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A Survey on Network Resiliency Methodologies
against Weather-based Disruptions
Massimo Tornatore ∗, Joao Andr´
exiii , P´
eter Babarczi ¶, Torsten Braun ∗∗, Eirik Følstad ‡‡,
Poul Heegaard ‡‡, Ali Hmaity ∗, Marija Furdek §, Luisa Jorge ‡, Wojciech Kmiecik xii ,
Carmen Mas Machuca x, Lucia Martins xiv , Carmo Medeiros xiv, Francesco Musumeci ∗,
Alija Paˇ
si´
c¶, Jacek Rakk, Steven Simpson xi, Rui Travanca ††, Artemios Voyiatzis †
∗Politecnico di Milano, Department of Electronics, Information and Bioengineering, Milan, Italy
‡Instituto Polit´
ecnico de Braganc¸a and INESC Coimbra, Braganc¸a, Portugal
§KTH Royal Institute of Technology, Stockholm, Sweden
¶MTA-BME Future Internet Research Group, Budapest University of Technology and Economics (BME), Hungary
kGdansk University of Technology, Faculty of Electronics, Telecommunications and Informatics, Poland
∗∗ University of Bern, Switzerland, †SBA Research, Vienna, Austria
†† Dept. of Civil Engineering, Universidade de Aveiro, 3810-193 Aveiro, Portugal
‡‡ Norwegian University Of Science and Technology, Trondheim, Norway
xTechnical University Munich, Germany, xi Lancaster University, United Kingdom
xii Wroclaw University of Technology, Poland
xiii National Laboratory for Civil Engineering (LNEC), Lisbon, Portugal
xiv Dept. of Electrical and Computer Engineering & INESC, University of Coimbra, Coimbra, Portugal
E-mail: massimo.tornatore@polimi.it,jandre@lnec.pt,babarczi@tmit.bme.hu,braun@inf.unibe.ch,eirik.folstad@item.ntnu.no,
poul.heegaard@item.ntnu.no,ali.hmaity@polimi.it,marifur@kth.se,ljorge@ipb.pt,wojciech.kmiecik@pwr.edu.pl,
cmas@tum.de,cmedeiros@deec.uc.pt,lucia@deec.uc.pt,pasic@tmit.bme.hu,francesco.musumeci@polimi.it,
jrak@pg.gda.pl,s.simpson@lancaster.ac.uk,rui.travanca@ua.pt,avoyiatzis@sba-research.org
Abstract—Due to the increasing dependence on network ser-
vices of our society, research has recently been concentrating on
enhancing traditional protection strategies to withstand large-
scale failures, as in case of disaster events. The recently-formed
EU-funded RECODIS project aims at coordinating and fostering
research collaboration in Europe on disaster resiliency in com-
munication networks. In particular, the Working Group (WG) 2
of the RECODIS project focuses on developing new network-
resiliency strategies to survive weather-based disruptions. As
a first step, WG2 members have conducted a comprehensive
literature survey on existing studies on this topic. This paper
classifies and summarizes the most relevant studies collected
by WG2 members in this first phase of the project. While the
majority of studies regarding weather-based disruptions deals
with wireless network (as wireless channel is directly affected
by weather conditions), in this survey we cover also disaster-
resiliency approaches designed for wired network if they leverage
network reconfiguration based on disaster “alerts”, considering
that many weather-based disruptions grant an “alert” thanks to
weather forecast.
Index Terms—weather-based disruptions; disaster resilient
communications; network resilience; disasters; failures;
I. INTRODUCTION
This paper is intended to provide a survey of existing studies
on network resiliency against weather-based disruptions. Spe-
cific weather conditions (e.g., heavy rain fall, extreme winds,
fog) can lead to partial degradation of network performance
characteristics, e.g., the capacity of wireless links can de-
crease significantly due to signal attenuation in the presence
of heavy rain [1]. On a larger scale, other more-impacting
weather condition (e.g.,weather-based disasters as hurricanes,
or tornadoes) can cause very extensive network disruptions
(consider, e.g., the extent of damage caused by the hurricane
Katrina in New Orleans in 2005 [2]).
Partial degradations usually last for limited time periods,
typically shorter than in the case of extensive disaster failures.
Yet, these relatively short time periods of disruption (measured
in minutes or hours) can be very significant for critical infras-
tructures, especially nowadays that several crucial activities
of our society rely on telecom-network services. Problems
considered by existing literature on weather-based network-
performance degradation are mostly related to access networks
(local and metropolitan) and wireless technologies, which
still form an important part of the global communications
infrastructure.
As for more extensive weather-based failures (e.g., hurri-
canes, or tornadoes), the large geographical footprint of such
failures makes them relevant also for wired networks and
as well as in the core segment of the network. In these
cases, it is important to develop the mechanisms of network
preparedness to incoming catastrophic weather conditions,
e.g., by reconfiguring network topologies in advance. It is
important noting here that one of the main difference between
resiliency techniques against natural and man-made disasters
(e.g., earthquakes, terrorist attacks, as those studied in the
WG1 of the RECODIS project) and weather-based disasters
is the fact that, with good probability, changing weather
conditions are announced by weather forecast and that grants
to network operators some time to reconfigure the network
before the disaster strikes (consider, e.g., hurricane forecasts).
In the rest of the paper we will refer to this granted interval
of time as “alert”.
While disaster-resilient planning strategies, as the one stud-
ied in WG1, ensure that the network is designed with min-
imum disaster risks based, e.g., on disaster probabilities, we
consider in this survey studies where the probability of an
incoming weather disruption can be extremely time-varying. In
response to an upcoming disaster alert, such a reconfiguration
might need to be performed in a very limited time scale,
ranging from minutes to hours depending on the type of alert.
The COST CA15127 RECODIS Action will develop ap-
propriate solutions to provide cost-efficient resilient commu-
nications in the presence of disaster-based disruptions, con-
sidering both existing and emerging communication network
architectures. As a first step towards achieving the goals of
RECODIS, and within the context of the activities of Working
Group 2, a survey of strategies for communication networks
to protect against weather-based disruption is presented here.
For reader’s convenience, we summarize the proposed contri-
butions, divided per aerea, in Tab. I.
The survey is organized as follows. Section II overviews
studies on the modeling of weather-based disruptions on
telecom networks. In Section III weather-based resiliency
studies in wireless networks are discussed, while in Section
IV we present alert-based resiliency studies applicable in
wired networks against weather-based disruptions. Section V
focuses on the emerging trend of weather-based resiliency in
converged networks. In Section VI, the role of more advanced
network paradigms, as delay tolerant networking, is discussed.
Finally, we conclude our survey in Section VII.
II. MO DE LI NG THE EFF EC T OF W EATHER-BA SE D
DISRUPTIONS ON TELECOM NETWORKS
A. Modeling infrastructure disruption
In building disaster models such as a spatial-temporal
model described in [3], we need to understand how undesired
events occur, how they are correlated, move/propagate, and
cascade. The observations made and lesson learnt from major
infrastructure disruption are used as a basis for such mod-
els. Two examples are the increased knowledge of disaster
impact on the telecommunications power infrastructure from
the Hurricane Katrina [5] and Great East Japan Earthquake
[2], and recovery from these disasters. An on-site survey from
the Hurricane Katrina conducted in October 2005 addressed
the effects, failure modes, causes, and duration, which are
included a fault tree analysis (FTA), and a summary table of
the main failure causes and restoration strategies in the wired
TABLE I
SUMMARY OF THE PROPOSED CONTRIBUTIONS PER AREA
Contributions References
Modeling weather-based
disruptions on telecom
networks
Modeling infrastructure
disruption
[3] [2] [4] [5]
[6] [7] [8] [9]
Effect on
wireless channel quality
[1] [10]
[11] [12]
Impact of
structural design
[13] [14] [15]
[16] [17]
Weather-based
resiliency studies
in wireless
networks
Protection
strategies
[18] [19] [20]
[21] [22] [23]
Optimization
and
survivability
models
Wireless
Mesh
Networks
[24] [25] [26]
Free
Space
Optics
[27] [8]
Alert-based weather-based
resiliency in wired
networks
Network
connectivity
[28] [29] [30]
[31] [32] [33]
[34] [35] [36]
Cloud networks [37] [38] [39]
[40] [41] [42]
Advanced topics in
weather-based
resiliency
Converged
networks
[43] [44] [45]
[46] [47] [48]
Advanced technologies
(DTN, ICN)
[49] [50] [51]
[52]
and wireless communication networks [5]. In [2] a detailed
description is given of the damages of the earthquake (main
shock and aftershock) and the following tsunami, including
how the number of power outages affecting the telecom
buildings changes over time after the main shock. Also during
Hurricane Ike (strongest hurricane in 2008 - Galveston, Texas,
September 13, 2008), the reachability of subnets was evaluated
through data related with Border Gateway Protocol (BGP)
update messages from subnets in Texas area during Septem-
ber 10-20. The time correlation between the reachability of
the network and the overlapping of the storm coverage and
the subnet locations (which are known only approximately)
was analysed. Some subnets became unreachable before the
hurricane reached any subnet region. Power outage and lack
of spare power were found as being the most important
causes to justify the low correlation obtained [4]. Similar other
investigations exist for other weather-based disasters as in [6],
[7]. Models of disaster effects on network infrastructures can
be used for network survivability quantification. In [8] it is
shown a scalable approach using a Markov model approach
to describe the transient effects on network performance of an
undesired event, until the network is restored to an operational
state, and then until it has completely recovered. This is
compliant with the survivability quantification definition of
ANSI-T1A1.2 given in [9].
B. Effect on wireless channel quality
As wireless networks operation can be heavily affected
by weather conditions, in these last years different modeling
studies have tried to capture the effect of weather condition on
wireless channel quality. In [10], authors focus on the impact
of fading from weather conditions on Free Space Optical
(FSO) systems and propose a new technique to mitigate the
negative influence of atmospheric effects. Various systems
were compared with the Multiple Input Single Output (MISO)
multi-hop Decode and Forward (DF) relay FSO system using
M-array Pulse Amplitude Modulation (M-PAM), concluding
that multi-hop system based PAM modulation have superior
performance, especially when increasing the number of
relays. Authors in [11] investigate the dynamic property
of a tropical-forested channel due to the weather effect on
Very High Frequency (VHF) and Ultra High Frequency
(UHF) radio-wave propagation. The main idea is to design
a fade margin for VHF/UHF communication system in a
tropical environment. The experimental results indicate that
the wind and the rain can impose an additional attenuation
on the propagation signal within critical environment.
Authors modeled the temporal fading components due to the
weather and draw a specific statistical fading model. Further
analysis is made on the effect of the Rician Kfactor and
the intensity of wind and rain. On the other hand, Wireless
Sensor Networks (WSN) integrate functions of sensing,
computation and communication to monitor a wide range of
environmental parameters. In [1] authors study the effect of
temperature and humidity on radio signal strength in outdoor
WSNs. Experimental measurements were performed using
Atmel ZigBit 2.4 GHz wireless modules, both in summer
and wintertime and testing over all the channels specified
by IEEE 802.15.4 for 2.4 GHz ISM frequency band with
two power levels. Their finding suggest that temperature has
negative, linear effect on signal strength in general, while high
relative humidity may have some effect, particularly when
temperature is below 0◦C. They also show that frequency
diversity can alleviate the effects of channel-specific variation.
Such finding can be useful for designing algorithms and
protocols which are adaptive and robust against the effects
of weather variation. Ref. [12] proposes a scheme to reduce
the influence of weather conditions for hybrid WSN when
hybrid WSN having both Radio Frequency (RF) and Free
Space Optics (FSO) links for communication. The main idea
is use multiple thresholds to activate transmission of RF and
switch from RF to FSO and vice-versa. The experimental
results under fog, snow and rain events show that the power
consumption saving of RF transmission can be reduced
significantly, and that the network lifetime in harsh terrestrial
environment is doubled with respect to the case of RF links
transmissions only.
C. Ensuring wireless channel quality by structural design
In a typical cellular network, wireless transmission equip-
ment, i.e., mostly the antennas (possibly co-located with some
baseband-processing hardware), can be placed in various loca-
tions and supporting structures. Figure 1 shows two possible
supporting structures: a monopole and a lattice tower. In both
cases, the structure is subject to significant deflections and
rotations that affect the wireless channel quality. So, consid-
erations regarding structural design need to be discussed.
Standards are a very important part of engineering practices,
serving as rules that engineers must comply. Structural design
Fig. 1. Antennas mounted on a lattice tower (on the left), antennas mounted
on a monopole (on the right).
standards are typically aimed at ensuring the proper structural
safety of the physical infrastructure hosting the antenna within
the range of diverse hazards that it will be exposed to. While
the prevention of collapse is of primary importance, the real
purpose of communication structures is to transmit signals,
regardless of the weather conditions. However, this primary
purpose cannot be achieved if the flexibility of the structure
is such that deflections and rotations at the points of support
of the antennas exceed permissible values. The main concern
for the network operator is not exceeding the permissible
values, but instead the time during which such permissible
value is exceeded. In the case of communications structures,
the so called “serviceability limit state” is generally defined
as the state that will cause an unacceptable reduction in the
level of service provided by the antenna system mounted
on the structure, i.e., the serviceability limit state is reached
when the signal level is reduced below an acceptable limit
by loss of alignment caused by twisting or tilting of the
antenna. The concept of unacceptable signal, resulting in
“outage”, is extremely complex, potentially being influenced
by the sensitivity of the electronic equipment and its ability
to recover after momentary excessive structural deflection in
a short duration gust. Thus, not only the wind speeds, and the
associated gusts, are important, but also the performance of
the electronic equipment [14]. Other weather conditions, e.g.
rain or icing, may also affect the signal performance. In the
structural design, many aspects are frequently ignored when
estimating deflections of antennas using numerical simulation,
e.g., soil-structure interaction, deflection of antenna mounting
system, a more refined mass distribution and/or stiffness loss.
Such aspects should not be overlooked [15], [16].
Most standards provide guidance to determine the relevant
deflections, rotations, or the duration curve to be used to
determine time that the wind speed is exceed. The American
and Australian standards provides specific limits to allowable
deflections and rotations, but for the United Kingdom and
Canadian standards, it would be up to the network operator to
assess if such outage durations were acceptable. The Eurocode
provides no guidance on limits for communication structures,
but gives guidance to the network operator on what parameters
need to be considered when setting his specifications or design
criteria. However, with the current economic environment and
market pressure, many of these structures are ordered by
clients whose knowledge of the structural requirements is
relatively limited [14], [17]. This is possibly motivated by
the relatively low cost of the structure compared with that of
the network equipment it supports, thereby concentrating the
attention of the network operator on the overall cost. On the
other hand, it can also be argued that a relatively small invest-
ment in a properly designed supporting structure would not
increase significantly the overall cost [14]. The high number
of failures observed in structures used as support of cellular
antennas motivates the need to treat their design, fabrication,
construction and maintenance extremely carefully [14], [13],
[17], [16]. The continuous evolution in the constructional field,
e.g., with the increasing strength of the materials used and
the new structural forms adopted, emphasizes the increasing
difficulty of a proper evaluation of the actions and effects
of wind on more slender and lightweight structures, such as
monopoles. As a static problem, i.e., a cantilever beam with
one or more concentrated masses, is probably the simplest
in the structural field. However, a deeper investigation on
monopoles reveals a completely different scenario, i.e., under
wind action they are subject to complex dynamic effects giving
rise to potentially unstable conditions [16]. Also, the conse-
quences in the codification sector are evident, i.e., specific
standards exist but based on empirical calculation criteria that
need to be reviewed and updated. The frequent abnormal
vibrations as well as some failures observed in these structures
confirm the need for a better understanding of wind-excited
behaviour [13], [16].
The business response is to keep expenditure to a mini-
mum and increase revenues. Mainly due to market pressures,
investments are short-term intended, focusing on replacing
and renewing as needed rather than modernising key physical
infrastructure, and expenditure takes place in response to
a crisis rather than proactively planning and managing key
physical infrastructures. Also, the focus is on operating at
near maximum operational capacity of the physical infras-
tructure which is viewed as being an optimal and efficient
management decision. This, however, causes the systems to
be less resilient against anticipated or unknown climatic and
socio-demographic changes during the infrastructures lifespan.
In conclusion, to properly plan and manage key physical
infrastructures it is necessary to gather a correct understanding
of the structural behaviour of such structures. Therefore, there
is an urgent need to apply advanced research methods, e.g.,
structural health monitoring, experimental testing and numer-
ical simulation, and develop a comprehensive risk framework
to elaborate new, and review existing, design guidelines, which
will contribute to overcome the existing weaknesses.
III. RESILIENCY AGAINST WEATHE R-BAS ED D IS RU PT IO NS
IN WI RE LE SS N ETWORKS
Wireless technologies play a key role in today’s network in-
frastructures. Originally intended mostly as a support technol-
ogy for the last mile, they are becoming promising alternative
to wired metro networks, due to the long-term planning, high
capital expenditures (CAPEX) and operating expenses (OPEX)
required by wired (mostly fiber-based) network deployments
in metro ares. Wireless networks are relatively fast and cheap
to deploy and can work in several topological shapes (ring,
star, mesh ect.). Often, when planning a robust and survivable
wireless network, mesh networks are considered to be the
most reliable solution. However, due to the nature of wireless
communications, wireless links are very susceptible to weather
disruption and this section aims at providing a survey of
the main challenges that weather-based disruption poses to
wireless networks.
Several technologies have to be considered when planning
a wireless network. These include:
•Millimeter-wave (MW) technology, which can achieve
transmission rates of 1-10Gbps per a millimeter-wave link
(utilizing the 71-86GHz band) [19]. Note that compared
to lower bands, radio waves in this band have high
atmospheric attenuation. Therefore, this band is better
suited for very short range (1-2 kilometer) point-to-point
and point-to-multipoint applications.
•FSO (Free Space Optics), a technology that uses light
propagating in free space for wireless data transmission.
Most of the manufacturers use the wavelengths between
800 and 1550nm (preferred) [24]. FSO links may carry
from 10Mbps to 10Gbps, up to 3km distance. The optical
beam is highly attenuated by fog and other airborne
particles.
•Microwave technologies (3-30GHz) can achieve trans-
mission rates up to 3Gbps with large coverage distance
and are not so vulnerable to precipitation (especially
under 10GHz). For instance WIMAX (Worldwide In-
teroperability for Microwave Access), which works at
data rates of 300Mbps to 1Gbps, can provide a coverage
distance up to 30km under Line Of Sight (LOS) situations
and a typical cell range of up to 8km under No LOS
(NLOS) [53].
•Mobile technologies (GSM, UMTS, LTE ect.) utilize
lower bands, i.e., from 225MHz to 3700MHZ and provide
date rates up to 300Mbps. Note that, these networks are
distributed over land areas called cells. The size of these
cells varies from 10m (femtocells) to 20km (macrocells).
The precipitation susceptibility is not significant.
A. Protection Strategies
1) Wireless Mesh Network (WMN): A wireless mesh net-
work (WMN) is a communications network made up of radio
nodes organized in a mesh topology and has been subject of
extensive research. Early papers on wireless survivability fo-
cused only on connectivity of a network topology as a measure
of fault tolerance in wireless mesh network. As connectivity
turned out to be a mostly qualitative measure (not suite for
carrier-grade applications), more precise measurements related
to signal attenuation and partial link failures gained attention in
later studies. Note that WMNs often use routing metrics based
Fig. 2. Example of radar echo rain maps (Ireland, November 26-27, 2011)
on Expected Transmission count (ETX), a metric depending
on the quality of the link. This metric (i.e. ETX) can be
helpful when improving reliability in case of bad link states
by weather impact.
When considering weather-based disruptions, two main pro-
tection strategies have to be considered (this will be discussed
in details below):
•One option is to periodically update the network topol-
ogy [19], [20].
•The second is to introduce rain-related link states to
improve the routing mechanism [21], [18]. The rain-
related link state can be either adjusted according to
locally measured data (for example Bit Error Rate) or
from externally measured information (e.g., radar data).
Impact of weather-based disruptions on performance of
high-frequency communications in WMNs operating in 71-
86 GHz band is addressed in [19] and [20]. In particular,
these papers focus on the influence of heavy rain falls on
the degradation of the effective capacity of WMN links. As
shown in these papers, the nominal capacity of WMN links
(commonly 1-10 Gbps) utilizing the 71-86 GHz band can be
remarkably impacted by even moderate rain falls. To provide
a proper solution to this problem, [19] introduces a scheme of
proactive preparedness of a WMN network to incoming rain
falls by means of periodic updates of a WMN topology in
advance based on information on incoming rain falls (derived
from radar echo rain maps like Figure 2). In particular, the
algorithm of WMN topology reconfiguration is proposed to de-
termine links of predicted low signal attenuation that should be
present in the updated topology, as well as those transmitting
information over heavy rain areas (which should be deleted).
This technique provides a significant improvement in terms
of reduction of the impact of rain on signal attenuation along
communication paths. Technique of periodic reconfiguration
of a WMN topology from [19] can be easily implemented,
since it does not involve any updates of routing algorithms.
Ref. [20] is an extended version of [19]. In particular, [20]
additionally presents the ILP model of weather-resistant links
formation problem as well as the proof of its NP-completeness.
Unlike the proposal from [19] and [20], two other tech-
niques (called XL-OSPF and P-WARP [22], [21]) to improve
performance of WMNs under weather-based disruptions rely
on further enhancements of routing algorithms. In particular,
routing in XL-OSPF is done based on a link-cost metric
proportional to the observed bit error rate (BER) of WMN
links. Instead, link costs of P-WARP (also used in routing)
are estimated based on radar information concerning predicted
weather conditions. An analysis of the impact of rain storms
on MW links and a performance comparison of the two
new routing protocols (i.e. XL-OSPF and P-WARP) that use
physical-layer information to improve routing at the network
level is provided in these papers. The detailed examination of
several observed storms shows that most of the times, while a
small number of links is severely degraded, a large set of links
may be just slightly degraded or unaffected, which motivates
the need of domain-specific routing protocols to use lower
layer information to improve routing decisions. Both protocols
demonstrate some improvement over OSPF during real rain
events modelled in simulation.
In [18], authors propose a Predictive Wireless Mesh Net-
work Routing (PWMNR) protocol which makes routing de-
cisions using only information from the wireless link rather
than from outside information regarding weather events (e.g.
radar information). Note that in PWMNR each node monitors
the link BER of all the links with its neighbors and uses
an appropriate statistical model to predict the link BERs for
certain specified time intervals into the future (unlike the XL-
OSPF, where no prediction occurs). The authors present the
operational protocol details as well as the implementation of
a protocol simulator enabling simulation based on data from
real weather events. Finally, they also present a performance
comparison with other approaches, including conventional
routing protocols (static routing and standard OSPF) as well as
link-state-based routing (link-cost OSPF). No comparison to
explicitly weather-information-based routing protocols (either
reactive or predictive) is provided (although link-cost OSPF
as implemented could be similar to XL-OSPF). As a result,
without using any sort of weather observation or prediction,
PWMNR achieves a throughput performance up to 8% higher
than link-quality-based routing that also does not use predic-
tion.
The authors in [23] consider solar powered base stations
(BS) as an alternative to the absence of power grid in rural
areas or at the occurrence of power outage in disaster-stricken
areas. However, it is hard to cope with the dependence of the
amount and rate of energy available over time. The authors
propose a wireless mesh network exploiting solar energy
harvesting BS. The aim is at providing reliable communication
network to offer stable communication applications through
the energy variation over time. The authors had some field
experiments and gave some hints on toward possible perfor-
mance improvement of WMNs via BS synchronization with
changing link states.
2) Free Space Optics (FSO): As mentioned before, FSO
(Free Space Optics) is another promising alternative for creat-
ing WMNs. Ref. [24] presents an overview of FSO commu-
nications technology enabling high-bandwidth optical wireless
transmission between stationary nodes. Characteristics of FSO
technology are described with special focus on signal atten-
uation, scattering, scintillation (additional attenuation on the
laser beam caused by atmospheric temperature and pressure
variations), alignment, and full duplex transmission. The paper
also points out disadvantages of FSO related to point-to-
point transmission, implying e.g., that each transceiver requires
accurate initial alignment as well as selftracking to preserve
the proper alignment for instance during strong winds. It also
highlights challenges leading to degradation of the effective
capacity of FSO links, in particular related to the influence
of fog, smoke, wind, sand, or heavy rain. Ref. [25] compares
different FSO networks that have been implemented in Graz
(Austria) and Nice (France). Although any common optical
wavelength could be initially used, most of the systems use
1550nm wavelength. In this work two systems are compared:
100m and 300m range. The two systems have one receiver
(photo-PIN-diode) but the 100m has one transmitter (LED -
Light-Emitting Diode) whereas the 300m has 8 transmitters
(LED). When replacing LEDs by Vertical-Cavity Surface-
Emitting Lasers (VCSELs), the reach can be increased to
800m. These network elements can be used in different
types of FSO networks, mainly using rings, star or mesh
topologies. The best solution for FSO configurations will be
a meshed network (unsurprisingly). This architecture com-
bines shorter distances and high reliability, because of the
location of the Optical Multipoint Unit. The combination
of FSO and microwave-links is also a possible solution for
increasing reliability and availability, because terrestrial FSO
is most affected by fog, whereas the microwave propagation is
mainly influenced by rain. These networks are called Hybrid
RF/FSO Networks. In [26], authors investigate the reliability
of such networks. Note that FSO links have a much higher
link capacity (20-25 times of a RF link), however, they are
much more vulnerable, especially to bad weather (fog, snow).
Hybrid RF/FSO networks combine the merits of FSO and
RF technologies by providing parallel transmission via RF
and FSO links. This means that if the FSO link fails, the
RF link transmits the critical data (high-priority traffic), while
the non-critical data has to be rerouted in the FSO domain,
if possible. To ensure the proper differentiation of recovery
actions after FSO link failures, several traffic criticality classes
have to be introduced. In particular, in [26], the weather-based
disruption of FSO links is addressed by taking into account
weather predictions and how they influence quality of FSO
link existence. Note that, until now the routing and network
resource allocation was determined offline, periodically. Upon
failure of an FSO link, redirection of traffic in the FSO domain
was considered (i.e., low-priority traffic not protected by the
corresponding RF backup link), but 100% restoration was not
guaranteed. In [26] a new routing metric (cost) was defined
based on weather forecasts, in order to establish obscuration-
tolerant paths in the FSO domain. The scheme is based on link-
disjoint FSO paths providing preplanned protection in case of
FSO link failures. This routing problem was proven to be NP-
hard, which is why an Integer Linear program and a heuristic
algorithm has been proposed.
B. Optimization and survivability models
In recent years, several useful general optimization mod-
els for survivability in WMNs were introduced. In [27],
an original optimization model is presented for the Flow-
Thinning Problem (FTP), formulated as non-compact linear
programming problem. A resolution method based on a path
generation approach is also presented. FTP is inspired by
diversity path strategy and elastic rerouting, previously pro-
posed, and therefore each demand may be routed through an
over-dimensioned set of paths, not necessarily disjoint, and
only a fraction of the flows traversing the affected links are
saved. Some encouraging numerical results were presented
comparing FTP with the global rerouting strategy, a strategy
that restores flows from scratch in surviving capacity, but the
authors concluded that further studies need to be carried out to
evaluate the applicability of this approach. The optimization
model proposed is suitable for broadband wireless networks
with non-interfering point-to-point links.
Another interesting approach was introduced in [8]. The
authors present survivability and network performance models
(including a phased recovery model of rerouting and restora-
tion) to study network survivability. The modeling approaches
are applied to both small and real-sized network examples.
Three different scenarios have been defined, including single
link failure, hurricane disaster, and instabilities in a large block
of the system (transient common failure). To avoid state space
explosion while addressing large networks, the models are
decomposed in space by studying the nodes independently, and
in time by decoupling the analytic performance and recovery
models, giving a closed form solution. The main purpose
of the approximations proposed in the paper is to reduce
the computational effort of obtaining transient solutions in
large network models without an undue loss in the accuracy
(under a set of assumptions described). Network survivability
is quantified in terms of performance metrics like packet loss
probability and the delay distribution of non-lost packets.
The results provided show good correspondence between the
transient loss and delay performance in the simulation and
analytic approximations.
IV. ALE RT-BAS ED RECONFIGURATION AGAINST
WEATH ER -BA SE D DI SRUP TI ON S IN WIRED NETWORKS
Large-scale weather-based disruptions (e.g., hurricanes,
floods) are expected to be more frequent in future due to global
warming. The affected areas in case of such destructive events
might also affect wired networks, e.g., Wide Area Networks
(WANs). In the following, as explained in the introduction,
we concentrate on disaster-resiliency techniques based on the
concept of “alert”, to avoid overlaps with RECODIS WG1, and
we classify the surveyed approaches in techniques focused on
ensuring network connectivity vs. techniques focused on cloud
networks (where the role of datacentres is crucial).
A. Alert-based Reconfiguration of Network Connectivity
By modeling possible disasters (e.g., using hazard maps),
their likelihood and the severity of their consequences, three
degrees of preparedness (including the post-disaster actions)
to a weather-based disruption can be obtained [28]. Normal
preparedness entails utilizing knowledge of risky regions to
pro-actively allocate network resources so that the network
disruption and data losses are minimized. Although traditional
protection approaches provide 100%deterministic recovery
from single link failures, multiple correlated failures caused
either by the primary or the cascading effects of weather-
based disruptions might require unsustainable amount of
backup resources to provide full protection. Thus, a promis-
ing strategy may focus on providing full-disaster protection
for mission-critical services and degraded service to other
applications [29]. Note that, some services are sensitive to
the amount of capacity provided, while others (e.g., video
streaming or file transfers) can operate with reduced band-
width and can still achieve lower but acceptable quality. As
available resources decrease dramatically during large-scale
disasters, the approach of degraded-service tolerance [29] can
reduce protection cost, reduce network disruption, and support
maximal carried traffic.
Instead of pro-actively design (costly) recovery from ran-
dom geographic failures [30], with alert-based reconfiguration
of the network the risk of disruptions can be minimized
in a cost-efficient manner by re-allocating critical network
resources when an alarm is issued, called enhanced prepared-
ness [28]. Luckily, current networking trends give excellent
support for the alert-based reconfiguration of wired networks
in order to maintain network connectivity. One of these trends
is Software-Defined Networking (SDN), which facilitates net-
work reconfigurability and programmability and opens up new
ways to reconfigure the network in reaction to a disaster alert
by centralizing control logic and separating it from the physi-
cal equipment. Another trend is network virtualization, which
enables multiple tenants to share the same underlying SDN
infrastructure to improve its resource efficiency. For this, each
tenant contracts a Service Level Agreement (SLA) with the
physical SDN infrastructure provider, which declares minimal
QoS requirements for its virtual topology. The responsibility
of the provider is to embed the tenants’ virtual topology
into the physical topology satisfying these requirements [31].
Therefore, in order to satisfy the required resilience declared
in the SLA, virtual networks might be migrated [32] from
the current physical resources to new ones as part of the alert-
based reconfiguration. Migration of virtual SDN networks (i.e.,
rearrangement of the existing flow configuration) boils down
to the task of removing old forwarding rules from the switches
and installing the new forwarding rules corresponding to the
desired (e.g., failure safe) flow configuration. However, the
failure of the control channel or the asynchrony of switch
updates might cause performance degradation, state inconsis-
tency and temporal over-utilization of the links, which have to
be considered when an alert-based reconfiguration is initiated.
Another related trend is Network Function Virtualization
(NFV) that can also potentially allow significant flexibility and
network programmability so as to react and respond fast to a
generic unpredicted network disruption (either weather-based
or others). An example of industrial research project heading
towards this direction is described in [33], where authors
develop novel testing tools (e.g., fault injection technologies)
and systematic guidelines to help telecom operators to eval-
uate the reliability of their NFV-capable infrastructure. The
authors focus on virtual machines, cloud management stacks,
and hypervisors and investigate the risks for NFV reliability
inherently associated to the adoption of virtualization.
In the remainder of this subsection, we notice that some
alert-based reconfiguration approaches concetrate on data
plane survivability while others on control plane survivability.
In order to ensure data plane survivability, when a hurricane
or tornado alert is issued we need to calculate a virtual SDN
embedding which is disjoint from the predicted disaster area.
Thus, given the original embedding of the virtual network and
the desired disaster-aware embedding, we need to migrate the
virtual nodes and links onto the new physical resources [32].
As part of this, we have to remove the old and install the new
forwarding rules in the switches. If the state of the virtual
nodes have to be migrated as well, the time of the migration
would depend on the memory size and (inverse proportionally)
on the available bandwidth along the links between its old
and new location. In this scenario a deadline T(depending on
the alert) might be added to the optimization problem, before
which the whole migration process must reach its desired state
(e.g., before the hurricane reaches the mainland or the tornado
hits the ground).
In order to preserve network connectivity, also the control
plane of the network requires to be disaster resilient, especially
in a scenario where a reaction to an alert is required and
therefore quick network reconfiguration is needed [34]. Hence,
in an alert-based control plane design we have to avoid that
switches getting disconnected from the control logic or the
network falls into several connected islands upon a controller
failure [34]. Several distributed SDN controller architectures
have been proposed to mitigate the risks of overload and
failure, but they are optimized for limited faults without
addressing the extent of large-scale disaster failures [35]. Thus,
in [34] the authors present a novel disaster-aware control-plane
design and mapping scheme, formally model this problem,
and demonstrate a significant reduction in the disruption of
controller-to-controller and switch-to-controller communica-
tion channels. While minimizing the resource usage, they also
consider inter-controller and switch-to-controller delay to be
able to respond to failures promptly. Further note that, if the
communication channel of a switch to the primary controller
fails, finding another operating controller upon disaster might
be slow or would not be feasible at all. Thus, multiple con-
trollers have to be assigned to each switch (i.e., a secondary,
tertiary, etc. controller to be contacted if the primary fails) [35]
in a resilient control plane design. Considering disasters in the
controller placement problem becomes especially important if
Fig. 3. After an alert is issued (red crircle), switches served by the affected
controller C1have to be assigned to their secondary controller (i.e., C2). The
virtual network embedded to switches S7−S5−S3have to be re-allocated
as well, including the migration of a virtual node (S3to S4) and two virtual
links (S3, S5)and (S3, S7).
the secondary controller might be responsible for controlling
a migrated virtual SDN, and, thus, it has different latency
constraints (to different physical locations of virtual nodes)
than the primary controller. An example is presented in Fig. 3
to demonstrate the required tasks.
Upon an alarm is issued and the reconfiguration process
is initiated, migrating flows from the old configuration to
their new location in one step would lead to temporal over-
utilization of links even if both the old and new configuration
of the flows were congestion-free, owing to the asynchrony
of forwarding rule updates at different switches. On the one
hand, one approach is to accept this temporal performance
degradation (i.e., congestion and packet loss) of the network
but trying to minimize its effect. However, such service
degradation is often unacceptable in production environments
like data centers and WANs. On the other hand, migrating
multiple flows at the same time in a provably congestion-free
manner without making any assumptions about the timing of
these updates at switches is a challenging problem and has
been thoroughly investigated. It was shown in [36] that instead
of performing forwarding rule update in a single step there
often exists a sequence of consistent network updates (i.e.,
congestion-free and without temporary demand reduction [29])
that deploys the desired flows in the network. A polynomial-
time algorithm was introduced in [36] to decide whether a
consistent sequence of forwarding rule updates (i.e., migration
plan) exists or not. However, if the flows are not allowed to
be split – flows have to be switched at once or in integer parts
from the current to their desired paths – then it is NP-hard to
decide whether such a migration plan exists or not.
Although the first steps were made to address these ques-
tions, alert-based reconfiguration against weather-based dis-
ruptions in software defined networking is a largely unexplored
research area.
B. Alert-based Reconfiguration in Cloud Networks
In cloud networks, a service request can be served by any
of the datacentres (DCs) which host the required content,
following the anycast communication paradigm. Under the
Infrastructure as a Service (IaaS) model, cloud service pro-
visioning comprises the selection of the most suitable DC
to handle a service request and the assignment of network
infrastructure to connect the source node of the request to the
selected DC. Targeted attacks and natural disasters can lead
to huge data loss and service disruptions in cloud networks.
Considering the important role of cloud services today, any
disruption of content/service, DC and network link failure
is a major concern and network operators are investigating
proactive and reactive measures to design disaster-resilient
networks. As weather disruptions tend to grant a certain
period of time in advance to the incoming disaster, a warning
time, in this section we survey research studies that try to
exploit such knowledge. In disaster-survivable IaaS clouds,
backup virtual machines (VMs) are employed in standby
mode, and are activated in a disaster. A disaster-resilient
IaaS cloud requires incorporating the knowledge of disaster
risks and consequences into the planning, modelling and
disaster recovery selection [37]. In the planning phase, the
possible risks are combined with resilience requirements and
constraints. The requirements are typically expressed as the
recovery time objective (RTO) and the recovery point objective
(RPO). The RTO accounts for the time needed to restore
a service, and it depends on the time needed to detect a
failure, restore the affected VMs from a backup site, restart all
the services running in these VMs, and redirect the network
traffic from the original site to the backup site. The RPO
refers to the data loss due to the time lapse between the
last backup of the service components (e.g., copy of virtual
disks) and the disaster [26]. When it comes to modelling, the
interplay between the available bandwidth between DC sites
and the offered RPO levels is still an open issue. The disaster
recovery mechanism selection focuses on disaster detection
mechanisms (e.g., periodical probing of DC sites, or using
alarms), VM recovery mechanisms (e.g., using VM snapshots),
and network reconfiguration mechanisms (typically relying on
anycast) [37]. A cloud resiliency approach that utilizes service
relocation and service differentiation for restoration of cloud
services after a single-link failure was proposed in [38]. The
paper leverages on the anycast nature of cloud services to
improve service restorability by relocation to a datacentre
with enough available IT (storage and processing) resources
when the shortage of network resources prohibits restoration
to the DC used by the failed working path. Moreover, applying
service differentiation can prioritize recovery of higher-class
services.
In [39], authors present novel techniques for disaster-aware
DC placement and content management in cloud networks
that can mitigate such loss by avoiding placement in given
disaster vulnerable locations. The problem is first solved as
a static disaster-aware DC and content placement problem by
adopting an integer linear program (ILP) with the objective
to minimize risk, defined as expected loss of content. Risk,
as defined by authors in this study, is a measure of how
much, in terms of cost or penalty, a network operator may
lose probabilistically due to possible disasters in a cloud
network. It is also shown how a service provider’s budget
constraint can affect disaster-aware placement design. Since
disaster scenarios, content popularity, and/or importance are
always changing in time (e.g., as a reaction to incoming alert
of a weather-related disruption), content placement should
rapidly adapt to these changes. Authors propose a disaster-
aware dynamic content-management algorithm that can adjust
the existing placement based on dynamic settings. Besides
reducing the overall risk and making the network disaster-
aware, reducing network resource usage and satisfying QoS
requirements can also be achieved by this approach. A cost
analysis of employing a dynamic disaster-aware placement
design in the network based on real-world cloud pricing. In
[40], the case of large-scale disasters, as a hurricane (refer
to the description of Hurricane Sandy in Section II), cloud
networks can suffer massive service disruptions and data loss.
To save critical data under such circumstances, contents could
be evacuated in response to an upcoming disaster alert from
a likely disaster region to a safe location before the disaster
occurs and causes serious data damage. Depending on the
forecasted disaster scenario, content evacuation can be greatly
constrained by limited available network resources and strict
deadlines (evacuation times). Hence, in [40], authors propose
a rapid-data-evacuation heuristic that selects the least-delay
paths (considering propagation delays, network bandwidth,
and congestion) through an anycast network model, and sched-
ules critical and vulnerable contents for evacuation such that
the maximum amount of contents can be evacuated within
the evacuation deadline or equivalently, a given amount of
contents can be evacuated in minimum time. The proposed
heuristic is compared with a nearest-evacuation approach,
which evacuates data only to the nearest DC using the shortest
path. Results show that, for typical scenarios considered in the
study, compared to nearest evacuation, the rapid-evacuation
approach provides about 64% time savings, or equivalently,
about 97% more volume of evacuated contents for a given
deadline. Since the algorithm is based on a greedy approach,
authors also present an enhanced rapid-data-evacuation algo-
rithm based on the simulated annealing metaheuristic as a
benchmark. It is shown that the proposed heuristic performs
very close to the simulated annealing based algorithm and is
much faster in computation time and, hence, it is suitable and
efficient for rapid evacuation.
Network vulnerability due to weather conditions is closely
related with the weather characteristics of the geographic
region where the network is deployed. In [41] a nonuniform
region vulnerability map was defined based on disaster occur-
rence probability and intensity of the region. The vulnerability
map is used as an input of an ILP formulation to identity
the optimal placement of DCs and contents that minimizes
failure risk due to disaster. Since content placement needs to
be optimized within a given warning time, ILP solutions, due
to their long running time, are not adequate and therefore
an heuristic is also suggested. If pre-fault recovery mecha-
nisms are not able to cope with network disruption post-fault
recovery schemes involving physical infrastructure repair or
replacement in a staged progressive manner is carried out. The
network will operate for some time in a degraded manner and
progressively recover to its pre-fault initial condition. In [42]
four post-fault progressive recovery schemes are proposed.
Uniform Placement, where repair resources are distributed in
an even manner across damaged nodes and links. Random
Placement , where repair resources are distributed in a ran-
dom manner. Physical Node and Link Degree, where repair
resources are assigned to failed nodes with the highest number
of physical links prior to failure and Virtual Node and Link
Degree that assigns repair resources to failed nodes/links with
higher numbers of embedded virtual/links prior to failure. In
all recovery schemes repair resources are distributed among
failed nodes/links that have at least one non-failed neighbour
node/link. This placement selectivity helps to improve the
network connectivity. Results indicate that uniform resource
placement gives faster initial recovery. However, uniform and
physical node degree placements, at the final stage, presents
slightly more efficient usage of network bandwidth resources.
V. RESILIENCY AGAINST WEATHE R-BASED D IS RUPTIONS
IN CONVERGED NETWORKS
Recent traffic explosion in telecom networks and the ex-
pectation of an even faster increase of traffic represent a big
challenge for network operators that have to minimize the total
cost of ownership while serving such traffic. In particular,
network operators must operate and maintain several access
technologies, either wired (DSL, FFTx) and wireless (WiFi,
3G, 4G) while minimizing costs, power consumption and
spectrum utilization in the wireless section. In 2009 a novel
wireless cloud architecture called Centralized Radio Access
Network (C-RAN) was proposed in [54] to ensure better
scalability to mobile cellular network archtiecures. In this
architecture the cellualr base station is divided into two parts,
the base band unit (BBU) and the remote radio head (RRH).
C-RAN implementation is often associated to other comple-
mentary architectures, such as, e.g., NFV and SDN (see e.g.
[55], [43], [56]). The C-RAN provides benefits to operators
and end-customers by enabling improved interference control,
and thereby improved throughput, and by providing higher
elasticity and scalability thanks to centralisation of BBUs.
The two key challenges for C-RAN realization is to devise
a bandwidth-efficient and latency-bounded transmission tech-
niques between the RRHs and the BBUs. In fact the so-called
fronhaul traffic (i.e, the traffic linking RRHs and BBBUs) has
very strict latency requirements coming from the air protocols,
as Time-Division Duplexing Long Term Evolution (TDD-
LTE), and from the coordination requirements. Moreover, the
fronthaul traffic is extremely bandwidth-intensive. Ref. [44]
presents results from field trials in the China Mobile’s TD-
LTE C-RAN, where compression techniques and wavelength-
division multiplexing (WDM) have been used to reduce fibre
count between the RRH and BBU pools. This field trial shows
that using C-RAN inter-cell interference may be significantly
reduced, with throughput gains of 20 to 50% at good coverage
areas (such gain may reach 50 to 100% at cell edge areas).
More importantly for our survey, [44] describes the severe
effect on the performance of failures in the transmission
network or in the BBU pools.
Some preliminary works are currently appearing that deal
with resiliency of the C-RAN architecture. In [43] the trade-
off between distributed and centralized RAN functionalities is
discussed depending on the actual needs as well as network
characteristics. A flexible functional split of the radio protocol
stack between the central RAN as a service (RANaaS) and the
local radio access points is proposed. The key requirement for
flexible functional split is the requirement for dynamic adap-
tation of network routes depending on available transmission
resources. This functionality may be used in case of a weather
alert to redistribute user traffic to the available base stations.
In [45] the problem of latency and reliability of a mobile
heterogeneous network with backhaul provided by an optical
passive network (PON) is considered. Typically, the coverage
areas of macro- and small-cells are overlapped. Furthermore,
the concept of WiFi offloading is considered. Since WiFi
is mainly an indoor technology, therefore offloading traffic
from impaired mobile networks to indoor networks could be a
good option. This network architecture provides to operators
some degree of freedom to modify user distributions across
the networks by means of traffic steering to improve network
performance according to network failures or a weather alert.
The virtualization of network functions, such as, e.g., C-
RAN, provides an architecture for elasticity and scalability
of of resources on demand. As discussed earlier in this
section, the C-RAN puts strict requirements on the latency
in transmission between the RRH and BBUs. In [46] the
localisation and capacity of the BBU pools are formulated
as a optimisation tasks where the cost of transmission and
BBUs is taken into consideration. This shows the potential
limitation of available fibres in the access network. It also
indicates that the number of redundancy between BBU pools
may be a challenge.
Ref. [47] addresses the survivability aspects of Next Gen-
eration - Passive Optical Networks (NG-PONs) and hybrid
Fibre-Wireless (FiWi) access networks, taking both optical
and wireless protection into account. The paper investigates
different selection schemes to find a small set of Optical
Network Units (ONUs) and equip them with wireless commu-
nication capabilities in order to guaranteeing a high degree of
survivability. The performance is examined for a wide range of
fibre link failure scenarios and different NG-PON topologies.
The redundancy-based restoration of virtualized network
functions due to malfunction has to take into consideration the
signalling messages between the the various network entities.
For instance, a re-instantiation of a virtualized mobility man-
agement entity (MME) in the evolved packet core (EPC) has
an effect on the traffic to/from user equipment (UE) handled
by the affected MME [48]. In [48] two proactive VNF failure
restoration approaches are proposed aimed at the reduction
of the network overload that may happen due to restoration
control signalling messages where as soon as a MME VNF
goes off or starts malfunctioning, a new MME VNF instance is
initiated. The first mechanism is based on bulk signalling, i.e.,
it creates only one single message to replace a certain number
of signalling messages in a bulk, while the second one creates
message profile, i.e., reduces the signalling message header by
replacing repetitive information element by a profile identifier.
The bulk signalling was the most effective mechanism to
reduce the signalling.
VI. ADVANCE D TECHNO LO GY F OR RESILIENCY AGAINST
WEATH ER -BA SE D DI SRUP TI ON S
We have described in previous sections how weather con-
ditions can significantly affect the performance of different
categories of communication networks (wired, wireless, con-
verged), e.g., by causing long delays that cannot be sustained
in existing Internet architectures. In this last section we move
our focus on a heterogeneous class of novel and experimental
networking technologies to see if they can offer new abilities
for realizing resilience when exposed to weather-based disrup-
tion.
Delay Tolerant Networking. Based on existing literature on
this topic Delay Tolerant Networking (DTN) seems to be the
most promising approach to overcome specific weather-related
outages. The Delay Tolerant Networking Architecture [57]
departs from the established Internet architecture paradigm of
end-to-end communication but it concentrates on techniques to
sustain long delays (order of hours or even more) and contin-
uous disruptions. Such events are considered unavoidable and
are part of the design. Hence, DTN inherently copes with them
by introducing the notion of storage inside the network stack,
transforming the “store-and-forward” paradigm to a “store-
carry-forward” one.
A large number of works explored DTN applications in dif-
ferent weather-challenged operation environments [49]. Here,
we highlight three examples. AX.25 is a link-layer proto-
col for packet radio networking over HF, VHF, and UHF
links of 1.200 bps. A series of experiments (cf. [43-47]
of [49]) revealed that DTN over TCP/IP Convergence Layer
outperforms established IPv4-based approaches in different
AX.25 network configurations, especially in cases of severe
winds that affected link-layer connectivity. A second example
is maritime communication with varying environmental and
weather conditions. Using real-world traces of WiMax links
for ship communications in the busy Strait of Singapore, it was
shown (cf. [93] of [49]) that DTN-based routing approaches
outperform ad hoc routing protocols (AODV and OLSR) in
packet delivery rates on the expense of greater delay that DTN
can cope with. A third example is a communication system
for underground mines, where radio communication is severely
limited by the (changing) topology of the mining tunnels and
the environmental conditions (e.g., humidity), and the mining
equipment. A DTN-based software system allowed to reliably
establish communication channels between the data sources
(drills), the intermediaries (pickups used to ferry workers
to/from the drill), and the sinks (wireless access points with
limited range), despite the lack of an end-to-end path and the
sporadic connectivity episodes [50].
The aforementioned examples highlight one of the core
principles of the DTN architecture. DTN does not try to hide
large delays or communication disruptions. Rather, such events
are considered unavoidable and become part of the design.
Information Centric Networking (ICN) is a family of
more clean-slate architectural approaches (e.g., CCN [58] and
NDN [59]) with the aim to evolve the Internet infrastructure
from a host-centric paradigm based end-to-end connectivity to
a network architecture in which the main target to be reached is
a “named information” (e.g., a content). ICN is expected to to
be helpful to support communications in emergency situations,
such as in the case of natural and weather disasters. In [51] sev-
eral advantages of ICN are discussed, including resilience due
to multi-homing and connectionless communication, as well
as open issues and research challenges, such as discovery of
information sources, management support, robust and resilient
routing, and push-based communications, as currently ICN are
pull-based. The need for push-based notification is addressed
in [60], where a new packet primitive is specified for CCN,
namely “Notification”.
Content Centric Networking (CCN) is an example of an
Information Centric Networking (ICN) architecture, where
“content” is addressable and routable. CCN and caching can be
useful alternatives in case of link failures at a local scale (e.g.,
due to extreme weather conditions). A performance evaluation
assuming realistic network topologies and simulations showed
that CCN can reduce by a factor of two the number of hops
to be traversed for retrieving information and thus, improve
network resilience [52]. Also CCN, therefore, might enable
new solutions against weather-based disruption especially in
content-centric network environments.
VII. CONCLUSIONS
Weather conditions can affect the performance of telecom
networks. In this survey, we classified and discussed relevant
studies in the field of network survivability against weather-
based disruptions. We considered first the modeling of the
impact of weather conditions on wireless channel quality,
with a specific emphasis on the structural impact of winds
on cellular towers. We then surveyed protection strategies
proposed in wireless networks (mostly, WMNs and FSO
network), wired networks (on which we focused on alert-based
reconfiguration techniques) and converged networks. Finally,
the role of advanced and innovative network architectural
proposal as DTN, NFV and ICN have been also discussed.
The importance of these topics is expected to grow in the next
years considering, e.g., the important role that wireless links
are expected to play in 5G networks (both in the access and
backhaul segments) and the increasing occurrences of extreme
weather conditions associated to global warming.
ACKNOWLEDGMENT
We would like to thank the participants of WG2 (Weather-
based disruptions) of COST Action CA15127 whom indirectly
collaborated in this task: Rasa Bruzgiene, Lina Narbutaite,
Adomkus Tomas.
This article is based upon work from COST Action
CA15127 (“Resilient communication services protecting end-
user applications from disaster-based failures – RECODIS”)
supported by COST (European Cooperation in Science and
Technology).
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