A Service Distribution Path (SDP) on a Nokia router is a unidirectional tunnel used to forward service traffic between two Provider Edge (PE) routers. To establish a functional, bidirectional service like VPLS between two PEs, a transport path is needed in each direction. Therefore, a minimum of two SDPs must be configured: one from the first PE to the second, and another from the second PE back to the first. A single SDP is capable of carrying traffic for multiple services, so all five VPLS services can utilize this single pair of SDPs.

A. 5-one for each service.

This is incorrect because a single SDP can transport traffic for multiple services. Creating a dedicated SDP for each service is not the minimum requirement.

C. 10-five in each direction.

This is incorrect as it implies creating a dedicated pair of SDPs for each of the five services, which is not necessary for functionality and is not the minimum.

D. None of the above.

This is incorrect because option B accurately states the minimum requirement based on the fundamental architecture of Nokia's service delivery model.

1. Nokia 7450 ESS, 7750 SR, 7950 XRS, and VSR Services Architecture Guide, Release 21.10.R1, Section: Service Distribution Paths (SDPs), Page 101: "An SDP is a unidirectional service tunnel between two 7x50 SRs... To provide a bidirectional service, two SDPs must be provisioned, one for each direction."

2. Nokia 7450 ESS, 7750 SR, 7950 XRS, and VSR Services Architecture Guide, Release 21.10.R1, Section: Service Distribution Paths (SDPs), Page 101: "Once an SDP is created, services can be mapped to the SDP. A single SDP can have multiple services mapped to it." This confirms that the five VPLS services do not require five separate SDPs.

3. Nokia Data Center and Cloud Interconnect (DCI) Solution Guide, Section: Service Distribution Path (SDP): "An SDP is a unidirectional entity that is configured on each participating PE router to provide a logical way to direct service traffic. For a service to be bidirectional between two routers, an SDP must be created from the first router to the second and from the second router to the first." This reinforces the need for a pair of SDPs for bidirectional communication.