RFC 2081 (rfc2081) - Page 2 of 4

RIPng Protocol Applicability Statement

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RFC 2081                  RIP-2 Applicability               January 1997


3.  Applicability

   A goal in developing RIPng was to make the minimum necessary change
   to RIP-2 to produce RIPng.  In essence, the IPv4 address was expanded
   into an IPv6 address, the IPv4 subnet mask was replaced with an IPv6
   prefix length, the next-hop field was eliminated but the
   functionality has been preserved, and authentication was removed.
   The route tag field has been preserved.  The maximum diameter of the
   network (the maximum metric value) is 15; 16 still means infinity
   (unreachable).

   The basic RIP header is unchanged.  However, the size of a routing
   packet is no longer arbitrarily limited.  Because routing updates are
   never forwarded, the routing packet size is now determined by the
   physical media and the sizes of the headers which precede the routing
   data (i.e., media MTU minus the combined header lengths).  The number
   routes which may be included in a routing update is the routing data
   length divided by the size of a routing entry.

3.1 Prefix

   The address field of a routing entry is 128 bits in length, expanded
   from the 32 bits available in RIP-2.  This allows the RIP entry to
   carry an IPv6 prefix.

3.2 Prefix Length

   The 32-bit RIP-2 subnet mask field is replaced by an 8-bit prefix
   length field.  It allows the specification of the number of bits in
   the prefix which form the actual prefix.

3.3 Next Hop

   The ability to specify the next hop, rather than simply allowing the
   recipient of the update to set the next hop to the sender of the
   update, allows for the elimination of unnecessary hops through
   routers which are running multiple routing protocols.  Consider
   following example topology:

         -----   -----         -----   -----
         |IR1|   |IR2|         |XR1|   |XR2|
         --+--   --+--         --+--   --+--
           |       |             |       |
         --+-------+-------------+-------+--
           |--------RIPng--------|






Malkin                       Informational
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