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Circuit Emulation Service Definitions, Framework and Requirements

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Service Definition and Requirements for CES in Metro Ethernet Networks.Table 7 CES Services and supporting Synchronization Administration Models 29

    Technical Specification

    MEF 3

    Circuit Emulation Service Definitions, Framework and Requirements in Metro Ethernet Networks

     April 13, 2004

    ? The Metro Ethernet Forum 2004. Any reproduction of this document, or any portion thereof, Page 1 of 65 MEF 3 shall contain the following statement: "Reproduced with permission of the Metro Ethernet Forum." No user of this document is authorized to modify any of the information contained herein.

    Circuit Emulation Service Definitions, Framework and

    Requirements in Metro Ethernet Networks

    Disclaimer

    The information in this publication is freely available for reproduction and use by any recipient and is believed to be accurate as of its publication date. Such information is subject to change without notice and the Metro Ethernet Forum (MEF) is not responsible for any errors. The MEF does not assume responsibility to update or correct any information in this publication. No representation or warranty, expressed or implied, is made by the MEF concerning the completeness, accuracy, or applicability of any information contained herein and no liability of any kind shall be assumed by the MEF as a result of reliance upon such information.

    The information contained herein is intended to be used without modification by the recipient or user of this document. The MEF is not responsible or liable for any modifications to this document made by any other party. The receipt or any use of this document or its contents does not in any way create, by implication or otherwise: (a) any express or implied license or right to or under any patent, copyright, trademark or trade secret rights held or

    claimed by any MEF member company which are or may be associated with the ideas, techniques, concepts or

    expressions contained herein; nor

    (b) any warranty or representation that any MEF member companies will announce any product(s) and/or service(s)

    related thereto, or if such announcements are made, that such announced product(s) and/or service(s) embody

    any or all of the ideas, technologies, or concepts contained herein; nor

    (c) any form of relationship between any MEF member companies and the recipient or user of this document. Implementation or use of specific Metro Ethernet standards or recommendations and MEF specifications will be voluntary, and no company shall be obliged to implement them by virtue of participation in the Metro Ethernet Forum. The MEF is a non-profit international organization accelerating industry cooperation on Metro Ethernet technology. The MEF does not, expressly or otherwise, endorse or promote any specific products or services. ? The Metro Ethernet Forum 2004. All Rights Reserved.

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    Circuit Emulation Service Definitions, Framework and

    Requirements in Metro Ethernet Networks

    Table of Contents

    1. ABSTRACT .................................................................................................................................................. 8

    2. TERMINOLOGY ......................................................................................................................................... 8

    3. SCOPE ........................................................................................................................................................ 10

    4. COMPLIANCE LEVELS .......................................................................................................................... 10

    5. MEF DOCUMENT ROADMAP ................................................................................................................ 10

    6. CIRCUIT EMULATION SERVICE DEFINITION .................................................................................. 11

    6.1 TDM LINE SERVICE (T-LINE)................................................................................................................. 11

    6.1.1 Operational Modes of a T-Line Service .......................................................................................... 12

    6.1.1.1 Unstructured Emulation mode .................................................................................................... 12

    6.1.1.2 Structured Emulation mode ........................................................................................................ 13

    6.1.1.3 Multiplexing mode..................................................................................................................... 13

    6.1.2 Bandwidth Provisioning for a T-Line Service ................................................................................. 14

    6.1.2.1 Bandwidth allocation at 100 kbit/s granularity ............................................................................ 14

    6.1.2.2 TDM multiplexing ..................................................................................................................... 14

    6.1.2.3 Ethernet multiplexing................................................................................................................. 15

    6.2 TDM ACCESS LINE SERVICE (TALS) ..................................................................................................... 15

    6.2.1 Operational Modes of a TALS Service ............................................................................................ 16

    6.3 CUSTOMER OPERATED CES ................................................................................................................... 17

    6.4 MIXED-MODE CES OPERATION ............................................................................................................. 18

    7. CIRCUIT EMULATION SERVICE FRAMEWORK .............................................................................. 19

    7.1 GENERAL PRINCIPLES ............................................................................................................................ 19

    7.1.1 Use of External Standards ............................................................................................................. 19

    7.2 SERVICE INTERFACE TYPES .................................................................................................................... 19

    7.2.1 Examples of TDM Service Interfaces .............................................................................................. 20

    7.2.2 TDM Service Processor (TSP) ....................................................................................................... 20

    7.2.3 Circuit Emulation Inter-working Function (CES IWF) .................................................................... 21

    7.2.3.1 PDH Circuit Emulation Service .................................................................................................. 22

    7.2.3.2 SONET/SDH Circuit Emulation Service .................................................................................... 22

    7.2.4 Emulated Circuit De/Multiplexing Function (ECDX) ...................................................................... 23

    7.2.5 Ethernet Flow Termination Function (EFT) ................................................................................... 23

    7.2.6 Direction terminology .................................................................................................................... 23

    7.3 SYNCHRONIZATION ................................................................................................................................ 23

    7.3.1 CES Interworking Function- Synchronization Description .............................................................. 25

    7.3.2 Synchronous IWF and Associated Tributaries ................................................................................ 27

    7.3.2.1 Synchronous IWF and Tributaries .............................................................................................. 27

    7.3.2.2 Synchronous IWF and Asynchronous Tributaries ....................................................................... 27

    7.3.3 Asynchronous IWF and Associated Tributaries .............................................................................. 27

    7.3.3.1 Asynchronous IWF, Asynchronous Tributaries ........................................................................... 28

    7.3.3.2 Asynchronous IWF, Synchronous Tributaries ............................................................................. 28

    ? The Metro Ethernet Forum 2004. Any reproduction of this document, or any portion thereof, Page 3 of 65 MEF 3 shall contain the following statement: "Reproduced with permission of the Metro Ethernet Forum." No user of this document is authorized to modify any of the information contained herein.

    Circuit Emulation Service Definitions, Framework and

    Requirements in Metro Ethernet Networks

    7.3.4 Synchronization Administration ..................................................................................................... 28

    7.3.4.1 Single Service-Provider Owned Network ................................................................................... 29

    7.3.4.2 Multi Service-Provider Owned Network ..................................................................................... 31

    7.3.4.3 Private (customer owned) Network ............................................................................................ 34

    7.4 PERFORMANCE MONITORING AND ALARMS ............................................................................................ 35 7.4.1 Facility Data Link.......................................................................................................................... 35

    7.4.2 Alarms ........................................................................................................................................... 35

    7.4.2.1 Unstructured Service .................................................................................................................. 35

    7.4.2.2 Structured Service ...................................................................................................................... 36

    7.4.2.3 Buffer Underflow and Overflow ................................................................................................. 36

    7.4.2.4 Alarms in CCS Signaling ........................................................................................................... 36

    7.4.3 End-to-End Delay .......................................................................................................................... 36

    7.5 SERVICE IMPAIRMENT ............................................................................................................................ 36

    7.5.1 Errors within the MEN causing TDM service impairment ............................................................... 37

    7.5.1.1 Frame Loss ................................................................................................................................ 37

    7.5.1.2 Frame Delay and Frame Jitter..................................................................................................... 37

    7.5.1.3 Bit Errors ................................................................................................................................... 37

    7.5.1.4 Frame Error Ratio and IWF behaviour........................................................................................ 37

    7.5.2 Relationship to TDM service impairment metrics ........................................................................... 38

    7.5.3 Errored Seconds Requirement for PDH Circuits ............................................................................ 38

    7.5.4 Severely Errored Seconds Requirement for PDH Circuits ............................................................... 39 7.5.5 Service Impairments for SONET/SDH Circuits ............................................................................... 41

    7.5.5.1 Performance Objectives for the SONET/SDH network ............................................................... 41

    7.5.5.2 MEN Performance Objectives .................................................................................................... 42

    7.5.5.3 Summary & Discussion.............................................................................................................. 45

    7.5.6 Availability Requirements .............................................................................................................. 45

    7.6 TDM SIGNALING ................................................................................................................................... 46

    7.7 LOOPBACKS ........................................................................................................................................... 46

     7.7.1 Provider Controlled Loopbacks ..................................................................................................... 46

    7.7.2 Customer Controlled Loopbacks .................................................................................................... 47

    7.8 PROTECTION .......................................................................................................................................... 48

    7.8.1 Scenario 1 dual unprotected services........................................................................................... 48 7.8.2 Scenario 2 dual protected services .............................................................................................. 48 7.8.3 Scenario 3 Single protected service ............................................................................................. 49 7.8.4 Scenario 4 Single to dual interface service .................................................................................. 49 7.9 SERVICE QUALITY ................................................................................................................................. 50

    7.10 EFFICIENCY ........................................................................................................................................... 50

    7.11 NON-REQUIREMENTS ............................................................................................................................. 50

    8. CIRCUIT EMULATION SERVICE REQUIREMENTS .......................................................................... 51 8.1 STRUCTURED DS1/E1 NX64 KBIT/S SERVICE .......................................................................................... 51 8.1.1 TDM Framing ............................................................................................................................... 51

    8.1.2 Timeslot Assignment ...................................................................................................................... 51

    8.1.3 Multiplexing Support ..................................................................................................................... 51

    8.1.4 Clocking ........................................................................................................................................ 52

    8.1.5 Jitter and Wander .......................................................................................................................... 52

    ? The Metro Ethernet Forum 2004. Any reproduction of this document, or any portion thereof, Page 4 of 65 MEF 3 shall contain the following statement: "Reproduced with permission of the Metro Ethernet Forum." No user of this document is authorized to modify any of the information contained herein.

    Circuit Emulation Service Definitions, Framework and

    Requirements in Metro Ethernet Networks

    8.1.6 Facility Data Link.......................................................................................................................... 52

    8.1.7 Bit Oriented Messages ................................................................................................................... 52

    8.1.8 Alarms ........................................................................................................................................... 52

    8.1.9 Signaling Bits ................................................................................................................................ 53

    8.1.10 Lost and Out of Sequence Frames .................................................................................................. 53

    8.1.11 Buffer Overflow/Underflow ............................................................................................................ 53

    8.2 DS1/E1 UNSTRUCTURED SERVICE ......................................................................................................... 53 8.2.1 Framing ........................................................................................................................................ 54

    8.2.2 Clocking ........................................................................................................................................ 54

    8.2.3 Jitter and Wander .......................................................................................................................... 54

    8.2.4 Facility Data Link.......................................................................................................................... 54

    8.2.5 Alarms ........................................................................................................................................... 54

    8.2.6 Lost and Out of Sequence Frames .................................................................................................. 55

    8.2.7 Buffer Overflow/Underflow ............................................................................................................ 55

    8.3 UNSTRUCTURED DS3/E3 SERVICE .......................................................................................................... 55 8.3.1 Framing ........................................................................................................................................ 55

    8.3.2 Clocking ........................................................................................................................................ 56

    8.3.3 Jitter and Wander .......................................................................................................................... 56

    8.3.4 Alarms ........................................................................................................................................... 56

    8.3.5 Lost and Out of Sequence Frames .................................................................................................. 56

    8.3.6 Buffer Overflow/Underflow ............................................................................................................ 57

    8.4 SONET/SDH INTERFACES ..................................................................................................................... 57 8.4.1 Framing and Overhead Processing ................................................................................................ 57

    8.4.2 Clocking ........................................................................................................................................ 58

    8.4.3 Pointer Adjustments ....................................................................................................................... 59

    8.4.4 Jitter and Wander .......................................................................................................................... 60

    8.4.5 Alarms ........................................................................................................................................... 60

    8.4.6 Buffer Overflow/Underflow ............................................................................................................ 60

    8.5 GENERAL REQUIREMENTS ...................................................................................................................... 61 8.5.1 Loopbacks ..................................................................................................................................... 61

    8.5.2 Frame Loss and Reordering ........................................................................................................... 61

    8.5.3 Efficiency ...................................................................................................................................... 61

    9. MEN REQUIREMENTS ............................................................................................................................ 62

    9.1 FRAME DELAY ....................................................................................................................................... 62

    9.2 ETHERNET FRAME JITTER....................................................................................................................... 62 9.3 ETHERNET FRAME LOSS ......................................................................................................................... 63 9.4 NETWORK AVAILABILITY....................................................................................................................... 63 9.5 BANDWIDTH PROVISIONING ................................................................................................................... 63 10. REFERENCES ........................................................................................................................................... 64

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    Circuit Emulation Service Definitions, Framework and

    Requirements in Metro Ethernet Networks

    List of Figures

    Figure 1: TDM Line Service over Metro Ethernet Networks .................................................................................. 11 Figure 2: Possible TDM Virtual Private Line Configurations ................................................................................. 12 Figure 3: Example Multi-point to Point T-Line Multiplexed service ...................................................................... 14 Figure 4: Multiplexing across a single Ethernet Virtual Connection ....................................................................... 15 Figure 5: Handoff of a multiplexed trunk to an external network ........................................................................... 16

    Figure 6: Possible TDM Handoff Configurations .................................................................................................. 17 Figure 7: Customer Operated CES over a Metropolitan Ethernet Service (e.g. E-Line) .......................................... 17

    Figure 8: Mixed-Mode Service ............................................................................................................................. 18 Figure 9: Functional Elements and Interface Types ............................................................................................... 19

    Figure 10: Functional Elements of SONET/SDH emulation service ....................................................................... 22

    Figure 11: Interworking function direction ............................................................................................................ 23 Figure 12: Timing distribution architecture showing clock domains....................................................................... 24 Figure 13: CES IWF Synchronization Reference Model ........................................................................................ 26 Figure 14: Synchronization Administration for a Single Service-Provider Network ............................................... 30

    Figure 15: Synchronization Administration for a Multi Service-Provider Network ................................................. 31

    Figure 16: Synchronization Administration for a Private Network ......................................................................... 34 Figure 17: Allowed Frame Error Ratio to meet ES objectives ................................................................................ 39 Figure 18: Relationship between Packing and FER for 0.01% SES ........................................................................ 40

    -3Figure 19: Relationship between Packing and FER for 0.01% SES based on 10 BER on end to end TDM data

    stream ........................................................................................................................................................... 41 Figure 20: Provider Controlled Loopback Points ................................................................................................... 47 Figure 21: Customer Controlled Loopback Points ................................................................................................. 47 Figure 22: Dual unprotected services .................................................................................................................... 48 Figure 23: Dual protected services ........................................................................................................................ 49 Figure 24: Single protected service ....................................................................................................................... 49 Figure 25: Single to dual interface connection ....................................................................................................... 49

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    Circuit Emulation Service Definitions, Framework and

    Requirements in Metro Ethernet Networks

    List of Tables

    Table 1: TDM Service Interfaces .......................................................................................................................... 20 Table 2: CES TDM Interface Definition................................................................................................................ 22 Table 3: Timing Distribution Definitions .............................................................................................................. 24 Table 4: CE Synchronization modes and Expected Timing performance ................................................................ 25

    Table 5: CES IWF Synchronization Definitions .................................................................................................... 26

    Table 6: Timing Options per Synchronization Domain .......................................................................................... 28 Table 7: CES Services and supporting Synchronization Administration Models ..................................................... 29

    Table 8: Timing Options Single-Service Provider Owned Network ....................................................................... 30 Table 9: Timing Options Multi-Service Provider Owned Network ......................................................................... 32

    Table 10: Timing Options for a Private Network ................................................................................................... 34 Table 11: Example conversion from ES to FER for Ethernet Virtual Circuit .......................................................... 38

    Table 12: Sparse FER objectives for MEN [G.826] ............................................................................................... 43 Table 13: Background FER and BER objectives for MEN [G.826] ........................................................................ 43 Table 14: Maximal FER accounted by SESR [G.826] ........................................................................................... 44 Table 15: MEN FER Requirements for SDH/SONET CES .................................................................................... 45

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    Circuit Emulation Service Definitions, Framework and

    Requirements in Metro Ethernet Networks

    1. Abstract

    The emulation of TDM circuits over a Metro Ethernet Network (known as Circuit Emulation Services, or CES) is a useful technique to allow MEN service providers to offer TDM services to customers. This document outlines the types of the TDM services that can be offered over a MEN, and the requirements of such services. It covers both PDH services (e.g. Nx64 kbit/s, T1, E1, T3, E3) and SONET/SDH services (STS-1, STS-3, STS-3c, STS-12, STS-12c and European equivalents).

    The document contains three sections:

    - a set of service definitions for Circuit Emulation Services (CES) in the Metro Ethernet Forum context, - a framework section explaining issues with the implementation of such services - a set of requirements needed for providing such services in Metro Ethernet Networks (MEN). Separate implementation agreements for PDH and SONET/SDH services will be produced which cover the implementation of these services in an inter-operable manner. This document is intended as a reference against which any Implementation Agreement can be compared to ensure that all the service requirements have been met. 2. Terminology

    Term Definition

    AIS Alarm Indication Signal

    ANSI American National Standards Institute

    APS Automatic Protection Switching

    BER Bit Error Ratio

    BBER Background Block Error Ratio

    BLSR Bi-directional Line Switched Ring

    CAS Channel Associated Signaling

    CCS Common Channel Signaling

    CE Customer Equipment

    CES Circuit Emulation Services

    CR Clock Recovery.

    CRC Cyclic Redundancy Check

    CUET Customer Unit Edge Terminal

    DSTM Derived System Timing Mode.

    The IWF system clock is derived from the incoming Ethernet frames.

    DTM Derived Timing Mode.

    The recovered service clock is derived from the incoming Ethernet frames.

    E-Line Ethernet Line Service

    ECDX Emulated Circuit De/Multiplexing Function

    ECID Emulated Circuit Identifier

    EFT Ethernet Flow Termination

    ES Errored Second

    ESR Errored Second Ratio

    ? The Metro Ethernet Forum 2004. Any reproduction of this document, or any portion thereof, Page 8 of 65 MEF 3 shall contain the following statement: "Reproduced with permission of the Metro Ethernet Forum." No user of this document is authorized to modify any of the information contained herein.

    Circuit Emulation Service Definitions, Framework and

    Requirements in Metro Ethernet Networks

    Term Definition

    ESF Extended Super Frame

    EVC Ethernet Virtual Circuit FDL Facility Data Link

    FER Frame Error Ratio

    HOVC Higher Order Virtual Container IA Implementation Agreement IETF Internet Engineering Task Force ITU-T International Telecommunication Union Telecommunication standardization sector

    IWF Inter-Working Function LOH Line OverHead

    LOPS Loss Of Packet Synchronization LOS Loss Of Signal

    LOVC Lower Order Virtual Container LTE Line Termination Equipment MIB Management Information Base MEN Metro Ethernet Networks NE Network Equipment

    NNI Network to Network Interface PDH Plesiochronous Digital Hierarchy.

    PDH refers to the DS1/DS2/DS3 and E1/E3/E4 family of signals

    PE Provider Edge

    PLL Phase Locked Loop

    PRS Primary Reference Source PSTN Public Switched Telephone Network PWE3 Pseudo-Wire Emulation Edge to Edge (an IETF working group)

    RDI Remote Defect Indication SDH Synchronous Digital Hierarchy SES Severely Errored Second SESR Severely Errored Second Ratio SF Super Frame

    SLA Service Level Agreement SLS Service Level Specification SONET Synchronous Optical Network SSM Synchronization Status Message TALS TDM Access Line Service TDM Time Division Multiplexing

    (examples of TDM services include Nx64 kbit/s, T1, T3, E1, E3, OC-3, STM-1, OC-12, STM-4)

    T-Line TDM Line Service

    TSP TDM Service Processing

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    Circuit Emulation Service Definitions, Framework and

    Requirements in Metro Ethernet Networks

    Term Definition

    UNI User Network Interface

    VC Virtual Container

    VT Virtual Tributary

    Mapper A device or logic that implements a mapping function

    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

    Multiplex Transmit one or more channels over a single channel

    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.

    3. Scope

    The scope of this document is to address the particular requirements of transport over MEN for edge-to-edge-emulation of circuits carrying time division multiplexed (TDM) digital signals. It makes references to requirements and specifications produced by other standards organizations (notably the ITU, ANSI, IETF PWE3 and ATM Forum), and adapts these to address the specific needs of MEN. It is not in the scope of this document to duplicate any work of other related standardization bodies.

    The document covers the definition of such services, a framework in which the service provision can be understood, and also the requirements for the defined services. The actual implementation of these services in an inter-operable manner will be the subject of separate Implementation Agreements, and hence is outside the scope of this document.

    4. Compliance Levels

    The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD

    NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in

    [RFC 2119]. All key words must be use upper case, bold text.

    5. MEF Document Roadmap

    MEF draft specifications and the document roadmap are available in the members area on the Metro Ethernet Forum website at http://www.metroethernetforum.net/.

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