Part 4: MPLS Forwarding Operations (LDP Vs RSVP)

MPLS Forwarding Operations (LDP Vs RSVP)

It is very important to understand LDP and RSVP when you are talking about MPLS forwarding operations. Both LDP and RSVP has a key role in MPLS environment to packet using labels and switches from one PE router (ingress) to another PE router (egress).

LDP(Label Distribution Protocol):
LDP stands for Label Distribution Protocol and LDP is the protocol used for exchanging the Labels in the MPLS network and is one of the backbone for the MPLS networks.

Label distribution protocols create and maintain the label-to-forwarding equivalence class (FEC) bindings along the label switched path (LSP) from MPLS ingress label-switching router (LSR) to MPLS egress LSR.

LDP uses several types of messages in order to establish the session, exchange of label mappings, and to report errors. All messages have the same structure and encoding as Type/Length/Value (TLV):Discovery messages, Session messages, Advertisement messages and Notification messages.

To understand depth on LDP protocol, please go through the below detailed discussion and the configurations of LDP

MPLS LDP in Depth

RSVP (Resource Reservation Protocol):
RSVP stands for Resource Reservation Protocol. RSVP is used when we are going to use MPLS traffic engineering and Traffic engineering RSVP is a separate protocol at the IP level. 

It uses IP datagrams (or UDP at the margins of the network) to communicate between LSR peers. It does not require the maintenance of TCP sessions, but as a consequence of this it must handle the loss of control messages 

To understand depth on RSVP protocol, please go through the below detailed discussion on RSVP as below

MPLS RSVP Traffic Engineering

Difference between LDP and RSVP
Let's talk about the difference between LDP and RSVP protocols and what they use while forwarding the traffic from one source to destination within the MPLS network.

Fig 1.2- LDP Vs RSVP