Cisco Systems 8600 Series manual Example 1, 8-Port OC3 BXM Configured in Trunk Mode

cnfrsrc

When a port partition has exhausted its configured guaranteed LCNs (min LCNs), it may draw LCNs for new connections on a FIFO basis from the unallocated LCNs, “z1”, until its maximum number of LCNs, “m1(x)”, is reached or the pool, “z1”, is exhausted.

No limit is actually placed on what may be configured for “m1 (x)”, although “ m1 (x)” is effectively ignored if larger than “z1 + n1”.The value “m1 (x)” is a non-guaranteed maximum value of connection spaces that may be used for a new connection or shared by a number of connections at a given time if there are a sufficient number of unallocated “LCNs available in “z1”. The value m1 (x) typically is not used in Release 9.1, but in future releases allows more control over how the LCNs are shared among multiple VSI partitions.

The following two examples, one for a BXM in port mode and the other for a BXM in trunk mode, provide further detail on the allocation of connections.

Example 1, 8-Port OC3 BXM Configured in Trunk Mode

This example is for an 8-port OC3 BXM configured for trunk mode and therefore, in Release 9.1, with all ports configured as trunks. Table 9-6lists the configured connection space (LCN) allocations for each port of “a (x)”, “n1 (x)”, and “m1 (x)”. It also shows the unallocated LCN pool, “z1” for each port group and the total common pool access, “g”.

Note LCN is the variable affected when configuring connection space allocations using the cnfrsrc command.

The port groups in the example are ports 1-4 and 5-8, and the maximum number of connection spaces (LCNs) per port group is 8192 for this 8-port-OC3 BXM card. The allocations for ports 1-4 are shown in Figure 9-11.The allocations for ports 5-8 are similar to that shown in Figure 9-11,but with correspondingly different values.

As shown in Figure 9-11,“g” is the total number of connection spaces (LCNs) available to port group 1-4 and is equal to 8192 LCNs in this example. To find the number of unallocated LCNs available for use by port partitions that exhaust their assigned number of LCNs, proceed as follows:

From “g”, subtract the sum of the AutoRoute connections, “a (x)”, and the sum of minimum guaranteed LCNs, “n1 (x)”. Also, since the ports in this example are configured in trunk mode, 270 LCNs per port are subtracted from “g”. Since there are four ports, “t” equals “4” in the expression “t*270”. The resulting expression is as follows:

z1 = (g - sum ( a (x) ) - sum ( n1 (x) ) - t*270)

The remaining pool of unallocated LCNs is “z1” as shown. This pool is available for use by ports 1-4 that exceed their minimum VSI LCN allocations “n1 (x)” for partition 1.

The maximum number of LCNs that a port partition can access on a FIFO basis from the unallocated pool “z1” for new connections can only bring its total allocation up to either “(z1 + n1 (x) ) or m1(x)”, whichever value is smaller. Also, since “z1” is a shared pool, the value of “z1” will vary as the common pool is accessed by other port partitions in the group.

The values shown in Table 9-6are obtained as follows:

•For ports 1-4:

z1 = (g - sum ( a(x) ) - sum( n1(x) -4*270)

and factoring in the sum of a (x) and the sum of n1 (x), the above expression evaluates to:

= (8192 - (185) - (3100) -4*270) = 3827 unallocated LCNs

9-40Cisco BPX 8600 Series Reference