[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04 05 06 07 08 RFC 7933

ICNRG                                                         S. Lederer
Internet Draft                                                  D. Posch
Intended status: Informational                               C. Timmerer
Expires: May 20, 2015                      Alpen-Adria University Klagenfurt
                                                        C. Westphal, Ed.
                                                             Aytac Azgin
                                                                  Huawei
                                                              C. Mueller
                                                                Bitmovin
                                                                 A.Detti
                                          University of Rome Tor Vergata
                                                               D. Corujo
                                                    University of Aveiro


                                                      November 21, 2014

                     Adaptive Video Streaming over ICN
                   draft-irtf-icnrg-videostreaming-02.txt

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79. This document may not be modified,
   and derivative works of it may not be created, and it may not be
   published except as an Internet-Draft.

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79. This document may not be modified,
   and derivative works of it may not be created, except to publish it
   as an RFC and to translate it into languages other than English.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008. The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.





Lederer, et al.          Expires May 10, 2015                  [Page 1]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other documents
   at any time.  It is inappropriate to use Internet-Drafts as
   reference material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html

   This Internet-Draft will expire on May 10, 2014.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with
   respect to this document.

Abstract

   This document considers the consequences of moving the underlying
   network architecture 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 MPEG Dynamic Adaptive Streaming
   over HTTP (DASH) standard; we consider layered encoding over ICN;
   P2P mechanisms introduce distinct requirements for video and we look
   at how to adapt PPSP for ICN; IPTV adds delay constraints, and this
   will create more stringent requirements over ICN as well. As part of
   the discussion on video, we discuss DRMs in ICN. Finally, in
   addition to consider how existing mechanisms would be impacted by



Lederer, et al.          Expires May 10, 2015                  [Page 2]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   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..................................................... 6
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 ....................... 8
   5.3.1. Interaction of DASH and ICN ................................ 8
   5.3.2. Interaction of ICN with Layered Encoding .................. 11
 5.4. Possible Integration of Video streaming and ICN architecture .. 11
   5.4.1. DASH over CCN ............................................. 11
   5.4.2. Testbed, Open Source Tools, and Dataset ................... 13
6. P2P video distribution and ICN.................................... 14
 6.1. Introduction to PPSP  ......................................... 14
 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 ...................... 16
   6.2.3. Support of PPSP interaction through a pull-based ICN API .. 17
   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 ................................... 19
 6.3. Impact of MPEG DASH coding schemes ............................ 20
7. IPTV and ICN...................................................... 21
 7.1. IPTV challenges ............................................... 21
 7.2. ICN benefits for IPTV delivery ................................ 22
8. Digital Rights Managements in ICN................................. 24
9. Future Steps for Video in ICN..................................... 27
 9.1. Large Scale Live Events ....................................... 27
 9.2. Video Conferencing and Real-Time Communications ............... 28
 9.3. Store-and-Forward Optimized Rate Adaptation  .................. 28
 9.4. Heterogeneous Wireless Environment Dynamics ................... 29
 9.5. Network Coding for Video Distribution in ICN .................. 30
10. Security Considerations.......................................... 31
11. IANA Considerations.............................................. 31



Lederer, et al.          Expires May 10, 2015                  [Page 3]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


12. Conclusions...................................................... 31
13. References....................................................... 31
 13.1. Normative References ......................................... 31
 13.2. Informative References ....................................... 32
14. Authors' Addresses............................................... 34
15. Acknowledgements................................................. 35




 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 ICN working 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 short- to mid-
   term 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.

   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].



Lederer, et al.          Expires May 10, 2015                  [Page 4]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   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",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   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.

   In this document, the characters ">>" preceding an indented line(s)
   indicates a compliance requirement statement using the key words
   listed above. This convention aids reviewers in quickly identifying
   or finding the explicit compliance requirements of this RFC.

 3. Use case scenarios for ICN and Video Streaming

   For ICN specific descriptions, we refer to the other working 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. 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):





Lederer, et al.          Expires May 10, 2015                  [Page 5]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   - a video delivery architecture similar to that if itune, 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;
   - 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
   mechanisms.

   This research items include videoconferencing and real-time video
   communications, which 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 protocol.

 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.



Lederer, et al.          Expires May 10, 2015                  [Page 6]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   However, current mechanisms are built atop existing transport
   protocol. Some ICN proposals (say, CCN or NDN for instance) attempt
   to leverage the work down 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
   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


Lederer, et al.          Expires May 10, 2015                  [Page 7]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   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, bitrates, 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
   capabilities.

   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 bitrate, 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.

   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.


Lederer, et al.          Expires May 10, 2015                  [Page 8]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   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 sources.

   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:

   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
      bandwidth.

   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.






Lederer, et al.          Expires May 10, 2015                  [Page 9]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   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
      representations.

   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.

   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].






Lederer, et al.          Expires May 10, 2015                 [Page 10]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


          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);
     . 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.

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.


Lederer, et al.          Expires May 10, 2015                 [Page 11]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   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.
   As 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
   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



Lederer, et al.          Expires May 10, 2015                 [Page 12]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   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
   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 and a seamless handover between them, which
   again comes together with bandwidth changes, e.g., switching between
   fixed and wireless, 3G/4G and WiFi networks, 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 condition. 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.




Lederer, et al.          Expires May 10, 2015                 [Page 13]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   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
   http://www.github.com/bitmovin/libdash. 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
   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
   testbed.

 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. 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 more the number of stream received,



Lederer, et al.          Expires May 10, 2015                 [Page 14]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   the higher the video quality. A peer control video rate by fetching
   or not the streams delivered on 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.

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



Lederer, et al.          Expires May 10, 2015                 [Page 15]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   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
   (PPSP-TP)[16].

   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),
   etc.

   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
   be wrapped as named-data items, and receivers should request them by
   name.




Lederer, et al.          Expires May 10, 2015                 [Page 16]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   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, like to fetch a DATA message (i.e. a
   video chunk), what it is relevant for a peer is just to receive the
   requested content, independently from who is the endpoint that
   generate the data. We refer 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 n. 1 may be named as
   "ccnx:/swarmID/chunk/chunkID", where swarmID is a unique identifier
   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
             API

   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



Lederer, et al.          Expires May 10, 2015                 [Page 17]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   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
   message.

          6.2.4. Abstract layering for PPSP over ICN

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


Lederer, et al.          Expires May 10, 2015                 [Page 18]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


                    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
   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.


Lederer, et al.          Expires May 10, 2015                 [Page 19]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   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.
   one entry per video chunk, and these entries are difficult to be
   aggregated since peers avail 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 valuably decrease the
   effectiveness of P2P cooperation and of in-network caching,
   depending of the kind of the video coding used by the MPEG DASH
   stream.

   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


Lederer, et al.          Expires May 10, 2015                 [Page 20]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   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. The estimation of
   the best coding rate is usually handled by receiver-driven
   algorithms, implemented by the video client.

   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 avails of chunks 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.

   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


Lederer, et al.          Expires May 10, 2015                 [Page 21]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   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. 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);
   (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. 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 challenge).

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.





Lederer, et al.          Expires May 10, 2015                 [Page 22]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   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 increase (including the same session
        at different quality levels), so as 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 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 degradatory
        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


Lederer, et al.          Expires May 10, 2015                 [Page 23]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


        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.



 8. Digital Rights Managements in ICN

   This section discusses the need for Digital Rights Management (DRM)
   functionalities for multimedia streaming over ICN. The discussion
   will show that Broadcast Encryption (BE) is 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.

   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 creater 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.

   In ICN, data packets can be cached inherently in the network and any
   network participant can request a copy of these packets. This makes


Lederer, et al.          Expires May 10, 2015                 [Page 24]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   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
   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)
   are:

     . 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
        LA.
     . The participants can agree on a common session key, which is
        chosen by the LA. The LA broadcasts an encrypted message that


Lederer, et al.          Expires May 10, 2015                 [Page 25]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


        includes the key. Participants with a valid set of secrets can
        derive the session-key from this message.
     . 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 secretes has been gathered. Note that secrets may
        become compromised because of two reasons. First, if the secret
        has been illegally revealed by a traitor. Second, if the
        subscription of an entity expires. 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.


Lederer, et al.          Expires May 10, 2015                 [Page 26]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


     . Since the amount of required computational resources may vary
        strongly from time to time it would be beneficial for any
        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.



 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


Lederer, et al.          Expires May 10, 2015                 [Page 27]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   events such as sports event in a stadium, a concert or a large
   demonstration.

   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 communication add timing constraints
   (both in terms of delay and in terms of synchronization) to the
   scenario discussed above.

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
   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
   link.

   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.


Lederer, et al.          Expires May 10, 2015                 [Page 28]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   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 can not 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
   end-user, which is of utmost importance when it comes to video
   content.

   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.



Lederer, et al.          Expires May 10, 2015                 [Page 29]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   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
     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].

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



Lederer, et al.          Expires May 10, 2015                 [Page 30]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   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.

 10. Security Considerations

   This is informational. Security considerations are TBD.

 11. IANA Considerations

   This is informational. IANA considerations are TBD.

 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
   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
             2013




Lederer, et al.          Expires May 10, 2015                 [Page 31]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


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.

   [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,
         2012.

   [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.




Lederer, et al.          Expires May 10, 2015                 [Page 32]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


   [9]   DASH Research at the Institute of Information Technology,
         Multimedia Communication Group, Alpen-Adria Universitaet
         Klagenfurt, URL: http://dash.itec.aau.at

   [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 2011

   [12] NetInf project Website http://www.netinf.org

   [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, pp.1424,1432,
             6-12 May 2007

   [14] PPSP WG Website https://datatracker.ietf.org/wg/ppsp/

   [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

   [18] http://www.ict-medieval.eu

   [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


Lederer, et al.          Expires May 10, 2015                 [Page 33]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


        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", 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.

 14. Authors' Addresses

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

   Email: {firstname.lastname}@itec.aau.at


   Cedric Westphal, Aytac Azgin
   Huawei
   2330 Central Expressway, Santa Clara, CA95050, USA

   Email: {first.last}@huawei.com


   Christopher Mueller
   bitmovin GmbH
   Lakeside B01, 9020 Klagenfurt, Austria

   Email: christopher.mueller@bitmovin.net






Lederer, et al.          Expires May 10, 2015                 [Page 34]


Internet-Draft    Adaptive Video Streaming over ICN       November 2014


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

   Email: andrea.detti@uniroma2.it

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

   Email: dcorujo@av.it.pt



 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
   in the context of the FP7/NICT EU-JAPAN GreenICN project,
   http://www.greenicn.org. 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.



















Lederer, et al.          Expires May 10, 2015                 [Page 35]


Html markup produced by rfcmarkup 1.129c, available from https://tools.ietf.org/tools/rfcmarkup/