Brocade Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide (Supporting R05.6.00) - Manual (Page 45)

Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide 21
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Traffic engineering database
1
After preemption, the reservable bandwidth array for the interface looks like this:
Priority Unreserved Bandwidth
0 2,500
1 2,500
2 2,500
3 0
4 0
5 0
6 0
7 0
Active: LSP with setup 1, hold 0, mean-rate 7,500
LSP with setup 4, hold 3, mean-rate 2,500
Preempted: LSP with setup 3, hold 2, mean-rate 5,000
Calculating a path based on an interface address
Under normal conditions, router IDs are used to configure hops within an MPLS path. In situations
where the user wants to exercise more control over the path, the user can specify actual interface
addresses in the MPLS path to make sure that the path traverses the interface specified. In
previous versions, the CSPF calculation would always resolve a specified interface address to the
router ID. Consequently, although a particular interface on a router is specified, the CSPF
calculation can end up connecting the path through a different interface on the router where the
interface has been specified.
In the network described in Figure 8 , the source node is “A” and the destination node is “E”. In this
configuration, incoming and outgoing interfaces are defined in the figure by their relationship to
where the arrowhead on the connecting line points. The arrowheads point to the incoming interface
from the outgoing interface. For instance “A1”, “A2” and “A3” are the outgoing interfaces of node A
and “C1” and “C2” are the incoming interfaces of node C. The following example describes how
the router might calculate a path between “A” and “B” under the default operating condition.
In this example, an MPLS path has been configured with a source “A” and a destination “E1”.
Under default operation, the interface “E1” destination is resolved to the routerID for “E”. This
means that the path can be calculated to arrive at the “E” node on any of the following interfaces:
“E1, “E2” or “E3”. While a path that travels from node “A” to node “B” to node “E” is the only path
that actually satisfies the intent of the configuration, any of the following paths could be created by
CSPF under the default operation condition: “A” to “C” to “E”, “A” to “D” to “C” to “E” or “A” to “D” to
“F” to “E”.
FIGURE 8 Calculating a path based on an interface