The working principle of MPLS CSPF and related experiments

Key knowledge points in this document:

Principle of CSPF Route selection

Parameters that have an effect on the CSPF path selection

How does the MPLS te display path be established?

cspf--constrained SPF (shorest path tree). Is the core of Mpls te path selection, as we already know, the functions of Mpls te are:

1, Information Release 2, path calculation and build 3, traffic forwarding in the tunnel.

After understanding the working principle of CSPF, in fact, it is the calculation of the path and the establishment of the original rational understanding, for later MPLS TE network planning and troubleshooting have some help.

The document will slowly explain how CSPF works after you have learned about the path-selection method of SPF.

We have learned about SPF ternary, {purpose, cost, next hop}.

In CSPF (constrained SPF), three additional elements are added.

Bandwidth---Bandwidth

Link Properties---Attribute-falgs

Management Weights---administrative-weight.

In CSPF, like SPF, there are path list tables and tent lists, but there is also a need to add available bandwidth.

The last listed property formats are:

{link, price, next hop, available bandwidth}

{Link,cost,next hop,availbable Bandwidth}

Here is a topology map, like the SPF topology, but with the reserved bandwidth of te.

In fact, the calculation method and SPF almost, but the reserved bandwidth added in, the following is the router a CSPF calculation results.

Finally, a top on a will draw a shortest path to the TE for each router.