Networking

MPLS Misconceptions By: Simon Hill CCNP CCIP

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Executive Summary

As per traditional service provider network, the router examined its IP routing table in order to determine the outgoing interface to the next hop router which is known as 'Process Switching' and is CPU intensive and that has to be performed for every packet. Whilst subsequent router developments, such as 'Fast Switching', helped reduce CPU load, the first packet with a new source and destination address was still process switched. MPLS was welcomed as a means of bridging ATM, Frame Relay and IP, and could run over an existing SP network using a mix of mediums (i.e. leased lines, DSL and Ethernet). MPLS has been incorporated within most Service Provider national networks for clear technical reasons whereas many Service Provider (SP) sales teams make quite different claims for the benefits and advantages of MPLS in order to leverage their products. Most common arguments are that MPLS is resilient, secure and faster than contemporary alternatives. The purpose of this white paper is to explain the real reasons why MPLS has been adopted by so many providers and dispel common misconceptions. It is true that modern MPLS-enabled network that is implemented across a nationwide network of IP switches will not provide any more resiliency than a legacy ATM network with nodes in the same locations whereas the other face of coin is that network architecture beneath MPLS that determines resiliency, not MPLS itself. In terms of security concern, an increasingly popular security topic is human error whereas whilst each MPLS VPN customer is given their own Virtual Routing and Forwarding Table, there is nothing to prevent a provisioning engineer making a configuration error and leaking routes between customers. In crux, MPLS has resolved a number of key service provider requirements.

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