Anybody normally send packets with unused options?


Murray.pa@Xerox.COM
Thu, 27 Mar 86 19:21:55 PST


I'm doing my homework in preparation for teaching Cedar about IP and
TCP. Cedar doesn't really like variable length chunks in the middle of
records. I can use pointers but it seems worthwhile to explore
alternatives.

I'm thinking of pretending that the options fields live at the end of
the buffer and making the low level driver slosh things around to put
everything in the correct place. Since the options fields are almost
always unused, the sloshing won't normally take any cycles. It looks
like I can have my cake and eat it too.

The question is, has somebody else already sliced the cake some other
way? For example, is some system normally sending a few empty option
bytes to trick the alignment into comming out clean in their
environment?

Does anybody have any data on how often non-empty options are used? John
and I watched some traffic arriving at XEROX.COM, and we didn't see any.



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