path: root/internet-draft-anytun.txt

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


                  anycast tunneling and relay protocol
                     draft-gsenger-anycast-relay-00

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   Copyright (C) The IETF Trust (2007).















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Abstract

   The anycast tunneling and relay protocol (anytun) defines a protocol
   used for communication between unicast clients and anycast servers.
   It can be used for tunneling information between 2 clients over the
   anycast servers or in relay mode to transmit data form the client
   over the anycast servers to a third party not using the protocol and
   vice versa.  Unlike other tunneling protocols like GRE or IPIP
   tunnels which indeed will work with anycast as well, anytun directly
   includes cryptography and authentication.  In relay mode it also
   supports source NAT with integrated NAT transversal.  It is intended
   to deliver a high performance and reliability solution for tunneling
   and relaying of data over servers, where direct client to client
   connections are not possible or not wanted.





































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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

2.2.1.  anycast udp mode

   Anytun does not define wich lower layer protocols HAVE TO be used,
   but it's most likely used on top of udp.  This section should only
   discuss some issues on udp in combination with anycasting and
   tunnels.











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2.2.2.  Using UDP

   An example of anytun used with udp as 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

   When using UDP no flow controll or retransmission is done, neigther
   by UDP nor anytun.  The encapsulated protocol HAS TO take care of
   this tasks if needed.  UDP however has a checksum of the complete udp
   datagram, so a packet gets discarded if there is a biterror in the
   payload

2.2.3.  Using lightUDP

   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




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   The difference between normal UDP and lightUDP is, that the udp size
   is not set to the length of the full packet, but to the lenght of the
   data used for the checksum and therefor the checksum is only
   calculated for that part.  When using lightUDP, the lenght HAS tO be
   set to the udp header length + the anytun header lenght.  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.

2.2.4.  Fragmentation

   The only way of fully supporting fragmentation would be to syncronise
   fragments between all anycast servers.  This is considered to be to
   much overhead, so there are two non perfect solutions for this
   problems.  Either fragmentation HAS TO be disabled or if not all
   fragments arrive at the same server the ip datagramm HAS TO be
   discarded.  As routing changes are not expected to occure very
   frequently, the encapsulated protocol can do a retransmission and all
   fragments will arrive at the new server.

2.3.  Protocol specification

2.3.1.  Header format

2.3.2.  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 reserverd and not used at the moment.

   Some exmples for protocol types

   HEX
   0000 Reserved
   .... Reserved
   05DC Reserved
   0800 Internet IP (IPv4)
   6558 transparent ethernet bridging
   86DD IPv6

                                 Figure 6










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Appendix A.  The appan


















































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3.  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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