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An Overview of the MEF - Get Now PowerPoint

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					 Packet-based and Network-Based
Synchronisation Solutions In Depth


       Karim Traore
       Senior systems architect
       Symmetricom
       ktraore@symmetricom.com
                                  1
Agenda

• Application requirements for clock
  synchronization in 2G, 3G, LTE
• IEEE-1588 overview
• Synchronous Ethernet overview
• Advanced end-to-end clocking architectures




                                               2
Application requirements for clock
 synchronization in 2G, 3G, LTE




                                     3
Applications Requirements
(Air interface of Base Stations/NodeBs)

Applications                              Frequency                Phase                        Time
                                                                                            ±10µs(±3µs
CDMA2000                                    ±50 ppb
                                                                                            Preferred)(1)
GSM                                         ±50 ppb
UMTS-FDD/WCDMA (FDD)                        ±50 ppb
UMTS-TDD/WCDMA (TDD)                        ±50 ppb              ±2.5µs(2)
TD-SCDMA                                    ±50 ppb               ±3µs(2)
                                                              Not yet specified
LTE (FDD)                                   ±50 ppb
                                                                for MBMS
LTE (TDD)                                   ±50 ppb               ±3µs(2)

Mobile WiMAX (802.16e/m)-FDD                ±50 ppb

Mobile WiMAX (802.16e/m)-TDD
                                            ±50 ppb               ±1µs(2)

        •   Note: (1)Time alignment error wrt UTC,(2) Phase alignment of neighboring base stations




                                                                                                            4
 Synchronization Requirements


      Frequency                         Phase                              Time
      Synchronization                   Synchronization                    Synchronization
                                                                                     01:00:00     01:00:10

                   TA=1/fA                           TA=1/fA                              TA=1/fA
A                                 A                                 A
                             t

                    TB=1/fB                            TB=1/fB                                  TB=1/fB
B                                 B                                 B
                             t
           fA=fB                                 fA=fB                   fA=fB        01:00:00     01:00:10



Aligning clocks with respect to   Aligning clocks with respect to   Aligning clocks with respect to time.
frequency                         phase                             The two clocks must utilize the
                                                                    same epoch. Time synchronization
                                                                    implicitly includes phase and
                                                                    frequency synchronization




                                                                                                              5
IEEE 1588-2008 Overview




                          6
 IEEE 1588 Precise Time Protocol - PTP History and
 Standards
• Developed by HP/Agilent Laboratories (John Eidson and al.) in
  1990s
   – Synchronization of test equipment
• Industrial Automation needs for high precision applications
  (e.g., robotics, test & measurements)
   – Sub-microsecond synchronization over Controlled Local Area Networks
   – Independent of the physical layer
   – Transfer frequency and time of the day
• IEEE 1588 PTP Specifications
   – 1588 PTP 2002 (also called version 1) - approved in 2002
   – 1588 PTP 2008 (also called version 2) - approved in 2008
• ITU-T Telecom Profile (under development)
   – Set of required options, prohibited options, range and defaults value of
     attributes
• ITU-T G.8261: Timing & Synchronization aspects in Packet
  Network
   – Performance testing framework

                                                                                7
 IEEE 1588 PTP 2008
• Packet based synchronization mechanism
   – UDP/IP layers messaging (multicast and unicast) over Ethernet
• Frequency, Phase and Time
   – TDM synchronization and SyncE are Layer 1 mechanisms & support only
     frequency
• Client/server model
   – Master clock, slave clock (ordinary clock)
   – Intermediary nodes may or may not support IEEE1588 PTP (unlike SyncE)
   – On-path support mechanisms
       • Boundary clock
           – It acts as a slave clock at port that connects to the grandmaster, and as a master to all
             other ports
           – It isolates the “down stream” clocks from any delays and jitter within the switch/routers
       • Transparent clock
           – It measures residence time of PTP events
• Key performance aspect:
   – Clock algorithm (vendor specific) – Not part of IEEE 1588 PTP standard

                                                                                                         8
IEEE 1588 PTP Protocol
                                             Master Clock                              Slave Clock
Two options
       •     One step                                       Announce                                   Timestamps known
                                                                                                       slave
       •     Two steps                        t1
                                                             Sync (t0 ,t1)
                                                                                                       t0 estimated time
                                                                Follow_Up (t1)                 t1,t2    t1, t2    One step

                                                                                               t1       t1, t2       Two steps

                                                              Delay_Req                        t3       t1, t2 ,t3
                                              t4

                                                                 Delay_Resp(t4)

                                                                                               t4       t1, t2 ,t3,t4
Bandwidth requirements *
      Master -> Salve: 101.5 Kbps
      Slave->Master: 48 Kbps



*Sync update rate of 64 packets per second           Offset =[(t2 - t1) - (t4 - t3) ]÷ 2



                                                                                                                                 9
               Multicast vs Unicast Deployment –
               Unicast Negotiation Sequence (Signaling Message)


                       Switch/Router Layer
Master Clock




                                              Slave Clock
 Time




                                             Time




                                                                  Lease Duration in Bytes (10-1000s for Telecom Profile)
                                                                  Sync Interval (2X), where x = -7,-6,..0,1,..,,7
                                                                  Signaling Type
                                                                  -b0 announce request
                                                                  -00 sync request
                                                                  -90 delay_resp(onse) request


                                                                                                                  10
       Multicast vs Unicast Deployment – Unicast Announce
       Message
Master Clock                           Slave Clock


                 Switch/Router Layer




  t1

                                                t2




                                                     Flags information
                                                t3

  t4
                                                         Unicast/Multicast
                                                         1-step or 2-step
   Time




                                             Time




                                                                             11
 MEF 22 Class of Service (CoS)
• MEF 22 provides service modeling and mapping
  guidelines
    – Guidelines for number of CoS classes
    – Bundling traffic types into limited number of CoS classes
• The MBH IA specifies QoS requests to enable service
  class differentiation

Service Class                  Example of Generic Traffic Classes mapping into CoS
   Name              4 CoS Model             3 CoS Model                    2 CoS Model
 Very High (H+)     Synchronization                 -                              -
   High (H)          Conversational,       Conversational and     Conversational and Synchronization,
                  Signaling and Control     Synchronization,            Signaling and Control,
                                          Signaling and Control               Streaming
  Medium (M)           Streaming               Streaming                           -
    Low (L)          Interactive and         Interactive and                Interactive and
                       Background              Background                     Background




                                                                                                        12
Synchronous Ethernet Overview




                                13
 Synchronous Ethernet
 History and Standards

• Migration of carrier networks from SONET/SDH-centric to
  Ethernet-centric infrastructure
   – Derived from timing distribution over SONET/SDH standards
• Initial driving forces: BT and FT/Orange - 2005
   – FT demonstrated test results confirming viability of approach
   – BT provided method for handling SSMs
• Synchronization Requirements
   – Must be directly frequency synchronized by an SSU/BITS or line-
     timed
• Based on well established SONET/SDH synchronization
  model
  • ITU-T G.813 clock model




                                                                       14
 Synchronous Ethernet (SyncE)
• Developed by ITU-T standard (G.8261/G.8262/G.8264), SG15 -
  Question 13
   – No impact to IEEE 802.3 standard
• Physical layer technology
   – Based on well established SONET/SDH synchronization model (ITU-T
     G.813 clock model)
• Transfer frequency
   – SyncE does not support phase or time synchronization
• Standardization : ITU, SG15, Question 13
   – ITU-T G.8261 – Timing and Synchronization aspects in packet network
       • Defines timing and synchronization elements of packet networks
   – ITU-T G.8262 – Timing characteristics of Synchronous Equipment Slave
     Clock (EEC)
       • Defines clock (PLL) performance characteristics such as wander, jitter, phase
         transients, clock bandwidth, frequency accuracy, holdover
   – ITU-T G.8264 – Distribution of timing through packet networks
       • Specifies the SSM transport channel, namely the Ethernet Synchronization
         Messaging Channel (ESMC) protocol behavior and message format

                                                                                         15
 How SyncE is Different
                                                                           Node without SyncE

• Ethernet without SyncE (e.g. 1000Base-T)
                                                                   Slave                            Master
   – Rx clock extracted from line (line timed)
   – Tx clock generated from free-running XO                        PHY                             PHY

       • Clock within 100 ppm (125 MHz+/- 0.01 percent)
   – No relationship between Rx and Tx                              PHY                             PHY
   – Each Ethernet interface (uni-dir or bi-dir) has own
                                                                   Line cards                   Line cards
     independent timing                                                          Backplane

                                                                            Node with SyncE


• Ethernet with SyncE (e.g. 1000Base-T)
                                                                                  SyncE
                                                                                 SyncE Timing
                                                                                  Timing
                                                                                     Card
                                                                                   Card

   – Rx clock extracted from line & transferred to timing engine
   – Tx clock generated from the timing card                        PHY                            EPHY


       • Clock within 4.6 ppm when free-running
   – Tx clock uses traceable to PRC/PRS                             PHY                            PHY

   – Note SyncE clock input may replace XO or may be in             Line cards              Line cards
     addition to normal XO input                                                   Backplane




                                                                                                          16
SyncE Synchronization Plane
►   Native Ethernet recovers the Rx clock, but does not propagate the
    clock downstream
►   SyncE Tx clock is sourced from a traceable timing source, instead of
    XO
►   The equipment (system) clock to be used as the Tx clock
►   Point-to-point (link-by-link) technology
►   All links in the chain must support propagation of synchronization
          Primary Reference
          Clock (BITS/SSU)




                  SyncE                                           SyncE                                           SyncE
                  Timing                                          Timing                                          Timing
                   Card                                            Card                                            Card
                                Master             Slave                        Master             Slave                        Master

                                           Data                                            Data
    PHY                          PHY               PHY                           PHY               PHY                           PHY

                                           Clock                                           Clock


    PHY                          PHY               PHY                           PHY                PHY                          PHY


     Line cards               Line cards             Line cards               Line cards             Line cards               Line cards
                  Backplane                                       Backplane                                       Backplane




                                                                                                                                           17
 Ethernet Synchronization Messaging Channel (ESMC)

• Transport of Synchronization Status Message
  (SSM) defined in ITU-T G.707 & G.781
   – SONET/SDH: S1 Line overhead bits
• Indication of quality level (QL) of clock
  driving sync chain
                                                                    OSI Model
   – Used to control/maintain/restore sync chain                    Application

   – Timing loops, bad quality signals etc                          Presentation
                                                                      Session
• IEEE 802.3ay Organization Specific Slow                            Transport
  Protocol (OSSP)                                                     Network
   – Extendable using TLV formats




                                                        Data Link
                                                                        LLC

   – PRC traceability information                                     ESMC
                                                                       MAC
   – Processing in each network element (on reception and
                                                                      Physical
     generation)

                                                                                   18
Ethernet Synchronization Messaging Channel (ESMC) –
ITU-T OSSP

 Octet          Size                   ESMC Field
 number
     1-6        6 bytes          DA =01-80-C2-00-00-02 (hex)

    7-12        6 bytes                Source Address

    13-14       2 bytes      Slow Protocol Ethertype = 88-09 (hex)
                                                                       Clock Quality Level Information
     15         1 bytes       Slow Protocol Subtype = 0A (hex)         (PRC, SSU, EEC, DoNotUse)
    16-18       3 bytes            ITU-OUI = 00-19-A7 (hex)

    19-20       2 bytes                  ITU Subtype
                                                                     Size            SSM QL TLV
     21         4 bits                     Version                   8 bits          Type: 0x01(SSM)

                 1 bit                    Event flag                 16 bits           Length: 0x04

                                                                     4 bits              0 (unused)
                3 bits                    Reserved
                                                                     4 bits              SSM code
    22-24       3 bytes                   Reserved

    25-28       4 bytes                  SSM QL TLV

   29-1532   32-1486 bytes         Future TLV and padding

    Last 4      4 bytes                      FCS




                                                                                                         19
Ethernet Interfaces eligible to SyncE
Examples


     PHY         Description        IEEE        Coding          Synchronous
                                    802.3                         Ethernet
                                   Clause                         capable
   10BASE-F        10Mb fiber        15     NRZ, intermittent       No
  10BASE-FP     10Mb fiber, star     16     NRZ, intermittent       No
   10BASE-T     10Mb TP copper       14        intermittent         No
 100BASE-BX10   100Mb bidi fiber   58, 66        4B/5B              Yes
  100BASE-FX      100Mb fiber      24, 26        4B/5B              Yes
 100BASE-LX10     100Mb fiber      58, 66        4B/5B              Yes
  100BASE-T2    100Mb TP copper      32          PAM-5              No
  100BASE-T4    100Mb TP copper      23          8B6T               No
  100BASE-TX    100Mb TP copper    24, 25        MLT-3              Yes
  1000BASE-CX     1Gb twinax         39         8B/10B              Yes
  1000BASE-KX    1Gb backplane       70         8B/10B              Yes
  1000BASE-LX      1Gb fiber         38         8B/10B              Yes




                                                                              20
Advanced end-to-end clocking
       architectures




                               21
Native Ethernet/MPLS Access Network
Mobile Backhaul Owned by Service Provider


                                           Aggregation
                                            Point/Hub                                                   1588 PTP
                                                                             Edge                       GM

                                                                     SyncE   Node

                                                                                       SyncE            BSC
                                                       SyncE
                        Ethernet                                           Edge
                                   SyncE
                                                                           Node

                                             IP/MPLS              SyncE    Ethernet                     RNC
       1588                                  Router                        over
       PTPSlave                                                                       SyncE
                       SyncE                                               DWDM
                                                                                                        SGSN
                                                                          Edge
                                                                          Node

                                                                                    SyncE
                                                                   SyncE
                                                                             Edge              BITS
                                                                             Node              Clock
   Base Station Site                                                                                   MTSO(RNC)



                        Access network                         Aggregation network




                                                                                                                   22
Native Ethernet Access Network
Mobile Backhaul Not Owned by Service Provider

                                                                           1588 PTP
                                    Aggregation                            GM
                                     Point/Hub

                                                      Edge
                                                      Node
                                                                           BSC

                       Ethernet

                                                              Ethernet     RNC
       1588                                                   over
       PTPSlave
                                                              DWDM
                                                                          SGSN
                                                       Edge
                                                       Node



                                                              Edge
                                                              Node
   Base Station Site                                                     MTSO(RNC)



                       Access network             Aggregation network




                                                                                      23
    Summary
               IEEE 1588 PTP                                   Synchronous Ethernet
•   Frequency & Phase transfer                       •   Frequency transfer only
•   Packet layer technology                          •   Physical layer technology
•   End-to-end technology                            •   Point-to-point technology
•   Performance affected by layer 2 &3               •   Unaffected by layer 2 &3 impairments
    impairments (e.g., PDV)                          •   No multi-operator support yet
•   Multi-operators support                          •   Hop-by-hop deployment
•   End-to-end deployment                            •   Early stage of deployment
•   Deployment by one tier 1 wireless                •   Feel of trust (robust technology)
    carrier in one country                                –   Conservative choice
     –   Pre-deployment trials & extensive testing
                                                     •   Brownfield considerations
         by carriers & vendors
•   Note: 1588 PTP addresses just the protocol
    aspects: what is critical is the clock
    algorithm, which is not standardized


    Hybrid cases: PTP used for phase and SyncE used for frequency on same network



                                                                                                24
  For in-depth presentations of Carrier Ethernet for business, Ethernet services, technical
   overview, certification program etc., visit: www.metroethernetforum.org/presentations


     For more information regarding joining the MEF:
     Visit:               www.metroethernetforum.org
     Email us at:         manager@metroethernetforum.org
     Call us at:          +1 310 258 8032 (California, USA)



Accelerating Worldwide Adoption of
Carrier-class Ethernet Networks and Services
                                                                                              25

				
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