How does ERS use the VLAN tag?

The correct answer is C. as a connection identifier to indicate destination. ERS (Ethernet Relay Service) is a point-to-multipoint Layer 2 service in which a single hub site connects to multiple spoke sites. In ERS the VLAN tag carried in the customer Ethernet frame is repurposed as a connection identifier - the provider maps each VLAN tag to a specific…

Advanced WAN Services

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Ato provide service internetworking
Bto support transparency for Layer 2 frames
Cas a connection identifier to indicate destination
Das a mapping to the DLCI in service internetworking
Eto provide a trunk by which all VLANs can navigate from one site to one or multiple sites

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A
3% (1)
B
8% (3)
C
87% (34)
D
3% (1)

Explanation

ERS (Ethernet Relay Service) is a point-to-multipoint Layer 2 service in which a single hub site connects to multiple spoke sites. In ERS the VLAN tag carried in the customer Ethernet frame is repurposed as a connection identifier - the provider maps each VLAN tag to a specific destination spoke, effectively using it to route or steer the frame to the correct remote endpoint rather than for traditional VLAN membership. This is distinct from port-based Ethernet Line (E-Line) service and from service interworking (which maps VLAN tags to DLCIs), and it does not simply provide trunk transparency or broadcast replication across all VLANs.

Topics

#ERS#VLAN tag#Ethernet relay service#connection identifier

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