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rfc:rfc6646

Internet Engineering Task Force (IETF) H. Song Request for Comments: 6646 N. Zong Category: Informational Huawei ISSN: 2070-1721 Y. Yang

                                                       Yale University
                                                              R. Alimi
                                                                Google
                                                             July 2012
   DECoupled Application Data Enroute (DECADE) Problem Statement

Abstract

 Peer-to-peer (P2P) applications have become widely used on the
 Internet today and make up a large portion of the traffic in many
 networks.  In P2P applications, one technique for reducing the
 transit and uplink P2P traffic is to introduce storage capabilities
 within the network.  Traditional caches (e.g., P2P and Web caches)
 provide such storage, but they can be complex (e.g., P2P caches need
 to explicitly support individual P2P application protocols), and do
 not allow users to manage resource usage policies for content in the
 cache.  This document discusses the introduction of in-network
 storage for P2P applications and shows the need for a standard
 protocol for accessing this storage.

Status of This Memo

 This document is not an Internet Standards Track specification; it is
 published for informational purposes.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Not all documents
 approved by the IESG are a candidate for any level of Internet
 Standard; see Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc6646.

Song, et al. Informational [Page 1] RFC 6646 DECADE Problem Statement July 2012

Copyright Notice

 Copyright (c) 2012 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.  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 ....................................................2
 2. Terminology and Concepts ........................................3
 3. The Problems ....................................................4
    3.1. P2P Infrastructural Stress and Inefficiency ................4
    3.2. P2P Cache: A Complex Type of In-Network Storage ............5
    3.3. Ineffective Integration of P2P Applications ................6
 4. Usage Scenarios .................................................6
    4.1. BitTorrent .................................................6
    4.2. Content Publisher ..........................................7
 5. Security Considerations .........................................8
    5.1. Denial-of-Service Attacks ..................................8
    5.2. Copyright and Legal Issues .................................8
    5.3. Traffic Analysis ...........................................8
    5.4. Modification of Information ................................8
    5.5. Masquerade .................................................9
    5.6. Disclosure .................................................9
    5.7. Message Stream Modification ................................9
 6. Acknowledgments .................................................9
 7. Informative References .........................................10

1. Introduction

 Peer-to-peer (P2P) applications, including both P2P streaming and P2P
 file-sharing applications, make up a large fraction of the traffic in
 many Internet Service Provider (ISP) networks today.  One way to
 reduce bandwidth usage by P2P applications is to introduce storage
 capabilities in networks.  Allowing P2P applications to store and
 retrieve data from inside networks can reduce traffic on the last-
 mile uplink, as well as on backbone and transit links.

Song, et al. Informational [Page 2] RFC 6646 DECADE Problem Statement July 2012

 Existing P2P caches provide in-network storage and have been deployed
 in some networks.  However, the current P2P caching architecture
 poses challenges to both P2P cache vendors and P2P application
 developers.  For P2P cache vendors, it is challenging to support a
 number of continuously evolving P2P application protocols, due to
 lack of documentation, ongoing protocol changes, and rapid
 introduction of new features by P2P applications.  For P2P
 application developers, closed P2P caching systems limit P2P
 applications from effectively utilizing in-network storage.  In
 particular, P2P caches typically do not allow users to explicitly
 store content into in-network storage.  They also do not allow
 applications to specific resource and access control policies over
 the usage of in-network storage.  The challenges, if not addressed,
 may lead to reduced efficiency for P2P applications, and increased
 load on the network infrastructure.
 The challenges can be effectively addressed by using a standard, open
 protocol to access in-network storage [Data_Lockers].  P2P
 applications can store and retrieve content in the in-network
 storage, as well as control resources (e.g., bandwidth, connections)
 consumed by peers in a P2P application.  As a simple example, a peer
 of a P2P application may upload to other peers through its in-network
 storage, saving its usage of last-mile uplink bandwidth.
 In this document, we distinguish between two functional components of
 the native P2P application protocol: signaling and data access.
 Signaling includes operations such as handshaking and discovering
 peer and content availability.  The data access component transfers
 content from one peer to another.
 In essence, coupling of the signaling and data access makes
 in-network storage complex to support various application services.
 However, these applications have common requirements for data access,
 making it possible to develop a standard protocol.

2. Terminology and Concepts

 The following terms have special meaning in the definition of the
 in-network storage system.
 In-network storage:  A service inside a network that provides storage
    and bandwidth to network applications.  In-network storage may
    reduce upload/transit/backbone traffic and improve network
    application performance.  The position of in-network storage is in
    the core of a network -- for example, co-located with the border
    router (network attached storage) or inside a data center.

Song, et al. Informational [Page 3] RFC 6646 DECADE Problem Statement July 2012

 P2P cache (peer-to-peer cache):  A kind of in-network storage that
    understands the signaling and transport of specific P2P
    application protocols.  It caches the content for those specific
    P2P applications in order to serve peers and reduce traffic on
    certain links.

3. The Problems

 The emergence of P2P as a major network application (especially P2P
 file sharing and streaming) has led to substantial opportunities.
 The P2P paradigm can be utilized to design highly scalable and robust
 applications at low cost, compared to the traditional client-server
 paradigm.
 However, P2P applications also face substantial design challenges.  A
 particular challenge facing P2P applications is the additional stress
 that they place on the network infrastructure.  At the same time,
 lack of infrastructure support can lead to unstable P2P application
 performance, in particular during peer churns and flash crowds, when
 a large group of users begin to retrieve the content during a short
 period of time, leading to stress on bandwidth-constrained access
 uplinks.  A potential way to reduce network stress and improve P2P
 application performance would be to make it possible for peers that
 are on bandwidth-constrained access to put data in a place that is
 free of bandwidth constraints and also accessible by other peers.
 These problems are now discussed in further detail.

3.1. P2P Infrastructural Stress and Inefficiency

 A particular problem of the P2P paradigm is the stress that P2P
 application traffic places on the infrastructure of ISPs.  Multiple
 measurements (e.g., [ipoque_Internet_Study]) have shown that P2P
 traffic has become a major type of traffic on some networks.
 Furthermore, the inefficiency of network-agnostic peering (at the P2P
 transmission level) leads to unnecessary traversal across network
 domains or spanning the backbone of a network [RFC5693].
 Using network information alone to construct more efficient P2P
 swarms is not sufficient to reduce P2P traffic in access networks, as
 the total access upload traffic is equal to the total access download
 traffic in a traditional P2P system.  On the other hand, it is
 reported that P2P traffic is becoming the dominant traffic on the
 access networks of some networks, reaching as high as 50-60% on the
 downlinks and 60-90% on the uplinks [DCIA] [ICNP] [ipoque_P2P_Survey]
 [P2P_File_Sharing].  Consequently, it becomes increasingly important
 to reduce upload access traffic, in addition to cross-domain and
 backbone traffic.

Song, et al. Informational [Page 4] RFC 6646 DECADE Problem Statement July 2012

 The inefficiency of P2P is also observed when traffic is sent
 upstream as many times as there are remote peers interested in
 getting the corresponding information.  For example, the P2P
 application transfer completion times remain affected by potentially
 (relatively) slow upstream transmission.  Similarly, the performance
 of real-time P2P applications may be affected by potentially
 (relatively) higher upstream latencies.

3.2. P2P Cache: A Complex Type of In-Network Storage

 An effective technique to reduce P2P infrastructural stress and
 inefficiency is to introduce in-network storage.  A survey of
 existing in-network storage systems can be found in [RFC6392].
 In the current Internet, in-network storage is introduced as P2P
 caches, either transparently or explicitly as a P2P peer.  To provide
 service to a specific P2P application, the P2P cache server must
 support the specific signaling and transport protocols of the
 specific P2P application.  This can lead to substantial complexity
 for the P2P cache vendor.
 First, there are many P2P applications on the Internet (e.g.,
 BitTorrent, eMule, Flashget, and Thunder for file sharing; Abacast,
 Kontiki, Octoshape, PPLive, PPStream, and UUSee for P2P streaming).
 Consequently, a P2P cache vendor faces the challenge of supporting a
 large number of P2P application protocols, leading to product
 complexity and increased development cost.
 Second, a specific P2P application protocol may evolve continuously
 to add new features or fix bugs.  This in turn forces a P2P cache
 vendor to continuously monitor application updates to track such
 changes, leading to product complexity and increased costs.
 Third, many P2P applications use proprietary protocols or support
 end-to-end encryption.  This can render P2P caches ineffective.
 Therefore, these three problems make it difficult to use the P2P
 cache as a network middlebox to support P2P application distribution.
 Finally, an end host has better connectivity and connection quality
 to a P2P cache than to a remote peer.  Without the ability to manage
 bandwidth usage, the P2P cache may increase the volume of download
 traffic, which runs counter to the reduction of upload access
 traffic.

Song, et al. Informational [Page 5] RFC 6646 DECADE Problem Statement July 2012

3.3. Ineffective Integration of P2P Applications

 As P2P applications evolve, it has become increasingly clear that
 usage of in-network resources can improve the user's experience.  For
 example, multiple P2P streaming systems seek additional in-network
 resources during a flash crowd, such as just before a major live
 streaming event.  In asymmetric networks, when the aggregated upload
 bandwidth of a channel cannot meet the download demand, a P2P
 application may seek additional in-network resources to maintain a
 stable system.
 However, some P2P applications using in-network infrastructural
 resources require flexibility in implementing resource allocation
 policies.  A major competitive advantage of many successful P2P
 systems is their substantial expertise in how to most efficiently
 utilize peer and infrastructural resources.  For example, many live
 P2P systems have specific algorithms to select those peers that
 behave as stable, higher-bandwidth sources.  Similarly, the higher-
 bandwidth sources frequently use algorithms to choose to which peers
 the source should send content.  Developers of these systems continue
 to fine-tune these algorithms over time.
 To permit developers to evolve and fine-tune their algorithms and
 policies, the in-network storage should expose basic mechanisms and
 allow as much flexibility as possible to P2P applications.  This
 conforms to the end-to-end systems principle and allows innovation
 and satisfaction of specific business goals.  Existing techniques for
 in-network storage in P2P applications lack these capabilities.

4. Usage Scenarios

 Usage scenarios are presented to illustrate the problems in both
 Content Distribution Network (CDN) and P2P scenarios.

4.1. BitTorrent

 When a BitTorrent client A uploads a block to multiple peers, the
 block traverses the last-mile uplink once for each peer.  After that,
 the peer B that just received the block from A also needs to upload
 through its own last-mile uplink to others when sharing this block.
 This is not an efficient use of the last-mile uplink.  With an
 in-network storage server, however, the BitTorrent client may upload
 the block to its in-network storage.  Peers may retrieve the block
 from the in-network storage, reducing the amount of data on the
 last-mile uplink.  If supported by the in-network storage, a peer can
 also save the block in its own in-network storage while it is being
 retrieved; the block can then be uploaded from the in-network storage
 to other peers.

Song, et al. Informational [Page 6] RFC 6646 DECADE Problem Statement July 2012

 As previously discussed, BitTorrent or other P2P applications
 currently cannot explicitly manage which content is placed in the
 existing P2P caches, nor can they manage access and resource control
 policies.  Applications need to retain flexibility to control the
 content distribution policies and topology among peers.

4.2. Content Publisher

 Content publishers may also utilize in-network storage.  For example,
 consider a P2P live streaming application.  A Content Publisher
 typically maintains a small number of sources, each of which
 distributes blocks in the current play buffer to a set of P2P peers.
 Some content publishers use another hybrid content distribution
 approach incorporating both P2P and CDN modes.  As an example,
 Internet TV may be implemented as a hybrid CDN/P2P application by
 distributing content from central servers via a CDN, and also
 incorporating a P2P mode amongst end hosts and set-top boxes.
 In-network storage may be beneficial to hybrid CDN/P2P applications
 as well to support P2P distribution and to enable content publisher
 standard interfaces and controls.
 However, there is no standard interface for different content
 publishers to access in-network storage.  One streaming content
 publisher may need the existing in-network storage to support
 streaming signaling or another such capability, such as transcoding
 capability, bitmap information, intelligent retransmission, etc.,
 while a different content publisher may only need the in-network
 storage to distribute files.  However, it is reasonable that the
 application services are only supported by content publishers'
 original servers and clients, and intelligent data plane transport
 for those content publishers are supported by in-network storage.
 A content publisher also benefits from a standard interface to access
 in-network storage servers provided by different providers.  The
 standard interface must allow content publishers to retain control
 over content placed in their own in-network storage and to grant
 access and resources only to the desired end hosts and peers.
 In the hybrid CDN/P2P scenario, if only the end hosts can store
 content in the in-network storage server, the content must be
 downloaded and then uploaded over the last-mile access link before
 another peer may retrieve it from an in-network storage server.
 Thus, in this deployment scenario, it may be advantageous for a
 content publisher or CDN provider to store content in in-network
 storage servers.

Song, et al. Informational [Page 7] RFC 6646 DECADE Problem Statement July 2012

5. Security Considerations

 There are several security considerations related to in-network
 storage.

5.1. Denial-of-Service Attacks

 An attacker can try to consume a large portion of the in-network
 storage, or exhaust the connections of the in-network storage through
 a denial-of-service (DoS) attack.  Authentication, authorization, and
 accounting mechanisms should be considered in the cross-domain
 environment.  Limitation of access from an administrative domain sets
 up barriers for content distribution.

5.2. Copyright and Legal Issues

 Copyright and other laws may prevent the distribution of certain
 content in various localities.  In-network storage operators may
 adopt system-wide ingress or egress filters to implement necessary
 policies for storing or retrieving content, and applications may
 apply Digital Rights Management (DRM) to the data stored in the
 network storage.  However, the specification and implementation of
 such policies (e.g., filtering and DRM) is not in scope for the
 problem this document proposes to solve.

5.3. Traffic Analysis

 If the content is stored in the provider-based in-network storage,
 there may be a risk to privacy: a malicious service provider could
 use some link that a victim user is interested in, estimate that
 another user accessing the same data may have the same interest, and
 use this information as a basis to perform a phishing attack on the
 other user.

5.4. Modification of Information

 This type of threat means that some unauthorized entity may alter
 in-transit in-network storage access messages generated on behalf of
 an authorized principal in such a way as to effect unauthorized
 management operations, including falsifying the value of an object.
 This threat may result in false data being supplied either because
 the data on a legitimate store is modified or because a bogus store
 is introduced into the network.

Song, et al. Informational [Page 8] RFC 6646 DECADE Problem Statement July 2012

5.5. Masquerade

 This type of threat means that an unauthorized entity gains access to
 a system or performs a malicious act by illegitimately posing as an
 authorized entity.  In the context of this specification, when
 accessing in-network storage, one malicious end host can masquerade
 as another authorized end host or application server to access a
 protected resource in the in-network storage.

5.6. Disclosure

 This type of threat involves the danger of someone eavesdropping on
 exchanges between in-network storage and application clients.
 Protecting against this threat may be required as a matter of
 application policy.

5.7. Message Stream Modification

 This type of threat means that messages may be maliciously
 re-ordered, delayed, or replayed to an extent greater than what would
 occur in a natural network system, in order to effect unauthorized
 management operations on in-network storage.  If the middlebox (such
 as a Network Address Translator (NAT)) or proxy between an end host
 and in-network storage is compromised, it is easy to do a stream
 modification attack.

6. Acknowledgments

 We would like to thank the following people for contributing to this
 document:
 Ronald Bonica
 David Bryan
 Kar Ann Chew
 Lars Eggert
 Roni Even
 Adrian Farrel
 Yingjie Gu
 David Harrington
 Leif Johansson

Song, et al. Informational [Page 9] RFC 6646 DECADE Problem Statement July 2012

 Francois Le Faucheur
 Hongqiang Liu
 Tao Ma
 Borje Ohlman
 Akbar Rahman
 Peter Saint-Andre
 Robert Sparks
 Sean Turner
 Yu-shun Wang
 Richard Woundy
 Yunfei Zhang

7. Informative References

 [DCIA]     Parker, A., "P2P Media Summit presentation", Distributed
            Computing Industry Association, October 2006,
            <http://www.dcia.info/activities/p2pmsla2006/
            CacheLogic.ppt>.
 [Data_Lockers]
            Yang, Y., "Open Content Distribution using Data Lockers",
            CoXNet Workshop, Beijing, China, November 2010,
            <http:// cs-www.cs.yale.edu/homes/yry/projects/p4p/
            open-data-lockers-nov-2010-coxnet.pdf>.
 [ICNP]     Wu, H., "Challenges and Opportunities of Internet
            Developments in China", ICNP 2007 Keynote Speech,
            October 2007,
            <http://www.ieee-icnp.org/2007/keynote_D.html>.
 [P2P_File_Sharing]
            Casadesus-Masanell, R. and A. Hervas-Drane, "Peer-to-Peer
            File Sharing and the Market for Digital Information
            Goods", Journal of Economics & Management Strategy,
            Vol. 19, No. 2, pp. 333-373, Summer 2010.

Song, et al. Informational [Page 10] RFC 6646 DECADE Problem Statement July 2012

 [RFC5693]  Seedorf, J. and E. Burger, "Application-Layer Traffic
            Optimization (ALTO) Problem Statement", RFC 5693,
            October 2009.
 [RFC6392]  Alimi, R., Ed., Rahman, A., Ed., and Y. Yang, Ed., "A
            Survey of In-Network Storage Systems", RFC 6392,
            October 2011.
 [ipoque_Internet_Study]
            Schulze, H. and K. Mochalski, "Internet Study 2008/2009",
            2009, <http://www.ipoque.com/resources/internet-studies>.
 [ipoque_P2P_Survey]
            "ipoque's 2007 P2P Survey to be presented at Technology
            Review's Emerging Technologies Conference at MIT",
            August 2007, <http://www.ipoque.com/en/news-events/
            press-center/press-releases/2007/
            ipoque%C2%B4s-2007-p2p-survey-to-be-presented-at-
            technology>.

Song, et al. Informational [Page 11] RFC 6646 DECADE Problem Statement July 2012

Authors' Addresses

 Haibin Song
 Huawei
 101 Software Avenue, Yuhua District
 Nanjing, Jiangsu Province  210012
 China
 EMail: haibin.song@huawei.com
 Ning Zong
 Huawei
 101 Software Avenue, Yuhua District
 Nanjing, Jiangsu Province  210012
 China
 EMail: zongning@huawei.com
 Y. Richard Yang
 Yale University
 EMail: yry@cs.yale.edu
 Richard Alimi
 Google
 EMail: ralimi@google.com

Song, et al. Informational [Page 12]

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