iSR6200 Intelligent Storage Router Installation Guide - QLogic

5–Fibre Channel over IPConfiguring FCIPData CompressionData compression is an option that in some configurations can provide a datathroughput rate greater than the capability of the IP link. The iSR6200 is capableof compressing data at rates up to 190Mbps. The iSR6200 can automaticallyenable or disable compression to achieve maximum throughput on a real-timebasis, depending on the compressibility of the data and the configured bandwidthfor the FCIP route. QLogic recommends that you always enable data compressionand monitor the resulting performance to determine improvement. The FCIP routebandwidth must be correctly configured to realize the affects of automaticcompression.Bandwidth LimitingThe router provides the ability to set the maximum bandwidth used by an FCIProute. This setting is very important because most WANs do not support the1-gigabit data rate of the router’s GE ports. Bandwidth limiting is also needed forthose configurations where the FCIP route is only allocated a portion of the totalbandwidth.NOTE:The bandwidth parameter should never be set higher than the total WANbandwidth; otherwise, performance suffers due to WAN congestion(dropped packets).When a configuration requires that the bandwidth available to the FCIP route be apercentage of the total WAN bandwidth, it is important to correctly calculate thebandwidth and set it accordingly. For instance if the FCIP route is being allocated50 percent of an OC-3 link (150Mbps link), the route bandwidth setting should beas follows:Bandwidth Allocated = 50% × Link Rate75Mbps = 0.5 × 150MbpsFor more information, see “Configuring an FCIP Route Using the CLI” onpage 5-3.TCP Window SettingsThe TCP window size defines the amount of data sent before seeing anacknowledgement. It is used to avoid overwhelming the receiver and still maintaina constant flow of data. The TCP window size is typically calculated based on theRTT and WAN speed.The following tables show the suggested TCP window size settings for IP linksbased on link speed and RTT.5-14 ISR651101-00 G