MPLS-Enabled Applications: Emerging Developments and New Technologies

5.2. THE BUSINESS DRIVERS

The benefits of traffic engineering were discussed in the Traffic Engineering chapter (Chapter 2). Providers use traffic-engineered paths for optimization of network resources, support of services with QoS guarantees, fast reroute and the measurement of the aggregated traffic flow between two points in the network. To achieve these functions in large networks with multiple IGP areas, the LSPs used for traffic engineering need to cross area boundaries (interarea LSPs).

Interdomain LSPs^[] are not limited to traffic engineering; they are also pivotal to the deployment of services spanning across different geographical locations. These can be services requiring assured bandwidth, such as connection of voice gateways, or they may be applications that rely on the existence of an MPLS transport tunnel, such as pseu-dowires or BGP/MPLS Layer 3 VPNs. When the service spans several IGP areas, the LSP is interarea; when it spans different ASs, the LSP is inter-AS.

^[] Recall that 'domain' is used in this chapter to denote either an area or an AS.

Inter-AS LSPs exist both within the same provider and across different providers. Multiple ASs can be present within a single service provider's network, e.g. following the acquisition of another provider's network in a different geographical location. The separate ASs are maintained for reasons ranging from administrative authority to the desire to maintain routing protocol isolation between geographical domains and prevent ...