Hi Mark, > -----Original Message----- > From: Mark Andrews [mailto:ma...@isc.org] > Sent: Thursday, August 01, 2013 5:36 PM > To: Templin, Fred L > Cc: RJ Atkinson; ipv6@ietf.org > Subject: Re: "Deprecate" > > > In message <2134F8430051B64F815C691A62D983180DCA04@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.
Yes, SEAL covers this in earlier document versions. "Approximately equal length is what it used to say; now it says: " breaks the inner packet into N non-overlapping segments (where N is minimized and each segment is significantly smaller than (MINMTU-HLEN) to allow for additional encapsulations in the path)." but I can modify this to say: "in N approximately equal length non-overlapping segments" to bring back what I had in earlier versions. Thanks - Fred fred.l.temp...@boeing.com > 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 > > fred.l.temp...@boeing.com > > -------------------------------------------------------------------- > > IETF IPv6 working group mailing list > > ipv6@ietf.org > > 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: ma...@isc.org -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
