Re: "Deprecate"

[Mark Andrews <[e-mail]>]

In message <[e-mail]
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
> [e-mail]
> --------------------------------------------------------------------
> IETF IPv6 working group mailing list
> [e-mail]
> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
> --------------------------------------------------------------------
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: [phone]                 INTERNET: [e-mail]