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3-6 Alacritech Accelerator Users Guide
through the Windows (host) TCP/IP protocol stack. If most of the
data is moving through the SLIC protocol stack, then performance
of the server will be optimal. Some reasons why data may not be
going through the SLIC protocol stack are:
•
Faulty network wiring or bad connections leading to
dropped frames and runt packets;
•
Inability of older network hardware to autonegotiate
properly;
•
Extremely high network traffic that causes dropped frames
on an intermediate network device such as a switch or hub.
The purpose of the SLIC Performance Monitor objects is to measure
the amount of data transmitted using the SLIC protocol stack, or
FastPath. Any data that is moved using the host protocol stack
instead of the SLIC protocol stack is referred to as SlowPath data. A
healthy TCP/IP connection will be put into FastPath state as soon as
the connection is established, and will stay in FastPath state until the
connection is closed.
As soon as an Alacritech Accelerator finds a problem with a
connection such as a dropped frame, the connection is flushed back
to the host, and is put under the control of the host protocol stack,
SlowPath, until the problem can be resolved. While the connection
is in this SlowPath state, all TCP/IP processing is handled by the
host and the Alacritech accelerator serves only to move Ethernet
frames to and from the network, much like a conventional network
interface card. When the host resolves the network problem, for
example by a retransmission, the connection is moved into FastPath
state and the Alacritech Accelerator once again takes over TCP/IP
processing. The FastPath data rate is the best indication of how
much data is being transmitted using the SLIC protocol stack and
should be at least 95%.
The table below indicates the SLIC objects and counters relevant to
the Accelerator for use with the Performance Monitor.