An E-pipe is configured with a service MTU of 5000. What value will be derived for the VC-MTU?

On the Nokia 7750 SR platform, the service-mtu defines the maximum size of the entire Layer 2 frame that can be accepted at a Service Access Point (SAP). The VC-MTU (Virtual Circuit MTU) is the value signaled to the remote PE router to indicate the maximum payload size for the pseudowire. For an E-pipe service, the SR OS derives the VC-MTU from the configured service-mtu by subtracting the size of the Ethernet MAC header, which is 14 bytes. This is done for compatibility with other vendor implementations that may consider the MTU to be the L2 payload size. Therefore, the calculation is: 5000 (service-mtu) - 14 = 4986.

A. 4078: This value is significantly smaller and does not follow the standard derivation formula for VC-MTU from the service-mtu.
C. 5014: This would imply adding 14 bytes, which is incorrect. The Ethernet header is part of the service-mtu and is removed for the VC-MTU calculation.
D. 5022: This value is larger than the service-mtu and does not correspond to any standard E-pipe MTU calculation.

Nokia 7750 SR OS Services Guide, Release 21.10.R1, "MTU Configuration Guidelines". In the VLL services section, it explicitly states: "For an Epipe service, the VC-MTU is derived from the service-MTU. The derivation is VC-MTU = service-MTU - 14 bytes (14 bytes is the size of the Ethernet header)."

Nokia 4A0-104 Course Material, Module 3: Virtual Private Wire Service (VPWS). The section on E-pipe configuration and verification details the relationship between service-mtu and the derived vc-mtu.