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SN0051408-00 C 5
6. Configure the iSR6142 Ethernet performance:
a. The TCP window size defines the maximum amount of data transmitted that was unacknowledged
(see Table 3-2). The TCP window size is typically increased to compensate for distance (round trip
delay) and link data rate. The iSR6142 Intelligent Storage Router Installation Guide (SN0051102-00)
contains tables that provide configuration parameters for typical data rates and delays. The TCP
window size configuration includes the following two parameters:
TCP max window size: 8192, 16384, 32768
Window scaling: 0 through 7
b. Bandwidth limiting:
The Ethernet transmit bandwidth utilized by the router is configurable from 2 to 1000 Mbps
(megabits per second). For example, if the WAN connection is capable of 45 MBps (megabytes per
second), but you want to limit FCIP to 33 percent of the available bandwidth, set the router
bandwidth parameter to 15 (15 = 45 x 33 percent).
c. Compression:
As a rule, compression should be set to enable when your Ethernet link data rate is less than
45 Mbps (5 MBps).
d. Jumbo frames:
Using jumbo frames will increase Ethernet efficiency. If used, jumbo frames must be enabled on
both the Ethernet switches and the routers.
Table 3-2. TCP Maximum Window Size
TCP Window Size
(bytes)
TCP Maximum
Window Size Window Scaling
8 K 8,192 0
16 K 16,384 0
32 K 32,768 0
64 K 32,768 1
128 K 32,768 2
256 K 32,768 3
512 K 32,768 4
1 M 32,768 5
2 M 32,768 6
4 M 32,768 7
CAUTION!
Do not set the bandwidth parameter higher than the available WAN bandwidth, otherwise
performance will suffer due to WAN congestion (dropped packets).