IEEE 802.1ah Provider Backbone Bridge

CE.

IEEE 802.1ah Provider Backbone Bridge (PBB) is a protocol that enables service providers to interconnect geographically separated Local Area Network (LAN) segments as a single bridged domain over an MPLS network. It is also known as MAC-in-MAC encapsulation, as it adds a second MAC header to the original Ethernet frame.

The correct statements about IEEE 802.1ah are:

A. IEEE 802.1ah enables geographically separated LAN segments to be interconnected as a single bridged domain over an MPLS network, knowing all the customer MAC addresses.

This statement is true. IEEE 802.1ah provides a way for service providers to interconnect geographically separated LAN segments as a single bridged domain over an MPLS network, while keeping track of all customer MAC addresses. This is done by adding an additional MAC header to the original Ethernet frame, which includes a service instance identifier (I-SID) that uniquely identifies each customer service.

C. IEEE 802.1ah allows a fewer number of pseudowires in the IP/MPLS core to transport a large number of customer services.

This statement is also true. IEEE 802.1ah allows for the creation of Provider Backbone Bridges (PBBs), which can transport multiple customer services over a single pseudowire. This reduces the number of pseudowires needed in the IP/MPLS core, which in turn reduces the amount of control plane overhead and improves network scalability.

B, D, and E are incorrect statements:

B. IEEE 802.1ah provides the same Ethernet Layer 2 network services as VLAN does, but with greater extensibility and flexibility by overlay scheme over a Layer 3 network.

This statement is incorrect. IEEE 802.1ah does not provide the same Ethernet Layer 2 network services as VLANs. Instead, it provides a way to interconnect geographically separated LAN segments over an MPLS network. It does so by adding an additional MAC header to the original Ethernet frame, which enables greater extensibility and flexibility in building Layer 2 networks over a Layer 3 network.

D. IEEE 802.1ah redefines the flooding and forwarding behavior to avoid loops by not flooding frames received from one member to other members of the same group.

This statement is also incorrect. IEEE 802.1ah does not redefine the flooding and forwarding behavior. Instead, it uses a technique called selective forwarding to prevent loops. With selective forwarding, frames are only forwarded to the ports that have a matching I-SID. This prevents frames from being flooded to other members of the same group, which can cause loops.

E. IEEE 802.1ah provides a means for interconnecting multiple provider bridged to build a large-scale, end-to-end, Layer 2 provider bridged network.

This statement is also incorrect. While IEEE 802.1ah does provide a means for interconnecting multiple Provider Backbone Bridges (PBBs), it does not build a large-scale, end-to-end, Layer 2 provider bridged network. Instead, it enables service providers to interconnect geographically separated LAN segments as a single bridged domain over an MPLS network.