IEEE 1588v2 Clock Synchronization

1
IEEE 1588v2 Clock Synchronization P2MP LSP
with co-routed reverse path

• Lizhong Jin (ZTE)
• Frederic Jounay (France Telecom Orange)

2
Requirement Analysis

• According to IEEE1588v2 (BC mode), the sync
  packet and delay request should follow the same
  path, with same transmission quality. The details
  are
• The forward and backward path should be same
• The QoS should be ensured for end-to-end packet
  transmission.
• It is preferred to do bandwidth usage
  optimization for sync packet transmission.
• MPLS network should provide all the above
  characteristics.

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Current Problem

• From the current deployment of IEEE 1588v2,
  because of the poor quality transmission provided
  by network, it was tested that about only 5 nodes
  are allowed between clock grandmaster and slave
  under the accepted accuracy of clock
  synchronization. (BC mode)

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Deployment with P2MP LSP with co-routed reverse
path
Processing clock sync between master and slave 1
Before sending ltdelay requestgt, delay for some
time according slave_id
Processing clock sync between master and slave 2
Before sending ltdelay requestgt, delay for some
time according slave_id
Sync packet Delay Request
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Solution Description

• The P2MP LSP has co-routed reverse path, and QoS
  reservation for both forward path and reverse
  path.
• Clock synchronization process
• Grandmaster will send IEEE1588v2 Sync to all
  Slave nodes through P2MP LSP with co-routed
  reverse path.
• When the slave node receive Sync packet, it is
  required to send delay request through P2MP LSP
  reverse path.
• In order to avoid some packet process collision
  on reverse path, an optimized method is
  (optional)
• When the slave node receive Sync packet, it is
  required to delay for sometime according to
  Slave_ID, then send delay request through P2MP
  LSP reverse path.
• The purpose of this method is to minimize
  potential packet process collision on reverse
  path.

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Solution Description (cont)

• P2MP LSP will provide the following functions
• Unidirectional point to multipoint connection
  from ingress LSR to all egress LSR
• Reverse path from egress LSR to ingress LSR,
  which has the same path from ingress LSR to
  egress LSR.
• Unidirectional point to multipoint LSP will
  provide Diff-serv TE.
• Reverse path LSP will provide Diff-serv TE.
• The QoS can only be guaranteed when only one of
  the egress LSR send packet through reverse path
  at one time.
• IEEE1588v2 will provide the following functions
• IEEE1588v2 will send same Sync packet to all
  slave node.
• When Slave receive the Sync packet, it is
  required to delay for sometime according to
  Slave_ID, then send Delay Request through reverse
  path. This is necessary so as to avoid all the
  slave node sending Delay Request through
  reverse path at same time.

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PROS CONS

• PROS
• The BW and EF resource is optimized by using P2MP
  connection.
• The number of nodes that between Grandmaster and
  slave is increased, by virtue of MPLS high
  quality packet transmission.
• More scalable.
• CONS
• If there is large number of nodes between
  Grandmaster and slave, the accuracy of clock
  synchronization will be poor. Hierarchy clock
  synchronization can be used to improve the
  accuracy.

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Next steps

• Add this requirements to draft-ietf-tictoc-require
  ments-00.

Thank you