MPLS Architecture
- Labels are bound to routes in the routing table
- MPLS architecture components:
- Control plane
- Forwarding plane
- CONTROL:
- Responsible for
- binding a label to network routes
- for this we need routing table
- to get routing table we need a routing protocol
- and distribute those bindings among other MPLS enabled routers
- for this 2 protocols are used
- Tag Distribution Protocol(TDP):
- Cisco proprietary protocol
- used to bind tags to network routes in the routing table.
- FORWARDING:
- The routing table is built in the control plane & cached in forwarding plane.
- Forward Information Base is built by CEF.
- FIB is a cached version of the ip routing table that eliminates the need for a lookup of routing table.
- Router compares the packet's destination ip address to the CEF FIB, ignore the ip routing table.
- CEF optimizes the organization of FIB, so that router easily find the correct FIB entry,
- resulting in a smaller forwarding delay & high volume of packets per second through a router.
- For each packet, the router finds the matching FIB entry,
- then finds the adjacency table entry referenced by the matching FIB entry,
- and forward the packet
