[Anima-signaling] GRASP and unicast UDP

[Brian E Carpenter <[e-mail]>]

To entertain myself while waiting for comments on other matters, I spent
quite some time (and swear words) on hacking the prototype GRASP to use
UDP instead of TCP for unicast operations (i.e. discovery responses,
synchronization responses, and negotiation).

My conclusion is that it's a fairly silly thing to do, except possibly
for discovery, which only involved a normal amount of debugging. I'm sure
this is something that DNS server developers are very familiar with:
writing a robust server handling things over UDP is a great deal harder
than doing it with TCP. In fact I gave up when I realised that for
the negotiation case (where there are an unpredictable number of messages
in both directions) I was basically going to have to rewrite half of TCP,
and still not have a robust solution. Without a lot more work, the UDP
solution is riddled with timing-dependent issues. (At one point, adding
a print statement for debugging fixed the bug, so that I simply couldn't
debug it...)

Of course, all this could be solved with more work, but I'm really not
sure we should recommend UDP at all, except for discovery responses.
I can't really imagine a real autonomic node that doesn't have TCP code.

Comments?

    Brian