Service Destination Points (SDPs)

Topics in this section include:

An SDP identifies the endpoint of a logical unidirectional service tunnel. The service tunnel provides a path from one service router to another.

In more general terms, SDP refers to the service tunnel itself. The SDP terminates at the far-end router, which is responsible for directing the flow of packets to the correct service egress SAPs on that device.

Note: In this document and in command line interface (CLI) usage, SDP is defined as Service Destination Point. However, it is not uncommon to find the term SDP defined in several different ways, as in the following list. All variations of SDP have the same meaning:

  • Service Destination Point

  • Service Distribution Point

  • Service Destination Path

  • Service Distribution Path

  • Service Delivery Path

When an SDP is bound to a service, the service is referred to as a distributed service. 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 that binds the service to the service tunnel. Multiple SDPs to different far-end nodes are bound to a service to provide transport for SAPs to other nodes participating in that service.

When configured, an SDP has the following characteristics.

  • An SDP is locally unique to a participating service router. The same SDP ID can appear on other service routers.

  • An SDP uses either the system IP address or the cellular PDN interface IP address of the far-end edge router to locate its destination.

  • An SDP is not specific to any one service or to any type of service. When 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 bound to an SDP use the same SDP (transport) encapsulation type defined for the SDP (for example, GRE-MPLS).

  • An SDP is a service entity used for service management. Even though the SDP configuration and the services carried within it 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 tunnel from a local device to the far-end device (router) requires a return SDP tunnel from the far end back to the local device. Each device must have an SDP defined for every remote router to which it wants to provide service. The SDP must be created before a distributed service can be configured.

  • An SDP can be used to provide PW redundancy, where up to four spoke SDPs can be assigned to a service endpoint that acts as the managing entity to ensure service connection. For information about pseudowire redundancy, see the 7450 ESS, 7750 SR, 7950 XRS, and VSR Layer 2 Services and EVPN Guide, "Pseudo-wire redundancy".