InitCwndAfterIdle.seq - The cwnd of the transport address should be adjusted to max(cwnd/2, 4*MTU) when does not transmit data
To check that when the endpoint does not transmit data on a given
transport address, the cwnd of the transport address should be
adjusted to max(cwnd/2, 4*MTU) per RTO.
./InitCwndAfterIdle.seq [-tooloption ...] -pkt ./InitCwndAfterIdle.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 DATA chunk 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
SACK ----------------->
(From DATA1 to DATA 4)
<---------------- DATA 5
SACK ----------------->
(Does not transmit data)
<----------------- HEARTBEAT
HEARTBEAT-ACK ------------------>
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, after received 4 DATA message, send SACK of all
the DATA to endpoint B.
4. Check B: Congestion control window is 5880 now.
5. Received one DATA message on endpoint A and send SACK to this
message.
6. Do not send any message to another endpoint within the current
Heartbeat period. HEARTBEAT message is sent from endpoint B.
7. Check C: Congestion control window is 6000 now.
None
RFC 4960
7.2.1. Slow-Start
Because an endpoint's cwnd is not tied to its Cumulative TSN Ack
Point, as duplicate SACKs come in, even though they may not advance
the Cumulative TSN Ack Point an endpoint can still use them to clock
out new data. That is, the data newly acknowledged by the SACK
diminishes the amount of data now in flight to less than cwnd, and so
the current, unchanged value of cwnd now allows new data to be sent.
On the other hand, the increase of cwnd must be tied to the
Cumulative TSN Ack Point advancement as specified above. Otherwise,
the duplicate SACKs will not only clock out new data, but also will
adversely clock out more new data than what has just left the
network, during a time of possible congestion.
o When the endpoint does not transmit data on a given transport
address, the cwnd of the transport address should be adjusted to
max(cwnd/2, 4*MTU) per RTO.