RE: [tcpm] New I-D posted : draft-moncaster-tcpm-rcv-cheat-00

> 
> is at odds with RFC 2581, which says:
> 
> > Out-of-order data segments SHOULD be acknowledged immediately, in 
> > order to accelerate loss recovery.
> 
> ...although I wonder why this is only a SHOULD, and not a 
> MUST, and herewith suggest to change this in 2581bis, unless 
> there's a good reason not to do so.

Although the RFC says SHOULD, in reality it is treated as a MUST, I
think the majority of stacks will send a ack for a out-of-order segment.
It probably makes sense to make this a MUST in RFC 2581bis if we want to
enforce some basic congestion control stuff like fast-retransmissions
(which is worded as a MUST by the way).

The only reason which I can think off why it was worded as a SHOULD
instead of a MUST is when the basic cong.control on TCP was written long
time back, "putting" many packets (even if they serve some useful
purpose) was probably considered aggressive, in the current context pure
ACK's. I am sure there are folks in the list who may have better
answers. 

OTOH, recently, we were discussing about rate-limiting the no. of
duplicate ACK's from mis-behaving receivers in the context of RFC
2581bis, now there is a mention about
"some-receivers-that-may-exist-who-don't-send-duplicate-acks-for-out-of-
order-segments-received" 

:-)

-Anantha

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