[tsvwg] design assumptions - draft-ietf-udp-options

[Joe Touch <[e-mail]>]

Getting back to the core design assumptions:

1- support options
2- allow at least some options to be silently ignored by legacy receivers (to enable ‘“optionally enhanced” exchanges)
3- allow at least some options to be required
4- allow the options themselves to be protected
5- support for fragmentation/reassembly
6- support for MTU discovery
7- support (optional?) middlebox checksum/payload length bug traversal
8- support LITE, i.e., where some of the payload is not covered by at least some checksum processing

AFAICT:

#7 requires a CCO-like sum, but it MUST he calculated AFTER all other options are populated (it depends on the value of ALL other options and surplus data)

#8 can depend on everything except CCO (it doesn’t need to protect CCO), but it depends on the value of all other options and needs to be computed next-to-last (or last if CCO isn’t present)

And we need a way to know:
	- for #7, whether CCO is included or not used (at user’s peril, but to allow for transmitters to avoid work)
	- for #8, when to end the options (either a length field OR a EOL flag)

Are there any other design requirements?

Joe