[Cake] Status of sch_cake and sctp with ECN

[Dave Taht]

It turns out that years ago we incorporated an sctp test into flent
but it doesn't work.

also, I tend to compile netperf with --enable-demo --enable-sctp - but
that *silently* fails unless libsctp is installed.

Anyway flent-fremont's netperf server now supports sctp, and my
firewall for ipv6 doesn't block sctp, and lo and behold,
sctp negotiates ecn.

It does this independent of the setting of the net.ipv4.tcp_ecn
variable. It always negotiates ecn.

However, its congestion control (at least in the framework of the
netperf test) is just miserable, the SCTP_STREAM test
has serious issues trying to saturate a 20Mbit link over 60 seconds.
the STREAM_STREAM_MULTI test does, though,
and you can see cake making CE markings on it. I don't have sufficient
tools or time to look into whether  it's doing the right things or
not. If anyone cares, a packet cap is up at:
http://flent-fremont.bufferbloat.net/~d/sctp/sctp.cap

On the other hand, I'm perfectly happy to have a standard, non-greedy,
reliable, protocol, one capable of multihoming, actually work from
within my home, over ipv6. It feels like the 80s, back when the future
for new protocols looked bright, and disco was king.


d at dancer:~/sctp$ Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

212992 212992   4096    60.00       4.96
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

212992 212992   4096    60.00       4.89
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

212992 212992   4096    60.00       4.89
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

212992 212992   4096    60.00       4.91
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

212992 212992 212992    60.01       0.03
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

212992 212992 212992    60.01       0.03
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

212992 212992 212992    60.01       0.09
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

212992 212992 212992    60.01       0.03