MEF Glossary

MEF Glossary

This is a summary of the terms used in the MEF specifications. Some abbreviations have several meanings dependent upon context. For example CE can mean Carrier Ethernet, Circuit Emulation, Customer Edge, or Customer Equipment. Others may have slight variation depending on the specification. Therefore, referral to individual context and the individual glossaries in each specification is required. Some terms reference their definition in ITU, IEEE and IETF specifications.

The Glossary contains commonly used terms and abbreviations, the first MEF Specification that a term is defined and a list of Specifications where the terms are used. The glossary covers specifications up to MEF 31.There are many representational diagrams of the UNI/ENNI etc., in the specifications. This diagram is considered definitive.

Term	Description
Carrier Ethernet	Carrier Ethernet is a ubiquitous, standardized, carrier-class Service and Network defined by five attributes that distinguish Carrier Ethernet from familiar LAN based Ethernet. These are:
Carrier Ethernet	- Standardized Services, Scalability Reliability, Quality of Service, Service Management
Term	MEF Ethernet Service Types Defined in MEF 6.1
E-Line	An MEF Ethernet Line (E-Line) Service Type is any Ethernet service that is based on a Point-to-Point Ethernet Virtual Connection (EVC)
E-LAN	An MEF Ethernet LAN (E-LAN) Service Type is any Ethernet service that is based on a Multipoint-to-Multipoint EVC
E-Tree	An MEF Ethernet LAN (E-Tree) Service Type is any Ethernet service that is based on a Rooted-Multipoint-to-Multipoint EVC
Term	MEF Ethernet Services Defined in MEF 6.1
EPL Service	Ethernet Private Line Service
EVPL Service	Ethernet Virtual Private Line Service
EP-LAN Service	Ethernet Private LAN Service
EVP-LAN Service	Ethernet Virtual Private LAN Service
EP-Tree Service	Ethernet Private Tree Service
EVP-Tree Service	Ethernet Virtual Private Tree Service
Commentary on the Use of Terminology
The terms, Operator, Service Provider, etc. are subjective within the industry and have evolved since the first MEF Specifications were written. The MEF uses the term Service Provider as a generic term for organizations such as Carriers, MSOs, telcos cable operators, PTTs, etc. Service Providers may provide UNI-UNI, ENNI-UNI or ENNI to ENNI services in all combination of wholesale and retail business. MEF Specifications generally use the term Operator for consistency between the documents but these may be substituted for different terms as appropriate. Terms such as VUNI Provider, Access Provider, Mobile Operator and Backhaul Provider are used to indicate the services that are being offered by Service Providers. This does not imply that these are the only services being offered by that provider.
MEN, CEN	Within the context of the MEF specifications, Metro Ethernet and Carrier Ethernet or MENs and CENs can be used interchangeably. For consistency with early work, the MEF specifications use the term MEN that originated when Carrier Ethernet only addressed Metro Area optical fiber networks. MEF marketing documents and presentations generally referred to Carrier Ethernet Networks.

Definitions in the Specifications
Term	Description	First Appears in	Referred to in
AAL1	ATM Adaptation Layer 1	MEF 8	8, 11
Access Link	A link that represents connectivity to External Reference Points of the MEN	MEF 2	2
ADM	Add Drop Multiplexer	MEF 2	2
AIS	Alarm Indication Signal	MEF 3	3, 8, 11, 30
Alarm Status	Indicates the occurrence of an abnormal condition. Values for alarm status include: critical, major, minor, indeterminate, warning, pending, and cleared	MEF 15	15
All to One Bundling	A UNI attribute in which all CE-VLAN IDs are associated with a single EVC	MEF 6.1	6.1, 19, 7, 9, 10.2, 14, 15, 29
ALNP	Aggregated Line and Node Protection	MEF 2	2
ANSI	American National Standards Institute	MEF 3	3, 8, 11
APCP	Application Protection Constraint Policy	MEF 2	2
APP	Application Layer, Application Services Layer	MEF 4	12, 17, 4
APS	Automatic Protection Switch, Automatic Protection Switching	MEF 2	2, 3
ATM	Asynchronous Transfer Mode	MEF 4	4, 8, 11
Availability Performance	A measure of the percentage of time that a service is useable.	MEF 10.2	10.2
Bandwidth Profile	A characterization of ingress Service Frame arrival times and lengths at a reference point and a specification of the disposition of each Service Frame based on its level of compliance with the Bandwidth Profile. In this document the reference point is the UNI	MEF 6.1	19, 6.1, 10, 14, 15, 7, 9, 27, 29
Bandwidth profile per CoS ID	A UNI service attribute	MEF 6.1	6.1
Bandwidth profile per EVC	A UNI service attribute	MEF 6.1	6.1
Bandwidth profile per ingress UNI	A UNI service attribute	MEF 6.1	6.1
BBER	Background Block Error Ratio	MEF 3	3
BER	Bit Error Rate, Bit Error Ratio	MEF 2	2, 3
BLSR	Bi-directional Line Switched Ring, Bi-directional Line Switching Redundancy	MEF 2	3, 2
BPDU	Bridge Protocol Data Unit	MEF 2	2
Broadcast Service Frame	A Service Frame that has a broadcast destination MAC address.	MEF 7	7, 15, 19, 10.2, 14
Broadcast Service Frame Delivery	An EVC service attribute	MEF 6.1	6.1
BSS	Business Support System	MEF 30	30
Bundling	A UNI attribute in which more than one CE-VLAN ID can be associated with an EVC	MEF 6.1	19, 10, 9, 10.2, 14, 7, 15, 6.1, 29
BWP	Bandwidth Profile	MEF 12	12
CAS	Channel Associated Signaling	MEF 3	3, 8, 11
CBS	Committed Burst Size	MEF 6.1	6.1, 7, 8, 10.2, 11, 13, 14, 15, 19, 27, 29
CCM	Continuity Check Message	MEF 30	30
CCS	Common Channel Signaling	MEF 3	3, 8, 11
CE	Customer Equipment, Carrier Ethernet, Customer Edge, Circuit Emulation	MEF 2	2, 3, 4, 6.1, 7, 8, 9, 10.2, 11, 12, 14, 15, 16, 19, 26, 27, 29
CES	Circuit Emulation Services	MEF 2	2, 7, 15, 3, 8, 11
CESoETH	Circuit Emulation Services over Ethernet	MEF 8	8, 11
CE-VLAN CoS	Customer Edge VLAN CoS. The user_priority bits in the IEEE 802.1Q Tag in a Service Frame that is either tagged or priority tagged.	MEF 6.1	6.1, 10.2, 14, 19, 7, 15, 27, 29
CE-VLAN CoS Preservation	An EVC service attribute	MEF 6.1	6.1
CE-VLAN ID	The identifier derivable from the content of a Service Frame that allows the Service Frame to be associated with an EVC at the UNI. Customer Edge VLAN ID. The identity of the VLANs on the Ethernet port of the customer equipment that is attached to the UNI.	MEF 6.1	13, 10.2, 14, 19, 15, 6.1, 7, 9, 27, 29
CE-VLAN ID / EVC Map	A UNI service attribute	MEF 6.1	6.1
CE-VLAN ID Preservation	An EVC attribute in which the CE-VLAN ID of an egress Service Frame is identical in value to the CE-VLAN ID of the corresponding ingress Service Frame	MEF 6.1	19, 6.1, 7, 10.2, 14, 15, 29
CE-VLAN ID/EVC Map	An association of CE-VLAN IDs and EVCs at a UNI.	MEF 7	7, 15, 19, 9. 10.2, 14, 27
CE-VLAN Tag	Customer Edge VLAN Tag. The IEEE 802.1Q Tag in a tagged Service Frame.	MEF 6.1	6.1, 7, 9, 10.2, 14, 19, 15, 27, 29
CE-VLAN tag preservation	A set of EVC service attributes	MEF 6.1	6.1
CF	Coupling Flag	MEF 6.1	6.1, 8, 10.2, 11, 14, 19, 15, 29
CFI	Canonical Format Indicator	MEF 12	12
CFM	Connectivity Fault Management	MEF 30	30
Child Document	A MEF Specification that uses the Ethernet Service Constructs model (defined in this specification) to specify a particular type of EI or ESN	MEF 29	29
CI	Characteristic Information	MEF 4	4, 12
CIR	Committed Information Rate	MEF 2	2, 7, 8, 10.2, 11, 13, 14, 15, 19, 6.1, 27, 29
CIR-compliant	Service frames that are compliant with the CIR of the bandwidth profile. CIR-compliant service frames are colored green.	MEF 7	7, 15
Circuit Emulation Service	A service that transports TDM-based traffic over a Metro Ethernet Network.	MEF 7	7, 15
Class of Service	A set of Service Frames that have a commitment from the Service Provider to receive a particular level of performance.	MEF 6.1	19, 7, 9, 10.2, 14, 15, 6.1, 27, 29
Class of Service Identifier	Information derivable from a) the EVC to which the Service Frame is mapped, b) the combination of the EVC to which the Service Frame is mapped and a set of one or more CE-VLAN CoS values, c) the combination of the EVC to which the Service Frame is mapped and a set of one or more DSCP values, or d) the combination of the EVC to which the Service Frame is mapped and a set of one or more tunneled Layer 2 Control Protocols.	MEF 9	9, 19, 10, 14, 10.2, 29
Class of Service Identifier CoSID	Information derivable from a) the EVC to which the Service Frame is mapped or b) the combination of the EVC to which the Service Frame is mapped and a set of one or more CE-VLAN CoS values	MEF 27	27
Class of Service Performance	A set of EVC-related service attributes	MEF 6.1	6.1
CLE	Customer Located Equipment	MEF 17	17
CLI	Command Line Interface	MEF 15	15
CM	Color Mode, Configuration Management	MEF 6.1	6.1, 10.2, 14, 19, 15, 29
Color Forwarding	An OVC attribute defining the relationship between the Color of an egress ENNI Frame and the Color of the corresponding ingress ENNI Frame or Service Frame.	MEF 26	26
Color Mode	CM is a Bandwidth Profile parameter. The Color Mode parameter indicates whether the color-aware or color-blind property is employed by the Bandwidth Profile. It takes a value of “color-blind” or “color-aware” only.	MEF 6.1	6.1, 19, 10.2, 14, 27, 29
Color-aware	A Bandwidth Profile property where a pre-determined level of Bandwidth Profile compliance for each Service Frame is taken into account when determining the level of compliance for each Service Frame A traffic management capability used to determine whether traffic is conformant or non-conformant to a bandwidth profile based on different CoS ID values.	MEF 7	19, 10.2, 14, 7, 15, 29
Color-blind	A Bandwidth Profile property where a pre-determined level of Bandwidth Profile compliance for each Service Frame, if present, is ignored when determining the level of compliance for each Service Frame	MEF 7	19, 10.2, 14, 7, 15, 29
Committed Burst Size	CBS is a Bandwidth Profile parameter. It limits the maximum number of bytes available for a burst of Service Frames sent at the UNI speed to remain CIR-conformant. It defines the average rate in bits/s of ingress Service Frames up to which the network delivers Service Frames and meets the performance objectives defined by the CoS Service Attribute	MEF 6.1	6.1, 19, 10, 14, 10.2, 7, 15, 27, 29
Committed Information Rate	CIR is a Bandwidth Profile parameter. It defines the average rate in bits/s of ingress Service Frames up to which the network delivers Service Frames and meets the performance objectives defined by the CoS Service Attribute. A Bandwidth Profile property where a pre-determined level of Bandwidth Profile compliance for each Service Frame, if present, is ignored when determining the level of compliance for each Service Frame	MEF 6.1	6.1, 19, 10, 14, 15, 10.2, 7, 27, 29
Connected Sub-Network	A Sub-Network that is connected by physical External Interfaces to the Ethernet Sub-Network under examination	MEF 29	29
Consecutive High Loss Interval	A sequence of small time intervals contained in T, each with a high frame loss ratio.	MEF 0	26.0.2
CoS	Class of Service	MEF 30	30
CoS	Class of Service	MEF 6.1	6.1, 7, 8, 10.2, 11, 12, 15, 17
CoS ID/ CoS Identifier	Class of Service Identifier	MEF 12	12
Coupling Flag	CF is a Bandwidth Profile parameter. The Coupling Flag allows the choice between two modes of operation of the rate enforcement algorithm. It takes a value of 0 or 1 only.	MEF 6.1	6.1, 10.2, 19, 15, 10, 14, 29
CPE	Customer Premise Equipment	MEF 17	17
CR	Clock Recovery.	MEF 3	3
CRC	Cyclic Redundancy Check	MEF 2	2, 3, 8, 11
CSN	Connected Sub-Network	MEF 29	29
CSPF	Constriant-based Shortest Path First	MEF 2	2
C-Tag	Subscriber VLAN Tag	MEF 26	26, 30
CUET	Customer Unit Edge Terminal	MEF 3	3
Current Problem List	Identifies the current existing problems (probable cause), with severity for an entity	MEF 15	15
Customer	The organization purchasing and/or using Ethernet Services. Alternate term: Subscriber	MEF 7	7, 15
Customer Edge	Equipment on the Subscriber side of the UNI	MEF 6.1	6.1, 7, 9, 15, 15, 19, 10.2, 14, 27, 29
Customer Edge VLAN CoS	The Priority Code Point bits in the IEEE 802.1Q Customer VLAN Tag in a Service Frame that is either tagged or priority tagged.	MEF 6.1	6.1, 7, 9,, 15, 10.2, 19, 14, 10, 27, 29
Customer Edge VLAN ID	The identifier derivable from the content of a Service Frame that allows the Service Frame to be associated with an EVC at the UNI.	MEF 6.1	6.1, 19, 10.2, 14, 7, 15, 27, 29
Customer Edge VLAN Tag	The IEEE 802.1Q Tag in a tagged Service Frame. When present, it contains the customer Edge VLAN ID and the Customer Edge VLAN CoS.	MEF 6.1	6.1, 9, 10.2, 19, 10, 14, 7, 15, 27, 29
C-VLAN	Customer VLAN	MEF 12	12
Data Service Frame	A Service Frame that is Unicast, Multicast, or Broadcast.	MEF 10.2	10.2
DCE	Data Circuit-terminating Equipment	MEF 2	2
DEI	Drop Eligible Indicator	MEF 30	30
DI	Data Instance	MEF 16	16
DLCI	Data Link Connection Identifier. A number attached to a data frame that identifies the PVC for the data frame.	MEF 6.1	6.1
DP	Discard Priority	MEF 12	12
DSCP	Diff-Serve Code Point	MEF 26	26, 29
DSL	Digital Subscriber Line	MEF 2	2
DSTM	Derived System Timing Mode. The IWF system clock is derived from the incoming Ethernet frames.	MEF 3	3
DTM	Derived Timing Mode The recovered service clock is derived from the incoming Ethernet frames..	MEF 3	3
Dual Rate Bandwidth Profile	A bandwidth profile that specifies both a CIR/CBS and EIR/EBS.	MEF 7	7, 15
DUT	Device Under Test	MEF 18	18
EAF	ETH Adaptation Function	MEF 12	12
EBS	Excess Burst Size	MEF 7	7, 8, 10.2, 11, 13, 14, 15, 19, 27, 29
ECDX	Emulated Circuit De/Multiplexing Function	MEF 3	3, 8, 11
ECF	ETH Connection Function, Ethernet Connection Function	MEF 2	12, 2
ECID	Emulated Circuit Identifier	MEF 3	3, 8, 11
ECT	Ethernet Connectionless Trail	MEF 12	12
EEPP	End-to-End Path Protection	MEF 2	2
EETF	ETH EVC Termination Function	MEF 12	12
EFCF	ETH Flow Conditioning Function	MEF 12	12
EFD	ETH Flow Domain	MEF 12	12
EFM	Ethernet First Mile	MEF 2	2
EFT	Ethernet Flow Termination	MEF 3	3
EFTF	Ethernet Flow Termination Function	MEF 8	8, 11, 12
Egress Bandwidth Profile	A service attribute that specifies the length and arrival time characteristics of egress Service Frames at the egress UNI.	MEF 10.2	10.2, 29
Egress EI Frame	An Ethernet Frame transmitted across the EI from the ESN toward the CSN	MEF 29	29
Egress Frame	A service frame sent from the Service Provider network to the CE.	MEF 7	7
Egress Service Frame	A service frame sent from the Service Provider network to the CE.	MEF 6.1	9, 19, 10.2, 14, 15, 6.1, 27, 29
EI	External Interface	MEF 29	29
EI Frame	An Ethernet frame transmitted across the EI toward the ESN or an Ethernet frame transmitted across the EI toward the CSN	MEF 29	29
EIR	Excess Information Rate	MEF 2	2, 6.1, 7, 8, 10.2, 11, 13, 14, 15, 19, 27, 29
EIR-compliant	Service frames that are compliant with the EIR of the bandwidth profile. EIR-compliant service frames may be colored green or yellow depending upon whether they are CIR-compliant or not, respectively.	MEF 7	7, 15
E-LAN	An Ethernet service type that is based on a Multipoint-to-Multipoint EVC	MEF 2	6.1, 2, 9
E-LAN Service	Ethernet LAN Service	MEF 10.2	10.2, 14, 19, 27
E-Line	An Ethernet service type that is based on a Point-to-Point EVC	MEF 2	6.1, 2, 3, 8, 11
E-Line Service	Ethernet Line Service	MEF 27	27
E-LMI	Ethernet Layer Management Interface	MEF 15	15, 17
EMS	Element Management System	MEF 30	30
EMS	Element Management System	MEF 17	17
End Point Map	A mapping of specified S-Tag VLAN ID values to specified OVC End Point Identifiers	MEF 26	26
End Point Type	A parameter in the End Point Map (In this specification the End Point Type is always OVC End Point.)	MEF 26	26
ENNI	External Network to Network Interface, A reference point representing the boundary between two Operator MENs that are operated as separate administrative domains	MEF 26	26, 30
E-NNI	Replaced with ENNI	MEF 15	15, 15, 17
ENNI Frame	The first bit of the Destination Address to the last bit of the Frame Check Sequence of the Ethernet Frame transmitted across the ENNI	MEF 26	26
ENNI MTU	MTU of an ENNI frame at the ENNI	MEF 26	26
ENNI-Ni	The functional element administered by the Operator of the ith Operator MEN that supports the protocols and procedures required in 26	MEF 26	26
EoS	Ethernet over Sonet	MEF 2	2
EoSONET	Ethernet over SONET	MEF 17	17
EPCF	ETH Provider Conditioning Function	MEF 12	12
EPL	Ethernet Private Line	MEF 6.1	6.1, 8, 11
ES	Errored Second	MEF 3	3, 8, 11
ESC	Ethernet Service Construct	MEF 29	29
ESCF	ETH Subscriber Conditioning Function. Ethernet Subscriber Conditioning Function	MEF 12	12, 17
ESD	Ethernet Services Definition	MEF 4	4
ESF	Extended Super Frame	MEF 3	3, 8, 11
ESM	Ethernet Services Model	MEF 4	4
ESN	Ethernet Sub-Network	MEF 29	29
ESNC	Ethernet Sub-Network Connection	MEF 29	29
ESNC End Point	A logical reference point located at a physical External Interface (EI)	MEF 29	29
ESR	Errored Second Ratio	MEF 3	3, 8, 11
ETH	Ethernet Services Layer	MEF 2	2, 4, 12, 17
ETH FPP	An Ethernet Flow Point Pool that represents an Ethernet UNI or E-NNI.	MEF 15	15
ETH-AIS	Ethernet Alarm Indication Signal function	MEF 30	30
ETH-CC	Ethernet Continuity Check function	MEF 30	30
Ethernet LAN Service	An Ethernet Service Type distinguished by its use of a Multipoint-to-Multipoint EVC	MEF 9	19, 10.2, 14, 9
Ethernet Line Service	An Ethernet Service Type distinguished by its use of a Point-to-Point EVC	MEF 10.2	19, 10.2, 14
Ethernet Service Construct	An abstract entity used to facilitate describing the externally visible behavior of an Ethernet Sub-Network (ESN) as seen by looking into the physical demarcation points of this ESN. The four basic types of Ethernet Service Constructs introduced in this document are EIs, ESNCs, ESNC End Points, and TEs. Each of these entities represents a collection of defined attributes that are used to describe this behavior	MEF 29	29
Ethernet Sub-Network	The Sub-Network that is under examination by the Ethernet Service Constructs model (see Figure 4)	MEF 29	29
Ethernet Sub-Network Connection	An association of two or more ESNC End Points that limits the exchange of EI frames to EIs in the ESNC	MEF 29	29
Ethernet Virtual Connection	An association of two or more UNIs that limits the exchange of frames to UNIs in the Ethernet Virtual Connection (EVC)	MEF 6.1	6.1, 7, 15, 19, 9, 10.2, 14, 29
EtherType	Ethernet Length/Type	MEF 12	12
ETH-LB	Ethernet Loopback function	MEF 30	30
ETH-LCK	Ethernet Lock signal function	MEF 30	30
ETH-LT	Ethernet Linktrace function	MEF 30	30
ETH-RDI	Ethernet Remote Defect Indication function	MEF 30	30
ETH-Test	Ethernet Test function	MEF 30	30
ETH-trail	An ETH-trail is an “ETH-layer entity” responsible for the transfer of information from the input of a trail termination source to the output of a trail termination sink.	MEF 2	2
E-Tree	An Ethernet service type that is based on a Rooted-Multipoint EVC.	MEF 6.1.1	6.1, 27
ETY	Ethernet Physical Layer	MEF 7	7, 15
EVC	Ethernet Virtual Connection. An association of two or more UNIs that limits the exchange of frames to UNIs in the Ethernet Virtual Connection	MEF 2	3, 2, 4, 6.1, 7, 8, 9, 10.2, 11, 12, 14, 15, 16, 17, 19, 13, , 26, 29, 30
EVC Maximum Transmission Unit Size	The maximum sized Service Frame allowed for an EVC.	MEF 10.2	10.2
EVC MTU Size	The maximum sized Service Frame allowed for an EVC.	MEF 6.1.1	6.1, 1 0.1
EVPL	Ethernet Virtual Private Line	MEF 6.1	6.1, 8, 11
E-WAN	An MEF defined ETH services aware network that provides connectivity between two or more MENs via ENNIs	MEF 26	26
Excess Burst Size	EBS is a Bandwidth Profile parameter. It limits the maximum number of bytes available for a burst of ingress Service Frames sent at the UNI speed to remain EIR-conformant	MEF 6.1	6.1, 19, 10, 14, 15, 10.2, 7, 29
Excess Information Rate	EIR is a Bandwidth Profile parameter. It defines the average rate in bits/s of ingress Service Frames up to which the network may deliver Service Frames without any performance objectives. The rate up to which the network will attempt to deliver Ethernet service frames before they are discarded.	MEF 6.1	6.1, 19, 10, 14, 15, 10.2, 7, 29
External Interface	Either a UNI or an ENNI	MEF 26	26, 29
FCS	Frame Check Sequence	MEF 8	8, 11, 12
FD	Frame Delay	MEF 10.2	10.2, 14, 15, 19
FDL	Facility Data Link	MEF 3	3, 8, 11
FDV	Frame Delay Variation (Often misquoted as Jitter)	MEF 10.2	10.2, 14, 17, 19
FDX	Full Duplex	MEF 6.1	6.1, 7, 15
FE	Functional Element	MEF 4	4
FER	Frame Error Ratio	MEF 3	3, 8, 11
FLR	Frame Loss Ratio (replaced by	MEF 10.1	10.1, 14, 17, 19
FM	Fault Management	MEF 30	30
FPP	Flow Point Pool	MEF 12	12
Frame	Short for Ethernet Frame	MEF 6.1	6.1, 19, 7, 10.2, 13, 14, 15, 29
The following definitions have migrated between MEF 10.1 and MEF 10.2
Frame Delay	The time required to transmit a Service Frame from ingress UNI to egress UNI. Editor's note: Replaced by Frame Delay Performance in MEF 10.2 below	MEF 10.1	6.1, 10.1, 19, 10, 14, 15
Frame Delay Performance	A measure of the delays experienced by Service Frames belonging to the same CoS instance	MEF 10.2	10.2, 14, 15, 19
Frame Delay Range	The difference between the Frame Delay Performance values corresponding to two different percentiles.	MEF 10.2	10.2
Frame Delay Range Performance	A measure of the extent of delay variability experienced by different Service Frames belonging to the same CoS instance.	MEF 10.2	10.2
Frame Delay Variation	The difference in delay of two Service Frames. Editor's note: Replaced by Frame Delay Variation Performance in MEF 10.2 below	MEF 10.1	6.1, 19, 10.1, 14, 15
Frame Delay Variation Performance	A measure of the variation in the delays experienced by different Service Frames belonging to the same CoS instance.	MEF 10.2	10.2, 14, 15, 19
Frame Loss Ratio	Frame Loss Ratio Editor's note: Replaced by Frame Loss Ratio Performance in MEF 10.2 below	MEF 10.1	6.1, 19, 10, 14, 15
Frame Loss Ratio Performance	Frame Loss Ratio is a measure of the number of lost frames between the ingress UNI and the egress UNI. Frame Loss Ratio is expressed as a percentage.	MEF 10.2	10.2, 19, 10, 14, 15
Frame	Short for Ethernet Frame	MEF 9	9
GARP	Generic Attribute Registration Protocol	MEF 2	2
GbE	Gigabit Ethernet	MEF 4	4
GRE	Generic Routing Encapsulation	MEF 2	2
HDX	Half Duplex	MEF 7	7, 15
High Loss Interval	A small time interval contained in T with a high frame loss ratio.	MEF 0	26.0.2
HLI	High Loss Interval	MEF 0	26.0.2
HOVC	Higher Order Virtual Container	MEF 3	3
IA	Implementation Agreement	MEF 3	3, 8, 11
IE	Information Element	MEF 15	15
IEEE	Institute of Electrical and Electronics Engineers	MEF 4	4, 8, 11, 30
IETF	Internet Engineering Task Force	MEF 2	2, 3, 8, 11, 16, 30
IGP	Interior Gateway Protocol	MEF 2	2
Ingress Bandwidth Profile	A characterization of ingress Service Frame arrival times and lengths at the ingress UNI and a specification of disposition of each Service Frame based on its level of compliance with the characterization.	MEF 10.2	10.2, 29
Ingress EI Frame	An Ethernet frame transmitted across the EI toward the ESN	MEF 29	29
Ingress Frame	A service frame sent from the CE to the Service Provider network.	MEF 7	7, 15
Ingress Service Frame	A Service Frame sent from the CE into the Service Provider network	MEF 6.1	19, 10.2, 14, 6.1, 29
Ingress Service Frame	A Service Frame sent from the CE into the Service Provider network.	MEF 9	9
Ingress	The direction from the CE into the Service Provider network.	MEF 13	13
I-NNI	Internal NNI (This definition has not been implemented in any specification)	MEF 17	17
ITU	International Telecommunication Union	MEF 2	2, 4, 16
ITU-T	International Telecommunication Union – Telecommunication standardization sector	MEF 3	3, 8, 11, 30
IWF	Interworking Function	MEF 3	4, 3, 8, 11
L1	Layer One	MEF 4	4
L2	Layer Two	MEF 4	4
L2+	Layer(s) above L2	MEF 4	4
L2CP	Layer Two Control Protocols	MEF 12	12, 29
LACP	Link Aggregation Control Protocol	MEF 2	2
LAG	Link Aggregation Group	MEF 2	2, 2, 29
LAN	Local Area network	MEF 2	2, 4, 12, 30
LANE	ATM LAN Emulation	MEF 17	17
Layer 2 Control Protocol Service Frame	A Service Frame that is used for Layer 2 control, e.g., Spanning Tree Protocol	MEF 6.1	6.1, 19, 9, 10.2, 13, 14, 29
Layer 2 Control Protocol Service Frame Delivery	The process by which a Layer 2 Control Protocol Service Frame is passed through the Service Provider network switches without being processed by those switches and delivered to the proper UNI(s).	MEF 6.1	6.1
Layer 2 Control protocol Tunneling	The process by which a Layer 2 Control protocol Service Frame is passed through the Service Provider network without being processed and delivered unchanged to the proper UNI(s).	MEF 9	9, 19, 10.2, 14, 29
LBM	Loopback Message	MEF 30	30
LBR	Loopback Reply	MEF 30	30
LCK	Locked, used in reference to LCK PDUs	MEF 30	30
Link	An ETH link or TRAN link	MEF 2	2
Link Protection Mechanism	Any mechanism (e.g. LAG) used to protect traffic in the event of link failure across a multi-link EI	MEF 29	29, 29
LLC	Logical Link Control	MEF 12	12
LOF	Loss of Frame, Loss of Frame Alignment	MEF 2	2, 8, 11
LOFS	Loss of Frames State	MEF 8	8, 11
LOH	Line OverHead	MEF 3	3
LOPS	Loss Of Packet Synchronization	MEF 3	3
LOS	Loss of Signal	MEF 2	2, 3, 8, 11
LOVC	Lower Order Virtual Container	MEF 3	3
LPM	Link Protection Mechanism	MEF 29	29
LSP	Label Switched Path	MEF 2	2
LSR	Label Switched Router	MEF 2	2
LTE	Line Termination Equipment	MEF 3	3
LTM	Linktrace Message	MEF 30	30
LTR	Linktrace Reply	MEF 30	30
MA	Maintenance Association (equivalent to a MEG)	MEF 30	30
MAC	Media Access Control	MEF 2	2, 4, 12, 16, 17, 8, 11, 30
MAID	Maintenance Association Identifier (equivalent to a MEG ID)	MEF 30	30
Mapper	A device or logic that implements a mapping function	MEF 3	3
Mapping	The process of associating each bit transmitted by the service into the SDH/SONET payload structure that carries the service. For example, mapping a DS1 service into SONET VT-1.5 / SDH VC-11 associate each bit of the DS1 with a location in the VT-1.5/VC-11	MEF 3	3
Maximum number of EVCs	A UNI service attribute	MEF 6.1	6.1
Maximum Number of UNIs	The maximum number of UNIs that may be in an EVC.	MEF 10.2	10.2
MCF	MAC Convergence Function	MEF 12	12
MD	Maintenance Domain (equivalent to a "OAM Domain in MEF 17)	MEF 30	30, 31
MD Level	Maintenance Domain Level (equivalent to a MEG level)	MEF 30	30, 31
ME	Maintenance Entity	MEF 17	17, 30, 31
Mean Frame Delay Performance	The arithmetic mean, or average of delays experienced by different Service Frames belonging to the same CoS instance.	MEF 10.2	10.2
Mean time to restore	The mean time from when a service is unavailable to the time it becomes available again	MEF 2	2
MEF	Metro Ethernet Forum	MEF 2	2, 4, 16, 30, 31
MEG	Maintenance Entity Group	MEF 17	17, 30, 31
MEG ID	Maintenance Entity Group Identifier. Equivalent to Maintenance Association Identifier (MAID).	MEF 30	30, 31
MEG Level	Maintenance Entity Group Level (equivalent to MD Level)	MEF 30	30, 31
MEN	Metro Ethernet Network	MEF 2	2, 4, 6.1, 7, 8, 9, 11, 12, 15, 16, 3, 17, 26, 30, 31
MEN-bound IWF	The IWF receiving TDM data from the customer’s TDM-based equipment, and forwarding this data in the form of Ethernet frames into the MEN.	MEF 8	8, 11
ME-NE	Metro Ethernet Network Element	MEF 15	15
MEP	MEG End Point	MEF 17	17, 30, 31
Metro Ethernet Network	The Service Provider’s network providing Ethernet services	MEF 6.1	6.1, 7, 15
Metro Ethernet Network Element	A Network Element supporting Metro Ethernet services	MEF 15	15
MIB	Management Information Base	MEF 3	3, 8, 11, 30, 31
MIF	MAC Independent Function	MEF 12	12
MIP	MEG Intermediate Point	MEF 17	17, 30, 31
MNU	Maximum Number of UNIs	MEF 10.2	10.2
MPLS	Multi Protocol Label Switching	MEF 2	4, 2, 17
MRTIE	Maximum Relative Time Interval Error	MEF 18	18
MTTR	Mean Time To Restore	MEF 7	7, 15
MTU	Maximum Transmission Unit	MEF 6.1.1	6.1, 26, 30, 31
MTU size	The maximum sized Service Frame allowed for an Ethernet service.	MEF 6.1.1	6.1
Multicast Service Frame	A Service Frame that has a multicast destination MAC address	MEF 7	19, 7, 10, 9, 10.2, 13, 14, 15
Multicast Service Frame Delivery	An EVC service attribute	MEF 6.1	6.1
Multiplex	Transmit one or more channels over a single channel	MEF 3	3
Multipoint EVC	An EVC with two or more UNIs. A Multipoint-to-Multipoint EVC with two UNIs is different from a Point-to-Point EVC because one or more additional UNIs can be added to it.	MEF 13	13
Multipoint-to-Multipoint	An EVC with two or more UNIs. A Multipoint-to-Multipoint EVC with two UNIs is different from a Point-to-Point EVC because one or more additional UNIs can be added to it.	MEF 7	7, 15
Multipoint-to-Multipoint EVC	An EVC with two or more UNIs. A Multipoint-to-Multipoint EVC with two UNIs is different from a Point-to-Point EVC because one or more additional UNIs can be added to it.	MEF 6.1	6.1, 9, 19, 10.2, 14, 29
N/A	Not Applicable	MEF 6.1	6.1
N/S	Not Specified	MEF 6.1	6.1, 7, 15
NDD	Network Demarcation Device	MEF 17	17
NE	Network Element	MEF 2	2, 4, 12, 17, 3, 30, 31
Network Operator	The Administrative Entity of a MEN. Editors note: This is used interchangeably with Operator	MEF 26	26
NI-	Network Interworking (e.g., NI-NNI)	MEF 4	4
NI-NNI	Network Interworking NNI	MEF 17	17
NMS	Network Management System	MEF 17	17, 30, 31
NNI	Network to Network Interface	MEF 3	3, 12, 17, 4, 30, 31
Node	A Provider owned network element	MEF 2	2
NT	Network Termination	MEF 4	4
OAM	Operations, Administration and Maintenance	MEF 2	2, 16, 17, 30, 31
Operator	The administrative organization responsible for a particular ESN (Carrier Ethernet Service Network)	MEF 29	29
Operator Virtual Connection	An association of OVC End Points	MEF 26	26
Ordered Pair of UNIs	A directional UNI pair of the form <Ingress UNI, Egress UNI>, selected from the UNI list for the EVC of interest.	MEF 10.2	10.2
OSS	Operations Support System	MEF 30	30, 31
OTN	Optical Transport Network	MEF 4	4
OVC	Operator Virtual Connection	MEF 26	26
OVC End Point	An association of an OVC with a specific External Interface i.e., UNI, ENNI	MEF 26	26
OVC Identifier	string that is unique among all OVCs in the Operator MEN	MEF 26	26
Path	A succession of interconnected links at a specific (ETH or TRANS) layer	MEF 2	2
PCS	Physical Coding Sub-layer	MEF 12	12
PDH	Plesiochronous Digital Hierarchy. PDH refers to the DS1/DS2/DS3 and E1/E3/E4 family of signals as defined by ITU-T and ATIS.	MEF 3	4, 3, 8, 11
PDU	Protocol Data Unit	MEF 8	8, 11, 12, 30, 31
PE	Provider Edge	MEF 2	2, 3, 4, 12
PLL	Phase Locked Loop	MEF 3	3
Pointer	A part of the SDH/SONET overhead that locates a floating payload structure. Frequency differences between SDH/SONET network elements or between the payload and the SDH/SONET equipment can be accommodated by adjusting the pointer value.	MEF 3	3
Point-to-Point EVC	An EVC with exactly 2 UNIs.	MEF 6.1	6.1, 9, 19, 7, 10.2, 13, 14, 15, 29
PRBS	Pseudo-Random Binary Sequence	MEF 18	18
PRM	Protection Reference Model	MEF 2	2
Protection merge point	A point in which the protection path traffic is either merged back onto the working path or passed on to the higher layer protocols (used in , called ‘tail-end switch’ in SONET/SDH).	MEF 2	2
PRS	Primary Reference Source	MEF 3	3
PSTN	Public Switched Telephone Network	MEF 3	3
P-VLAN	Provider VLAN	MEF 12	12
PW	Pseudo Wire	MEF 17	17
PWE3	Pseudo-Wire Emulation Edge to Edge (an IETF working group)	MEF 3	3, 8, 11
QoS	Quality of Service	MEF 2	2
Qualified Set of Service Frames	The set of frames that comply with specific criteria, such as the arrival time at the Ingress UNI and Bandwidth Profile compliance, on which a performance attribute is based.	MEF 10.2	10.2
RDI	Remote Defect Indication	MEF 3	3, 8, 11, 30, 31
Remote UNI	Remote UNI is a UNI serving as the UTA component consisting of a collection of service attributes in the UNI within an Operator’s MEN. The remote UNI is paired with a VUNI in a VUNI Provider’s MEN. At the remote UNI, Service Frames are exchanged between the Subscriber and the Network Operator MEN.	MEF 28	28
Resiliency Performance	The number of High Loss Intervals and Consecutive High Loss Intervals in a time interval T	MEF 0	26.0.2
RFC	Request for Comment	MEF 30	30, 31
Rooted-Multipoint EVC	A multipoint EVC in which each UNI is designated as either a Root or a Leaf. Ingress Service Frames at a Root UNI can be delivered to one or more of any of the other UNIs in the EVC. Ingress Service Frames at a Leaf UNI can only be delivered to one or more Root UNIs in the EVC.	MEF 10.2	10.2
RPR	Resilient Packet Ring	MEF 2	2, 4
RSTP	Rapid Spanning Tree Protocol	MEF 2	2
RTP	Real-time Transport Protocol (an IETF protocol, described in RFC 3550)	MEF 8	8, 11
Scheduled Downtime	A time interval agreed upon by both the Subscriber and Service Provider during which a service may be disabled by the Service Provider.	MEF 10.2	10.2
SDH	Synchronous Digital Hierarchy	MEF 2	2, 3, 4
Segment	A connected subset of the trail	MEF 2	2
Service Frame	An Ethernet frame transmitted across the UNI toward the Service Provider or an Ethernet frame transmitted across the UNI toward the Subscriber.	MEF 6.1	6.1, 7, 9, 19, 10.2, 13, 14, 15, 7, 15, 26, 29, 30, 31
Service Frame Delivery	A set of EVC service attributes	MEF 6.1	6.1
Service Level Agreement	The contract between the Subscriber and Service Provider specifying the agreed to service level commitments and related business agreements.	MEF 6.1	6.1, 19, 10.2, 14, 15, 7
Service Level Specification	The technical specification of the service being offered by the Service Provider to the Subscriber	MEF 6.1	6.1, 7, 15, 19, 10.2, 14
Service Multiplexing	A UNI attribute in which the UNI can be in more than one EVC instance	MEF 6.1	7, 9, 15, 13, 6.1, 19, 10.2, 14, 29
Service Provider	The organization providing Ethernet Service(s). Editor's note: used intergchangeably with Operator in marketing documents and presentations.	MEF 6.1	9, 19, 10.2, 13, 14, 6.1, 15, 7, 26, 29
SES	Severely Errored Second	MEF 3	3
SESR	Severely Errored Second Ratio	MEF 3	3
SF	Super Frame	MEF 3	3, 8, 11
SI-	Service Interworking (e.g., SI-NNI)	MEF 4	4
Single Rate Service	A service that only specifies a CIR/CBS and no EIR/EBS.	MEF 7	7
SI-NNI	Service Interworking NNI	MEF 17	17
SLA	Service Level Agreement	MEF 2	2, 3, 6.1, 7, 10.2, 14, 15, 17, 19
SLS	Service Level Specification	MEF 2	2, 3, 6.1, 7, 10.2, 14, 15, 17, 19
SNI	Service Node Interface	MEF 4	4, 15, 17, 29
SNMP	Simple Network Management Protocol	MEF 30	30, 31
SNMP Manager	An SNMP entity containing one or more command generator and/or notification receiver applications (along with their associated SNMP engine)	MEF 30	30, 31
SOAM	Service OAM	MEF 30	30, 31
SOAM PDU	Service OAM frames, or Protocol Data Unit. Specifically, those PDUs defined in [IEEE 802.1ag], [ITU-T Y.1731], or MEF specifications.	MEF 30	30, 31
SONET	Synchronous Optical Network	MEF 2	2, 3, 4
SRLG	Shared Risk Link Group	MEF 2	2
SSM	Synchronization Status Message	MEF 3	3
SSRC	Synchronization Source (a field within the RTP protocol, RFC 3550)	MEF 8	8, 11
S-Tag	Service VLAN Tag.	MEF 26	26, 30, 31
STP	Spanning Tree Protocol	MEF 2	2
Structure-agnostic	Structure-agnostic emulation is the transport of unstructured TDM, or of structured TDM when the structure is completely disregarded by the transport mechanism.	MEF 8	8, 11
Structure-aware	Structure-aware emulation is the transport of structured TDM taking at least some level of the structure into account.	MEF 8	8, 11
Structure-indicated	Encapsulation utilized for Structure-Aware TDM transport where TDM structure boundaries are indicated by pointers	MEF 8	8, 11
Structure-locked	Encapsulation utilized for Structure-Aware TDM transport where TDM structure boundaries are indicated by packet payload boundaries	MEF 8	8, 11
Subscriber	The organization or customer purchasing and/or using Ethernet Services. Editor's note: most marketing materials use the international term end-users.	MEF 2	19, 6.1, 9, 10.2, 13, 14, 2, 7, 15, 16, 26, 29
S-VLAN	Service VLAN (also referred to as Provider VLAN)	MEF 12	12
S-VLAN ID	The 12 bit VLAN ID field in the S-Tag of an ENNI Frame	MEF 26	26
TAF	Transport Adaptation Function	MEF 12	12
Tag	An optional field in a frame header. In 26 it is the 4-byte field that, when present in an Ethernet frame, appears immediately after the Source Address, or another tag in an Ethernet frame header and which consists of the 2-byte Tag Protocol Identification Field (TPID) which indicates S-Tag or C-Tag, and the 2-byte Tag Control Information field (TCI) which contains the 3-bit Priority Code Point, and the 12-bit VLAN ID field	MEF 26	26
TALS	TDM Access Line Service	MEF 3	3, 8, 11
TC	Textual Conventions	MEF 30	30, 31
TCF	Transport Connection Function	MEF 2	2
TCI	Tag Control Information	MEF 12	12
TCP	Transmission Control Protocol	MEF 2	2
TDM	Time Division Multiplexing (examples of TDM services include Nx6.14 kbit/s, DS1, DS3, E1, E3, OC3, STM1, OC12, STM3)	MEF 2	2, 8, 11, 3
TDM-bound	The direction of travel of CESoETH frames within the IWF receiving frames containing emulated circuit data from the MEN, and forwarding TDM data to the customer’s TDM-based equipment.	MEF 8	8, 11
TE	Transport Equipment	MEF 4	4, 29
Tester	Special equipment used to generate and monitor traffic for verification purposes.	MEF 9	9
T-Line	TDM Line Service	MEF 3	3, 8, 11
TLV	Type Length Value, a method of encoding Objects	MEF 30	30, 31
TLV	Type, Length and Value	MEF 16	16
TRAN	Transport Layer	MEF 2	12, 17, 2, 4
Transparency	A term used to describe that the content of a Service Frame is delivered unaltered across a MEN	MEF 6.1	6.1
Transport	A specific TRANS layer technology	MEF 2	2
TRAN-trail	A TRAN-trail (see ITU-T Recommendation G.805) is a “transport entity” responsible for the transfer of information from the input of a trail termination source to the output of a trail termination sink.	MEF 2	2
TrCP	Traffic Conditioning Point	MEF 17	17
TSP	TDM Service Processing	MEF 3	3, 8, 11
TST	Test PDU	MEF 30	30, 31
TTF	Trail Termination Function	MEF 2	2
Tunnel End Point	An ESC that represents a collection of ESNC End Points at an EI. It is used to facilitate the description of the externally observable behavior of the case where multiple ESNCs are encapsulated into a single service stream within an ESN	MEF 29	29
UML	Unified Modeling Language	MEF 30	30, 31
UNI	The UNI is the physical interface or port that is the demarcation between the customer and the service provider/Cable Operator/Carrier/MSO	MEF 2	3, 6.1, 7, 8, 9, 10.2, 11, 14, 15, 16, 19, 13, 2, 4, 12, 17, 26, 29, 30, 31
UNI C	A compound functional element used to represent all of the functional elements required to connect a MEN subscriber a MEN implementing a UNI N.	MEF 2	2
UNI EVC ID	A UNI service attribute	MEF 6.1	6.1
UNI Identifier	A UNI service attribute	MEF 6.1	6.1
UNI List	An EVC service attribute	MEF 6.1	6.1
UNI Maximum Transmission Unit Size	The maximum sized Service Frame allowed at the UNI.	MEF 10.2	10.2
UNI MTU	The maximum sized Service Frame allowed at the UNI.	MEF 6.1.1	6.1, 10.2
UNI-C	Compound architectural component on the Subscriber side of the UNI that represents all the functions required to connect a subscriber to a MEN	MEF 27	27
Unicast Service Frame	A Service Frame that has a unicast destination MAC address	MEF 7	9, 13, 7, 15, 19, 10.2, 14, 29
Unicast Service Frame Delivery	An EVC service attribute	MEF 6.1	6.1
UNI-N	A compound functional element used to represent all of the functional elements required to connect a MEN to a MEN subscriber implementing a UNI C. The functional elements within the Customer Edge that supports the MEN Subscriber’s technical capabilities and compliance to the UNI specification. A set of one or more functional elements that supports the MEN Service Provider’s technical capabilities and compliance to the UNI specification.	MEF 2	2, 27
Unscheduled Downtime	A time interval not agreed upon by both the Subscriber and Service Provider during which the Service Provider determines that the service is not usable.	MEF 10.2	10.2
User Network Interface	The User Network Interface (UNI) is the physical interface or port that is the demarcation between the customer and the service provider/Cable Operator/Carrier/MSO. The physical demarcation point between the responsibility of the Service Provider and the responsibility of the Subscriber.	MEF 2	6.1, 2, 7, 15, 19, 10.2, 14, 9, 29
UTA	The UNI Tunnel Access (UTA) associates a VUNI and remote UNI and is composed of VUNI and remote UNI Components and at least one supporting OVC	MEF 28	28
UTA Component	A specific set of capabilities which may be used as part of UTA.	MEF 28	28
UTA OVC	An OVC in the Network Operator’s MEN that provides an association of a remote UNI with an ENNI in support of UTA.	MEF 28	28
UTC	Coordinated Universal Time	MEF 30	30, 31
VC	Virtual Container	MEF 3	3
VID	VLAN Identifier	MEF 31	31
VLAN	Virtual Local Area Network	MEF 4	4, 7, 12, 15, 6.1, 8, 11, 31
VLAN ID	VLAN Identifier	MEF 12	12
VPLS	Virtual Private LAN Service	MEF 12	12, 17, 17
VPWS	Virtual Private Wire Service	MEF 17	17
VT	Virtual Tributary	MEF 3	3
VUNI	Virtual UNI (VUNI) is the component consisting of a collection of service attributes in the VUNI Provider’s MEN. The VUNI is paired with a remote UNI in a Network Operator’s MEN. The main function of the VUNI is to map frames between a set of one or more OVCs present in the VUNI Provider domain and a single UTA.	MEF 28	28
VUNI End Point	An End Point at the VUNI Provider’s side of a specific ENNI that associates the ENNI with a VUNI in support of UTA.	MEF 28	28
VUNI Provider	The Operator MEN providing the VUNI.	MEF 28	28
WAN	Wide Area Network	MEF 4	4, 12
WG	WG is the amount of traffic accepted as Green over the time interval T that should be delivered to the egress UNI	MEF 19	19
WTR	Wait to Restore	MEF 2	2
WY	WY is the amount of traffic accepted as Yellow over the time interval T that may be delivered to the egress UNI	MEF 19	19
xSTP	Spanning Tree Protocol (multiple variations)	MEF 17	17