Hi Acee, I disagree about the "original intent" of the MTU field. As I see it, it's function is to prevent an OSPF adjacency from forming over a link where the endpoints disagree about the link MTU. We do this primarily to prevent the data plane from using a link that will drop packets sent to a system with an MTU smaller than ours.
While OSPFv3 certainly needs to know the IPv6 link MTU when building it's packets, this information should be available locally without reference to the MTU field in the DBD packet. So, I would argue that in af-alt the MTU in the DBD packet should be for the address family we are routing, not IPv6 in all cases. Regards, Paul Acee Lindem wrote: > Hi Prasanna, > > On May 28, 2008, at 8:18 AM, Prasanna Kumar A.S wrote: > >> Hi >> I just wanted to understand what the primary use of exchanging >> MTU in >> DD packets and doing MTU-check is? Is it only for the control plane or >> is it for the DATA-plane? > > Control-plane - when sending DD, LSR, and LSU packets, OSPF will > attempt to send as many LSA headers or complete LSAs as will fit in a > maximum sized packet. > > >> Why I am getting this doubt is, in draft-ietf-ospf-af-alt-06.txt >> doesn't >> specify which MTU we should use while exchanging the DD packet for the >> ipv4-unicast or ipv4-mutlticast Address-family, is it ipv6-mtu or >> ipv4-mtu? > > We have this clarified in the an update which we post soon. Since > this is OSPFv3 which using IPv6 for transport, you always use the > IPv6 MTU. > > Thanks, > Acee > > >> >> Regards >> Prasanna >> _______________________________________________ >> OSPF mailing list >> [email protected] >> https://www.ietf.org/mailman/listinfo/ospf > > _______________________________________________ > OSPF mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/ospf _______________________________________________ OSPF mailing list [email protected] https://www.ietf.org/mailman/listinfo/ospf
