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.


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


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.

 UNI Type 2.1UNI Type 2.2
  • Backward compatible with UNI Type 1
  • Service OAM
  • Enhanced UNI attributes
  • L2CP handling
  • Backward compatible with UNI Type 1
  • Service OAM
  • Enhanced UNI attributes
  • L2CP handling
  • Link OAM
  • Protection
  • E-LMI
  • Link OAM
  • Protection
  • E-LMI

Frame Delay between UNIs

The Service Provider measures a Frame Delay of 6 ms across its E-Line service.

Related and Further Reading



Attributes | Architecture |