The working principle of MPLS TE RSVP

Before the document starts, I think it is necessary to know the signaling protocol for MPLS Te.

Rsvp-te

The agreement itself is relatively mature and has been applied in scale.

--based on the soft state, the scalability is relatively poor.

Cd-ldp

Protocol relatively new, immature, basically no application.

--based on hard state, extensibility is better.

Ultimately, however, the market decides that RSVP is accounted for first, so when it comes to MPLS TE, most vendors support Rsvp-te. Few vendors support the CD-LDP protocol. It seems that Rsvp-te is already a standard in the industry. So learning Mpls te is necessary to understand the operation of RSVP.

The relevant knowledge points of RSVP have the following points:

RSVP Basics

RSVP grouping

RSVP operation

RSVP in the real world.

The RSVP protocol type is 46, although it is possible to encapsulate RSVP in UDP, but MPLS Te never encapsulates RSVP in UDP.

What does RSVP do for me?

We all know that there are several ways to label distribution:

MPLS LDP/TDP, which is the standard protocol used to distribute MPLS tags.

RSVP, for label distribution in Mpls Te. Has no intersection with LDP work.

Another is BGP's label distribution for VRF routing.

RSVP is not a routing protocol, and any routing decision is made by IGP and CSPF. (If CSPF is still in doubt, please refer to http://361531.blog.51cto.com/351531/657115, MPLS CSPF working principle and related experiments, RSVP's only job is to advertise and maintain the reserved resources in the network. In MPLS te, RSVP retains the bandwidth in the control plane layer, so there is no control over the forwarding plane of the traffic.

There are three basic features of RSVP:

The establishment and maintenance of the path

Path removal

Error notification.

The main message types for RSVP are as follows: A total of 7 categories are the main applications.

Regarding the establishment of RSVP signaling, simply put, in 2 steps, the original node sends an RSVP path message to the destination router, and then the destination router returns a RESV to the original node after it receives the path request. So, a te tunnel was built successfully.