EXP Computer S200 manual Consider, Nature, Expected Number, SVCs

Spanning Tree Protocol Entity (STPE)

Consider the	A further consideration for setting path cost is the nature and expected number of
Nature and	SVCs that the bridge link uses to achieve its connectivity and adjust the value of
Expected Number	incremental path cost accordingly. For example, consider the topology shown in
of SVCs	Figure 45.

Node B

X25-1

X25-2

Node A

Bridge 1

X25-3

MX25

Bridge 2

Node C

Bridge 3

Node D

Bridge 4

Node E

Figure 45. Bridge Links Within Network

Bridge 2 is linked to bridge 1 by two separate links. The link through Node B must traverse two separate SVC hops while the direct link has only a single hop. If the speed of the lines are all equal, then the cost for the bridge link through Node B should be higher than the cost for the direct link.

On the other hand, if the amount of traffic (due to sources other than bridging traffic) causes added delay for the direct route, or if the direct route has a lower speed, it might be better to use the direct route as a backup. Therefore one would set the cost for the direct route higher than for the Node B route. For the multipoint line connecting bridges 2, 3, and 4, the cost for each link should be increased in proportion to the amount of bandwidth-sharing involved. This also accounts for the fact that a slave node such as Node D or Node E must wait to be polled before it can pass data to its master, thus adding some extra delay.

92 Bridging