Configuring Tcp Parameters - Cisco MDS 9000 series Configuration Manual

Configuring FCIP
S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m

Configuring TCP Parameters

You can control TCP behavior in a switch by configuring the TCP parameters that are described in this
section.
When FCIP is sent over a WAN link, the default TCP settings may not be appropriate. In such cases, we
Note
recommend that you tune the FCIP WAN link by modifying the TCP parameters (specifically bandwidth,
round-trip times, and CWM burst size).
This section includes the following topics:
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Minimum Retransmit Timeout
You can control the minimum amount of time TCP waits before retransmitting. By default, this value is
200 milliseconds (msec).
To configure the minimum retransmit time, follow these steps:
Command
Step 1
switch(config-profile)# tcp
min-retransmit-time 500
switch(config-profile)# no tcp
min-retransmit-time 500
Keepalive Timeout
You can configure the interval that the TCP connection uses to verify that the FCIP link is functioning.
This ensures that an FCIP link failure is detected quickly even when there is no traffic.
If the TCP connection is idle for more than the specified time, then keepalive timeout packets are sent
to ensure that the connection is active. This command can be used to tune the time taken to detect FCIP
link failures.
You can configure the first interval during which the connection is idle (the default is 60 seconds). When
the connection is idle for the configured interval, eight keepalive probes are sent at 1-second intervals.
If no response is received for these eight probes and the connection remains idle throughout, that FCIP
link is automatically closed.
Cisco MDS 9000 Family NX-OS IP Services Configuration Guide
2-12
Minimum Retransmit Timeout, page 2-12
Keepalive Timeout, page 2-12
Maximum Retransmissions, page 2-13
Path MTUs, page 2-13
Selective Acknowledgments, page 2-13
Window Management, page 2-14
Monitoring Congestion, page 2-15
Estimating Maximum Jitter, page 2-15
Buffer Size, page 2-16
Purpose
Specifies the minimum TCP retransmit time for the TCP
connection to be 500 msec. The default is 200 msec and the
range is from 200 to 5000 msec.
Reverts the minimum TCP retransmit time to the factory
default of 200 msec.
Chapter 2 Configuring FCIP
OL-19525-01,Cisco MDS NX-OS Release 4.2(1)