> Yes - I think that's better, actually (less work and a stronger
> statement). Mark, what do you think?
Yes, indeed. I added a sentence to the following paragraph. It is
early, so if there is a better way to say this, please let me know.
Thanks,
allman
---
A TCP receiver SHOULD send an immediate duplicate ACK when an
out-of-order segment arrives. The purpose of this ACK is to inform
the sender that a segment was received out-of-order and which
sequence number is expected. From the sender's perspective,
duplicate ACKs can be caused by a number of network problems.
First, they can be caused by dropped segments. In this case, all
segments after the dropped segment will trigger duplicate ACKs.
Second, duplicate ACKs can be caused by the re-ordering of data
segments by the network (not a rare event along some network paths).
Finally, duplicate ACKs can be caused by replication of ACK or data
segments by the network. In addition, a TCP receiver SHOULD send an
immediate ACK when the incoming segment fills in all or part of a
gap in the sequence space. This will generate more timely
information for experimental loss recovery algorithms, such as
NewReno [Flo98].