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

   This section gives an overview of possible operation modes und usage
   scenarios.  Please note, that the protocols used in the figures are
   only examples and that anytun itself does not care about either
   transport protocols or encapsulated protocols.  Routing and network
   address translation is not done by anytun.  Each implemetation MAY
   choose it's own way of doing this task (e.g. using functions provided
   by the operating system).  Anytun is used to establish and controll
   tunnnels, to encapsulate and encrypt data.

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


















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2.2.1.  anycast udp mode

   An example of anytun used with udp transport

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

                                 Figure 4

   In anycast udp mode the data between clients and anycast serveres is
   carried by udp packets.  Packets are routed by the serveres from one
   client to another.  Because udp is stateless no inforamtion has to be
   syncronised

2.2.2.  anycast light udp mode

   An example of anytun used with udp transport

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

                                 Figure 5

   The light UDP mode is neerly the same as the normal UDP mode, the



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   only difference is, that the udp size is set to the udp header lenght
   and not to the length of the full packet and therefor the checksum is
   only calculated for the udp header itself.  So there is no error
   correction or detection done on the payload.  This can be usefull if
   realtime data is beeing transimittet or the tunneled protocol does
   error correction/detection by itself.

2.2.3.  unicast tcp with anycast initialisation

2.2.4.  full anycast tcp

2.2.4.1.  Introduction

   TCP is statefull, this is a big problem, because everey anycast
   server hast to know the tcp state.  The TCP state has to be synced
   between the servers, that meens a lot of overhead.  To keep this
   amount small and therefor make anycast TCP connections efficient some
   tricks SHOULD be used.

2.2.4.2.  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

3.2.  Protocol field

   The protocol field defines the payload protocol.  ETHER TYPE protocol
   numerbers are used. http://www.iana.org/assignments/ethernet-numbers
   .  The values 0000-05DC are not used for DIX ethernet lenght, but are
   reservered for special purposes.  As the definition of transparent
   ethernet bridging is very unclear 2 special types are added for
   ethernet frames

   Protocol Types

   HEX
   0000 Reserved
   0001 Raw Ethernet - both IEEE 802.3 and DIX ethernet
                       without preamble,SFD, PAD and FCS
   0002 Raw ethernet with FCS
   0003 Reserved
   .... Reserved
   05DC Reserved
   05DD as in http://www.iana.org/assignments/ethernet-numbers
   .... as in http://www.iana.org/assignments/ethernet-numbers
   0800 Internet IP (IPv4)
   .... as in http://www.iana.org/assignments/ethernet-numbers
   86DD IPv6
   .... as in http://www.iana.org/assignments/ethernet-numbers

                                 Figure 6




















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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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