In message <2134f8430051b64f815c691a62d983180dc...@xch-blv-504.nw.nos.boeing.co m>, "Templin, Fred L" writes: > Hi Ran, > > > Discussion: > > Deployments using tunnels, whether IP-in-IP, GRE, IPsec tunnel-mode, > > or some other IETF specified technology, are NOT going away. > > Yes, this is the same as I and others have been saying all along. > > > If the physical MTU is 1280, then the tunnel MTU will be smaller. > > Not allowed; the tunnel MUST be able to do a minimum 1280. > > > Nested tunnels are not unusual and can be difficult to detect > > absent a working PMTUD mechanism (whatever that might be). > > Agree that nested tunnels are not unusual and are in fact in > common widespread deployment. But, there is no need to "detect" > them from the source host's perspective as long as they honor > the IPv6 1280 minMTU. That means that tunnels MUST be prepared > to do a small amount of fragmentation and reassembly when > necessary.
And if we generate appoximately equal sized fragments rather than 1280 byte fragments + a runt fragment tunnels would need to fragment less often. Your 1500 byte UDP payloads become 2 x 750 byte fragments which can be encapulated multiple times. It doesn't take a lot of math to work out what size to fragment at to produce optimal fragment sizes for a given MTU. Mark > Thanks - Fred > [email protected] > -------------------------------------------------------------------- > IETF IPv6 working group mailing list > [email protected] > Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 > -------------------------------------------------------------------- -- Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117, Australia PHONE: +61 2 9871 4742 INTERNET: [email protected] -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
