RFC 2890 (rfc2890) - Page 2 of 7


Key and Sequence Number Extensions to GRE



Alternative Format: Original Text Document



RFC 2890       Key and Sequence Number Extensions to GRE  September 2000


   Silently discard
                The implementation discards the datagram without further
                processing, and without indicating an error to the
                sender.  The implementation SHOULD provide the
                capability of logging the error, including the contents
                of the discarded datagram, and SHOULD record the event
                in a statistics counter.

2. Extensions to GRE Header

   The GRE packet header[1] has the following format:

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |C|       Reserved0       | Ver |         Protocol Type         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |      Checksum (optional)      |       Reserved1 (Optional)    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The proposed GRE header will have the following format:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |C| |K|S| Reserved0       | Ver |         Protocol Type         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Checksum (optional)      |       Reserved1 (Optional)    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Key (optional)                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Sequence Number (Optional)                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


     Key Present (bit 2)

     If the Key Present bit is set to 1, then it indicates that the
     Key field is present in the GRE header.  Otherwise, the Key
     field is not present in the GRE header.

     Sequence Number Present (bit 3)

     If the Sequence Number Present bit is set to 1, then it
     indicates that the Sequence Number field is present.
     Otherwise, the Sequence Number field is not present in the GRE
     header.

     The Key and the Sequence Present bits are chosen to be
     compatible with RFC 1701 [2].



Dommety                     Standards Track