HP AE370A - Brocade 4Gb SAN Switch 4/12, Administrator'S Manual

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Fabric OS 5.2.x administrator guide 391
WAN Tool performance characteristics
The following table lists the end-to-end IP path performance characteristics that you can display using the
portCmd ipPerf
command and option. All four of the base
ipPerf
performance characteristics
(bandwidth, loss, RTT, PMTU) are provided in the command output in Fabric OS 5.2.0 or higher.
Starting WAN Tool analysis
Typically, you start the WAN tool before setting up a new FCIP tunnel between two sites. You can configure
and use the
ipPerf
option immediately after installing the IP configuration on the FCIP port (for example,
IP address, route entries). Once the basic IP addressing and IP connectivity is established between two
sites, you can configure
ipPerf
with parameters similar to what will be used when the FCIP tunnel is
configured.
The traffic stream generated by the WAN tool ipperf session can be used to:
• Validate a service provider Service Level Agreement (SLA) throughput, loss, and delay characteristics.
• Validate end-to-end PMTU, especially if you are trying to eliminate TCP segmentation of large Fibre
Channel (FC) frames.
• Study the effects and impact FCIP tunnel traffic may have on any other applications sharing network
resources.
To start an
ipPerf
session, you can use any port as long as the port (in combination with local interface)
is not in use. You must run the
ipPerf
client on both the host (source mode, -S option) and receiver (sink
mode, -R option). See ” WAN Tool IpPerf syntax ” on page 391for more information about specifying source
and sink mode.
Figure 35 WAN Tool performance characteristics
Characteristic Description
Bandwidth Indicates the total packets and bytes sent. Bytes/second estimate are
maintained as a weighted average with a 30 second sampling frequency
and also as an average rate over the entire test run. The CLI output prints
the bandwidth observed in the last display interval as well as the
Weighted Bandwidth (WBW).BW represents what the FCIP tunnel / FC
application sees for throughput rather than the Ethernet on-the-wire bytes.
Loss Loss estimate is based on the number of TCP retransmits (assumption is
that the number of spurious retransmits is minimal). Loss rate (percentage)
is calculated based on the rate of retransmissions with in the last display
interval.
Delay Round Trip Time (RTT). Indicates TCP smoothed RTT and variance estimate
in milliseconds.
Path MTU (PMTU) Indicates the largest IP-layer datagram that can be transmitted over the
end-to- end path without fragmentation. This value is measured in bytes
and includes the IP header and payload.
There is a limited support for black hole PMTU discovery. If the Jumbo
PMTU (anything over 1500) does not work, ipperf will try 1500 bytes
(minimum PMTU supported for FCIP tunnels). If 1500 PMTU fails, ipperf
will give up. There is no support for aging. PMTU detection is not
supported for active tunnels. During black hole PMTU discovery, the BW,
Loss, and PMTU values printed might not be accurate.