User`s guide

3 – Planning
iSCSI/Gigabit Ethernet Performance
FI0054601-00 C 3-3
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Bandwidth
Bandwidth measures the amount of data transmitted over a channel or network. A
1-Gbps/2-Gbps FC port can transmit or receive at nominal rates of 1- or 2-Gbps,
depending on the device to which it is connected. This corresponds to actual
bandwidth values of 106 MB and 212 MB, respectively. WAN data rates range
from 1.5 megabits per second (T1) to greater than 600 megabits per second
(OC-12)
Latency
Latency measures how long a transaction takes to travel through the router or
over a communication link.
iSCSI/Gigabit Ethernet Performance
The SANbox 6142 router supports Ethernet service at transmission rates of
1000-, 100- or 10-Mbps with a MTU size of 1500 or 9000 (jumbo frames). Related
performance characteristics include the following:
 Distance
 Bandwidth
 Latency
Distance
Consider the physical distance between routers. This is usually measured in
round-trip delay. Round-trip delay ranges anywhere from less than 1 millisecond
to as great as 250 milliseconds.
Performance Tuning
Properly configuring the router maximizes its performance. Knowing the round-trip
delay (distance) between routers and the WAN effective data rate (connection
type) allows the routers to be tuned for optimal performance. The following tables
provide TCP Window Scaling Factor and Window Size settings for specific WAN
environments. A table is provided for each connection type.
Table 3-1. T1 / DS-1 – 1.554 Mbits/Sec
Round Trip delay
(ms)
Total Window Size
(bytes)
Scaling Factor
250 64 K 1
100 32 K 0
50 32 K 0