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MPLS-TP PWE3 dual-homed protection (MPDP)

MPLS-TP PWE3 dual-homed protection (MPDP). Speaker : Deng Hui (CMCC) . limitation of Linear Protection mechanism.

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MPLS-TP PWE3 dual-homed protection (MPDP)

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  1. MPLS-TP PWE3 dual-homed protection (MPDP) Speaker: Deng Hui (CMCC)

  2. limitation of Linear Protection mechanism • The linear protection mechanisms work within the PSN and provide fast recovery when link failure or P node failure occurs. However, Linear protection unable to protect against the failure of a PE node or the failure of an attachment circuit. For example: • Failure point ① can recovery by linear protection. • Failure ② and ③ can’t recovery by linear protecgion. PSN ① ② PE CE CE PE ③

  3. Requirements of dual-homed network topology ② ① PE1 • MPLS-TP network is often constructed by dual-homed topology to improve network survivability. • The operators need an end-to-end network’s survivability for guaranteed services, so the protection mechanisms for AC failure(③),PE failure(②) and failure within PSN(①) are all needed. ③ CE CE PE PSN PE2

  4. Limitation of PW redundancy ② ① PE1 • PW redundancy mechanism has introduced in RFC6718 to meet the requirment of dual-homed network topology. It provided a separate mechanisms to recover the PE and AC link failure from the PSN failure. • Failure ② ③: using PW redundancy mechanism. • Failure ①: using PSN protection mechanism(such as FRR, PSC, APS). • This separate mechanism raised the following issues: • longer recovery time, because hold-off time should be set to avoid race scenarios. • lower bandwidth efficiency because of multi-layer protections. • extra configuration makes the operation and maintenance more complicated. • the AC link failure will result in protection switching performed within PSN. ③ CE CE PE PSN PE2

  5. Multi-chassis PWprotection mechanism • PW protection in PE-3: Dual-homed PW protection mechanism keeps the same protection switching mechanism with linear protection in the Remote PE (PE-3). • MC-PW protection mechanism between PE-1 and PE-2: • ① Dual nodes interconnection (DNI) PW is set up between two dual-homed PE nodes, and it is used to bridge traffic when failure occurs. • ② Messages between two dual-homed nodes including “channel status notify message” and “protection group status notify message” are used to coordinate the multi-chassis PW protection. PE-3 PE-1 CE CE PE-2 PW protection(APS/PSC) MC-PW protection DNI PW

  6. Multi-chassis LAG protection mechanism PE-1 CE Ethernet port port PE-3 CE DRNI LAG DRCP port port Ethernet PE-2 • DRNI is used to protect Ethernet link failure between CE and PE and dual-homed node Failure on the CE side in dual-homed protection mechanism. • DRNI (Distributed Resilient Network Interconnect) and DRCP (Distributed Relay Control Protocol) is defined in IEEE P802.1AXREV-D2.2. DRNI expands the concept of Link Aggregation so that, at either one or both ends of a Link Aggregation Group, the single Aggregation System is replaced by a Portal, composed from one to three Portal Systems.

  7. Cooperation of MC PW protection and DRNI CE PE3 PE1 PW1 AC PW1 Service PW Cooperation state machine DNI-PW PE2 PW2 Service PW PW2 AC • In dual-homed PE nodes, the protection mechanism in PSN network(MC PW protection) and protection mechanism between PE and CE(DRNI) should cooperate to ensure an appropriate switch. • ①Service PW Status: Service PW is the PW which carry service between dual-homed PEs and remote PE and Service PW status is decided by MC PW protection mechanism. • ② AC status is the status of AC port between dual-homed PW and CE, being either active or standby. It is decided by DRNI mechanism.

  8. Cooperation state machine in dual-homed nodes • The principle of three point state machine in dual-homed nodes: • If AC status is active, establish connection from service PW to AC. If AC status is standby, establish connection from service PW to DNI PW. • If service PW is active, establish connection from AC to service PW. If service PW status is standby, establish connection from AC to DNI PW. • If service PW is active, establish connection from DNI PW to service PW. If service PW status is standby, establish connection from DNI PW to AC. • State transition of three point state machine in dual-homed nodes:

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