Synchronization in Packet-based Networks Dennis Hagarty, Technical Marketing Engineer BRKSPG-2170

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2 Synchronization in Packet-based Networks Dennis Hagarty, Technical Marketing Engineer BRKSPG-2170

3 Agenda Introduction: What Is Synchronization? Overview of Synchronization and Timing Distributing Timing Reference With Packets (PTP) Frequency to Phase/Time: What s Changing? Standardization and Deployment Conclusion

4 What is Synchronization?

5 Some Basic Concepts A clock is an oscillator and a counter There can be three different types of synchronization: Frequency: doing things at the same rate Phase: doing things at the same time (and probably the same rate as well) Time: doing things using the same view of wall clock (time of day) Syntonization is the alignment of clocks to the same frequency Synchronization is the alignment of clocks to the same time/phase Free-running is when local clock is running without external reference Holdover is when local clock is running without external reference, but using information from an external reference that it was recently aligned with

6 Frequency, Phase and Time Time, Phase Frequency Router# show clock 13:38: UTC Sat Jun Reference in Output Frequency Output Frequency Output Frequency

7 Frequency Synchronization What are some examples of frequency synch? Sending data via TDM/SDH/SONET network (Transmit frequency = Receive frequency) Pulling materials through a long series of machines (printing press, rolling mill) Radio/cellular networks Carrying TDM over a packet network with Circuit Emulation (CEM) Tuning musical instruments? How to we maintain/distribute frequency? Physically: TDM circuit, GPS, SyncE, BITS/SSU network, WWVB Via Packet: PTP (IEEE ), Adaptive Clock Recovery (ACR) Cell Radio Cell Site Router Same Frequency Aggregation Router Controller

8 Phase Synchronization What are some examples of phase synch? Distributing power for the A/C power grid (those Hertz have to align) Robots working together Single Frequency broadcasting (SFN) Playing in an orchestra? How to we distribute phase synch? Physically: Physical pulses, GPS signals (1PPS) Via packet: PTP (IEEE )

9 Time Synchronization What are some examples of time synch? Submitting financial transactions in chronological order Correlating log files and events/alarm across a whole network Measuring one-way delay in networks (IP-SLA, TWAMP, etc) Running scientific experiments (e.g. Large Hadron Collider at CERN) Ensuring billing records are accurate (off-peak, on-peak, prime time) Typical billing and alarm systems require sync in the millisecond range How to we distribute time synch? Physically: GPS signals, radio signals (WWVB, DCF77), talking clock Via packet: NTP, PTP (IEEE )

10 Phase Sync Failure Example Timeslots? TDD Handover Fails Small Cells Not Co-ordinated

11 Time Sync Failure Example Time Applications Y.1731 Performance Management Customer Equipment 1 Way Delay = RxTime - TxTime Service Provider Customer Equipment NEs must be synchronized (ToD) for one-way delay MEP MEP 1DM TxTimeStampf RxTimeStampf 1DM

12 Overview of Synchronization & Timing

13 Frequency Distribution: Physical or Packet? Two approaches: SEC SEC EEC EEC SONET- SDH SONET- SDH SyncE SyncE Source Physical Layer Frequency Distribution Recovered Clock Master Packet exchange with timing information Slave Packet Layer Frequency Distribution SyncE

14 Frequency Sources Two types: Physical and Packet Physical Layer Frequency Distribution Synchronous Ethernet in-band timing BITS/SSU 10 MHz (typically from GPS receiver) TDM Line clocking in-band timing Packet Based Frequency Distribution IEEE or PTPv2 (there are others) Line/TDM interfaces SyncE = 1GE, 10GE, BITS/SSU/10MHz External source input/output 10 MHZ input Input from GNSS (GPS) receiver GNSS Antenna GPS, Glonass, Compass,

15 Frequency Distribution: Clock Recovery Two approaches: Input frequency with noise & jitter Clock Recovery Local Oscillator Physical Layer Frequency Distribution Recovered Clock Clock frequency recovered from input Signal conditions local oscillator Output for frequency consumer/user Frequency info in packet stream Noisy packets Servo Packet Selection PLL Local Oscillator Packet Layer Frequency Distribution Recovered Clock Classify the packets Select the good packets (discard the noisy ones) Process these packets to recover stable clock

16 SONET/SDH Frequency Sync For your reference Clock Designation Long Term Accuracy (± PPM) Holdover Stability (± PPM) Free Run Accuracy (100 ns in ) Holdover Accuracy (100 ns in ) Stratum N/A 2.7 hours N/A Stratum sec 16.7 min Stratum 3E sec 8.3 sec Stratum sec 0.27 sec SMC sec 0.22 sec Stratum 4E 32 N/A sec N/A Stratum 4 32 N/A sec N/A

17 Validating Recovered Clock: Physical Distribution TIE MTIE & TDEV Masks per G.823, G.824, G.8261 Physical Frequency Distribution PRC/PRS Source BITS Reference SyncE or TDM/SDH Device compares recovered clock to reference SyncE or TDM/SDH EEC/SEC EEC/SEC EEC/SEC Recovered clock

18 Validating Recovered Clock: Packet Distribution TIE MTIE & TDEV Masks per G.823, G.824, G.8261 Packet Frequency Distribution PRC/PRS Source Reference Device compares recovered clock to reference BITS PTP Master PTP Slave Recovered clock

19 Clock Traceability: Quality Level (QL) Determining the best available clock Which clock source should I use? PRC Source + QL + QL + QL SSU-A Source + QL QL-Disabled Mode 1. Management commands 2. Signal Failure 3. Local Priority (per interface) References: ITU-T G.871 / G.8261 QL-Enabled Mode 1. Management commands 2. Quality level 3. Signal Failure 4. Local Priority (per interface)

20 Clock Traceability: Quality Level (QL) QL implementation depends on the technology Transport QL Name Description BITS/SSU/T1/E1 SSM 4 bits interlaced in the data stream SONET/SDH SSM 4 bits interlaced in the data stream SyncE ESMC Slow Protocol frames over link Note: SSM may not be supported on normal traffic interfaces timing ports! ESMC carries the QL NOT the timing (that s physical) 1588 Telecom Profile clockclass Sent by master in Announce msg ESMC frames SyncE Node IEEE802.3 Slow Protocol SyncE Node clockclass PTP Attribute ESMC = Ethernet Synchronous Messaging Channel / SSM = Sync Status Messaging

21 Clock Traceability: Quality Level (QL) QL can be mapped between technologies (e.g. Telecoms) SSM G.781 ESMC PTP clockclass Option I Option II Option I Option II 0001 QL-PRS QL-STU QL-PRC QL-ST QL-SSU-A QL-TNC QL-SSU-B QL-ST3E QL-ST3 QL-EEC QL-SEC QL-EEC QL-SMC QL-PROV QL-DNU QL-DUS 110 ANSI/SONET & SDH Terms PRS Primary Reference Source PRC Primary Reference Clock = G.811 STU Stratum Traceability Unknown QU Quality Unknown UNK Unknown ST2 Stratum 2 = G.812 Type II TNC Transit Node Clock = SSU-A SSU-A Sync. Supply Unit A = G.812 Type V ST3E Stratum 3E = G.812 Type III ST3 Stratum 3 = G.812 Type IV SSU-B Sync. Supply Unit B = G.812 type VI SETS Sync Equipment Timing Source (SEC) SEC SDH Equipment Clock = G.813 opt. 1 SMC SONET Minimum Clock = G.813 opt. 2 ST4E Stratum 4E ST4 Stratum 4 DUS Don't Use for Sync DNU Do Not Use Option 1 = SDH, option 2 = SONET (USA) Source: ITU-T G Telecom Profile

22 Phase Synchronization

23 Phase Synchronization Until now, we ve mostly been talking about frequency now we add phase Frequency is just about oscillations phase is aligning those oscillations Two frequency signals which have constant phase offset are phase-locked and implicitly frequency syntonized Two timing signals with phases aligned and an offset is within defined limits are (phase) synchronized The most common way to carry phase across a wider network is with a packet-based approach, typically PTPv2 Hybrid mode: carry frequency with physical, phase with packet We ll include Time of Day (ToD) synch in this as well A B θ =phase offset of signal A relative to signal B

24 Phase Sources Two types: Phase and ToD Phase is transferred via 1 Pulse per Second (1PPS) Typically some form of SMA or Mini-DIN connector Also comes as an RJ interface combined with ToD Time (ToD) is transferred via an ASCII string set Much like NTP has used for ages (RS232, RS422) Different formats, commonly UBX, Cisco, NTP, NMEA Both (+ freq) available via integrated GNSS receiver Combined 1PPS and ToD Two pairs carry both signals 1PPS Input/Output Port Input/output of 1 pulse per sec ToD input ASCII strings carry date and time info GNSS Antenna GPS, Glonass, Compass,

25 Phase/Time Distribution: Packet Based Source ToD and 1PPS from time source Packet Timing Information Recovered ToD & phase (1PPS) Master Slave Master has timing inputs (ToD, 1PPS) and generates PTP packets Slave recovers/processes PTP packets & outputs time (ToD, 1PPS) Note: (S)NTP is the most widely used ToD distribution method

26 PTP Overview

27 What is Precision Time Protocol (PTP)? Precision Clock Synch. protocol for networked measurement & control systems PTP is, like NTP, a Two Way Time Transfer protocol (TWTT). IEEE 1588 has been originally specified because: Sub-microsecond (ns!) accuracy and precision (NTP normally low milliseconds) Frequency + Phase and Time Sync (increasing interest by Telecom Service Providers) Packet-based (replacing TDM) and basically Administration Free operation Accessible for both high-end devices as well as low-cost, low-end devices In band solution, i.e. doesn t necessarily require a separate clocking network Original IEEE 1588: to support timing in industrial automation (e.g. robots) IEEE : = V2 features added for WAN deployment introduced the profile for flexibility in other applications, such as SmartGrid, Telecom, etc

28 Standard IEEE Clocks Ordinary Clocks: Master and Slave Boundary Clocks Transparent Clocks Primary Reference Time Clock PRTC Ordinary Master PTP PTP Ordinary Slave BC Boundary Clock PTP TC Transparent Clock Recovered Clock

29 PTP Helper: Hardware Time Stamping Time stamping done as close to the wire as possible (support in MAC/PHY) Slave Master

30 PTP Boundary Clock A PTP aware node which is both a slave and a master Has at least 2 PTP ports, 1 slave port & 1 master (can dynamically swap) BC is used to clean up jitter, and reduce node latency & asymmetry Also necessary when the PTP transport is NOT a routed protocol (e.g. Ethernet) Master Clock PTP PTP Slave Clock BC PTP Boundary Clock

31 PTP Transparent Clocks Transparent Clocks help cancel queuing and processing delays

32 PTP Hybrid Clock(s) Clock Uses SyncE/TDM for Frequency, Packet for Phase A hybrid clock (Boundary or Slave) uses PTP only to recover time/phase It takes frequency from another source, typically SyncE or BITS Very stable in holdover, because the freq stability keeps the phase aligned Frequency Source Master Clock 1 option = In-band SyncE Slave Clock PTP Phase 2nd option = Sync input from freq. distribution network

33 PTP v2 Messages and Transmission Set of event messages: Sync Delay_Req Pdelay_Req (Peer to Peer case) Pdelay_Resp (Peer to Peer case) Events messages require timestamps general messages do not Mappings: L2 Ethernet, IPv4, IPv6, MPLS (others possible) Set of general messages: Announce Follow_Up Delay_Resp Pdelay_Resp_Follow_Up (P2P case) Signaling Management Transmission modes: either unicast or multicast (or can be mixed) Variable rates, timeout values, various TLVs and flexible TLV extensions

34 PTP Two-Way Time Transfer Protocol Can we open a PTP channel so you can give me time? Got your time, but how long was that message in transit? I know, I ll send a message and ask for a timed reply. Please reply to this message, I want to calculate the RTT. So transit was ½ round time trip delay (RTT) I can estimate my clock correction!! Signaling Announce Sync, Follow-up Delay- Request Delay- Response I m a top quality master clock It s beer o clock Ok, here s the time that packet of yours arrived

35 One-Step and Two-Step Clocks 1-step clock includes accurate timestamp (t 1 ) in Sync message 2-step clock sends accurate timestamp (t 1 ) in a Follow_Up message Slaves should interface with both one- or two-step masters Most of our Service Provider and Routing products are 1-step masters One-Step Two-Step

36 Two Step PTP Message Exchange Master time = T M Slave time = T S = T M + offset For your reference Time Values known by Slave Offset = T S - T M Delay Delay - Offset = B = t 4 t 3 Offset + Delay = A = t 2 t 1 t 2 = t 1 + Offset + Delay t 2 t 1, t 2 Delay t 4 = t 3 - Offset + Delay t 1, t 2, t 3 Delay = ((t 2 t 1 )+(t 4 t 3 ))/2 Offset = ((t 2 t 1 ) (t 4 t 3 ))/2 t 1, t 2, t 3, t 4

37 Best Master Clock Algorithm Selection by the Slave of the Best Master Clock Method by which each clock determines the best master clock in its subdomain out of all clocks it can see ensures best quality flows across timing domain BMCA is run locally on all ports of every OC or BC in a domain allows to continuously re-adapt to changes in the network and/or clock quality Port state can change between slave master under BMCA control Chooses best by comparing PTP Announce messages from masters: priority1: 128 grandmasterclockclass: 6 grandmasterclockaccuracy: The time is accurate to within 100 ns (0x21) grandmasterclockvariance: StepsRemoved: 0 TimeSource: ATOMIC_CLOCK (0x10) The method to select the best clock is usually specified in the PTP Profile

38 PTP Profiles IEEE is extensible through the concept of Profiles Profiles are used for a particular application area/network reference model: set of allowed Precision Time Protocol (PTP) features applicable to a device Typically defines clockclass values, TLV values, transport: IPv4/L2/IPv6, unicast/multicast, clock selection (BMCA), Domain #, packet rates, etc. ITU_T has defined one for frequency transport in mobile telecommunications G Telecom Profile (original Annexes J3 and J4 are known as default profiles ) There are others for some examples: C from IEEE for protection applications for power grids 802.1AS from IEEE for Audio-Visual Broadcasting SMPTE ST from Broadcasting for professional video

39 From Frequency to Phase

40 What s Changing? Before we had Frequency sync now we need Phase (and Time) One example: Tier-1 operators are increasingly rolling out LTE-A, TDD and SFN networks & adding advanced mobile services into their networks These networks and services require phase sync to work properly Phase requires much tighter network performance than frequency and over WAN networks, that could mean a packet-based distribution mechanism New performance requirements new standards, features, profiles, equipment Use new methods of packet distribution (L2 v L3, Multicast v Unicast) Requiring different performance characteristics (DPLL, Noise, etc) Combining SyncE with PTP, combining both with GNSS/GPS

41 Evolving Phase Requirements Application Frequency Network / Air Phase Requirement GSM, UMTS, W-CDMA 16 ppb / 50 ppb N/A LTE-Frequency Duplex 16 ppb / 50 ppb N/A LTE-Time Duplex 16 ppb / 50 ppb ± 1.5 μs ± 5 μs Notes No phase requirement for earlier cellular generations (except CDMA) 3 km cell radius >3 km cell radius LTE MBMS (FDD & TDD) 16 ppb / 50 ppb ± 10 μs Inter-cell time difference LTE-Advanced / 4G 16 ppb / 50 ppb ± 1.5 to 5 μs Depends on the application (below) Application LTE-A eicic (Enhanced Inter-Cell Interference Co-ordination) LTE-A CoMP (Co-operative Multi-Point operation) ± 1.5 to 5 μs Phase Requirements ± 1.5 to 5 μs (depends on technique)

42 Sync: What are our options? GNSS is a solution for frequency+phase sync, but has issues: Jamming and spoofing Antenna cost and siting issues Still requires a good local oscillator for short-term stability and long-term holdover Ownership/politics: remember 04:05 UTC 2 nd May, 2000? SyncE (or PTP) could transport frequency sync, phase requires PTP Cisco SP products (today) mostly support PTP for frequency ( Telecom Profile ) Now increasing requirements (e.g. mobile comms) for phase sync as well ITU_T has risen to the challenge and developed new standards to meet it

43 Sync: What are our options? Synchronization Option How Widely Used Robust Availability Robust Accuracy Cost Notes GNSS (GPS) Extremely Widespread Easily jammed, antenna and site costs PTP Growing Rapidly Network engineering needs to fix accuracy NTP Widespread V4 required for better accuracy, V3 common Over the Air (Radio) Not widespread No standard, Requires air I/F Atomic Clock Root of all today s clocks Expensive, needs alignment of phase

44 Standardization and Deployment

45 New Problems, New Solutions The ITU_T standards on frequency sync are long since implemented/deployed G.826x sets of standards (freely downloadable from the website) Now they define new profiles, architectures and clock types for phase: The process starts with the application, its requirements and budget Then, there is an architecture Also a model of the network and performance limits They must specify the clock types and their characteristics Finally a profile is defined to meet the application requirements and network constraints Defined for two cases: 1) with full on-path support 2) with partial on-path support First, lets look at the whole list of the phase standards

46 Models of Networks for Timing Transfer GM No timing support Full timing support Partial timing support Timing support means PTP-capable network devices in the path Support of PHY-layer frequency may or may not be there

47 Standards Overview (Phase) ITU-T SG15 Q13 Work Plan Definitions Terminology G.8260 Definitions Full on-path Support Active Standard Assisted Partial Support Under Construction Work item /Future Partial Support Basics G.8271 Network Requirements G Network PDV G G.8271.y Clock Models and Limits Methods G.8272 PRTC (+T-GM) G.8273 G.8275 G T-Grand Master (stand alone) G BC/Slave G BC/Slave G TC G A-PTS IEEE 1588 Profiles G Full Support G Partial Support G.8275.y

48 Phase Budget As an example of this process, we ll look at the budget Maximum Time Error 1100 ns!! A B N C D Application requirement GM Packet network Frequency and/or time reference(s) Packet Master Homework: Read G Packet Slave End Application(s)

49 PTP Profiles for Mobile M = Master, S = Slave BC = Boundary Clock T-BC = Telecom Boundary Clock T-GM = Telecom Grand Master T-TSC = Telecom Time Slave Clock IP Unicast, v4 mandatory, v6 allowed S PTP unaware backhaul network PTP processed only at each end, G Telecom Profile M Supported Ethernet Multicast T- TSC T-BC PTP aware backhaul network T-BC T-BC T-BC T- GM Coming PTP with full on-path timing support, G Telecom Profile IPv4 Unicast S PTP unaware G like BC PTP unaware G like M Draft PTP with partial timing support, G Telecom Profile

50 G Telecom Profile for Frequency The original profile by now widely deployed No on-path support (e.g. boundary and transparent clocks) because these are/were not generally available in existing networks. IPv4 was mandated as the network layer due to its ubiquity: and unicast was mandated in order to prevent multicast storms from slaves Announce message uses new clockclass values to map the Quality Level defined in G.781, to the physical equivalents in SONET/SDH and SyncE SSM Alternate BMCA (Best Master Clock Algorithm) was adopted with static local priority, allowing the synchronization flow to be planned and deterministic Port state statically configured: Master or Slave not dynamic IEEE Telecom Profile ICAP certification ensures protocol compliance!!!

51 G Full Timing Support Profile for Phase Just about everything that G isn t Full on-path support (e.g. Boundary clock) required at every hop in the network Ethernet multicast was the chosen distribution method (i.e. Layer 2) Uses two newly defined clock types: T-BC (Telecom Boundary Clock) and T-TSC (Telecom Time Slave Clock) Port state: Master or Slave can change dynamically (think: ring support) Requires physical frequency source (e.g. SyncE) in conjunction ( hybrid mode ) BMCA closer to the original IEEE 1588 approach some additional fields IEEE Telecom Profile ICAP certification process is coming for G

52 G Full Timing Support Profile for Phase Requires full timing support all network elements process the PTP messages Completed in association with (i.e. you need these as well): G.8272 (PRTC and PRTC+GM) G (Telecom BC and Telecom TSC) Network Limits defined in G Will be enhanced with: Stand alone T-GM G Transparent clocks G

53 PTP Profile Differences For your reference M = Master, BC = Boundary Clock TC = Transparent Clock, S = Slave T-GM = Telecom Grand Master T-TSC = Telecom Time Slave Clock Profile Name Original G Frequency G Phase Mapping Normally IPv4 IPv4 or IPv6 (L3) Ethernet (L2) Transport (M->S) Multicast (unicast option) Unicast Multicast Clock Types Ordinary (M, S), BC, TC NO BC T-GM, T-BC, T-TSC Negotiation Optional Yes No Packet Rates Fixed (negotiation option) Negotiated Fixed Redundancy (BMCA) Yes Alternate BMCA Yes Master Selection BMCA G.781-like alt-bmca Alternate BMCA clockclass values 1588 set G set Extended G set Define Local MC Priority No Yes Optional

54 G Partial Timing Profile for Phase Draft Same architectural view based on G.8275 Focus on architecture with no BC and one master for the 1 st version Requires only partial timing support from the network: PTP unaware network elements separated by T-BC s PTP messages mapped in IPv4 (same as G ) Completed in association with: G.8272 (PRTC) G (T-BC and T-TSC) updates and G (A-PTS) Might be better accepted by operators, but still some way off ratification

55 Summary of the Current Situation As we ve seen, there are two important Profiles for phase Profile to support Full On-Path Support : G , also including: G.8275 Architecture and requirements for packet-based phase sync G Network limits for phase sync in mobile backhaul packet networks supporting LTE TDD and some LTE-A services G Characteristics of new clock types required for G Profile to support Partial On-Path Support : G , (draft) and includes: G Characteristics of new clock types for Assisted Partial Timing support In summary: First one is being developed, tested, certified now Second one is still being worked on in the standards process

56 What about GNSS/GPS? Can we consider using GNSS/GPS? Nearly available everywhere, and provides all three synchronization types More than one: Glonass, Galileo, BeiDou-2/Compass, etc Very weak signal, e.g. GPS is >20,000Km = Femto-W E.g. a GPS disciplined oscillator can provide time accurate to within 100ns All GNSS very susceptible to jamming and increasingly, to spoofing Expensive to deploy cabling and antenna costs Satellite-Based Augmentation Systems: QZSS, EGNOS, GAGAN, WAAS, etc It s definitely got a place in the network design and sync architecture

57 Assisted Partial Network Timing Support Example: ITU-T G (Draft) PTP unaware GM PTP unaware PTP Node PTP unaware PTP Node PTP Node PTP Node Primary time source available at end slave Network-based timing as backup source for frequency* and/or time *Note: PHY-layer frequency support (i.e. SyncE) is an alternative.

58 Deploying Partial and Assisted Partial Use GPS as Primary Source have PTP available as a backup Many are investigating G full on-path support, today What if that s not possible? What if the network cannot support it? We have this resource above us we should consider it. Many are happy to go with GNSS/GPS, but need mitigation for its limitations So, the standards support assisted partial support: assisted = GNSS help Design calls for GNSS/GPS as a reference source, but PTP when it s out Lots of new product designs are going to feature integrated GPS receivers

59 Deploying PTP in Real Networks PTP CAN handle Asymmetry, but Assumed is that delays in each direction are symmetrical Beyond node error, there are link errors due to link asymmetry: fibre length, copper, lambdas, speeds, optical factors, PTP cannot measure asymmetry but if an asymmetry value is known it can be added to correctionfield and PTP can use it in its corrections First, the operator must first either estimate, or externally measure the link asymmetry for every path that could be used and configure PTP with it The values could change over time as well, so it might need redoing Obviously a slow/expensive (impossible?) task

60 A Few Rules to Understand PDV and Asymmetry are fatal to packet solutions for phase Engineering for Precise Time Synchronization is about Budgeting. Microwaves are terrible on both measures (unless they are a BC or a TC) Frequency source (e.g. SyncE) greatly improves PTP (Hybrid mode) SyncE greatly improves holdover performance when PTP is off Frequency sources are BITS/SyncE, Phase/time needs a GNSS as a source PTP is required to carry phase and time when no GNSS around PTP phase will need measurement/correction for phase offset ($$)

61 SP Routing Platforms Support For your reference Hardware ASR9000 RSP (not RSP2) & >2 nd Gen LC (Ironman) ASR903 ME3600X-24CX ASR901 ASR920 ASR920-M ME1200 Ethernet Traffic Interfaces Ethernet Traffic Interfaces Ethernet Traffic Interfaces Ethernet Traffic Interfaces Ethernet Traffic Interfaces Ethernet Traffic Interfaces 1PPS / ToD interfaces Input Yes + GNSS (New RSP) Yes Yes Yes Yes + GNSS No Clock Modes BMCA PTP Transport Options OC, BC, hybrid OC 1), BC, hybrid E2E TC OC 1), BC, hybrid E2E TC OC 1), BC, hybrid OC 1), BC, hybrid E2E TC OC 1), BC, hybrid E2E TC OC slave, BC, hybrid, E2E TC Default, Hot Standby 2), Hot Standby 2), Default 2), Hot Standby 2), Hot Standby 2), Default 2), Telecom 3) Telecom 3) Telecom 3) Telecom 3) Telecom 3) Telecom 3) Telecom 3) IPv4 Unicast Negotiation IPv4 Unicast 4) and Ethernet Unicast IPv4 Unicast 4) IPv4 Unicast 4) and Ethernet Multicast IPv4 Unicast 4) IPv4 Unicast 4) Negtn., IP IPv4 UC MC, L2 MC G Q1/ Q1/16 No 3.18 Q1/ Q1/ Q1/16 Q4/15

62 Platform Support 1) Master (grandmaster) and slave (slave-only); 2) for clock selection, the port state is either master or slave; 3) ITU-T G Telecom profile for frequency 4) For higher packet rates, reduce sessions in proportion For your reference ASR9000 ASR903 ME3600X-24CX ASR901 ASR920 ASR920-M ME1200 PTP HW Timestamp Yes Yes Yes No Yes Yes Yes Asymmetry Correction Currently not supported Manual / Automatic on Roadmap Manual / Automatic on Roadmap Manual / Automatic (not hybrid mode) Manual / Automatic on Roadmap Manual / Automatic on Roadmap Manual Transparent Clock Mode Currently not supported TC E2E L2/L3 for IPv4 TC E2E L2/L3 for IPv4 Not supported (HW) TC E2E L2/L3 for IPv4 TC E2E L2/L3 for IPv4 TC E2E & P2P P2P TC No No No No No No Yes BC # of Slaves with Announce Interval 2000 (16pps) max 32,000 pps 64 (64/64pps) 5) 64 (64/64pps) 5) 40 (64/32pps) 5) 64 (64/64pps) 5) 64 (64/64pps) 5) 20 (64pps) per LC 4)

63 Conclusion and Summary

64 Conclusion As new communications applications and methods arise, synch has increased in importance, and new requirements have only increased the challenge New standards have been developed for Telecoms, but these will flow through to many other industries that are facing similar challenges. Cisco and other Telecom Equipment makers are following these standards and rushing to implement them to help the operators service their customers

65 Further Resources Three YouTube videos explaining synch in far more detail (and time): Part 1/3: TDM and Packet-based Frequency Synch Part 2/3: IEEE 1588 and PTPv2 Part 3/3: Configuration of Clocking & Timing (for Cisco SP Access platforms) IEEE ICAP Certification page: ITU_T SG15

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67 Glossary 1DM: 1 (One)-way Delay Measurement 1PPS: 1 (One) Pulse per Second 3GPP: 3rd Generation Partnership Project (standards org) ACR: Adaptive Clock Recovery A-PTS: (1588) Assisted Partial Timing Support BC: (1588) Boundary Clock BITS: Building Integrated Timing Supply BMCA: Best Master Clock Algorithm CDMA: Cellular/Mobile Standard CEM: Circuit Emulation CERN: Org. Européenne pour la Recherche Nucléaire CoMP: Co-operative Multi-Point Operation (LTE term) DCF77: German Time Transmitter DPLL: Digital Phase-Locked Loop (timing device) EEC: (Synchronous) Ethernet Equipment (slave) Clock eicic: Enhanced Inter-Cell Interference Co-ordination (LTE) eloran: Enhanced LORAN (Navigation system) embms:enhanced MBMS (LTE version of MBMS) FDD: Frequency Domain Duplex GM: (1588) Grand Master GSM: Cellular/Mobile Standard GNSS: Global Navigation Satellite System GPS: Global Position System IEEE: Institute of Electrical and Electronics Engineers IRIG: Inter-Range Instrumentation Group ITU: International Telecommunication Union ITU-T: ITU Telecommunication Standardization IP-SLA: Internet Protocol Service Level Agreement L2, L3: Layer 2, Layer 3 (network architecture level) LTE: Long Term Evolution LTE-A: Long Term Evolution - Advanced MBMS: Multimedia Broadcast Multicast Services (3GPP) MEP: Maintenance association End Point (from Y.1731) MTIE: Maximum Time Interval Error μs: Micro (Mu) second NTP: Network Time Protocol OC: (1588) Ordinary Clock OTA: Over The Air (transfer via radio) PRC/PRS: Primary Reference Clock(SDH)/Source (ANSI) PPB: Parts Per Billion

68 Glossary PPM: Parts Per Million PRTC: Primary Reference Time Clock PTPv2: Precision Time Protocol V2 QL: Quality Levels QL-DNU: Quality Level - Do Not Use QL-DUS: Quality Level - Do not Use for Sync QL-EEC: Quality Level - Ethernet Equipment Clock QL-PRC: Quality Level - Primary Reference Clock QL-PRS: Quality Level - Primary Reference Source QL-SEC: Quality Level - Synchronous Equipment Clock QL-SMC: Quality Level - SONET Minimum Clock QL-SSU: Quality Level - Synchronous Station Unit QL-ST3: Quality Level - Stratum 3 QL-STU: Quality Level - Sync Traceability Unknown QL-TNC: Quality Level - Transit Node Clock SDH: Synchronous Digital Hierarchy SEC: Synchronous Equipment Clock SETS: Synchronous Equipment Timing Source SFN: Single Frequency Network (broadcasting) SONET: Synchronous Optical Networking SSM: Synchronization Status Messages SSU: Synchronization Supply Unit SyncE: Synchronous Ethernet T-BC: (1588) Telecom Boundary Clock T-GM: (1588) Telecom Grand Master T-TSC: (1588) Telecom Time Slave Clock TC: (1588) Transparent Clock TDD: Time Domain Duplex TDEV: Time Deviation TDM: Time Domain Multiplexed ToD: Time of Day TSC: (1588) (Telecom) Time Slave Clock TWAMP: Two-Way Active Measurement Protocol TWTT: Two-Way Time Transfer (protocol) UMTS: Cellular/Mobile Standard μs: Micro (Mu) second UTC: Coordinated Universal Time W-CDMA: Cellular/Mobile Standard WWVB: NIST Time Transmitter SSU: Synchronization Supply Unit XO: Crystal Oscillator

69 Thank you

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