ACK
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... acknowledged. Even though the route may be
asymmetric, an ACK for new data proves that the
acknowleged data must have been transmitted
successfully.
...
... SYN-RCVD should be labeled
with "snd SYN,ACK", to agree with the text on page 68
and with Figure 8.
...
...
It is extremely important to remember that ACK
(acknowledgment) segments that contain no data ...
... not supported, a connection may hang forever when an
ACK segment that re-opens the window is lost.
...
...
This procedure minimizes delay if the zero-window
condition is due to a lost ACK segment containing a
window-opening update ...
... In general, the processing of received segments MUST be
implemented to aggregate ACK segments whenever possible.
For example, if the TCP ...
... TCP is processing a series of queued
segments, it MUST process them all before sending any ACK
segments.
...
... states other than SYN-RECEIVED: ESTABLISHED, FIN-WAIT-
1, FIN-WAIT-2, CLOSE-WAIT, CLOSING, LAST-ACK, and
TIME-WAIT.
...
... (g) Check ACK field, ESTABLISHED state, p. 72: The ACK is a
duplicate if SEG.ACK =< SND.UNA (the = was omitted).
...
... state, p. 72: The ACK is a
duplicate if SEG.ACK =< SND.UNA (the = was omitted).
Similarly, the window should be updated if: SND.UNA =<
SEG.ACK ...
... ACK =< SND.UNA (the = was omitted).
Similarly, the window should be updated if: SND.UNA =<
SEG.ACK =< SND.NXT.
...
... RFC-793std7 (see page 74) was ambiguous about whether or
not an ACK segment should be sent when an out-of-order
segment was received, i.e., when SEG.SEQ ...
... algorithm, the sender uses the
"redundant" ACK's to deduce that a segment has been
lost before the retransmission timer ...
... lost before the retransmission timer has expired. It
counts the number of times an ACK has been received
with the same value of SEG.ACK and with the same right
...
... counts the number of times an ACK has been received
with the same value of SEG.ACK and with the same right
window edge. If more than a threshold ...
... edge. If more than a threshold number of such
ACK's is received, then the segment containing the
octets starting ...
... segment containing the
octets starting at SEG.ACK is assumed to have been lost
and is retransmitted, without awaiting a timeout. The
threshold ...
... Internet and the hosts by
sending fewer than one ACK (acknowledgment) segment per data
segment ...
...
A TCP SHOULD implement a delayed ACK, but an ACK should not
be excessively delayed; in particular, the delay MUST be
...
... A TCP SHOULD implement a delayed ACK, but an ACK should not
be excessively delayed; in particular, the delay MUST be
less than 0.5 seconds, and in a stream ...
...
A delayed ACK gives the application an opportunity to
update the window and perhaps to send an immediate
...
... response. In particular, in the case of character-mode
remote login, a delayed ACK can reduce the number of
segments sent by the server ...
... In addition, on some large multi-user hosts, a delayed
ACK can substantially reduce protocol processing
overhead by reducing the total number of packets to be
...
... overhead by reducing the total number of packets to be
processed [TCP:5]. However, excessive delays on ACK's
can disturb the round-trip timing and packet "clocking"
...
... customarily known as "updating the window". This
algorithm combines with the delayed ACK algorithm (see
Section 4.2.3.2) to determine when an ACK ...
... ACK algorithm (see
Section 4.2.3.2) to determine when an ACK segment
containing the current window will really be sent to
...
... Recommended initial values and bounds |4.2.3.1 | |x| | | |
| | | | | | |
Generating ACK's: | | | | | | |
Queue out-of-order ...
... out-of-order segments |4.2.2.20| |x| | | |
Process all Q'd before send ACK |4.2.2.20|x| | | | |
Send ACK for out-of-order segment ...
... Process all Q'd before send ACK |4.2.2.20|x| | | | |
Send ACK for out-of-order segment |4.2.2.21| | |x| | |
Delayed ACK ...
... ACK for out-of-order segment |4.2.2.21| | |x| | |
Delayed ACK's |4.2.3.2 | |x| | | |
Delay < 0.5 seconds |4.2.3.2 |x| | | | |
Every 2nd full-sized segment ...
... Delay < 0.5 seconds |4.2.3.2 |x| | | | |
Every 2nd full-sized segment ACK'd |4.2.3.2 |x| | | | |
Receiver SWS-Avoidance Algorithm ...
...
- Default at least 2 hrs. |4.2.3.6 |x| | | | |
- Tolerant of lost ACK's |4.2.3.6 |x| | | | |
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