[OSPF] Re: draft-acee-ospf-multi-instance-00

Hi Vishwas,

 From a protocol standpoint, it is completely backward compatible.  
OSPF routers not supporting the draft but receiving a multicast OSPF  
packet with a non-zero instance ID will simply treat it as an unknown  
AuType and fail authentication.

With this respect, RFC 2328 simply states:

  8.2.  Receiving protocol packets
                          o
                          o
                          o
  o   The packet must be authenticated.  The authentication
        procedure is indicated by the setting of AuType (see
        Appendix D).  The authentication procedure may use one or
        more Authentication keys, which can be configured on a per-
         interface basis.  The authentication procedure may also
         verify the checksum field in the OSPF packet header (which,
         when used, is set to the standard IP 16-bit one's complement
         checksum of the OSPF packet's contents after excluding the
         64-bit authentication field).  If the authentication
         procedure fails, the packet should be discarded.

And:

     D.5 Message verification

         When an OSPF packet has been received on an interface, it must
         be authenticated. The authentication procedure is indicated by
         the setting of Autype in the standard OSPF packet header, which
         matches the setting of Autype for the receiving OSPF interface.

         If an OSPF protocol packet is accepted as authentic, processing
         of the packet continues as specified in Section 8.2. Packets
         which fail authentication are discarded.

Speaking as a draft author (not OSPF WG Co-chair):

Unfortunately, some well-deployed implementations make a bigger fuss  
than is necessary when an authentication failure occurs. IMHO, now  
would be a good time to rectify this to lesses the impact should this  
draft be accepted as a standards track document. Of course, there are  
manual ways of segregating the multi-access networks to avoid down- 
level routers from receiving multicast packets for non-zero  
instances. Perhaps, we should discuss these in the draft and dispense  
with the more radical discussions of requesting new multicast  
addresses or other IANA code points.

Thanks,
Acee

On Jan 24, 2008, at 12:49 PM, Vishwas Manral wrote:

> Hi Acee,
>
> I wanted to know if this draft was backward compatible with current
> implementation. If its not, I was also eager to know, if we have a way
> for incremental deployment.
>
> Thanks,
> Vishwas