-
Content-Centric Wireless Networking: A Survey
Marica Amadeo, Claudia Campolo, Antonella Molinaro, Giuseppe
RuggeriUniversity Mediterranea of Reggio Calabria - DIIES
Department
Email: {marica.amadeo, claudia.campolo,
antonella.molinaro,giuseppe.ruggeri}@unirc.it
Abstract
Content-Centric Networking (CCN) is a candidate future Internet
architecturethat gives favourable promises in distributed wireless
environments. The latterones seriously call into question the
capability of TCP/IP to support stable end-to-end communications,
due to lack of centralized control, node mobility, dy-namic
topologies, intermittent connectivity, and harsh signal propagation
con-ditions. The CCN paradigm, relying on name-based forwarding and
in-networkdata caching, has great potential to solve some of the
problems encountered byIP-based protocols in wireless networks.
In this paper, we examine the applicability of CCN principles to
wirelessnetworks with distributed access control, different degrees
of node mobility andresource constraints. We provide some
guidelines for readers approaching re-search on CCN, by
highlighting points of strength and weaknesses and reviewingthe
current state of the art. The final discussion aims to identify the
main openresearch challenges and some future trends for CCN
deployment on a large scale.
Keywords: Content Centric Networking, Mobile Ad Hoc Networks,
WirelessSensor Networks, Vehicular Ad Hoc Networks
1. Introduction
Modern mobile devices such as smartphones, laptops, and tablets,
enabledwith wireless Internet connectivity and sensing
capabilities, are steadily growingin popularity and market
penetration. They can provide users with mobilityand flexibility in
accessing and generating information anywhere (e.g., in
home,office, shops, cars) and at any time. Wireless networking is
expected to playa crucial role in the future Internet, not only to
sustain direct interactionsbetween personal users devices, but also
as a means to provide connectivityon a large scale while involving
resource-constrained devices like sensors andsmart objects.
Conventional networking protocols designed to support
stableend-to-end communications between nodes that are uniquely
identified throughan IP address, fail in wireless distributed
environments due to dynamic changesin the network topology caused
by the node mobility, frequent link failures orthe presence of
energy-constrained nodes running out of battery.
Preprint submitted to Computer Networks June 3, 2014
-
In addition, it is also evident that the traditional
host-centric Internet modelmismatches the dominant
information-centric usage of the current Internet.Today,
applications such as video downloading, file sharing, social
networking,and cloud services, massively drive content retrieval
and dissemination in theInternet. To support the efficient and
reliable delivery of such applications, anumber of research
initiatives has recently advocated a shift from the
traditionalInternet networking model to a novel paradigm that
considers the content (orinformation) as the first class network
citizen and decouples it from the identityof the node(s) storing
it.
Information-centric networking has become one of the main
potential archi-tecture of the future Internet and several related
projects are active worldwide[1]. In this research arena, the
Content-Centric Networking (CCN) architectureproposed in the
seminal work of Van Jacobson [2] has rapidly gained consen-sus and
it is now at the basis of many research initiatives running
worldwide,including Named-Data Networking (NDN) [3] and others
cited in [4].
In CCN, each piece of data is associated with a
location-independent namethat is directly used by the applications
for content search and retrieval. Com-munication is driven by the
receiver, which uses an Interest packet to request acontent by
name. The content source, or any other network node that
tem-porarily stores the requested content, replies with a Data
packet that containsthe named content and additional authentication
and data integrity informa-tion. Each Data packet is a
self-identifying and self-authenticating unit; andthis enables
seamless in-network caching and content replication.
It is the authors convincement that CCN is an effective
networking paradigmthat well matches the features of wireless
environments. Indeed, CCN can over-step the inefficiencies of
TCP/IP in handling node mobility, unreliability ofwireless links,
and resource-constrained devices by relaxing the need of creat-ing
and maintaining stable sessions between end-points. Moreover, CCN
mayleverage the broadcast channel nature and help the content
sharing betweenneighbouring nodes.
Some good surveys have addressed information-centric solutions
[1], [4] andcovered topics ranging from naming to mobility
management and caching, e.g.,[5], [6], [7]. This paper differs from
the previous ones since it focuses specif-ically on the CCN
paradigm, and it provides a comprehensive overview anda clear
identification of the applicability, potentialities, weaknesses and
futurechallenges of this paradigm in wireless networks.
The rest of the paper is organized as follows. In Section II, we
introduce theCCN basics and major functionalities. In Section III,
we present the main fea-tures of wireless sensors, mobile and
vehicular ad hoc networks and we identifythe benefits of CCN in
such environments. In Sections IV-X different aspects ofthe CCN
applicability to wireless environments are analyzed, including
naming,routing and forwarding, caching, security, and transport
issues, as well as eval-uation platforms and prototypes. Section XI
summarizes the open challengesand future perspectives. Section XII
concludes the paper.
2
-
Figure 1: CCN hourglass and node architecture.
2. The CCN architecture
The CCN model [2] provides a new network architecture that
supports con-tent retrieval in the future Internet by using
Interest/Data packets exchange.
Each CCN name is persistent, unique and hierarchical and it can
be repre-sented as a Uniform Resource Identifier (URI). Integrity
and authenticity aresupported at a packet-level by piggybacking the
data publishers signature andother authentication information
(e.g., publisher public key digest) in the Datapacket.
Since each Data is a self-contained unit, caching is facilitated
in networknodes. Depending on local constraints and policies, a
subset (or all) of thenetwork nodes can cache contents and speed up
data retrieval while reducingthe overhead. A CCN node that
maintains a cached copy of the content can actas a provider like
the original source.
As shown in Figure 1, CCN inherits the hourglass model of the IP
archi-tecture, but the narrow waist leverages names of content
chunks instead of IPaddresses for data delivery.
Each CCN node maintains three data structures: (i) a Content
Store (CS)for temporary caching of incoming Data packets; (ii) a
routing table namedForwarding Information Base (FIB) used to guide
the Interests towards Data;and (iii) a Pending Interest Table
(PIT), which keeps track of the forwardedInterest(s) that are not
yet satisfied with a returned Data packet.
Routing in CCN serves the purpose of computing the FIBs entries
to be usedfor Interest forwarding. Given the hierarchical name
structure, CCN facilitatesglobal routing via prefix
aggregation.
The CCN forwarding plane is a two-step process that involves
Interests for-warding from the consumers to the retrieved data, and
Data packets flowingback along the same path to the consumers. Each
CCN node receiving an In-terest makes its forwarding decision based
on the following algorithm. First, itsearches for a name prefix
longest-match in its CS. If a match is found, thenthe node sends
the Data back to the incoming interface of the processed Inter-est.
Otherwise, if there is a matching PIT entry (another consumer has
alreadyasked for the same Data), the Interest is discarded and the
new incoming inter-face is added to the existing PIT entry.
Otherwise, a new PIT entry is createdand the Interest is further
forwarded to the interface stored in the FIB.
3
-
Figure 2: Interest/Data packets processing and forwarding
operations in CCN.
When a Data packet is retrieved, its name is used to look up the
PIT. Ifa matching entry is found, then the node sends the packet to
the interface(s)where the Interest was received, it stores the data
in the CS, and deletes the PITentry. So, Data packets follow the
chain of PIT entries back to the requester(s).If a match is not
found in the PIT then the Data packet is considered unsolicitedand
it is dropped.
For the sake of clarity, Figure 2 sketches CCN packets
processing and for-warding. Upon receiving the Interest from node
A, the intermediate node C,not finding a match in its CS or in the
PIT, forwards the Interest to the sourcenode D. Once receiving the
Data packet from D, node C forwards it back toA, and subsequently
it serves directly the request for the same content comingfrom B
with its cached copy.
CCN achieves one-to-one flow balance by letting each Interest be
consumedby a single Data packet. Moreover, it permits to specify
different transportservices at the Strategy Layer, depending on the
application requirements (suchas reliability, delay-tolerance) and
the network constraints (such as mobility,channel quality).
3. Content-Centric Wireless Ad Hoc Networking
3.1. Main Features of Wireless Ad Hoc Networks
Wireless ad hoc networking can be regarded as a type of
spontaneous infras-tructureless networking, automatically activated
when nodes are in line of sightwithout the need of any centralized
control. It can be characterized by differentdegrees of node
mobility, multihop communications, battery-powered devices,and
multifaceted possible deployments and use cases.
Mobile Ad hoc NETworks (MANETs) are self-organized multihop
networksthat support exchange of information without relying on any
pre-existing net-work infrastructure. Applications cover
home/office environments, tactical net-works, emergency services. A
MANET can be used either as a stand-alone
4
-
deployment with locally generated and exchanged data, or to
provide wirelessInternet access through gateway(s) connected to the
infrastructure. A MANETcan be formed among users devices sharing
similar interests (e.g., students ex-changing class materials in a
campus; workforce operators exchanging maps ina disaster recovery
scenario), or sharing location-based information (e.g., com-muters
exchanging information about train/bus departures times).
Unlike MANETs where routing nodes are mobile, in wireless mesh
networks(WMNs) routers are stationary and form a wireless multihop
backbone [8].Mesh routers offer wireless connectivity to mobile
devices that may use themesh backbone to connect to the Internet
through one or more gateways. Amesh network can benefit from
advance planning of the node positions, butnothing prevents it from
growing organically.
The ad-hoc networking paradigm is also at the basis of Vehicular
Ad hocNETworks (VANETs). By enabling vehicle-to-vehicle and
vehicle-to-infrastructurecommunications, VANETs can provide a
unique set of applications specificallydesigned for the road
environment to improve safety and comfort of drivers andpassengers,
e.g., by disseminating hazardous event notifications, road traffic
in-formation, advertisements about nearby points-of-interest [9].
Mobile nodes ina VANET move at higher speed than nodes in a MANET
and with predictablemovements. The high node mobility may cause low
connectivity and highlydynamic network topology with frequent
partitions. Vehicular nodes are en-abled with self-localization
capability, and have resources not limited by energy,memory, or
processing constraints.
The lack of an infrastructure is among the main features of
Wireless SensorNetworks (WSNs), which consist of (thousands of)
resource-constrained devicesthat communicate untethered [10]. These
networks are used for tasks such asenvironmental monitoring,
logistics, surveillance; hence they cannot be operatedin isolation
but need to be connected to remote servers. Sensor devices are
themost critical in terms of energy, memory and processing
resources.
Table 1 summarizes the main features of the aforementioned
networks. Al-though they have a huge potential in different
scenarios and arouse interestfrom service/network providers and
users, they suffer from serious technicalchallenges that could
hinder their massive deployment and efficient use.
Wireless channel. Signal propagation on the wireless medium may
beadversely affected by impairments like interference, path loss,
multipath fading,and shadowing effects, which could induce packet
errors and losses.
Distributed control. The broadcast wireless channel may
facilitate datasharing on the one hand, but on the other hand it
asks for specific channelaccess policies to keep collisions and
packet redundancy under control. Thedistributed channel access in
most wireless networks is based on carrier senseand may suffer from
hidden and exposed terminals problems with throughputdegradation,
especially harmful in multihop dynamic scenarios.
Mobility. Network topologies dynamically change due to node
mobility,which can range from low-to-medium (e.g., in a MANET) to
high mobility(e.g., vehicular nodes). Topology changes may cause
network partitions andlead to poor, intermittent, and short-lived
connectivity with negative effects on
5
-
Table 1: Main features of Wireless Ad hoc Networks.
Feature MANETs VANETs WMNs WSNs
Mobility Medium High Low-to-Static Medium-to-Static
Battery con-
straints
Medium (de-vices arerechargeable)
No constraint(energy istaken from theengine)
Low-to-Noconstraints(nodesare mostlyplugged)
High
Storage capa-
bilities
Medium-to-Low
Theoreticallyinfinite
High Low
Main reference
standard
IEEE802.11a/b/g/n
IEEE 802.11p IEEE 802.11s IEEE 802.15.4
the routing performance.Constrained Resources. With the
exception of infrastructured elements
and nodes on board of vehicles, wireless nodes are
battery-powered deviceswith limited processing power and storage
capabilities. These constraints areespecially critical for
sensors.
3.2. CCN advantages in wireless environments
Node mobility, multihop communications, battery constraints, the
lossy broad-cast wireless channel, the type of applications, and
the lack of an infrastructurecharacterizing wireless ad hoc
networks, heavily question the capabilities oftraditional TCP/IP
protocols to support efficient and robust end-to-end
com-munications [11]. This is why, over the years, alternative
networking solutionshave been devised that try to move away from
host-centric models and embracecontent-oriented communications.
Early precursors of the content-centric paradigm can be found in
the lit-erature on wireless networking (e.g., delay-tolerant [12]
and opportunistic [13]networking, content-based publish-subscribe
models [14]). These solutions areimplemented as an overlay on the
IP layer, which is used to address the networknodes. Unlike them,
the named-data CCN architecture can be also implementedon top of
any layer 2 access technology as a pure clean-slate solution.
The feasibility of applying CCN in wireless ad hoc scenarios,
such as general-purpose [11] and military [15, 16] MANETs, VANETs
[17, 18], and WSNs [19],[20], [21] has been recently discussed in
the literature, with preliminary deploy-ments in some cases [22],
[23], [24]. The motivations for such a surge of interestare
manifold.
First, consumer mobility is intrinsically supported in CCN: when
a consumermoves, it can simply re-issue any unsatisfied Interest
from the new location.Provider mobility may require routing
updates, but CCN inherently supportscontent multi-sourcing, thus
reducing the effects of a provider re-location [6].
Second, CCN retrieves information without the need of any a
priori knowl-edge of the source node identity. This is a clear
benefit for several mobile appli-cations that are
information-centric in nature: uploading a photo to Facebook
6
-
or Twitter, downloading videos from YouTube are examples of the
commonway for mobile users to access the Internet. Other emerging
applications arerelated to the exchange of surveillance data,
command and control, and soft-ware updates among mobile users in a
MANET. Similarly, in VANETs, traffic,weather, and parking
information can be requested by vehicles in a given area,regardless
of their identities or IP addresses. A variety of civilian,
scientific andmilitary applications based on data collection and
dissemination in large-scalemonitoring sensor networks, can also
benefit from hierarchical content namingand the simple CCN
Interest/Data exchange.
In addition, the majority of these applications consists of
information ad-dressed to more than one recipient. Such information
can be created explicitlyfor public dissemination (e.g., news,
weather information), or it can involve re-stricted groups of
recipients (e.g., a video streaming), or it can be
increasinglygenerated by end users (e.g., a post in a social
network). CCN natively sup-ports multicast data delivery, thanks to
the Interests aggregation in the PIT,according to which
intermediate nodes avoid forwarding multiple requests forthe same
Data packet while the first one is pending.
The fourth major advantage is that CCN can cope well with
intermittent,short-lived connectivity, and dynamic topologies in
wireless ad hoc environments.In fact, under node mobility, low
power operation and opportunistic contacts,having self-consistent
data units and exploiting in-network decentralized
datacaching/replication can substantially improve the quality of
communication bymaking the best of the broadcast wireless
medium.
In the following sections, the key design challenges of the CCN
paradigm arediscussed in detail, by surveying solutions proposed in
the literature. For thereaders convenience, the most representative
application domains for wirelessnetworks, their main demands and
native CCN benefits are summarized in Table2. In addition, Table 3
provides a summary of the main works that, to the bestof our
knowledge, recommend the adoption of CCN in MANETs, VANETs andWSNs.
Most of them propose general-purpose solutions without any
specificapplication in mind.
The majority of the surveyed literature supports CCN as a
clean-slate so-lution. An overlay of CCN on IP is not generally
recommended in ad hoc net-works for two main reasons: (i) the
end-to-end route set-up and maintenancebetween overlay nodes induce
high control overhead; (ii) the overlay designforces point-to-point
communications, without exploiting neither the broadcastradio
channel nor in-network caching [25].
4. Naming
A CCN content name is composed of one or more variable length
alphanu-meric strings separated by / , e.g., a Youtube video name
can be /youtube/-clipNetworking/CCN/introduction. CCN defines some
basic conventions for thehierarchical name structure (e.g.,
encoding human-readable name components,globally-unique name
prefixes), while the name semantics and the number ofsubstrings in
a name can be customized on the basis of applications, local
and/or
7
-
global conventions. As a consequence, application developers can
choose a hi-erarchy of name components that fits their needs and
lets name conventions tobe opaque to the network [47].
The CCN naming system is still under active research, and some
namingproposals in the context of wireless networks have recently
started to appear.
In [17] the authors explore the benefits of hierarchical CCN
naming inVANETs. The following name structure is proposed for
traffic information dis-semination:
/traffic/geolocation/timestamp/datatype, in which the name
com-ponents identify the temporal and geographical scopes of
traffic information,and the application data type. For instance,
the Interest with name /traf-fic/Road101/south/40,41/ could be used
to request traffic information abouta specified region of Road 101
(southbound, kilometres 40-41). Similarly, in[24], the interested
road area is encoded in the name; e.g.,
/traffic/westwood-at-strathmore/ would refer to the traffic
information from the area close to theWestwood-Strathmore street
intersection.
In [21], CCN names are customized to support sensor networking.
In orderto fit into an IEEE 802.15.4 frame, the authors assume that
the maximumlength of a content name is 50 octets and limited to
five components withmaximum 15 octets each one. In [19] a naming
scheme for WSNs is proposedto describe the sensing task, thus
allowing the sink to precisely ask for theneeded information, and
the sensors to describe the sensed data. The namestructure task
type/task location/task time period/nonce accounts for: thesensing
task (e.g., temperature, humidity); the geographic area in which
thetask is performed, stated either in terms of logical names
(e.g., a room) orin geographical coordinates; the time period in
which the task is performed
Table 2: Application domains and their requirements coupled with
CCN benefits and relatedliterature.
Application domain Main requirements CCN benefits Works
Battlefield operations anddisaster relief (MANETs)
High security, self-configuration, resiliency
Data integrity and originauthentication, possibil-ity of
encryption, mean-ingful naming, multipathsupport
[15], [16]
Vehicular safety applica-tions (VANETs)
Timely and reliable high-priority safety messagesdelivery
Broadcasting, meaning-ful naming, robust trans-port
[26]
Road traffic efficiency andinfotainment applications(VANETs)
Scalable delivery oflocal/spatial-relevantinformation
Lightweight route set-up and maintenance,caching
[17], [18],[24], [27],[28], [29],[30], [31],[32], [33]
Environment/Buildingmonitoring (WSNs)
(Large scale) period-ical short-lived smalldata delivery,
energyefficiency
Thin naming, easy con-figuration, Interest ag-gregation
[19], [20],[21], [22]
Video streaming(MANETs, VANETs,WMNs)
High bandwidth, low la-tency
Caching [34], [35]
8
-
Table 3: Literature Addressing CCN on top of Wireless Ad Hoc and
Sensor Networks.
MANETs VANETs WSNs
Naming - [17], [24] [19], [21]
Routing and for-
warding
[11], [15], [25], [36],[37], [38], [39], [40],[41], [42]
[18], [27], [28], [29],[30], [33]
[19], [21]
Transport [25], [37] [27], [31] -
Caching [25], [43] [27] [20], [21]
Security [15], [16], [44] [32] -
Prototypes [39], [45], [46] [24] [21], [22], [23]
Service models [26], [27] [20]
(e.g., an instantaneous measurement, or an averaged value over a
given timewindow); the unique data identifier used to identify
replicas. For instance,an Interest with name
humidity/room121/[timestamp1,timestamp2]/1323454declares that the
sink is looking for the average humidity in room121 during thetime
period between timestamp2 and timestamp1.
In summary, the CCN namespace is highly expressive and highly
customiz-able. By leveraging the hierarchical tree structure, CCN
name components canbe user-friendly attributes that describe the
content itself.
5. Routing and forwarding
Unlike in IP, where routing is the smart operation and
forwarding is con-sidered as dumb, in CCN both routing and
forwarding are smart. Routingrefers to the way FIBs are populated
by exchanging name-prefix announcementsamong routers; forwarding
refers to Interest and Data processing, which is donehop-by-hop
according to the decisions of the Strategy Layer in each node.
CCN nodes are expected to use any of the traditional routing
protocols(adapted to handle content names instead of IP addresses,
e.g., like in [48]) tofill in the FIB tables and keep them up to
date. So far, the definition of proac-tive routing protocols in CCN
wireless ad hoc networks has not been specificallyinvestigated.
This is mainly because to manage name-prefix advertisements isvery
challenging in mobile networks and may introduce some overhead
(e.g.,related to data source mobility, dynamic data catalogues,
possibility of aggre-gating name prefixes, frequency of updates,
etc.), so that the cost of maintainingrouting information may
overwhelm the benefits of proactive solutions [40]. Inaddition, in
such distributed environments contents may be time-and
location-relevant and be generated on the fly. Therefore, the CCN
literature usuallyrelies on reactive flooding-based approaches to
discover content in wireless net-works. Only a recent work [33]
proposes proactive advertisements in case ofpopular
non-sharable/non-cacheable data, by using Bloom filters to reduce
theoverhead.
The CCN stateful forwarding plane may leverage information
stored in thePIT and the FIB to make forwarding decisions adaptive
to network conditions
9
-
[49]. Nonetheless, the design specifics of the CCN forwarding
fabric that fitwireless networks and applications remain to be
filled. Strategy modules couldbe customized that sometimes violate
the basic CCN forwarding rules.
We organize the remainder of this section in two parts. First,
we scan simpleflooding-based solutions for data dissemination in
content-centric wireless net-works. Then, we examine enhanced
techniques that introduce some selectivityin the CCN forwarding
decision process by leveraging additional (discovered)information
about the neighbourhood and the producer(s). We call blind andaware
the two forwarding approaches respectively.
5.1. Blind forwarding
CCN implementations in wireless environments may leverage the
broadcastnature of the radio channel to help data dissemination
[11], [27], [37], [42].
Flooding is the easiest way to forward Interest packets on the
wirelessmedium. Such an approach has the virtue of simplicity and
well faces situa-tions in which end-to-end path set up and
maintenance are difficult and costly,such as in dynamic ad hoc
environments and with resource-constrained devices.Flooding
facilitates content sharing in the network; in fact, a node
overhearingsome data of interest requested by other nodes can
access it without an explicitrequest. This reduces the number of
transmissions and saves the nodes en-ergy. However, flooding on a
broadcast medium must be handled with care andcontrolled to avoid
the broadcast storm [50].
To counteract packets redundancy and collisions, solutions in
the literaturemainly rely on distributed packet suppression
techniques. The basic idea is thata node defers the packet
forwarding while overhearing the channel and, eventu-ally, drops
the packet if it hears the packet transmitted by a neighbour [11,
15].Distance-based, slotted random, or purely random defer
strategies can be imple-mented. In [27] a set of timers is used to
assist Data broadcasting in vehicularenvironments. Specifically, a
collision-avoidance timer is used by neighbour-ing cars that
simultaneously receive an Interest for traffic jam information,
toreschedule Data broadcasting at different times. A similar
approach is followedin [18, 30], where different defer timers are
used for Interest and Data forwardingin order to minimize the
collision probability and prioritize Data over Interests.
However, a blind controlled flooding based on the above
mentioned simplecountermeasures does not always guarantee that (i)
the best nodes are selectedto forward packets, and that (ii)
overhearing avoids packet collisions. This iswhy controlled
flooding can be regarded as a baseline implementation of
CCNbroadcasting in wireless networks, on top of which more
sophisticated and awareforwarding strategies can be deployed, as
discussed in the following.
5.2. Aware forwarding
New awareness mechanisms have been included in the forwarding
plane tohelp in selecting the outgoing interface, the content
provider(s), and the next-hop nodes, by leveraging new entries in
(new) tables, additional packets and/oradditional fields
piggybacked in Interest/Data packets.
10
-
Interface selection. CCN forwarding may leverage the information
storedin PITs and FIBs to select the outgoing interface(s) at each
node. For example,the FIB may keep track of the delivery
performance (e.g., in terms of latency,throughput, round-trip
times, cost) of each outgoing interface, so that packetsare
transmitted via the best performing interface [49]. In [26],
vehicles thathave access to multiple networks (such as IEEE
802.11p, WiMAX, UMTS)transmit safety messages over the low latency
interface. Packets could be alsosimultaneously transmitted over all
available interfaces of different technologiesto cope with
disruption in connectivity [24].
As a further option, the outgoing radio interface can be
selected so as toooad the cellular infrastructure by leveraging the
ad hoc connectivity of nearbynodes. This is the approach followed
in [34] and [35] for mobile video streaming,where the CCN
routing-by-name is used to enforce the download of a videosegment
either through cellular or Wi-Fi interfaces.
Next-hop selection. Some awareness can also be used by a CCN
node toselect the next-hop in Interest/Data forwarding. In the
direction-selective datadissemination solution in [41] the Interest
sender initially divides its surroundingspace into four quadrants
and broadcasts the Interest (including its own node-idand
geo-location information) to all one-hop neighbours. The farthest
node ineach quadrant is then selected as a relay node for the
Interest packet. In [25]the eligibility of a relay node is decided
by its data retrieval rate for the givenname prefix and its
distance to the data consumer. If the data retrieval rate islow or
the node is too far away from the consumer, the incoming Interest
willbe discarded locally. In [27] a pushing timer is used in
vehicular networks toforward locally generated data (e.g., an
accident warning) further away fromthe point it was originated
(e.g., towards drivers travelling towards the accidentplace). A
farther car from the previous transmitter uses a shorter timer than
anearby car to schedule Data re-broadcasting.
The BlooGO proposal [38] determines if forwarding the packet or
not bycomparing the neighbourhood of the sender and the receiver.
This is possiblesince a Data packet carries a Bloom filter field
that includes the identifiers ofthe nodes in the transmission range
of the sender. They are collected throughperiodical beacon
broadcasting. A node forwards the packet only if its
localneighbourhood is not completely included into the one
advertised in the incom-ing packet, so that the progress of packets
is ensured without much redundancy.BlooGO is used as the routing
protocol in the MADN platform [39], a modulararchitecture for
multipath data distribution in content-centric MANETs.
In [19] a forwarding strategy is designed that creates a
direction state duringthe initial content discovery phase in a WSN.
After receiving an Interest, thediscovered producer sends the Data
and includes its identifier in an additionalpackets field. A
receiver node stores this identifier in the so-called Next HopTable
(NHT) and then forwards the packet towards the consumer with its
ownidentifier information. As a result, the NHT in each crossed
node contains abind between the content name, the producer, and the
next hop identifier and apath is created that is used any time the
consumer sends a subsequent Interestto retrieve more Data.
11
-
Path selection. Thanks to the broadcast nature of the wireless
medium,Interests may propagate along multiple paths towards
potential provider(s), andeven Data packets may be returned over
multiple paths, especially when mul-tiple copies of a content item
are cached in the network. Multipath retrievalis particularly
beneficial in wireless ad hoc networks, because it can mitigatethe
service disruption periods due to node mobility or adverse
propagation con-ditions, and can limit the overhead caused by
end-to-end path establishmentand maintenance. In [29], the data
diversity over multiple paths is beneficiallyexploited in a VANET.
By applying network coding techniques, intermediatenodes perform a
linear combination of the received chunks, and then they trans-mit
the result to the neighbours.
Provider selection. If the consumer discovers more than one
contentsource, the best performing provider can be selected based
on some criteria.
In [15], after an Interest reception, a provider transmits a
Reply packet toadvertise itself in a MANET. The consumer may
collect more than one Replyfrom different providers, select one of
them and send back a Request to the targetprovider, which is
allowed to reply with Data. Similarly, in [41] four
packets(Interest, ACK, CMD and Content) are exchanged. A three-way
handshakescheme is also proposed in [11] with the similar intent of
routing Data over themost stable consumer-provider path.
The selected provider can be advertised in subsequent Interests
so that in-termediate nodes can properly route the packet, as
advocated in [30, 28]. Lightpath-state information (the selected
providers identifier and its hop distance tothe consumer) are
included in Interest and Data and left as bread crumbs in aProvider
Table kept by CCN nodes in a MANET. In doing so, the twofold
bene-fit is achieved of keeping the channel load under control and
reducing downloadtime and energy consumption [37]. One could
reasonably argue that by fixingonly one provider could reduce the
CCN advantages of fetching the content fromdifferent nodes.
However, in-network caching is fully operative, in the sense thatin
case of packet losses, any intermediate node caching the missing
Data cancompensate for the loss and provide it, although not being
the selected provider.
6. Caching
On-path data caching provided by CCN is especially useful in
infrastruc-tureless wireless networks: it promises high content
availability, network trafficreduction, and low retrieval latency,
by mitigating the challenges induced bylossy links, bandwidth
limitations, and node mobility. By caching data, a mo-bile node may
also enable store-carry-and-forward communications and serve asa
link between disconnected areas. This particularly suits the VANET
environ-ment [27].
Caching in ad hoc networks has been widely studied in the
literature thatpreceded CCN, especially in the context of
opportunistic networking and datamuling. However, the novelty of
CCN is the coupling of caching and named-data. In fact, names make
the content accessible in an application-independentmanner, so that
a request for a named content can be satisfied by any matching
12
-
data regardless of its location. Additional peculiarities of the
CCN architecture(e.g., splitting content in chunks, correlated
content requests) make caching inCCN a quite new, and widely
uninvestigated, research topic, as briefly discussedin the
following.
Chunks partitioning. Unlike most existing works, where entire
objects aregenerally cached, in CCN content is partitioned in
chunks of small size, so thatdifferent chunks of the same object
may be cached on different CCN nodes. Insuch a case, the cached
fragment phenomenon discussed in [25] may affect dataretrieval,
especially if caching is coupled with a single-path forwarding
strategythat keeps sending Interests to the first found content
source, like in [36]. Infact, although the complete data object
resides in a single provider (i.e., a singlephysical node),
consumers may wrongly select other discovered nodes that holdonly
partial objects. To overcome this issue, the node sending Data
shouldadvertise if it owns the entire object or only some
chunks.
Another issue to consider is that CCN requests for consecutive
chunks ofthe same object are correlated, so that the traditional
independent referencecaching model no longer holds [51]. Although
few recent studies consideredcorrelated arrivals, the analysis is
limited to simple topologies with single paths(e.g., cascade or
tree) and, hence, they cannot be straightforwardly extended
toad-hoc dynamic topologies.
Cache decision and replacement policies. Cache decision shall be
takenat each CCN node regarding whether or not to cache the current
data; then, incase of positive decision and if the cache is full,
the node may need to replace astored chunk according to a
replacement policy. The CCN architecture does notmake specific
assumptions on cache decision and replacement policies; howeverthe
related literature has typically considered that all nodes may
cache all newchunks (this is the Leave a Copy Everywhere, LCE,
assumption), and that theLeast Recently Used (LRU) chunk is
replaced if a cache is full.
Concerning caching decision, caching every content in every node
along thedelivery path(s) may cause caching redundancy, so playing
against the CCNefficiency if not coupled with a smart forwarding.
Furthermore, indiscrimi-nate caching may waste network bandwidth
and device energy, due to mul-tiple transmissions of cached
contents from many nodes; and this is a threatin wireless
environments. In order to select what to cache (and then
eventu-ally what to replace), in the traditional caching
literature, popularity-drivenapproaches are considered to favour
keeping more popular contents in caches.In [43], the Location-Aided
Content Management Architecture (LACMA) forMANETs binds data to
geographic locations and more densely replicates popu-lar contents
so to push them closer to potential consumers. However, as arguedin
[51], also forcing many replicas of popular content in multiple
caches may bedetrimental for cache diversity in the CCN context
with correlated arrivals andnave forwarding on multiple paths.
Beyond the decision about what to cache, the dynamicity of many
wire-less networks, characterized by short-lived contacts, and the
spatial- and time-relevant nature of locally exchanged contents
(e.g., in a VANET) make thedecision about where to cache to be a
major concern in mobile networks. While
13
-
caching in vehicular devices comes at a negligible cost, since
on board units arenot limited by energy and storage constraints,
the same consideration does nothold for resource-constrained
devices like sensors [21, 20]. The authors of [27]propose a data
muling service in VANETs where each vehicle caches overhearddata,
even though it is not interested in, and then performs proactive
data push.
Solutions where only selected nodes in the delivery path cache
the contentmay leverage the node betweenness centrality in a
topology, according to whichsome nodes have higher probability of
getting a cache hit [52]. Centrality-baseddecisions could be easily
applied in static wireless scenarios (such as a meshbackhaul), but
they are more difficult to extend to mobile scenarios, where
thetopology dynamically changes and the concept of node centrality
is less intuitive.
7. Security
Despite the clear benefits of content-centric
location-independent security,many issues still need to be tackled.
Some of them, including the possibility ofcache pollution and
Denial of Service (DoS) attacks via Interest flooding, arecommon to
wired and wireless networks [16]; while others are strictly related
towireless environments, e.g., the computational cost of
data-security in presenceof resource-constrained devices, the
absence of trusted third parties in infras-tructureless scenarios.
So far, CCN security in ad hoc and sensor networks hasbeen poorly
investigated; most of the work is focused on (or at least testedin)
wired topologies, e.g., [53]. The main reason is that the wired
environmentis easier to tackle until some robust solutions have
emerged and matured. Inthe following, we focus on the few
fundamental security aspects that should beconsidered in
wireless-specific design.
The problem of key distribution and management in tactical and
emergencyMANETs has been tackled in [15] and [16]. The authors
assume that the con-ventional CCN security framework is enabled,
but public and private keys mustbe pre-assigned before nodes are
dispersed in the field by using a pre-definedkey management tool.
It is widely accepted, in fact, that several key manage-ment
schemes (with fully or partially distributed certificate authority)
designedin past years for ad hoc networks [54] can be extended to
CCN nodes.
A new alternative approach to verify the public-key and producer
identitybinding in wireless networks is presented in [44], where a
social network-basedsecurity scheme is proposed that employs a
trusted chain of friend relation-ships. Since the producer identity
is included in the Data packet, the contentrequester will first
look up into the local Identity Bundle Table (consisting ofthe
identity-id and its public key). A match implies instant
verification. If thelocal table does not contain this binding
relationship, the requester must sendout another Interest packet
with the identitys name to retrieve the producersidentity bundle
from the social trust graph. By doing so, both authenticity
andintegrity problems are solved in a more flexible and distributed
way.
In [32], a secure application is built for data collection from
vehicles thatallows manufacturers to verify integrity and
authenticity of incoming contentand to protect privacy of mobile
users. Data packets originated by vehicles are
14
-
tagged with their signature and encrypted using the public key
of the referencedatabase server. The authors assume that the data
collector has access to eachmobiles public key. This is reasonable
for vehicle manufacturers as they couldrecord public keys of
vehicles and also store the public key of the database serverinside
vehicles before release.
The burden of security support in memory-constrained devices has
not beenconsidered in preliminary implementations of CCN in WSNs
[20, 21, 22, 23],where the Data packet is assumed to include only
Payload and Content namefields. Similarly, the cost of security
operations in terms of time and energyconsumption has not been
analyzed in presence of battery-powered ad hoc andsensor devices.
However, it would be worth exploring in depth security issuesin
resource-poor wireless nodes to better figure out their actual
impact on CCNperformance, which could heavily change when
authentication and cypheringprocedures will be in place.
8. Transport
The CCN Strategy Layer may perform some functions that are
typical ofthe Internet transport layer, e.g., unacknowledged packet
retransmissions andrate regulation. Differently from the TCP, these
functions are implemented byCCN nodes hop-by-hop and not
end-to-end.
Interest retransmissions. Due to the shared and lossy nature of
thewireless channel, Interests/Data packets may be lost or
corrupted in transit, orData may be temporarily unavailable due to
the provider mobility. To support areliable transport, if a pending
Interest is not satisfied in a given period of timewith a returned
Data packet, a new Interest must be retransmitted. The
relatedretransmission timeout (RTO) setting is critical to quickly
recover packet losseswhile limiting useless retransmissions.
Currently, a specific algorithm for the computation of the
Interests RTOin CCN networks has not been defined. In [27], where
traffic information dis-semination is VANETs is considered, every
vehicle broadcasts a packet severaltimes with a pre-configured RTO.
When the node hears that the packet hasbeen successfully
re-broadcasted, it cancels subsequent retransmissions.
TCPs RTO estimation [55] has been extended to work also in
content-centricVANETs [31]. Each CCN node tracks the time when an
Interest has been for-warded and records a Round Trip Time (RTT)
sample when the requested Datais received. Then, the average RTT is
estimated as a moving average of RTTsamples, and the RTO is
dynamically adapted to follow the average RTT varia-tions. The
problem is that the dynamics of ad hoc networks topologies
coupledwith the channel unreliability and potential congestion may
create fluctuationsin such estimation. In addition, different nodes
can store the same content intheir caches; so a consumer could
receive successive Data packets from differentnodes. As a
consequence, the RTT fluctuations could be very high. To copewith
this issue, it is crucial for the consumer to know the identity of
the contentsource, in order to maintain separated RTT measurements
and/or to perform
15
-
selective updates. In [37], for example, the RTT estimation is
updated only ifthe Data packet is sent from the selected
provider.
Interest rate regulation. In CCN multiple Interests asking for
successiveData may be pipelined to maximize the bandwidth usage. By
properly tuningthe Interests transmission rate, a node can control
the traffic flow accordingto the available network resources.
Interest rate control is however still poorlyinvestigated in the
literature for wireless ad hoc networks.
In [25], the Neighborhood-Aware Interest Forwarding (NAIF) uses
localstatistics to adjust the fraction of Interests a node in a
MANET should for-ward for a given name prefix. NAIF is based on the
following intuition: themore Data of the same name prefix a node
overhears from its neighbors, themore Interests corresponding to
that name prefix it can drop.
In this way, the nodes cooperatively regulate the Interest
forwarding ratewithout congestion.
Another Interest rate control scheme is presented in [37], where
a transportfunction is defined for wireless multihop environments.
The proposed mecha-nism adapts the Interest transmission at the
consumer-side on the basis of theobserved Data arrival rate and an
explicit feedback from intermediate nodesthat advertise the minimum
sustainable data rate on a given path. The re-ceived Data rate at a
consumer gives an indirect measure of global congestionin the
network; while the sustainable data rate gives information on the
localcongestion in a node (the bottleneck) on the path. The
Interest rate is regulatedso to be slightly higher than the
received Data rate, while not overloading anynode in the path.
9. Overhauling the CCN philosophy
In the previous sections, literature solutions have been
surveyed that pro-pose enhancements to the main pillars of the CCN
model, caching policies,while keeping the main tenets of the
paradigm, i.e., receiver-driven communi-cation supporting both one
(source)-to-one (consumer) and asymmetrical one(source)-to-many
(consumers) communication modes. However, for the sake
ofcompleteness, it is worth observing that some works also proposed
some revi-sions of the CCN philosophy to enable not natively
supported service models.
With its Interest/Data exchange, CCN natively supports a pull
(or on-demand) service model, where the consumer starts
communication by declaringthe requested content and there is a
1-to-1 relationship between Interest andData. Nevertheless, with
proper adaptations, push (or publish-subscribe) ser-vices, in which
Data packets are sent without any Interest solicitation, could
alsobe supported by CCN [57]. This could be the case of media
streams or real-timenotifications, such as sensors immediately
reporting abnormal detected param-eter values [21], [20], and cars
transmitting safety messages [26] or gatheringdata about
surrounding environments (e.g., traffic jam, road closure)
[27].
In addition to the addressed case where information is generated
by a singleprovider and requested by multiple recipients, some
applications in the wireless
16
-
domain may involve more than one content producer. For instance,
a sink nodemay be interested to gather all temperature information
from many sensors ina place. In this case, a consumer sending the
Interest may expect to receivemultiple content objects (with names
that share some common parts) frommultiple sources.
Depending on the application domain, three major add-ons to CCN
can beidentified to support the mentioned service models. Such
modifications requirethe CCN communication fabric to be properly
re-engineered both in terms oftransport mechanisms and semantics of
packet types.
1. Pushing via Unsolicited Data. In [26], unsolicited content
packets calledEvent packets are used to disseminate safety
information in a VANET. TheEvent Packet has the same structure as
the CCN Data, but features an addi-tional field called Expiry Time
that indicates the time after which the packetshould be deleted.
Similarly, in [27], unsolicited Data are published by a car atthe
head of a vehicle sequence in the travelling direction and then
disseminatedby other cars acting as data mules.
2. Pushing via Long-term Interests. The concept of long-term
Interests hasbeen examined in [56], [57] and used in [58] to
deliver multiple real-time contentpackets with only one Interest.
In this implementation, Interests are not deletedafter a matching
Data is forwarded, but they remain in the PIT until users
ex-plicitly unsubscribe from a channel or their lifetime expires.
Therefore, Interestpackets are extended with one more optional
selector fields, which indicate thepacket type: long-term or
normal. Such a concept could be also successfullyapplied to support
periodical (untriggered) data monitoring in WSNs.
3. Multiple Data via Continuous Interests. The notion of
continuous Inter-est is used in [20] to handle many
(sources)-to-one (consumer) communicationmode. Similarly to
long-term Interest, the continuous Interests lifetime is setfor a
long period of time and the packet must not be deleted after the
soliciteddata has been received, thus a node could receive the same
kind of data fromdifferent producers.
10. Evaluation tools
Several simulation and emulation tools are currently available
to analyze theCCN performance and its potential extensions to
operate in wireless and mobilead hoc networks.
The majority of discussed works has used customized CCN modules
as eval-uation tools built on top of existing simulation platforms
like ns-2 [37], Qualnet[25], [36]. In order to incentivize studies
on CCN a new software module forthe open-source ns-3 network
simulator [59], namely ndnSIM [60], has been re-leased in 2012. An
official simulation environment that strictly follows the
CCNcommunication model, ensures more accurate results and the
reproducibilityand the comparability of simulations conducted by
the CCN research commu-nity. Under active development worldwide,
ndnSIM supports the core featuresof CCN in a modular way and can be
the best environment to simulate large
17
-
scale wireless networks. In fact, ns-3 provides modules that
reproduce mobilityand propagation models, and various access layer
technologies such as IEEE802.11g and 802.11s.
Due to its recent deployment, to the best of our knowledge, only
a few papersusing ndnSIM for CCN performance evaluation in wireless
networks have beenpublished, e.g., [19], [27].
CCNx [61] is an open source software reference implementation of
the CCNarchitecture and protocol, developed at Palo Alto Research
Center. It is avail-able for deployment on several operating
systems such as Linux, Unix, MacOSand Android. The core component
of CCNx is the ccnd daemon, which sup-ports the forwarding plane
and the caching service; it currently can run as anoverlay on top
of IP to take advantage of existing connectivity.
Recently, NDNBlue has been released [62], a cross platform proxy
layer forLinux and Android systems, which works between CCNx and
Bluetooth stacksto achieve CCN connectivity directly over Bluetooth
links.
In [22], an extension of CCNx is presented to support a
content-centric com-munication layer over Contiki, an open-source
operating system for embeddeddevices and WSNs that relies on IEEE
802.15.4 at the physical and MAC layers.
Another fully customizable and open source platform is the
CCN-Java Open-source Kit EmulatoR (CCN-Joker) for wireless ad hoc
networks [63]. It is anapplication-layer platform, specifically
tailored for wireless devices with limitedresources in terms of
storage capability and computational load, which can beused to
build a CCN overlay and is suitable for both emulation-based
analysisand real experiments.
11. Open Challenges
From the literature overview in the previous Sections, it
clearly emerges that,despite the young age of the topic, several
works have appeared addressing CCNin wireless environments, due to
its inherent potentialities. The main findingsfrom the scanned
literature are summarized in Table 4 that shows the mainpotential
benefits of CCN for wireless networking and the research trends
foreach of the main CCN pillars.
Despite the enhancements and modifications proposed in the CCN
communi-cation fabric to overstep challenges and constraints of
wireless ad hoc networks,research in this field is still at the
beginning and some hints for future deploy-ment can be provided as
follows.
As regards naming schemes, there is a tight relationship between
naming,applications and access network constraints. Although CCN
names can havevariable lengths without any a priori fixed upper
bound, wireless technologiessuch as IEEE 802.15.4 have very limited
payload sizes and should work withthin content names. It is
mandatory for application designers to interact withthe CCN
developers in order to converge on some standard
application-specificand access network-compliant naming
definitions.
18
-
Table 4: CCN for wireless networking: main benefits and research
prospectives.
CCN pillar Main benefits Research prospective
Naming (i) Low-cost network configu-ration (ii) Theoretically
infi-nite/unbounded namespace
Naming schemes adapted to applicationstype, institution
requirements, networkconstraints, and/or global conventions
Security (i) Content-based security; (ii)No need of securing
chan-nels/boxes in the delivery path
(i) Key management infrastructures; (ii)Computation- and
bandwidth-efficientsignature schemes; (iii) Effective and flex-ible
trust models
Routing and
Forwarding
(i) Lightweight route setup andmaintenance; (ii) Easy
mul-ticasting; (iii) Multipath for-warding and multiple
providers;(iv) Leveraging broadcastingand channel overhearing
(i) Advanced controlled flooding and re-active schemes; (ii)
Prioritization policiesfor different types of contents; (iii)
Net-work coding techniques to enhance mul-tipath routing
performance, (iv) Robustpacket suppression techniques
Caching (i) Coping with intermittentconnectivity and error
pronechannels, (ii) Shortening thecontent retrieval time
Policies adapted to device constraints,content type, node and
network features
Transport Connectionless communications (i) Interest/Data
retransmissions proce-dures, (ii) Interest rate control
policies
Many issues related to security are completely open. It is worth
noticingthat many wireless nodes are resource-constrained devices
and signature and au-thentication operations can be computationally
expensive in terms of time andenergy resources consumption. At the
same time, several applications in wire-less domains, e.g., for
control systems [64], may require the use of authenticatedInterests
in addition to signed Data. This further complicates the
managementof the wireless security framework. Therefore, the use of
public key cryptog-raphy claims for two open tasks: (i) definition
of an efficient key managementmethodology that works in
infrastructureless environment, and (ii) developmentof computation-
and bandwidth- efficient signature schemes.
The number of proposals handling CCN routing and forwarding
chal-lenges in wireless environments witness the interest of the
research communityin these topics. Overall, there is a wide
consensus on leveraging some kind ofawareness in the Strategy layer
to augment the CCN forwarding fabric. How-ever, the trade-off
between the overhead of transferring and/or keeping aware-ness in
every node (e.g., additional information about providers and/or
neigh-bors) and the achieved benefits in terms of packet delivery
performance shouldbe carefully considered by accounting for the
requirements of the applications,the nodes capabilities and the
network conditions. Moreover, the routing designshould be tighten
to both caching and transport routines.
Concerning caching, storage is becoming cheaper and of smaller
footprint:modern smartphones and tablets have significant storage
capacity often reachingseveral gigabytes. Thus, caching space would
not be a big matter, unless toconsider battery-constrained devices
and sensors typically equipped with a fewkilobytes memory. Several
design options shall be considered to decide where,what, and how
long caching data. For instance, in an environment with nodes
19
-
equipped with heterogeneous capabilities, data storage could be
distributed in afew nodes, more powerful than the others. In a more
general case, the popularity,the priority, and the type of contents
could make the difference to decide whatand how long caching
data.
Transport issues pose several concerns related to the regulation
of the In-terest rate and the estimation of the retransmission
interval, which are especiallycritical in wireless environments
with dynamic topologies and high node mobil-ity. Both aspects are
crucial to ensure reliability, flow balance, and congestioncontrol
in distributed wireless environments.
An additional aspect to consider for a comprehensive analysis of
CCN inwireless environments includes the deployment mode. Although
the intro-duction of any new technology always claims for
additional costs and compati-bility issues, it is worth noticing
that wireless access nodes (access points, meshrouters, road-side
infrastructure units, etc.) and devices (smartphones,
tablets,vehicular on board units, etc.) can be easily augmented
with a software CCNstack that works directly over the access layer
technology, thus building purestand-alone content-centric
environments. Connectivity through an IP-basedbackbone can be
performed by enabling some nodes with proxy functions or
byimplementing overlay solutions.
Finally, it is interesting to briefly speculate on the
relationships betweencontent-centric wireless networking and other
emerging paradigms, like cloudcomputing [65] and social networking
[66].
On the one hand, it is worth investigating how CCN can help to
(i) makecloud computing deployable on a smaller scale in mobile
environments, and (ii)support mobile social networking
applications. On the other hand, it should beexplored if and to
which extent (i) CCN can benefit from mobile cloud comput-ing,
e.g., to augment distributed in-network content storage, and (ii)
the designof cross-layer protocols inspired from social networking
analysis can improveCCN performance (e.g., through socially-driven
forwarding and caching opera-tions) and reduce security-related
threats to make content delivery trustworthy(e.g., by exploiting
social relationships among nodes).
12. Conclusions
In this paper we provided a survey on the state-of-the-art of
the content-centric networking principles and architecture applied
to wireless ad hoc envi-ronments (e.g., MANETs, VANETs, and
WSNs).
By leveraging named data, in-network caching and lightweight
forwarding,the Content Centric Networking paradigm is a
particularly attractive solutionfor wireless networking, facing the
limitations of resource-constrained devicesand overstepping
mobility and wireless channel issues, hardly addressed by
con-ventional TCP/IP-based solutions. Irrespective of the huge CCN
potentialitiesin wireless environments, research on this topic is
still in its infancy; many re-search challenges still lie ahead,
mainly concerning security and privacy, cachingand transport
issues, and have to be addressed to bring CCN for wireless
net-working to life.
20
-
References
[1] B. Ahlgren, C. Dannewitz, C. Imbrenda, D. Kutscher, and B.
Ohlman, A Survey ofInformation-Centric Networking, IEEE
Communication Magazine, vol. 50, no. 7, 2012.
[2] V. Jacobson et al., Networking Named Content, in ACM CoNEXT,
Rome, Italy, 2009.[3] Named Data Networking (NDN) Project,
http://www.named-data.net/.[4] G. Xylomenos et al., A Survey of
Information-Centric Networking Research, IEEE
Communication Surveys and Tutorials, vol. 16, no. 2, 2014.[5] M.
Bari, S. Chowdhury, R. Ahmed, R. Boutaba, and B. Mathieu, A Survey
of Nam-
ing and Routing in Information-Centric Networks, IEEE
Communications Magazine,vol. 50, no. 12, pp. 4453, 2012.
[6] G. Tyson, N. Sastry, I. Rimac, R. Cuevas, and A. Mauthe, A
Survey of Mobility inInformation-Centric Networks: Challenges and
Research Directions, in ACM NoM12,Hilton Head, SC, USA, June 2012,
pp. 16.
[7] G. Zhang, Y. Li, and T. Lin, Caching in Information Centric
Networking: A survey,Computer Networks, 2013.
[8] M. Conti and S. Giordano, Multihop Ad Hoc Networking: The
Reality, IEEE Com-munications Magazine, vol. 45, no. 4, pp. 8895,
2007.
[9] G. Karagiannis, O. Altintas, E. Ekici, G. Heijenk, B.
Jarupan, K. Lin, and T. Weil,Vehicular networking: A survey and
tutorial on requirements, architectures, challenges,standards and
solutions, IEEE Comm. Surveys & Tutorials, vol. 13, no. 4,
2011.
[10] I. F. Akyildiz, W. Su, Y. Sankarasubramaniam, and E.
Cayirci, Wireless sensor net-works: a survey, Computer networks,
vol. 38, no. 4, pp. 393422, 2002.
[11] M. Meisel, V. Pappas, and L. Zhang, Ad Hoc Networking via
Named Data, in Mo-biArch10, Chicago, Illinois, USA, September
2010.
[12] K. Fall, A Delay-Tolerant Network Architecture for
Challenged Internets, in ACMSIGCOMM03, New York, NY, USA, 2003, pp.
2734.
[13] J. Scott, P. Hui, J. Crowcroft, and C. Diot, Haggle: a
Networking Architecture DesignedAround Mobile Users, in IFIP WONS,
January 2006, pp. 7886.
[14] F. Guidec and Y. Maheo, Opportunistic Content-Based
Dissemination in DisconnectedMobile Ad Hoc Networks, in IEEE
UBICOM07, November 2007, pp. 4954.
[15] S. Y. Oh, D. Lau, and M. Gerla, Content Centric Networking
in Tactical and EmergencyMANETs, in Wireless days, IFIP 2010,
Venice, Italy, 2010, pp. 15.
[16] B. Etefia and L. Zhang, Named Data Networking for Military
Communication Systems,in IEEE Aerospace Conference, Big Sky, MT,
USA, March 2012, pp. 17.
[17] J. Wang, R. Wakikawa, R. Kuntz, R. Vuyyuru, and L. Zhang,
Data Naming in Vehicle-to-Vehicle Communications, in IEEE INFOCOM12
Workshop on Emerging DesignChoices in Name-Oriented Networking,
March 2012.
[18] M. Amadeo and C. Campolo and A. Molinaro, Content-Centric
Networking: is that aSolution for Upcoming Vehicular Networks? in
ACM VANET12, June 2012.
[19] M. Amadeo, C. Campolo, A. Molinaro, and N. Mitton, Named
Data Networking: aNatural Design for Data Collection in Wireless
Sensor Networks, in IFIP Wireless Days,Valencia, Spain, 2013.
[20] N.-T. Dinh and Y. Kim, Potential of information-centric
wireless sensor and actor net-working, in International Conference
on Computing, Management and Telecommuni-cations (ComManTel),
2013.
[21] Z. Ren, M. A. Hail, and H. Hellbruck, CCN-WSN - a
lightweight, flexible Content-Centric Networking Protocol for
Wireless Sensor Networks, in SSNIP 2013, Melbourne,Australia, April
2013.
[22] B. Saadallah, A. Lahmadi, and O. Festor, CCNx for Contiki:
Implementation Details,INRIA, Tech. Rep. RT-0432, November
2012.
[23] J. Meijers, M. Amadeo, C. Campolo, A. Molinaro, S.
Paratore, G. Ruggeri, and M. Booy-sen, A Two-Tier Content-Centric
Architecture for Wireless Sensor Networks, in IEEEICNP13,
Gottingen, Germany, 2013.
[24] G. Grassi, D. Pesavento, L. Wang, G. Pau, R. Vuyyuruc, R.
Wakikawac, and L. Zhang,Vehicular inter-networking via named data,
ACM SIGMOBILE Mobile Computingand Communications Review, vol. 17,
no. 3, 2013.
21
-
[25] Y.-T. Yu, R. B. Dilmaghani, S. Calo, M. Y. Sanadidi, and M.
Gerla, Interest Propaga-tion in Named Data MANETs, in IEEE ICNC13,
San Diego, CA, January 2013.
[26] G. Arnould, D. Khadraoui, and Z. Habbas, A Self-Organizing
Content Centric NetworkModel for Hybrid Vehicular Ad Hoc Networks,
in ACM DIVANet11, Miami, Florida,October 2011.
[27] L. Wang, A. Afanasyev, R. Kunts, R. Vuyyuru, R. Wakikawa,
and L. Zhang, RapidTraffic Information Dissemination Using Named
Data, in ACM NoM12), June 2012.
[28] M. Amadeo, C. Campolo, and A. Molinaro, CRoWN:
Content-Centric Networking inVehicular Ad Hoc Networks, IEEE
Communications Letters, vol. 16, no. 9, 2012.
[29] P. T. Fard and V. Leung, A Content Centric Approach to
Dissemination of Informa-tion in Vehicular Networks, in Second ACM
International Symposium on Design andAnalysis of Intelligent
Vehicular Networks and Applications (DIVANet12), 2012.
[30] M. Amadeo, C. Campolo, and A. Molinaro, Enhancing
Content-Centric Networking forVehicular Environments, Elsevier
Computer Networks, vol. 57, no. 16, 2013.
[31] M. Amadeo and C. Campolo and A. Molinaro, Design and
Analysis of a Transport-LevelSolution for Content-Centric VANETs,
in IEEE ICC Workshops, Budapest, Hungary,June 2013.
[32] J. Wang, R. Wakikawa, and L. Zhang, DMND: Collecting Data
from Mobiles UsingNamed Data, in IEEE Vehicular Networking
Conference, December 2010.
[33] Y.-T. Yu, X. Li, M. Gerla, and M. Sanadidi, Scalable vanet
content routing using hier-archical bloom filters, in Wireless
Communications and Mobile Computing Conference(IWCMC), 2013 9th
International. IEEE, 2013, pp. 16291634.
[34] B. Han, X. Wang, N. Choi, T. T. Kwon, and Y. Choi,
AMVS-NDN: Adaptive MobileVideo Streaming and Sharing in Wireless
Named Data Networking, in IEEE INFOCOMNOMEN Workshop, Turin, Italy,
2013.
[35] A. Detti, M. Pomposini, N. Blefari-Melazzi, S. Salsano, and
A. Bragagnini, Ooadingcellular networks with Information-Centric
Networking: the case of video streaming, inIEEE WoWMoM, 2012, pp.
13.
[36] M. Meisel, V. Pappas, and L. Zhang, Listen First, Broadcast
Later: Topology-agnosticForwarding Under High Dynamics, in Annual
Conference of International TechnologyAlliance in Network and
Information Science, September 2010.
[37] M. Amadeo, A. Molinaro, and G. Ruggeri, E-CHANET: Routing,
Forwarding andTransport in Information-Centric Multihop Wireless
Networks, Elsevier ComputerCommunications, vol. 36, no. 7,
2013.
[38] F. Angius, G. Pau, and M. Gerla, BLOOGO: BLOOm filter based
GOssip algorithmfor wireless NDN, in ACM NoM12, June 2012.
[39] F. Angius, A. Bhiday, M. Gerla, and G. Pau, MADN Multipath
Ad-hoc Data Networkprototype and experiments, in IEEE IWCMC13,
Cagliary, Italy, 2013.
[40] M. Varvello, I. Rimac, U. Lee, L. Greenwald, and V. Hilt,
On the Design of Content-Centric MANETs, in IEEE/IFIP WONS, January
2011.
[41] Y. Lu, B. Zhou, L.-C. Tung, M. Gerla, A. Ramesh, and L.
Nagaraja, Energy-efficientcontent retrieval in mobile cloud, in
Proceedings of the second ACM SIGCOMM work-shop on Mobile cloud
computing, ser. MCC 13. ACM, 2013.
[42] C. Anastasiades, A. Uruqi, and T. Braun, Content Discovery
in Opportunistic Content-Centric Networks, in IEEE Local Computer
Networks Workshops, October 2012.
[43] S.-B. Lee, S. H. Y. Wong, K.-W. Lee, and S. Lu, Content
Management in a Mobile AdHoc Network: Beyond Opportunistic
Strategy, in IEEE INFOCOM 11, April 2011,pp. 266270.
[44] Y. Lu, Z. Wang, Y. Yu, R. Fan, and M. Gerla, Social network
based security scheme inmobile information-centric network, in
Med-Hoc-Net, June 2013.
[45] P. Sharma, D. Souza, E. Fiore, J. Gottschalk, and D.
Marquis, A Case for MANET-Aware Content Centric Networking of
Smartphones, in IEEE WoWMoM, June 2012.
[46] R. Chiocchetti, D. Rossi, and G. Rossini, SCALE: a
Content-Centric MANET, in IEEEINFOCOM 13, Turin, April 2013.
[47] L. Zhang et al., Named Data Networking (NDN) Project, PARC,
Tech. Rep. NDN-0001, October 2010.
22
-
[48] L. Wang et al., OSPFN: An OSPF Based Routing Protocol for
Named Data Network-ing, NDN Project, Tech. Rep. NDN-0003, July
2012.
[49] C. Yi et al., A case for stateful forwarding plane,
Elsevier Computer Communications,vol. 36, no. 7, April 2013.
[50] O. Tonguz, N. Wisitpongphan, J. Parikh, F. Bai, P.
Mudalige, and V. Sadekar, On theBroadcast Storm Problem in Ad Hoc
Wireless Networks, in Broadband Communica-tions, Networks, and
Systems (BROADNETS), San Jose, CA, October 2006.
[51] G. Rossini and D. Rossi, Evaluating CCN multi-path interest
forwarding strategies,Computer Communications, vol. 36, no. 7,
2013.
[52] W. K. Chai, D. He, I. Psaras, and G. Pavlou, Cache less for
more in Information-Centric Networks (extended version), Computer
Communications, vol. 36, no. 7, 2013.
[53] A. Afanasyev, P. Mahadevan, I. Moiseenko, E. Uzun, and L.
Zhang, Interest FloodingAttack and Countermeasures in Named Data
Networking, in IFIP Networking, 2013.
[54] J. V. D. Merwe, D. Dawoud, and S. McDonald, A survey on
peer-to-peer key manage-ment for mobile ad hoc networks, ACM CSUR,
vol. 39, no. 1, p. 1, 2007.
[55] V. Jacobson, Congestion Avoidance and Control, in
SIGCOMM88, New York, NY,USA, 1988.
[56] C. Tsilopoulos, G. Xylomenos, Supporting Diverse Traffic
Types in Information CentricNetworks, PACM SIGCOMM workshop on
Information-centric networking (ICN11),Toronto, Canada, August
2011.
[57] A. Carzaniga, M. Papalini, and A. L. Wolf, Content-Based
Publish/Subscribe Net-working and Information-Centric Networking,
in ACM SIGCOMM Workshop onInformation-Centric Networking (ICN11),
Toronto, Canada, August 2011.
[58] C. Yao, L. Fan, Z. Yan, and Y. Xiang, Long term interest
for real-time applications inthe named data network, in ACM
AsiaFI12, Kioto, Japan, August 2012.
[59] The Network Simulator-3 (ns-3), http://www.nsnam.org/.[60]
A. Afanasyev, I. Moiseenko, and L. Zhang, ndnSIM: NDN simulator for
NS-3, NDN
Project, Tech. Rep. NDN-0005, July 2012.[61] CCNx Project,
http://www.ccnx.org.[62] A. Attam and I. Moiseenkoy, NDNBlue: NDN
over Bluetooth, Tech. Rep. NDN-0015,
2013.[63] I. Cianci, L. A. Grieco, and G. Boggia, CCN - Java
Opensource Kit EmulatoR for
Wireless Ad Hoc Networks, in ACM CFI12, Seoul, Korea, September
2012.[64] L. Breslau, P. Cao, L. Fan, G. Phillips, and S. Shenker,
Securing Instrumented Envi-
ronments over Content-Centric Networking: the Case of Lighting
Control and NDN, inIEEE Infocom NOMEN Workshop, Turin, Italy,
2013.
[65] M. Gerla, Vehicular Cloud Computing, in IEEE Med-Hoc-Net,
2012.[66] B. Mathieu, P. Truong, W. You, and J.-F. Peltier,
Information-Centric Networking:
a Natural Design for Social Network Applications, IEEE
Communications Magazine,vol. 50, no. 7, pp. 4451, 2012.
23