Transcript IEEE 1588v2 Clock Synchronization over MPLS Networks

IEEE 1588v2 Clock Synchronization
&
P2MP LSP with co-routed reverse path
Lizhong Jin (ZTE)
Frederic Jounay (France Telecom Orange)
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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 corouted reverse path
Processing clock
sync between master
and slave 1
GrandMaster
Before sending <delay
request>, delay for
some time according
slave_id
R2
IP/MPLS
Processing clock
sync between master
and slave 2
R1
Slave_1
R3
Slave_2
P2MP LSP
P2MP LSP forward path
P2MP LSP reverse path
Sync packet
Delay Request
Before sending <delay
request>, delay for some
time according slave_id
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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-tictocrequirements-00.
Thank you
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