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The User Network Interface (UNI) is the physical demarcation point between the responsibility of the Subscriber (UNI-C, the Customer Edge or CE) and the responsibility of the Service Provider (UNI-N)

The network that provides the Ethernet services is called the Carrier Ethernet Network (CEN). The basic service model as described in MEF 10.3 is shown in the picture below.

UNI-C

The UNI-C provides the Customer Edge side functions which can be implemented on a switch or a router that connects to the CEN. The UNI-C is responsible for:

• Formatting the frames in ETH format
• C-tagging the frames per the service definition
• Traffic management functions such as shaping
• OAM functions such as link OAM and the Subscriber MEG for service OAM

UNI-N

The UNI-N is the SP's side of the UNI. It can be implemented in a single network element or can be distributed between several network elements within the CEN. UNI-N is responsible for:

• Exchange of data frames with UNI-C
• Mapping service frames to and from the EVCs
• Enforcing ingress and bandwidth profiles and color marking
• OAM functions
• Optional CE-VLAN ID manipulation

UNI Type 1 and UNI Type 2

The MEF defines two UNI types

UNI Type 1

UNI Type 1 is defined by MEF 13. This is a basic UNI with manual configuration of UNI-N and UNI-C.

UN I Type 1 is further divided into UNI Type 1.1 and UNI Type 1.2:

• Type 1.1: Non-multiplexed UNI for services such as EPL
• Type 1.2: Multiplexed UNI for services such as EVPL

UNI Type 2

UNI Type 2 is defined by MEF 20. It presents an automated implementation model allowing UNI-C to retrieve EVC status and configuration information from UNI-N. It supports enhanced UNI attributes and additional fault management and protection functionality.

  UNI type 2 is further divided into UNI Type 2.1 and UNI Type 2.2.