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Precision Time Protocol over MPLS

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... as part of 802.1as 'Standard for Local and Metropolitan Area Networks - Timing ... Synchronization for Time-Sensitive Applications in Bridged Local Area Networks' ... – PowerPoint PPT presentation

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Title: Precision Time Protocol over MPLS


1
Precision Time Protocol over MPLS
  • draft-ronc-ptp-mpls-00.txt
  • PWE3 WG IETF Chicago 2007
  • Ron Cohen
  • ronc_at_resolutenetworks.com

2
Agenda
  • IEEE1588/PTP in a nutshell
  • Encapsulation
  • PTP LSPs
  • LSP Setup and Signaling
  • Open issues
  • Summary and Proposal

3
  • PTP in a nutshell

4
Protocol Operation
5
Protocol Operation (Cont.)
6
Main PTP Entities
7
Sync and Delay-Req formats
8
Encapsulations
  • PTP defined over
  • Ethernet
  • UDP/IPv4
  • UDP/IPv6
  • DeviceNet, ControlNet, IEC 61158
  • PTP is used as part of 802.1as "Standard for
    Local and Metropolitan Area Networks - Timing and
    Synchronization for Time-Sensitive Applications
    in Bridged Local Area Networks

9
  • PTP over MPLS Encapsulation

10
PTP MPLS Encapsulation
11
PTP MPLS Encapsulation
  • PTP header immediately follows PW label
  • Transport Specific Field set to zero for all PTP
    messages
  • Compliant with generic PW control word as
    specified in RFC4385
  • A PTP Forwarding Equivalence Class (FEC) is
    associated with the PW label
  • Benefits
  • Bandwidth efficient
  • Easy to identify PTP Event messages
  • Easy to process correction field in hardware

12
  • Tunnel and PTP LSPs
  • Scope limited to Point to Point LSP

13
Tunnel and PTP LSPs
  • Tunnel LSP switches MPLS tunnel labels
  • Tunnel LSP connects between PTP aware LSRs
  • E2E PTP LSP switches PTP/PW labels
  • E2E LSP connects between PTP ordinary and
    boundary clocks

14
Tunnel and PTP LSPs (Cont.)
  • Peer to Peer PTP LSPs connects between PTP peers
    for Pdelay Measurements only

15
Similarity to Multi-Segment PW
  • Transparent clocks behave somewhat similar to PW
    stitching
  • Manipulates the correction field of PTP messages
    In addition to PW label switching
  • Same administrative domain and PSN on both ends

16
PTP Entities
17
PTP Entities over MPLS
  • Communication Paths
  • A set of one or more E2E LSPs
  • Point to Point Communication Path or
  • Each ordinary or boundary clock port must form an
    PTP LSP with all non-slave-only PTP ports.
  • PTP domains
  • Different Domains are sent on separate PTP LSPs
  • PTP ports
  • PTP port used per E2E PTP LSP or
  • Single PTP port used for multiple LSPs

18
MPLS Communication Path Example
19
  • PTP LSP Setup and Signaling

20
PTP LSP Setup
  • Use LDP Extensions for setup of PWs (RFC3036)
  • Extended LDP discovery
  • Bidirectional LSPs setup
  • Downstream unsolicited label binding
  • Use Forwarding Equivalence Class (FEC) to
    identify the meaning of the label and identify
    the PW type
  • New FEC AII and AGI defined
  • Generalized PWiD (GID) FEC used
  • End-to-End or Peer-to-Peer PTP PW Types
  • Port Number and Clock Identity (Port identity)
    used as Attachment Individual Identifiers (AII)
  • Domain number used as Attachment Group Identifier

21
PTP FEC
22
  • Open issues and Next Steps

23
Open Issues
  • Traffic Engineering
  • Setup of symmetric LSPs
  • Use of RSVP-TE for tunnel LSP
  • Automatic Protection switching
  • Use of P2MP and MP2MP LSPs
  • FEC collision
  • Discovery and Aggregation Friendly AII types
  • LDP capability negotiation
  • PTP management messages

24
Summary and Proposal
  • PTP direct mapping to MPLS is required
  • PWE3 is the place to advance this work
  • Non-IP encapsulation over MPLS
  • Relevant experts and expertise
  • Suggest to add to PWE3 agenda
  • Possibly move to TICTOC if chartered
  • Coordinate with other WG if required
  • Suggest to adopt draft-ronc-ptp-mpls-00 as
    candidate for WG document

25
Thank You
  • Ron Cohen
  • ronc_at_resoluteNetworks.com

26
Multi-Segment PTP Scenario
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