Cisco ASR 1000 Series Configuration Manual page 47

Configuring TCP
The following output shows that ECN capabilities are enabled at both ends. In response to the ECN-setup
SYN, the other end favorably replied with an ECN-setup SYN-ACK message. This connection is now ECN
capable for the rest of the session.
Device# telnet 10.10.10.10
Trying 10.10.10.10 ... Open
Password required, but none set
!
1d20h: 10.1.25.34:11003 <---> 10.1.25.35:23
1d20h: 10.1.25.34:11003 <---> 10.1.25.35:23
The following example shows how to verify that the hosts are connected:
Device# show debugging
!
TCP:
TCP Packet debugging is on
TCP ECN debugging is on
!
Device# telnet 10.1.25.234
!
Trying 10.1.25.234 ...
!
00:02:48: 10.1.25.31:11001 <---> 10.1.25.234:23
00:02:48: tcp0: O CLOSED 10.1.25.234:11001 10.1.25.31:23 seq 1922220018
00:02:50: 10.1.25.31:11001 <---> 10.1.25.234:23
00:02:50: cwnd from 1460 to 1460, ssthresh from 65535 to 2920
00:02:50: tcp0: R SYNSENT 10.1.25.234:11001 10.1.25.31:23 seq 1922220018
00:02:54: 10.1.25.31:11001 <---> 10.1.25.234:23
00:02:54: cwnd from 1460 to 1460, ssthresh from 2920 to 2920
00:02:54: tcp0: R SYNSENT 10.1.25.234:11001 10.1.25.31:23 seq 1922220018
00:03:02: 10.1.25.31:11001 <---> 10.1.25.234:23
00:03:02: cwnd from 1460 to 1460, ssthresh from 2920 to 2920
00:03:02: tcp0: R SYNSENT 10.1.25.234:11001 10.1.25.31:23 seq 1922220018
00:03:18: 10.1.25.31:11001 <---> 10.1.25.234:23
00:03:18: 10.1.25.31:11001 <---> 10.1.25.234:23
00:03:18: cwnd from 1460 to 1460, ssthresh from 2920 to 2920
00:03:18: tcp0: O SYNSENT 10.1.25.234:11001 10.1.25.31:23 seq 1922220018
00:03:20: 10.1.25.31:11001 <---> 10.1.25.234:23
00:03:20: cwnd from 1460 to 1460, ssthresh from 2920 to 2920
00:03:20: tcp0: R SYNSENT 10.1.25.234:11001 10.1.25.31:23 seq 1922220018
00:03:24: 10.1.25.31:11001 <---> 10.1.25.234:23
00:03:24: cwnd from 1460 to 1460, ssthresh from 2920 to 2920
00:03:24: tcp0: R SYNSENT 10.1.25.234:11001 10.1.25.31:23 seq 1922220018
00:03:32: 10.1.25.31:11001 <---> 10.1.25.234:23
00:03:32: cwnd from 1460 to 1460, ssthresh from 2920 to 2920
00:03:32: tcp0: R SYNSENT 10.1.25.234:11001 10.1.25.31:23 seq 1922220018
!Connection timed out; remote host not responding
OPTS 4 ECE CWR SYN WIN 4128
OPTS 4 ECE CWR SYN WIN 4128
OPTS 4 ECE CWR SYN WIN 4128
OPTS 4 ECE CWR SYN WIN 4128
OPTS 4 SYN WIN 4128
OPTS 4 SYN WIN 4128
OPTS 4 SYN WIN 4128
OPTS 4 SYN WIN 4128
IP Application Services Configuration Guide, Cisco IOS XE Release 3S (Cisco ASR 1000)
Example: Verifying the Configuration of TCP ECN
out ECN-setup SYN
in ECN-setup SYN-ACK
out ECN-setup SYN
congestion window changes
congestion window changes
congestion window changes
SYN with ECN disabled
congestion window changes
congestion window changes
congestion window changes
congestion window changes
39