A routing technique that directs data from one node in a network to another using MPLS labels rather than IP Addresses.
This is done by adding an MPLS header between The Link Layer header and the The Network Layer header. MPLS therefore requires the usage of a compatible router called Label Switched Router (LSR), since ordinary routers will be confused to find a MPLS header where it would expect an IP header.
The routers construct a routing table to advertising to each other their possible destination and the required MPLS label to be redirected to this destination. In this way each MPLS router knows which labels should be redirected where.
Use Cases
Since MPLS allows multiple paths to the same destination, contrary to IP Address, it allows for packets to be routed on paths otherwise not possible. This can be used to override normal IP routing and force some traffic headed toward a given destination along one path.
This possibility of traffic engineering gives rise to several use cases:
- VPN: MPLS can be used to isolate the resources and addresses used by a costumer’s VPN.
- Isolating traffic for each costumer in a multi-tenant cloud.