ICNRG                                                         J. Seedorf
Internet-Draft                 HFT Stuttgart - Univ. of Applied Sciences
Intended status: Informational                           M. Arumaithurai
Expires: August 2, 2020                         University of Goettingen
                                                               A. Tagami
                                                      KDDI Research Inc.
                                                         K. Ramakrishnan
                                                University of California
                                                      N. Blefari Melazzi
                                                  University Tor Vergata
                                                        January 30, 2020

        Research Directions for Using ICN in Disaster Scenarios


   Information Centric Networking (ICN) is a new paradigm where the
   network provides users with named content, instead of communication
   channels between hosts.  This document outlines some research
   directions for Information Centric Networking with respect to
   applying ICN approaches for coping with natural or human-generated,
   large-scale disasters.  This document is a product of the
   Information-Centric Networking Research Group (ICNRG).

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   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Disaster Scenarios  . . . . . . . . . . . . . . . . . . . . .   4
   3.  Research Challenges and Benefits of ICN . . . . . . . . . . .   5
     3.1.  High-Level Research Challenges  . . . . . . . . . . . . .   5
     3.2.  How ICN can be Beneficial . . . . . . . . . . . . . . . .   7
     3.3.  ICN as Starting Point vs. Existing DTN Solutions  . . . .   8
   4.  Use Cases and Requirements  . . . . . . . . . . . . . . . . .   9
   5.  ICN-based Research Approaches and Open Research Challenges  .  10
     5.1.  Suggested ICN-based Research Approaches . . . . . . . . .  10
     5.2.  Open Research Challenges  . . . . . . . . . . . . . . . .  13
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   7.  Conclusion  . . . . . . . . . . . . . . . . . . . . . . . . .  15
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  16
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  16
   Appendix A.  Acknowledgment . . . . . . . . . . . . . . . . . . .  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19

1.  Introduction

   This document summarizes some research challenges for coping with
   natural or human-generated, large-scale disasters.  In particular,
   the document discusses potential research directions for applying
   Information Centric Networking (ICN) to address these challenges.

   There are existing research and standardization approaches (for
   instance, see further the work and discussions in the concluded IRTF
   DTN Research Group [dtnrg] and in the IETF DTN Working Group [dtnwg])
   and an IRTF stream Experimental RFC [RFC5050] for Delay/Disruption
   Tolerant Networking (DTN), which is a key necessity for communicating
   in the disaster scenarios we are considering in this document (see
   further Section 3.1 ).  'Disconnection tolerance' can thus be
   achieved with these existing DTN approaches.  However, while these
   approaches can provide independence from an existing communication
   infrastructure (which indeed may not work anymore after a disaster

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   has happened), ICN offers as key concepts suitable naming schemes and
   multicast communication which together enable many key (publish/
   subscribe-based) use cases for communication after a disaster (e.g.
   message prioritisation, one-to-many delivery of important messages,
   or group communication among rescue teams, see further Section 4 ).
   One could add such features to existing DTN protocols and solutions;
   however, in this document we explore the use of ICN as starting point
   for building a communication architecture that supports (somewhat
   limited) communication capabilities after a disaster.  We discuss the
   relationship between the ICN approaches (for enabling communication
   after a disaster) discussed in this document with existing work from
   the DTN community in more depth in Section 3.3 .

   'Emergency Support and Disaster Recovery' is also listed among the
   ICN Baseline Scenarios in [RFC7476] as a potential scenario that 'can
   be used as a base for the evaluation of different information-centric
   networking (ICN) approaches so that they can be tested and compared
   against each other while showcasing their own advantages' [RFC7476] .
   In this regard, this document complements [RFC7476] by investigating
   the use of ICN approaches for 'Emergency Support and Disaster
   Recovery' in depth and discussing the relationship to existing work
   in the DTN community.

   This document focuses on ICN-based approaches that can enable
   communication after a disaster.  These approaches reside mostly on
   the networking layer.  Other solutions for 'Emergency Support and
   Disaster Recovery', e.g., on the application layer, may complement
   the ICN-based networking approaches discussed in this document and
   expand the solution space for enabling communications among users
   after a disaster.  In fact, addressing the use cases explored in this
   document would require corresponding applications that would exploit
   the discussed ICN-benefits on the networking layer for users.
   However, the discussion of applications or solutions outside of the
   networking layer are outside the scope of this document.

   This document represents the consensus of the Information-Centric
   Networking Research Group (ICNRG); it is not an IETF product and it
   does not define a standard.  It has been reviewed extensively by the
   ICN Research Group (RG) members active in the specific areas of work
   covered by the document.

   Section 2 gives some examples of what can be considered a large-scale
   disaster and what the effects of such disasters on communication
   networks are.  Section 3 outlines why ICN can be beneficial in such
   scenarios and provides a high-level overview on corresponding
   research challenges.  Section 4 describes some concrete use cases and
   requirements for disaster scenarios.  In Section 5 , some concrete
   ICN-based solutions approaches are outlined.

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2.  Disaster Scenarios

   An enormous earthquake hit Northeastern Japan (Tohoku areas) on March
   11, 2011, and caused extensive damages including blackouts, fires,
   tsunamis and a nuclear crisis.  The lack of information and means of
   communication caused the isolation of several Japanese cities.  This
   impacted the safety and well-being of residents, and affected rescue
   work, evacuation activities, and the supply chain for food and other
   essential items.  Even in the Tokyo area that is 300km away from the
   Tohoku area, more than 100,000 people became 'returner' refugees, who
   could not reach their homes because they had no means of public
   transportation (the Japanese government has estimated that more than
   6.5 million people would become returner refugees if such a
   catastrophic disaster were to hit the Tokyo area).

   That earthquake in Japan also showed that the current network is
   vulnerable to disasters.  Mobile phones have become the lifelines for
   communication including safety confirmation: Besides (emergency)
   phone calls, services in mobile networks commonly being used after a
   disaster include network disaster SMS notifications (or SMS 'Cell
   Broadcast' [cellbroadcast]), available in most cellular networks.
   The aftermath of a disaster puts a high strain on available resources
   due to the need for communication by everyone.  Authorities such as
   the President/Prime-Minister, local authorities, Police, fire
   brigades, and rescue and medical personnel would like to inform the
   citizens of possible shelters, food, or even of impending danger.
   Relatives would like to communicate with each other and be informed
   about their wellbeing.  Affected citizens would like to make
   enquiries of food distribution centres, shelters or report trapped
   and missing people to the authorities.  Moreover, damage to
   communication equipment, in addition to the already existing heavy
   demand for communication highlights the issue of fault-tolerance and
   energy efficiency.

   Additionally, disasters caused by humans such as a terrorist attack
   may need to be considered, i.e. disasters that are caused
   deliberately and willfully and have the element of human intent.  In
   such cases, the perpetrators could be actively harming the network by
   launching a Denial-of-Service attack or by monitoring the network
   passively to obtain information exchanged, even after the main
   disaster itself has taken place.  Unlike some natural disasters that
   are to a small extent predictable using weather forecasting
   technologies, may have a slower onset, and occur in known
   geographical regions and seasons, terrorist attacks almost always
   occur suddenly without any advance warning.  Nevertheless, there
   exist many commonalities between natural and human-induced disasters,
   particularly relating to response and recovery, communication, search
   and rescue, and coordination of volunteers.

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   The timely dissemination of information generated and requested by
   all the affected parties during and the immediate aftermath of a
   disaster is difficult to provide within the current context of global
   information aggregators (such as Google, Yahoo, Bing etc.) that need
   to index the vast amounts of specialized information related to the
   disaster.  Specialized coverage of the situation and timely
   dissemination are key to successfully managing disaster situations.
   We believe that network infrastructure capabilities provided by
   Information Centric Networks can be suitable, in conjunction with
   application and middleware assistance.

3.  Research Challenges and Benefits of ICN

3.1.  High-Level Research Challenges

   Given a disaster scenario as described in Section 2, on a high-level
   one can derive the following (incomplete) list of corresponding
   technical challenges:

   o  Enabling usage of functional parts of the infrastructure, even
      when these are disconnected from the rest of the network: Assuming
      that parts of the network infrastructure (i.e.  cables/links,
      routers, mobile bases stations, ...) are functional after a
      disaster has taken place, it is desirable to be able to continue
      using such components for communication as much as possible.  This
      is challenging when these components are disconnected from the
      backhaul, thus forming fragmented networks.  This is especially
      true for today's mobile networks which are comprised of a
      centralised architecture, mandating connectivity to central
      entities (which are located in the core of the mobile network) for
      communication.  But also in fixed networks, access to a name
      resolution service is often necessary to access some given

   o  Decentralised authentication, content integrity, and trust: In
      mobile networks, users are authenticated via central entities.
      While special services important in a disaster scenario exist and
      may work without authentication (such as SMS 'Cell Broadcast'
      [cellbroadcast] or emergency calls), user-to-user (or user-to-
      authorities) communication is normally not possible without being
      authenticated via a central entity in the network.  In order to
      communicate in fragmented or disconnected parts of a mobile
      network, the challenge of decentralising user authentication
      arises.  Independently of the network being fixed or mobile, data
      origin authentication and verifying the correctness of content
      retrieved from the network may be challenging when being 'offline'
      (e.g., potentially disconnected from content publishers as well as
      from servers of a security infrastructure which can provide

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      missing certificates in a certificate chain or up-to-date
      information on revoked keys/certificates).  As the network
      suddenly becomes fragmented or partitioned, trust models may shift
      accordingly to the change in authentication infrastructure being
      used (e.g., one may switch from a PKI to a web-of-trust model such
      as PGP).  Note that blockchain-based approaches are in most cases
      likely not suitable for the disaster scenarios considered in this
      document, as the communication capabilities needed to find
      consensus for a new block as well as for retrieving blocks at
      nodes presumably will not be available (or too excessive for the
      remaining infrastructure) after a disaster.

   o  Delivering/obtaining information and traffic prioritization in
      congested networks: Due to broken cables, failed routers, etc., it
      is likely that in a disaster scenario the communication network
      has much less overall capacity for handling traffic.  Thus,
      significant congestion can be expected in parts of the
      infrastructure.  It is therefore a challenge to guarantee message
      delivery in such a scenario.  This is even more important as in
      the case of a disaster aftermath, it may be crucial to deliver
      certain information to recipients (e.g. warnings to citizens) with
      higher priority than other content.

   o  Delay/Disruption Tolerant Approach: Fragmented networks make it
      difficult to support direct end-to-end communication with small or
      no delay.  However, communication in general and especially during
      a disaster can often tolerate some form of delay.  E.g., in order
      to know if someone's relatives are safe or not, a corresponding
      emergency message need not necessarily be supported in an end-to-
      end manner, but would also be helpful to the human recipient if it
      can be tranported in a hop-by-hop fashion with some delay.  For
      these kinds of use-cases, it is sufficient to improve
      communication resilience in order to deliver such important

   o  Energy Efficiency: Long-lasting power outages may lead to
      batteries of communication devices running out, so designing
      energy-efficient solutions is very important in order to maintain
      a usable communication infrastructure.

   o  Contextuality: Like any communication in general, disaster
      scenarios are inherently contextual.  Aspects of geography, the
      people affected, the rescue communities involved, the languages
      being used and many other contextual aspects are highly relevant
      for an efficient realization of any rescue effort and, with it,
      the realization of the required communication.

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3.2.  How ICN can be Beneficial

   Several aspects of ICN make related approaches attractive candidates
   for addressing the challenges described in Section 3.1 . Below is an
   (incomplete) list of considerations why ICN approaches can be
   beneficial to address these challenges:

   o  Routing-by-name: ICN protocols natively route by named data
      objects and can identify objects by names, effectively moving the
      process of name resolution from the application layer to the
      network layer.  This functionality is very handy in a fragmented
      network where reference to location-based, fixed addresses may not
      work as a consequence of disruptions.  For instance, name
      resolution with ICN does not necessarily rely on the reachability
      of application-layer servers (e.g.  DNS resolvers).  In highly
      decentralised scenarios (e.g. in infrastructureless, opportunistic
      environments) the ICN routing-by-name paradigm effectively may
      lead to a 'replication-by-name' approach, where content is
      replicated depending on its name.

   o  Integrity and Authentication of named data objects: ICN is built
      around the concept of named data objects.  Several proposals exist
      for integrating the concept of 'self-certifying data' into a
      naming scheme (see e.g.  [RFC6920]).  With such approaches, object
      integrity of data retrieved from the network can be verified
      without relying on a trusted third party or PKI.  In addition,
      given that the correct object name is known, such schemes can also
      provide data origin authentication (see for instance Section 8.3.
      in [RFC6920])

   o  Content-based access control: ICN promotes a data-centric
      communication model which naturally supports content-based
      security (e.g. allowing access to content only to a specific user
      or class of users) as in ICN - if desired - not the communication
      channel is secured (encrypted) but the content itself.  This
      functionality could facilitate trusted communications among peer
      users in isolated areas of the network where a direct
      communication channel may not always or continuously exist.

   o  Caching: Caching content along a delivery path is an inherent
      concept in ICN.  Caching helps in handling huge amounts of
      traffic, and can help to avoid congestion in the network (e.g.
      congestion in backhaul links can be avoided by delivering content
      from caches at access nodes).

   o  Sessionless: ICN does not require full end-to-end connectivity.
      This feature facilitates a seemless aggregation between a normal

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      network and a fragmented network, which needs DTN-like message

   o  Potential to run traditional IP-based services (IP-over-ICN):
      While ICN and DTN promote the development of novel applications
      that fully utilize the new capabilities of the ICN/DTN network,
      work in [Trossen2015] has shown that an ICN-enabled network can
      transport IP-based services, either directly at IP or even at HTTP
      level.  With this, IP- and ICN/DTN-based services can coexist,
      providing the necessary support of legacy applications to affected
      users, while reaping any benefits from the native support for ICN
      in future applications.

   o  Opportunities for traffic engineering and traffic prioritization:
      ICN provides the possibility to perform traffic engineering based
      on the name of desired content.  This enables priority based
      replication depending on the scope of a given message [Psaras2014]
      . In addition, as [Trossen2015] , among others, have pointed out,
      the realization of ICN services and particularly of IP-based
      services on top of ICN provide further traffic engineering
      opportunities.  The latter not only relate to the utilization of
      cached content, as outlined before, but to the ability to flexbily
      adapt to route changes (important in unreliable infrastructure
      such as in disaster scenarios), mobility support without anchor
      points (again, important when parts of the infrastructure are
      likely to fail) and the inherent support for multicast and
      multihoming delivery.

3.3.  ICN as Starting Point vs. Existing DTN Solutions

   There has been quite some work in the DTN (Delay Tolerant Networking)
   community on disaster communication (for instance, see further the
   work and discussions in the concluded IRTF DTN Research Group [dtnrg]
   and in the IETF DTN Working Group [dtnwg]).  However, most DTN work
   lacks important features such as publish/subscribe (pub/sub)
   capabilities, caching, multicast delivery, and message prioritisation
   based on content types, which are needed in the disaster scenarios we
   consider.  One could add such features to existing DTN protocols and
   solutions, and indeed individual proposals for adding such features
   to DTN protocols have been made (e.g.  [Greifenberg2008] [Yoneki2007]
   propose the use of a pub/sub-based multicast distribution
   infrastructure for DTN-based opportunistic networking environments).

   However, arguably ICN---having these intrinsic properties (as also
   outlined above)---makes a better starting point for building a
   communication architecture that works well before and after a
   disaster.  For a disaster-enhanced ICN system this would imply the
   following advantages: a) ICN data mules would have built-in caches

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   and can thus return content for interests straight on, b) requests do
   not necessarily need to be routed to a source (as with existing DTN
   protocols), instead any data mule or end-user can in principle
   respond to an interest, c) built-in multi-cast delivery implies
   energy-efficient large-scale spreading of important information which
   is crucial in disaster scenarios, and d) pub/sub extension for
   popular ICN implementations exist [COPSS2011] which are very suitable
   for efficient group communication in disasters and provide better
   reliability, timeliness and scalability as compared to existing pub/
   sub approaches in DTN [Greifenberg2008] [Yoneki2007] .

   Finally, most DTN routing algorithms have been solely designed for
   particular DTN scenarios.  By extending ICN approaches for DTN-like
   scenarios, one ensures that a solution works in regular (i.e. well-
   connected) settings just as well (which can be important in reality,
   where a routing algorithm should work before and after a disaster).
   It is thus reasonable to start with existing ICN approaches and
   extend them with the necessary features needed in disaster scenarios.
   In any case, solutions for disaster scenarios need a combination of
   ICN-features and DTN-capabilities.

4.  Use Cases and Requirements

   This Section describes some use cases for the aforementioned disaster
   scenario (as outlined in Section 2 ) and discusses the corresponding
   technical requirements for enabling these use cases.

   o  Delivering Messages to Relatives/Friends: After a disaster
      strikes, citizens want to confirm to each other that they are
      safe.  For instance, shortly after a large disaster (e.g.,
      Earthquake, Tornado), people have moved to different refugee
      shelters.  The mobile network is not fully recovered and is
      fragmented, but some base stations are functional.  This use case
      imposes the following high-level requirements: a) People must be
      able to communicate with others in the same network fragment, b)
      people must be able to communicate with others that are located in
      different fragmented parts of the overall network.  More
      concretely, the following requirements are needed to enable the
      use case: a) a mechanism for a scalable message forwarding scheme
      that dynamically adapts to changing conditions in disconnected
      networks, b) DTN-like mechanisms for getting information from
      disconnected island to another disconnected island, c) source
      authentication and content integrity so that users can confirm
      that the messages they receive are indeed from their relatives or
      friends and have not been tampered with, and d) the support for
      contextual caching in order to provide the right information to
      the right set of affected people in the most efficient manner.

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   o  Spreading Crucial Information to Citizens: State authorities want
      to be able to convey important information (e.g. warnings, or
      information on where to go or how to behave) to citizens.  These
      kinds of information shall reach as many citizens as possible.
      i.e. Crucial content from legal authorities shall potentially
      reach all users in time.  The technical requirements that can be
      derived from this use case are: a) source authentication and
      content integrity, such that citizens can confirm the correctness
      and authenticity of messages sent by authorities, b) mechanisms
      that guarantee the timeliness and loss-free delivery of such
      information, which may include techniques for prioritizing certain
      messages in the network depending on who sent them, and c) DTN-
      like mechanisms for getting information from disconnected island
      to another disconnected island.

   It can be observed that different key use cases for disaster
   scenarios imply overlapping and similar technical requirements for
   fulfilling them.  As discussed in Section 3.2 , ICN approaches are
   envisioned to be very suitable for addressing these requirements with
   actual technical solutions.  In [Robitzsch2015] , a more elaborate
   set of requirements is provided that addresses, among disaster
   scenarios, a communication infrastructure for communities facing
   several geographic, economic and political challenges.

5.  ICN-based Research Approaches and Open Research Challenges

   This section outlines some ICN-based research approaches that aim at
   fulfilling the previously mentioned use cases and requirements
   (Section 5.1).  Most of these works provide proof-of-concept type
   soluions, addressing singular challenges.  Thus, several open issues
   remain which are summarized in Section 5.2.

5.1.  Suggested ICN-based Research Approaches

   The research community has investigated ICN-based solutions to
   address the aforementioned challenges in disaster scenarios.
   Overall, the focus is on delivery of messages and not real-time
   communication.  While most probably users would like to conduct real-
   time voice/video calls after a disaster, in the extreme scenario we
   consider (with users being scattered over different fragmented
   networks, see Section 2), somewhat delayed message delivery appears
   to be inevitable, and full-duplex real-time communication seems
   infeasible to achieve (unless users are in close proximity).  Thus,
   the assumption is that - for a certain amount of time at least (i.e.
   the initial period until the regular communication infrastructure has
   been repaired) - users would need to live with message delivery and
   publish/subscribe services but without real-time communication.
   Note, however, that a) in principle ICN can support VoIP calls; thus,

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   if users are in close proximity, (duplex) voice communication via ICN
   is possible [Gusev2015], and b) delayed message delivery can very
   well include (recorded) voice messages.

   o  ICN 'data mules': To facilitate the exchange of messages between
      different network fragments, mobile entitites can act as ICN 'data
      mules' which are equipped with storage space and move around the
      disaster-stricken area gathering information to be disseminated.
      As the mules move around, they deliver messages to other
      individuals or points of attachment to different fragments of the
      network.  These 'data mules' could have a pre-determined path (an
      ambulance going to and from a hospital), a fixed path (drone/robot
      assigned specifically to do so) or a completely random path
      (doctors moving from one camp to another).  An example of a many-
      to-many communication service for fragmented networks based on ICN
      data mules has been proposed in [Tagami2016].

   o  Priority-dependent or popularity-dependent name-based replication:
      By allowing spatial and temporal scoping of named messages,
      priority based replication depending on the scope of a given
      message is possible.  Clearly, spreading information in disaster
      cases involves space and time factors that have to be taken into
      account as messages spread.  A concrete approach for such scope-
      based prioritisation of ICN messages in disasters, called 'NREP',
      has been proposed [Psaras2014] , where ICN messages have
      attributes such as user-defined priority, space, and temporal-
      validity.  These attributes are then taken into account when
      prioritizing messages.  In [Psaras2014] , evaluations show how
      this approach can be applied to the use case 'Delivering Messages
      to Relatives/Friends' decribed in Section 4.  In [Seedorf2016], a
      scheme is presented that enables to estimate the popularity of ICN
      interest messages in a completely decentralized manner among data
      mules in a scenario with random, unpredictable movements of ICN
      data mules.  The approach exploits the use of nonces associated
      with end user requests, common in most ICN architectures.  It
      enables for a given ICN data mule to estimate the overall
      popularity (among end-users) of a given ICN interest message.
      This enables data mules to optimize content dissemination with
      limited caching capabilities by prioritizing interests based on
      their popularity.

   o  Information Resilience through Decentralised Forwarding: In a
      dynamic or disruptive environment, such as the aftermath of a
      disaster, both users and content servers may dynamically join and
      leave the network (due to mobility or network fragmentation).
      Thus, users might attach to the network and request content when
      the network is fragmented and the corresponding content origin is
      not reachable.  In order to increase information resilience,

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      content cached both in in-network caches and in end-user devices
      should be exploited.  A concrete approach for the exploitation of
      content cached in user devices is presented in [Sourlas2015] . The
      proposal in [Sourlas2015] includes enhancements to the NDN router
      design, as well as an alternative Interest forwarding scheme which
      enables users to retrieve cached content when the network is
      fragmented and the content origin is not reachable.  Evaluations
      show that this approach is a valid tool for the retrieval of
      cached content in disruptive cases and can be applied to tackle
      the challenges presented in Section 3.1 .

   o  Energy Efficiency: A large-scale disaster causes a large-scale
      blackout and thus a number of base stations (BSs) will be operated
      by their batteries.  Capacities of such batteries are not large
      enough to provide cellular communication for several days after
      the disaster.  In order to prolong the batteries' life from one
      day to several days, different techniques need to be explored:
      Priority control, cell-zooming, and collaborative upload.  Cell
      zooming switches-off some of the BSs because switching-off is the
      only way to reduce power consumed at the idle time.  In cell
      zooming, areas covered by such inactive BSs are covered by the
      active BSs.  Collaborative communication is complementary to cell
      zooming and reduces power proportional to a load of a BS.  The
      load represents cellular frequency resources.  In collaborative
      communication, end-devices delegate sending and receiving messages
      to and from a base station to a representative end-device of which
      radio propagation quality is better.  The design of an ICN-based
      publish/subscribe protocol that incorporates collaborative upload
      is ongoing work.  In particular, the integration of collaborative
      upload techniques into the COPSS (Content Oriented Publish/
      Subscribe System)} framework is envisioned [COPSS2011] .

   o  Data-centric confidentiality and access control: In ICN, the
      requested content is not anymore associated to a trusted server or
      an endpoint location, but it can be retrieved from any network
      cache or a replica server.  This calls for 'data-centric'
      security, where security relies on information exclusively
      contained in the message itself, or, if extra information provided
      by trusted entities is needed, this should be gathered through
      offline, asynchronous, and non interactive communication, rather
      than from an explicit online interactive handshake with trusted
      servers.  The ability to guarantee security without any online
      entities is particularly important in disaster scenarios with
      fragmented networks.  One concrete cryptographic technique is
      'Ciphertext-Policy Attribute Based Encryption' (CP-ABE), allowing
      a party to encrypt a content specifying a policy, which consists
      in a Boolean expression over attributes, that must be satisfied by
      those who want to decrypt such content.  Such encryption schemes

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      tie confidentiality and access-control to the transferred data,
      which can be transmitted also in an unsecured channel.  These
      schemes enable the source to specify the set of nodes allowed to
      later on decrypt the content during the encryption process.

   o  Decentralised authentication of messages: Self-certifying names
      provide the property that any entity in a distributed system can
      verify the binding between a corresponding public key and the
      self-certifying name without relying on a trusted third party.
      Self-certifying names thus provide a decentralized form of data
      origin authentication.  However, self-certifying names lack a
      binding with a corresponding real-world identity.  Given the
      decentralised nature of a disaster scenario, a PKI-based approach
      for binding self-certifying names with real-world identities is
      not feasible.  Instead, a Web-of-Trust can be used to provide this
      binding.  Not only are the cryptographic signatures used within a
      Web-of-Trust independent of any central authority; there are also
      technical means for making the inherent trust relationships of a
      Web-of-Trust available to network entities in a decentralised,
      'offline' fashion, such that information received can be assessed
      based on these trust relationships.  A concrete scheme for such an
      approach has been published in [Seedorf2014] , where also concrete
      examples for fulfilling the use case 'Delivering Messages to
      Relatives/Friends' with this approach are given.

5.2.  Open Research Challenges

   The proposed solutions in Section 5.1 investigate how ICN approaches
   can in principal address some of the outlined challenges.  However,
   several research challenges remain open and still need to be
   addressed.  The following (incomplete) list summarizes some
   unanswered research questions and items that are being investigated
   by researchers:

   o  Evaluation of the proposed mechanisms (and their scalability) in
      realistic large-scale testbeds with actual, mature implementations
      (compared to simulations or emulations)

   o  Specifying for each mechanism suggested to what exact extent ICN
      deployment in the network and at user equipment is required or
      would be necessary, before and after a disaster.

   o  How to best use DTN and ICN approaches for an optimal overall
      combination of techniques?

   o  How do data-centric encryption schemes scale and perform in large-
      scale, realistic evaluations?

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   o  Build and test real (i.e. not early-stage prototypes) ICN data
      mules by means of implementation and integration with lower layer
      hardware; conduct evaluations of decentralised forwarding schemes
      in real environments with these actual ICN data mules

   o  How to derive concrete policies for ICN-style name-based
      prioritized spreading of information?

   o  Further investigate, develop, and verify mechanisms that address
      energy efficiency requirements for communication after a disaster

   o  How to properly disseminate authenticated object names to nodes
      (for decentralised integrity verification and authentication)
      before a disaster, or how to retrieve new authenticated object
      names by nodes during a disaster?

6.  Security Considerations

   This document does not define a new protocol (or protocol extension)
   or a particular mechanism, and therefore introduces no specific new
   security considerations.  General security considerations for
   Information-Centric Networking -- which also apply when using ICN
   networking techniques to communicate after a disaster -- are
   discussed in [RFC7945].

   The after-disaster communication scenario which is the focus of this
   document raises particular attention to decentralised authentication,
   content integrity, and trust as key research challenges (as outlined
   in Section 3.1).  The corresponding use cases and ICN-based research
   approaches discussed in this document thus imply certain security
   requirements.  In particular data origin authentication, data
   integrity, and access control are key requirements for many use cases
   in the aftermath of a disaster (see Section 4).

   In principle, the kinds of disasters discussed in this document can
   happen as a result of a natural disaster, accident or by human-error.
   However, also intentional actions can cause such a disaster (e.g., a
   terrorist attack, as mentioned in Section 2).  In this case, i.e.,
   intentionally caused disasters by attackers, special attention needs
   to be paid when re-enabling communications as temporary, somewhat un-
   reliable communications with potential limited security features may
   be anticipated and abused by attackers (e.g., to circulate false
   messages to cause further intentional chaos among the human
   population, to leverage this less secure infrastructure to refine
   targeting, or to track the responses of security/police forces).
   Potential solutions on how to cope with intentionally caused
   disasters by attackers and on how to enable a secure communications

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   infrastructure after such an intentionally caused disaster are out of
   scope of this document.

   The use of data-centric security schemes such as 'Ciphertext-Policy
   Attribute Based Encryption' (as mentioned in Section 5.1) which
   encrypt the data itself (and not the communication channel), in
   principle allows for the transmission of such encrypted data over an
   unsecured channel.  However, still metadata about the encrypted data
   being retrieved arises.  Such metadata may disclose sensitive
   information to a network-based attacker even if such an attacker
   cannot decrypt the content itself.

   This document has summarized research directions for addressing these
   challenges and requirements, such as efforts in data-centric
   confidentiality and access control as well as recent works for
   decentralised authentication of messages in a disaster-struck
   networking infrastructure with non-functional routing links and
   limited communication capabilities (see Section 5).

7.  Conclusion

   This document has outlined some research directions for Information
   Centric Networking (ICN) with respect to applying ICN approaches for
   coping with natural or human-generated, large-scale disasters.  The
   document has described high-level research challenges for enabling
   communication after a disaster has happened as well as a general
   rationale why ICN approaches could be beneficial to address these
   challenges.  Further, concrete use cases have been described and how
   these can be addressed with ICN-based approaches has been discussed.

   Finally, the document provided an overview of examples of existing
   ICN-based solutions that address the previously outlined research
   challenges.  These concrete solutions demonstrate that indeed the
   communication challenges in the aftermath of a disaster can be
   addressed with techniques that have ICN paradigms at their base,
   validating our overall reasoning.  However, further, more detailed
   challenges exist and more research is necessary in all areas
   discussed: efficient content distribution and routing in fragmented
   networks, traffic prioritization, security, and energy-efficiency.
   An incomplete, high-level list of such open research challenges has
   concluded the document.

   In order to deploy ICN-based solutions for disaster-aftermath
   communication in actual mobile networks, standardized ICN baseline
   protocols are a must: It is unlikely to expect all user equipment in
   a large-scale mobile network to be from the same vendor.  In this
   respect, the work being done in the IRTF ICNRG is very useful as it
   works towards standards for concrete ICN protocols that enable

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   interopability among solutions from different vendors.  These
   protocols - currently being standardized as IRTF stream Experimental
   specifications in the IRTF INCRG - provide a good foundation for
   deploying ICN-based disaster-aftermath communication and thereby
   addressing key use cases that arise in such situations (as outlined
   in this document).

8.  IANA Considerations

   This document requests no IANA actions.

9.  References

9.1.  Normative References

   [RFC5050]  Scott, K. and S. Burleigh, "Bundle Protocol
              Specification", RFC 5050, DOI 10.17487/RFC5050, November
              2007, <https://www.rfc-editor.org/info/rfc5050>.

   [RFC6920]  Farrell, S., Kutscher, D., Dannewitz, C., Ohlman, B.,
              Keranen, A., and P. Hallam-Baker, "Naming Things with
              Hashes", RFC 6920, DOI 10.17487/RFC6920, April 2013,

   [RFC7476]  Pentikousis, K., Ed., Ohlman, B., Corujo, D., Boggia, G.,
              Tyson, G., Davies, E., Molinaro, A., and S. Eum,
              "Information-Centric Networking: Baseline Scenarios",
              RFC 7476, DOI 10.17487/RFC7476, March 2015,

   [RFC7945]  Pentikousis, K., Ed., Ohlman, B., Davies, E., Spirou, S.,
              and G. Boggia, "Information-Centric Networking: Evaluation
              and Security Considerations", RFC 7945,
              DOI 10.17487/RFC7945, September 2016,

9.2.  Informative References

              Wikipedia, "Cell Broadcast - Wikipedia,
              https://en.wikipedia.org/wiki/Cell_Broadcast",  (online).

              Chen, J., Arumaithurai, M., Jiao, L., Fu, X., and K.
              Ramakrishnan, "COPSS: An Efficient Content Oriented
              Publish/Subscribe System",  Seventh ACM/IEEE Symposium on
              Architectures for Networking and Communications Systems
              (ANCS), 2011.

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   [dtnrg]    Fall, K. and J. Ott, "Delay-Tolerant Networking Research
              Group - DTNRG",  https://irtf.org/dtnrg.

   [dtnwg]    Fall, K. and J. Ott, "Delay/Disruption Tolerant Networking
              WG",  https://tools.ietf.org/wg/dtn/.

              Greifenberg, J. and D. Kutscher, "Efficient publish/
              subscribe-based multicast for opportunistic networking
              with self-organized resource utilization",  Advanced
              Information Networking and Applications-Workshops, 2008.

              Gusev, P. and J. Burke, "NDN-RTC: Real-Time
              Videoconferencing over Named Data Networking",  2nd ACM
              Conference on Information-Centric Networking (ICN 2015),
              Sep. 30 - Oct. 2, San Francisco, CA, USA.

              Psaras, I., Saino, L., Arumaithurai, M., Ramakrishnan, K.,
              and G. Pavlou, "Name-Based Replication Priorities in
              Disaster Cases",  2nd Workshop on Name Oriented Mobility
              (NOM), 2014.

              Robitzsch, S., Trossen, D., Theodorou, C., Barker, T., and
              A. Sathiaseel, "D2.1: Usage Scenarios and
              Requirements"",  H2020 project RIFE, public deliverable,

              Seedorf, J., Kutscher, D., and F. Schneider,
              "Decentralised Binding of Self-Certifying Names to Real-
              World Identities for Assessment of Third-Party Messages in
              Fragmented Mobile Networks",  2nd Workshop on Name
              Oriented Mobility (NOM), 2014.

              Seedorf, J., Kutscher, D., and B. Gill, "Decentralised
              Interest Counter Aggregation for ICN in Disaster
              Scenarios",  Workshop on Information Centric Networking
              Solutions for Real World Applications (ICNSRA), 2016.

              Sourlas, V., Tassiulas, L., Psaras, I., and G. Pavlou,
              "Information Resilience through User-Assisted Caching in
              Disruptive Content-Centric Networks",  14th IFIP
              NETWORKING, May 2015.

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              Tagami, A., Yagyu, T., Sugiyama, K., Arumaithurai, M.,
              Nakamura, K., Hasegawa, T., Asami, T., and K.
              Ramakrishnan, "Name-based Push/Pull Message Dissemination
              for Disaster Message Board",  The 22nd IEEE International
              Symposium on Local and Metropolitan Area Networks
              (LANMAN), 2016.

              Trossen, D., "IP over ICN - The better IP?",  2015
              European Conference onNetworks and Communications (EuCNC),
              June/July 2015, pp. 413 - 417.

              Yoneki, E., Hui, P., Chan, S., and J. Crowcroft, "A socio-
              aware overlay for publish/subscribe communication in delay
              tolerant networks",  Proceedings of the 10th ACM Symposium
              on Modeling, Analysis, and Simulation of Wireless and
              Mobile Systems, 2007.

Appendix A.  Acknowledgment

   The authors would like to thank Ioannis Psaras for useful comments.
   Also, the authors are grateful to Christopher Wood and Daniel Corujo
   for valuable feedback and suggestions on concrete text for improving
   the document.  Further, the authors would like to thank Joerg Ott and
   Dirk Trossen for valuable comments and input, in particular regarding
   existing work from the DTN community which is highly related to the
   ICN approaches suggested in this document.  Also, Akbar Rahman
   provided useful comments and usggestions, in particular regarding
   existing disaster warning mechanisms in today's mobile phone

   This document has been supported by the GreenICN project (GreenICN:
   Architecture and Applications of Green Information Centric Networking
   ), a research project supported jointly by the European Commission
   under its 7th Framework Program (contract no.  608518) and the
   National Institute of Information and Communications Technology
   (NICT) in Japan (contract no. 167).  The views and conclusions
   contained herein are those of the authors and should not be
   interpreted as necessarily representing the official policies or
   endorsements, either expressed or implied, of the GreenICN project,
   the European Commission, or NICT.  More information is available at
   the project web site http://www.greenicn.org/.

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Authors' Addresses

   Jan Seedorf
   HFT Stuttgart - Univ. of Applied Sciences
   Schellingstrasse 24
   Stuttgart  70174

   Phone: +49 711 8926 2801
   Fax:   +49 711 8926 2553
   Email: jan.seedorf@hft-stuttgart.de

   Mayutan Arumaithurai
   University of Goettingen
   Goldschmidt Str. 7
   Goettingen   37077

   Phone: +49 551 39 172046
   Fax:   +49 551 39 14416
   Email: arumaithurai@informatik.uni-goettingen.de

   Atsushi Tagami
   KDDI Research Inc.
   2-1-15 Ohara
   Fujimino, Saitama    356-85025

   Phone: +81 49 278 73651
   Fax:   +81 49 278 7510
   Email: tagami@kddi-research.jp

   K. K. Ramakrishnan
   University of California
   Riverside  CA

   Email: kkramakrishnan@yahoo.com

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   Nicola Blefari Melazzi
   University Tor Vergata
   Via del Politecnico, 1
   Roma  00133

   Phone: +39 06 7259 7501
   Fax:   +39 06 7259 7435
   Email: blefari@uniroma2.it

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