InitCwndUnderFastRetran.seq - Verify that cwnd is update correctly after a fast retransmit
To check that cwnd is update correctly after a fast retransmit
and detection of packet losses from SACK.
./InitCwndUnderFastRetran.seq [-tooloption ...] -pkt ./InitCwndUnderFastRetran.def
-tooloption : v6eval tool option
See Also: ../common/STD_PKT_COMMON.def
../common/SCTP_COMMON.def
Association is established between endpoint A and B. Arrange data
in endpoint B such that messages is sent to endpoint A.
Endpoint A Endpoint B ULP
(ESTABLISHED) (ESTABLISHED)
<----- Send
<---------------- DATA 1
Don't Send SACK
<---------------- DATA 2
Don't Send SACK
<---------------- DATA 3
Don't Send SACK
<---------------- DATA 4
Don't Send SACK
<---------------- DATA 5
SACK ----------------->
(For DATA 1 and DATA 2)
SACK ----------------->
(For DATA 1 and DATA 3, report DATA 2 is missing)
SACK ----------------->
(For DATA 1, DATA 3 and DATA 4, report DATA 2 is missing)
SACK ----------------->
(For DATA 1, DATA 3 to DATA 5, report DATA 2 is missing)
<---------------- DATA 2
SACK ----------------->
(For all DATAs)
<---------------- DATA 6
SACK ----------------->
TEST DESCRIPTION:
1. Check A: the initial cwnd before DATA transmission is set to 4380.
2. From endpoint B, send valid DATA message 5 times to endpoint A,
when there is association between them.
3. From endpoint A, send SACK of the first 2 DATA messages to
endpoint B.
4. Check B: Congestion control window is 5880 now.
5. From endpoint A, send SACK of the 1st, 3rd DATA messages to
endpoint B, report the 2nd message is missing.
6. From endpoint A, send SACK of the 1st, 3rd and 4th DATA messages
to endpoint B, report the 2nd message is missing.
7. From endpoint A, send SACK of the 1st, 3rd to 5th DATA messages
to endpoint B, report the 2nd message is missing.
8. Check C: The 2nd DATA messages is send again immediately.
9. Check D: Congestion control window is 6000 now.
10.Send SACK of all DATA to endpoint B.
11.Received and SACK the rest DATA messages.
None
RFC 4960
7.2.3. Congestion Control
Upon detection of packet losses from SACK (see Section 7.2.4), an
endpoint should do the following:
ssthresh = max(cwnd/2, 4*MTU)
cwnd = ssthresh
partial_bytes_acked = 0
Basically, a packet loss causes cwnd to be cut in half.
When the T3-rtx timer expires on an address, SCTP should perform slow
start by:
ssthresh = max(cwnd/2, 4*MTU)
cwnd = 1*MTU
and ensure that no more than one SCTP packet will be in flight for
that address until the endpoint receives acknowledgement for
successful delivery of data to that address.