path: root/draft-gsenger-anycast-relay-00.txt

Network Working Group                                         O. Gsenger
Internet-Draft                                                March 2007
Expires: September 2, 2007


                        Anycast stream relaying
                     draft-gsenger-anycast-relay-00

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   Copyright (C) The IETF Trust (2007).















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Abstract

   The anycast tunneling (anytun) protocol defines a protocol used for
   communication between unicast clients and anycast servers.  It can be
   used for tunneling information between 2 clients over the servers or
   in relay mode to transmit data form the client over the servers to a
   third party not using the protocol and vice versa.












































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1.  Introduction

   anytun defines a Host Anycast Service as defined in rfc1546.  It can
   be used to build high scalable and redundant tunnel services.  It
   supports both UDP and TCP connections.  Additionally to the
   possibility of establashing an unicast TCP connection over an anycast
   address as suggested in rfc1546, it supports real anycast TCP
   connections with state syncronisation and heuristic state forecast.
   It also has a relay mode, that makes it possible, that only one of
   the connection endpoints has to use the anytun protocol.  This can be
   used to make connections through Firewalls or behind a NAT Router

   RFC3068 [1] DTD.






































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2.  Operation modes

2.1.  Tunnel modes

2.1.1.  Tunneling Mode

   An example of anytun used in tunnel mode

             -----------                      -----------
             |   RTP   |      ----------      |   RTP   |
             -----------  ->  |server 1|  ->  -----------
             |   UDP   |      ----------      |   UDP   |
             -----------                      -----------
   -----     |   IPv6  |      ----------      |   IPv6  |     -----
   |   |  -> -----------  ->  |server 2|  ->  -----------  -> |   |
   -----     |  anytun |      ----------      |  anytun |     -----
   #####     -----------                      -----------     #####
             |   UDP   |      ----------      |   UDP   |
   client 1  -----------  ->  |server 3|  ->  -----------     client 2
             |   IPv4  |      ----------      |   IPv4  |
             -----------                      -----------
             |   ...   |       anycast        |   ...   |

                                 Figure 1

   In tunneling mode the payload of the anytun packet is transmitted
   from one unicast host to the anycast server.  This server makes a
   routing descision based on the underlying protocol and transmits a
   new anytun package to one or more clients depending on the routing
   descition.  The server MAY also route the packet to a directly
   connected network or a service running on the server, but please
   note, that this is only usefull for anycast host services like DNS
   and that the services HAVE TO be running on all servers in order to
   work.

















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2.1.2.  Open tunnel mode

   An example of anytun used in open tunnel mode

             -----------
             |   RTP   |      ----------
             -----------  ->  |server 1|  ->
             |   UDP   |      ----------      -----------
             -----------                      |   RTP   |
   -----     |   IPv6  |      ----------      -----------     -----
   |   |  -> -----------  ->  |server 2|  ->  |   UDP*  |  -> |   |
   -----     |  anytun |      ----------      -----------     -----
   #####     -----------                      |   IPv6* |     #####
             |   UDP   |      ----------      -----------
   client 1  -----------  ->  |server 3|  ->  |   ...   |    host
             |   IPv4  |      ----------                     not using
             -----------                                     anytun
             |   ...   |       anycast
                                              *changed source address
                                               or port

                                 Figure 2

   In open tunnel mode only one of two clients talking to each other
   over the servers MUST use the anytun protocol.  When a client using
   the anytun protocol wants to tunnel data, it is building a connection
   to the anycast servers using the anytun protocol.  The anycast
   servers relay the encapsulated packages directly to the destination
   without using the anytun protocol.  The source address of the
   datagramm HAS TO be changed to the anycast address of the server.
   The anytun servers act like a source NAT router, therefor for the
   destination it saems that it is talking to the client directly.



















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2.1.3.  relay mode

   An example of anytun used in relay mode

             -----------
   -----     |   RTP   |      ----------
   |   |  -> -----------  ->  |server 1|  ->
   -----     |   UDP** |      ----------      -----------
   #####     -----------                      |   RTP   |
             |   IPv6**|      ----------      -----------     -----
   host      -----------  ->  |server 2|  ->  |   UDP*  |  -> |   |
   not using |   ...   |      ----------      -----------     -----
   anytun                                     |   IPv6* |     #####
                              ----------      -----------
             -----------  ->  |server 3|      |   ...   |    host
   -----     |  anytun |      ----------                     not using
   |   |  -> -----------                                     anytun
   -----     |   IPv4  |       anycast
   #####     -----------
   connection|   ...   |
   controller

    *changed source address or port
    **changed destination address or port

                                 Figure 3

   In relay mode the anycast serveres directly repaet the packetes of
   clients, only the source and destination addresses are changed.  The
   anytun protocol is only used for controll messages, but not fr
   encapsulation.

2.2.  Transport modes

2.2.1.  anycast udp mode

2.2.2.  unicast tcp with anycast initialisation

2.2.3.  full anycast tcp

2.2.3.1.  keep alive message request

   Most NAT routers need a tcp connection to transmit some packets once
   in while to stay open.  In full anycast tcp mode anytun hast to
   predict the tcp state including the sequence number.  Synconisation
   of the sequence number would be to much overhead, so a keep alive
   intervall is agreed.  This interval is used to calculate the sequemce
   number.



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3.  Protocol specification

3.1.  Header format
















































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Appendix A.  The appan


















































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4.  References

   [1]  Huitema, C., "An Anycast Prefix for 6to4 Relay Routers",
        RFC 3068, June 2001.















































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Author's Address

   Othmar Gsenger
   Sporgasse 6
   Graz  8010
   AT

   Phone:
   Email: otti@wirdorange.org
   URI:   http://anytun.org/









































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