Large service providers today operate multiple service specific networks to provide their customers with the full range of services that they require. In order to reduce capital and operational expenditure, service providers are seeking to converge their multiple networks where possible onto common infrastructures. The chosen convergence technologies must support existing services but also be flexible enough to support future services to allow service providers to stop deploying ‘stovepipes’. A flexible converged infrastructure reduces the number of network elements that must be managed and maintained, whilst at the same time enabling the service provider to increase revenue generation by offering new services. On the other hand, in deploying new services large services providers must protect the revenues provided by their existing services and protect their existing infrastructure investment.

The growth of the Internet has made IP the most widely used Layer 3 protocol, which makes it an attractive convergence technology. However, as IP is a connectionless-based protocol, it is not suitable for all types of services. Business customers require well-defined QoS and reliability guarantees that can only be delivered using connection-orientated protocols. This is where MPLS steps into the network convergence arena. MPLS is a connection-orientated protocol and as such has the ability to support bandwidth reservation and service guarantees on a per connection basis. This presentation introduces two alternative approaches to using MPLS as a network convergence technology. The first approach is to use network interworking to support all service types using a converged IP/MPLS infrastructure. These services include SDH/SONET, TDM, Ethernet, ATM and Frame Relay. To support all service types over an IP/MPLS network requires certain issues to be addressed including packet re-ordering, timing, and more importantly OAM. As only networking interworking is supported, the service type must be the same at each end of the IP/MPLS network.

An alternative approach breaks the convergence problem space up into three networking modes. The three modes are connectionless (e.g. IP), connection-orientated packet-switching (e.g. MPLS, ATM, Frame Relay), and connection-orientated circuit switching (e.g. SDH, SONET). Operators require all three modes to deliver existing and future services. IP is the obvious choice for convergence in the connectionless case, and SDH/SONET are well suited for the connection-orientated circuit-switching case (moving to optical switching in the future). MPLS has the potential to take on the convergence role in the connection-orientated packet-switching case; however before it can take on this role certain conditions must be met. The primary conditions being that MPLS must have its own separate address space, support service interworking and provide adequate OAM functionality.

This presentation presents a balanced view of the alternative MPLS convergence approaches by investigating the issues and benefits associated with each.