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IEEE 1588v2 Clock Synchronization & P2MP LSP with co-routed reverse path Lizhong Jin (ZTE) Frederic Jounay (France Telecom Orange) 1 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. 2 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) 3 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 4 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. 5 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. 6 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. 7 Next steps • Add this requirements to draft-ietf-tictocrequirements-00. Thank you 8