Implementation
Figure 4-8 illustrates the MPLS TE framework.
- IGP-based information advertisement for TE information collection
- Path calculation using the collected information
- Path setup through signaling packet exchange between upstream and downstream nodes
- Traffic forwarding over an established MPLS TE tunnel
Table 4-1 describes the four functions.
No. |
Function |
Description |
|---|---|---|
1 |
Collects network load information in addition to routing information. MPLS TE extends an IGP to advertise TE information, including the maximum link bandwidth, maximum reservable bandwidth, and reserved bandwidth. Every node collects TE information about all links in a local area and generates a traffic engineering database (TEDB). |
|
2 |
Uses the Constrained Shortest Path First (CSPF) algorithm and data in the TEDB to calculate a path that satisfies specific constraints. CSPF evolves from the Shortest Path First (SPF) algorithm. It excludes nodes and links that do not satisfy specific constraints and uses the SPF algorithm to calculate a path. |
|
3 |
Nodes on a network use the Resource Reservation Protocol (RSVP) TE signaling protocol to set up CR-LSP tunnels. RSVP-TE messages carry constraints for a CR-LSP, such as the bandwidth and explicit path. There is no need to manually configure each hop along a dynamic CR-LSP. Dynamic CR-LSP setup applies to large-scale networks. RSVP authentication can be used to enhance security and reliability of CR-LSPs. |
|
4 |
Directs traffic to an MPLS TE tunnel and forwards traffic over the MPLS TE tunnel. The first three functions set up an MPLS TE tunnel, and the traffic forwarding function directs traffic arriving at a node to the MPLS-TE tunnel. |
To deploy MPLS TE on a network, you must configure link and tunnel attributes. Then MPLS TE sets up tunnels automatically. After a tunnel is set up, traffic is directed to the tunnel for forwarding.