RE: Move TS to optional (RE: Don't remove TS from IKEv2)

[Stephen Kent <kent@xxxxxxx>]

I think it worth noting that there is considerable pressure to not 
make the ESP header any larger. Good engineering practice suggests 
that if additional signaling info is needed only infrequently, 
relative to the vast majority of traffic sent on an SA, then it makes 
more sense to perform the signalling in a fashion that does not 
increase the size of the header for the vast majority of the traffic, 
and that does not add additional processing burden (e.g., examination 
of any part of the packet) for that vast majority.  The ESP header 
has no spare bits available for signalling; it consists of only the 
the SPI and the sequence number. Adding info to the trailer would 
violate the second of my suggestions above, re additional 
examination. I'd suggest we think in terms of additional phase 2 
exchanges in SOI.

Steve