path: root/internet-draft-satp.txt

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


                secure anycast tunneling protocol (satp)
           draft-gsenger-secure-anycast-tunneling-protocol-00

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   Copyright (C) The IETF Trust (2007).















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Abstract

   The secure anycast tunneling protocol (satp) defines a protocol used
   for communication between any combination of unicast and anycast
   tunnel endpoints.  It allows tunneling of every ETHER TYPE protocol
   (e.g. ethernet, ip, arp ...).  SATP directly includes cryptography
   and message authentication based on the methodes used by SRTP.  It is
   intended to deliver a generic, scaleable and secure solution for
   tunneling and relaying of packets of any protocol.










































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1.  Introduction

   SATP is somehow a mixture of a generic encapsulation protocol like
   GRE [1] and a secure tunneling protocol as IPsec [2] in tunnel mode.
   To save some header overhead it uses the encryption technices of SRTP
   [3].  It supports peer to peer tunnels, where tunnel endpoints can be
   any combination of unicast, multicast or anycast hosts, so it defines
   a Host Anycast Service [4]











































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2.  Motivation and usage scenarios

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

2.1.  Usage scenarions

2.1.1.  tunneling from unicast hosts over anycast routers to other
        unicast hosts

   An example of SATP used to tunnel in an unicast client - anycast
   server model

                       --------- router -----------
                      /                            \
       unicast ------+---------- router ------------+------ unicast
       host           \                            /        host
                       --------- router -----------

     unicast  | encrypted     |  anycast  | encrypted     |  unicast
     tunnel   | communication |  tunnel   | communication |  tunnel
     endpoint | using SATP    |  endpoint | using SATP    |  endpoint

                                 Figure 1

   In this scenario the payload gets encapsuleted into a SATP packet by
   a unicast host and gets transmitted to one of the anycast routers.
   It than gets decapsulated by the router.  This router makes a routing
   descision based on the underlying protocol and transmits a new SATP
   package to one or more unicast hosts depending on the routing
   descition.















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2.1.2.  tunneling from unicast hosts to anycast networks

   An example of SATP used to encrypt data between a unicast host and
   anycast networks

                          -------Router -+---- DNS Server
                         /                \
                        /                  --- 6to4 Router
                       /
       unicast -------+----------Router --+--- DNS Server
       host            \                   \
                        \                   --- 6to4 Router
                         \
                          -------Router -+---- DNS Server
                                          \
                                           --- 6to4 Router

     unicast  | encrypted     |  anycast  | plaintext
     tunnel   | communication |  tunnel   | anycast
     endpoint | using SATP    |  endpoint | services


                                 Figure 2

2.1.3.  redundant tunnel connection of 2 networks

   An example of SATP used to connect 2 networks

                 Router -----------   ---------------Router
               /                   \ /                     \
       Network - Router ------------x                       Network
          A    \                   / \                     /   B
                 Router -----------   ---------------Router

               | packets       |  packets  |  packets      |
    plaintext  | get           |  take a   |  get          | plaintext
    packets    | de/encrypted  |  random   |  de/encrypted | packets
               |de/encapsulated|   path    |de/encapsulated|


                                 Figure 3

   Network A has multible routers, that act as gateway/tunnel endpoint
   to another network B. This is done to build a redundant encrpted
   tunnel connection between the two networks.  All tunnel endpoints of
   network A share the same anycast address and all tunnel endpoints of
   network B share another anycast address.  When a packet from network
   a gets transmitted to network B, it first arrives on one of networks



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   A border routers.  Which router is used is determined by network A's
   internal routing.  This router encapsulates the package and sends it
   to the anycast address of the network B routers.  The SATP packet
   arrives at one of network B's routers and gets decapsulated and
   routed to it's destination within network B.

2.2.  Encapsulation

   SATP does not depend an which lower layer protocols is used, but it's
   most likely used on top of ip or udp.  This section should only
   discuss some issues on ip and udp in combination with anycasting and
   tunnels.

   Examples of SATP used with different lower layer and payload
   protocols

       +------+-----+-------------------------------+
       |      |     |      + ---------------+------ |
       | IPv6 | UDP | SATP | Ethernet 802.3 | ... | |
       |      |     |      +----------------+-----+ |
       +------+-----+-------------------------------+

   Tunneling of Ethernet over UDP/IPv6

       +------+-----+---------------------------+
       |      |     |      +------+-----+-----+ |
       | IPv4 | UDP | SATP | IPv6 | UDP | RTP | |
       |      |     |      +------+-----+-----+ |
       +------+-----+---------------------------+

   Tunneling of IPv6 over UDP/IPv4 with RTP payload

       +------+-------------------------------+
       |      |      + ---------------+------ |
       | IPv6 | SATP | Ethernet 802.3 | ... | |
       |      |      +----------------+-----+ |
       +------+-------------------------------+

   Tunneling of Ethernet over IPv6

       +------+---------------------------+
       |      |      +------+-----+-----+ |
       | IPv4 | SATP | IPv6 | UDP | RTP | |
       |      |      +------+-----+-----+ |
       +------+---------------------------+

   Tunneling of IPv6 over IPv4 with RTP payload




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                                 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

2.3.  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.

































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3.  Protocol specification

3.1.  Header format

   Protocol Format

        0                   1                   2                   3
      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |           sender ID           |         sequence number       | |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
   | |              ....        payload        ...                   | |
   | |-------------------------------+-------------------------------+ |
   | | padding (OPT) | pad count(OPT)|         payload type          | |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | ~                          MKI (OPTIONAL)                       ~ |
   | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
   | :                 authentication tag (RECOMMENDED)              : |
   | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
   |                                                                   |
   +- Encrypted Portion*                      Authenticated Portion ---+

                                 Figure 5

3.2.  sender ID

   The sender ID is a 8bit unsigned integer.  It HAS TO be unique for
   every sender sharing the same anycast address

3.3.  sequence number

   The sequenze number is a 24 bit unsigned integer in network byte
   order.  It starts with a random value and is increased by 1 for every
   sent packet.  After the maximum value, it starts over from 0.  This
   overrun causes the ROC to be increased.

3.4.  payload

   A packet of the type payload type (e.g. an IP packet).

3.5.  padding (OPTIONAL)

   Padding of max 255 ocitets.  None of the pre-defined encryption
   transforms uses any padding; for these, the plaintext and encrypted
   payload sizes match exactly.  Transforms are based on transforms of
   the SRTP protocol and these transforms might use the RTP padding
   format, so a RTP like padding is supported.  If padding field is



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   present, than the padding count field MUST be set to the padding
   lenght.

3.6.  padding count

   The number of octets of the padding field.  This field is optional.
   It's presents is signaled by the key management and not by this
   protocol.  If this field isn't present, the padding field MUST NOT be
   present as well.

3.7.  payload type field

   The payload type field defines the payload protocol.  ETHER TYPE
   protocol numerbers are used.  See IANA assigned ethernet numbers [5]
   .  The values 0000-05DC are reserverd and MUST NOT be used.

   Some examples for protocol types

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

                                 Figure 6

3.8.  Encryption

   Encryption is done in the same way as for SRTP [3].  This section
   will only discuss some small changes that HAVE TO be made.



















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Appendix A.  The appan


















































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4.  References

   [1]  Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. Traina,
        "Generic Routing Encapsulation (GRE)", RFC 2784, March 2000.

   [2]  Kent, S. and R. Atkinson, "Security Architecture for the
        Internet Protocol", RFC 2401, November 1998.

   [3]  Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
        Norrman, "The Secure Real-time Transport Protocol (SRTP)",
        RFC 3711, March 2004.

   [4]  Partridge, C., Mendez, T., and W. Milliken, "Host Anycasting
        Service", RFC 1546, November 1993.

   [5]  <http://www.iana.org/assignments/ethernet-numbers>



































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Author's Address

   Othmar Gsenger
   Puerstingerstr 32/7
   Saalfelden  5760
   AT

   Phone:
   Email: satp@gsenger.com
   URI:   http://www.gsenger.com/satp/









































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