Multi-Protocol Label Switching. MPLS is a system to improve the performance of a packet switched network, especially for real time traffic such as video and audio over IP.
MPLS directs data from one network router to the next based on short path labels rather than long network addresses, avoiding complex lookups in a routing table.
The labels identify virtual links (paths – called Label Switched Paths) between distant routers (at the edge of the MPLS network). Paths are built by MPLS routers exchanging information using other protocols, commonly LDP (Label Distribution Protocol) or RSVP-TE (Resource Reservation Protocol – Traffic Engineering).
Once paths are set up, each packet that arrives at an MPLS network is given a class (confusingly called the FEC – forwarding equivalence class, NOT to be confused with Forward Error Correction). This class could be based on the source, the destination, or the type of traffic as marked by the DiffServ. All traffic for a particular class will take the same route through the MPLS network.
MPLS can encapsulate packets of various network protocols, and be carried over various network protocols, hence its name “multiprotocol”.
With IP and Ethernet, the MPLS header is added between the IP Header and the Ethernet Header (Which lead some people to call it layer 2.5)
Multiple MPLS headers can be stacked to allow things like Ethernet tunneling over MPLS.
MPLS is not commonly used by broadcasters themselves but is used by Telecoms providers when providing circuits for audio and video over IP. People refer to an MPLS cloud.
See Router
