Packet Forwarding with Multiprotocol Label Switching

Authors: R.N.Pise, S.A.Kulkarni, R.V.Pawar

Abstract:

MultiProtocol Label Switching (MPLS) is an emerging technology that aims to address many of the existing issues associated with packet forwarding in today-s Internetworking environment. It provides a method of forwarding packets at a high rate of speed by combining the speed and performance of Layer 2 with the scalability and IP intelligence of Layer 3. In a traditional IP (Internet Protocol) routing network, a router analyzes the destination IP address contained in the packet header. The router independently determines the next hop for the packet using the destination IP address and the interior gateway protocol. This process is repeated at each hop to deliver the packet to its final destination. In contrast, in the MPLS forwarding paradigm routers on the edge of the network (label edge routers) attach labels to packets based on the forwarding Equivalence class (FEC). Packets are then forwarded through the MPLS domain, based on their associated FECs , through swapping the labels by routers in the core of the network called label switch routers. The act of simply swapping the label instead of referencing the IP header of the packet in the routing table at each hop provides a more efficient manner of forwarding packets, which in turn allows the opportunity for traffic to be forwarded at tremendous speeds and to have granular control over the path taken by a packet. This paper deals with the process of MPLS forwarding mechanism, implementation of MPLS datapath , and test results showing the performance comparison of MPLS and IP routing. The discussion will focus primarily on MPLS IP packet networks – by far the most common application of MPLS today.

Keywords: Forwarding equivalence class, incoming label map, label, next hop label forwarding entry.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1073467

References:

[1] RFC 3031- Multiprotocol Label Switching Architecture.
[2] RFC 3032 - MPLS Label Stack Encoding.
[3] MPLS and VPN Architectures -- CCIP Edition Pearson education 2002, Delhi, India.
[4] TCP/IP Illustrated -- Richard Stevens Volume II Pearson Education 2001, Delhi, India.
[5] Computer Networks (Fourth edition) -- Andrew S. Tanenbaum. Prentice Hall India, 2002 Delhi, India.
[6] Routing TCP/IP - Jeff Doyle CCIE #1919 Volume I Techmedia, 2002 Delhi India.