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INTERNET-DRAFT                                                  R. Huang
Intended Status: Informational                                    Huawei
Expires: August 18, 2014                                        Y. Zhang
                                                                 CoolPad
                                                       February 14, 2014


                 Survey of WebRTC based P2P Streaming
                 draft-huang-ppsp-p2p-webrtc-survey-00


Abstract

   This document presents a survey of current emerging WebRTC based P2P
   streaming applications available on the nowadays Internet.

Status of this Memo

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

   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
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   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/1id-abstracts.html

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


Copyright and License 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



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   to this document. Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



Table of Contents

   1  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3  Traditional P2P Streaming Applications on Browsers  . . . . . .  4
   4  WebRTC based P2P Applications . . . . . . . . . . . . . . . . .  5
     4.1 Swarm CDN  . . . . . . . . . . . . . . . . . . . . . . . . .  5
     4.2 PeerCDN  . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     4.3 Sharefest  . . . . . . . . . . . . . . . . . . . . . . . . .  7
     4.4 P2P Media Streaming with HTML5 and WebRTC  . . . . . . . . .  8
   5  Discussion  . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     5.1  Incorporating P2P Streaming in RTCWEB Scenarios . . . . . .  9
     5.2  Open Issues . . . . . . . . . . . . . . . . . . . . . . . .  9
   6  Security Considerations . . . . . . . . . . . . . . . . . . . . 10
   7  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 10
   8  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 10
   9  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     9.1  Informative References  . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11

























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1  Introduction

   P2P streaming applications usually use standard or private P2P
   protocol to deliver content between their end users. Some of them
   uses specific desktop software as the client which end users have to
   download and install in their OS. The others uses browsers as
   clients, but users still need to download corresponding plug-ins to
   enable the P2P transmission.

   WebRTC is a new software architecture which enable web browsers with
   Real Time Communication (RTC) capabilities via simple JavaScript
   APIs. It provides direct interactive communications using audio,
   video, etc. between two peers' web-browsers without any additional
   plug-ins. Currently, WebRTC only focuses on conversational
   applications such as VoIP and video conferencing, multimedia
   streaming systems are not considered. However, the interests towards
   WebRTC is strongly increasing. An ever-increasing number of P2P
   applications have adopted WebRTC to distribute multimedia content or
   file sharing from a source to a large number of endpoints only via
   browsers without installing any plug-ins. This document presents a
   survey of current emerging WebRTC based P2P streaming applications
   available on the nowadays Internet.

   the remainder of this document is organized as follows: Section 2
   introduces terminology used throughout the survey; Section 3 provide
   the analysis of how traditional P2P streaming applications on
   browsers work; Section 4 presents current emerging WebRTC based P2P
   streaming applications.

2  Terminology

   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].

   Plug-in: a piece of software which enhances another software
   application and usually cannot be run independently.

   API: Application Programming Interface - a specification of a set of
   calls and events, usually tied to a programming language or an
   abstract formal specification such as WebIDL, with its defined
   semantics.

   Peer: A peer refers to a participant in a P2P streaming system that
   not only receives streaming content, but also caches and forwards
   streaming content to other participants.

   Tracker: A tracker refers to a directory service that maintains a



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   list of peers participating in a specific audio/video source or in
   the distribution of a streaming file. A tracker answers queries
   received from peers for the information of other peers sharing the
   same streaming content. A tracker is a logical component which could
   be centralized or distributed.

   Tracker protocol: A signaling protocol between trackers and peers.

   Peer protocol: A signaling and data protocol among the peers.

3  Traditional P2P Streaming Applications on Browsers

   Some of traditional P2P streaming applications also allow their users
   to obtain their content via browsers. The browsers are required to
   install some plug-ins provided by these content providers firstly.
   After that, the browsers of end users download and run specific
   JavaScript application from content server. The JavaScript
   application will act as a peer of P2P network to connect to a tracker
   and get a list of available peers via tracker protocol. With the help
   of plug-ins, the JavaScript application will then be able to
   communicate with other peers exchanging content via standard or
   private peer protocol.

            +---------+         +---------+
            |         |         |         |
            |  web    |         |         |
            |         |         | Tracker |
            |  Server |         |         |
            |         |         |         |
            +---------+         +---------+
                 |              /       \
                 |             /         \
                 |            /           \
       HTTP/     |           /             \
       WebSockets|          /               \
                 |         /Tracker          \ Tracker
                 |        / Protocol          \Protocol
                 |       /                     \
                 |      /                       \
                 |     /                         \
                 |    /                           \
                 |   /                             \
         +-----------++---+                +-----------+
         |JS/HTML/CSS|| P |                |           |
         +-----------+| l |   Peer         |           |
         +-----------+| u |   Protocol     | Seeders/  |
         |           || g +----------------+other Peers|
         |           || | |                |           |



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         |  Browser  || i |                |           |
         |           || n |                |           |
         +-----------++---+                +-----------+

      Figure 1 Traditional P2P Streaming Applications on Browsers

   Adobe's Flash Player is a typical example of such usage. It has
   cooperated with many content providers, e.g. Sohu video, to support
   P2P video streaming. It also provides APIs to help developers to be
   able to use flash player to build various other P2P applications
   right within the browsers. But the browsers of these users will be
   required to install or update the plug-ins of Flash Player. Flash
   Player has provided the ability of peer-to-peer communication since
   version 10.1.

4  WebRTC based P2P Applications

   WebRTC is a collection of technologies, including a media connection
   protocol (which is RTP) that can be used to initiate sessions like
   video conversation, a data exchange protocol that will enable users
   to transfer data, e.g. chat or files, without the need for a third-
   party server, and a way to access local resources, e.g. user's
   microphone and video camera. WebRTC is created to facilitate
   conversational communications from web browsers. However, it is not
   the only usage WebRTC turns out to be. Recently, some innovative
   applications and projects are using WebRTC technology on peer-to-peer
   connections to accomplish tasks like streaming and sharing, instead
   of relying on third-party plug-ins or proprietary software. They all
   rely on WebRTC's data channel protocol, which is designed to allow
   browsers to exchange data other than audio or video. Some of the
   typical WebRTC based P2P applications are presented as follow, but
   not exhaustive. Currently, the data channel protocol has been
   implemented in Chromes as well as Firefox, which means that current
   WebRTC based P2P applications are only supported in these two types
   of browsers.

4.1 Swarm CDN

   Swarm CDN is a new peer-to-peer browser based content delivery
   network using WebRTC technology to save web site owners' money,
   reduce their bandwidth and reduce server costs. Instead of hosting
   the content on servers in data centers, Swarm CDN provides a way for
   users to deliver content to other users on the same site without
   installing any plug-ins.

   Figure 2 demonstrates the rough architecture of this system.





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            +---------+         +---------+
            |         |         |         |
            |  web    |         |         |
            |         |         | Tracker |
            |  Server |         |         |
            |         |         |         |
            +---------+         +---------+
                 |             /         \
                 |            /           \
       HTTP/     |           /             \
       WebSockets|          /               \
                 |         /Tracker          \ Tracker
                 |        / Protocol          \Protocol
                 |       /  over HTTP          \ over HTTP
                 |      /                       \
                 |     /                         \
         +----------------+                +-----------+
         |JS/HTML/CSS     |                |JS/HTML/CSS|
         +----------------|                +-----------+
         +----------------|  Data Channel  +-----------+
         |                |----------------|           |
         |                |                |           |
         |  Browser       |                | Browser   |
         |                |                |           |
         +----------------+                +-----------+

              Figure 2 WebRTC based P2P Applications

   Swarm CDN provides plug-ins to content providers or modifies their
   sites' HTML code so that peers made up of the users's browsers will
   be redirected to a centralized server which is called tracker in this
   memo. As depicted from the above figure, after the web page is loaded
   from the original web server, the peer will join the P2P network by
   establishing a HTTP connection to the centralized server which holds
   connections to a certain number of peers that have recently joined
   the network. Afterwards, this HTTP connection is used to signal the
   WebRTC handshake, resulting in a direct WebRTC data channel between
   the newly joined client and one of the other clients that has the
   content. For those users on a non compatible WebRTC browsers, the
   tracker will detect this and default them to retrieve the requested
   content from the original web servers.

   Swarm CDN could provide service for video and images. Currently, it's
   free and able to swarm video and images for 20 simultaneous users.

4.2 PeerCDN

   PeerCDN helps web applications build a peer-to-peer content delivery



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   network (CDN) that will make the web faster, more reliable, and help
   sites to reduce bandwidth costs. The technology of PeerCDN is similar
   to Swarm CDN, which uses WebRTC encrypted data channel for data
   transmission. It also requires users to insert a single line of HTML
   code to enable the usage without any browser plug-ins. Afterwards, a
   web browser triggers a notification to the peerCDN's tracking server
   that they are visiting the page. If someone else visits this page at
   the same time, peerCDN automatically sets up a connection and quietly
   streams the data between the peers. PeerCDN serves a site's static
   assets, such as images, streaming videos and file downloads. It only
   works on all WebRTC browsers.

   PeerCDN was founded by Stanford engineering graduate in early 2013.
   And Yahoo has bought this startup company in December of 2013.

4.3 Sharefest

   Sharefest is a file sharing application developed by a video
   streaming company called Peer5. Different from tools like Dropbox
   transferring files to the remote server then back again, Sharefest
   creates peer-to-peer communication between browsers directly using
   WebRTC.

   Figure 3 depicts the architecture of Sharefest.
                     +------------+
                     | Web Server |
                     +------------+
                    /      |       \
                   /       |        \
                  /  +------------+  \
                 /   |  Browser   |   \
                /    +------------+    \
               /    *     ||        *   \
              /    *      ||         *   \
             /    *  +------------+   *   \
            /    *   |Sharefest   |    *   \
           /    *    |Server      |     *   \
          /    *     +------------+      *   \
         /    *    //             \\      *   \
        /    *    //               \\      *   \
      +------------+               +----------------+
      |   Browser  |***************|   Browser      |
      +------------+               +----------------+
                                                  ---- Signaling
                                                  ==== Sharefest tracker
                                                       protocol
                                                  **** Data channel
              Figure 3 Architecture of Sharefest



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   The Sharefest server presents an auto-generated short-URL for each
   file shared by the client wishing to share. When a client browser
   visits the URL, the server connects it to the sharing client's
   browser and the sharing client's browser transfers the file over an
   WebRTC data channel. If multiple clients connect from different
   locations, the server attempts to pair nearby clients to each other
   to maximize the overall throughput. Sharefest utilizes some simple
   p2p technologies like slicing. It does its best to maximize
   efficiency by dividing each file into slices that the downloading
   peers exchange with each other.

   Currently the size limit for shared files is around 1 GB and only the
   recent versions of Chrome and Firefox are supported.

4.4 P2P Media Streaming with HTML5 and WebRTC

   Some students from Aalto university have proposed an experimental
   system for P2P VoD service applying WebRTC standards. The experiment
   mirrors the BitTorrent architecture and the same entities - tracker,
   seeder and peers - are used. Peers and seeders could be WebRTC
   browsers. It can be seen in Figure 4.

                   +-----------------------------+
                   |                             |
                   |       Tracker Server        |
                   |                             |
                   |                             |
                   +-----------------------------+
                       |          |            |
                       |          |            |
                       |   +--------------+    |
                       |   |    Seeder    |    |
                       |   +--------------+    |
                       |      *          *     |
                       |      *          *     |
                   +------------+     +------------+
                   |   Peer 1   |*****|   Peer 2   |
                   +------------+     +------------+

                                           ---- Private tracker protocol
                                           **** Data channel

         Figure 4 Network Architecture for the P2P VoD service
                         with HTML5 and WebRTC

   Initially users or content provides create a torrent file containing
   the metadata of the video, hashes of each piece of the video and
   uploads the torrent file to the tracker. Media content is uploaded to



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   the seeder simultaneously. When a peer requests this content, it will
   obtain the metadata from the tracker and start to download the
   content slices from the seeder or original peer uploading the content
   or both. As the content becomes popular, subsequent peers could get
   the content from the nearby peers, which decrease the load on the
   seeder and original peer uploading the content.

   The experiment raises some considerations on this kind of
   implementations. The main concern is that the performance of MD5 on
   JavaScript and how much load could be handle in current solution
   generated. It points out that the resources available through
   browsers are much more limited than for native applications. The
   calculation of MD5 hashes use too much CPU consumption which will
   adversely affect the speed of getting content to play, especially for
   mobile devices. This experiment also indicates that handling two
   streams,incoming and outgoing, is manageable with current desktop and
   mobile devices. Increasing peers number will severely degrade
   performance and result in a bad user experience.

   As the capability of computing for both desktop and mobile devices is
   rapidly increasing, it can be anticipated that the above problems
   will be eliminated soon.


5  Discussion

5.1  Incorporating P2P Streaming in RTCWEB Scenarios

   As we have discussed in the above sections, there are more and more
   efforts on enabling p2p streaming using WebRTC technologies.
   According to the statistics of LTE usage in Verizon [Verizon], video
   streaming traffic is accounting the largest part of the LTE traffic
   and it slows down the wireless download speed by 20 percentages.
   Using p2p streaming is an efficient means to solve the traffic
   pressure not only in the core network, backbone but also in the air
   interface especially when Device to Device mode (D2D) is deployed
   between the browsers of end nodes, which is in the standardization
   process in 3GPP. Although RTCWEB is created to facilitate JavaScript
   APIs for real-time communication in the browser without implementing
   any plug-ins, the current scope of RTCWEB only includes
   conversational applications not streaming systems. We can see that
   web applications supporting p2p streaming without plug-ins are more
   and more appealing. So is it possible to incorporate P2P streaming in
   RTCWEB scenarios so as to implement JavaScript APIs for P2P
   algorithms as part of the WebRTC standardization process?

5.2  Open Issues




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   Several open issues need to be addressed for the purpose described in
   Section 5.1:

   1. Do we need WebRTC to support P2P algorithms? If yes, how to
   support?

   2. Do we need WebRTC to support the tracker protocol? If yes, how to
   support?

   3. Do we need WebRTC to support the peer protocol? If yes, how to
   support?

   4. Is there any security problems?

6  Security Considerations

   This document has no security concern.

7  IANA Considerations

   This document has no actions for IANA.

8  Acknowledgments

   TBD.

9  References

9.1  Informative References

   [RFC6972] RFC 6972, "Problem Statement and Requirements of the Peer-
   to-Peer Streaming Protocol (PPSP)"

   [SwarmCDN] Swarm CDN web site, http://swarmcdn.com/

   [PeerCDN] Peer CDN web site, https://peercdn.com/?

   [Sharefest] Sharefest web site, http://www.sharefest.me/?

   [PPMSHW] J. Nurminen, A. Meyn, et al., "P2P Media Streaming with
   HTML5 and WebRTC", February 2013

   [Verizon] http://www.fiercewireless.com/tech/story/verizon-spending-
   millions-network-upgrades-counter-growth-video-traffic/2013-12-16







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Authors' Addresses


   Rachel Huang
   Huawei
   Phone: +86-25-56623633

   EMail: rachel.huang@huawei.com



   Yunfei Zhang
   Coolpad

   EMail: hishigh@gmail.com




































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