Brocade Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide (Supporting R05.6.00) - Manual (Page 43)

Priority Unreserved Bandwidth
0 10,000
1 10,000
2 10,000
3 9,000
4 9,000
5 9,000
6 9,000
7 9,000
Active: LSP with setup 6, hold 3, mean-rate 1,000
Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide 19
53-1003031-02
Traffic engineering database
1
Given the bandwidth allocation above, when an LSP is established with a setup priority of three and
a mean-rate of 9,500 Kbps, it would not pass admission control because only 9,000 Kbps is
available at priority 3.
LSP preemption
When there is not enough unallocated bandwidth on an interface to fulfill the requirements of a
new LSP that has passed admission control, existing LSPs that have a lower priority may be
preempted. When preemption occurs, bandwidth allocated to lower-priority LSPs is reallocated to
the higher-priority LSP. LSP preemption depends on the bandwidth requirements and priority of the
new LSP, compared to the bandwidth allocation and priority of already existing LSPs.
When LSP preemption is necessary, the device uses the following rules:
NOTE
LSP preemption rules have changed to improve the scalability and performance for Fast Reroute
(FRR) enabled LSPs. Please see bullets three and four below for changes to LSP preemption for FRR
enabled LSPs. Changes to LSP preemption for FRR enabled LSPs is supported on Brocade MLX
series, Brocade NetIron XMR, Brocade NetIron CER, and Brocade NetIron CES devices.
• Preempt existing LSPs that have lower priority than the new LSP
• When several existing LSPs have lower priority than the new LSP, preempt the LSP that has the
lowest priority
• When two LSPs have equal priority and one LSP must be preempted, preempt the LSP which is
currently FRR enabled irrespective of its bandwidth requirement
• Preempt as many FRR enabled LSPs as necessary before preempting unprotected LSPs of the
same priority. For example, when both FRR enabled LSPs and non-FRR enabled LSPs are
configured, the system attempts its best to preempt FRR enabled LSPs first before preempting
non-FRR enabled LSPs until the bandwidth requirement is met for a new high priority LSP.
In the example above, bandwidth has been allocated to an LSP that has a hold priority of three and
a mean-rate of 1,000 Kbps. When a new LSP with a setup priority of two, hold priority of one, and
mean-rate of 10,000 Kbps is established, admission control, bandwidth allocation, and LSP
preemption work as described below.