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Adaptive Video Streaming over Information-Centric Networking (ICN)

The information below is for an old version of the document that is already published as an RFC.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 7933.
Authors Cedric Westphal , Stefan Lederer , Christopher Mueller , Andrea Detti , Daniel Corujo , Jianping Wang , Marie-Jose Montpetit , Niall Murray , Christian Timmerer , Daniel Posch , Aytac Azgin , Will (Shucheng) LIU
Last updated 2016-08-26 (Latest revision 2016-04-28)
RFC stream Internet Research Task Force (IRTF)
Intended RFC status Informational
IETF conflict review conflict-review-irtf-icnrg-videostreaming
Additional resources Mailing list discussion
Stream IRTF state Published RFC
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IESG IESG state Became RFC 7933 (Informational)
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ICNRG                                                    C. Westphal, Ed.
Internet Draft                                                     Huawei
Intended status: Informational                                 S. Lederer
Expires: October 26, 2016                                         D. Posh
                                                              C. Timmerer
                                        Alpen-Adria University Klagenfurt
                                                              Aytac Azgin
                                                                   S. Liu
                                                               C. Mueller
                                           University of Rome Tor Vergata
                                                                D. Corujo
                                                     University of Aveiro
                                                                  J. Wang
                                             City University of Hong-Kong
                                                     Marie-Jose Montpetit
                                                             Niall Murray
                                          Athlone Institute of Technology

                                                         April 27, 2016

                     Adaptive Video Streaming over ICN

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   This document considers the consequences of moving the underlying
   network architecture from the current Internet to an Information-
   Centric Network (ICN) architecture on video distribution. As most of
   the traffic in future networks is expected to be video, we consider
   how to modify the existing video streaming mechanisms. Several
   important topics related to video distribution over ICN are
   presented, covering a wide range of scenarios: we look at how to
   evolve DASH to work over ICN, and leverage the recent ISO/IEC Moving
   Picture Experts Group (MPEG) Dynamic Adaptive Streaming over HTTP
   (DASH) standard; we consider layered encoding over ICN; Peer-to-Peer

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   (P2P) mechanisms introduce distinct requirements for video and we
   look at how to adapt PPSP for ICN; Internet Protocol Television
   (IPTV) adds delay constraints, and this will create more stringent
   requirements over ICN as well. As part of the discussion on video,
   we discuss Digital Rights Management (DRM) in ICN. Finally, in
   addition to considering how existing mechanisms would be impacted by
   ICN, this document lists some research issues to design ICN specific
   video streaming mechanisms.

Table of Contents
1. Introduction....................................................... 4
2. Conventions used in this document.................................. 5
3. Use case scenarios for ICN and Video Streaming..................... 5
4. Video download..................................................... 7
5. Video streaming and ICN............................................ 7
 5.1. Introduction to client-driven streaming and DASH ............... 7
 5.2. Layered Encoding  .............................................. 8
 5.3. Interactions of Video Streaming with ICN ....................... 9
   5.3.1. Interaction of DASH and ICN ................................ 9
   5.3.2. Interaction of ICN with Layered Encoding .................. 11
 5.4. Possible Integration of Video streaming and ICN architecture .. 12
   5.4.1. DASH over CCN ............................................. 12
   5.4.2. Testbed, Open Source Tools, and Dataset ................... 14
6. P2P video distribution and ICN.................................... 15
 6.1. Introduction to PPSP .......................................... 15
 6.2. PPSP over ICN: deployment concepts ............................ 16
   6.2.1. PPSP short background ..................................... 16
   6.2.2. From PPSP messages to ICN named-data ...................... 17
   6.2.3. Support of PPSP interaction through a pull-based ICN API .. 18
   6.2.4. Abstract layering for PPSP over ICN ....................... 18
   6.2.5. PPSP interaction with the ICN routing plane ............... 19
   6.2.6. ICN deployment for PPSP ................................... 20
 6.3. Impact of MPEG DASH coding schemes ............................ 21
7. IPTV and ICN...................................................... 22
 7.1. IPTV challenges ............................................... 22
 7.2. ICN benefits for IPTV delivery ................................ 23
8. Digital Rights Managements in ICN................................. 25
 8.1. Broadcast Encryption for DRM in ICN ........................... 25
 8.2. AAA Based DRM for ICN Networks ................................ 28
   8.2.1. Overview .................................................. 28
   8.2.2. Implementation ............................................ 29

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9. Future Steps for Video in ICN..................................... 30
 9.1. Large Scale Live Events ....................................... 30
 9.2. Video Conferencing and Real-Time Communications ............... 30
 9.3. Store-and-Forward Optimized Rate Adaptation ................... 30
 9.4. Heterogeneous Wireless Environment Dynamics ................... 31
 9.5. Network Coding for Video Distribution in ICN .................. 33
 9.6. Synchronization Issues for Video Distribution in ICN .......... 33
10. Security Considerations.......................................... 34
11. IANA Considerations.............................................. 34
12. Conclusions...................................................... 34
13. References....................................................... 35
 13.1. Normative References ......................................... 35
 13.2. Informative References ....................................... 35
14. Authors' Addresses............................................... 38
15. Acknowledgements................................................. 39

 1. Introduction

   The unprecedented growth of video traffic has triggered a rethinking
   of how content is distributed, both in terms of the underlying
   Internet architecture and in terms of the streaming mechanisms to
   deliver video objects.

   In particular, the IRTF ICNRG research group has been chartered to
   study new architectures centered upon information; the main
   contributor to Internet traffic (and information dissemination) is
   video, and this is expected to stay the same in the near future. If
   ICN is expected to become prominent, it will have to support video
   streaming efficiently.

   As such, it is necessary to discuss along two directions:

     . Can the current video streaming mechanisms be leveraged and
        adapted to an ICN architecture?

     . Can (and should) new, ICN-specific video streaming mechanisms
        be designed to fully take advantage of the new abstractions
        exposed by the ICN architecture?

   This document intends to focus on the first question, in an attempt
   to define the use cases for video streaming and some requirements.

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   This document focuses on a few scenarios, namely Netflix-like video
   streaming, peer-to-peer video sharing and IPTV, and identifies how
   the existing protocols can be adapted to an ICN architecture. In
   doing so, it also identifies the main issues with these protocols in
   this ICN context.

   Some documents have started to consider the ICN-specific
   requirements of dynamic adaptive streaming [2][3][4][6].

   In this document, we give a brief overview of the existing solutions
   for the selected scenarios. We then consider the interactions of
   such existing mechanisms with the ICN architecture and list some of
   the interactions any video streaming mechanism will have to
   consider. We then identify some areas for future research.

 2. Conventions used in this document

   In examples, "C:" and "S:" indicate lines sent by the client and
   server respectively.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC-2119 [RFC2119].

   In this document, these words will appear with that interpretation
   only when in ALL CAPS. Lower case uses of these words are not to be
   interpreted as carrying RFC-2119 significance.

 3. Use case scenarios for ICN and Video Streaming

   For ICN specific descriptions, we refer to the other research group
   documents. For our purpose, we assume here that ICN means an
   architecture where content is retrieved by name and with no binding
   of content to a specific network location.

   The consumption of multimedia content comes along with timing
   requirements for the delivery of the content, for both, live and on-
   demand consumption. Additionally, real-time use cases such as audio-
   /video conferencing [7], game streaming, etc., come along with more
   strict timing requirements. Long startup delays, buffering periods
   or poor quality, etc., should be avoided to achieve a good Quality
   of Experience (QoE) to the consumer of the content. (For a
   definition of QoE in the context of video distribution, please refer
   to [25]. The working definition is: "Quality of Experience (QoE) is
   the degree of delight or annoyance of the user of an application or
   service. It results from the fulfillment of his or her expectations

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   with respect to the utility and / or enjoyment of the application or
   service in the light of the user's personality and current state.")

   Of course, these requirements are heavily influenced by routing
   decisions and caching, which are central parts of ICN and which have
   to be considered when streaming video in such infrastructures.

   Due to this range of requirements, we find it useful to narrow the
   focus on four scenarios (more can be included later):

   - a video download architecture similar to that of Apple iTtunes(R),
     where the whole file is being downloaded to the client and can be
     replayed there multiple times;
   - a video streaming architecture for playing back movies; this is
     relevant for the naming and caching aspects of ICN, as well as the
     interaction with the rate adaptation mechanism necessary to
     deliver the best QoE to the end-user;
   - a peer-to-peer architecture for sharing videos; this introduces
     more stringent routing requirements in terms of locating copies of
     the content, as the location of the peers evolves and peers join
     and leave the swarm they use to exchange video chunks (for Peer-
     to-Peer definitions and taxonomy, please refer to RFC5694);
   - IPTV; this introduces requirements for multicasting and adds
     stronger delay constraints.

   Other scenarios, such as video-conferencing and real-time video
   communications are not explicitly discussed in this document, while
   they are in scope. Also, events of mass-media distribution, such as
   a large crowd in a live event, are also adding new requirements to
   be included in later version.

   We discuss how the current state-of-the-art protocols in an IP
   context can be modified for the ICN architecture. The remainder of
   this document is organized as follows. In the next section, we
   consider video download. Then in Section 5, we briefly describe DASH
   [1], and Layered Encoding (MDC, SVC). P2P is the focus of Section 6,
   where we describe PPSP. Section 7 highlights the requirements of
   IPTV, while Section 8 describes the issues of DRM. Section 9 lists
   some research issues to be solved for ICN-specific video delivery

   Videoconferencing and real-time video communications will be
   detailed more in future versions of this document; as well as the
   mass distribution of content at live large-scale events (stadium,
   concert hall, etc) for which there is no clearly adopted existing

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 4. Video download

   Video download, namely the fetching of a video file from a server or
   a cache down to the user's local storage, is a natural application
   of ICN. It should be supported natively without requiring any
   specific considerations.

   This is supported now by a host of protocols (say, SCP, FTP, or over
   HTTP), which would need to be replaced by the protocols to retrieve
   content in ICNs.

   However, current mechanisms are built atop existing transport
   protocols. Some ICN proposals (say, CCN or NDN for instance) attempt
   to leverage the work done upon these transport protocol and it has
   been proposed to use mechanisms such as the TCP congestion window
   (and the associated Adaptive Increase, Multiplicative Decrease -
   AIMD) to decide how many object requests ("interests" in CCN/NDN
   terminology) should be in flight at any point in time.

   It should be noted that ICN intrinsically supports different
   transport mechanisms, which could achieve better performance than
   TCP, as they subsume TCP into a special case. For instance, one
   could imagine a link-by-link transport coupled with caching. This is
   enabled by the ICN architecture, and would facilitate the point-to-
   point download of video files.

 5. Video streaming and ICN

5.1. Introduction to client-driven streaming and DASH

   Media streaming over the hypertext transfer protocol (HTTP) and in a
   further consequence streaming over the transmission control protocol
   (TCP) has become omnipresent in today's Internet. Content providers
   such as Netflix, Hulu, and Vudu do not deploy their own streaming
   equipment but use the existing Internet infrastructure as it is and
   they simply deploy their own services over the top (OTT). This
   streaming approach works surprisingly well without any particular
   support from the underlying network due to the use of efficient
   video compression, content delivery networks (CDNs), and adaptive
   video players. Earlier video streaming research mostly recommended
   to use the user datagram protocol (UDP) combined with the real time
   transport protocol (RTP). It assumed it would not be possible to
   transfer multimedia data smoothly with TCP, because of its
   throughput variations and large retransmission delays. This point of
   view has significantly evolved today. HTTP streaming, and especially
   its most simple form known as progressive download, has become very
   popular over the past few years because it has some major benefits

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   compared to RTP streaming. As a consequence of the consistent use of
   HTTP for this streaming method, the existing Internet
   infrastructure, consisting of proxies, caches and CDNs, could be
   used. Originally, this architecture was designed to support best
   effort delivery of files and not real time transport of multimedia
   data. Nevertheless, real time streaming based on HTTP could also
   take advantage of this architecture, in comparison to RTP, which
   could not leverage any of the aforementioned components. Another
   benefit that results from the use of HTTP is that the media stream
   could easily pass firewalls or network address translation (NAT)
   gateways, which was definitely a key for the success of HTTP
   streaming. However, HTTP streaming is not the holy grail of
   streaming as it also introduces some drawbacks compared to RTP.
   Nevertheless, in an ICN-based video streaming architecture these
   aspects also have to be considered.

   The basic concept of DASH [1] is to use segments of media content,
   which can be encoded at different resolutions, bit rates, etc., as
   so-called representations. These segments are served by conventional
   HTTP Web servers and can be addressed via HTTP GET requests from the
   client. As a consequence, the streaming system is pull-based and the
   entire streaming logic is located on the client, which makes it
   scalable, and allows to adapt the media stream to the client's

   In addition to this, the content can be distributed using
   conventional CDNs and their HTTP infrastructure, which also scales
   very well. In order to specify the relationship between the
   contents' media segments and the associated bit rate, resolution,
   and timeline, the Media Presentation Description (MPD) is used,
   which is a XML document. The MPD refers to the available media
   segments using HTTP URLs, which can be used by the client for
   retrieving them.

5.2. Layered Encoding

   Another approach for video streaming consist in using layered
   encoding. Namely, scalable video coding formats the video stream
   into different layers: a base layer which can be decoded to provide
   the lowest bit rate for the specific stream, and enhancement layers
   which can be transmitted separately if network conditions allow. The
   higher layers offer higher resolutions and enhancement of the video
   quality, while the layered approach allows to adapt to the network
   conditions. This is used in MPEG-4 scalable profile or H.263+.
   H264SVC is available, but not much deployed. JPEG2000 has a wavelet
   transform approach for layered encoding, but has not been deployed
   much either.

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   It is not clear if the layered approach is fine-grained enough for
   rate control.

5.3. Interactions of Video Streaming with ICN

          5.3.1. Interaction of DASH and ICN

   Video streaming, and DASH in particular, have been designed with
   goals that are aligned with that of most ICN proposals. Namely, it
   is a client-based mechanism, which requests items (in this case,
   chunks of a video stream) by name.

   ICN and MPEG-DASH [1] have several elements in common:

   - the client-initiated pull approach;
   - the content being dealt with in pieces (or chunks);
   - the support of efficient replication and distribution of content
     pieces within the network;
   - the scalable, session-free nature of the exchange between the
     client and the server at the streaming layer: the client is free
     to request any chunk from any location;
   - the support for potentially multiple source locations.

   For the last point, DASH may list multiple source URLs in a
   manifest, and ICN is agnostic to the location of a copy it is
   receiving. We do not imply that current video streaming mechanisms
   attempt to draw the content from multiple sources concurrently. This
   is a potential benefit of ICN, but is not considered in the current
   approaches mentioned in this document.

   As ICN is a promising candidate for the Future Internet (FI)
   architecture, it is useful to investigate its suitability in
   combination with multimedia streaming standards like MPEG-DASH. In
   this context, the purpose of this section is to present the usage of
   ICN instead of HTTP in MPEG-DASH

   However, there are some issues that arise from using a dynamic rate
   adaptation mechanism in an ICN architecture (note that some of the
   issues are related to caching, and not necessarily unique to ICN):

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   o  Naming of the data in DASH does not necessarily follow the ICN
      convention of any of the ICN proposals. Several chunks of the
      same video stream might currently go by different names that for
      instance do not share a common prefix. There is a need to
      harmonize the naming of the chunks in DASH with the naming
      conventions of the ICN. The naming convention of using a
      filename/time/encoding format could for instance be made
      compatible with the convention of CCN.

   o  While chunks can be retrieved from any server, the rate
      adaptation mechanism attempts to estimate the available network
      bandwidth so as to select the proper playback rate and keep its
      playback buffer at the proper level. Therefore, there is a need
      to either include some location semantics in the data chunks so
      as to properly assess the throughput to a specific location; or
      to design a different mechanism to evaluate the available network

   o  The typical issue of access control and accounting happens in
      this context, where chunks can be cached in the network outside
      of the administrative control of the content publisher. It might
      be a requirement from the owner of the video stream that access
      to these data chunks needs to be accounted/billed/monitored.

   o  Dynamic streaming multiplies the representations of a given video
      stream, therefore diminishing the effectiveness of caching:
      namely, to get a hit for a chunk in the cache, it has to be for
      the same format and encoding values. Alternatively, to get the
      same hit rate as for a stream using a single encoding, the cache
      size must be scaled up to include all the possible

   o  Caching introduces oscillatory dynamics as it may modify the
      estimation of the available bandwidth between the end user and
      the repository where it is getting the chunks from. For instance,
      if an edge cache holds a low resolution representation near the
      user, the user getting this low resolution chunks will observe a
      good performance, and will then request higher resolution chunks.
      If those are hosted on a server with poor performance, then the
      client would have to switch back to the low representation. This
      oscillation may be detrimental to the perceived QoE of the user.

   o  The ICN transport mechanism needs to be compatible to some extent
      with DASH. To take a CCN example, the rate at which interests are
      issued should be such that the chunks received in return arrive
      fast enough and with the proper encoding to keep the playback
      buffer above some threshold.

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   o  The usage of multiple network interfaces is possible in ICN,
      enabling a seamless handover between them. For the combination
      with DASH, an intelligent strategy which should focus on traffic
      load balancing between the available links may be necessary. This
      would increase the effective media throughput of DASH by
      leveraging the combined available bandwidth of all links,
      however, it could potentially lead to high variations of the
      media throughput.

   o  DASH does not define how the MPD is retrieved; hence, this is
      compatible with CCN. However, the current profiles defined within
      MPEG-DASH require the MPD to contain HTTP-URLs (incl. http and
      https URI schemes) to identify segments. To enable a more
      integrated approach as described in this document, an additional
      profile for DASH over CCN has to be defined, enabling ICN/CCN-
      based URIs to identify and request the media segments.

   We describe in Section 5.4 a potential implementation of a dynamic
   adaptive video stream over ICN, based upon DASH and CCN [5].

          5.3.2. Interaction of ICN with Layered Encoding

   Issues of interest to an Information-Centric network architecture in
   the context of layered video streaming include:

     . Caching of the multiple layers. The caching priority should go
        to the base layer, and defining caching policy to decide when
        to cache enhancement layers;
     . Synchronization of multiple content streams, as the multiple
        layers may come from different sources in the network (for
        instance, the base layer might be cached locally while the
        enhancement layers may be stored in the origin server). Video
        and audio video streams must be synchronized, and this includes
        both intra-layer synchronization (for the layers of the same
        video or audio stream) and inter-stream synchronization (see
        Section 9 for other synchronization aspects to be included in
        the "Future Steps for Video in ICN");
     . Naming of the different layers: when the client requests an
        object, the request can be satisfied with the base layer alone,
        aggregated with enhancement layers. Should one request be
        sufficient to provide different streams? In a CCN architecture
        for instance, this would violate a one interest-one data packet
        principle and the client would need to specify each layer it
        would like to receive. In a Pub/Sub architecture, the
        rendezvous point would have to make a decision as to which
        layers (or which pointer to which layer's location) to return.

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5.4. Possible Integration of Video streaming and ICN architecture

          5.4.1. DASH over CCN

   DASH is intended to enable adaptive streaming, i.e., each content
   piece can be provided in different qualities, formats, languages,
   etc., to cope with the diversity of todays' networks and devices. As
   this is an important requirement for Future Internet proposals like
   CCN, the combination of those two technologies seems to be obvious.
   Since those two proposals are located at different protocol layers -
   DASH at the application and CCN at the network layer - they can be
   combined very efficiently to leverage the advantages of both and
   potentially eliminate existing disadvantages. As CCN is not based on
   classical host-to-host connections, it is possible to consume
   content from different origin nodes as well as over different
   network links in parallel, which can be seen as an intrinsic error
   resilience feature w.r.t. the network. This is a useful feature of
   CCN for adaptive multimedia streaming within mobile environments
   since most mobile devices are equipped with multiple network links
   like 3G and WiFi. CCN offers this functionality out of the box which
   is beneficial when used for DASH-based services. In particular, it
   is possible to enable adaptive video streaming handling both
   bandwidth and network link changes. That is, CCN handles the network
   link decision and DASH is implemented on top of CCN to adapt the
   video stream to the available bandwidth.

   In principle, there are two options to integrate DASH and CCN: a
   proxy service acting as a broker between HTTP and CCN as proposed in
   [6], and the DASH client implementing a native CCN interface. The
   former transforms an HTTP request to a corresponding interest packet
   as well as a data packet back to an HTTP response, including
   reliable transport as offered by TCP. This may be a good compromise
   to implement CCN in a managed network and to support legacy devices.
   Since such a proxy is already described in [6] this draft focuses on
   a more integrated approach, aiming at fully exploiting the potential
   of a CCN DASH Client. That is, we describe a native CCN interface
   within the DASH client, which adopts a CCN naming scheme (CCN URIs)
   to denote segments in the Media Presentation Description (MPD). In
   this architecture, only the network access component on the client
   has to be modified and the segment URIs within MPD have to be
   updated according to the CCN naming scheme.

   Initially, the DASH client retrieves the MPD containing the CCN URIs
   of the content representations including the media segments. The
   naming scheme of the segments may reflect intrinsic features of CCN
   like versioning and segmentation support. Such segmentation support
   is already compulsory for multimedia streaming in CCN and, thus, can

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   also be leveraged for DASH-based streaming over CCN. The CCN
   versioning can be adopted in a further step to signal different
   representations of the DASH-based content, which enables an implicit
   adaptation of the requested content to the clients' bandwidth
   conditions. That is, the interest packet already provides the
   desired characteristics of a segment (such as bit rate, resolution,
   etc.) within the content name (or potentially within parameters
   defined as extra types in the packet formats). Additionally, if
   bandwidth conditions of the corresponding interfaces or routing
   paths allow so, DASH media segments could be aggregated
   automatically by the CCN nodes, which reduces the amount of interest
   packets needed to request the content. However, such approaches need
   further research, specifically in terms of additional intelligence
   and processing power needed at the CCN nodes.

   After requesting the MPD, the DASH client will start to request
   particular segments. Therefore, CCN interest packets are generated
   by the CCN access component and forwarded to the available
   interfaces. Within the CCN, these interest packets leverage the
   efficient interest aggregation for, e.g., popular content, as well
   as the implicit multicast support. Finally, the interest packets are
   satisfied by the corresponding data packets containing the video
   segment data, which are stored on the origin server or any CCN node,
   respectively. With an increasing popularity of the content, it will
   be distributed across the network resulting in lower transmission
   delays and reduced bandwidth requirements for origin servers and
   content providers respectively.

   With the extensive usage of in-network caching, new drawbacks are
   introduced since the streaming logic is located at the client, i.e.,
   clients are not aware of each other and the network infrastructure
   and cache states. Furthermore, negative effects are introduced when
   multiple clients are competing for a bottleneck and when caching is
   influencing this bandwidth competition. As mentioned above, the
   clients request individual portions of the content based on
   available bandwidth, which is calculated using throughput
   estimations. This uncontrolled distribution of the content
   influences the adaptation process of adaptive streaming clients. The
   impact of this falsified throughput estimation could be tremendous
   and leads to a wrong adaptation decision which may impact the
   Quality of Experience (QoE) at the client, as shown in [8]. In ICN,
   the client does not have the knowledge from which source the
   requested content is actually served or how many origin servers of
   the content are available, as this is transparent and depends on the
   name-based routing. This introduces the challenge that the
   adaptation logic of the adaptive streaming client is not aware of
   the event when the ICN routing decides to switch to a different

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   origin server or content is coming through a different
   link/interface. As most algorithms implementing the adaption logic
   are using bandwidth measurements and related heuristics, the
   adaptation decisions are no longer valid when changing origin
   servers (or links) and potentially cause playback interruptions and,
   consequently, stalling. Additionally, ICN supports the usage of
   multiple interfaces. A seamless handover between these interfaces
   (and different sources for the content) comes together with changes
   in performance, e.g., due to switching between fixed and wireless,
   3G/4G and WiFi networks, or between different types of servers (say
   with/without SSD, or with/without hardware acceleration), etc.

   Considering these characteristics of ICN, adaptation algorithms
   merely based on bandwidth measurements are not appropriate anymore,
   as potentially each segment can be transferred from another ICN node
   or interface, all with different bandwidth conditions. Thus,
   adaptation algorithms taking into account these intrinsic
   characteristics of ICN are preferred over algorithms based on mere
   bandwidth measurements.

          5.4.2. Testbed, Open Source Tools, and Dataset

   For the evaluations of DASH over CCN, a testbed with open source
   tools and datasets is provided in [9]. In particular, it provides
   two client player implementations, (i) a libdash extension for DASH
   over CCN and (ii) a VLC plugin implementing DASH over CCN. For both
   implementations the CCNx implementation has been used as a basis.

   The general architecture of libdash is organized in modules, so that
   the library implements a MPD parser and an extensible connection
   manager. The library provides object-oriented interfaces for these
   modules to access the MPD and the downloadable segments. These
   components are extended to support DASH over CCN and available in a
   separate development branch of the github project available at libdash comes together with
   a fully featured DASH player with a QT-based frontend, demonstrating
   the usage of libdash and providing a scientific evaluation platform.
   As an alternative, patches for the DASH plugin of the VLC player are
   provided. These patches can be applied to the latest source code
   checkout of VLC resulting in a DASH over CCN-enabled VLC player.

   Finally, a DASH over CCN dataset is provided in form of a CCNx
   repository. It includes 15 different quality representation of the
   well-known Big Buck Bunny Movie, ranging from 100 kbps up to 4500
   kbps. The content is split into segments of two seconds, and
   described by an associated MPD using the presented naming scheme in
   Section 4.1. This repository can be downloaded from [9], and is also

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   provided by a public accessible CCNx node. Associated routing
   commands for the CCNx namespaces of the content are provided via
   scripts coming together with the dataset and can be used as a public

 6. P2P video distribution and ICN

   Another form of distributing content - and video in particular-
   which ICNs need to support is Peer-to-Peer distribution (P2P). We
   see now how an existing protocol such as PPSP can be modified to
   work in an ICN environment.

6.1. Introduction to PPSP

   P2P video Streaming (PPS) is a popular approach to redistribute live
   media over Internet. The proposed P2PVS solutions can be roughly
   classified in two classes:

   -  Push/Tree based

   -  Pull/Mesh based

   The Push/Tree based solution creates an overlay network among peers
   that has a tree shape [30]. Using a progressive encoding (e.g.
   Multiple Description Coding or H.264 Scalable Video Coding),
   multiple trees could be set up to support video rate adaptation. On
   each tree an enhancement stream is sent. The higher the number of
   received streams, the higher the video quality. A peer controls the
   video rate by fetching or not the streams delivered over the
   distribution trees.

   The Pull/Mesh based solution is inspired by the BitTorrent file
   sharing mechanism. A Tracker collects information about the state of
   the swarm (i.e. set of participating peers). A peer forms a mesh
   overlay network with a subset of peers, and exchange data with them.
   A peer announces what data items it disposes and requests missing
   data items that are announced by connected peers. In case of live
   streaming, the involved data set includes only a recent window of
   data items published by the source.  Also in this case, the use of a
   progressive encoding can be exploited for video rate adaptation.

   Pull/Mesh based P2PVS solutions are the more promising candidate for
   the ICN deployment, since most of ICN approach provides a pull-based
   API [5][10][11][12]. In addition, Pull/Mesh based P2PVS are more
   robust than Push/Tree based one [13] and the Peer to Peer Streaming
   Protocol (PPSP) working group [14] is also proposing a Pull/Mesh
   based solution.

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                   |                                                |
                   |     +--------------------------------+         |
                   |     |            Tracker             |         |
                   |     +--------------------------------+         |
                   |        |     ^                   ^             |
                   |Tracker |     | Tracker           |Tracker      |
                   |Protocol|     | Protocol          |Protocol     |
                   |        |     |                   |             |
                   |        V     |                   |             |
                   |     +---------+    Peer     +---------+        |
                   |     |   Peer  |<----------->|   Peer  |        |
                   |     +---------+   Protocol  +---------+        |
                   |       | ^                                      |
                   |       | |Peer                                  |
                   |       | |Protocol                              |
                   |       V |                                      |
                   |     +---------------+                          |
                   |     |      Peer     |                          |
                   |     +---------------+                          |
                   |                                                |
            Figure 1: PPSP System Architecture (source [RFC6972])

   Figure 1 reports the PPSP architecture presented in [RFC6972]. PEERs
   announce and share video chunks and a TRACKER maintains a list of
   PEERs participating in a specific audio/video channel or in the
   distribution of a streaming file. The tracker functionality may be
   centralized in a server or distributed over the PEERs. PPSP
   standardize the Peer and Tracker Protocols, which can run directly
   over UDP or TCP.

   This document discusses some preliminary concepts about the
   deployment of PPSP on top of an ICN that exposes a pull-based API,
   meanwhile considering the impact of MPEG DASH streaming format.

6.2. PPSP over ICN: deployment concepts

          6.2.1. PPSP short background

   PPSP specifies peer protocol (PPSPP) [15] and tracker protocol

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   Some of the operations carried out by the tracker protocol are the
   followings. When a peer wishes to join the streaming session it
   contacts the Tracker (CONNECT message), obtains a PEER_ID and a list
   of PEER_IDs (and IP addresses) of other peers that are participating
   to the SWARM and that the tracker has singled out for the requesting
   peer (this may be a subset of the all peers of the SWARM). In
   addition to this join operation, a peer may contact the tracker to
   request to renew the list of participating peers (FIND message), to
   periodically update its status to the tracker (STAT_REPORT message),

   Some of the operations carried out by the peer protocol are the
   following. Using the list of peers delivered by the tracker, a peer
   establishes a session with them (HANDSHAKE message). A peer
   periodically announces to neighboring peers which chunks it has
   available for download (HAVE message). Using these announcements, a
   peer requests missing chunks from neighboring peers (REQUEST
   messages), which will send back them (DATA message).

          6.2.2. From PPSP messages to ICN named-data

   An ICN provides users with data items exposed by names. The bundle
   name and data item is usually referred as named-data, named-content,
   etc. To transfer PPSP messages though an ICN the messages should be
   wrapped as named-data items, and receivers should request them by

   A PPSP entity receives messages from peers and/or tracker. Some
   operations require gathering the messages generated by another
   specific host (peer or tracker). For instance, if a peer A wishes to
   gain information about video chunks available from peer B, the
   former shall fetch the PPSP HAVE messages specifically generated by
   the later. We refer to these kinds of named-data as "located-named-
   data", since they should be gathered from a specific location (e.g.
   peer B).

   For other PPSP operations, such as fetching a DATA message (i.e. a
   video chunk), as long as a peer receives the requested content, it
   doesn't matter which endpoint generated the data.We refer to this
   information with the generic term "named-data".

   The naming scheme differentiates named-data and located-named-data
   items. In case of named-data, the naming scheme only includes a
   content identifier (e.g. the name of the video chunk), without any
   prefix identifying who provides the content. For instance, a DATA
   message containing the video chunk #1 may be named as
   "ccnx:/swarmID/chunk/chunkID", where swarmID is a unique identifier

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   of the streaming session, "chunk" is a keyword and chunkID is the
   chunk identifier (e.g. a integer number).

   In case of located-named-data, the naming scheme includes a
   location-prefix, which uniquely identifies the host generating the
   data item. This prefix may be the PEER_ID in case the host was a
   peer or a tracker identifier in case the host was the tracker. For
   instance, a HAVE message generated by a peer B may be named as
   "ccnx:/swarmID/peer/PEER_ID/HAVE", where "peer" is a keyword,
   PEER_ID_B is the identifier of peer B and HAVE is a keyword.

          6.2.3. Support of PPSP interaction through a pull-based ICN

   The PPSP procedures are based both on pull and push interactions.
   For instance, the distribution of chunks availability can be
   classified as a push-based operation, since a peer sends an
   "unsolicited" information (HAVE message) to neighboring peers.
   Conversely the procedure used to receive video chunks can be
   classified as pull-based, since it is supported by a
   request/response interaction (i.e. REQUEST, DATA messages).

   As we said, we refer to an ICN architecture which provides a pull-
   based API. Accordingly, the mapping of PPSP pull-based procedure is
   quite simple. For instance, using the CCN architecture [5] a PPSP
   DATA message may be carried by a CCN Data message and a REQUEST
   message can transferred by a CCN Interest.

   Conversely, the support of push-based PPSP operations may be more
   difficult. We need of an adaptation functionality that carries out a
   push-based operation using the underlying pull-based service
   primitives. For instance, a possible approach is to use the
   request/response (i.e. Interest/Data) four ways handshakes proposed
   in [7]. Another possibility is that receivers periodically send out
   request messages of the named-data that neighbors will push and,
   when available, sender inserts the pushed data within a response

          6.2.4. Abstract layering for PPSP over ICN

                       |      Application                  |
                       |        PPSP (TCP/IP)              |
                       |  ICN - PPSP Adaptation Layer (AL) |

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                       |       ICN Architecture            |
                    Figure 2: Mediator approach

   Figure 2 provides a possible abstract layering for PPSP over ICN.
   The Adaptation Layer acts as a mediator (proxy) between legacy PPSP
   entities based on TCP/IP and the ICN architecture. In facts, the
   role the mediator is to use ICN to transfer PPSP legacy messages.

   This approach makes possible to merely reuse TCP/IP P2P applications
   whose software includes also PPSP functionality. This "all-in-one"
   development approach may be rather common since the PPSP-Application
   interface is not going to be specified. Moreover, if the Operating
   System will provide libraries that expose a PPSP API, these will be
   initially based on a underlying TCP/IP API. Also in this case, the
   mediator approach would make possible to easily reuse both the PPSP
   libraries and the Application on top of an ICN.

                       |      Application                  |
                       |        ICN-PPSP                   |
                       |       ICN Architecture            |

                    Figure 3: Clean-slate approach

   Figure 3 sketches a clean-slate layering approach in which the
   application directly includes or interacts with a PPSP version based
   on ICN. Likely such a PPSP_ICN integration could yield a simplier
   development, also because it does not require implementing a TCP/IP
   to ICN translation as in the Mediator approach. However, the clean-
   slate approach requires developing the application (in case of
   embedded PPSP functionality) or the PPSP library from scratch,
   without exploiting what might already exist for TCP/IP.

   Overall, the Mediator approach may be considered as the first step
   of a migration path towards ICN native PPSP applications.

          6.2.5.  PPSP interaction with the ICN routing plane

   Upon the ICN API a user (peer) requests a content and the ICN sends
   it back. The content is gathered by the ICN from any source, which
   could be the closest peer that disposes of the named-data item, an
   in-network cache, etc. Actually, "where" to gather the content is

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   controlled by an underlying ICN routing plane, which sets up the ICN
   forwarding tables (e.g. CCN FIB [5]).

   A cross-layer interaction between the ICN routing plane and the PPSP
   may be required to support a PPSP session. Indeed, ICN shall forward
   request messages (e.g. CCN Interest) towards the proper peer that
   can handle them. Depending on the layering approach, this cross-
   layer interaction is controlled either by the Adaptation Layer or by
   the ICN-PPSP. For example, if a peer A receives a HAVE message
   indicating that peer B disposes of the video chunk named
   "ccnx:/swarmID/chunk/chunkID", then former should insert in its ICN
   forwarding table an entry for the prefix
   "ccnx:/swarmID/chunk/chunkID" whose next hop locator (e.g. IP
   address) is the network address of peer B [17].

          6.2.6.         ICN deployment for PPSP

   The ICN functionality that supports a PPSP session may be "isolated"
   or "integrated" with the one of a public ICN.

   In the isolated case, a PPSP session is supported by an instance of
   an ICN (e.g. deployed on top of IP), whose functionalities operate
   only on the limited set of nodes participating to the swarm, i.e.
   peers and the tracker. This approach resembles the one followed by
   current P2P application, which usually form an overlay network among
   peers of a P2P application. And intermediate public IP routers do
   not carry out P2P functionalities.

   In the integrated case, the nodes of a public ICN may be involved in
   the forwarding and in-network caching procedures. In doing so, the
   swarm may benefit from the presence of in-network caches so limiting
   uplink traffic on peers and inter-domain traffic too. These are
   distinctive advantages of using PPSP over a public ICN, rather than
   over TCP/IP. In addition, such advantages aren't likely manifested
   in the case of isolated deployment.

   However, the possible interaction between the PPSP and the routing
   layer of a public ICN may be dramatic, both in terms of explosion of
   the forwarding tables and in terms of security. These issues
   specifically take place for those ICN architectures for which the
   name resolution (i.e. name to next-hop) occurs en-route, like the
   CCN architecture.

   For instance, using the CCN architecture, to fetch a named-data item
   offered by a peer A the on-path public ICN entities have to route
   the request messages towards the peer A. This implies that the ICN
   forwarding tables of public ICN nodes may contain many entries, e.g.

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   one entry per video chunk, and these entries are difficult to be
   aggregated since peers may have available only sparse parts of a big
   content, whose names have a same prefix (e.g. "ccnx:/swarmID").
   Another possibility is to wrap all PPSP messages into a located-
   named-data. In this case the forwarding tables should contain "only"
   the PEER_ID prefixes (e.g. "ccnx:/swarmID/peer/PEER_ID"), so scaling
   down the number of entries from number of chunks to number of peers.
   However, in this case the ICN mechanisms recognize a same video
   chunk offered by different peers as different contents, so vanishing
   caching and multicasting ICN benefits. Moreover, in any case routing
   entries should be updated either the base of the availability of
   named-data items on peers or on the presence of peers, and these
   events in a P2P session is rapidly changing so possibly hampering
   the convergence of the routing plane. Finally, since peers have an
   impact on the ICN forwarding table of public nodes, this may open
   obvious security issues.

6.3. Impact of MPEG DASH coding schemes

   The introduction of video rate adaptation may significantly decrease
   the effectiveness of P2P cooperation and of in-network caching,
   depending of the kind of the video coding used by the MPEG DASH

   In case of a MPEG DASH streaming with MPEG AVC encoding, a same
   video chunk is independently encoded at different rates and the
   encoding output is a different file for each rate. For instance, in
   case of a video encoded at three different rates R1,R2,R3, for each
   segment S we have three distinct files: S.R1, S.R2, S.R3. These
   files are independent of each other. To fetch a segment coded at R2
   kbps, a peer shall request the specific file S.R2. Receiver-driven
   algorithms, implemented by the video client, usually handle the
   estimation of the best coding rate.

   The independence among files associated to different encoding rates
   and the heterogeneity of peer bandwidths, may dramatically reduce
   the interaction among peers, the effectiveness of in-network caching
   (in case of integrated deployment), and consequently the ability of
   PPSP to offload the video server (i.e. a seeder peer). Indeed, a
   peer A may select a coding rate (e.g. R1) different from the one
   selected by a peer B (e.g. R2) and this prevents the former to fetch
   video chunks from the later, since peer B only has chunks available
   that are coded at a rate different from the ones needed by A. To
   overcome this issue, a common distributed rate selection algorithm
   could force peers to select the same coding rate [17]; nevertheless
   this approach may be not feasible in the in case of many peers.

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   The use of SVC encoding (Annex G extension of the H.264/MPEG-4 AVC
   video compression standard) should make rate adaptation possible,
   meanwhile neither reducing peer collaborations nor the in-network
   caching effectiveness. For a single video chunk, a SVC encoder
   produces different files for the different rates (roughly "layers"),
   and these files are progressively related each other. Starting from
   a base-layer which provides the minimum rate encoding, the next
   rates are encoded as an "enhancement layer" of the previous one. For
   instance, in case the video is coded with three rates R1 (base-
   layer), R2 (enhancement-layer n.1), R3 (enhancement-layer n.2), then
   for each DASH segment we have three files S.R1, S.R2 and S.R3. The
   file S.R1 is the segment coded at the minimum rate (base-layer). The
   file S.R2 enhances S.R1, so as S.R1 and S.R2 can be combined to
   obtain a segment coded at rate R2. To get a segment coded at rate
   R2, a peer shall fetch both S.R1 and S.R2. This progressive
   dependence among files that encode a same segment at different rates
   makes peer cooperation possible, also in case peers player have
   autonomously selected different coding rates. For instance, if peer
   A has selected the rate R1, the downloaded files S.R1 are useful
   also for a peer B that has selected the rate R2, and vice versa.

 7. IPTV and ICN

7.1. IPTV challenges

   IPTV refers to the delivery of quality content broadcast over the
   Internet, and is typically associated with strict quality
   requirements, i.e., with a perceived latency of less than 500 ms and
   a packet loss rate that is multiple orders lower than the current
   loss rates experienced in the most commonly used access networks
   (see [31]). We can summarize the major challenges for the delivery
   of IPTV service as follows.

   Channel change latency represents a major concern for the IPTV
   service. Perceived latency during channel change should be less than
   500ms. To achieve this objective over the IP infrastructure, we have
   multiple choices:

   (i)   receiving fast unicast streams from a dedicated server (most
          effective but not resource efficient);
   (ii)  connecting to other peers in the network (efficiency depends
          on peer support, effective and resource efficient, if also
          supported with a dedicated server);

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   (iii) connecting to multiple multicast sessions at once (effective
          but not resource efficient, and depends on the accuracy of
          the prediction model used to track user activity).

   The second major challenge is the error recovery.  Typical IPTV
   service requirements dictate the mean time between artifacts to be
   approximately 2 hours (see [31]). This suggests the perceived loss
   rate to be around or less than 10^-7. Current IP-based solutions
   rely on the following proactive and reactive recovery techniques:
   (i) joining the FEC multicast stream corresponding to the perceived
   packet loss rate (not efficient as the recovery strength is chosen
   based on worst-case loss scenarios), (ii) making unicast recovery
   requests to dedicated servers (requires active support from the
   service provider), (iii) probing peers to acquire repair packets
   (finding matching peers and enabling their cooperation is another

7.2. ICN benefits for IPTV delivery

   ICN presents significant advantages for the delivery of IPTV
   traffic. For instance, ICN inherently supports multicast and allows
   for quick recovery from packet losses (with the help of in-network
   caching). Similarly, peer support is also provided in the shape of
   in-network caches that typically act as the middleman between two
   peers, enabling therefore earlier access to IPTV content.

   However, despite these advantages, delivery of IPTV service over
   Information Centric Networks brings forth new challenges. We can
   list some of these challenges as follows:

     . Messaging overhead: ICN is a pull-based architecture and relies
        on a unique balance between requests and responses. A user
        needs to make a request for each data packet. In the case of
        IPTV, with rates up to, and likely to be, above 15Mbps, we
        observe significant traffic upstream to bring those streams. As
        the number of streams increases (including the same session at
        different quality levels and other formats), so does the burden
        on the routers. Even if the majority of requests are aggregated
        at the core, routers close to the edge (where we observe the
        biggest divergence in user requests) will experience a
        significant increase in overhead to process these requests. The
        same is true at the user side, as the uplink usage multiplies

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        in the number of sessions a user requests (for instance, to
        minimize the impact of bandwidth fluctuations).
     . Cache control: As the IPTV content expires at a rapid rate
        (with a likely expiry threshold of 1s), we need solutions to
        effectively flush out such content to also prevent degradation
        impact on other cached content, with the help of intelligently
        chosen naming conventions. However, to allow for fast recovery
        and optimize access time to sessions (from current or new
        users), the timing of such expirations needs to be adaptive to
        network load and user demand. However, we also need to support
        quick access to earlier content, whenever needed, for instance,
        when the user accesses the rewind feature (note that in-network
        caches will not be of significant help in such scenarios due to
        overhead required to maintain such content).
     . Access accuracy: To receive the up-to-date session data, users
        need to be aware of such information at the time of their
        request. Unlike IP multicast, since the users join a session
        indirectly, session information is critical to minimize
        buffering delays and reduce the startup latency.  Without such
        information, and without any active cooperation from the
        intermediate routers, stale data can seriously undermine the
        efficiency of content delivery. Furthermore, finding a cache
        does not necessarily equate to joining a session, as the look-
        ahead latency for the initial content access point may have a
        shorter lifetime than originally intended. For instance, if the
        user that has initiated the indirect multicast leaves the
        session early, the requests from the remaining users need to
        experience an additional latency of one RTT as they travel
        towards the content source. If the startup latency is chosen
        depending on the closeness to the intermediate router, going to
        the content source in-session can lead to undesired pauses.

   It should be noted that IPTV includes more than just multicast. Many
   implementations include "trick plays" (fast forward, pause, rewind)
   that often transform a multicast session into multiple unicast
   sessions. In this context, ICN is beneficial, as the caching offers
   an implicit multicast, but without tight synchronization constraints
   in between two different users. One user may rewind, and start
   playing forward again, drawing from a nearby cache of the content
   recently viewed by another user (whereas in a strict multicast
   session, the opportunity of one user lagging off behind would be
   more difficult to implement).

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 8. Digital Rights Managements in ICN

   This section discusses the need for Digital Rights Management (DRM)
   functionalities for multimedia streaming over ICN. It focuses on two
   possible approaches: modifying AAA to support DRM in ICN, and using
   Broadcast Encryption.

   It is assumed that ICN will be used heavily for digital content
   dissemination. It is vital to consider DRM for digital content
   distribution. In today's Internet there are two predominant classes
   of business models for on-demand video streaming. The first model is
   based on advertising revenues. Non-copyright protected (usually
   user-generated content, UGC) is offered by large infrastructure
   providers like Google (YouTube) at no charge. The infrastructure is
   financed by spliced advertisements into the content. In this context
   DRM considerations may not be required, since producers of UGC may
   only strive for the maximum possible dissemination. Some producers
   of UGC are mainly interested to share content with their families,
   friends, colleges or others and have no intention to make profit.
   However, the second class of business models requires DRM, because
   they are primarily profit oriented. For example, large on-demand
   streaming platforms like Netflix establish business models based on
   subscriptions. Consumers may have to pay a monthly fee in order to
   get access to copyright protected content like TV series, movies or
   music. This model may be ad-supported and free to the content
   consumer, like YouTube Channels or Spotify. But the creator of the
   content expects some remuneration for his work. From the perspective
   of the service providers and the copyright owners, only clients that
   pay the fee (explicitly or implicitly through ad placement) should
   be able to access and consume the content. Anyway, the challenge is
   to find an efficient and scalable way of access control to digital
   content, which is distributed in information-centric networks.

8.1. Broadcast Encryption for DRM in ICN

   The section discusses Broadcast Encryption (BE) as a suitable basis
   for DRM functionalities in conformance to the ICN communication
   paradigm. Especially when network inherent caching is considered the
   advantage of BE will be highlighted.

   In ICN, data packets can be cached inherently in the network and any
   network participant can request a copy of these packets. This makes
   it very difficult to implement an access control for content that is
   distributed via ICN. A naive approach is to encrypt the transmitted
   data for each consumer with a distinct key. This prohibits everyone

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   other than the intended consumers to decrypt and consume the data.
   However, this approach is not suitable for ICN's communication
   paradigm since it would reduce the benefits gained from the inherent
   network caching. Even if multiple consumers request the same content
   the requested data for each consumer would differ using this
   approach. A better but still insufficient idea is to use a single
   key for all consumers. This does not destruct the benefits of ICN's
   caching ability. The drawback is that if one of the consumers
   illegally distributes the key, the system is broken and any entity
   in the network can access the data. Changing the key after such an
   event is useless since the provider has no possibility to identify
   the illegal distributer. Therefore this person cannot be stopped
   from distributing the new key again. In addition to this issue other
   challenges have to be considered. Subscriptions expire after a
   certain time and then it has to be ensured that these consumers
   cannot access the content anymore. For a provider that serves
   millions of daily consumers (e.g. Netflix) there could be a
   significant number of expiring subscriptions per day. Publishing a
   new key every time a subscription expires would require an
   unsuitable amount of computational power just to re-encrypt the
   collection of audio-visual content.

   A possible approach to solve these challenges is Broadcast
   Encryption (BE) [22] as proposed in [23]. From this point on, this
   section will focus only on BE as an enabler for DRM functionality in
   the use case of ICN video streaming. This subsection continues with
   the explanation of how BE works and shows how BE can be used to
   implement an access control scheme in the context of content
   distribution in ICN.

   BE actually carries a misleading name. One might expect a concrete
   encryption scheme. However, it belongs to the family of key-
   management schemes (KMS). KMS are responsible for the generation,
   exchange, storage and replacement of cryptographic keys. The most
   interesting characteristics of Broadcast Encryption Schemes (BES)

     . A BES typically uses a global trusted entity called the
        licensing agent (LA), which is responsible for spreading a set
        of pre-generated secrets among all participants. Each
        participant gets a distinct subset of secrets assigned from the
     . The participants can agree on a common session key, which is
        chosen by the LA. The LA broadcasts an encrypted message that
        includes the key. Participants with a valid set of secrets can
        derive the session-key from this message.

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     . The number of participants in the system can change
        dynamically. Entities may join or leave the communication group
        at any time. If a new entity joins the LA passes on a valid set
        of secrets to that entity. If an entity leaves (or is forced to
        leave) the LA revokes the entity's subset of keys, which means
        that it cannot derive the correct session key anymore when the
        LA distributes a new key.
     . Traitors (entities that reveal their secrets) can be traced and
        excluded from ongoing communication. The algorithms and
        preconditions to identify a traitor vary between concrete BES.

   This listing already illustrates why BE is suitable to control the
   access to data that is distributed via an information-centric
   network. BE enables the usage of a single session key for
   confidential data transmission between a dynamically changing subset
   or network participants. ICN caches can be utilized since the data
   is encrypted only with a single key known by all legitimate clients.
   Furthermore, traitors can be identified and removed from the system.
   The issue of re-encryption still exists, because the LA will
   eventually update the session key when a participant should be
   excluded. However, this disadvantage can be relaxed in some way if
   the following points are considered:

     . The updates of the session key can be delayed until a set of
        compromised secrets has been gathered. Note that secrets may
        become compromised because of two reasons. First, a traitor
        could have illegally revealed the secret. Second, the
        subscription of an entity expired. Delayed revocation
        temporarily enables some non-legitimate entities to consume
        content. However, this should not be a severe problem in home
        entertainment scenarios. Updating the session key in regular
        (not too short) intervals is a good tradeoff. The longer the
        interval last the less computational resources are required for
        content re-encryption and the better the cache utilization in
        the ICN will be. To evict old data from ICN caches that has
        been encrypted with the prior session key the publisher could
        indicate a lifetime for transmitted packets.
     . Content should be re-encrypted dynamically at request time.
        This has the benefit that untapped content is not re-encrypted
        if the content is not requested during two session key updates
        and therefore no resources are wasted. Furthermore, if the
        updates are triggered in non-peak times the maximum amount of
        resource needed at one point in time can be lowered
        effectively, since in peak times generally more diverse content
        is requested.
     . Since the amount of required computational resources may vary
        strongly from time to time it would be beneficial for any

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        streaming provider to use cloud-based services to be able to
        dynamically adapt the required resources to the current needs.
        Regarding to a lack of computation time or bandwidth the cloud
        service could be used to scale up to overcome shortages.

   Figure 4 show the potential usage of BE in a multimedia delivery
   frameworks that builds upon ICN infrastructure and uses the concept
   of dynamic adaptive streaming, e.g., DASH. BE would be implemented
   on the top to have an efficient and scalable way of access control
   to the multimedia content.

             +--------Multimedia Delivery Framework--------+
             |                                             |
             |     Technologies            Properties      |
             |  +----------------+     +----------------+  |
             |  |   Broadcast    |<--->|   Controlled   |  |
             |  |   Encryption   |     |     Access     |  |
             |  +----------------+     +----------------+  |
             |  |Dynamic Adaptive|<--->|   Multimedia   |  |
             |  |   Streaming    |     |   Adaptation   |  |
             |  +----------------+     +----------------+  |
             |  |       ICN      |<--->|    Cachable    |  |
             |  | Infrastructure |     |   Data Chunks  |  |
             |  +----------------+     +----------------+  |

           Figure 4: A potential multimedia framework using BE.

8.2      .                AAA Based DRM for ICN Networks

          8.2.1.                                         Overview

   Recently, a novel approach to Digital Rights Management (DRM) has
   emerged to link DRM to usual network management operations, hence
   linking DRM to authentication, authorization, and accounting (AAA)
   services. ICN provides the abstraction of an architecture where
   content is requested by name and could be served from anywhere. In
   DRM, the content provider (the origin of the content) allows the
   destination (the end user account) to use the content. The content
   provider and content storage/cache are at two different entities in
   ICC and for traditional DRM only source and destination count and
   not the intermediate storage. The proposed solution allows the
   provider of the caching to be involved in the DRM policies using
   well known AAA mechanisms. It is important to note that this
   solution is compatible with the proposes the Broadcast Encryption

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   (BE) proposed earlier in this draft. The BE proposes a technology as
   this solution is more operational.

          8.2.2.                                        Implementation

   With the proposed AAA-based DRM, when content is requested by name
   from a specific destination, the request could link back to both the
   content provider and the caching provider via traditional AAA
   mechanisms, and trigger the appropriate DRM policy independently
   from where the content is stored. In this approach the caching, DRM
   and AAA remain independent entities but can work together through
   ICN mechanisms. The proposed solution enables extending the
   traditional DRM done by the content provider to jointly being done
   by content provider and network/caching provider.

   The solution is based on the concept of a "token".  The content
   provider authenticates the end user and issues an encrypted token to
   authenticate the a named content ID or IDs that the user can access.
   The token will be shared with the network provider and used as the
   interface to the AAA protocols. At this point all content access is
   under the control of the network provider and the ICN. The
   controllers and switches can manage the content requests and handle
   mobility. The content can be accessed from anywhere as long as
   the token remains valid or the content is available in the network.
   In such a scheme the content provider does not need to be contacted
   every time a named content is requested. This reduces the load of
   the content provider network and creates a DRM mechanism that is
   much more appropriate for the distributed caching and peer-to-peer
   storage characteristic of ICN networks. In particular, the content
   requested by name can be served from anywhere under the only
   condition that the storage/cache can verify that the token is valid
   for content access.

   The solution is also fully customizable to both content and network
   provider's needs as the tokens can be issued based on user accounts,
   location and hardware (MAC address for example) linking it naturally
   to legacy authentication mechanisms. In addition, since both content
   and network providers are involved in DRM policies pollution attacks
   and other illegal requests for the content can be more easily
   detected. The proposed AAA-based DRM is currently under full

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 9. Future Steps for Video in ICN

   The explosion of online video services, along with their increased
   consumption by mobile wireless terminals, further exacerbates the
   challenges of Video Adaptation leveraging ICN mechanisms. The
   following sections present a series of research items derived from
   these challenges, further introducing next steps for the subject.

9.1. Large Scale Live Events

   An active area of investigation and a potential use case where ICN
   would provide significant benefits, is that of distributing content,
   and video in particular, using local communications in large scale
   events such as sports event in a stadium, a concert or a large

   Such use-case involves locating content that is generated on the fly
   and requires discovery mechanisms in addition to sharing mechanisms.
   The scalability of the distribution becomes important as well.

9.2. Video Conferencing and Real-Time Communications

   Current protocols for video-conferencing have been designed, and
   this document needs to take input from them to identify the key
   research issues. Real-time communications add timing constraints
   (both in terms of delay and in terms of synchronization) to the
   scenario discussed above.

   AR and VR (and immersive multimedia experiences in general) are
   clearly an area of further investigation, as they involve combining
   multiple streams of data from multiple users into a coherent whole.
   This raises issues of multi-source multi-destination multimedia
   streams that ICN may be equipped to deal with in a more natural
   manner than IP that is inherently unicast.

9.3. Store-and-Forward Optimized Rate Adaptation

   One of the benefits of ICN is to allow the network to insert caching
   in the middle of the data transfer. This can be used to reduce the
   overall bandwidth demands over the network by caching content for
   future re-use. But it provides more opportunities for optimizing
   video streams.

   Consider for instance the following scenario: a client is connected
   via an ICN network to a server. Let's say the client is connected
   wirelessly to a node that has a caching capability, which is
   connected through a WAN to the server. Assume further that the

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   capacity of each of the links (both the wireless and the WAN logical
   links) vary with time.

   If the rate adaptation is provided in an end-to-end manner, as in
   current mechanisms like DASH, then the maximal rate that can be
   supported at the client is that of the minimal bandwidth on each

   For instance, if during time period 1, the wireless capacity is 1
   and the wired capacity is 2, and during time period 2, the wireless
   is 2 due to some hotspot, and the wired is 1 due to some congestion
   in the network, then the best end-to-end rate that can be achieved
   is 1 during each period.

   However, if the cache is used during time period 1 to pre-fetch 2
   units of data, then during period 2, there is 1 unit of data at the
   cache, and another unit of data, which can be streamed from the
   server, and the rate that can be achieved is therefore 2 units of
   data. In this case, the average bandwidth rises from 1 to 1.5 over
   the 2 periods.

   This straw man example illustrate a) the benefit of ICN for
   increasing the throughput of the network, and b) the need for the
   special rate adaptation mechanisms to be designed so as to take
   advantage of this gain. End-to-end rate adaptation cannot take
   advantage of the cache availability.

9.4. Heterogeneous Wireless Environment Dynamics

   With the ever-growing increase in online services being accessed by
   mobile devices, operators have been deploying different overlapping
   wireless access networking technologies. In this way, in the same
   area, user terminals are within range of different cellular, Wi-Fi
   or even WiMAX networks. Moreover, with the advent of the Internet of
   Things (e.g., surveillance cameras feeding video footage), this list
   can be further complemented with more specific short-range
   technologies, such as Bluetooth or ZigBee.

   In order to leverage from this plethora of connectivity
   opportunities, user terminals are coming equipped with different
   wireless access interfaces, providing them with extended
   connectivity opportunities. In this way, such devices become able to
   select the type of access which best suits them according to
   different criteria, such as available bandwidth, battery
   consumption, access do different link conditions according to the
   user profile or even access to different content. Ultimately, these
   aspects contribute to the Quality of Experience perceived by the

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   end-user, which is of utmost importance when it comes to video

   However, the fact that these users are mobile and using wireless
   technologies, also provides a very dynamic setting, where the
   current optimal link conditions at a specific moment might not last
   or be maintained while the user moves. These aspects have been amply
   analyzed in recently finished projects such as FP7 MEDIEVAL [18],
   where link events reporting on wireless conditions and available
   alternative connection points were combined with vide requirements
   and traffic optimization mechanisms, towards the production of a
   joint network and mobile terminal mobility management decision.
   Concretely, in [19] link information about the deterioration of the
   wireless signal was sent towards a mobility management controller in
   the network. This input was combined with information about the user
   profile, as well as of the current video service requirements, and
   used to trigger the decrease or increase of scalable video layers,
   adjusting the video to the ongoing link conditions. Incrementally,
   the video could also be adjusted when a new better connectivity
   opportunity presents itself.

   In this way, regarding Video Adaptation, ICN mechanisms can leverage
   from their intrinsic multiple source support capability and go
   beyond the monitoring of the status of the current link, thus
   exploiting the availability of different connectivity possibilities
   (e.g., different "interfaces"). Moreover, information obtained from
   the mobile terminal's point of view of its network link, as well as
   information from the network itself (i.e., load, policies, and
   others), can generate scenarios where such information is combined
   in a joint optimization procedure allowing the content to be forward
   to users using the best available connectivity option (e.g.,
   exploiting management capabilities supported by ICN intrinsic
   mechanisms as in [20]).

   In fact, ICN base mechanisms can further be exploited in enabling
   new deployment scenarios such as preparing the network for mass
   requests from users attending a large multimedia event (i.e.,
   concert, sports), allowing video to be adapted according to content,
   user and network requirements and operation capabilities in a
   dynamic way.

   The enablement of such scenarios require further research, with the
   main points highlighted as follows:

  . Development of a generic video services (and obviously content)
     interface allowing the definition and mapping of their

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     requirements (and characteristics) into the current capabilities
     of the network;

  . How to define a scalable mechanism allowing either the video
     application at the terminal, or some kind of network management
     entity, to adapt the video content in a dynamic way;

  . How to develop the previous research items using intrinsic ICN
     mechanisms (i.e., naming and strategy layers);

  . Leverage intelligent pre-caching of content to prevent stalls and
     poor quality phases, which lead to bad Quality of Experience of
     the user. This includes in particular the usage in mobile
     environments, which are characterized by severe bandwidth changes
     as well as connection outages, as shown in [21];

  . How to take advantage of the multi-path opportunities over the
     heterogeneous wireless interfaces.

9.5. Network Coding for Video Distribution in ICN

   An interesting research area for combining heterogeneous sources is
   to use network coding [24]. Network coding allows to asynchronously
   combine multiple sources by having each of them send information
   that is not duplicated by the other but can be combined to retrieve
   the video stream.

   However, this creates issues in ICN in terms of defining the proper
   rate adaptation for the video stream; securing the encoded data;
   caching the encoded data; timeliness of the encoded data; overhead
   of the network coding operations both in network resources and in
   added buffering delay, etc.

   Network coding has shown promise in reducing buffering events in
   unicast, multicast and P2P setting. [26] considers strategies using
   network coding to enhance QoE for multimedia communications. Network
   coding can be applied to multiple streams, but also within a single
   stream as an equivalent of a composable erasure code. Clearly, there
   is a need for further investigation of network coding in ICN,
   potentially as a topic of activity in the research group.

9.6. Synchronization Issues for Video Distribution in ICN

   ICN de-couples the fetching of video chunks from the location of
   these chunks. This means an audio chunk may be received from one
   network element (cache/storage/server) while a video chunk may be
   received from another one while another chunk (say, the next one, or

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   another layer from the same video stream) may come from a third
   element. This introduces disparity in the retrieval times and
   locations of the different elements of a video stream that need to
   be played at the same (or almost same) time. Synchronization of such
   delivery and playback may require specific synchronization tools for
   video delivery in ICN.

   Other synchronization aspects involve:

   - synchronizing within a single stream, for instance the consecutive
     chunks of a single stream, or the multiple layers of a layered
     scheme, when sources and transport layers may be different. Re-
     ordering the packets of a stream distributed over multiple sources
     at the video client, or ensuring that multiple chunks coming from
     multiple sources arrive within an acceptable time window;
   - synchronizing multiple streams, such as the audio and video
     components of a video stream, which can be received from
     independent sources;
   - synchronizing multiple streams from multiple sources to multiple
     destinations, such as mass distribution of live events. For
     instance, for live video streams or video-conferencing, some level
     of synchronization is required so that people watching the stream
     view the same events at the same time.

   Some of these issues were addressed in [27] in the context of social
   video consumption. Network coding, with traffic engineering, is
   considered as a potential solution for synchronization issues. Other
   approaches could be considered that are specific for ICN as well.

   Traffic engineering in ICN [28,29] may be required to provide proper
   synchronization of multiple streams.

 10. Security Considerations

   This is informational. There are no specific security considerations
   outside of those mentioned in the text.

 11. IANA Considerations

   This document does not require any IANA action.

 12. Conclusions

   This draft proposed adaptive video streaming for ICN, identified
   potential problems and presented the combination of CCN with DASH as
   a solution. As both concepts, DASH and CCN, maintain several
   elements in common, like, e.g., the content in different versions

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   being dealt with in segments, combination of both technologies seems
   useful. Thus, adaptive streaming over CCN can leverage advantages
   such as, e.g., efficient caching and intrinsic multicast support of
   CCN, routing based on named data URIs, intrinsic multi-link and
   multi-source support, etc.

   In this context, the usage of CCN with DASH in mobile environments
   comes together with advantages compared to today's solutions,
   especially for devices equipped with multiple network interfaces.
   The retrieval of data over multiple links in parallel is a useful
   feature, specifically for adaptive multimedia streaming, since it
   offers the possibility to dynamically switch between the available
   links depending on their bandwidth capabilities, transparent to the
   actual DASH client.

 13. References

13.1. Normative References

   [RFC6972] Y. Zhang, N. Zong, "Problem Statement and Requirements of
             the Peer-to-Peer Streaming Protocol (PPSP)", RFC6972, July

13.2. Informative References

   [1]   ISO/IEC DIS 23009-1.2, Information technology - Dynamic
         adaptive streaming over HTTP (DASH) - Part 1: Media
         presentation description and segment formats

   [2]   Lederer, S., Mueller, C., Rainer, B., Timmerer, C.,
         Hellwagner, H., "An Experimental Analysis of Dynamic Adaptive
         Streaming over HTTP in Content Centric Networks", in
         Proceedings of the IEEE International Conference on Multimedia
         and Expo 2013, San Jose, USA, July, 2013

   [3]   Liu, Y., Geurts, J., Point, J., Lederer, S., Rainer, B.,
         Mueller, C., Timmerer, C., Hellwagner, H., "Dynamic Adaptive
         Streaming over CCN: A Caching and Overhead Analysis", in
         Proceedings of the IEEE international Conference on
         Communication (ICC) 2013 - Next-Generation Networking
         Symposium, Budapest, Hungary, June, 2013

   [4]   Grandl, R., Su, K., Westphal, C., "On the Interaction of
         Adaptive Video Streaming with Content-Centric Networks",
         eprint arXiv:1307.0794, July 2013.

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   [5]   V. Jacobson, D. Smetters, J. Thornton, M. Plass, N. Briggs and
         R. Braynard, "Networking named content", in Proc. of the 5th
         int. Conf. on Emerging Networking Experiments and Technologies
         (CoNEXT '09). ACM, New York, NY, USA, 2009, pp. 1-12.

   [6]   A. Detti, M. Pomposini, N. Blefari-Melazzi, S. Salsano and A.
         Bragagnini, "Offloading cellular networks with Information-
         Centric Networking: The case of video streaming", In Proc. of
         the Int. Symp. on a World of Wireless, Mobile and Multimedia
         Networks (WoWMoM '12), IEEE, San Francisco, CA, USA, 1-3,

   [7]   V. Jacobson, D. K. Smetters, N. H. Briggs, M. F. Plass, P.
         Stewart, J. D. Thornton, and R. L. Braynard, "VoCCN: Voice
         over content-centric networks," in ACM ReArch Workshop, 2009

   [8]   Christopher Mueller, Stefan Lederer and Christian Timmerer, A
         proxy effect analysis and fair adaptation algorithm for
         multiple competing dynamic adaptive streaming over HTTP
         clients, In Proceedings of the Conference on Visual
         Communications and Image Processing (VCIP) 2012, San Diego,
         USA, November 27-30, 2012.

   [9]   DASH Research at the Institute of Information Technology,
         Multimedia Communication Group, Alpen-Adria Universitaet
         Klagenfurt, URL:

   [10] A. Detti, N. Blefari-Melazzi, S. Salsano, and M. Pomposini
        CONET: A content centric inter-networking architecture," in ACM
        Workshop on Information-Centric Networking (ICN), 2011.

   [11] W. K. Chai, N. Wang, I. Psaras, G. Pavlou, C. Wang, G. C. de
        Blas, F. Ramon-Salguero, L. Liang, S. Spirou, A. Beben, and E.
        Hadjioannou, "CURLING: Content-ubiquitous resolution and
        delivery infrastructure for next-generation services," IEEE
        Communications Magazine, vol. 49, no. 3, pp. 112-120, March

   [12] NetInf project Website

   [13] N. Magharei, R. Rejaie, Yang Guo, "Mesh or Multiple-Tree: A
        Comparative Study of Live P2P Streaming Approaches," INFOCOM
        2007. 26th IEEE International Conference on Computer
        Communications. IEEE , vol., no., pp.1424,1432, 6-12 May 2007

   [14] PPSP WG Website

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   [15] A. Bakker, R. Petrocco, V. Grishchenko, "Peer-to-Peer Streaming
        Peer Protocol (PPSPP)", draft-ietf-ppsp-peer-protocol-08

   [16] Rui S. Cruz, Mario S. Nunes, Yingjie Gu, Jinwei Xia, Joao P.
        Taveira, Deng Lingli, "PPSP Tracker Protocol-Base Protocol
        (PPSP-TP/1.0)", draft-ietf-ppsp-base-tracker-protocol-02

   [17] A.Detti, B. Ricci, N. Blefari-Melazzi,"Peer-To-Peer Live
         Adaptive Video Streaming for Information Centric Cellular
         Networks", IEEE PIMRC 2013,London, UK, 8-11 September 2013


   [19] B. Fu, G. Kunzmann, M. Wetterwald, D. Corujo, R. Costa, "QoE-
        aware Traffic Management for Mobile Video Delivery", Proc. 2013
        IEEE  ICC,  Workshop  on  Immersive  &  Interactive  Multimedia
        Communications  over  the  Future  Internet  (IIMC),  Budapest,
        Hungary, Jun 2013.

   [20] Corujo D., Vidal I., Garcia-Reinoso J., Aguiar R., "A Named
        Data   Networking   Flexible   Framework   for   Management
        Communications", IEEE Communications Magazine, Vol. 50, no. 12,
        pp. 36-43, Dec 2012

   [21] Crabtree B., Stevens T., Allan B., Lederer S., Posch D.,
        Mueller C., Timmerer C., Video Adaptation in Limited or Zero
        Network Coverage, CCNxConn 2013,PARC, Palo Alto, pp. 1-2, 2013

   [22] Fiat A., Naor M., "Broadcast Encryption", in Advances in
        Cryptology (Crypto'93), volume 773 of Lecture Notes in Computer
        Science, pages 480-491. Springer Berlin / Heidelberg, 1994.

   [23]  Posch  D.,  Hellwagner  H.,  Schartner  P.,  "On-Demand  Video
        Streaming based on Dynamic Adaptive Encrypted Content Chunks",                                        th             in Proceedings of the 8  International Workshop on Secure
        Network  Protocols  (NPSec'13),  Los  Alamitos,  IEEE  Computer
        Society Press, October, 2013.

   [24]  Montpetit M.J., Westphal C., Trossen D., "Network Coding Meets
        Information Centric Networks," in Proceedings of the workshop
        on Name-Oriented Mobility (NOM), jointly with ACM MobiHoc 2013,
        Hilton Head, SC, June 2013.

   [25] Le Callet P., Moeller S.  and  Perkis A. (eds.),  Qualinet
        White  Paper  on  Definitions  of  Quality  of  Experience
        (2012). European Network on Quality of Experience in Multimedia

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        Systems  and   Services  (COST  Action  IC  1003),  Lausanne,
        Switzerland, Version 1.2, March 2013.

   [26] Medard M., Kim M., ParandehGheibi M., Zeng W., Montpetit M.J.,
        Quality of Experience for Multimedia Communications: Network
        Coding Strategies, Technical Report, MIT, 2012/3

   [27] Montpetit M.J., Holtzman H., Chakrabarti K., Matijasevic M.,
        Social  video  consumption:  Synchronized  viewing  experiences
        across devices and networks, IEEE International Conference on
        Communications Workshops (ICC), 2013, 286-290

   [28] Su K., Westphal C., On the Benefit of Information Centric
        Networks for Traffic Engineering, IEEE ICC Conference, June

   [29] Chanda A., Westphal C., Raychaudhuri D., Content Based Traffic
        Engineering in Software Defined Information Centric Networks,
        in IEEE INFOCOM Workshop NOMEN'13, April, 2013

   [30] Castro M., Druschel P., Kermarrec A.-M., Nandi A., Rowstron A.,
        Singh A. SplitStream: Highbandwidth multicast in cooperative
        environments. In Proceedings of ACM SOSP (2003).

   [31] ATIS     IPTV     Interoperability     Forum,     ATIS     IFF,

 14. Authors' Addresses

   Stefan Lederer, Christian Timmerer, Daniel Posch
   Alpen-Adria University Klagenfurt
   Universitaetsstrasse 65-67, 9020 Klagenfurt, Austria

   Email: {firstname.lastname}

   Cedric Westphal, Aytac Azgin. Shucheng (Will) Liu
   2330 Central Expressway, Santa Clara, CA95050, USA

   Email: {cedric.westphal,aytac.azgin,liushucheng}

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   Christopher Mueller
   bitmovin GmbH
   Lakeside B01, 9020 Klagenfurt, Austria


   Andrea Detti
   Electronic Engineering Dept.
   University of Rome Tor Vergata
   Via del Politecnico 1, Rome, Italy


   Daniel Corujo,
   Advanced Telecommunications and Networks Group
   Instituto de Telecomunicacoes
   Campus Universitario de Santiago
   P-3810-193 Aveiro, Portugal


   Jianping Wang
   City University of Hong Kong
   Hong Kong, China


   Marie-Jose Montpetit


   Niall Murray
   Dept. of Electronic, Computer and Software Engineering
   Athlone Institute of Technology
   Dublin Rd., Athlone, Ireland


 15. Acknowledgements

   This work was supported in part by the EC in the context of the
   SocialSensor (FP7-ICT-287975) project and partly performed in the
   Lakeside Labs research cluster at AAU. SocialSensor receives
   research funding from the European Community's Seventh Framework
   Programme. The work for this document was also partially performed

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Internet-Draft    Adaptive Video Streaming over ICN          April 2016

   in the context of the FP7/NICT EU-JAPAN GreenICN project, Apart from this, the European Commission
   has no responsibility for the content of this draft. The information
   in this document is provided as is and no guarantee or warranty is
   given that the information is fit for any particular purpose. The
   user thereof uses the information at its sole risk and liability.
   The authors would like to thank Shucheng (Will) Liu from Huawei for
   supporting Dr. Wang's research and Marie-Jose Montpetit of MIT for
   her help in writing the AAA for DRM section.

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