Cisco ASR 1000 Series Configuration Guide

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 out ECN-setup SYN
1d20h: 10.1.25.34:11003 <---> 10.1.25.35:23 in ECN-setup SYN-ACK
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 out ECN-setup SYN
00:02:48: tcp0: O CLOSED 10.1.25.234:11001 10.1.25.31:23 seq 1922220018
OPTS 4 ECE CWR SYN WIN 4128
00:02:50: 10.1.25.31:11001 <---> 10.1.25.234:23 congestion window changes
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
OPTS 4 ECE CWR SYN WIN 4128
00:02:54: 10.1.25.31:11001 <---> 10.1.25.234:23 congestion window changes
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
OPTS 4 ECE CWR SYN WIN 4128
00:03:02: 10.1.25.31:11001 <---> 10.1.25.234:23 congestion window changes
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
OPTS 4 ECE CWR SYN WIN 4128
00:03:18: 10.1.25.31:11001 <---> 10.1.25.234:23 SYN with ECN disabled
00:03:18: 10.1.25.31:11001 <---> 10.1.25.234:23 congestion window changes
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
OPTS 4 SYN WIN 4128
00:03:20: 10.1.25.31:11001 <---> 10.1.25.234:23 congestion window changes
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
OPTS 4 SYN WIN 4128
00:03:24: 10.1.25.31:11001 <---> 10.1.25.234:23 congestion window changes
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
OPTS 4 SYN WIN 4128
00:03:32: 10.1.25.31:11001 <---> 10.1.25.234:23 congestion window changes
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
OPTS 4 SYN WIN 4128
!Connection timed out; remote host not responding
IP Application Services Configuration Guide, Cisco IOS XE Release 3S (Cisco ASR 1000)
39
Configuring TCP
Example: Verifying the Configuration of TCP ECN

Cisco ASR 1000 Series Specifications

General

Brand	Cisco
Model	ASR 1000 Series
Category	Network Router
Language	English