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Due to the intrinsically inefficient service provisioning in traditional networks, Network Function Virtualization (NFV) keeps gaining attention from both industry and academia. By replacing the purpose-built, expensive, proprietary network equipment with software network functions consolidated on commodity hardware, NFV envisions a shift towards a more agile and open service provisioning paradigm. During the last few years, a large number of NFV platforms have been implemented in production environments that typically face critical challenges, including the development, deployment, and management of Virtual Network Functions (VNFs). Nonetheless, just like any complex system, such platforms commonly consist of abounding software and hardware components and usually incorporate disparate design choices based on distinct motivations or use cases. This broad collection of convoluted alternatives makes it extremely arduous for network operators to make proper choices. Although numerous efforts have been devoted to investigating different aspects of NFV, none of them specifically focused on NFV platforms or attempted to explore their design space. In this paper, we present a comprehensive survey on the NFV platform design. Our study solely targets existing NFV platform implementations. We begin with a top-down architectural view of the standard reference NFV platform and present our taxonomy of existing NFV platforms based on what features they provide in terms of a typical network function life cycle. Then we thoroughly explore the design space and elaborate on the implementation choices each platform opts for. We also envision future challenges for NFV platform design in the incoming 5G era. We believe that our study gives a detailed guideline for network operators or service providers to choose the most appropriate NFV platform based on their respective requirements. Our work also provides guidelines for implementing new NFV platforms.
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IEEE TRANSACTIONS ON NETWORK AND SERVICE MANAGEMENT 1
NFV Platforms: Taxonomy, Design Choices
and Future Challenges
Tianzhu Zhang, Han Qiu, Member, IEEE, Leonardo Linguaglossa, Member, IEEE,
Walter Cerroni, Senior Member, IEEE, Paolo Giaccone, Senior Member, IEEE
Abstract—Due to the intrinsically inefficient service provision-
ing in traditional networks, Network Function Virtualization
(NFV) keeps gaining attention from both industry and academia.
By replacing the purpose-built, expensive, proprietary network
equipment with software network functions consolidated on
commodity hardware, NFV envisions a shift towards a more
agile and open service provisioning paradigm. During the last few
years, a large number of NFV platforms have been implemented
to facilitate the development, deployment, and management of
Virtual Network Functions (VNFs). Nonetheless, just like any
complex system, such platforms commonly consist of abounding
software and hardware components and usually incorporate
disparate design choices based on distinct motivations or use
cases. This broad collection of convoluted alternatives makes it
extremely arduous for network operators to make proper choices.
Although numerous efforts have been devoted to investigating
different aspects of NFV, none of them specifically focused on
NFV platforms or attempted to explore their design space. In
this paper, we present a comprehensive survey on the NFV
platform design. Our study solely targets existing NFV platform
implementations. We begin with a top-down architectural view of
the standard reference NFV platform and present our taxonomy
of existing NFV platforms based on what features they provide in
terms of a typical network function life cycle. Then we thoroughly
explore the design space and elaborate on the implementation
choices each platform opts for. We also envision future challenges
for NFV platform design in the incoming 5G era. We believe that
our study gives a detailed guideline for network operators or
service providers to choose the most appropriate NFV platform
based on their respective requirements. Our work also provides
guidelines for implementing new NFV platforms.
KeywordsNetwork Function Virtualization, Service Function
Chaining, Service Management and Orchestration, NFV Infras-
tructure, VNF Life Cycle
I. INTRODUCTION
Traditionally, network services are provisioned using
purpose-built, proprietary hardware appliances (or middle-
T. Zhang was with the Department of Network and Computer Science,
Telecom Paris. He is now with Nokia Bell Labs, 91620 Nozay, France. (email:
tianzhu.zhang@nokia-bell-labs.com)
H. Qiu and L. Linguaglossa are with the Department of Network and Com-
puter Science, Telecom Paris, 91120 Paris, France. (email: han.qiu@telecom-
paris.fr, linguaglossa@telecom-paris.fr)
W. Cerroni is with the Department of Electrical, Electronic, and Information
Engineering “Guglielmo Marconi,” University of Bologna, 40136 Bologna,
Italy. (email: walter.cerroni@unibo.it)
P. Giaccone is with Consorzio Nazionale Interuniversitario per le Telecomu-
nicazioni (CNIT), 43124, Parma, Italy and with the Department of Electronics
and Telecommunications, Politecnico di Torino, 10138 Torino, Italy. (email:
paolo.giaccone@polito.it)
boxes). Middleboxes embody a large variety of specialized
functions to forward, classify, or transform traffic based on
packet content. Examples of middleboxes include L2 switch-
ing, L3 Routing, Network Address Translation (NAT), Fire-
wall (FW), Deep Packet Inspection (DPI), Intrusion Detection
System (IDS), Load Balancers (LB), WAN optimizers, and
stateful proxies. Nowadays, middleboxes are ubiquitous in
enterprise networks [1]. With the increasingly diversified user
requirements, as well as the rapid growth of Internet traffic in
terms of both volume and heterogeneity [2], hardware mid-
dleboxes begin to exhibit several fundamental disadvantages.
First off, middleboxes are generally expensive to acquire and it
usually requires domain-specific knowledge to manage them,
resulting in large capital expenditure (CapEx) and operational
expenditure (OpEx). Also, adding customized functionalities is
extremely time-consuming if not impossible, and it sometimes
takes an entire purchase cycle (e.g, four years) to bring in
equipment with new features [3]. Such tight coupling with
the hardware production cycle considerably hampers network
innovation and prolongs time-to-market. Deploying new Net-
work Services (NSs) is also a tedious process, as technicians
are required to visit specific sites and place the middleboxes in
a pre-defined order to form the correct Service Function Chains
(SFCs). Service instantiation might even take days. Worse still,
service maintenance usually involves constant repetition of the
same process. Furthermore, because of the inherent inflexibil-
ity, it is not trivial for hardware middleboxes to elastically
scale in and out based on the shifting demand or other system
dynamics. Consequently, network operators usually resort to
peak-load (over-)provisioning, which in turn leads to inefficient
resource utilization and high energy consumption.
To improve resource utilization and overcome the network
ossification, telecommunication operators began to pursue new
solutions that can guarantee both cost-effectiveness and flexi-
switch router
FW IDS
proxy NAT NIC
COTS hardware
COTS hardware
COTS hardware
Virtualization layer
NFV Manager
Fig. 1: Traditional vs. NFV paradigm
IEEE TRANSACTIONS ON NETWORK AND SERVICE MANAGEMENT 2
bility. The advent of Software Defined Networking (SDN) [4]
and Network Function Virtualization (NFV) [5] opened new al-
ternative approaches for network management and service pro-
visioning. SDN decouples the control plane from the data plane
and leverages a logically centralized controller to configure the
programmable switches based on a global view, while NFV
aims at replacing specialized middleboxes with software-based
Virtual Network Functions (VNFs) deployed on Commodity
Off-The-Shelf (COTS) hardware. The key to their success
lies in separating the evolution timeline of software network
functions from that of specialized hardware, completely un-
leashing the potential of the former. An illustrative example
contrasting the NFV paradigm with traditional network infras-
tructures is shown in Fig. 1. Compared to the traditional service
provisioning paradigm based on hardware middleboxes, NFV
manages to achieve cost-effectiveness by leveraging multiple
instances of VNFs on high-volume yet less expensive COTS
servers, routers, or storage. Service provisioning in NFV is thus
highly simplified, as the previously mentioned troublesome
tasks, such as middlebox deployment, monitoring, migration,
and scaling, can be optimally automated and flexibly managed
through software control mechanisms. It is thus convenient for
NFV solutions to exploit available resources and management
tools typical of cloud or edge computing infrastructures. In
addition, NFV remarkably promotes network innovation and
accelerates the time-to-market process as network function
development is cut down to writing software programs using
standard application programming interfaces (APIs).
Thanks to these benefits, NFV keeps gaining momentum
from both industry and academia. The first concerted effort
towards NFV standardization began in 2012, with the appoint-
ment of the Industry Specification Group on NFV as part of the
European Telecommunications Standards Institute (ETSI) [6].
Currently, ETSI consists of more than 500 members across the
world, including major telecommunication operators, service
providers, manufacturers, as well as universities. Meanwhile,
the continuous advancement of COTS hardware capabilities
and the emergence of high-speed packet processing techniques
have managed to reduce the previously huge performance
gap between software network functions and specialized mid-
dleboxes. Resources of other hardware components, such as
Graphics Processing Unit (GPU) and in-path programmable
network devices, can also be exploited to share the workload
and alleviate the CPU burden. These technical opportunities
considerably stimulate the growth of NFV and foster its
adoption by telecom operators. During the last eight years,
a large variety of NFV platforms have been developed and
implemented to spur the innovation and evolution of NFV.
However, just like any complex system, existing NFV
platforms usually encompass many closely interacting soft-
ware and hardware components and embrace divergent design
choices driven by their respective motivations, use cases, and
application fields. To deal with the non-trivial network function
life cycle, the design space of these platforms can be very wide,
with choices ranging from high-level VNF development to
low-level infrastructure details. The former category includes
VNF execution models, state management schemes, or genres
of APIs, while the latter category includes system design
choices like packet I/O frameworks, VNF interconnecting
methods, or virtualization technologies, as well as various
datapath acceleration techniques such as batch processing,
zero-copy packet transfer, data prefetching, and computation
offloading. Such a broad range of platform implementations
coupled with even more extensive design space makes it
extremely difficult (if not impossible) for network operators to
choose the most suitable solution to their needs. The tradeoffs
and caveats between different design choices are also unclear,
making new platforms laborious and error-prone to implement.
This paper presents a comprehensive survey of existing NFV
platforms and their design. The main contributions can be
summarized as follows:
We conduct a literature review and classify the existing
NFV platforms according to what features they provide
in terms of a typical VNF life cycle. We also briefly
review the internals of each platform.
We explore the NFV design space and discuss the
various design choices adopted by existing platforms.
We discuss potential challenges of bringing Artifi-
cial Intelligence (AI), network slicing, and Internet of
Things (IoT) into NFV.
Several existing literature surveys investigated some particular
aspects of NFV, including VNF placement [7], resource alloca-
tion [8], fault management [9], service function chaining [10],
and security [11], but none of them specifically focused on
the design aspects of NFV platforms from a VNF life cycle
perspective, nor did they attempt to explore the design space or
review different implementation choices. In [12], the authors
investigated several industrial NFV Management and Orches-
tration (MANO) projects, whereas our work additionally con-
siders the NFV management frameworks from academia. In
[13] and [14], a subset of the state-of-the-art NFV platforms
were generally reviewed, while our work considers, to the best
of our knowledge, all the existing platforms and focuses on
their tailored implementation.
This paper is organized as follows: in Sec. II, we give an
architectural overview of the components of NFV platforms.
Then we present our taxonomy on existing platforms in Sec. III
based on a typical VNF life cycle. In Sec. IV, we propose a
collection of critical design choices and survey the solutions
adopted by different platforms. We envision future directions
and draw our conclusion in Secs. V and VI, respectively.
II. NFV PL ATFO RM :AN ARCHITECTURAL OVERVIEW
We devote this section to presenting a general architectural
overview of a typical NFV platform and to reviewing the
key components in depth. Although a reference architecture
has been defined by the ETSI specification [15], most of the
existing NFV platforms did not strictly follow it. For example,
some key ETSI components were not implemented by some
industrial NFV platforms [12], whereas other implementations
focused only on partial management aspects. As a result,
we seek to combine the ETSI reference architecture with
those of the existing platforms and present a generic view,
as illustrated in Fig. 2. An NFV platform generally consists
of three primary components, namely the NFV MANO plane,
IEEE TRANSACTIONS ON NETWORK AND SERVICE MANAGEMENT 3
MANO plane
Service plane
NFV infrastructure
VIM
VNFM
NFVO
Placement
Scheduling
Monitoring
Data
Store
Scaling/Failover
COTS server
NIC SmartNIC
CPUs
NIC
Cores CPU
Main
memory
PCIe
Virtualization layer
vCPU vNIC vRAM Interconnect
Switch
Switch
Switch
caches
Fig. 2: The architecture of a general NFV platform
the service plane, and the NFV Infrastructure (NFVI). The
MANO plane provides centralized control over service pro-
visioning and management. The NFVI contains a collection
of computation, storage, and network resources that are dis-
tributed across different infrastructural nodes. MANO plane
components systematically monitor and schedule the resources
to build a virtualized environment and accommodate different
network services. The service plane contains a diversified
collection of VNFs that are ordered in the form of service
chains to fulfill the desired network services. These service
chains are also carefully monitored and adjusted by the MANO
plane components to efficiently multiplex the NFVI resources.
In general, the service plane is enabled through concerted
operations from both the MANO plane and NFVI.
A. MANO plane
The NFV MANO plane is the central point for service
provisioning in NFV. A MANO system typically consists
of three sub-systems: NFV Orchestrator (NFVO), Virtualized
Infrastructure Manager (VIM), and VNF Manager (VNFM).
As shown in Fig. 2, the NFVO is responsible for the instan-
tiation, management, and termination of network services. At
present, an NFVO commonly encompasses different modules
to apply different MANO operations. On the right part of
Fig 2, we illustrate four example modules. The placement
module is in charge of rendering the best deployment, pos-
sibly in an incremental fashion. When new services need
to be deployed, the placement module analyzes the service
descriptions or requirements specified by network operators,
constructs an aggregated service representation (e.g., service
processing graph), performs necessary optimizations (e.g.,
function merging, redundant elimination), and calculates the
best possible placement strategy by determining the nodes on
which to deploy the related VNFs and their chaining order. The
monitoring module is responsible for collecting statistics and
events from both the service plane and the infrastructure and
provides runtime feedback to other NFVO modules. Based on
the traffic condition and resource utilization collected on-the-
fly, the placement module can recalculate a new placement
to achieve better performance. The scheduling module can
dynamically make fine-grained resource allocation to attain
resource efficiency. The scaling/failover module can also col-
laborate with the placement module to scale in/out particular
VNFs or service chains to accommodate traffic fluctuations
or instantiate new VNF replicas upon failure. Based on the
decisions made by the aforementioned modules, the NFVO
interacts with other MANO plane components to realize the
intended service configurations and resource allocations.
The VIM is designed to configure infrastructure compo-
nents to accommodate the heterogeneous VNFs or service
chains instantiated in the service plane. In specific, it directs
the provision/release/upgrade of NFVI resources and man-
ages the mapping between virtual and physical resources. It
also manages the data path for network services by creat-
ing/deleting/updating virtual interfaces and logical links and
collects the NFVI software and hardware resource status on
behalf of the NFVO monitoring module. Note that a VIM
instance might control either all the resources of the whole
NFVI or those of multiple NFVI-Nodes. In some cases, a VIM
might also just control a specific type of resource.
On the other hand, VNFM interacts with the service plane
and takes care of the lifecycle (i.e., instantiating, scaling,
upgrading, and terminating) of individual VNFs and service
chains. It also needs to synchronize with VIMs to allocate
or release the related infrastructural resources. According to
ETSI specification, the MANO system might also maintain
several data stores to hold configuration information such as
network service descriptors, VNF templates, NFVI resource
repositories, etc.
B. NFV Infrastructure
The NFV Infrastructure (NFVI) contains all the essential
hardware and software components to compose virtual net-
work services. The infrastructure might belong to Internet
service providers, cloud/edge operators, or simply infrastruc-
ture providers. It usually embodies a large variety of comput-
ing nodes and network equipment. Each computing node or
network equipment is commonly referred to as NFVI-Node.
Network equipment in NFVI can be traditional purpose-built
switches/routers or the emerging programmable switches that
IEEE TRANSACTIONS ON NETWORK AND SERVICE MANAGEMENT 4
can be remotely orchestrated with SDN or P4 [16] seman-
tics. The most typical form of computing nodes in NFVI is
represented by COTS servers. These servers normally con-
tain several critical hardware components, including multicore
CPUs, the main memory, and the physical Network Interface
Controllers (NICs), which are interconnected through PCI
buses. The physical NICs are capable of operating at Gigabit
rates with multiple queues promoting parallelization. High-
speed packet I/O techniques are also integrated by the NICs to
transport packets to the service plane. Inside the server, multi-
core CPUs are distributed across non-uniform memory access
(NUMA) nodes to speed up traffic processing. Aside from
CPU, other computing units such as smartNICs and GPUs
are also widely utilized by existing NFV platforms to further
boost performance. The virtualization layer in the COTS server
provides the environment to accommodate network functions.
The virtualization can be at the hardware level relying on bare-
metal hypervisors or at the OS level using container engines.
Some platforms even execute network functions as ordinary
processes, which are addressed as Physical Network Functions
(PNFs) in some works. In this paper, we universally refer to
them as VNFs for the sake of simplicity. To ensure efficient
communication between the VNFs and the external network,
virtual interconnects need to be precisely established. This
is typically accomplished using state-of-the-art software-based
virtual switches or customized forwarding tables. Note that we
consider physical links between COTS servers and network
equipment as part of the NFVI as well.
C. Service plane
The service plane is populated with a variety of VNFs im-
plementing different processings to constitute various network
services. The distribution of VNFs inside virtual environments
is quite flexible. For instance, a VNF or a whole service chain
can be mapped to a single VM for execution, but a VNF
can also be split into finer-grained processing elements and
deployed across multiple NFVI-Nodes. In addition, VNFs are
usually constructed using different programming abstractions
and operate in different runtime execution models. Some
platforms provide complete primitives to build and manage
stateful VNFs or SFCs.
III. TAXONOMY OF NFV PLATFORMS
Our taxonomy of NFV platforms follows the typical life
cycle of network functions, as shown in Fig. 3. The initial
step is prototyping, which implements the first instances of
the desired network functions. Then it follows the extensive
testing phase to validate the correctness and performance of
the implemented functions. Afterward, during the deployment
phase, the network functions are instantiated for execution
in the production environment. Finally, the management and
execution phase ensures smooth service provisioning by taking
care of different management issues and execution optimiza-
tions at runtime. Based on our literature review, most of the
existing NFV platforms are specially purposed to facilitate
a particular phase in the life cycle. Therefore, we opted to
classify existing NFV platforms according to their main focus
for the VNF life cycle. Note that the integrated NFV platforms
aim at actualizing end-to-end service provisioning and thus
take care of multiple phases in the life cycle, we discuss them
in detail at the end of this section.
The remainder of this section is organized as follows.
Sec. III-A focuses on the design and implementation of
network functions. In Sec. III-B, we discuss NFV platforms
purposed to validate and benchmark the implemented net-
work functions. We devote Sec. III-C to discussing NFV
platforms that specifically target the problem of deployment. In
Sec. III-D, we review platforms dealing with the management
and execution of VNFs and SFCs. Finally, we discuss the
integrated NFV platforms in Sec. III-E.
A. Prototyping
Rapid prototyping massively reduces the time-to-market of
network services and plays a critical role in the growing
popularity of NFV. Existing NFV platforms usually undertake
two approaches to spur VNF development. The first approach
is embracing modular design by pre-building a set of simple,
loosely-coupled, and extensible network functions for devel-
opers to implement more advanced network services without
reinventing the wheel. The second approach is employing
complexity abstraction to deal with the intricacies of the VNF
execution environment and let the developers concentrate on
implementing the essential VNF processing logics.
Modular design: Several existing NFV platforms specif-
ically follow the modular design approach. In particular,
xOMB [17] is among the earliest endeavors for building
scalable, programmable, and performant network functions on
COTS servers. It provides a set of programmable modules and
allows them to be arranged into a general pipeline to imple-
ment the expected network services. NetBricks [18] facilitates
the VNF development process by implementing a small set
of core processing elements that are highly optimized and
customizable through user-defined functions. It also employs
safe language, an efficient runtime library, and unique types
to ensure the execution and performance isolation of the im-
plemented VNFs. µNF [19] builds SFCs using disaggregated,
reusable components, and employs a centralized orchestrator
to convert service policies to equivalent forwarding graphs. It
further instructs per-server agents to install and manage the
VNFs. Some platforms even provide modular transport stack
to develop network functions at the application layer. For ex-
ample, Microboxes [20] implements a modular, customizable,
asynchronous TCP stack for each flow to avoid redundant
SFC processing. It also provides a publish/subscribe channel to
chain network functions and realize complex network services.
ClickNF [21] augments the Click router [22] with a modular
TCP stack to build L2-L7 VNFs and devises a blocking socket
to ease VNF development difficulty imposed by traditional
asynchronous non-blocking paradigm.
Complexity abstraction: Existing NFV platforms commonly
provide high-level abstractions of the underlying function ex-
ecution environment to relieve developers from the peripheral
IEEE TRANSACTIONS ON NETWORK AND SERVICE MANAGEMENT 5
Prototyping Deployment
Fig. 3: Our taxonomy is inspired by the typical life cycle of network functions, namely: prototyping, testing, deployment,
management and execution. We highlight in boxes some of the principles and objectives, and their main positioning within the
network function life cycle.
but tedious tasks such as packet I/O, traffic classification,
state management, task coordination, and resource alloca-
tion. In particular, NFMorph [23] decouples VNF logics
from packet processing optimizations and proposes a domain-
specific language with coherent processing pipelines. It also
optimizes VNF execution based on the runtime workload and
system constraints. Polycube [24] builds reconfigurable SFCs
in kernel space. It separates the processing pipeline into a fast
kernel path and a slow path and exposes an API to handle
fast-/slow-path processing and system events. The fast path
leverages extended Berkeley Packet Filter (eBPF) [25] to sus-
tain high speed, while the slow path provides more advanced,
complex processing in user-space. Some platforms aim at
providing APIs to realize customized processing for individual
traffic classes. For instance, FlowOS [26] exposes an API for
VNF developers to implement customized processing for each
packet flow without dealing with the low-level complexities
such as inter-process communication and raw packet I/O.
Scylla [27] is a declarative language for per-flow custom
processing in wireless networks. It also provides a set of pro-
gramming abstractions to express management intents, which
are realized in NFVI by Scylla runtime. MiddleClick [28] aims
at building high-speed, parallelized service chains. It provides
APIs for network operators to define SFC intents which are
synthesized into a flow table. A session abstraction is also
implemented to facilitate per-flow inspection.
Some platforms provide APIs to automatically manage VNF
execution states. For instance, libVNF [29] implements a
generic library to assist the development of VNFs ranging from
L2/L3 middleboxes to transport-/application-layer endpoints,
with the support of seamless integration of the kernel and third-
party network stacks. A request object abstraction is proposed
to maintain application states across multiple non-blocking,
event-driven callbacks. The libVNF API is also capable of
interacting with multi-level data stores for state management
across threads of a single VNF or multiple VNF replicas.
StatelessNF [30] embraces the separation of concerns design
by decoupling the VNF states from processing so that devel-
opers only need to concentrate on VNF-specific logic, while
StatelessNF arranges for state replication and management
tasks. The VNF states are maintained in a distributed key-
value data store that guarantees low-latency access and data
resilience. S6 [31] extends distributed state objects (DSO) with
a programming model to build scalable VNFs. S6 runtime
manages shared VNF states distributed in DSO space. S6
also employs several optimizations including micro-threaded
scheduling and DSO space reorganization. NFVactor [32] em-
ploys the distributed actor model to support per-flow abstrac-
tion and provides APIs to implement VNFs with resilience.
NetStar [33] implements a flow-based asynchronous interface
combined with a future/promise library for VNF development.
Instead of spreading control logic across multiple callback
functions, NetStar mimics sequential execution by chaining
multiple future objects and functions over a single call.
B. Testing
After the prototyping phase, an extensive testing campaign
is required to validate the correctness and performance of the
newly developed VNFs. In this section, we review existing
NFV platforms specially designed for execution validation as
well as performance benchmarking.
Validation: A few NFV platforms adopt code analysis to
validate the correctness of VNFs and SFCs. For example,
SFC-Checker [34] is a diagnosis framework to verify the
correctness of SFC forwarding behaviors. It extends OpenFlow
to represent each VNF with a Match/Action table and a state
machine and builds a stateful forwarding graph to capture
both forwarding behaviors and state transitions so that SFC
forwarding behaviors can be verified under different traffic
conditions. BUZZ [35] is a testing framework that models
complex network functions as finite-state machines to detect
policy violations. It also employs an optimized symbolic
execution to achieve high scalability. ChainGuard [36] is an
independent tool for static SFC verification in the dynamic
cloud environment. It leverages flow tables to model the pro-
cessing and forwarding behaviors for the SFCs and implements
IEEE TRANSACTIONS ON NETWORK AND SERVICE MANAGEMENT 6
a graph traversing algorithm for verification. NFactor [37]
automatically synthesizes a VNF model through code analysis
to verify network policy and service chaining.
Performance benchmarking: There is a broad range of
platforms designed to benchmark the performance of the newly
developed VNFs and SFCs. Some of them mainly focus on
performance monitoring in different environments. For in-
stance, ConMon [38] is a distributed framework to monitor the
performance of containerized VNFs. It dynamically discovers
and monitors the communication between containers, and
executes network monitoring functions inside a standby con-
tainer interconnected through a virtual switch. KOMon [39]
is a kernel-based online monitoring tool to measure packet
processing times imposed by the target VNF. NFVPerf [40]
detects performance bottlenecks for a SFC by monitoring inter-
VNF communication. VBaaS [41] envisions a Benchmark-as-
a-Service platform to perform runtime performance profiling
on VNFs and NFVI. OPNFV Barometer [42] is designed to
monitor the performance of DPDK-accelerated VNFs. It can
be attached to the target VNF as a secondary process to gather
data plane information. NFV-VIPP [43] can be integrated into
the DPDK-accelerated data plane to collect execution metrics
and demonstrate the internals of an NFVI node.
Besides performance monitoring, some platforms are also
capable of performance analysis. NFV-vital [44] interprets
deployment and workload configurations to setup VNFs and
generate workload. It also receives runtime statistics for
posttest analysis. Gym [45] is designed for automatic VNF
performance benchmarking. It embraces a modular architecture
with an extensible set of benchmarking tools and a simple
messaging subsystem for remote procedure calls. It further
provides a means for data post-processing and result visualiza-
tion. Du et al. [46] build a benchmarking framework on the
OPNFV clearwater platform. They leverage the microservices
architecture to integrate existing open-source tools to realize
comprehensive tests under varied traffic loads and fault con-
ditions. Symperf [47] predicts VNF runtime performance and
functional behaviors under various traffic dynamics through
code analysis. Perfsight [48] aggregates runtime information
from data path to diagnose performance issues. SFCPerf [49]
uses a control module to parse service descriptions and deploy
the corresponding SFCs in NFVI. The control module also
collects critical statistics for data analysis and visualization.
In [50], the authors proposed NFV-Bench, a benchmarking
solution capable of performing dependability and performance
evaluations for NFV solutions, and presented a case study on
two state-of-the-art virtualization techniques. BOLT [51] de-
fines the concept of the performance contract, which expresses
the expected VNF or SFC performance as a function of critical
parameters (e.g., execution instructions, CPU cycles, memory
accesses). DeepDiag [52] monitors the runtime queuing statis-
tics for each VNF and constructs an online impact graph to
diagnose the cause of performance degradation. CASTAN [53]
adopts symbolic execution to identify the worst code path and
a CPU cache model to determine memory access patterns that
cause cache invalidation. Currently, CASTAN has successfully
analyzed a dozen DPDK-based network functions. In [54], the
authors proposed a Proof-of-Concept (PoC) implementation of
a semi-supervised learning algorithm to monitor and detect
malfunctioning VNFs. The authors planned to optimize the
algorithm and extend their approach to more complex envi-
ronments and malfunctions for further validation.
C. Deployment
The deployment phase requires careful planning of service
composition to realize the intended SFCs.
Service composition: Many NFV platforms provide cus-
tomized services for different traffic classes by parsing the
specified service intents, organizing VNFs into logical exe-
cution graphs, and configuring the correct traffic routes to
steer packets through the corresponding service chains. These
platforms commonly employ different mechanisms to reduce
the processing redundancy and optimize service deployment.
For instance, Slick [55] allows developers to specify network
services based on traffic classes. Then a Slick “runtime” com-
ponent parses the service specifications and makes placement
decisions using several heuristics before placing the VNFs and
configuring the forwarding routes. SpeedyBox [56] utilizes a
match/action table to consolidate VNF actions at runtime and
eliminate redundant processing for SFCs. NFCompass [57]
adopts a two-level SFC reorganization technique to parallelize
VNFs and eliminate redundant processing. It also adopts a
task allocation scheme to balance the load and minimize
latency. ParaBox [58] utilizes a dependency analysis module
to identify parallelizable VNFs and implements mirror/merge
functions to distribute and aggregate packet copies across the
parallelization stages. NFP [59] incorporates an orchestrator to
analyze VNF dependencies and build optimized service graphs.
The NFP infrastructure handles graph execution while dealing
with traffic steering, load balancing, and parallel execution.
Metron [60] decomposes SFC processing graph into stateless
and stateful operations. The former is offloaded to in-path pro-
grammable switches, while the latter remains on COTS servers.
Metron also leverages the in-path tagging to dispatch packets
to the correct processing cores. An agent is also deployed on
each server to conduct MANO operations. Flurries [61] is a
container-based NFV platform with flexible service chaining
and flow-level service customization. A combination of polling
and interrupt I/O scheme is also adopted to consolidate per-
flow service chains. SNF [62] uses graph composition and
set theory for traffic classification, and synthesizes VNFs
for each traffic class using a minimal number of elements.
vConductor [63] automates service deployment with a re-
source scheduling algorithm to meet business requirements,
and uses enhanced inventory management for fault isolation.
CoMb [64] advocates consolidated development of network
functions at execution and management level. It parses service
policies and infrastructure descriptions and solves an optimiza-
tion model to decide the optimal deployment strategy, which is
mapped to the distributed data plane by allocating the required
resources. VirtPhy [65] integrates server-centric topology,
SDN techniques, and software switches to realize efficient
VNF deployment and service function chaining for edge data
centers. VLH [66] combines NFV and edge computing to
IEEE TRANSACTIONS ON NETWORK AND SERVICE MANAGEMENT 7
handle the complex IoT application call-graphs with improved
resource efficiency. It also adopts container techniques and
the microservices architecture for remote function sharing.
NetFATE [67] implements a PoC architecture to advocate
deploying SFCs on the edge. fNF [68] proposes the concept
of flyweight network functions that construct slices on the
shared IoT infrastructure for applications with diversified QoS
requirements. CoNFV [69] combines cloud and end-hosts to
reduce SFC deployment cost and processing latency.
D. Management and execution
The final phase of the VNF life cycle involves both man-
agement and execution of the deployed network services.
Some NFV management platforms aim at building full-fledged,
holistic MANO systems, while others tackle only a subset of
the MANO problems, such as resource scheduling and VNF
scaling/migration. We also review platforms that attend to the
optimized execution and secure runtime of VNFs and SFCs.
Holistic MANO: Some platforms are purposed for full-
fledged, holistic MANO systems. In particular, ETSO [70] is
an ETSI-compliant NFV MANO platform for heterogeneous
cloud environments. It addresses various key service orchestra-
tion issues through a shared service abstraction. UNIFY [71],
[72] employs a layered graph abstraction to automatically map
user-specified services into SFCs deployed to the underlying
NFVI PoPs. It also models network and service altogether
and provides joint optimizations for service management and
orchestration. Open Source MANO (OSM) [73] aims at
implementing a production-grade MANO stack interoperable
with third-party NFV components while it allows for efficient
service provisioning. OpenMANO [74] consists of an orches-
trator (openmano), a VIM (openvim), and a graphical user
interface. Openvim manages NFVI resources and relies on
a REST API to communicate with OpenMANO for MANO
operations. Open Baton [75] is an extensible MANO frame-
work for service orchestration across heterogeneous NFVIs. It
manages a diverse set of VNFs running across NFVI-Nodes
with different virtualization technologies and features network
slicing for resource multiplexing. T-NOVA [76] leverages
SDN and cloud management tools to design and implement a
software NFV MANO stack for automated VNF management.
TeNOR [77] is an NFV orchestrator based on a micro-
services architecture. It proposes two approaches to address
resource and service mapping and provides a marketplace to
accommodate third-party VNFs.
Resource scheduling: A large set of NFV platforms specif-
ically tackle the problem of runtime resource scheduling.
NFVnice [78] adopts rate-cost proportional fairness by adjust-
ing CPU weight for each VNF based on the estimated traffic
arrival rate and service time. The scheduling is done by tuning
the OS scheduler via Linux cgroups. At runtime, NFVnice
monitors workload and employs a back-pressure mechanism
to early-drop packets for congested SFCs to spare resources.
EdgeMiner [79] spares CPU resources from co-located VNFs
to execute other applications at the network edge, by employ-
ing a back-pressure scheme to detect SFC overloads and puts
upstream VNFs into sleep to harvest the otherwise wasted
CPU cycles. UNiS[80] is tailored to schedule poll-mode
VNFs. For each worker core, it measures intermediate buffer
occupancies to make scheduling decisions. The scheduling
is non-intrusive as UNiS just tunes parameters of the Linux
Realtime Scheduling without rewriting the VNFs. SNF1[81]
dynamically traces the VNF workload and allocates compute
resources at a fine granularity. A peer-to-peer in-memory store
is deployed to proactively replicate the states and reduce packet
processing latency. ResQ [82] is a cluster-based resource man-
agement framework with guaranteed service layer objectives. It
consists of a performance profiler and a scheduler. The profiler
performs a set of experiments on the target VNFs to construct
profiles. Based on the profiling results, the ResQ scheduler
computes a resource-efficient allocation using a greedy ap-
proach. ResQ also periodically solves a Mix Integer Linear
Programming (MILP) formulation to obtain the optimal alloca-
tion, which can be applied to substitute the current allocation if
a pre-defined threshold is exceeded. NetContainer [83] aims at
exploiting cache locality to achieve maximum throughput and
low latency for containerized VNFs. The authors first identify
the random page allocation policy as the root cause of cache
pollution. Then they build an estimation model based on the
footprint theory to infer the cache access overhead and model
the cache mapping problem as a Minimum Cost/Maximum
Flow (MCMF) problem to decide the optimal memory buffer
mappings. NFV-throttle [84] spreads modules across NFVI
to dynamically monitor system conditions and drop excessive
packets to prevent VNFs from being overwhelmed. Iron [85]
introduces an enforcement mechanism to account for the time
spent by the VNFs in kernel space, and throttles or even drops
packets for the aggressive VNFs through Linux scheduler or a
hardware-based approach. ESFC [86] is designed for flexible
SFC resource scheduling. It implements a controller to monitor
the VNF and enforce resource allocation policies using an
asynchronous notification mechanism. A hash algorithm is
devised to balance packets across VNF replicas while ensuring
flow-level affinity. SCC [87] collects execution statistics to
identify the root causes of SFC delays, which are addressed by
SCC runtime by adjusting the allocated batch size, scheduling
policies, priorities, and time slices.
Scaling and migration: Some platforms strive for efficient
VNF scaling and migration. Split/Merge [88] uses a central-
ized orchestrator and SDN controller to direct instance scaling
and flow migration. It provides an API to split or merge flow
states among VNF replicas. The system then migrates the
relevant states and configures the network to direct flows to the
correct replicas. TFM [89] performs migration through a cen-
tralized controller, which decouples flow and state migration
processes with three modules: a state manager, a flow manager,
and a forwarding manager. The state manager conducts state
migration through southbound APIs. The forwarding manager
interacts with the SDN controller to update the corresponding
traffic steering rules. The flow manager distributes TFM boxes
for packet classification and buffering during VNF migration.
1The SNF cited here is different from the one previously mentioned [62].
IEEE TRANSACTIONS ON NETWORK AND SERVICE MANAGEMENT 8
OpenNF [90] implements a controller that consists of an
event-driven model to capture relevant packets, a southbound
API to request the import/export of VNF states at different
granularities, and a northbound API to control applications and
instruct state migration, which is carefully crafted to avoid
packet losses or out-of-order packets. It also performs state
synchronization with strong or eventual consistency. DiST [91]
and U-HAUL [92] follow similar procedures for state and
flow migration without controller intervention. In particular, U-
HAUL only identifies and migrates states for elephant flows
while serving mice flows in original VNFs until expiration,
reducing the number of migrated states. SliM [93] proposes
statelet, a compact packet data representation, to achieve
bandwidth-efficient state migration. It also integrates a kernel-
bypassing I/O technique to boost performance. StateAlyzr [94]
is a non-intrusive framework that handles state clone and
migration based on program analysis. LEGO [95] provides
a set of mechanisms for traffic splitting, instance partitioning,
and runtime management, to enable elastic scaling of Artifi-
cial Neural Network (ANN)-based VNFs. Lange et al. [96]
employs a machine learning approach to predict and scale the
number of VNF instances based on recently monitored traffic.
The authors also provided guidelines on the data features
and parameters to render reliable predictions. DeepMigra-
tion [97] deduces the migration and scaling cost of existing
VNF instances using a customized graph neural network, and
dynamically decides the best flow migration policies through a
trained reinforcement learning model. CHC [98] adopts a set
of state management and optimization techniques to ensure
service correctness without degrading performance. In partic-
ular, it offloads VNF states to the distributed data store and
employs state caching and update algorithms to ensure high
performance. It additionally leverages metadata to guarantee
a set of correctness properties during traffic redistribution and
instance/component failures.
Optimized execution: There are many platforms devoted to
optimizing the underlying NFVI to accelerate the execution of
VNFs and SFCs. The optimization can be performed directly
within individual NFVI nodes (e.g. COTS servers), or by
leveraging a hardware-assisted approach that delegates some
portion of the VNFs’ computational resources to external
accelerators. Within the first class, NetVM [99] achieves line-
rate processing through a shared memory mechanism and relies
on a hypervisor switch to steer packets based on traffic or
system conditions. It also defines multiple trust domains to
limit memory access of untrusted VNFs. OpenNetVM [100]
follows NetVM design, but adopts containers to wrap VNFs.
It achieves more flexible traffic steering by enabling VNFs and
management entities to make routing decisions. ClickOS [3]
utilizes the Click Modular Router [22] to build a wide range of
VNFs in Xen-based uni-kernel VMs. A set of optimizations
is performed on the hypervisor data path to boost the per-
formance. Similarly, HyperNF [101] advocates consolidating
VNFs for resource efficiency and reduces synchronization
overhead with hypervisor-based packet I/O. CliMBOS [102]
implements lightweight, isolated, and modular IoT backends
based on ClickNF. MVMP [103] employs a virtual device
abstraction to flexibly steer traffic between containerized VNFs
and physical NICs. NFF-Go [104] is designed to build and
deploy network functions in the cloud. It leverages Go lan-
guage for concurrency and safety, and a scheduler to scale
VNFs on demand. IOVTee [105] optimizes the VNF RX path
by mapping the VM queues to hypervisor switch, eliminat-
ing the expensive copy operations while ensuring security.
HALO [106] optimizes the flow classification process by ex-
ploiting hardware parallelism of the CPU caches and extending
the CPU instruction set to scale flow-rule lookups. NNF [107]
extends UNIFY’s data plane to execute VNFs at end devices
and a native controller to instantiate service graphs according
to the corresponding VNF templates and employs network
namespaces to guarantee isolation and multi-tenancy.
Some platforms adopt the hardware-assisted NFVI optimiza-
tion. In particular, P4SC [108] and P4NFV [109], both explor-
ing P4 language to accelerate SFC processing. P4SC parses
specified service policies and converts them into a P4 pro-
gram, which is subsequently deployed onto the P4-compatible
hardware. P4NFV is designed for both hardware and software
targets and supports runtime reconfiguration without violating
state consistency. Albeit augmented with various software
acceleration techniques, CPU cores might still fall short of per-
formance. As a result, several platforms explore other hardware
components for processing acceleration. OpenANFV [110]
aims at supporting VNF acceleration in the cloud by dele-
gating a subset of tasks to PCIe-based FPGA card. Similarly,
the work in [111] proposes to integrate OpenNetVM with
SmartNICs to offload VNF processing and enforce memory
isolation. ClickNP [112] augments COTS servers with FPGA
acceleration and exposes a modular abstraction to implement
VNFs. UNO [113] targets the SmartNICs (i.e. ASIC, FPGA,
System on Chip) for computation offloading without violating
the interoperability with the existing orchestration plane. While
still relying on a centralized orchestrator to make global
decisions, UNO selectively places new VNFs on the underlying
SmartNICs to minimize host CPU usage, based on a placement
algorithm considering local system status. It also actively
reruns the algorithm and adjusts VNF placement between
host and SmartNICs. To hide the complexity of SmartNICs
from the remote orchestrator, UNO exposes a single- switch
abstraction that correctly maps traffic steering rules to the host
or SmartNIC switches. NICA [114] exploits F-NICs to accel-
erate inline processing. It implements an API to grant direct
control over F-NIC accelerators and an I/O path virtualization
for multiple VMs to share F-NICs with security and fairness.
Some platforms construct CPU-GPU pipelines to expedite SFC
processing. NetML [115] accelerates data transfer to GPU
by optimizing the data path. FlowShader [116] leverages
kernel stack for traffic classification and exposes an API to
develop compatible VNFs across CPU and GPU domains. It
also employs a scheduling algorithm to balance the workload
between GPU and CPU. GPUNFV [117] employs flow-level
parallelism and runs an SFC to completion in a GPU thread.
It exploits GPU for processing and devotes CPU for packet
I/O and flow classification. Gen [118] features the dynamic
scheduling of GPU threads for VNF scaling, and supports
runtime SFC modification using CUDA API. Grus [119]
IEEE TRANSACTIONS ON NETWORK AND SERVICE MANAGEMENT 9
reduces the processing latency through coordinated access of
the PCI-E bus, fine-grained VNF scheduling, and dynamic
batching. G-NET [120] manipulates GPU context to allow
for spatial GPU sharing across manifold VNF kernels and
leverages safe pointers to guarantee GPU memory isolation.
A scheduling algorithm is also employed to calculate the per-
SFC cost and optimize the GPU resource sharing.
Secure runtime: Another group of platforms has been
specifically devoted to developing secure VNFs for execution
in untrusted environments. vEPC-sec [121] incorporates a vari-
ety of traffic encryption, validation, and monitoring schemes to
safeguard cloud-based LTE VNFs. SplitBox [122] distributes
VNF functionalities to multiple cloud VMs to obscure its
internals from public cloud. Embark [123] allows VNFs to
operate on encrypted data leveraging a special HTTPS en-
cryption scheme. BSec-NFVO [124] introduces a blockchain-
based architecture to protect NFV orchestration by auditing all
the operations over the SFCs. Other platforms exploit Intel R
Software Guard Extensions (SGX) [125] instruction codes
to secure VNFs from memory reading attacks. In specific,
S-NFV [126] concentrates on the protection of VNF states
by stashing them into the shielded SGX memory region
(enclave) to prevent unauthorized access or snooping. Trust-
edClick [127] and ShieldBox [128] extend the Click modular
router to secure packet processing within SGX enclave, and
rely on SGX remote attestation to verify code correctness.
ShieldBox additionally integrates DPDK for high-speed packet
processing and ring buffers to support SFC deployment. Sev-
eral platforms further protect VNF states. SafeLib [129] offers
comprehensive protection, including user traffic, VNF code,
policy, and execution states. It also integrates DPDK and
libVNF to support TCP functionalities without compromising
performance. LightBox [130] employs a virtual interface to
protect enclave I/O, a state management scheme to cache states
for active flows, and a space-efficient algorithm for flow clas-
sification. Safebricks [131] partitions VNF code to minimize
the trusted computing base in enclaves and performs packet
exchanges across trust boundaries through shared memory. It
also supports deploying an entire SFC inside an enclave and
leverages Rust primitives to isolate the VNFs.
E. Integrated NFV platforms
Besides the foregoing NFV platforms that can be categorized
into a specific phase of the typical VNF life cycle, there is
a large collection of integrated NFV platforms that involve
multiple phases for end-to-end service provisioning.
Several industrial projects strive for building integrated NFV
platforms. For instance, CloudBand [132] is a carrier-grade
NFV platform from Nokia. It consists of two components: the
CloudBand Management System and the CloudBand Node.
The former functions as the NFVO that interfaces with the
latter through standard OpenStack APIs. CloudBand node
integrates the OpenStack Platform as VIM and other Red Hat
virtualization solutions to construct NFVI. CloudBand also
implements different abstractions that support network services
optimized for distributed cloud infrastructure and VNF lifecy-
cle management. CloudNFV [133] is an open-source NFV
platform based on cloud computing and SDN. It employs a
data model named “active virtualization” to represent network
services and infrastructural resources. Based on the current re-
source usage and specific service profiles, CloudNFV’s MANO
plane deploys VNFs to the most suitable NFVI PoPs and
configures the corresponding routes. The MANO plane also
inspects resources and traffic conditions in real-time to make
orchestration decisions according to pre-defined management
policies. SONATA [134] implements a service development
toolchain for service composition and integrates a service plat-
form and a modular orchestration system to deploy and man-
age network services. OPNFV [135] is a Linux Foundation
project which integrates several open-source sub-components
for the development of NFV systems. It can provide a large
variety of tasks including continuous components integration,
function verification, performance benchmarking, and service
automation, as well as cycle management, dynamic service
provisioning, fault recovery, and vendor-agnostic deployment.
ONAP [136] is a cloud-native NFV platform that provides a
whole set of solutions to compose, deploy, and manage the
complete life cycle of network services across the NFVI.
There are also many integrated NFV platform implemen-
tations from academia. For instance, Eden [137] is purposed
for provisioning network functions at end-hosts in a single
administrative domain. It is composed of a controller, stages,
and enclaves at the end-hosts. The controller provides cen-
tralized VNF coordination based on its global network view.
Stages reside in the end-host stack to associate application
semantics to particular traffic classes. The per-host Eden
enclave maintains a set of Match/Action tables to decide the
destination VNF for each packet based on its traffic class. In
Eden, VNFs are written in F# language and are automatically
compiled into executable byte-code to be interpreted inside
the enclaves. OpenBox [138] allows developers to implement
VNF logic through the northbound API of the OpenBox
controller, which in turn deploys the logic to the data plane
and implements the intended processing sequence through the
OpenBox protocol. The OpenBox controller merges the core
control logic of multiple VNFs to avoid duplicated processing
and spare NFVI resources for other tasks. The OpenBox data
plane is extensible with specialized hardware or pure software.
Cloud4NFV [139] is an ETSI-compliant platform. It provides
an SFC model for fine-grained traffic classification and steering
and relies on cloud management tools for service orchestration.
MicroNF [140] builds modularized SFCs based on element
dependency analysis and places them with minimal inter-VM
data transfer. It also employs two algorithms to achieve load-
balanced scaling and introduces an infrastructure to realize
high-speed forwarding and fair scheduling. Flick [141] brings
application-specific semantics into VNF development on multi-
core COTS servers. The authors implement a domain-specific
language to offer high-level abstractions and common primi-
tives to assist VNF development. The compiler automatically
translates the flick programs into parallel task graphs with
bounded runtime resource usage. Multiple graphs can exe-
cute simultaneously without interference through cooperative
scheduling. E2 [142] exposes a “pipelet” abstraction to express
network policies, each of which consists of a subset of input
IEEE TRANSACTIONS ON NETWORK AND SERVICE MANAGEMENT 10
traffic (or traffic class) and a processing graph. E2 manager
merges multiple pipelets into a graph and instructs local agents
to place VNFs across servers and interconnect them through
a high-speed data plane. E2 also provides hooks to VNFs
and data plane to make dynamic adjustments. SDNFV [143]
combines SDN and NFV to realize a flexible, hierarchical
control framework over VNFs. It consists of three hierarchies:
SDNFV application, SDN controller, NFV orchestrator, and
NF manager. SDNFV application utilizes a graph abstraction
to represent the intended network services for different traffic
flows. Then it proposes a heuristic algorithm to jointly deploy
the VNFs to COTS servers and configure traffic routes across
them, through the SDN controller and NFV orchestrator. An in-
stance of NF manager is installed on each COTS server to man-
age the local VNFs and traffic routing. Each manager maintains
an extended OpenFlow (OF) table based on host-level status.
This table can also be configured by the remote SDN controller
(for default routing) and the local VNFs (based on their
internal states), realizing a more flexible control paradigm
beyond SDN. GNF [144] exposes an interface to specify
services at the network edge and relies on a manager for
MANO operations. The manager instructs per-device agents
to deploy and manage VNFs in containers. DeepNFV [145]
is based on GNF. It incorporates deep learning techniques
to learn hidden data patterns and provide enhanced services
such as traffic classification, QoS optimization, and link status
analysis. Additionally, the NFV platform can provide the tools
to automatically detect redundant code and parallelize the jobs
that could be performed in parallel.
IV. DESIGN SPACE
We now explore the design space and summarize the dif-
ferent design choices adopted by existing NFV platforms.
This section focuses on the technological solution adopted by
each platform, and it is complementary to Sec. III, whose
taxonomy refers to the platform life cycle of VNFs. We
begin our discussion from the MANO plane followed by the
service plane and NFVI. The design choices of some existing
representative NFV platforms are listed in Table I. For a more
detailed description of the NFV design space, please refer to
our technical report [146]. Note that in general there is no
superior choice over the others, and a choice should be made
according to specific use scenarios and application contexts.
A. MANO plane
High-level API: Most of the existing NFV frameworks
provide high-level APIs to specify service policies or smooth
the process of VNF development. These APIs can be either
Domain-Specific Language (DSL) or General-Purpose Lan-
guage (GPL). GPLs such as C, C++, Java, and Python are
mature programming languages capable of solving problems
in multiple domains. They are shipped with multitudinous
control primitives, miscellaneous data structures, and flexible
operating patterns. Most of the existing NFV platforms adopt
GPL. For example, OpenNF relies on a C++ API to develop
control applications. NFVNice exposes the “libnf” C library
to perform I/O operations asynchronously and to monitor
the workload of each VNF. OpenBox exposes a Java API
for operators to specify processing logic and subscribe to
system events. Slick API allows developers to specify service
policies in Python, while NetBricks achieves it with a Rust
API. Compared to GPLs, DSLs provide higher-level optimized
abstractions for specific problems, and they usually operate in
an environment with limited operation patterns and restricted
resource usage. For example, Flick language supports parallel
execution and safe resource sharing. In addition to basic
primitives such as event handling and common data types,
Flick can deserialize input packets into application-specific
data types and vice versa, bringing application semantics into
VNF development. Service policies in Eden are specified in F#
language for safety checking. NFMorph proposes a DSL that
allows developers to express per-packet operations and com-
piler hints for dependency analysis and runtime optimization.
Placement: Service placement is achieved in two steps:
pre-processing and deployment. In the pre-processing phase,
input policies are optimized through graph merging and par-
allelization. In the deployment phase, network services are
installed across NFVI-Nodes with pre-defined objectives. Ex-
isting platforms generally follow the same procedure. For
instance, CoMb consolidates SFCs on a single NFVI-Node
by solving an optimization model based on service and infras-
tructural description. OpenBox merges input processing graphs
with correctness guarantees and deploys the related VNFs to
the specified NFVI-Nodes. Slick employs an inflation heuristic
to consolidate VNFs with minimum cost and uses a placement
algorithm to deploy them while configuring traffic steering
rules on the network switches. E2 also merges multiple ser-
vice graphs to reduce processing redundancy. It models VNF
placement as a graph partition problem over NFVI-Nodes and
employs a heuristic placement algorithm to minimize the inter-
server traffic. SDNFV formulates the placement problem as a
MILP problem and designs a heuristic algorithm to maximize
resource utilization. Metron leverages SNF to optimize the
input graph and constructs a synthesized one, which is subse-
quently split into a stateful subgraph and a stateless subgraph.
The stateful graph is deployed on COTS servers selected by
the Metron server selection scheme. The stateless graph is
offloaded to in-path network elements based on the locations
of the stateful graph. MicroNF performs dependency analysis
for VNF elements and reconstructs the service graph to reduce
redundant processing and improve resource efficiency. It places
the modularized SFCs to the COTS servers by solving an
integer programming problem to minimize inter-VM overhead.
The µNF orchestrator constructs an optimal forwarding graph
by consolidating VNFs performing similar processing, but the
authors did not indicate the placement approaches.
State coordination: With the proliferation of stateful VNFs,
it is critical to timely coordinate the processing states upon
the scaling, migration, and failover of VNFs. However, it
is extremely challenging to simultaneously guarantee flow
affinity, correct processing, and minimal service interruption.
Existing NFV platforms resort to two strategies, state mi-
gration and migration avoidance, respectively. The former
employs different approaches to migrate states. For instance,
Split/Merge suspends traffic flows for all replicas and transfers
IEEE TRANSACTIONS ON NETWORK AND SERVICE MANAGEMENT 11
TABLE I: Design choices for a subset of the existing NFV platforms.
MANO plane Service plane NFV infrastructure (NFVI)
Platform High-level Placement State Execution TCP VNF Packet VNF Virtualization
API engine coordination model function I/O I/O interconnect technique
GPL DSL SM MA RTC Pipe. Poll. Intr. VS Cus. VM Co. Pr.
OpenBox X X X X Kernel X
E2 X X X X X DPDK X
SDNFV X X X DPDK X X
Slick X X X X Kernel X
Eden X X X Kernel X X
MicroNF X X X X DPDK X X X
µNF X X X X DPDK X X X
Metron X X X X DPDK X X
Flurries X X X X DPDK X
MicroBoxes X X DPDK X
OpenNF X X Kernel
Split/Merge X X Kernel X X
ClickNF X X X X DPDK X
Flick X X X X X DPDK X
NetStar X X X X X DPDK X X
StatelessNF X X X X DPDK X
NFMorph X X X X DPDK X X
NetVM X X X DPDK X X
OpenNetVM X X X DPDK X X X
NetBricks X X X X DPDK X X
ClickOS X X X netmap X X
HyperNF netmap X X
IOVTee DPDK X X X
CHC X X VMA X X
NICA X X X VMA X
Polycube X X eBPF X
NFP XDPDK X X
ParaBox DPDK X X
NFVNice X X X DPDK X X
libVNF X X X X X X X
DPDK
X X Xnetmap
kernel
the relevant states across them while configuring the related
traffic routes. Metron divides states of the overloaded SFC into
two groups and copies one group to new replicas. However,
both approaches incur in-transit packet losses that might lead
to state inconsistency. OpenNF uses a centralized controller
and in-path OpenFlow switches to preserve flow affinity and
packet processing order without in-transit losses. MicroNF,
UNO, and OpenBox also advocate this solution for state
coordination. Similarly, TFM deploys a “box” at each VNF
instance to buffer incoming packets and feed them in the
correct order to the new replica. In contrast, some platforms
adopt a migration avoidance strategy to avoid state migration
overhead. In particular, E2 splits the flow space and steers part
of the incoming flows to the new instance while keeps serving
existing flows till termination. Another migration avoidance
strategy is state externalization. For example, StatelessNF,
CHC, NetStar, and libVNF keep VNF processing states in
external data stores to avoid state migration costs.
B. Service plane
NFV platforms are required to consider several critical
design choices in the service plane.
Execution model: In NFV domain, two VNF execution
models are adopted: run-to-completion (RTC) and pipeline.
In the RTC model, all the elements of a VNF run on a
single thread, whereas in the pipeline model, each element
is pinned to a separate thread, as illustrated in Fig. 4a. The
performance of either model is highly dependent on processing
complexity and input workload, which leads to different levels
of cache and memory access patterns. In general, the RTC
model presents better performance executing simple VNFs or
short SFCs by eliminating inter-core transfer overhead [60]. It
also requires fewer cores than the pipeline model. However,
the pipeline model enables finer granularity scaling and incurs
fewer cache misses processing complex VNFs. Some platforms
employ the RTC model to accommodate lightweight VNFs
or trimmed SFCs. For instance, CoMb, NetVM, NetBricks,
ClickNF, ClickOS, NetStar, and SafeBricks execute VNFs in
the RTC model to avoid the inter-core transfer and synchro-
nization overhead; Metron offloads part of its SFCs to the in-
path hardware devices, executing the trimmed tasks in RTC
model on COTS servers. Other platforms employ the pipeline
model. In particular, µNF and MicroNF decompose VNFs or
SFCs into loosely-coupled elements to be scaled individually.
TCP functionality: As stateful VNFs have become an im-
portant building block in the NFV ecosystem, it is worth
pointing out existing platforms that implement or integrate
TCP/IP stack to support stateful VNFs at layer 4 or beyond.
ClickNF is equipped with a full-fledge modular TCP stack
to facilitate the end-host application development. Microboxes
comes with a modular, customizable TCP stack that can be
shared among a group of VNFs to eliminate redundant pro-
IEEE TRANSACTIONS ON NETWORK AND SERVICE MANAGEMENT 12
cessing. OpenANFV also designs a TCP stack in the userspace.
NICA even implements a simplified TCP stack in Smart-
NICs to enrich its in-path processing features. xOMB stack
only implements simple functions such as TCP connection
termination. Instead of developing TCP functionalities from
scratch, some platforms choose to directly incorporate third-
party solutions. For example, Flick integrates the high-speed
kernel-bypassing mTCP stack [147] to realize transport layer
VNFs, NetStar directly employs a third-party user-space TCP
stack with future/promise abstraction. libVNF is designed to be
generic by integrating both the standard networking stack and
mTCP. Besides, all the NFV platforms using the kernel TCP/IP
stack and POSIX sockets are granted TCP functionalities by
default. In particular, Polycube directly cooperates with the
kernel TCP/IP stack to build complex SFCs.
VNF I/O: There are also two alternative means for VNFs
to perform packet I/O, namely polling mode and interrupt
mode. VNFs running in polling mode keep querying the NICs
or upstream VNFs for data, which normally renders better
performance at the cost of wasted CPU cycles and increased
energy consumption due to idle waiting. Interrupt-based I/O
usually does not entail wasted resources but suffers from
performance losses due to interrupt propagation delay and
cache line warm-up. Existing NFV platforms such as UNO,
CHC, NetBricks, ClickNF, NetStar, and StatelessNF, execute
VNFs in the polling mode to enhance performance. Other
platforms such as Flick, NFVNice, xOMB, ClickOS, Flurries,
and libVNF execute VNFs in interrupt mode.
Secure execution: As VNFs are increasingly delegated
to untrusted environments (e.g., public cloud or third-party
networks), traffic data and VNF internals are exposed to
potential cyber-attacks. Existing NFV platforms secure the
execution of VNFs with encryption and shield execution.
Platforms adopting the former (e.g., vEPC-sec, Embark) lever-
age cryptographic schemes to enable VNFs to operate directly
on encrypted traffic. Platforms adopting shield execution run
VNFs in memory regions called enclaves whose contents are
strictly protected from external accesses. For example, S-NFV,
TrustedClick, ShieldBox, SafeLib, SafeBricks, and LightBox
leverage Intel SGX to provide a shield execution environment
for VNFs. Similarly, NetVM and OpenNetVM place VNFs
inside trusted domains to ensure security. Compared to shield
execution, encryption approaches usually incur higher over-
head imposed by the complex cryptographic operations and
support a limited set of functionalities.
C. NFV Infrastructure (NFVI)
Packet I/O techniques: Existing NFV platforms adopt dif-
ferent I/O techniques to exchange packets with the outside
network through physical NICs. When such NICs are managed
by COTS servers, the two approaches used for I/O are kernel-
based and kernel-bypassing, as shown in Fig. 4b. Traditional
network applications rely on the feature-rich kernel stack for
packet I/O, although the overhead imposed by kernel stack
makes software solutions fail to sustain line-rate process-
ing [148]. This bottleneck can be overcome by adopting kernel-
bypassing techniques (e.g., DPDK [149], netmap [150]).
Netmap partially bypasses the kernel, and it adopts system call
based validation and interrupt-based packet reception. DPDK
employs complete kernel-bypassing and poll-mode drivers to
boost performance. They also expose APIs to simplify VNF
development. As shown in Tab. I, most of platforms such as E2,
Flick, ClickNF, IOVTee, NetStar, µNF, Flurries, StatelessNF,
NetVM, and OpenNetVM leverage DPDK for packet I/O.
netmap is used by ClickOS and HyperNF. NICA and CHC
adopt Mellanox Message Accelerator (VMA) [151], another
kernel-bypassing technique with standard socket APIs and
user-space library. Note that even though the traditional kernel-
based approach fails to render comparable performance as
kernel-bypassing techniques, it can still be useful when the
VNFs are not I/O intensive or the cost to set up a kernel-
bypassing stack is too high. The extended Berkeley Packet
Filter (eBPF) [25] adopts an in-kernel virtual machine to run
user-space programs that can be used to execute network
functions. In conjunction with the XDP enhancements [152],
it provides high-performance packet processing capabilities.
eBPF is adopted by Polycube for packet I/O. Note that libVNF
supports kernel, DPDK, and netmap to achieve generality.
VNF interconnects: Existing NFV platforms concatenate
consolidated VNFs by integrating or implementing software
switches. Software switches are widely used by existing plat-
forms for efficient traffic steering. For instance, E2 augments
BESS [153] as data plane, ClickOS and HyperNF extend
VALE switch [154], CoMb customizes the Click Modular
Router [22]. Metron, MiddleClick, SCC, and SplitBox lever-
age FastClick [148] to transfer packets between VNFs and
the network. Split/Merge, TFM, and MicroNF employ Open
vSwitch (OVS) [155] for VM networking. UNO extends OVS-
DPDK [156] to steer packets at both host and SmartNIC level.
NetBricks adopts both OVS-DPDK and BESS to interconnect
VNFs. More details about the performance of these software
switches can be found in [157]–[159]. Rather than adopt-
ing third-party software switches, some platforms implement
customized solutions. For instance, G-NET uses a bespoke
software switch to route packets between VNFs and physical
NICs, NetVM implements a hypervisor software switch to
enable state- and data-dependent forwarding.
Virtualization technique: As the central point of any NFV
platform, existing implementations deploy network functions
in Virtual Machines (VMs),Containers, and Processes.
As illustrated in Fig. 4c, virtualization is implemented at
different layers in the commodity hardware, and therefore
present different degrees of isolation and resource require-
ments. VM is a hardware-level virtualization technique that
relies on the Virtual Machine Monitor (VMM) or hypervisor
to accommodate VNFs2. Hypervisors also manage the VMs
for efficient resource sharing. Some platforms adopt different
VM hypervisors to host VNFs. For example, NetVM, NICA,
OpenANFV, IOVTee, and SDNFV adopt KVM; Split/Merge,
HyperNF, and FlowOS adopt Xen. However, VMs commonly
impose heavy resource demands, huge memory footprints, and
2Note that there is another kind of hypervisor that operates at OS level
(namely, hosted hypervisor) which was excluded from our discussion as rarely
used by existing NFV platforms.
IEEE TRANSACTIONS ON NETWORK AND SERVICE MANAGEMENT 13
(a) Execution models
Device Driver
TCP/IP Stack
NICs
Application
Device Driver
Kernel Space
User Space
Application
(b) Packet I/O techniques
Infrastructure Infrastructure
Hypervisor Host OS Host OS
Container Engine
Libs/Bins
Guest OS
Libs/Bins
VNFs
Virtual Machine
Infrastructure
Libs/Bins
VNFs
Container
VNFs
Process
(c) Virtualization techniques
Fig. 4: Illustration of several key design choices
high migration costs. To overcome these deficits, ClickOS
and CliMBOS adopt unikernel VMs that are small, agile,
and fast-to-boot. The advent of containers, such as LXC and
Docker, gives another option. Compared to VMs, containers
are OS-level virtualization techniques with a small memory
footprint, short boot time, high deployment density, and low
migration cost. The disadvantages of containers include weak
isolation and degraded security. In terms of performance, they
both can sustain line rate processing using tailored I/O paths.
At present, many existing NFV platforms opt for container-
ized VNFs. For instance, OpenNetVM, Flurries, MicroBoxes,
NFVNice, MVMP, NFP, ParaBox, MVMP, statelessNF, and
GNFC employ Docker, while CHC and Iron adopt LXC. Aside
from VMs and containers, some platforms deploy VNFs as
processes to trade isolation for performance. For example,
NetBricks, ClickNF, libVNF, and SafeLib execute VNFs as
processes and use different means to guarantee isolation.
GPUNFV, Gen, FlowShader, Grus, and G-NET execute VNFs
or SFCs as GPU threads. Note that some platforms feature
multiple techniques. For example, OpenNetVM and µNF adopt
both process and container. MicroNF runs containers inside
VMs probably to improve security.
D. Other design choices
As discussed in [160], there is a large assortment of accel-
eration techniques for high-speed packet processing. Here, we
choose the most commonly utilized techniques and enumerate
their adoption by existing NFV platforms. The optimization
knobs we consider including zero-copy, batching, memory pre-
allocation, parallel execution, CPU cache optimization, and
computation offloading. Although these optimizations are com-
monly applied by high-speed packet processing applications,
we discuss them in the context of NFV.
Zero-copy: In the high-speed packet processing domain,
runtime memory copy is an expensive operation that usually
leads to unbearable overhead. For the sake of performance,
many existing NFV platforms deliver packets across VNFs
or memory boundaries in a zero-copy manner, by copying
only their associated packet descriptors. For example, µNF
implements a zero-copy port abstraction that only exchanges
packet addresses instead of copying full packets between
VNFs. NetVM employs a shared memory mechanism to enable
zero-copy packet delivery to and between the VNFs running
in VMs. Instead of shared memory, IOVTee implements a
safe zero-copy mechanism through memory mapping between
hypervisor switch and VM. NetBricks adopts Unique Types to
implement safe zero-copy packet delivery between NFs. The
TCP stack of ClickNF exposes zero-copy interfaces to interact
with user-space VNF. NICA leverages ring buffers for zero-
copy message exchange between the F-NIC units and the user-
space VNFs. GPUNFV achieves zero-copy packet delivery
across CPU and GPU boundary through CUDA’s page-lock
memory. G-NET’s switch also employs a zero-copy design.
Batching: In high-speed packet processing frameworks, I/O
batching is widely used to amortize the overhead of accessing
the physical NIC over multiple packets. This technique is also
employed by some NFV platforms to enhance performance.
For example, NFVNice and EdgeMiner batch the I/O interrupts
to amortize VNF wakeup overhead. SCC handles the system
calls of VNF I/O in dynamic batches to reduce the overhead of
context switches. NFMorph advocates optimizing performance
with batch tuning. The VNFs on µNF platform perform packet
I/O in batches through the intermediate ring buffers. The
TCP stack of ClickNF exchanges packets with the user-space
VNFs in batches. StatelessNF aggregates multiple read/write
requests to the data store into a single request to amortize
the overhead of remote procedure call (RPC). SafeBricks
implements an in-enclave module to perform batched packet
I/O between the enclave and the host. LightBox adopts packet
batching to amortize the system call overhead. GPUNFV, Grus,
FlowShader, G-NET, and Gen deliver packets between CPU
and GPU in dynamic batches.
Pre-allocation: Runtime memory allocation remains a
heavy task. Barring pre-allocating packet buffers and de-
scriptors for packet I/O with physical NICs, existing NFV
platforms usually reserve memory regions to stage and reuse
other relevant packet processing data structures. For example,
libVNF pre-allocates memory pools for its per-core, persis-
tent request objects, and lock-free packet buffers. Flick pre-
allocates its task graphs and queues. S6 pre-allocates a pool of
the cooperative, user-space, per-flow micro-threads to avoid the
IEEE TRANSACTIONS ON NETWORK AND SERVICE MANAGEMENT 14
dynamic thread creation/deletion overhead. NetVM maintains
a pool of idle VMs for prompt VNF migration. ShieldBox pre-
allocates packet descriptor memory. LightBox pre-allocates
state management data structures.
Parallel execution: To take advantage of the multicore
CPUs, many platforms explore possibilities for parallelization.
µNF performs a dependency analysis on its forwarding graphs
to identify parallelize VNFs. Consecutive VNFs are deemed
parallelizable if they perform read-only operations or update
disjoint packet regions. Then these VNFs are assigned inde-
pendent CPU cores to process packets. A reference counter
is attached as meta-data to avoid out-of-order operations from
downstream VNFs. Likewise, SDNFV allows multiple VNFs
to access a packet in parallel using a reference counter em-
bedded in the packet descriptor. Eden exposes a concurrency
model that creates consistent state copies for multiple VNFs to
execute in parallel in the Eden enclave. CoMb allocates each
SFC an independent shim layer to allow for parallel execution
of multiple SFCs. Flick instantiates a new task graph for
each new connection and schedules the tasks of these graphs
onto multiple worker cores in parallel. NetBricks runs per-
tenant service processing graphs in parallel in a multi-tenant
environment. ClickNF utilizes the Receive-Side Scaling (RSS)
of physical NICs to distribute incoming packets to multiple
cores with flow-level affinity guaranteed. NetStar builds VNFs
with a share-nothing thread model and distributes incoming
packets to different threads for paralleled multicore processing.
libVNF is built with multicore scalability of VNF and uses per-
core data structures to avoid inter-core communication which
can hamper the multicore scalability of a VNF.
Cache optimization: Modern CPUs are equipped with hi-
erarchical caches between their cores and the main memory.
Cache misses result in extra access to other cache levels or the
main memory, which significantly slows down the processing
speed. Many existing NFV platforms are aware of this issue
and explore opportunities for cache optimization. NetContainer
aims at exploiting cache locality at inter-flow and intra-flow
levels for NFV workload and leverages page coloring tech-
niques to aggregate buffer pages to separate cache regions to
avoid cache contention. ResQ exploits Intel Cache Allocation
Technology with corresponding buffer sizing to eliminate last
level cache invalidation while ensuring performance isolation.
LightBox adapts cache line protection techniques to reduce the
cache miss rate. µNF and NFMorph perform data prefetching
in batches to increase the cache hit rate. Some platforms also
make their critical internal data structures cache-optimized. For
example, the request objects of libVNF are cache-optimized,
all the per-core data structures of ClickNF are cache-aligned.
Computation offloading: Computation offloading is widely
adopted by existing NFV platforms to alleviate the pressure
of COTS servers. Potential resources to offload computing
tasks include GPU, smartNICs, and in-path network switches.
E2 selectively offloads simple VNFs to adjacent hardware
switches. Metron offloads stateless operations to the in-path
programmable NICs and switches. OpenBox and Eden also
implement their forwarding plane in hardware. OpenNetVM
and OpenANFV incorporate programmable NICs or FPGAs
for computation offloading. ClickNF explores common NIC
features to perform TCP/IP checksum offloading, TCP seg-
mentation offloading (TSO), and large receive offloading
(LRO). GPUNFV, Gen, FlowShader, Grus, and G-NET employ
GPU offloading to boost performance. SmartNICs are com-
monly equipped with programmable, multi-core processors
and an integrated operating system, making them ideal to
execute computation tasks. UNO exploits smartNICs to offload
VNFs, forwarding rules, flow tables, and crypto/compression
operations. NICA leverages the inline processing of FPGA on
smartNICs to accelerate data plane processing.
V. OPEN ISSUES AND CHALLENGES
In this section, we envision some future directions for NFV
platform design, including Artificial Intelligence (AI), network
slicing, and Internet of Things (IoT), and discuss the potential
challenges therein.
A. AI in NFV
With the proliferation of Artificial Intelligence, an increasing
amount of effort has been devoted to driving networks using
AI techniques without human intervention. Although Machine
Learning (ML) and Deep Learning (DL) techniques have
begun to be adopted by some NFV platforms for traffic
prediction and runtime management [54], [95], [96], [145], AI
is still far away from complete integration into NFV. Since AI
techniques such as Neural Networks are intrinsically complex
(if not impossible) to comprehend, a huge amount of domain-
specific expertise is required to guarantee the correctness and
reliability of the AI-integrated NFV solutions. Developers
need to master knowledge in both NFV and AI domains to
implement production-ready NFV platforms, making it more
difficult for newbies to get started and expensive for companies
to recruit talents. As the base of ML/DL, large sets of relevant
data need to be collected and pre-processed. While plenty of
datasets for legacy networks and applications are available, the
patterns or features may be at odds with contemporary NFV
and 5G networks. It is also time-consuming to extract correct
features and train the models, not to mention the tedious
verification process to avoid inaccuracy or overfitting. While
we believe AI will become commonplace in the NFV domain,
it is still in its infancy in the telecommunication industry and
several challenges yet need to be overcome to thoroughly
unleash the potentials of AI in NFV.
B. Network slicing
As one of the key enabling technologies for 5G, network
slicing promises to slice the physical network infrastructure
into multiple self-contained, isolated, and programmable logi-
cal (or virtual) networks to indulge different genres of services
demanded by assorted tenants [161]. Combined with other
trending network softwarization technologies such as SDN
and cloud/edge computing, NFV platforms are envisaged to
realize network slicing over 5G infrastructure. We identify
several fundamental challenges that need to be surmounted.
Firstly, creating variable-sized network slices for varied ten-
ants or business verticals entails effective management of
IEEE TRANSACTIONS ON NETWORK AND SERVICE MANAGEMENT 15
an NFV platform’s components, including dynamic slice in-
stantiation/termination, cognitive resource scheduling among
network slices, adaptive VNF placement and configuration for
each slice, efficient intra-/inter-slice communication, and so
on. Although some of the management issues have been indi-
vidually resolved, few platforms come up with a joint solution
to manage heterogeneous network slices, each of which calls
for a particular set of resource and SLA requirements. As
a result, it is of uttermost importance for NFV platforms to
manage their services and resources tailored for each slice
with guaranteed performance and efficient resource usage.
Similarly, each network slice may also come with different
levels of security concerns originated from diverse industrial
verticals, NFV platforms are thus required to provide means
to ensure customized security policies. At a minimum, attacks
on one slice must be unconditionally isolated from the others.
It is also challenging to enforce security policies for slices
spanning across multiple administrative domains. Therefore,
NFV platforms are required to implement a brand-new set of
mechanisms to eliminate these security concerns.
C. Integration with IoT
In the foreseeable 5G era, the IoT ecosystem is expected to
accommodate an unprecedented deluge of data traffic gener-
ated by hundreds of billions of heterogeneous interconnected
devices. NFV platforms are envisioned to enable massive
deployment and flexible management of IoT services [162].
However, most of the platforms reviewed in this paper are
not specifically designed for IoT use cases. At present, only
a few NFV platforms are tailored for IoT in terms of user
privacy [102], QoS [68], deployment [66], and still, a vast
design space must be explored in addition to proof-of-concept
implementations. In particular, it is unclear whether NFV plat-
forms can handle enormous data traffic with ultra-low latency
and high-throughput. While many existing NFV platforms
manage to sustain 40/100 Gbps links using high-speed I/O
techniques, their performances have not been tested under IoT
configurations. The NFV platforms may also face scalabil-
ity issues due to the immense number of connections from
densely distributed IoT devices, making service provisioning
and scheduling even more critical. Energy consumption is yet
another crucial challenge faced by IoT systems, especially
under the progressively heavy and fluctuating traffic load.
Albeit a large collection of scientific research has been devoted
to energy efficiency, few NFV platforms include this as their
design goals. Also, as IoT devices are increasingly deployed
in third-party environments, it is equally important to ensure
the security of IoT applications. Despite NFV platforms usu-
ally leverage data encryption and shield execution to secure
VNFs, their applicability in 5G-IoT environments is yet to be
comprehensively validated.
VI. CONCLUSION
As a novel paradigm to shift network management and
service provisioning, NFV is expected to revolutionize the
next-generation telecommunication networks. To accelerate the
innovation and commercial adoption of NFV, a large spectrum
of platforms have been implemented in the last eight years.
While sharing the ultimate objective of promoting NFV, they
usually tackle divergent problems in the NFV eco-system and
embrace disparate design choices to achieve different perfor-
mance metrics or service layer agreements, and few works have
been devoted to interpreting this huge collection of platform
implementations. In this paper, we concentrate on existing
NFV platforms and strive for comprehending their design.
After introducing the NFV reference architecture, we present
our taxonomy on existing NFV platforms based on their focus
on the life cycle of a network function. Then we explore the
design space and investigate the various choices individual
NFV platforms opt for to tackle different implementation
challenges. Last but not least, we envision future research
directions for NFV platforms concerning AI, network slicing,
and IoT, and discuss the variety of challenges to overcome. We
believe that our work presents a first-hand guideline for both
network operators and developers to choose or design NFV
solutions according to their respective requirements.
VII. ACKN OWLEDGEMENTS
The work has been supported by European Horizon 2020
Programme through the project 5G-EVE on “European 5G
validation platform for extensive trials” (grant agreement
n. 815074).
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Tianzhu Zhang is a research engineer at Nokia Bell
Labs. He received his B.S. degree from Huazhong
University of Science and Technology, Wuhan,
China, in 2012. Afterward, he received the M.S.
degree in 2014, and the Ph.D. degree in 2017, both
from Politecnico di Torino, Turin, Italy. From 2017
to 2019, he was a PostDoc researcher at Telecom
ParisTech and LINCS, under a research grant from
Cisco Systems. He joined Nokia Bell Labs in Au-
gust 2020. His current research interests include
SDN/NFV, Artificial Intelligence, Edge Computing,
Robotics, Big Data, and log analysis.
Han Qiu (Member, IEEE) received the B.E. degree
from the Beijing University of Posts and Telecommu-
nications, Beijing, China, in 2011, the M.S. degree
from Telecom-ParisTech (Institute Eurecom), Biot,
France, in 2013, and the Ph.D. degree in computer
science from the Department of Networks and Com-
puter Science, Telecom-ParisTech, Paris, France, in
2017. He is currently a Research Engineer with
Telecom Paris, France. His research interests include
AI security, big data security, applied cryptography,
and cloud computing.
Leonardo Linguaglossa is an assistant professor
at Telecom Paris (France). He received his master
degree in telecommunication engineering at Uni-
versity of Catania (Italy) in 2012. He pursued a
Ph.D. in Computer Networks in 2016 through a
joint doctoral program with Alcatel-Lucent Bell Labs
(nowadays Nokia), INRIA and University Paris 7.
Leonardo’s research interests focus on architecture,
design and prototyping of systems for high-speed
software packet processing, future Internet architec-
ture and SDN.
Walter Cerroni (M’01, SM’16) is an Associate
Professor of communication networks at the Uni-
versity of Bologna, Italy. His recent research inter-
ests include software-defined networking, network
function virtualization, service function chaining in
cloud computing platforms, intent-based northbound
interfaces for multi-domain/multi-technology virtu-
alized infrastructure management, modeling and de-
sign of inter- and intra-data center networks. He co-
authored more than 130 articles published in the
most renowned international journals, magazines and
conference proceedings. He serves/served as Series Editor for the IEEE
Communications Magazine, Associate Editor for the IEEE Communications
Letters, and Technical Program Co-Chair for IEEE-sponsored international
workshops and conferences.
Paolo Giaccone (M’99, SM’16) received the Dr.Ing.
and Ph.D. degrees in telecommunications engineer-
ing from the Politecnico di Torino, Torino, Italy, in
1998 and 2001, respectively. During the summer of
1998, he was with High Speed Networks Research
Group, Lucent Technology-Bell Labs, Holmdel, NJ,
USA. From 2000 to 2001 and in 2002, he was with
Information Systems Networking Lab, Department
of Electrical Engineering, Stanford University, Stan-
ford, CA, USA. He is currently an Associate Profes-
sor with the Department of Electronics, Politecnico
di Torino. His main area of interest is in the design of network algorithms, in
particular for the control of software-defined networks, and cloud computing
systems.
... Zoure et al. [20] Network services anomalies in NFV 2022 Zhang et al. [21] NFV platforms, design and taxonomy 2021 Hamdan et al. [22] Load balancing techniques in SDN 2021 Fei et al. [23] NFV deployment acceleration 2020 Kaur et al. [24] vNF placement, availability, and load balancing 2020 Hantouti et al. [25] Service function, 5G and next-generation networks 2020 Bonfim et al. [26] NFV architectures; NFV/SDN design taxonomy 2019 Hantouti et al. [27] Traffic steering in SFC; SDN-based chaining evaluation 2019 ...
... In their work, Zhang et al. [21] presented NFV platform design choices. They presented three main open issues in NFV: (1) the use of artificial intelligence in NFV, (2) network slicing, that is, the management of network slices, the communication between slices and placement of network slices, and (3) the integration of NFV with IoT. ...
Research
Full-text available
Network slicing has become a fundamental property for next-generation networks, especially because an inherent part of 5G standardisation is the ability for service providers to migrate some or all of their network services to a virtual network infrastructure, thereby reducing both capital and operational costs. With network function virtualisation (NFV), network functions (NFs) such as firewalls, traffic load balancers, content filters, and intrusion detection systems (IDS) are either instantiated on virtual machines (VMs) or lightweight containers, often chained together to create a service function chain (SFC). In this work, we review the state-of-the-art NFV and SFC implementation frameworks and present a taxonomy of the current proposals. Our taxonomy comprises three major categories based on the primary objectives of each of the surveyed frameworks: (1) resource allocation and service orchestration, (2) performance tuning, and (3) resilience and fault recovery. We also identify some key open research challenges that require further exploration by the research community to achieve scalable, resilient, and high-performance NFV/SFC deployments in next-generation networks.
... These continue to play a pivotal role in the vision of 6G, forming the backbone of flexible and intelligent networks [4]. SDN abstracts the underlying network while NFV introduces softwarisation and decouples network functions from the underlying hardware, overall creating a hardware agnostic virtualized environment for network applications [5]. This shift has opened the market to a wider movement towards virtualised applications and services in key verticals such as automatic vehicles, smart grid, virtual reality (VR), internet of things (IoT), industry 4.0, etc., and also includes verticals that previously relied solely on specialised hardware. ...
... A key challenge highlighted in the conceptualization of 6G is to impose stringent end-to-end QoS requirements within heterogeneous services [4]. To this end, 5G deployments include the proposition of network slicing, clustering applications with similar demands in an appropriate Cloud environment [5]. This ensures the placement of latency-critical URLLC applications in a high availability slice, where re-sources are suitably provisioned to ensure reliability. ...
Article
Full-text available
Recent advancements in the domain of Network Function Virtualization (NFV), and rollout of next-generation networks have necessitated the requirement for the upkeep of latency-critical application architectures in future networks and communications. While Cloud service providers recognize the evolving mission-critical requirements in latency sensitive verticals such as autonomous driving, multimedia, gaming, telecommunications, and virtual reality, there is a wide gap to bridge the Quality of Service (QoS) constraints for the end-user experience. Most latency-critical services are over-provisioned on all fronts to offer reliability, which is inefficient towards scalability in the long run. To address this, we propose a strategy to model frequent violations on the application level as a multi-output target to enable more complex decision-making in the management of virtualised communication networks. In this work, we utilize data from a real-world deployment to configure and draft a realistic set of Service Level Objectives (SLOs) for a voice based NFV application, and develop a deep neural network based multi-label classification methodology to identify and predict multiple categories of SLO breaches associated with an application state. With this, we aim to gain granular SLA and SLO violation insights, enabling us to study and mitigate their impact and inform precision in drafting proactive scaling policies. We further compare the performance against a set of multi-label compatible machine learning classifiers, and address class imbalance in a multi-label setup. We perform a comprehensive evaluation to assess the performance on example-based, label-based and ranking-based measures, and demonstrate the suitability of deep learning in such a use-case.
... Software Defined Networking (SDN) [4] and Network Function Virtualization (NFV) [42] showed a significant promise in meeting massive IoT needs by offloading the computation to fog infrastructures close to edge devices and scaling IoT capabilities by allowing on-demand service orchestration and management. In addition to improving the management of network flows in massive IoT systems, SDN allows better isolation of data flows and improves resiliency to failures for critical data [21]. ...
... The latter also signs and verifies IoT transactions across distributed IoT nodes in which data could be signed and verified in near realtime. Leveraging SDN/NFV enforces the coordination of massive IoT nodes and increases their performance by creating a modular architecture in which virtual miners can be hosted inside a NFV platform such as the Open Platform for NFV (OPNFV) [42]. On the other hand, the SDN controller network abstraction layer enforces the security policies and configuration of the data plane by protecting flow table rules inside virtual SDN routers from intentional or unintentional tampering. ...
... As a final remark, it is noteworthy the significant impact that the ETSI NFV architectural framework is causing within the telecommunications community where it has been widely embraced. In particular, a significant effort has focused on providing functional implementations of the ETSI NFV framework, aiming at accelerating, enriching, and sustaining the development and adoption of this technology [14]. On the other hand, these initiatives have also allowed NFV to become a key player in the development of novel concepts arising from 5G networks such as network slicing [15]. ...
Article
Full-text available
Network Functions Virtualization (NFV) is a key technology for network automation and has been instrumental to materialize the disruptive view of 5G and beyond mobile networks. In particular, 5G embraces NFV to support the automated and agile provision of telecommunication and vertical services as a composition of versatile virtualized components, referred to as Virtual Network Functions (VNFs). It provides a high degree of flexibility in placing these components on distributed NFV infrastructures (e.g., at the network edge, close to end users). Still, this flexibility creates new challenges in terms of VNF connectivity. To address these challenges, we introduce a novel secure link-layer connectivity platform, L2S. Our solution can automatically be deployed and configured as a regular multi-site NFV service, providing the abstraction of a layer-2 switch that offers link-layer connectivity to VNFs deployed on remote NFV sites. Inter-site communications are effectively protected using existing security solutions and protocols, such as IP security (IPsec). We have developed a functional prototype of L2S using open-source software technologies. Our evaluation results indicate that this prototype can perform IP tunneling and cryptographic operations at Gb/s data rates. Finally, we have validated L2S using a multi-site NFV ecosystem at the Telefonica Open Network Innovation Centre (5TONIC), using our solution to support a multicast-based IP television service.
... This current trend of "network softwarization", fueled by the growing popularity of Software Defined Networking (SDN) [7] or Network Function Virtualization (NFV) [1], can significantly reduce the maintenance cost of network services, as the life-cycle of software evolves much faster than that of hardware-based solutions [8]. Moreover, it opens new business models for network services. ...
Conference Paper
Full-text available
The on-going process of softwarization of IT networks promises to reduce the operational and management costs of network infrastructures by replacing hardware middleboxes with equivalent pieces of code executed on general-purpose servers. Alongside the benefits from the operator’s perspective, new strategies to provide the network’s resources to users are arising. Following the principle of “everything as a service”, multiple tenants can access the required resources – typically CPUs, NICs, or RAM – according to a Service-Level Agreement. However, tenants’ applications may require a complex and expensive measurement infrastructure to continuously monitor the network function’s state. Although the application’s specific behavior is unknown (and often opaque to the infrastructure owner), the software nature of (virtual) network functions (VNFs) may be the key to infer the behavior of the high-level functions by accessing low-level information, which is still under the control of the operating system and therefore of the infrastructure owner. As such, in the scenario of software VNFs executed on COTS servers, the underlying CPU’s behavior can be used as the sole predictor for the high-level VNF state without explicit in-network measurements: in this paper, we develop a novel methodology to infer high-level characteristics such as throughput or packet loss using CPU data instead of network measurements. Our methodology consists of (i) experimentally analyzing the behavior of a CPU that executes a VNF under different loads, (ii) extracting a correlation between the CPU footprint and the high-level application state, and (iii) use this knowledge to detect the previously mentioned network metrics. Our code and datasets are publicly available.
Article
The Softwarization of networks is enabled by the SDN (Software-Defined Networking), NV (Network Virtualization), and NFV (Network Function Virtualization) paradigms, and offers many advantages for network operators, service providers and data-center providers. Given the strong interest in both industry and academia in the softwarization of telecommunication networks and cloud computing infrastructures, a series of special issues was established in IEEE Transactions on Network and Service Management, which aims at the timely publication of recent innovative research results on the management of softwarized networks.
Preprint
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Due to the intrinsically inefficient service provisioning in traditional networks, Network Function Virtualization (NFV) keeps gaining attention from both industry and academia. By replacing the purpose-built, expensive, proprietary network equipment with software network functions consolidated on commodity hardware, NFV envisions a shift towards a more agile and open service provisioning paradigm with much lower capital expenditure (CapEx) and operational expenditure (OpEx). Nonetheless, just like any complex system, NFV platforms commonly consist of abounding software and hardware components and usually incorporate disparate design choices based on distinct motivations or use cases. This broad collection of convoluted alternatives makes it extremely arduous for network operators to make proper choices. Although numerous efforts have been devoted to investigating different aspects of NFV, none of them specifically focused on NFV platforms or attempted to explore the design space. In this paper, we present a comprehensive survey on NFV platform design. Our study solely targets existing NFV platform implementations. We begin with an architectural view of the standard reference NFV platform and present our taxonomy of existing NFV platforms based on the principal purpose of design. Then we thoroughly explore the design space and elaborate on the implementation choices each platform opts for. We believe that our study gives a detailed guideline for network operators or service providers to choose or implement the most appropriate NFV platforms based on their respective requirements. Note that this report serves as a complementary document for a published IEEE TNSM paper [1]. We will periodically update this document to include the newly proposed NFV platforms and design choices.
Article
Full-text available
The simple programming model and very low-overhead I/O capabilities of emerging packet processing techniques leveraging kernel-bypass I/O and poll-mode processing is gaining significant popularity for building high performance software middleboxes (aka Virtual Network Functions (VNFs)). However, existing OS schedulers fall short in rightsizing CPU allocation to poll-mode VNFs due to the schedulers' shortcoming in capturing the actual processing cost of these VNFs. This issue is further exacerbated by their inability to consider VNF processing order when VNFs are chained to form Service Function Chains (SFCs). The state-of-the-art VNF schedulers proposed as an alternative to OS schedulers are intrusive, requiring the VNFs to be built with scheduler specific libraries or having carefully selected scheduling checkpoints. This highly restricts the VNFs that can properly work with these schedulers. In this paper, we present UNiS, a User-space Non-intrusive work-flow aware VNF Scheduler. Unlike existing approaches, UNiS is non-intrusive, i.e., does not require VNF modifications and treats poll-mode VNFs as black boxes. UNiS is also workflow-aware, i.e., takes SFC processing order into account while scheduling VNFs. Testbed experiments show that UNiS is able to achieve a throughput within 90% and 98% of that achievable using an intrusive cooperative scheduler for synthetic and real data center traffic, respectively.
Article
Full-text available
Managing Network Function (NF) service chains requires careful system resource management. We propose NFVnice, a user space NF scheduling and service chain management framework to provide fair, efficient and dynamic resource scheduling capabilities on Network Function Virtualization (NFV) platforms. The NFVnice framework monitors load on a service chain at high frequency (1000Hz) and employs backpressure to shed load early in the service chain, thereby preventing wasted work. Borrowing concepts such as rate proportional scheduling from hardware packet schedulers, CPU shares are computed by accounting for heterogeneous packet processing costs of NFs, I/O, and traffic arrival characteristics. By leveraging cgroups, a user space process scheduling abstraction exposed by the operating system, NFVnice is capable of controlling when network functions should be scheduled. NFVnice improves NF performance by complementing the capabilities of the OS scheduler but without requiring changes to the OS's scheduling mechanisms. Our controlled experiments show that NFVnice provides the appropriate rate-cost proportional fair share of CPU to NFs and significantly improves NF performance (throughput and latency) by reducing wasted work across an NF chain, compared to using the default OS scheduler. NFVnice achieves this even for heterogeneous NFs with vastly different computational costs and for heterogeneous workloads.
Conference Paper
Full-text available
Software switches are increasingly used in network function virtualization (NFV) to route traffic between virtualized network functions (VNFs) and physical network interface cards (NICs). Understanding of alternative switch designs remains deficient, however, in the absence of a comprehensive, comparative performance analysis. In this paper, we propose a methodology intended to be fair and use it to compare the performance of seven state-of-the-art software switches. We first explore their respective design spaces and then compare their performance under four representative test scenarios. Each scenario corresponds to a specific case of routing NFV traffic between NICs and/or VNFs. Our experimental results show that no single software switch prevails in all scenarios. It is therefore important to choose the one that is best adapted to a given use-case. The presented results and analysis bring a better understanding of design tradeoffs and identify potential bottlenecks that limit the performance of software switches.
Article
Full-text available
The increasing consumption of multimedia services and the demand of high-quality services from customers has triggered a fundamental change in how we administer networks in terms of abstraction, separation, and mapping of forwarding, control and management aspects of service. The industry and the academia are embracing 5G as the future network capable to support next generation vertical applications with different service requirements. To realize this vision in 5G network, the physical network has to be sliced into multiple isolated logical networks of varying sizes and structures which are dedicated to different types of services based on their requirements with different characteristics and requirements(e.g., a slice for massive IoT devices, smartphones or autonomous cars, etc.). Softwarization using Software-Defined Networking (SDN) and Network Function Virtualization (NFV)in 5G networks are expected to fill the void of programmable control and management of network resources. In this paper, we provide a comprehensive review and updated solutions related to 5G network slicing using SDN and NFV. Firstly, we present 5G service quality and business requirements followed by a description of 5G network softwarization and slicing paradigms including essential concepts, history and different use cases. Secondly, we provide a tutorial of 5G network slicing technology enablers including SDN, NFV, MEC, cloud/Fog computing, network hypervisors, virtual machines & containers. Thidly, we comprehensively survey different industrial initiatives and projects that are pushing forward the adoption of SDN and NFV in accelerating 5G network slicing. A comparison of various 5G architectural approaches in terms of practical implementations, technology adoptions and deployment strategies is presented.. Moreover, we provide discussion on various open source orchestrators and proof of concepts representing industrial contribution.. The work also investigates the standardization efforts in 5G networks regarding network slicing and softwarization. Additionally, the article presents the management and orchestration of network slices in a single domain followed by a comprehensive survey of management and orchestration approaches in 5G network slicing across multiple domains while supporting multiple tenants. Furthermore, we highlight the future challenges and research directions regarding network softwarization and slicing using SDN and NFV in 5G networks.
Conference Paper
With rising network rates, cloud vendors increasingly deploy FPGA-based SmartNICs (F-NICs), leveraging their inline processing capabilities to offload hypervisor networking infrastructure. However, the use of F-NICs for accelerating general-purpose server applications in clouds has been limited. NICA is a hardware-software co-designed framework for inline acceleration of the application data plane on F-NICs in multi-tenant systems. A new ikernel programming abstraction, tightly integrated with the network stack, enables application control of F-NIC computations that process application network traffic, with minimal code changes. In addition, NICA’s virtualization architecture supports fine-grain time-sharing of F-NIC logic and provides I/O path virtualization. Together these features enable cost-effective sharing of F-NICs across virtual machines with strict performance guarantees. We prototype NICA on Mellanox F-NICs and integrate ikernels with the high-performance VMA network stack and the KVM hypervisor. We demonstrate significant acceleration of real-world applications in both bare-metal and virtualized environments, while requiring only minor code modifications to accelerate them on F-NICs. For example, a transparent key-value store cache ikernel added to the stock memcached server reaches 40 Gbps server throughput (99% line-rate) at 6 μs 99th-percentile latency for 16-byte key-value pairs, which is 21× the throughput of a 6-core CPU with a kernel-bypass network stack. The throughput scales linearly for up to 6 VMs running independent instances of memcached.
Article
Network Function Virtualization (NFV) enables flexible deployment of network services as applications. However, it is a big challenge to guarantee the Quality of Service (QoS) under unpredictable network traffic while minimizing the processing resources. One typical solution is to realize NF scale-out, scale-in and load balancing by elastically migrating the related traffic flows. However, it is difficult to optimally migrate flows considering the resources and QoS constraints. In this paper, we propose DeepMigration to efficiently and dynamically migrate traffic flows among different NF instances. DeepMigration is a Deep Reinforcement Learning (DRL)-based solution coupled with Graph Neural Network (GNN). By taking advantages of the graph-based relationship deduction ability from our customized GNN and the self-evolution ability from the experience training of DRL, DeepMigration can accurately model the cost (e.g., migration latency) and the benefit (e.g., reducing the number of NF instances) of flow migration among different NF instances and employ dynamic and effective flow migration policies generated by the neural networks to improve the QoS. Experiment results show that DeepMigration reduces the migration latency and saves up to 71.6% of the computation time than the state-of-the-art.
Article
Public cloud offers economy of scale to adapt workload changes in an autonomic manner, maximizing the use of resources. Through network function virtualization (NFV), network operators can move LTE core to the cloud; hence removing their dependency on carrier-grade LTE network functions. Recent research efforts discuss performance, latency, and fault tolerance of LTE NFV, largely ignoring the security aspects. In this paper, we discover new vulnerabilities that LTE NFV face today with no standard solutions to address them. These vulnerabilities span at both LTE control and user planes. To address them, we propose vEPC-sec that cryptographically secures LTE control-plane signaling messages in the cloud. It provides distributed key management and key derivation schemes to derive shared-symmetric keys for securing the communication between any two network functions. Our approach provides encryption and integrity protection to the messages even during virtual machines scalability and failure recovery scenarios. vEPC-sec also prevents user-plane vulnerabilities by ensuring that LTE routing modules should faithfully forward the LTE subscriber packets.