At 11:09 PM 7/10/01, Michael L. Williams wrote:
>You're correct, and I should be more careful with my terminology....
>segments are what TCP deals with.... I'm wondering how you could get away
>with writing an RFC that doesn't specify something as critical as sending
>ACKs.... =)
Well, I think the normal thing used to be to ACK when you received all the
bytes in your window size. In fact, I still see that when sniffing. But
it's not what the RFC says.
> > I think you mean bytes. He certainly didn't see that many packets without
> > an ACK! Plus TCP sequences and ACKs bytes, not packets.
>
>My numbers (32768, 65536, etc) were just "made up" for sake of example....
>but your statement confuses me.... ACKs bytes? Since this is all TCP, and
>the segments are what receive the sequence numbers, wouldn't TCP send an ACK
>saying "I've received sequence (or up to sequence) number "? Why
>would the ACK acknowledge the actual number of bytes?
TCP sequences bytes, ACKs bytes, and the receive window is how many bytes
can be accepted.
Of course, TCP sends multiple bytes per segment and multiple segments per
window. But the numbers deal with bytes. So, if I say my receive window is
65536, I'm saying I can receive that many bytes, not that many segments.
When I say the sequence number for this segment is 2453, that's the
sequence number of the first byte in the segment. Let's say I send 1000
bytes, because the other side said that's what its max segment size is. The
other side sends an ACK (perhaps delayed). The ACK number is 3453. The ACK
number indicates that the recipient received up through byte number 3452
and is expecting 3453 next.
Priscilla
>I've read RFC 2001 and it's cool.... I need to read it closer and get a
>better understanding of slow start, congestion avoidance, fast retransmit,
>and fast recovery....
>
>Mike W.
________________________
Priscilla Oppenheimer
http://www.priscilla.com
Message Posted at:
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