RFC 2918 (rfc2918) - Page 2 of 4

Route Refresh Capability for BGP-4

RFC 2918                Route Refresh for BGP-4           September 2000


2. Route Refresh Capability

   To advertise the Route Refresh Capability to a peer, a BGP speaker
   uses BGP Capabilities Advertisement [BGP-CAP]. This capability is
   advertised using the Capability code 2 and Capability length 0.

   By advertising the Route Refresh Capability to a peer, a BGP speaker
   conveys to the peer that the speaker is capable of receiving and
   properly handling the ROUTE-REFRESH message (as defined in Section 3)
   from the peer.

3. Route-REFRESH Message

   The ROUTE-REFRESH message is a new BGP message type defined as
   follows:

          Type: 5 - ROUTE-REFRESH

          Message Format: One  encoded as

                  0       7      15      23      31
                  +-------+-------+-------+-------+
                  |      AFI      | Res.  | SAFI  |
                  +-------+-------+-------+-------+

          The meaning, use and encoding of this  field is the
          same as defined in [BGP-MP, sect. 7]. More specifically,

               AFI  - Address Family Identifier (16 bit).

               Res. - Reserved (8 bit) field. Should be set to 0 by the
                      sender and ignored by the receiver.

               SAFI - Subsequent Address Family Identifier (8 bit).

4. Operation

   A BGP speaker that is willing to receive the ROUTE-REFRESH message
   from its peer should advertise the Route Refresh Capability to the
   peer using BGP Capabilities advertisement [BGP-CAP].

   A BGP speaker may send a ROUTE-REFRESH message to its peer only if it
   has received the Route Refresh Capability from its peer.  The  carried in such a message should be one of the  that
   the peer has advertised to the speaker at the session establishment
   time via capability advertisement.





Chen                        Standards Track