HP StorageWorks Enterprise File Services WAN Accelerator - Manual (Page 44)

44 2 - C ONFIGURING THE HP EFS WAN A CCELERATOR
Enabling
HSTCP Protocol
Options
Optionally, you can enable the High Speed Transmission Control Protocol (HSTCP)
blade in the Setup: Optimization Service - Protocol HSTCP page. HSTCP provides
acceleration and high throughput for high bandwidth networks where the WAN pipe is
large but latency is high. HSTCP is activated for all connections that have a
Bandwidth-Delay Product (BDP) larger than 100 packets. HSTCP is available only on
the HP EFS WAN Accelerator 5010.
To configure HSTCP you must:
‹ enable HSTCP support.
‹ increase the WAN buffers to 2 Bandwidth Delay Product (BDP) or 10 MB. You
can calculate the BDP WAN buffer size. For example, for a link of 155 Mbps and
100 ms round-trip delay, the WAN buffers should be set to:
2 * 155 Mbps * 100 ms = 1937500 bytes
‹ increase the LAN buffers to 1 MB.
‹ enable in-path support. For detailed information, see “Enabling In-Path and Out-
of-Path Support” on page 22 .
‹ disable the Lempel-Ziv (LZ) compression and SDR in in-path optimization
policies. For detailed information about optimization policies if your WAN link
capacity is 100 Mbps, see
“Setting Optimization Policies” on page 28 .
With SDR enabled your throughput will bottleneck between 100 and 150 Mbps, which
cancels out the benefit of HSTCP. If you have an Optical Carrier-3 line or faster,
turning off SDR makes sense and allows HSTCP to reach its full potential. For a 2
Mbps link, regardless of the amount of latency, it is better to keep SDR enabled,
because the HSTCP mechanism is typically not triggered until you reach beyond 100
Mbps of WAN throughput.