A service is a globally unique entity that refers to a type of connectivity service for either Internet or VPN connectivity. Each service is uniquely identified by a service ID and an optional service within a service area. The 7210 SAS-series service model uses logical service entities to construct a service. In the service model, logical service entities provide a uniform, service-centric configuration, management, and billing model for service provisioning.
In the 7210 SAS-series routers, services can provide Layer 2/bridged service between a service access point (SAP) and another service access point (a SAP is where traffic enters and exits the service) on the same (local) router or another router (distributed). A distributed service spans more than one router.
Distributed services use service distribution points (SDPs) to direct traffic through a service tunnel to another 7210 SAS router, SR router, or other router that supports MPLS. SDPs are created on each participating router, specifying the origination address (the router participating in the service communication) and the destination address of another router. SDPs are then bound to a specific customer service. Without the binding process, the far-end router is not able to participate in the service (there is no service without associating an SDP with the service).