Lab

Networking and Cloud Computing Lab

About the lab

[Lab Heads: Giuseppe Lettieri, Giovanni Stea]

The Lab hosts activities related to Networking and Cloud Computing. As far as networking is concerned, these activities involve design, implementation and evaluation and prototyping of: network protocols – from the MAC to the application layer; network algorithms, such as resource allocation, scheduling, access control; network services and software; tools for network analysis and performance evaluation. As far as Cloud Computing is concerned, the activities involve the design, implementation and evaluation of fast and flexible networking Application Programming Interfaces and I/O datapaths for both virtual and real NICs and switches.

Featured projects (1)

Project
Computing service guarantees, such as maximum end-to-end delay, in packet systems (networks, computer architectures) using Network Calculus. Engineering systems based on performance constraints (e.g., minimizing the amount of resources that can guarantee a given delay bound). Designing software tools that allow researchers to run Network Calculus computations.

Featured research (114)

The Dynamic Random Access Memory (DRAM) is among the major points of contention in multi-core systems. We consider a challenging optimization problem arising in worstcase performance analysis of systems architectures: computing the worst-case delay (WCD) experienced when accessing the DRAM due to the interference of contending requests. The WCD is a crucial input for micro-architectural design of systems with reliable end-to-end performance guarantees, which is required in many applications, such as when strict realtime requirements must be imposed. The problem can be modeled as a mixed integer linear program (MILP), for which standard MILP software struggles to solve even small instances. Using a combination of upper and lower scenario bounding, we show how to solve realistic instances in a matter of few minutes. A novel ingredient of our approach, with respect to other WCD analysis techniques, is the possibility of computing the exact WCD rather than an upper bound, as well as providing the corresponding scenario, which represents crucial information for future memory design improvements.
Network Calculus (NC) is an algebraic theory that represents traffic and service guarantees as curves in a Cartesian plane, in order to compute performance guarantees for flows traversing a network. NC uses transformation operations, e.g., min-plus convolution of two curves, to model how the traffic profile changes with the traversal of network nodes. Such operations, while mathematically well-defined, can quickly become unmanageable to compute using simple pen and paper for any nontrivial case, hence the need for algorithmic descriptions. Previous work identified the class of piecewise affine functions which are ultimately pseudo-periodic (UPP) as being closed under the main NC operations and able to be described finitely. Algorithms that embody NC operations taking as operands UPP curves have been defined and proved correct, thus enabling software implementations of these operations. However, recent advancements in NC make use of operations, namely the lower pseudo-inverse, upper pseudo-inverse, and composition, that are well defined from an algebraic standpoint, but whose algorithmic aspects have not been addressed yet. In this paper, we introduce algorithms for the above operations when operands are UPP curves, thus extending the available algorithmic toolbox for NC. We discuss the algorithmic properties of these operations, providing formal proofs of correctness.
Network Calculus (NC) is an algebraic theory that represents traffic and service guarantees as curves in a Cartesian plane, in order to compute performance guarantees for flows traversing a network. NC uses transformation operations, e.g., min-plus convolution of two curves, to model how the traffic profile changes with the traversal of network nodes. Such operations, while mathematically well-defined, can quickly become unmanageable to compute using simple pen and paper for any non-trivial case, hence the need for algorithmic descriptions. Previous work identified the class of piecewise affine functions which are ultimately pseudo-periodic (UPP) as being closed under the main NC operations and able to be described finitely. Algorithms that embody NC operations taking as operands UPP curves have been defined and proved correct, thus enabling software implementations of these operations. However, recent advancements in NC make use of operations, namely the lower pseudo-inverse, upper pseudo-inverse, and composition, that are well defined from an algebraic standpoint, but whose algorithmic aspects have not been addressed yet. In this paper, we introduce algorithms for the above operations when operands are UPP curves, thus extending the available algorithmic toolbox for NC. We discuss the algorithmic properties of these operations, providing formal proofs of correctness.
This paper describes Nancy, a Network Calculus (NC) library that allows users to perform complex min-plus and max-plus algebra operations efficiently. To the best of our knowledge, Nancy is the only open-source library that implements operators working on arbitrary piecewise-linear functions (as opposed to only concave/convex ones), as well as to implement some of them (e.g. sub-additive closure and function composition). Nancy allows researchers to compute NC results using a straightforward syntax, which matches the algebraic one. Moreover, it is designed having computational efficiency in mind: it exploits clever data representation, it uses inheritance to allow for faster algorithms when they are available (e.g., for specific subclasses of functions), and it is natively parallel, thus reaping the benefit of multicore hardware. This makes it usable to solve NC problems which were previously considered beyond the realm of tractable.
Multi-access Edge Computing (MEC) will enable context-aware services for users of mobile 4G/5G networks. MEC application developers need tools to aid the design and the performance evaluation of their apps. During the early stages of deployment, they should be able to evaluate the performance impact of design choices - e.g., what round-trip delay can be expected due to the interplay of computation, communication and service consumption. When a prototype of the app exists, it needs to be tested it live, under controllable conditions, to measure key performance indicators. In this paper, we present an open-source framework that allows developers to do all the above. Our framework is based on Simu5G, the OMNeT++-based simulator of 5G (NewRadio) and 4G (LTE) mobile networks. It includes models of MEC entities (i.e., MEC orchestrator, MEC host, etc.) and provides a standard-compliant RESTful interface towards application endpoints. Moreover, it can interface with external applications, and can also run in real time. Therefore, one can use it as a cradle to run a MEC app live, having underneath both 4G/5G data packet transport and MEC services based on information generated by the underlying emulated radio access network. We describe our framework and present a use-case of an emulated MEC-enabled 5G scenario.

Lab head

Giovanni Stea
Department
  • Department of Information Engineering
About Giovanni Stea
  • The main research area of Giovanni Stea is network Quality of Service (scheduling, performance evaluation via simulation and Network Calculus, MEC, Wireless Networks and 4G/5G cellular). In the above fields he coauthored 100+ works and 16 patents. He is an editor for Wireless Networks, a member of the steering committee of VALUETOOLS, and he has been General Chair and Program Chair for international conferences. He has given keynote speeches in international venues. He is a fellow of the EAI.

Members (10)

Giuseppe Anastasi
  • Università di Pisa
Enzo Mingozzi
  • Università di Pisa
Carlo Vallati
  • Università di Pisa
Antonio Virdis
  • Università di Pisa
Giovanni Nardini
  • Università di Pisa
Carlo Puliafito
  • Università di Pisa
Francesca Righetti
  • Università di Pisa
Raffaele Zippo
  • Università di Pisa
Alessandro Noferi
Alessandro Noferi
  • Not confirmed yet
Giuseppe Lettieri
Giuseppe Lettieri
  • Not confirmed yet
alessio vecchio
alessio vecchio
  • Not confirmed yet
Martina Pappalardo
Martina Pappalardo
  • Not confirmed yet

Alumni (5)