Internet DRAFT - draft-song-decade-problem-statement

draft-song-decade-problem-statement






DECADE                                                           H. Song
Internet-Draft                                                   N. Zong
Intended status: Standards Track                                  Huawei
Expires: January 12, 2011                                        Y. Yang
                                                                R. Alimi
                                                         Yale University
                                                           July 11, 2010


     DECoupled Application Data Enroute (DECADE) Problem Statement
                 draft-song-decade-problem-statement-02

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 total
   amount of P2P traffic is to introduce storage capabilities within the
   network.  Traditional caches (e.g., P2P and Web caches) provide such
   storage, but they are complex (due to explicitly supporting
   individual P2P application protocols) and they do not allow users to
   manage access to content in the cache.  For example, Content
   Providers cannot easily control access and resource usage policies to
   satisfy their own requirements.  This document discusses the
   introduction of in-network storage for P2P applications, shows the
   need for a standard protocol for accessing this storage, and
   identifies the scope of this protocol.  The accessing protocol can
   also be used by other applications with similar requirements.

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on January 12, 2011.

Copyright Notice




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   Copyright (c) 2010 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
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   (http://trustee.ietf.org/license-info) in effect on the date of
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   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology and Concepts . . . . . . . . . . . . . . . . . . .  4
   3.  The Problems . . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.1.  P2P infrastructural stress and inefficiency  . . . . . . .  5
     3.2.  P2P cache: a complex in-network storage  . . . . . . . . .  5
     3.3.  Ineffective integration of P2P applications and
           in-network storage . . . . . . . . . . . . . . . . . . . .  6
   4.  DECADE as an In-network Storage Capability . . . . . . . . . .  7
     4.1.  Data access  . . . . . . . . . . . . . . . . . . . . . . .  9
     4.2.  Authorization  . . . . . . . . . . . . . . . . . . . . . . 10
     4.3.  Resource control . . . . . . . . . . . . . . . . . . . . . 10
   5.  Usage Scenarios  . . . . . . . . . . . . . . . . . . . . . . . 10
     5.1.  BitTorrent . . . . . . . . . . . . . . . . . . . . . . . . 10
     5.2.  Content Publisher  . . . . . . . . . . . . . . . . . . . . 11
     5.3.  Data Transfer Scenarios  . . . . . . . . . . . . . . . . . 12
       5.3.1.  Both Sender and Receiver Accounts are Used . . . . . . 12
       5.3.2.  Only Sender's Storage Account is Used  . . . . . . . . 13
       5.3.3.  Only Receiver's Storage Account is Used  . . . . . . . 13
       5.3.4.  No Storage Accounts are Used . . . . . . . . . . . . . 13
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
     6.1.  Denial of Service attack . . . . . . . . . . . . . . . . . 14
     6.2.  Copyright and Legal issues . . . . . . . . . . . . . . . . 14
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 14
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 14
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 15
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16







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1.  Introduction

   P2P applications, including both P2P streaming and P2P filesharing
   applications, make up a large fraction of the traffic in many
   Internet networks today.  One way to reduce bandwidth usage by P2P
   applications is to introduce storage capabilities in the networks.
   Allowing P2P applications to store and retrieve data from inside
   networks can reduce traffic on the last-mile uplink, as well as
   backbone and transit links [I-D.weaver-alto-edge-caches].

   P2P caches provide in-network storage and have been deployed in some
   networks.  But 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 applications, closed P2P caching systems
   limit P2P applications to effectively utilize in-network storage.  In
   particular, P2P caches typically do not allow users to explicitly
   store content into in-network storage.  Neither do they allow users
   to implement control over the content that have been placed into the
   in-network storage.

   Both of these challenges can be effectively addressed by using an
   open, standard protocol to access in-network storage.  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.

   With DECADE, P2P applications can still use their native protocols
   for signaling and data transport.  However, they may use a standard
   protocol for data access incorporating in-network storage, and fall
   back to their native data transport protocols if in-network storage
   is not available or not used.

   In essence, an open, standard protocol to access in-network storage
   provides an alternative mechanism for P2P application data access
   that is decoupled from P2P application control and signaling.  This
   decoupling leads to many advantages, which is explained further in
   Section 4.



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2.  Terminology and Concepts

   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 [RFC2119].

   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.

      IAP (In-network storage Access Protocol): a standard protocol that
      is spoken between P2P applications and in-network storage.  The
      protocol may also be used between entities implementing the in-
      network storage service.  IAP may be a new protocol or existing
      protocol with extensions.

      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.

      Content Publisher: An entity that originates content to consumers.


3.  The Problems

   The emergence of peer-to-peer (P2P) as a major type of network
   applications (esp.  P2P file sharing and streaming apps) has led to
   substantial opportunities.  The P2P paradigm can be utilized in
   designing highly scalable and robust applications at low cost,
   compared with traditional client-server paradigms.  For example, CNN
   [CNN] reported that P2P streaming by Octoshape played a major role in
   its distribution of the historical inauguration address of President
   Obama.  PPLive, one of the largest P2P streaming vendors, is able to
   distribute large-scale, live streaming programs to more than 2
   million users with only a handful of servers.

   However, P2P applications also face substantial design challenges.  A
   particular problem facing P2P applications is the substantial stress
   that they place on the network infrastructure.  Also, lacking of
   infrastructure support can lead to unstable P2P application
   performance during peer churns and flash crowd.  Below we elaborate
   on the problems in more detail.



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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 Internet service
   providers (ISP).  Multiple measurements (e.g., [ipoque]) have shown
   that P2P traffic has become a major type of traffic on some networks.
   Furthermore, network-agnostic peering leads to unnecessary traversal
   across network domains or spanning the backbone of a network, leading
   to network inefficiency [I-D.ietf-alto-problem-statement].

   Recently, the IETF Application Layer Traffic Optimization (ALTO)
   Working Group was formed to provide P2P applications with network
   information so that they can perform better-than-random initial peer
   selection [I-D.ietf-alto-problem-statement].  However, there are
   limitations on what ALTO can achieve alone.  For example, network
   information alone cannot reduce P2P traffic in access networks, as
   the total access upload traffic is equal to the total access download
   traffic in a pure P2P system.  On the other hand, it is reported that
   P2P traffic is becoming the dominating traffic on the access networks
   of some networks, reaching as high as 50-60% at the down-links and
   60-90% at the uplinks ([DCIA], [ICNP], [ipoque.P2P_survey.],
   [P2P_file_sharing]).  Consequently, it becomes increasingly important
   to complement the ALTO effort and reduce upload access traffic, in
   addition to cross-domain and backbone traffic.

   The IETF Low Extra Delay Background Transport (LEDBAT) Working Group
   is focusing on techniques that allow large amounts of data to be
   consistently transmitted without substantially affecting the delays
   experienced by other users and applications.  It is expected that
   some P2P applications would start using such techniques, thereby
   somewhat alleviating the perceivable impact (at least on other
   applications) of their high volume traffic .  However, such
   techniques may not be adopted by all P2P applications.  Also, when
   adopted, these techniques do not remove all inefficiencies, such as
   those associated with traffic being 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 potential (relatively) slow upstream
   transmission.  Similarly, the performance of real-time P2P
   applications may be affected by potential (relatively) higher
   upstream latencies.

3.2.  P2P cache: a complex in-network storage

   An effective technique to reduce P2P infrastructural stress and
   inefficiency is to introduce in-network storage.  For example, in
   [I-D.weaver-alto-edge-caches], the author demonstrates clearly the
   potential benefits of introducing in-network storage to improve



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   network efficiency and thus reduce network infrastructure stress.

   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.

   Furthermore, a specific P2P application protocol may be evolving
   continuously, to add new features or fix bugs.  This forces a P2P
   cache vendor to continuously update to track the changes of the P2P
   application, leading to product complexity, high cost, and low
   reliability.

   Third, many P2P applications use proprietary protocols or support
   end-to-end encryption.  This can render P2P caches ineffective.

3.3.  Ineffective integration of P2P applications and in-network storage

   As P2P applications evolve, it becomes increasingly clear that they
   will need in-network resources to provide positive user experiences.
   For example, multiple P2P streaming systems seek additional in-
   network resources during 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.

   A requirement by some P2P applications in using in-network
   infrastructural resources, however, is 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 their specific algorithms in selecting the
   peers that behave as the more stable, higher bandwidth sources.  They
   continue to fine-tune such algorithms.  In other words, in-network
   storage should export basic mechanisms and allow as much flexibility
   as possible to P2P applications to implement specific policies.  This
   conforms to the end-to-end systems principle and allows innovation
   and satisfaction of specific business goals.  Existing techniques for



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   P2P application in-network storage lack these capabilities.


4.  DECADE as an In-network Storage Capability

   The objective of this working group is to design DECADE, an in-
   network storage protocol to address the problems discussed in the
   preceding section.

   DECADE will provide access to storage and data transport services in
   the network to P2P applications to improve their efficiency and
   reduce the stress on the network infrastructure.  Unlike the existing
   P2P caching architecture, DECADE is a standard interface for various
   P2P applications (both content publishers and end users) to access
   in-network storage.  This decoupling of P2P data access from P2P
   application control and signaling reduces the complexity of in-
   network storage services.  Furthermore, DECADE provides basic access
   mechanisms and allows P2P applications to implement flexible policies
   to create an ecosystem for application innovation and various
   business goals.  Besides that, it also improves the availability of
   P2P contents because the in-network storage is always-on.

                            IAP
                        -----------+
                        |          |
                        |          v
                   +--------------------+
                   | In-network Storage |
                   +--------------------+
                     ^               ^
                 IAP |           IAP |
       +-------------v-+           +-v-------------+
       | P2P           |           |  Content      |
       | application   |           |  publishers   |
       | clients       |           +---------------+
       +---------------+
        |             ^
        |             |
        +-------------+
        P2P application
        native protocol

   Figure 1  Overview of protocol interaction between DECADE elements

   Specifically, the main component of DECADE is the in-network storage
   access protocol (IAP), which is a standard, P2P-application-agnostic
   protocol for different P2P applications to access in-network storage.
   IAP defines a set of commands that P2P application elements can issue



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   to in-network storage to store and retrieve data.  IAP includes the
   following functionalities:

   (1) Data access provides read/write by users (e.g., P2P application
   clients and content publishers) to the corresponding in-network
   storage and between entities implementing the in-network storage;

   (2) Authorization implements access control to resources provided by
   in-network storage;

   (3) Resource control allows users to implement application policies
   for the corresponding in-network storage.

   Note that DECADE is independent of current IETF work on P2P, e.g.
   P2PSIP, ALTO, PPSP.  For example, peers discovered by either RELOAD
   or ALTO can all use DECADE to share data.

   The Peer to Peer Streaming Protocol effort in the IETF is
   investigating specification of signaling protocols (called PPSP
   protocols) for multiple types of entities (e.g. intelligent
   endpoints, caches, content distribution network nodes, and/or other
   edge devices) to participate in P2P streaming systems in both fixed
   and mobile Internet.  As discussed in the PPSP problem statement
   document [I-D.zhang-ppsp-problem-statement], one important PPSP use
   case is the support of an in-network edge Cache for P2P Streaming.
   However, this approach to providing in-network cache has different
   applicability, different objectives and different implications for
   the in-network cache operator.  A DECADE service can be used for any
   application transparently to the DECADE in-network storage operator:
   it can be used for any P2P Streaming application (whether it supports
   PPSP protocols or not), for any other P2P application, and for non
   P2P applications that simply want to benefit from in-network storage.
   So with DECADE the operator is providing a generic in-network storage
   service that can be used by any application without application
   involvement or awareness by the operator; in the PPSP cache use case,
   the cache operator is participating in the specific P2P streaming
   service.

   DECADE and PPSP can both contribute independently, and (where
   appropriate) simultaneously, to making content available closer to
   peers.  Here are a number of example scenarios:

      A given network supports DECADE in-network storage, and its CDN
      nodes do not participate as PPSP Peers for a given "stream" (e.g.
      say because no CDN arrangement has been put in place between the
      Content Provider and the considered network provider).  In that
      case, PPSP Peers will all be "off-net" but will be able to use
      DECADE in-network storage to exchange chunks.



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      A given network does not support DECADE in-network storage, and
      (some of) its CDN nodes participate as PPSP Peers for a given
      "stream" (e.g. say because an arrangement has been put in place
      between the Content Provider and the considered network provider).
      In that case, the CDN nodes will participate as in-network PPSP
      Peers.  The off-net PPSP Peers (ie end users) will be able to get
      chunks from the in-network CDN nodes (using PPSP protocols with
      the CDN nodes).

      A given network supports DECADE in-network storage, and (some of)
      its CDN nodes participate as PPSP Peers for a given "stream" (e.g.
      say because an arrangement has been put in place between the
      Content Provider and the considered network provider).  In that
      case, the CDN nodes will participate as in-network PPSP Peers.
      The off-net PPSP Peers (ie end users) will be able to get chunks
      from the in-network CDN nodes (using PPSP protocols with the CDN
      nodes) as well as be able to get chunks /share chunks using DECADE
      in-network storage populated (using IAP protocol) by PPSP Peers
      (both off-net end-users and in-network CDN Nodes).

   While DECADE will focus on P2P applications, the solution is expected
   to be applicable in other contexts with similar requirements.

4.1.  Data access

   P2P application clients use the protocol to read data from an in-
   network storage, store data to an in-network storage, or remove data
   from an in-network storage.  The data could be of various types.
   Existing protocols will be used wherever possible and appropriate to
   support DECADE's requirements.  In particular, data storage,
   retrieval, and management may be provided by an existing IETF
   protocols.  The WG will not limit itself to a single data transport
   protocol since different protocols may have varying implementation
   costs and performance tradeoffs.  However, to keep interoperability
   manageable, a small number of specific, targeted, data transport
   protocols will be identified and used.  If a protocol is found to be
   suitable but does not fully meet the requirements, then the protocol
   may need to be extended.  The following considerations should be
   taken into account.  But it might be a trade-off when making
   decision.

      o The protocol(s) should support deployments with a very large
      number of users without substantial increase to operational
      complexity for the storage provider.

      o The protocol(s) should be easy for applications to integrate
      with when they want to use it for P2P applications (e.g. file-
      sharing or streaming) or other content distribution applications.



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4.2.  Authorization

   DECADE ensures that access to the in-network storage is subject to
   authorization by the user owning the in-network storage service.  The
   authorization can take into account the user trying to access, the
   content, the time period, etc.

4.3.  Resource control

   A user uses the protocol to manage the resources on in-network
   storage that can be used by other peers, e.g., the bandwidth or
   connections.  The resource control policies could be based on
   individual remote peers or a whole application.


5.  Usage Scenarios

   Usage scenarios are described from two perspectives.  First, we
   introduce high-level use cases showing how P2P applications may
   utilize in-network storage.  Second, we show how in more detail how
   users exchange data using IAP.

5.1.  BitTorrent

   BitTorrent may be integrated with DECADE to be more network efficient
   and reduce the bandwidth consumed on ISP networks.  When a BitTorrent
   client uploads a block to peers, the block traverses the last-mile
   uplink once for each peer.  With DECADE, 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.

   We now describe in more detail how BitTorrent can utilize DECADE.
   For illustration, we assume that both the BitTorrent client (A) and
   its peer (B) utilize in-network storage.  When A requests a block, it
   indicates that it would like the block stored in its in-network
   storage and provides the necessary access control.  Instead of
   sending the 'piece' message with the desired block, peer B replies
   with a 'redirect' message indicating that the content should be
   retrieved from its own in-network storage and provides the necessary
   access control.  If the peer B had not previously stored the content
   in its in-network storage, it uploads the block.  A downloads the
   block into its own in-network storage from B's in-network storage,
   and finally A itself retrieves the block.

   Note that this requires extensions to the BitTorrent protocol.  While
   there are multiple ways to do so, this example assumes the native
   BitTorrent 'request' message is extended to carry additional



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   information and that a new 'redirect' message is added.  Upload and
   download to/from in-network storage uses the standard IAP protocol.

   This example has illustrated how utilizing DECADE can increase
   BitTorrent's network efficiency.  First, notice that peer B does not
   utilize any uplink bandwidth if the block was already present in its
   in-network storage.  Second, notice that the block is downloaded
   directly into A's in-network storage.  When A wishes to share the
   block with another peer (say, peer C) that supports DECADE, it may
   upload directly from its in-network storage, again avoiding usage of
   the last-mile uplink.

   This technique can be applied to other P2P applications as well.
   Since P2P applications use a standard for communicating with in-
   network storage, they no longer require in-network storage to
   explicitly support their protocol.  P2P applications retain the
   ability to explicitly manage which content is placed in in-network
   storage, as well as access and resource control polices.

5.2.  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 the P2P
   peers.

   Consider a case where the Content Publisher owns an in-network
   storage account within ISP A. If there are multiple P2P peers within
   ISP A, the Content Publisher may utilize DECADE to distribute content
   to the peers.

   First, the Content Publisher stores a block in the in-network
   storage, and then sends to each peer in ISP A the block's identifier
   and necessary access control.  Second, each peer may then download
   from the Content Publisher's in-network storage.

   In this example, the block is distributed in a more network efficient
   way (the content only traverses the ISP's interdomain link once),
   while the Content Publisher retains explicit control over access to
   the content placed in its own storage.  The Content Publisher can
   remove content from its in-network storage when it is stale or needs
   to be replaced, and grant access and resources to only the desired
   peers.

   Note that Content Publishers and individual peers can each use in-
   network storage.  For example, after downloading content from the
   Content Publisher's in-network storage, peers may each utilize their



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   own in-networks storage similar to the usage scenario in Section 5.1.
   This can have the benefit of increased network efficiency, while
   Content Publishers and peers still retain control over content placed
   in their own in-network storage.

5.3.  Data Transfer Scenarios

   The previous usage scenarios have utilized the ability for peers to
   transfer data by storing and retrieving from in-network storage.
   This section describes in further detail an example solution of how
   DECADE can provide this capability.

   In this section, we consider the case of a user B (the receiver)
   requesting data from user A (the sender).  We use Sa to denote User
   A's storage account, and Sb to denote User B's storage account.  Each
   user independently decides if its in-network storage account is used,
   so there are four cases.

   When a user indicates that it wishes to use its in-network storage,
   it provides an access control token the other user.  The token is
   sent using the application's protocol.  To simplify the illustration,
   we omit details of the access control from the detailed scenarios
   below.

5.3.1.  Both Sender and Receiver Accounts are Used

   This scenario is illustrated in Figure 2.  B first requests an object
   from A using the application protocol indicating it wishes the object
   to be stored in Sb.  A responds using the application protocol
   indicating that B should download the object from Sa.  B sends a IAP
   request to Sb indicating that the object should be downloaded from
   Sa.  Sb uses IAP to download from Sa, and finally, B downloads the
   object from Sb (also using IAP).

         +-------+ 4  IAP Get +-------+
         |  Sa   | <----------+  Sb   |
         +-------+  *********>+-------+
               5 data transfer  ^  *
                       3 IAP Get \  * 6 data transfer
                1 App request     \ \ /
      +-------+<-------------------+-------+
      |User A |                    |User B |
      +-------+------------------->+-------+
                2 App response

   Figure 2: Usage Scenario 1 (Sender and receiver Accounts used)





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5.3.2.  Only Sender's Storage Account is Used

   This scenario is illustrated in Figure 3.  B requests an object from
   A using the application protocol.  A responds using the application
   protocol indicating that B should download the object from Sa.
   Finally, B sends a IAP request to Sa to download the object.

                              +-------+
                              |  Sa   |
                              +-------+
                                ^  *
                       3 IAP Get  \  * 4 data transfer
                 1 App request     \ \/
       +-------+<-------------------+-------+
       |User A |                    |User B |
       +-------+------------------->+-------+
                 2 App response

   Firgure 3: Usage Scenario 2 (Sender account used)

5.3.3.  Only Receiver's Storage Account is Used

   This scenario is illustrated in Figure 4.  B requests an object from
   A using the application protocol indicating that it wishes the object
   to be stored in Sb.  A stores the object in Sb (using IAP), and
   responds to B (using the application protocol) that it should
   download from Sb.  B uses IAP to download the object from Sb.
                        +---------+
                      > |   Sb    |
            3.       /  +---------+
         IAP Store /            ^  *
                 /    3.IAP Get   \  * 4 data transfer
               / 1.App request     \  \/
       +-------+<-------------------+-------+
       |User A |                    |User B |
       +-------+------------------->+-------+
                 2.App response

   Figure 4: Usage Scenario 3 (Receiver account used)

5.3.4.  No Storage Accounts are Used

   This scenario is illustrated in Figure 5.  In this scenario, the
   application protocol is used directly to send data.  This scenario
   applies with one of the peers does not support IAP, or neither of the
   peers are using in-network storage.





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                  1.App request
        +-------+<-------------------+-------+
        |User A |   ...   ...   ...  |User B |
        +-------+*******************>+-------+
                  2.data transfer

   Figure 5: Usage Scenario 4 ( No storage accounts used)


6.  Security Considerations

   There are multiple security considerations.  We focus on two in this
   section.

6.1.  Denial of Service attack

   Without access control or resource control, an attacker can try to
   consume a large portion of the in-network storage, or exhaust the
   connections of the in-network storage to commit a Denial of Service
   (DoS) attack.  Thus, access control and resource control mechanisms
   are mandatory.  A resource control mechanism should be used to allow
   a user to allocate the resource in its in-network storage account to
   be utilized by other clients.

6.2.  Copyright and Legal issues

   Copyright and other laws may prevent the distribution of certain
   content in various localities.  While in-network storage operators
   may adopt system-wide ingress or egress filters to implement
   necessary policies for storing or retrieving content, the
   specification and implementation of such policies (e.g., filtering
   and DRM) is outside of the scope of this working group.


7.  IANA Considerations

   There is no IANA consideration with this document.


8.  Acknowledgments

   We would like to thank the following people for contributing to this
   document:

   David Bryan

   Francois Le Faucheur




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   Hongqiang Law.

   Kar Ann Chew

   Richard Woundy

   Roni Even

   Yunfei Zhang

   Yu-shun Wang

   Yingjie Gu


9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

9.2.  Informative References

   [ipoque.com]
              "http://www.ipoque.com/resources/internet-studies/
              internet-study-2008_2009".

   [I-D.ietf-alto-problem-statement]
              Seedorf, J. and E. Burger, "Application-Layer Traffic
              Optimization (ALTO) Problem Statement",
              draft-ietf-alto-problem-statement-04 (work in progress),
              September 2009.

   [I-D.weaver-alto-edge-caches]
              Weaver, N., "Peer to Peer Localization Services and Edge
              Caches", draft-weaver-alto-edge-caches-00 (work in
              progress), March 2009.

   [I-D.zhang-ppsp-problem-statement]
              Zhang, Y., Zong, N., Camarillo, G., Seng, J., and Y. Yang,
              "Problem Statement of P2P Streaming Protocol (PPSP)",
              draft-zhang-ppsp-problem-statement-06 (work in progress),
              July 2010.

   [RFC3720]  Satran, J., Meth, K., Sapuntzakis, C., Chadalapaka, M.,
              and E. Zeidner, "Internet Small Computer Systems Interface
              (iSCSI)", RFC 3720, April 2004.



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   [RFC5661]  Shepler, S., Eisler, M., and D. Noveck, "Network File
              System (NFS) Version 4 Minor Version 1 Protocol",
              RFC 5661, January 2010.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [DCIA]     http://www.dcia.info, "Distributed Computing Industry
              Association".

   [ipoque.P2P_survey.]
              "Emerging Technologies Conference at MIT", Sept. 2007.

   [P2P_file_sharing]
              Parker, A., "The true picture of peer-to-peer
              filesharing", July 2004.

   [ICNP]     Wu, H., "Challenges and opportunities of Internet
              developments in China, ICNP 2007 Keynote", Oct. 2007.


Authors' Addresses

   Song Haibin
   Huawei
   Baixia Road No. 91
   Nanjing, Jiangsu Province  210001
   P.R.China

   Phone: +86-25-56622975
   Email: melodysong@huawei.com


   Ning Zong
   Huawei
   Baixia Road No. 91
   Nanjing, Jiangsu Province  210001
   P.R.China

   Phone: +86-25-56622975
   Email: zongning@huawei.com









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   Y. Richard Yang
   Yale University

   Email: yry@cs.yale.edu


   Richard Alimi
   Yale University

   Email: richard.alimi@yale.edu









































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