Expand Configuration and Management Manual (G06.24+)

Tuning
Expand Configuration and Management Manual—523347-008
20-32
Example 2: Reducing Passthrough Traffic
Example 2: Reducing Passthrough Traffic
It is common for the role of a node in an Expand network to change over a period of
time. Example 20-7 shows a situation in which the routine, simple collection of
Measure SYSTEM entity data helped an operations staff discover that certain nodes in
the network had become switches—that is, their resources were used primarily for
passthrough traffic. Further investigation showed that the simple rerouting of
communications lines would help to recover some processor resources and free
controllers to be used elsewhere, perhaps in more stressed network paths.
Measuring Passthrough Traffic on a Single Node
Example 20-7 shows a summary of Measure SYSTEM entity data on a node called
\JUICE. The data was captured by Measure, placed in a structured file, and then
formatted with Enform.
The SYSTEM data allows you to compare the number of Expand frames transferred
between a node and its neighbors to those that are simply forwarded or passed
through to other nodes. Passthrough traffic is shown in the SENT-FWD and RCVD-
FWD counters. Total passthrough traffic is shown in the TOTAL FORWARD column.
Notice that the source and destination of passthrough traffic cannot be identified from
Measure data.
By comparing the total DIRECT frames to the total FORWARD frames, you can
determine that \JUICE is used primarily as a switch in the network among \TOPPER,
\TONY, and \TRGGR. Ninety-seven percent of the data (1,184,392 frames, as shown
in the TOTAL FORWARD column) sent to \JUICE from \TOPPER was passed on to
other nodes.
Similar measurements made on \TOPPER and \TONY would show that all the frames
forwarded through \JUICE to and from \TONY went to \TOPPER. About 300,000 bytes
were received from \TONY and sent to \TOPPER, and about 300,000 bytes were
received from \TOPPER and sent to \TONY. As a result, \JUICE is spending more time
processing passthrough traffic between \TOPPER and \TONY than it is sending direct
traffic.
Making a direct connection between \TONY and \TOPPER would eliminate 600,000
frames of passthrough traffic on \JUICE and would result in a 40 percent reduction in
unnecessary switched traffic. Additional benefits would include a reduction in the
Example 20-7. Passthrough Traffic From Measure SYSTEM Counters on \JUICE
<========Expand FRAMES============> TOTAL TOTAL
SYSTEM LINKS SENT RECEIVED SENT-FWD RCVD-FWD DIRECT FORWARD
===================================================================
\TOPPER 9816 21605 20549 604067 580325 42154 1184392
\TONY 98328 292025 386625 294042 310158 678650 604200
\TRIGGR 46 177 140 123022 85795 317 208817
\SCOUT 24779 51396 55189 102819 2160 106585 104979
\FURY 10529 21725 23774 50291 50734 45499 101025