Multi Protocol Label Switching

Introduction

Multi Protocol Label Switching or MPLS is a generic Layer 2 packet switching protocol. It uses a mechanism that allows setting MPLS labels to data packets in order to indicate their destination. An MPLS label improves the efficiency of an IP network by helping the routers to steer a packet to its final destination over a network.

IETF (Internet Engineering Task Force) has developed MPLS to help in clearing up clogged data networks since the routers could simply pass on a data packet without determining a route for it. In this way, the MPLS mechanism allows better management of data flow coupled with significant increase in efficiency and accuracy of data packet delivery over a network.

MPLS adopted a number of technically sound ideas from the ATM protocol. MPLS can be seamlessly implemented over both the IPv4 as well as the IPv6 networks. MPLS also helps in the integration of the data link layer information such as the bandwidth, latency and utilization parameters with the network layer. Since MPLS attempts to integrate layer 2 with the layer 3, it is often referred to as a "Layer 2.5 protocol". The MPLS mechanism is predominantly used over packet-switched data networks despite the fact that it was designed to provide unified data carrying services to both the circuit switching as well as packet switching clients through a datagram service model. The Multi Protocol Label Switching (MPLS) can be used to carry a wide variety of traffic including the IP packets, Asynchronous Transfer Mode (ATM), Synchronous Optical Networking (SONET) and Ethernet frames.

Internet Protocol (IP)

The Internet Protocol (IP) is used for data communications over a packet switched network. IP is a network layer protocol in the TCP/IP protocol suite. IP is a connectionless protocol encapsulated in the data link layer protocol that is best suited for transmission of data packets over a network. IP is considered a lower layer protocol as it is involved in the process of data encapsulation in packets or datagrams. Moreover, it is closer to the physical layer in the TCP/IP protocol suite and can be used over a heterogeneous network owing to the abstraction provided by encapsulation. IP is not a very reliable service as it employs the best effort delivery mechanism whereby the actual delivery of the data packets is not assured. Instances of data corruption, loss, duplication, discarded or out of order data packets are not rare and need to be factored in through proper error detection and resolution techniques.

Frame Relay

The network providers commonly use frame relay to encapsulate voice and data traffic for transmission between Local Area Networks (LAN) and between end-points in a Wide Area Network (WAN) in the form of a continuous relay of frames. It is a data transmission technique that aims at sending the digital information in a fast and cost effective manner while making an efficient use of the existing physical network resources. The name Frame Relay is derived from the fact that the mechanism uses variable sized data units called frames for transmission of data over a network. In the Frame Relay mechanism, error correction is undertaken at the end-points. This tends to speed up the overall process of data transmission. The 'permanent virtual circuit' offered by Frame Relay attempts to integrate the advantages of a packet switching network with the feel of a dedicated leased line. However, Frame Relay networks often suffer from bandwidth overbooking by the telecom operators leading to frequent network congestion. MPLS is expected to eventually replace the Frame Relay technology.

Asynchronous Transfer Mode (ATM)

ATM is a connection oriented cell relay data link and network layer protocol that is used for data communications over packet switched networks. It encodes data packets into small fixed sized cells consisting of 53 bytes each that comprises of 48 bytes of data and 5 bytes of header information. Unlike other technologies such as Internet Protocol (IP) or Ethernet that are based on the packet-switched networks, ATM is a connection oriented technology that establishes a virtual connection between two endpoints before commencing the actual exchange of data between them. ATM is commonly used in the Wide Area Network (WAN) cores and Asynchronous Digital Subscriber Line (ADSL) broadband implementations. The inherent complexity of the protocol prevents it from being widely accepted for use over the Local Area Networks (LAN). MPLS borrows heavily from ATM and is complementary to the IP thereby making it the preferred choice for data communications over IP networks.

Ethernet

The term Ethernet is derived from the word Ether that was earlier supposed to permeate all physical space. It is a generic term used to denote a family of computer networking technologies that are used over the Local Area Networks (LAN). These are frame-based technologies that define wiring and signaling standards for the physical layer through Media Access Control (MAC) or Data link Layer. Ethernet is also denoted as IEEE 802.3 outlining the standard for connecting various nodes to a communications network. Ethernet has been in use since the 1990s and has replaced several competing LAN standards such as FDDI, token ring and ARCNET. Ethernet has become a de facto standard for data communications over a Local Area Network (LAN) to the extent that majority of the PCs come with preinstalled Ethernet cards for network communications.