MPLS Background | Cisco Multiservice Switching Networks

MPLS is defined by the Internet Engineering Task Force (IETF) as a standards-based approach to applying label-swapping technology to large-scale networks. The MPLS Working Group was established in early 1997 and has since defined a large set of working documents that are currently being massaged into standards. Prior to the formation of the MPLS Working Group, a number of vendors had announced and/or built a proprietary version of a label-switching implementation. This widespread interest in label-switching technology initiated the formation of the MPLS Working Group.

The IETF is defining MPLS in response to numerous interrelated problems that need immediate attention. These problems include the following:

Scaling IP networks to meet the growing demands of Internet traffic
Allowing differentiated levels of IP-based services to be provisioned
Merging voice, video, and different data applications onto a single IP network
Scaling VPNs
Improving operational efficiency to cut costs

It is important to note that many service providers are active in the MPLS Working Group. This ensures that MPLS's capabilities will have a direct correlation to customer problems. Many of the issues MPLS seeks to address have already been recognized by a number of equipment manufacturers. In fact, many of these vendors have already developed standards-based solutions that address these problems. You can find more information about this in the IETF MPLS charter at www.ietf.org/html.charters/mpls-charter.html.

It is interesting to analyze the etymology of the MPLS acronym. This chapter covers the label-switching paradigm in great depth. However, what does multiprotocol refer to? This question might seem basic, but the answer goes to the heart of the MPLS concept. Multiprotocol means multiple network layer (Layer 3) protocols such as IPv4 and IPv6 and multiple data link layer (Layer 2) protocols such as Asynchronous Transfer Mode (ATM), Frame Relay, Point-to-Point Protocol (PPP), Ethernet, and Fast Ethernet. For this reason, MPLS does not fit into the OSI model.

Although MPLS, as we described, can conceptually support multiple Layer 2 and Layer 3 protocols, the initial work is focused on the integration of IPv4 with ATM and Frame Relay. Current feature developments include IPv6 and AToM (Any Transport over MPLS), just to name a couple.