The principle of selecting and establishing MPLS TE SPF Path

In the traffic engineering of MPLS TE, it is divided into the following aspects:

1, the release of information

2, the calculation and establishment of the path

3, traffic forwarding in the tunnel.

So here to understand the path calculation and build, first of all to understand how SPF is working, and then see what is CSPF (constrained SPF). In order to establish the calculation of the path is a good understanding. In detail, why do you want to learn the principle of SPF calculation path?

Because for MPLS te Flow Engineering, the path selection and calculation is very important.

So what is the protocol based on the path calculation? is based on cspf--constrained SPF to carry out the automatic calculation of the path.

But if you want to learn the CSPF,SPF calculation principle is the foundation.

So this document mainly expounds the working principle of SPF calculation, and lays a foundation for the follow-up CSPF.

In OSPF, the SPF Shortest path algorithm is the core algorithm. Take the cost of the link as a priority guideline. For the IGP protocol supported by TE, only OSPF and ISIS two kinds of IGP protocols, and OSPF should be much wider than ISIS, the students who understand OSPF and the number of OSPF are far greater than ISIS, so it is more necessary to have a good review Spf--shorest path Tree's path selection principle.

Here again to review the SPF algorithm, understanding of SPF, CSPF is based on SPF evolved. It is also a great help to understand the CSPF of MPLS.

Router	(The price of a neighbour)
A	(b,5) (c,10)
B	(a,5) (c,3) (d,8)
C	(a,10) (b,3) (d,4)
D	(b,8) (c,4)

The above table is based on the SPF algorithm to obtain the shortest path.

In fact, this is a topology for router a

For each router, it is a topology formed by ternary tables.

{router, distance, next hop}

{Router,distance,nexthop}

What is the path list and tent list:

PATH list:

A list of nodes on the shortest path to the destination. The important thing about the path list is that the list records the shortest path to the destination.

TENT list:

The next hop list may or may not be on the shortest path of the destination address. This list is called the tent list.

Each router runs the following algorithm: (SPF)---principle

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