Precision Time Protocol Precision Time Protocol (aka IEEE1588)(aka IEEE1588)
TICTOC and PWE3
PWE3 WG IETF Prague 2007
Ron Cohen Resolute Networks
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AgendaAgenda
• IEEE1588/PTP Status• Protocol overview• Transparent clocks• TICTOC and PWE3
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The Precision Time Protocol (PTP)The Precision Time Protocol (PTP)
• PTPv1 published in 2002• Industries involved:
v1: Industrial Automation, T&M, Military, Power Generation and Distribution
v2 : Audio-Visio Bridges (802.1AS), Telecom and Mobile
• Symposia in 2003, 2004, 2005, and 2006. 2007 in Vienna• Products: Microprocessors, GPS Linked Clocks, Boundary Clocks,
NIC Cards, Protocol Stacks, RF Instrumentation, Aircraft Flight Monitoring Instruments, etc.
• Information: http://ieee1588.nist.gov• Version 2 PAR approved March 2005. Technical work
completed
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Protocol overviewProtocol overview
• Timing Protocol Align slaves to master time Measure delay between master and slave Measure per-link delay (v2)
• Synchronization Hierarchy ‘routing’ Protocol Automatic Best Master Clock Algorithm Determines the master-slave synchronization clock tree
hierarchy
• Management Protocol Configuration and performance monitoring
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PTP Master-Slave HierarchyPTP Master-Slave Hierarchy
*Clock symbols taken from ITU-T SG15 ‘synchronization modeling components – time’ contribution #249 Geneva-2007 by Mike Gilson of BT
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Timing Protocol OperationTiming Protocol Operation
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Peer Delay Measurement (Optional) Peer Delay Measurement (Optional)
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End-to-End Transparent ClocksEnd-to-End Transparent Clocks
E2E TCs cancel queuing and processing delays
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Peer-to-Peer Transparent ClocksPeer-to-Peer Transparent Clocks
P2P TCs cancel queuing, processing and propagation delays
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E2E TC Enabled PSNE2E TC Enabled PSN
Packet queuing and processing is removed
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P2P TC Enabled PSNP2P TC Enabled PSN
Topology change does not effect slave performance
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An application: Use of IEEE1588 for CESAn application: Use of IEEE1588 for CES
PEs use IEEE1588 clock as common reference
E1/T1 service clock delivered using differential timing
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PWE3 Architecture (single hop)PWE3 Architecture (single hop)
Properties
Emulates a native service
IWF implemented at Provider Edge
PSN is unaware
Service and PW is bidirectional
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PWE3 Architecture (multi-hop)PWE3 Architecture (multi-hop)
Properties
PW stitching used for to provide inter-provider services
PW stitching for in intra-provider network mainly in aggregation scenarios
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TICTOC propertiesTICTOC properties
IEEE1588 (and TICTOC in general)
Provides frequency and time services. Can be used for emulating existing services as well as enable new services
PSN can be unaware or can be enhanced by introducing boundary and transparent clocks
Timing and time services are mostly unidirectional, however the timing protocol is bidirectional
Timing and time services are required mostly within a single provider, from central locations to the provider edges
Delivering time and timing services between providers is of no interest
Boundary clock (or Transparent clocks) probably required for aggregation scenarios within a provider network
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SummarySummary
• There are commonalities and differences between PWE3 and TICTOC
• We should figure out the relationship between TICTOC and PWE3 in the following areas: PW architecture PW MIB PW signaling TICTOC protocol mapping to MPLS/L2TP
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