Subject: [Int-area] ip-proto-44 tunneling

From: "Templin, Fred L" <[email-masked]>
Date: Thu, 13 Nov 2014 05:12:58 +0000

I would like to propose a "new" tunneling encapsulation format - call it ip-proto-44
tunneling, or IPv6 Fragment Header (FH) tunneling. It works with  IPvX-in-IPvY
encapsulation for any (X,Y) combinations. So, the possible formats are:

  IPv4/FH/IPv4
  IPv4/FH/IPv6
  IPv6/FH/IPv4
  IPv6/FH/IPv6

Now, if we say that the FH can be "compressed away" by simply not including
it for packets that do not require fragmentation we can then say that ip-proto-4
and ip-proto-41 tunneling are simply compressed versions of ip-proto-44 tunneling
and in fact always have been.

This gives rise to an interesting possibility. When the outer encapsulation header is
IPv4, and the encapsulated packet requires fragmentation, we should be able to
insert an IPv6 Fragment Header between the outer IPv4 header and inner IPv*
header and perform ordinary IPv6 fragmentation even though the outer protocol
is IPv4. With that arrangement, we have now fixed IPv4 fragmentation brokenness
and can use tunnel fragmentation to fix path MTU problems.

All of that said, another possibility is to include the FH even for some/all packets that
do not require fragmentation, i.e., as "atomic fragments". This might be useful in
networks where including a high-quality Identification value in each packet could aid
in duplicate packet detection, reordering detection, etc. But, I understand some
people want to deprecate "atomic fragments".

Comments?

Fred
[email-masked]