RSVP-TE(Resource Reservation Protocol-Traffic Engineering) is the enhanced RSVP for MPLS. RSVP-TE is not a real routing protocol, but it works with routing protocols.
For RSVP-TE, bidirectional flow is required. To provide this, there must be two RSVP sessions. Because RSVP-TE is unidirectional.
RSVP-TE brings some benefits to MPLS. These benefits are:
– Ability to define LSP paths, path choice by administrator.
– Advanced cost calculation, not restricted to IGP cost values.
– Rich set of traffic protection (secondary paths and fast reroute).
– Ability to make resource reservation functionality.
As we talked about before in LDP articles, there are also some main characteristics for RSVP-TE. Some of these characteristics are different than LDP. What are these characteristics? Let’s check:
– Downstream on demand : LSPs signalled when requested. ( This was unsolicited downstream in LDP, which send labels without any requests).
– Ordered control : Label distribution process follows a hierarchical order (Same as LDP).
– Conservative label retention : Labels are cleared if not needed. ( This was liberal label retention in LDP, which stores all the labels).