Installation guide

5–Fibre Channel Over IP
Configuring FCIP
5-14 ISR651101-00 C
Data Compression
Data compression is an option that in some configurations can provide a data
throughput rate greater than the capability of the IP link. The iSR6200 is capable
of compressing data at 150 MB per second. If a FCIP configuration has the
following attributes, data compression should be enabled and the resulting
performance monitored to determine if data compression results in a performance
improvement.
iSR6200/mpx200 (compression rate = 150 MByte/sec)
 Round-Trip Time is greater than 10 milliseconds
 WAN Data Rate is less than 1 gigabits per second
 Data is compressible
Bandwidth Limiting
The router provides the ability to set the maximum bandwidth used by a FCIP
route. This setting is very important because most WANs do not support the 1
gigabit data rate of the router’s GE ports. Bandwidth limiting is also needed for
those configurations where the FCIP route is only allocated a portion of the total
bandwidth.
When a configuration requires that the bandwidth available to the FCIP route be a
percentage of the total WAN bandwidth it is important to correctly calculate the
bandwidth and set it accordingly. For instance if the FCIP route is being allocated
50% of an OC-3 link (150 Mb/sec link), the route bandwidth setting should be as
follows:
Bandwidth allocated = 50% * Link Rate
75Mb/s = 0.5 * 150Mb/sec
For more information, see “Configuring an FCIP Route Using the CLI” on
page 5-3.
TCP Window Settings
The TCP window size defines the amount of data sent before seeing an
acknowledgement. It is used to avoid overwhelming the receiver and still maintain
a constant flow of data. The TCP window size is typically calculated based on the
RTT and WAN speed.
NOTE:
The bandwidth parameter should never be set higher than the total WAN
bandwidth, otherwise performance suffers due to WAN congestion (dropped
packets).