 Multi-Protocol Label Switching networking
Multi-Protocol Label Switching (MPLS), as the very name indicates, is a versatile network. As in the case of Internet Protocol networks, a special set-up is required for MPLS network. In many ways, MPLS provides the best of both IP and Asynchronous Transfer Mode (ATM) by combining traffic engineering, subnetwork connections and different models of Quality of Service (QoS). Bringing these two domains of IP and ATM connection-oriented telecom network requires an integrated approach. MPLS continues to be popular with global service providers. The benefits of effective MPLS network management can be realised only when the technology is integrated into SP workflows and business processes.
MPLS is a mechanism for forwarding packets in network routers. It was first developed to provide faster packet forwarding than traditional IP routing, though upgrades in router hardware have minimised the importance of speed in packet forwarding. However, the versatility of MPLS has resulted in it becoming the default way for modern networks to attain Quality of Service, next generation VPN services and optical signaling. Conventional IP networks are connectionless. When a packet is received, the router decides the next hop using the destination IP address on the packet together with information from its own forwarding table.
The router’s forwarding tables include information on the network topology. They use an IP routing protocol such as OSPF, IS-IS, BGP, RIP or static configurations, to keep their information synchronised with changes in the network. MPLS also uses IP addresses, v4 or v6, to identify end points, intermediate switches and routers and this makes it compatible with IP and helps easily integrate with conventional networks. However, unlike conventional IP, MPLS flows are connection-oriented and packets are routed along pre-configured Label Switched Paths.
MPLS works by tagging packets with an identifier (a label) to differentiate the Label Switched Paths. When a packet is received, the router uses this label to identify the LSP. It then has a close look at the LSP to decide the best link over which to forward the packet and the label to use on this hop. For each hop, a different label, which is chosen by the router or switch performing the forward operation, is used. This allows the use of very fast and simple forwarding engines as the router can select the label to minimise processing. As MPLS uses only the label to forward packets, it is protocol-independent. That explains the term ‘multi-protocol’ in MPLS. | 
05-01-06, 07:07 AM
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