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NE40E V800R010C10SPC500 Feature Description - Network Reliability 01

This is NE40E V800R010C10SPC500 Feature Description - Network Reliability
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Inter-board Hot Backup

Inter-board Hot Backup

Basic Concepts

From a micro perspective, inter-board hot backup indicates the CPU backup between the master and slave service boards. From a macro perspective, inter-board hot backup indicates that a NAT device is equipped with multiple service boards where the master and slave service boards back up each other. Inter-board hot backup allows for a master/slave switchover upon a fault on the master service board, thereby ensuring data consistency and service continuity as well as preventing users from perceiving faults.

Backup Principles

Inter-board hot backup uses static configuration to determine the master/slave relationship between service boards. NAT session tables are established on the master service board, and service traffic is transmitted over the master service board only. Once the master VSUF-80/160 becomes faulty, the chassis detects the fault, and the interface board switches traffic to the slave service board.

Currently, inter-board backup includes the cold backup, warm backup, and hot backup modes. In comparison with cold backup and warm backup, hot backup has the following differences:
  • Hot backup

    The slave service board automatically synchronizes NAT sessions with the master service board, without requiring NAT sessions to be re-established during traffic switching. Figure 11-1 shows the internal processing path: multi-core CPU (maser) <-> TM (master) <-> SFU <-> TM (slave) <-> multi-core CPU (slave).
    NOTE:
    • Multi-core CPU: processes NAT information, including the public and private IP addresses, range of ports to be allocated, NAT source tracing logs, and session aging processing mechanism.
    • Traffic manager (TM): processes forwarding traffic on VSUFs and other related boards.
    • Switch fabric unit (SFU): provides data communication channels for all boards.
    Figure 11-1 Inter-board hot backup
  • Cold/Warm backup

    The slave service board does not synchronize NAT sessions with the master service board. When traffic is switched to the slave service board, NAT sessions need to be re-established. The re-establishment time is determined by the number of NAT sessions. Figure 11-2 shows the internal processing path: multi-core CPU (maser) <-> TM (master).
    Figure 11-2 Inter-board cold/warm backup

Troubleshooting Mechanism

Table 11-1 lists the comparison between cold backup, warm backup, and hot backup. Inter-board hot backup supports both centralized and distributed scenarios for rapid service recovery.

Table 11-1 Inter-board backup modes

Backup Mode

Applicable NAT Scenario

Service Running Scenario

Service Switching Scenario

Service Switchback Scenario

Inter-board cold backup

Centralized NAT

The master service board processes services, and the slave service board does not back up any tables.

When the master service board becomes faulty, user traffic is interrupted temporarily, and traffic is switched to the slave service board. A public IP address is re-allocated, and NAT sessions are re-established.

When the master service board recovers from the fault, it enters the delayed switchback phase, and NAT sessions are re-established.

Inter-board warm backup

Distributed NAT

The master service board processes services, and the slave service board backs up user table information in real time.

When the master service board becomes faulty, user traffic is interrupted temporarily, and traffic is switched to the slave service board. NAT sessions are re-established using the backed up user table information.

When the master service board recovers from the fault, it enters the delayed switchback phase, and user table information is backed up to the master service board. NAT sessions are re-established using the backed up user table information.

Inter-board hot backup

Centralized NAT

The master service board processes services, and the slave service board backs up user entries and NAT session table information.

When the master service board becomes faulty, user traffic is interrupted temporarily, and traffic is switched to the slave service board. The backed up user entries and NAT session table information are used.

When the master service board recovers from the fault, it enters the delayed switchback phase, and user entries and NAT session table information are backed up to the master service board. The backed up user entries and NAT session table information are used.

Distributed NAT
NOTE:

In centralized scenarios, two VSUF-80s/160s are deployed on a NAT device, and the CPUs of the two VSUF-80s/160s form the hot backup or cold backup relationships. In distributed scenarios, two VSUF-80s/160s are deployed on a BRAS, and the CPUs of the two VSUF-80s/160s form the hot backup or warm backup relationship.

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Updated: 2019-01-03

Document ID: EDOC1100055045

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