A Service Distribution Point (SDP) acts as a logical way to direct traffic from one 7450 ESS or 7750 SR to another 7450 ESS or 7750 SR through a unidirectional (one-way) service tunnel. The SDP terminates at the far-end router which directs packets to the correct service egress SAPs on that device. A distributed service consists of a configuration with at least one SAP on a local node, one SAP on a remote node, and an SDP binding the service to the service tunnel.
An SDP has the following characteristics:
An SDP is locally unique to a participating 7450 ESS or 7750 SR. The same SDP ID can appear on other 7450 ESS or 7750 SR OS.
An SDP uses the system IP address to identify the far-end 7450 ESS or 7750 SR edge router.
An SDP is not specific to any one service or any type of service. After an SDP is created, services are bound to the SDP. An SDP can also have more than one service type associated with it.
All services mapped to an SDP use the same transport encapsulation type defined for the SDP (either GRE or MPLS).
An SDP is a management entity. Even though the SDP configuration and the services carried within are independent, they are related objects. Operations on the SDP affect all the services associated with the SDP. For example, the operational and administrative state of an SDP controls the state of services bound to the SDP.
An SDP from the local device to a far-end 7450 ESS or 7750 SR requires a return path SDP from the far-end router back to the local router. Each device must have an SDP defined for every remote router to which it wants to provide service. SDPs must be created first, before a distributed service can be configured.