MPLS: Delivering Next-Generation Networking Services

Randy Zhang

Many business WAN services are currently provided by leased lines, frame relay, or ATM services. These services are popular because they provide a high level of quality guarantees and privacy, albeit at a high cost. For example, a frame relay-based network provides quality in terms of Committed Information Rate (CIR) and privacy in terms of permanent virtual circuits (PVC). Besides the high cost, these layer 2 technologies are commonly provisioned point-to-point, presenting a scalability problem. Success of the Web technology and the industry's convergence to a single protocol, IP, presents another alternative -- WAN services through the public IP network, the Internet. Because IP exists at layer 3 and is connectionless, it provides an any-to-any connectivity, with unmatched scalability by layer 2 technologies. However, IP services were not designed to be reliable and predictable. The majority of IP traffic is still delivered as a best-effort with little or no quality guarantees, yet such quality may become increasingly critical for many applications. Another increasingly common concern is data privacy and security, yet the current IP-level VPN solution involves building encryption tunnels. These tunnels, which are similar to WAN circuits, present a scalability problem.

There are two major forces pushing for new IP services: new applications and expanded infrastructure.