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ME60 V800R010C10SPC500 Feature Description - WAN Access 01

This is ME60 V800R010C10SPC500 Feature Description - WAN Access

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The BGP non-stop routing (NSR) technique ensures the control plane connection to peers and uninterrupted traffic transmission on the forwarding plane if the BGP control plane fails because of active main board (AMB) failures.


Carriers have increasing demands for IP network reliability. Conventional non-stop forwarding (NSF) and graceful restart (GR) techniques cannot prevent traffic interruptions if a peer does not support GR or multiple peers fail simultaneously during a GR process. Traffic is interrupted temporarily before the GR process is complete because a GR-enabled router cannot obtain routing information from or establish control plane connections to its peers during the GR process.

NSR can be used to ensure uninterrupted traffic transmission and retain control plane connections if a software or hardware fault occurs on the control plane of a router. In addition, the fault is transparent to the control planes of its peers.

Related Concepts

  • High availability (HA): supports data backup between the AMB and standby main board (SMB).
  • NSR: allows a standby control plane to take over traffic from an active control plane if the active control plane fails, preventing the control planes of peers from detecting the fault.
  • NSF: enables a node to use the GR mechanism to ensure uninterrupted transmission during an AMB/SMB switchover.
  • AMB and SMB: run control plane processes.


BGP NSR implements synchronization of the following BGP data between the AMB and SMB to support NSR.
  • BGP forwarding entries

  • BGP control blocks


The AMB and SMB must be installed on an NSR-enabled node to support NSR.

The NSR process is as follows:
  1. Batch backup

    The AMB backs up BGP data in batches to the SMB immediately after the SMB starts.

  2. Real-time backup

    The SMB backs up BGP data in real time and receives packets with the AMB simultaneously.

  3. Switchover

    If the AMB fails, the SMB takes over services. The SMB retains uninterrupted operation of both the control and forwarding planes because data is synchronous between the AMB and SMB.


For details about NSR, see "Uninterruptible Service Technology" in Feature Description - Reliability.

Other Usages

An NSR device can function as a GR Helper. The GR Helper communicates with NSR-disabled devices and responds to peers' GR requests during an AMB/SMB switchover.

Usage Scenario

  • NSR is enabled on a node (for example, PE3 shown in Figure 9-30) with multiple links among which traffic is load-balanced. NSR helps to prevent traffic interruptions caused by a single point of failure. Figure 9-30 shows a typical networking for NSR application.
    Figure 9-30 Typical networking for BGP NSR application
  • NSR minimizes the impact of control plane faults and prevents route flapping on heavily loaded networks.


  • NSR ensures the uninterrupted operation of the forwarding plane and allows a standby control plane to retain connections between a local router and its peers if the local BGP control plane fails.
  • With NSR, BGP routers can work independently without the assistance of peers. Even though control planes of multiple BGP routers fail, NSR can still ensure the AMB/SMB switchover on each router.
Updated: 2019-01-04

Document ID: EDOC1100059473

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