Joint ITU-T/IEEE Workshop on Carrier-class Ethernet

Transcription

1 Joint ITU-T/IEEE Workshop on Carrier-class Ethernet Time Synchronization Protocols - Time & Timing Core to Edge Mike Gilson Lead Technical Consultant British s Plc, UK

2 Agenda Techniques & protocols for Time & Timing - Frequency & Time are interrelated The challenge facing carrier networks - TDM -> Packet based - Service mix Vs Network Requirements Options going forward & potential interaction - Range of Time Synchronization protocols - Physical layer & Packet based Solutions Work in the standards environment - ITU-T SG15 Q13 - IEEE, both 1588 & AVB - IETF TicToc Conclusions

3 Applications for Time & Timing Effective use of resources in space and time - Application->network, network->network, intra-network Applications - Fixed TDM (PDH / SDH replacement, within budgets) - Mobile FDD 50ppb, TDD 2.5µsec (Phase / Time alignment) Intra network uses - Billing, alarm, security, authentication - One way pkt delay time (measure order magnitude better) - SLA monitoring, - Determine link efficiency effectiveness, - Improve routing effectiveness 20C Network to 21C Network - Evolution from TDM to Packet based - CE / PWE support

4 Balancing Requirements Timing required at the Edge, Application or within the Network? Choices based on various factors - Reference generation, distribution technology & balance of implementation issues. These need to include, complexity and a trade between Performance Vs Risk. Primary Reference Clocks (PRC) Source of freq & time -Caesium -GNSS (i.e. GPS, Galileo, GLONASS etc) -Boundary Clocks Source Generation Distribution Fibre, copper, wireless Architectures -Core/Edge/Enterprise Technology -Ethernet (Sync or Native) -xdsl -xpon -Packet Based -TDM Sink Application App Requirements -Wireless (2G, 3G, LTE) -Fixed -Existing TDM -Voice end points -Boundary Clocks -AVB masters -etc

5 Pros & Cons of Protocol Techniques Pro Operation over native Ethernet / IP networks -reduce network complexity Processing power -huge gains available to optimise performance with high speed packet solutions Allow Transport of Frequency & Time - Limitation of existing TDM/SDH physical layer - only frequency transport Migration path 20C to 21C -Use of CE allows CPE reuse across NGN s Flexibility Con Disruption by packet impairments -Performance ->Impact varies -repeatability Packet overhead -e.g. 2MBit/s -> CE 6Mbit/s Network Assumptions -path is symmetrical -load / PDV Implementation at every node / equipment -appropriate silicon, complexity to embed Security of packet flow -replay, spoof etc

6 ITU-T SG15 Q13 The synchronisation question - Scope: Frequency, real time generation & distribution. Performance limits and implementation in the carrier scale environment. Key areas of work - G.8261 Synchronisation aspects in packet networks TDM over packet networks, Physical Layer Timing aka Synchronous Ethernet, provides limits Describes various techniques G.8261 is currently being revised - G.paclock Synchronous Ethernet Clock (based on G.813) - G.pacmod Timing & Time distribution, architectures Timescales - G.8261 Version 2 Feb G.paclock June G.pacmod Feb 2008 Development of profiles for packet based solutions - Architecture & performance of IEEE1588V2

7 ITU-T G.8261 Timing Techniques Network Synchronous -PSN Physical layer distribution -PSN/TDM only IWF PSN IWF CE IWF PSN IWF CE PRC PRC Timing within TDM end Systems & Networks Adaptive -Based on pkt rate / buffer fill CE IWF PSN IWF CE PRC PRC CE IWF PSN IWF CE Differential -Based on timing messages -Requires stable reference Time stamping techniques - One way or two way CE IWF PSN IWF CE PRC PRC IWF PSN IWF PSN=Packet Switch Network CE=Circuit Emulation / IWF=Inter-working Function Physical Layer Timing Flow Packet Flow

8 Physical Layer - Synchronous Ethernet Typical Clock Chain Physical Layer Timing Flow ETH Hybrid ETY G.813 SDH / SEC Physical Layer distribution of frequency -described in G.8261, G.paclock, G.pacmod Injection at the ETY layer bit stream not frame -Re-use standards functionality & thus existing building blocks Inter-connect / work with existing Synch architectures - Easier migration path -> possible Hybrid working G.paclock

9 IEEE Activities Solutions to specific problems IEEE1588V2 - Version 1 - Test & measurement heritage constrained high speed networks - Provide a time base Test & automation control - V2 migrating into WAN IEEE802.1AS Audio Video Bridging (AVB) - Consumer electronics and professional AV networks - Driven by consumer market demands - LAN type solution To get the best performance = Silicon in all the devices in the chain

10 IEEE1588V2 Two way time based protocol -determine frequency based on recovery of time - certain assumptions Symmetrical & Fixed (within limits) -implementation requires hardware changes -Physical layer frequency assist is possible with Synchronous Ethernet IEEE1588V2 -PTP Precise Time Protocol -Details the Protocol -IEEE802.1AS Audio Video Bridging (AVB) uses explicit 1588 profile -Expected approval 2007 Telecoms Profile required for carrier applications! -Architecture, performance etc

11 IEEE802.1AS Audio Video Bridging -video / audio streaming & content control - Native IEEE1588 profile Bridge enhancement -Support streaming QoS -2ms latency through 7 bridges -Admission control for guaranteed bandwidth -Precise timestamps for media co-ordination Reservation of resources Time Bound distribution -Digital Rights Mng (DMR) -Geographic bound -Assumed fixed & Symmetrical Network XX XX Clock / Time matching the listener buffers AVB Master Device #1 Device #2 Device #3 Streaming QoS only Guaranteed in cloud XX X X X X DD D D D D Time Bound Assumed to be fixed & symmetrical!

12 IETF - TicToc Additional work now being started by IETF 68 th IETF Prague TicToc BOF - TicToc - Timing over IP Connection and Transfer of Clock - Solutions to specific problems Currently developing WG charter - focus carrier or enterprise Network Timing Protocol (NTP) - Version 4 ready - Hardware based NTP time stamping Analysis and work on other protocols - Development of NTP version 5 analysis of Future protocol development beyond 1588 & NTPV4

13 Frequency & Time Relationship Frequency & time are related a resource! - Carrier - traditionally required frequency - IT / computer networks time converging Synchronous Ethernet Layer 1 - Can provide the frequency base in carrier scale networks IEEE1588V2 Layer 2 - Frequency & Time - Good frequency at the end points - Time lock quicker - Frequency base in native networks - limited Synchronous Ethernet & IEEE1588V2 - complementary in resolving frequency and time solution Network Timing Protocol (NTP) V4 & V5 - Ubiquitous layer 3 solution for Time based clients e.g. software only

14 Network & Resource Convergence Resource UTC UTC UTC UTC frequency UTC UTC frequency UTC UTC Network Network Network Network Network Network Carrier IT Carrier IT Platform Services Services Services Services Services

15 Scenarios Combining Physical & Packet Based Solutions Copper Fibre Wireless device Apps Push into core Native PTP SyncE Time & Frequency (lower quality across Native Ethernet) Frequency & Time PTP over Native Push to edge to trade off access impairment SyncE Frequency Core Edge

16 Possible Architectures Combined Frequency & Time Master Clock - PRC Synchronous Ethernet -frequency assist to Clocks (Time) -frequency to end devices / other SyncE PRC SDH SDH SyncE DD D D SDH DD D D DD D D AVB Domains PSN Core Based on Ron Cohen - Resolute presentation to IETF 68 TicToc March 2007

17 Conclusions Range of techniques available - Solutions should be seen as complementary - Resolving different time & frequency problems Large amount of work progressing across standards bodies - ITUSG15 Q13, IEEE, IETF - More inter working between bodies to gain best progress and not replicating work - Developing the integrated architecture going forward