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ALTO                                                           S. Kiesel
Internet-Draft
Intended status: Standards Track                          M. Stiemerling
Expires: September 2, 2010                               NEC Europe Ltd.
                                                           March 1, 2010


                                ALTO H12
                        draft-kiesel-alto-h12-01

Abstract

   Many Internet applications are used to access resources, such as
   pieces of information or server processes, which are available in
   several equivalent replicas on different hosts.  This includes, but
   is not limited to, peer-to-peer file sharing applications.  The goal
   of Application-Layer Traffic Optimization (ALTO) is to provide
   guidance to applications, which have to select one or several hosts
   from a set of candidates, that are able to provide a desired
   resource.  This memo proposes one possible way of implementing the
   ALTO protocol, called H12.

Status of this Memo

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

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   This Internet-Draft will expire on September 2, 2010.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the



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   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
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   described in the BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Solution Space . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Proposed Solution  . . . . . . . . . . . . . . . . . . . . . .  6
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   5.  Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . .  9
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     6.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     6.2.  Informative References . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11



























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1.  Introduction

   Many Internet applications are used to access resources, such as
   pieces of information or server processes, which are available in
   several equivalent replicas on different hosts.  This includes, but
   is not limited to, peer-to-peer file sharing applications.  The goal
   of Application-Layer Traffic Optimization (ALTO) is to provide
   guidance to applications, which have to select one or several hosts
   from a set of candidates, that are able to provide a desired
   resource.  This memo proposes one possible way of implementing the
   ALTO protocol, called H12.  The H12 protocol is a client/server
   protocol between end hosts and ALTO servers.

   The problem space of ALTO is described in
   [I-D.marocco-alto-problem-statement] and the set of requirements is
   discussed in [I-D.kiesel-alto-reqs].

   Comments and discussions about this protocol proposal should be
   directed to the ALTO working group: alto@ietf.org.
































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2.  Solution Space

   The ALTO protocol is a client/server protocol, operating between a
   number of ALTO clients and an ALTO server, as sketched in Figure 1

                 +----------+
                 |  ALTO    |
                 |  Server  |
                 +----------+
                       ^
                _.-----|------.
            ,-''       |       `--.
          ,'           |           `.
         (     Network |             )
          `.           |           ,'
            `--.       |       _.-'
                `------|-----''
                       v
    +----------+  +----------+   +----------+
    |  ALTO    |  |  ALTO    |...|  ALTO    |
    |  Client  |  |  Client  |   |  Client  |
    +----------+  +----------+   +----------+

                Figure 1: Network Overview of ALTO Protocol

   An ALTO server stores information about preferences (e.g., a list of
   preferred autonomous systems, IP ranges, etc) and ALTO clients can
   retrieve these preferences.  However, there are basically two
   different approaches on where the preferences are actually processed:

   1.  The ALTO server has a list of preferences and clients can
       retrieve this list via the ALTO protocol.  This preference list
       can be partially updated by the server.  The actual processing of
       the data is done on the client and thus there is no data of the
       client's operation revealed to the ALTO server .  This approach
       has been proposed by [I-D.shalunov-alto-infoexport].

   2.  The ALTO server has a list of preferences or preferences
       calculated during runtime and the ALTO client is sending
       information of its operation (e.g., a list of IP addresses) to
       the server.  The server is using this operational information to
       determine its preferences and returns these preferences (e.g., a
       sorted list of the IP addresses) back to the ALTO client.  This
       approach has been initially described in [ACM.ispp2p], but never
       been described on the protocol level.

   Approach 1 (we call it H1) has the advantage (seen from the client)
   that all operational information stays within the client and is not



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   revealed to the provider of the server.  On the other hand, does
   approach 1 require that the provider of the ALTO server, i.e., the
   network operator, reveals information about its network structure
   (e.g., AS numbers, IP ranges, topology information in general) to the
   ALTO client.

   Approach 2 (we call it H2) has the advantage (seen from the operator)
   that all operational information stays with the ALTO server and is
   not revealed to the ALTO client.  On the other hand, does approach 2
   require that the clients send their operational information to the
   server.

   Both approaches have their pros and cons and are extensively
   discussed on the ALTO mailing list.  But there is basically a
   dilemma: Approach 1 is seen as the only working solution by peer-to-
   peer software vendors and approach 2 is seen as the only working by
   the network operators.  But neither the software vendors nor the
   operators seem to willing to change their position.  However, there
   is the need to get both sides on board, to come to a solution.

   Therefore, this does memo proposes to integrate both approaches in
   one protocol and offer a way for clients and servers to learn each
   preferred way of operating.




























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3.  Proposed Solution

   The current proposed solution is not yet defining a bit level syntax
   but describes the protocol on a high-level, i.e., it is not yet a
   complete solution that can be implemented and deployed.

   The H12 protocol uses TCP as transport protocol between clients and
   server and some encoding of the messages to be defined later on.

   Unlike the H1H2 protocol[I-D.stiemerling-alto-h1h2-protocol] the H12
   protocol does not have several modes of operation, which have to be
   negotiated at the startup.  Instead it allows the client and the
   server some flexibility in the requests and the responses while using
   only on mode of operation.

   The client puts one or several host location attributes, about which
   it wants to receive a rating, in the query message.  We proposes, as
   example and not to predetermine the final encoding scheme, that the
   client uses the TLV defined in Figure 2.

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Type         | Length                        |    Reserved   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                  IPv4 or IPv6 address                       //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  PrefixLength |                      Reserved                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                 Figure 2: TLV for IP addresses and ranges

   The Type and Length fields are tbd.  The IPv4 or IPv6 address field
   carries the actual address or address prefix (actually there might be
   two different TLVs for each IP version).  The PrefixLength field
   carries the length of the prefix (e.g., 32 for a full IPv4 address).

   This TLV carries a full IP address or an IP address prefix, leaving
   the client the choice how much of an IP address it wants to reveal to
   the server.  That is, the client can request information for one or
   several specific IP addresses (PrefixLength equal 32 or 128), for
   address ranges, or for "the whole Internet" (PrefixLength equal 0).
   However, the "whole Internet" is not really referring to the whole
   Internet as such, as no single entity can have such a big knowledge,
   but to whatever broader scope the server can give guidance about.
   This scop can include, for instance, its own complete network.




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   Furthermore, the client specifies one or several rating criteria,
   such as operator preference, lower bound for delay, etc.  For a work-
   in-progress list of such rating criteria see [I-D.kiesel-alto-reqs].

   The server replies with a list of network location attributes, in the
   same format as in the query, and the respective ratings for the
   requested attributes.  However, the number of lines in this list may
   be shorter or longer than in the query, and the PrefixLengths may be
   different:

   o  The server may decide not to give any rating for a specific
      location attribute.  In this case, a default value applies.

   o  Instead of rating several location attributes with long
      PrefixLengths (in particular: individual IP addresses)
      individually, the server may decide to give only one rating for a
      broader address range (i.e., PrefixLength is shorter).

   o  Instead of giving one rating for a large address range, the server
      may decide to give several ratings for smaller ranges (i.e., i.e.,
      each returned TLV has a PrefixLength that is longer that
      requested).

   The actual rating is given for each rating criterion as a signed
   integer value.  A value of zero (0) means "default value".  This
   value is to be used if the server has no information regarding this
   (network location attribute, rating criteria) tuple, or if it does
   not want to disclose it.  Positive values mean that this location is
   "better" than default and therefore should be preferred for peer
   selection, while negative values indicate the location to be "worse"
   than default and therefore that it should be avoided.  The meaning of
   "better" and "worse", as well as the scale has to be defined
   individually for each rating criterion.

   This approach gives both sides, i.e., server and clients, to still
   exchange their desired information and level of precision, but also
   gives the chance to hide information if necessary and desired.














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4.  Security Considerations

   This initial version of this memo does not yet have any security
   considerations, but they will be added in future revision.















































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5.  Conclusion

   This memo presents a very basic straw man protocol, is for sure work
   in progress, and is requesting feedback from the ALTO working group.
   Ask the authors why it is called H12.














































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6.  References

6.1.  Normative References

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

6.2.  Informative References

   [ACM.ispp2p]
              Aggarwal, V., Feldmann, A., and C. Scheideler, "Can ISPs
              and P2P systems co-operate for improved performance?",  In
              ACM SIGCOMM Computer Communications Review
              (CCR), 37:3, pp. 29-40.

   [I-D.kiesel-alto-reqs]
              Kiesel, S., Popkin, L., Previdi, S., Woundy, R., and Y.
              Yang, "Application-Layer Traffic Optimization (ALTO)
              Requirements", draft-kiesel-alto-reqs-02 (work in
              progress), March 2009.

   [I-D.marocco-alto-problem-statement]
              Seedorf, J. and E. Burger, "Application-Layer Traffic
              Optimization (ALTO) Problem Statement",
              draft-marocco-alto-problem-statement-05 (work in
              progress), March 2009.

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

   [I-D.stiemerling-alto-h1h2-protocol]
              Stiemerling, M. and S. Kiesel, "ALTO H1/H2 Protocol",
              draft-stiemerling-alto-h1h2-protocol-00 (work in
              progress), March 2009.















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Authors' Addresses

   Sebastian Kiesel

   Email: ietf-alto@skiesel.de


   Martin Stiemerling
   NEC Laboratories Europe/University of Goettingen
   Kurfuerstenanlage 36
   Heidelberg  69115
   Germany

   Phone: +49 6221 4342 113
   Fax:   +49 6221 4342 155
   Email: stiemerling@nw.neclab.eu
   URI:   http://www.nw.neclab.eu/


































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