RE: [RRG] Map-encap, fragmentation, PMTUD etc.

["Templin, Fred L" <Fred.L.Templin@boeing.com>]

>-----Original Message-----
>From: Robin Whittle [mailto:rw@firstpr.com.au] 
>Sent: Monday, July 28, 2008 4:54 PM
>To: Routing Research Group; Routing Research Group
>Cc: Pekka Savola
>Subject: [RRG] Map-encap, fragmentation, PMTUD etc.
>
>I haven't been keeping up with the list of late, but noticed this
>message, in the "Re: [RRG] Six/One Router Design Clarifications"
>thread.  Quoting Pekka, Tony wrote:
>
>> |As a result for encap/decap schemes I specifically want to see
>> |how they 100% avoid fragmentation, or describe how they deal with
>> |it.
>>
>> Cue Fred.  ;-)
>
>  http://tools.ietf.org/html/draft-templin-seal-22

Also the Linux kernel code is here:

  http://osprey67.com/seal

To Pekka's question, fragmentation is not 100%
avoided however it is "tuned out" as early as
possible so as to avoid RFC4963-type problems
(using a "report fragmentation" mechanism).
 
>Please also take a look at:
>
>  http://www.firstpr.com.au/ip/ivip/pmtud-frag/
>
>My approach is intended to cope gracefully with transition to
>jumboframes in the DFZ - so it goes well beyond coping with the
>immediate problem of the encapsulation overhead pushing the final
>packet length over the 1500 byte limit.  I explain it in terms of
>Ivip but I think the principles apply just as well to LISP, 
>APT or TRRP.

SEAL also supports graceful accommodation of larger
path MTUs. Just to be clear, the 2KB reassembly limit
in SEAL is there *only* to accommodate paths with
marginal MTUs. But, larger path MTUs will still be
naturally discovered and utilized.

Fred
fred.l.templin@boeing.com

  
>
>    - Robin
>
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