Recently I've been working on middlebox s/w: Firewalls and NAT. One thing this has brought home to me is just how unreliable fragmentation is on the current Internet. NAT will often simply break it (such that they can not be reassembled) or just discard them, and firewalls are often set up to block them.
As such, almost every protocol now would seem to need protocol level segmentation/fragmentation, rather than depend up IP level fragmentation. It struck me that it should be quite simple to extend HIP to support such. 1) Add a Controls bit which advertises that the sender supports segmentation. 2) Define a new parameter, numbered 1 such that it is first in the parameters, and is critical. Within the parameter have a seqno/identifier, offset and more segments / final segment bit, possibly also a total size field. Define some simple reassembly rules, similar to those for IP fragments, such that one could reassemble a HIP packet larger than 2008 bytes if desired (how big?). 3) Possibly also define a none critical parameter within the non signed, non MACed range which advertises the max size packet the sender is willing to reassemble. In fact I guess this might remove the need to use a Controls bit, since it would imply the sender can reassemble. Then have a rule that once one party has seen the other party advertise the segmentation capability within the current BEX session, it is free to make use of segmentation towards that peer. Thoughts? DF _______________________________________________ Hipsec mailing list [email protected] https://www.ietf.org/mailman/listinfo/hipsec
