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Internet Engineering Task Force                              O. Akonjang
Internet-Draft                                               A. Feldmann
Intended status: Informational                         DT Labs/TU Berlin
Expires: September 3, 2009                                    S. Previdi
                                                                B. Davie
                                                     Cisco Systems, Inc.
                                                               D. Saucez
                                        Universite catholique de Louvain
                                                           March 2, 2009


                          The PROXIDOR Service
                  draft-akonjang-alto-proxidor-00.txt

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Abstract

   Several applications, such as peer-to-peer (P2P), content
   distribution and realtime services rely on selection mechanisms in
   order to select the peer or server from which to request the service.
   Examples of such services are: file sharing, media streaming and
   voice gateways.

   Application-layer selection algorithms do not typically take into
   account network-layer topology information; either that information
   is unavailable to them, or when such information is available (e.g.,
   from BGP Looking Glass servers), it does not include sufficient
   information about the local topology in the neighbourhood of the
   application client(s).  Therefore, most applications today make their
   selection decisions based on performance measurements (combined with
   some amount of random selection) and largely ignore network layer
   routing.  It has been demonstrated that by keeping the traffic local
   (e.g., within the same Autonomous System) both infrastructure
   utilization and application performance may be improved.

   By enhancing selection algorithms through the use of accurate
   network-layer topology, applications may improve performance while
   network operators are also able to reduce the utilization of
   infrastructure resources by application traffic.  At the same time,
   exchange of information between the application and the network
   should not be allowed to compromise confidentiality for either party.
   Detailed routing information owned by the service provider should not
   be made publicly available, while detailed information about the
   application should also not be made known to the service provider.

   This draft introduces a signaling protocol which we call "PROXIDOR".
   The PROXIDOR protocol is a request-response protocol in which a
   PROXIDOR Client (PxC) issues requests to and receives responses from
   a PROXIDOR Server (PxS).  The questions of how a PxC discovers a PxS
   and how a PxS acquires network-layer topology information are beyond
   the scope of this document.















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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Historical Background of this Proposal . . . . . . . . . .  5
   2.  Conventions  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Benefits of the PROXIDOR Service . . . . . . . . . . . . . . .  5
     3.1.  Benefits to End-users  . . . . . . . . . . . . . . . . . .  5
     3.2.  Benefits to the ISP  . . . . . . . . . . . . . . . . . . .  5
   4.  The PROXIDOR Architecture  . . . . . . . . . . . . . . . . . .  5
     4.1.  Definitions and Terminologies  . . . . . . . . . . . . . .  6
     4.2.  Scope  . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     4.3.  Design Goals . . . . . . . . . . . . . . . . . . . . . . .  7
     4.4.  Design Choices . . . . . . . . . . . . . . . . . . . . . .  7
   5.  Entities of the PROXIDOR System  . . . . . . . . . . . . . . .  8
     5.1.  The PROXIDOR Client  . . . . . . . . . . . . . . . . . . .  8
     5.2.  The PROXIDOR Server  . . . . . . . . . . . . . . . . . . .  9
     5.3.  The Ranking System . . . . . . . . . . . . . . . . . . . .  9
   6.  PROXIDOR Messages  . . . . . . . . . . . . . . . . . . . . . . 10
     6.1.  The Query Message  . . . . . . . . . . . . . . . . . . . . 10
     6.2.  The Response Message . . . . . . . . . . . . . . . . . . . 10
   7.  Use Cases  . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     7.1.  The Oracle Use Case  . . . . . . . . . . . . . . . . . . . 11
     7.2.  The Proximity Use Case . . . . . . . . . . . . . . . . . . 12
     7.3.  The IDIPS Use Case . . . . . . . . . . . . . . . . . . . . 13
   8.  Extensibility  . . . . . . . . . . . . . . . . . . . . . . . . 14
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
   10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 15
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 15
     11.2. Informative References . . . . . . . . . . . . . . . . . . 15





















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1.  Introduction

   This draft introduces the concept of a PROXIDOR service (PS).  A
   PROXIDOR Service (PS) aims to deliver to selection algorithms at the
   application layer (or any other consumer of the PROXIDOR service) the
   topological guidance that will allow an improved selection scheme,
   taking into considerations the topology and infrastructure that is
   going to be used for transmitting data from/to a given selected peer,
   host or server.  The protocol defined in this draft aims to be
   generic and exploitable by any application entity requiring such a
   service, no matter its architecture and implementation.

   This draft describes a signaling protocol through which a PROXIDOR
   Client (PxC) requests service from a PROXIDOR Server (PxS).  In the
   current version of the document, the protocol is described only in
   high-level, abstract terms.

   As an example, a peer-to-peer client, once it has obtained from the
   application layer the list of peers through which a given content or
   service can be obtained, requests PROXIDOR services from a PROXIDOR
   server.  The PROXIDOR query is built with the list of candidate
   peers' IP addresses and sent to the PxS.  The PxS replies with the
   original list of IP addresses sorted by preference.

   The definition of "preference" in this context requires some further
   explanation.  By assigning a higher preference to a particular
   address, the PxS indicates to the application that, all things being
   equal, the application should prefer that address to other addresses
   of lower preference.  Exactly what the PxS means by higher
   preference, or how this preference is calculated, is intentionally
   not made explicit.  As an example, preference may be calculated by
   using routing metric distance, with nodes that are a shorter distance
   from the requester being given a higher preference than those that
   are at a greater distance.  Such a calculation could, for example, be
   performed by inspecting network-layer information (IGP, BGP, etc) and
   may also be influenced by policies of the service provider.

   We assume that the service provider cannot force the application to
   adhere to the preferences that the PROXIDOR service provides.
   Therefore, the service provider has an incentive to provide
   information that is useful to the application; otherwise it is likely
   to be ignored.

   Although we use IP addresses in the preceding example, similar
   ranking operations could also be performed on AS numbers, address
   prefixes, etc.  While it is necessary to ensure interoperability
   through the standardization of the signaling protocol, there is no
   immediate need to standardize any algorithm or any computational



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   method that computes ranks or preferences.

1.1.  Historical Background of this Proposal

   The architecture and protocol described in this document arose from
   the merger of three previous pieces of work: the Oracle service [1],
   the ISP-Driven Informed Path Selection (IDIPS) service [5] and the
   Proximity service [6].  The name PROXIDOR, like the proposal itself,
   contains elements of each of these three original work items.

2.  Conventions

   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].

3.  Benefits of the PROXIDOR Service

   The PROXIDOR service offers many benefits to both end-users
   (consumers of the service) and Internet Service Providers (ISPs)
   (providers of the service).

3.1.  Benefits to End-users

   Hosts that use the PROXIDOR service can benefit in multiple ways,
   e.g., they no longer need to infer topology information or measure
   path performance by themselves.  They can take advantage of the
   knowledge of the ISP to avoid bottlenecks and boost performance.

3.2.  Benefits to the ISP

   ISPs also benefit from the PROXIDOR service.  It enables them to
   influence the neighborhood selection process of overlay networks to
   e.g. ensure locality of traffic and also regain the ability to
   efficiently engineer traffic that traverses backbone and transit
   links, thus allowing a better provisioning of the networking
   infrastructure.

4.  The PROXIDOR Architecture

   The PROXIDOR architecture can be defined in terms of its entities,
   the set of messages that are exchanged between these entities and the
   rules governing the exchanges.








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4.1.  Definitions and Terminologies

      Autonomous System (AS):
            A single network or a collection of networks under the same
            administrative control.

      Autonomous System Number (ASN):
            A globally unique number, used to identify an AS and to exchange
            exterior routing information with other (neighboring) ASes.

      PROXIDOR client (PxC):
            An Internet end-host that requests for PROXIDOR services by
            creating and sending queries.

      PROXIDOR server (PxS):
            An Internet system that accepts and processes PROXIDOR queries.

      Metric:
            Criteria used by server to process/rank IP addresses,
            prefixes or ASNs in a query.

      PROXIDOR Query (PxQ):
            A message to request for a particular PROXIDOR service.

      PROXIDOR Response (PxR):
            An answer to a PROXIDOR query.

      PROXIDOR Error (PxE):
            Indicates non-conformity.

      PROXIDOR Failure (PxF):
            A PROXIDOR system malfunction.

      PROXIDOR Services (PS):
            A PROXIDOR service that can be directly requested by clients.

      PROXIDOR Service Protocol (PSP):
            The protocol used by PROXIDOR entities to communicate with
            each oher.

      PROXIDOR Source List (PSL):
            A list of sources that is sent to PxS for ranking.

      PROXIDOR Target List (PTL):
            A list of targets that is sent to PxS for ranking.

      PROXIDOR Couples (PC):
            A ranked list of <source, destination>.



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      PROXIDOR Source Address (PSA):
           Source IP or Prefix address used in PxQ when requesting for
           PROXIDOR services.

      Type Length Value (TLV):
            Data encoding format for PROXIDOR payloads.

4.2.  Scope

   This draft defines the PROXIDOR service, describes its functionality
   and gives details of its architecture.  Details of the PROXIDOR
   protocol itself (i.e., details of the messages that are exchanged
   between entities of the PROXIDOR service) are out of scope of this
   document.

4.3.  Design Goals

   We expect the PROXIDOR service to be requested by a high number of
   simultaneous clients and therefore aspects such as simplicity,
   scalability, performance and flexibility are among the most important
   criteria:

   o  Simplicity.  The protocol must be lightweight in its content and
      state machinery.  Different flavors may be defined in order to
      cope with different application scenarios.  However, in most of
      practical cases, the protocol should carry the minimal set of
      information in its simplest form of encoding.

   o  Scalability.  The protocol is expected to be used by a large
      amount of consumers simultaneously, which means that providers
      will have to absorb a large amount of transactions.  Protocol
      specification should take into account the scalability factors
      that would allow the protocol and its implementations to scale.

   o  Performance.  Related to scalability, PROXIDOR servers will have
      to handle a high number of simultaneous transactions and therefore
      the performance of handling protocol packets is critical for the
      overall scalability and deployability of the protocol.

   o  Flexibility.  The protocol should allow different modes of
      operations with different encoding techniques.

4.4.  Design Choices

   Two major concerns of the PROXIDOR protocol design are scalability
   and performance.  A server (or a cluster of servers) should be able
   to simultaneously handle a very large number of client requests and
   yet, suffer no penalties in terms of performance.  To address these



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   concerns, important design choices need to be made, including;

      i) Choice of transport protocol:

         The PROXIDOR service SHOULD be able to function with UDP, TCP
         and HTTP.

      ii) Choice of approach:

         Although most aspects of the PROXIDOR protocol are new,
         advantage is still taken of already existing protocols, such as
         the Domain Name System (DNS) protocol.  In principle, we see a
         lot of functional similarities between the DNS and the PROXIDOR
         service.  The DNS is not only distributed and very scalable,
         but can also effectively handle many queries from a large
         number of clients simultaneously.  The DNS protocol approach is
         thus partly adopted.

   Further concerns of the protocol design are flexibility and
   extensibility.  The protocol should be flexible enough to adapt to
   changes in end-users' and ISPs' needs and be extensible enough to
   incorporate new types of services without the need to undergo a
   fundamental change.

   To address these concerns, PROXIDOR uses both Service Codes (to
   request for particular PROXIDOR services or to express their
   preferences) and Service Categories (to create and categorize (new)
   PROXIDOR service groups).

5.  Entities of the PROXIDOR System

   A PROXIDOR system consists of PROXIDOR clients and PROXIDOR servers.
   Both entities implement the PROXIDOR protocol in order to interact
   with each other.  Each entity independently plays an important role
   in the overall system architecture.

5.1.  The PROXIDOR Client

   The PROXIDOR client can either be an end-user host that generates and
   sends queries to a PROXIDOR server or a PROXIDOR server that
   generates and/or forwards queries to other PROXIDOR servers.

   To use the PROXIDOR service, a client (PxC) must generate a standard
   PROXIDOR query (PxQ) and send to the PROXIDOR server (PxS).  It can
   also optionally cache a copy of the sent packet.  It MUST clear its
   cache before attempting to contact another PROXIDOR server.





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5.2.  The PROXIDOR Server

   A PROXIDOR server that receives a query, can generally react in one
   of the following ways:

   o  grant the request by responding appropriately to the query,

   o  silently drop the query if it is e.g., running out of resources,

   o  send back a PROXIDOR error message (PxE), in case of a malformed
      request,

   o  send back a PROXIDOR failure message (PxF), in case of system
      malfunction,

   o  send back a re-direct message, re-directing the client to another
      PROXIDOR server, if it doesn't offer the requested service and
      knows another (trusted) server that does.

   The server MAY also decide to explicitly express the criteria it used
   in ranking the contents of the response message.  It should be noted
   that revealing the criteria does not directly reveal the algorithm or
   functions that these criteria were used to construct.

   The PROXIDOR protocol may also be used between servers.  When a
   server needs more accurate information that is not available in its
   database, it may also use the PROXIDOR service to request this
   information from another server.  This could be typical in
   environments such as the global coordinate system in [2].  PROXIDOR
   protocol supports authentication between a client and a server and
   between servers.  Authentication could be used to establish a kind of
   trust between PROXIDOR entities involved in a transaction.

5.3.  The Ranking System

   The most common (perhaps the default) criteria for the ranking system
   is the minimal distance between the requester and each individual IP
   address in the query message.  In this case the PxS evaluates the
   distance between requester and each address of the list and returns
   the list in an ordered fashion.  Distance is evaluated according to
   the network-layer topology.

   A different preference criteria can be specified, relying on AS
   membership: Given an unsorted list of IP addresses, the PxS returns
   the list ordered by preference in AS membership.  The ranked list
   starts with addresses belonging to the same AS of the requester, then
   all other addresses ordered according to the number of AS-hops
   between their AS and requester's AS.



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   The ranking system can also use criteria that are based on measured
   performance, such as available bandwidth and link delays, as well as
   those that are based on the ISP's private policies and need to be
   taken into consideration.

   Criteria MAY be used either alone or in combinations, when evaluating
   preferences.

   While a ranking is one way to assign preferences to addresses,
   prefixes, etc., it may also be desirable to assign a weight to the
   elements in the list, to indicate more clearly the extent to which
   some elements are preferred over others.  This approach is described
   in [4].

   The semantic of each ranking request is carried within the query
   message (implicitly or explicitly).  However, the server MAY or MAY
   NOT take this into account.

6.  PROXIDOR Messages

   There are generally two types of PROXIDOR messages; the PROXIDOR
   query (PxQ) message and the PROXIDOR response (PxR) message.

6.1.  The Query Message

   A standard (default) PROXIDOR query (PxQ) is that which is sent from
   a PROXIDOR client (PxC) to a PROXIDOR server (PxS).  A PROXIDOR
   server (PxS) can also query another PxS using the same message
   format.  The PROXIDOR protocol differentiates between these two query
   types.

   Query messages may also carry requests that express desires for more
   specific information or services.  The server is not compelled to
   grant them.  The server MAY decide to grant or ignore them, depending
   on its own preferences or individual policies.  For example, it can
   decide to grant server-generated desires sent by trusted PxS peers
   and ignore client-generated ones that it considers to be too
   intrusive.

6.2.  The Response Message

   Response messages are similar in structure to query messages.
   Response messages can make use of attributes (optional) to send
   additional information about designated payload types, e.g., when
   responding to queries sent by a trusted PxS peer.  Such peers could
   exist within an AS or in a global coordinate system, made up of
   PROXIDOR servers that are managed by different ISPs.  The additional
   information supplied by the use of attributes can help the receiving



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   server make better decisions before responding to client-generated
   queries.

   The order of the items in the response message is very important.
   The first item indicates highest priority or preference and the last
   one, least priority or preference.  There is no general derivable
   relationship between this order and the criteria used to create it,
   since the latter MAY depend on factors that are of the PROXIDOR
   Service Provider's individual choice.

   Although some characteristics of the response message is also
   determined by the same factors that affect those of the query
   message, all response packets MUST additionally adhere to the
   important factor of strict ranking.  Ranking could force the response
   payload to be packaged in particular orders relative to each other,
   requiring the use of extra bytes in the response message than that
   used in the query.  The details of this aspect is out of scope of
   this document.

7.  Use Cases

   Use cases are grouped according to service categories, such as the
   Oracle service category, the Proximity service category and the IDIPS
   service category.

7.1.  The Oracle Use Case

   i) The PROXIDOR service is used in a P2P environment to influence the
   neighborhood selection process.

      An end-host that wants to join a P2P overlay, first needs to
      locate and cretae a list of potential neighbors.  Instead of
      randomly connecting to clients in the list, the end-host can use
      the PROXIDOR service to establish a more effective connection
      pattern.

      1.  The PROXIDOR client (PxC) creates a PROXIDOR Target List (PTL)
          from the list of potentials neighbors.

      2.  PXC contructs a PROXIDOR query message (PxQ) with the PTL as
          payload.

      3.  PxC then sends PxQ to a PROXIDOR server (PxS) for ranking.

      4.  PxS receives and extracts PTL from PxQ.  It uses its knowledge
          of the network to re-arrange the list, ranking them according
          to some pre-defined criteria, e.g. locality and bandwidth.




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          +  The list is ranked according to priority (or preference),
             i.e., from highest to lowest.

          +  Proximal and optimal performing neighbors (relative to PxC)
             are given highest priority and are placed at the top of the
             list.

          +  PxS can decide to supplement the response with extra
             information through the use of attributes and their values.

      5.  PxS then sends the ranked PTL back to PxC.

      6.  PxC can now use the ranked PTL to establish optimal overlay
          connections.

   ii) The PROXIDOR service is used in a P2P environment to influence
   the selection of sources from where content is downloaded.

      After a successful search or after joining a swarm, PxC may have
      multiple sources from which content could be downloaded.  It can
      use the PROXIDOR service again to locate the best sources (from
      among these potential sources) to download from.

      1.  PxC creates a new PTL from the list of potential sources.

      2.  PxC constructs a new PxQ using the new PTL.

      3.  PxC sends the new PxQ to PxS.

      4.  PxS extracts and ranks the PTL according to optimal
          performance.

      5.  PxS sends the ranked PTL back to PxC.

      6.  PxC can now use the ranked PTL to download from the best
          ranked sources in a more efficient mannner.

7.2.  The Proximity Use Case

   1.  PxC obtains from the application layer the list of servers/peers
       where data or service is available.  PxC builds a list of IP
       addresses corresponding to these peers/servers.

   2.  PxC builds a PROXIDOR query (PxQ).  PxC insert following
       information in the query:

       *  PSA: the PxC IP address.




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       *  PTL: the list of target IP addresses.

       *  PRC: set to IP-Address-based or AS-based.

   3.  PxC sends the PxQ to the PxS.

   4.  PxS receives PxQ and extracts the following information:

       *  PROXIDOR Source Address (PSA).  PSA is the source IP address
          of the requester.

       *  PROXIDOR Target List (PTL).  PTL is the list of IP addresses
          for which PROXIDOR service is requested.

       *  PROXIDOR Ranking Criteria.

   5.  PxS computes PROXIDOR algorithms and ranks the PTL based on PRC.
       Preference is determined according to network-layer topology
       information.

   6.  PxS creates a PxR message including:

       *  PROXIDOR Source Address (PSA): the PSA address as received in
          the request packet.

       *  PROXIDOR Target List (PTL): the ordered (ranked) original PTL
          (as received in the request packet).

       *  PROXIDOR Ranking Criteria: same as PRC in PxR message.

   7.  PxC receives PxR, extracts PTL and may apply it to its selection
       scheme.

7.3.  The IDIPS Use Case

   The PxC is connected to its network with, at the same time, a
   wireless and a wired connection.

   1.  PxC obtains from the application layer the list of servers/peers
       where data or service is available.  PxC builds a list of IP
       addresses corresponding to these peers/servers.

   2.  PxC builds a PROXIDOR query (PxQ).  PxC insert following
       information in the query:

       *  PSL: the list of PxC IP addresses.





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       *  PTL: the list of target IP addresses.

       *  PRC: set to delay-based.

   3.  PxC sends the PxQ to the PxS.

   4.  PxS receives PxQ and extracts the following information:

       *  PROXIDOR Source List (PSL).  PSL is the list of IP addresses
          of the requester.

       *  PROXIDOR Target List (PTL).  PTL is the list of IP addresses
          for which PROXIDOR service is requested.

       *  PROXIDOR Ranking Criteria.

   5.  PxS determines the feasible <source,destination> pairs where
       souces are in PSL and destinations are in PTL.  PxS computes
       PROXIDOR algorithms and ranks the pairs.  Preference is
       determined according to network-layer topology information.

   6.  PxS creates a PxR message including:

       *  PROXIDOR Couples (PC): the ordered (ranked) list of <source,
          destination> pairs built with the original PSL and the
          original PTL.

       *  PROXIDOR Ranking Criteria: same as PRC in PxQ message.

   7.  PxC receives PxQ, extracts PC and may apply it to its selection
       scheme.

8.  Extensibility

   The protocol is capable of using different transport mechanisms and
   also allows both clients and servers to express particular desires.
   These aspects add a great deal of flexibility to the protocol
   construct.

   The use of service categories also creates enough room for
   extensibility when the need for such arises, e.g., when changes in
   end-users' or ISPs' needs necessitate the creation of additional
   service features or even totally new service groups.

9.  Security Considerations

   The PROXIDOR system MUST ensure that data is exchanged between
   PROXIDOR servers in a secure manner.  Details of this aspect and



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   further security considerations will be treated in future versions of
   this document.

10.  Contributors

   We acknowledge with much thanks the enormous contributions made
   through discussions, remarks and suggestions by the following
   individuals (in alphabetical order): Vinay Aggarwal, Olivier
   Bonaventure, Pierre Francois, Benjamin Frank, Luigi Iannone, Jun
   Jiang, Ingmar Poese, Georgios Smaragdakis and Pengchun Xie.

11.  References

11.1.  Normative References

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

11.2.  Informative References

   [1]        Aggarwal, V., Feldmann, A., and C. Scheideler, "Can ISPs
              and P2P systems co-operate for improved performance?", ACM
              SIGCOMM Computer Communications Review (CCR), 37(3):29-40,
              July 2007.

   [2]        Aggarwal, V., Feldmann, A., and R. Karrer, "An Internet
              Coordinate system to enable collaboration between ISPs and
              P2P systems", In Proceedings of the 11th International
              ICIN Conference , October 2007.

   [3]        Aggarwal, V., Akonjang, O., and A. Feldmann, "Improving
              User and ISP Experience through ISP-aided P2P Locality",
              In Proceedings of 11th IEEE Global Internet Symposium 2008
              (GI '08) , 2008.

   [4]        Shalunov, S., Penno, R., and R. Woundy, "ALTO Information
              Export Service", draft-shalunov-alto-infoexport-00 (work
              in progress) , October 2008.

   [5]        Saucez, D., Donnet, B., and O. Bonaventure, "IDIPS: ISP-
              Driven Informed Path Selection",
              draft-saucez-alto-idips-01 (work in progress) ,
              February 2008.

   [6]        Previdi, S., "Routing Proximity Services", IETF 73,
               http://www.ietf.org/proceedings/08nov/slides/alto-0.pdf,
              November 2008.




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Authors' Addresses

   Obi Akonjang
   DT Labs/TU Berlin
   Ernst-Reuter-Platz 7
   10587 Berlin
   Germany

   EMail: obi@net.t-labs.tu-berlin.de


   Anja Feldmann
   DT Labs/TU Berlin
   Ernst-Reuter-Platz 7
   10587 Berlin
   Germany

   EMail: anja@net.t-labs.tu-berlin.de


   Stefano Previdi
   Cisco Systems, Inc.
   Via Del Serafico
   Rome 00142
   Italy

   EMail: sprevidi@cisco.com


   Bruce Davie
   Cisco Systems, Inc.
   1414 Mass. Ave.
   Boxborough, MA  01719
   USA

   EMail: bsd@cisco.com


   Damien Saucez
   Universite catholique de Louvain
   Place Sainte Barbe 2
   Louvain-la-Neuve, 1348
   Belgium

   EMail: damien.saucez@uclouvain.be






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