HP StorageWorks 8/80 HP StorageWorks Fabric OS 6.1.x administrator guide (5697 - Page 408

WAN tool performance characteristics Table 92 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 later. Table 92 WAN tool performance characteristics Characteristic Description Bandwidth Indicates the total packets and bytes sent. Bytes/second estimates 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 Indicates the 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 within the last display interval. Delay Path MTU (PMTU) Indicates TCP smoothed RTT and variance estimate in milliseconds. 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 may not be accurate. 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 for the following functions: • 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 409 for more information about specifying source and sink mode. 408 Configuring and monitoring FCIP extension services