The list of network transport options available over the years to enterprises with significant bandwidth and security requirements is long: private lines, ATM, SONET, Frame Relay, and even IP-VPN. And let’s not forget X.25! At first, each one was the ‘must-have’, until the next cheaper, faster, and smarter platform replaced it, leaving a dusty pile of long-term contracts, obsolete equipment, and sunk costs behind. Legacy networks are just that – too expensive to abandon and too integral a part of the network architecture to work around. Happily, Multiprotocol Label Switching integrates with legacy networks and multiple protocols in a very elegant way. MPLS is not a transport or service, but rather a protocol-neutral labeling system that mixes all kinds of packet-switched data on the same network.
MPLS makes multi-layered networks running different kinds of packet traffic with various levels of packet overhead requirements work. MPLS can accommodate IP packets, which have no overhead, alongside native ATM, SONET, and Ethernet frames which have high overhead requirements. In a MPLS network, edge and inner-network routers read low-overhead labels that require little ‘thinking’ to route onward. MPLS-protocol packets are assigned an outer label, and both the length and contents of the packet are immaterial. Only the label gets read, so the limited number of paths available allows for traffic prioritization, Classes of Services, and other sophisticated services. Once a packet is covered by an MPLS ‘sheep’s skin’, any ‘wolf’ packet can travel an end-to-end circuit across any type of transport medium.
MPLS’ flexibility and scalability is an obvious solution for large enterprise networks running several types of packet traffic. The corporate WAN requiring performance guarantees and Quality of Service can’t rely on an IP-VPN network over the public Internet for reliable business-class transport. Applications like VoIP, real-time data traffic, and video conferencing require both security and performance, but today’s competitive business doesn’t want to pay ATM or frame relay prices for them. MPLS implemented over a newer, more cost-effective, and easily scalable transport such as Ethernet offers the same security and privacy as yesterday’s legacy technologies. It’s simple to replace ATM or frame relay with MPLS over Ethernet, without an expensive network redesign or complicated LAN and WAN re-provisioning and maintenance.