McDATA Eclipse 2640 SAN, Руководство по администрированию и настройке

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5-8
Eclipse™ 2640 SAN Router Administration and Configuration Manual
Configuring iSCSI Ports
1. Select
Smaller CWND Reduction in Fast Recovery
to improve the
performance of the SAN Router when packet losses occur due to
reordering or noise rather than congestion. When enabled, the
SAN Router responds more slowly to congestion events because
the send congestion window (CWND) is reduced to 7/8 of its
previous value as compared to 1/2 in standard TCP.
NOTE:
Do not select this option when other traffic sources sharing the same
TCP link are bursty or intermittent.
2. Select
Quick Start
to improve the initial performance and error
recovery performance on dedicated links with a lot of traffic.
Enabling this increases the initial value for the congestion
window at the beginning of TCP slow starts, and increase the
congestion window size more rapidly.
Standard TCP uses
Slow Start
to protect a network and the other
traffic on it from a sudden burst that can cause congestion
difficulties.
3. Select
Reduced Slow Start Timeout
to reduce the minimum
Slow
Start
timeout from 500 msec to 150 msec. This improves
responsiveness to congestion events that trigger
Slow Start
.
4. Disable
Standard Congestion Avoidance
to disable the slow growth
mode of the SAN Router's congestion window that occurs in the
standard TCP stack when a congestion event is detected.
A congestion event occurs when there is either a transmission
timeout (slowstart timeout) or sufficient duplicate
acknowledgements trigger the fast recovery algorithm. The
growth of the congestion window in congestion avoidance is
normally at the rate of 1/cwnd bytes per ACK received. This
option causes the CWND size to grow at a faster, linear rate. The
SAN Router approximates this and puts a lower limit on the
growth by increasing the cwnd by MIN (segement_size/8, 128)
bytes per ack received.
5. Select
Reorder Resistance
for reliable links that reorder packets
.
Selecting this option will reduce unnecessary packet
retransmission caused by packets being reordered in the TCP
path.
Selecting
Reorder Resistance
increases the number of duplicate
ACKs required to trigger a
Fast Retransmit
or
Fast Recovery
. Use
the next step to specify the number of ACKs.