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.
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Gliffy Diagram
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Carrier Ethernet Network - 2 OVCs
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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.
UNI 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 2.1
UNI Type 2.2
Mandatory
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
Optional
Link OAM
Protection
E-LMI
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Example(s)
Frame Delay between UNIs
The Service Provider measures a Frame Delay of 6 ms across its E-Line service.