Download An Overview of the MEF

Introducing the Specifications of the
MEF
MEF 22: Mobile Backhaul Implementation
Agreement
February 2009
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Approved MEF Specifications
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MEF 2
MEF 3
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MEF 4
MEF 6.1
MEF 7
MEF 8
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MEF 9
MEF 10.1
MEF 11
MEF 12
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MEF 13
MEF 14
MEF 15
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MEF 16
MEF 17
MEF 18
MEF 19
MEF 20
MEF 21
Requirements and Framework for Ethernet Service Protection
Circuit Emulation Service Definitions, Framework and Requirements in
Metro Ethernet Networks
Metro Ethernet Network Architecture Framework Part 1: Generic Framework
Metro Ethernet Services Definitions Phase 2
EMS-NMS Information Model
Implementation Agreement for the Emulation of PDH Circuits
over Metro Ethernet Networks
Abstract Test Suite for Ethernet Services at the UNI
Ethernet Services Attributes Phase 2*
User Network Interface (UNI) Requirements and Framework
Metro Ethernet Network Architecture Framework
Part 2: Ethernet Services Layer
User Network Interface (UNI) Type 1 Implementation Agreement
Abstract Test Suite for Traffic Management Phase 1
Requirements for Management of Metro Ethernet
Phase 1 Network Elements
Ethernet Local Management Interface
Service OAM Framework and Requirements
Abstract Test Suite for Circuit Emulation Services
Abstract Test Suite for UNI Type 1
User Network Interface (UNI) Type 2 Implementation Agreement
Abstract Test Suite for UNI Type 2 Part 1: Link OAM
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MEF 22
Mobile Backhaul Implementation Agreement
* MEF 10 .1 replaces and enhances MEF 10 Ethernet Services Definition Phase 1 and replaced MEF 1 and MEF 5. MEF 6.1 replaced MEF 6.
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This Overview Presentation
• Purpose:
– This presentation is an introduction to MEF 22
• Audience
– Equipment manufacturers building devices that will carry mobile
backhaul traffic over Carrier Ethernet
– Useful for mobile backhaul service providers architecting their
systems for Carrier Ethernet
– For wire-line service providers architecting their systems for the
inclusion of mobile backhaul traffic over Carrier Ethernet
• Other Documents
– Presentations of the other specifications and an overview of all
specifications is available on the MEF web site
– Other materials such as white papers and case studies are also
available
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MEF 22 Overview Presentation Topics
• MEF 22 Overview
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Objectives
Scope
Implementation phases
Terminology and concepts
• MBH IA Specification Sections
– Use cases and migration strategy
– Services
• Classes of service
• Service types
– Generic interworking function
– Synchronization and clock recovery
• Synchronization background information
• References and related documents
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MEF 22 Overview Section
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MEF Mobile Backhaul Implementation Agreement
• Overview
– Provides generic specification for Ethernet backhaul
architectures for mobile networks (2G, 3G, 4G)
– Explains how to apply existing MEF specifications
– User-Network Interface requirements
– Service Requirements
RAN BS
• Service definitions
UNI
• Clock synchronization for
UNI
application support
UNI
Carrier Ethernet
Network
RAN NC
RAN BS
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About the Specification
• The role of the document is to provide guidelines for
implementing mobile backhaul network that is based on
Carrier Ethernet
• The document includes requirement and recommendations
for the equipment, architecture & operation of Mobile
Backhaul network.
• Mobile Backhaul Implementation Agreement is an MEF
specification
• It provides a set of requirements and guidelines detailing the
use of existing MEF standards and other industry standards in
a way that best fit mobile backhaul requirements.
• The Implementation Agreement aims to describe best
practices as a blueprint for a successful implementation of
mobile backhaul services.
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Scope of the Implementation Agreement
• Utilize existing MEF technical specifications with required
extensions to interface and service attributes.
• Provide requirements for UNI-C and UNI-N beyond those in MEF
13 & MEF 20.
• Define requirements for the implementation of Ethernet Services.
• Provide requirements for the usages of Link OAM and Service OAM
Fault Management.
• Use a single Metro Ethernet Network with external interfaces being
only UNIs.
• Provide high-level requirements for Class of Service.
• Define synchronization requirements where possible for packet
based synchronization methods that are transparent to the CEN.
• Specify functional requirements applicable to legacy mobile
technology using the Generic Inter-Working Function (GIWF)
interfaces.
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Phased Implementation
MEF 22 Mobile Backhaul Implementation Agreement Phase 1 was
approved as an official MEF Specification in January 2009.
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This first phase includes:
– EVCs spanning a single MEN (Metro Ethernet Network).
– Synchronization is either delivered outside of the Ethernet
transport network or using a packet based method that is
transparent to the MEN*, e.g. treated as standard Service Frames
– GSM, WCDMA, CDMA, CDMA2000, and WiMAX 802.16e.
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Subsequent phases are anticipated to include:
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EVCs spanning arbitrary number of MENs.
Other synchronization methods.
Other mobile standards, such as LTE (Long Term Evolution).
Synchronous Ethernet
And other topics
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Terminology and Concepts (1)
• The Specifications and presentations refer to MENs (Metro
Ethernet Networks) not Carrier Ethernet Networks. Why is that?
– The technical work of the MEF as described in the specifications, together
with the work of associated standards bodies, collectively enable the
functionality and attributes of Carrier Ethernet
– The completed specifications continue to refer to MENs (Metro Ethernet
Networks) but this is now a generic term covering the enabled service
network in the increasing variety of Access, Metro and long haul networks
– Some Specifications refer to CENs (Carrier Ethernet Networks) this term
may be used interchangeably with MENs as in this document
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Terminology and Concepts (2)
• The scope of the “Mobile Backhaul”
network as defined for the specification
– The Mobile Backhaul is defined as the network
between the:
• Radio Network Controllers (RNCs), and
• Radio Access Networks Base Station (RAN BS).
– Mobile Backhaul Implementation Agreement provides
guidelines to architecture, equipment & operation to
that part of the network
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Terminology and Concepts (3)
• Network Elements addressed by the Specification
Terminology used in the specification and this overview
GIWF
Generic Inter-working Function
PCP
Priority Code Point
PEC
Packet based Equipment Clocks
PTP
Precision Time Protocol
RAN
Radio Access Network
RAN BS
RAN Base Station
RAN CE
RAN Customer Edge
RAN NC
RAN Network Controller
RNC
Radio Network Controller
• The RAN CE is a generic term that identifies a mobile network node or site,
such as a RAN network Controller or RAN Base Station
• A RAN NC may be a single network controller or a site composed of several
network elements including: OSS, WCDMA Radio Network Controller or
Synchronization Server.
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Terminology and Concepts (4)
• The RAN Base Station is shown in the
specification as in the diagram on the right
Carrier
Ethernet
Network
• However, this is intended to represent all
varieties of configurations typically enclosed
and may support several cell towers
• A RAN BS may also be a single base station
or a collection of several base stations as
shown on the right. The actual
implementations may integrate the GIWF
function, microwave backhaul functions, etc.,
RAN BS
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Mobile Backhaul Implementation Agreement
Section Review
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Section Review
• Use Cases and Migration Strategy
– Four use cases address the migration from legacy networks
• Services
– This section examines the application of six Carrier Ethernet
service types together with the class of service
recommendations
• Generic Interworking Function
– Addresses generic devices to be used as part of the migration
strategy
• Synchronization and Clock Recovery
– Addresses the issues of clock preservation across Carrier
Ethernet mobile backhaul networks
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Legacy Mobile Backhaul Migration
Packet offload over Carrier Ethernet – Use Case 1a
Legacy
Network
Carrier Ethernet
Network
RAN BS
Non-Ethernet
I/F
GIWF
UNI
UNI
GIWF
Non-Ethernet
I/F
RAN NC
Emulation over Carrier Ethernet – Use Case 1b
Carrier Ethernet
Network
RAN BS
Non-Ethernet
I/F
GIWF
UNI
UNI
GIWF
Non-Ethernet
I/F
RAN NC
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When RAN nodes are equipped with Ethernet
RAN dual stack – Use Case 2a
Legacy
Network
Carrier Ethernet
Network
RAN BS
UNI
UNI
RAN NC
Full Ethernet – Use Case 2b
Carrier Ethernet
Network
RAN BS
UNI
UNI
RAN NC
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Migration legacy to Carrier Ethernet Backhaul (1)
– The Mobile Backhaul Implementation Agreement covers
various steps in the migration phase
– It describes two use cases of mobile backhaul networks
that are composed of a legacy network and a Carrier
Ethernet network in parallel.
– The first of these two use cases employs a “Generic
Inter-Working Function” to interface between the legacy
base station / network controller and the Carrier
Ethernet network:
Legacy
Network
Carrier Ethernet
Network
RAN BS
Non-Ethernet
I/F
GIWF
UNI
UNI
GIWF
Non-Ethernet
I/F
RAN NC
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Migration legacy to Carrier Ethernet Backhaul (2)
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The second legacy use case describes a hybrid offload
model. The network controller and base stations
maintain legacy network (TDM, ATM, or HDLC/PPP)
connections for voice traffic and native Carrier
Ethernet interfaces for data traffic:
Legacy
Network
Carrier Ethernet
Network
RAN BS
UNI
UNI
RAN NC
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MBH Service Requirements Addressed
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Carrier Ethernet Services for Mobile Backhaul
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Typically there are 1-2 RNC sites and between hundreds to
thousands of RAN BS sites
Bandwidth requirements for a base station site will vary and
may range from a few Mbps to over a Gbps
Services need to be:
• Scalable
• Flexible
• Cost effective
Generally, the requirement is to follow one of the following
MEF services:
• Ethernet Private Line Service
• Ethernet Virtual Private Line Service
• Ethernet Private LAN Service
• Ethernet Virtual Private LAN service
• Ethernet Private Tree Service
• Ethernet Virtual Private Tree Service
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Service Definitions – Point-to-Point (E-Line)
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Similar to leased lines
Requires traffic separation per RAN BS at RAN NC
The specification cover private and virtual private line cases
EVPL shown here
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Service Definitions – Ethernet LAN Service (E-LAN)
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Virtual LAN service
Requires traffic separation per RAN BS at RAN NC
The specification cover private and virtual private LAN cases
EP-LAN shown here
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Rooted Multipoint (E-Tree Service)
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Similar behavior as leased lines
Supports simpler RAN BS and RAN NC solutions
Multiplexing could be used for increased traffic separation
The specification cover private and virtual private routed multipoint
services
• EVP-Tree shown here
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Traffic Separation
• MEF 22 provides service modeling and mapping guidelines
– Guidelines for the number of CoS classes to use
– Bundling traffic types into limited number of CoS classes
– CoS class performance requirements
• The MBH IA specifies QoS requests to enable service class
differentiation
– The “must” request is to support at least two Class of Service. But
the recommended request is to support four Class of Service.
Service Class
Name
Example of Generic Traffic Classes mapping into CoS
4 CoS Model
3 CoS Model
2 CoS Model
Very High (H+)
Synchronization
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-
High (H)
Conversational,
Signaling and Control
Conversational and
Synchronization,
Signaling and Control
Conversational and Synchronization,
Signaling and Control,
Streaming
Medium (M)
Streaming
Streaming
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Low (L)
Interactive and
Background
Interactive and
Background
Interactive and
Background
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Technology Migration and
Interworking
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Mobile Backhaul Generic Interworking Function (1)
• The Mobile backhaul GIWF (Generic Interworking Function)
– Mobile Backhaul Generic Interworking Function (GIWF) provides
adaptation and interconnection between any legacy mobile
equipments (TDM/ATM/HDLC based) in the base station and
network controller and the Metro Ethernet network at the UNI.
– It enables the joint backhaul of any combination of 2G, 2.5G, 3G
(legacy based) and Evolved-3G & 4G (Ethernet based) voice and
data traffic over a single Carrier Ethernet RAN (Radio Access
Network).
– The adaptation of the legacy mobile traffic to the Carrier Ethernet
service can be based on TDM circuit emulation standards as well as
ATM/HDLC pseudo-wire standards.
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Mobile Backhaul Generic Interworking Function (2)
• How the GIWF handles existing GSM based networks
– GSM uses a number of T1 (1.5 Mbit/s) or E1 (2 Mbit/s) circuits to connect
the base station with the network controller.
– The GIWF terminates a circuit emulation service (CES) per such E1/T1
circuit at the cell site or service edge and at the network controller site
– A variety of circuit emulation services can be used in the implementation
agreement (MEF8 (CESoE), TDMoMPLS, SAToP, CESoPSN)
Service Provider Network
TDM Circuit Emulation
TDM
CES Ethernet
IWF
Carrier Ethernet
Network
Ethernet CES
TDM
IWF
RAN NC
RAN BS
TDM Base Station
demarcation
Ethernet
UNI
E-Line
Service
Ethernet
UNI
TDM Network
Interface
CES IWF: Circuit Emulation Interworking Function
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Technology Interworking
• How the GIWF handles existing UMTS / WCDMA networks
– These Technologies uses ATM over a number of bundled T1 (1.5 Mbit/s)
or E1 (2 Mbit/s) circuits to connect the base station with the network
controller.
– The GIWF terminates an ATM pseudo-wire or a TDM circuit emulation
tunnel at the cell site or service edge and at the network controller site
– A variety of ATM pseudo-wire and/or TDM circuit emulation standards can
be used in the implementation agreement
Service Provider Network
ATM Pseudo-wire
ATM/TDM
CES Ethernet
IWF
Carrier Ethernet
Network
Carrier Ethernet
Network
Ethernet CES
ATM/TDM
IWF
RAN NC
RAN BS
ATM / TDM BS
demarcation
Ethernet
UNI
E-Line
Service
Ethernet
UNI
ATM / TDM
Network Interface
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Technology Interworking
• How MEF 22 aligns with ATM pseudo-wire and TDM
circuit emulation solutions?
– The MEF has defined MEF 8 for TDM over Ethernet circuit
emulation; the specification is maintained by the MEF
– The MPLS-based circuit emulation of TDM and ATM circuits is
defined by the IP/MPLS Forum. The MEF liaises with the
IP/MPLS Forum to ensure the specifications are aligned.
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Mobile Backhaul Synchronization
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Synchronization
• Key Issue
– Migration to all packet networks means loss of TDM clock source
• Three principal Components of sync
– Frequency synchronization(2G, 3G, 3.5G)
– Phase synchronization(4G in some cases)
– Time of Day synchronization
• The following approaches are possible
– Outside of the Ethernet transport network (e.g. via GPS)
– Packet Based Synch using dedicated packet flow (e.g. IEEE 1588
V2, NTP) or using the clock carried by circuit emulated data (the
following methods are possible : Differential Clock Recovery,
Adaptive Clock Recovery)
– Synchronous Ethernet
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MEF Approach to Synchronization
• Packet based
– Packet based methods are in scope
for Phase 1
• Synchronization quality requirements
reference the ITU G.8261 standard
• The IA is agnostic to specific methods/implementations like
adaptive clocking, RTP-extended adaptive clocking, IEEE1588
etc.
– Eliminates the cost and need for retention of T1/E1 circuit solely for
synchronization
• Other approaches
– Common Clock (GPS, legacy E1 clocking) is out of scope
– Synchronous Ethernet in scope for future phases
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Mobile Backhaul Synchronization
Background
Background
The following 8 slides are intended to assist the readers
understanding of the topic and background concepts behind the
implementation agreement
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Mobile Backhaul Synchronization Background (1)
• Background Information
– The following slides are not descriptive of MEF 22 but are intended as
useful background knowledge
• Relevant ITU Standards for Clock Requirements for Circuit
Emulation services
– The synchronization requirements are derived from the ITU-T
Recommendation G.8261, which studies timing and synchronization
over packet based networks and examines the requirements for
different mobile technologies.
– Subsequent versions of this ITU specify clocks conforming to G.823
(for signals related to the E1-hierarchy) or G.824 (for T1-hierarchy
signals)
– These standards define the permissible output jitter and wander for
two levels
• Clock (Jitter and wander) requirements for the traffic interface are
defined in ITU-T G.823, Section 5 for E1 and in ITU-T G.824,
Section 5, for T1
• Clock (Jitter and wander) requirements for the synchronization
interface are defined in ITU-T G.823, Section 6.2.4 for E1 and in
ITU-T G.824, section 6.2.2 for T1
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Mobile Backhaul Synchronization Background (2)
• Principle types of synchronization
– There are 3 principal types of synchronization that are of
importance:
• Frequency synchronization
– Relate to the alignment of clocks in frequency, a process
that is also referred to as syntonization
• Phase synchronization
– Imply that the two clocks are aligned in phase, a process
that also referred to as relative-time synchronization
• Time synchronization
– Also referred to as time-of-day synchronization or wallclock synchronization where the clocks in question are
traceable to a common, universal, time-base such as
UTC
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Mobile Backhaul Synchronization Background (3)
• Important synchronization types and requirements in
cellular networks (1)
– GSM Base Station (frequency synchronization)
• Timing requirement applicable to the GSM radio interface can
be found in the ETSI technical specification TS 145.010
• The radio interface requirement for a GSM base station is
frequency accuracy of ±50 ppb and ±100 ppb (pico BS)
– The need for this requirement stems primarily from the need
to support handover of mobiles between base stations
– UMTS FDD Base Station (frequency synchronization)
• The timing requirement applicable to the WCDMA FDD radio
interface can be found in the ETSI technical specification TS
125.104
• The radio interface requirement for UMTS FDD base stations is
a frequency accuracy of ± 50ppb (wide area), ±100 ppb (local
area) and ±250 ppb (Home BS); for the FDD mode there are no
phase alignment requirements
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Mobile Backhaul Synchronization Background (4)
• Important synchronization types and requirements in cellular
networks (2)
– UMTS TDD Base Station (frequency and phase synchronization)
• The timing requirement applicable to the WCDMA TDD radio interface can
be found in the ETSI technical specification TS 125.105
• The radio interface requirement for UMTS TDD base stations is a
frequency accuracy of ±50 ppb; for the TDD mode there is the additional
requirement for the phase alignment of neighboring base stations to within
2.5 µs.
– 3GPP2 CDMA2000 Base Station (frequency and time synchronization)
• The relevant CDMA2000 standards are the 3GPP2 C.S0010-B and 3GPP2
C S0002-B
• According to the CDMA2000 specifications the average frequency
difference between the actual CDMA transmit carrier frequency and
specified CDMA transmit frequency assignment shall be less than ±50 ppb
• The time error should be less than 3μs: due to that it is a common practice
to equip CDMA base stations with GPS receivers
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Mobile Backhaul Synchronization Background (5)
•
How network synchronization is achieved for emulated circuits
over a packet-based infrastructure (1)
– There are 3 major methods:
1. Network Synchronous Method.
• This is supported via a local GPS or via a master –slave
synchronization network using the physical layer to distribute the
synchronization
2. Differential clocking mode
• A PRC-traceable reference is required at both ends of the packet
network. However often a this may not be available for service
providers at every possible site, such as a remote cell site
• The system will use the PRC-traceable clock source, which is fed
into all the elements of the network
• The system will use the common clock source as well as observe
the time stamps received from the circuit emulation service (CESoE
/ SAToP / CESoPSN) packets received from the packet network
and calculate the differential to recover an accurate clock
• This recovered clock reference is then used to transmit the TDM
frames
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Mobile Backhaul Synchronization Background (6)
• How network synchronization is achieved for emulated
circuits over a packet-based infrastructure (2)
3. Adaptive Clock Recovery
• In some deployments, there is no PRC-traceable reference
nor GPS source available at the remote site
• The CPE at the cell site has to completely rely on the incoming
packet stream from the Ethernet network to calculate the
clocking reference
• The clock accuracy, thus derived, should be of suitable high
quality, sufficient to recover a timing signal compliant to the
3GPP mobile standards (e.g. accuracy of 16 ppb or higher)
• The central office will be using a primary clock source
reference, and the receiving site will derive the clock based on
the incoming circuit emulation service packets
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Mobile Backhaul Synchronization Background (7)
•
The requirements from Clock Recovery over PSN based MBH
–
Any clock recovery over packet mechanism should be designed
primarily to meet the clock synchronization requirements for GSM
and UMTS RANs as specified in ETSI EN 300 912 and TS 125 402
"Synchronization in UTRAN stage 2”
–
Jitter and wander measured at the output of the GIWF TDM-bound interface
should meet the traffic interface requirements specified in ITU-T
recommendations (G.823/G.824/G.825)
–
The wander budget allocated to the MEN and the GIWF as measured at the
output of the GIWF TDM-bound interface should meet the traffic interface
requirements of ITU-T G.8261, Deployment Case 2
–
Frequency accuracy in holdover should conform to a standard Clock as
applicable
–
A robust clock recovery mechanism should also maintain its
outstanding performance even under the most demanding network
conditions, such as high Packet Delay Variation (jitter) and packet
loss ratio
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Mobile Backhaul Synchronization Background (8)
• How clock recovery solutions are related to 1588v2 and NTP
– IEEE 1588v2 and NTP (Network Time Protocol) define how to
transport time information over the network
• The algorithms to reconstruct and recover the clock are vendor
specific
• This is an "implementation" issue rather protocol
– 1588v2 implementation actually calls for a standardized
implementation of the information carried while maintaining the high
clock accuracy currently achieved through clock recovery
implementations
• The clock recovery implementations should interoperable and
complement 1588v2 standard.
– The clock recovery implementations should comply with G.823,
G.824, G.8261, G.8264, G.8265 and G.8266 as applicable
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MEF 22 Related Documents
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MEF 22 Reference Works
• Other MEF documents on which parts of the Mobile Backhaul
Implementation Agreement are based
– The services and requirements that appear at the Mobile Backhaul
Implementation Agreement doc are based on:
• The services defined in MEF 6.1 Ethernet Service Definition –
Phase 2
• The attributes defined in MEF 10.1 Ethernet Service Attributes –
Phase 2
• MEF 13 & MEF 20 (UNI Types 1 & 2)
• Other documents currently under development by the MEF
Technical Committee (Ethernet Classes of Service, Service-OAM
and External Network-to-Network Interface technical
specifications)
– It is highly recommended to be familiar with the requirements in the
above two documents before reading the Mobile Backhaul
Implementation Agreement document. These are available on the
MEF Public web site Information Center
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Final Word
• Next Actions
– Read the detailed MEF 20 Implementation
Agreement available on the MEF web site
– Further information related to implementation is to be
found on the MEF site:
• Further Technical FAQs beyond the scope of this
document
• A full reference presentation with additional
market perspectives
• White papers, case studies, applications
• Video presentations
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End of MEF 22 Overview
More information:
www.metroethernetforum.org
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