Reliability Technologies
Network reliability can be improved by increasing the MTBF or reducing the MTTR. Faults caused by various factors are inevitable, so fault recovery technologies are important. The following reliability technologies are mainly used to reduce the MTTR and meet level 3 reliability requirements.
Reliability technologies fall into fault detection technologies and protection switching technologies.
Fault Detection Technologies
Fault detection technologies focus on fault detection and diagnosis. Table 1-2 describes the fault detection technologies.
Technology |
Description |
Link |
|---|---|---|
Bidirectional Forwarding Detection (BFD) |
BFD is a unified detection mechanism independent of media and protocols, and is used to rapidly detect link faults and monitor IP connectivity. |
|
Ethernet in the First Mile (EFM) |
EFM monitors network faults and is for use on last-mile Ethernet access links to users on the network. EFM needs to be enabled on the two directly connected devices so that EFM can monitor the link between the two devices. |
Protection Switching Technologies
Protection switching technologies focus on network recovery, and backs up hardware, link, service information, and routing information and perform fast switching to ensure service continuity. Table 1-3 describes protection switching technologies.
Technology |
Description |
Link |
|---|---|---|
Interface backup |
Interface backup ensures smooth services. When an interface on a router is faulty or bandwidth is insufficient, interface backup allows the router to quickly switch services on the faulty interface to other available interfaces. |
|
Graceful Restart (GR) |
GR ensures nonstop service transmission when IP/MPLS protocols such as BGP, IS-IS, OSPF, LDP, and RSVP-TE restart or an active/standby switchover occurs. Information such as routes is backed up and restored with the help of neighboring devices.
GR can be used for RIP, IS-IS, IS-ISv6, OSPF, OSPFv3, BGP, BGP4+, IGMP/MLD, PIM, MSDP, IPv4 L3VPN, RSVP, and LDP.
NOTE:
Only the AR2204XE, AR2204XE-DC, and AR2240C supports GR. |
For details about GR, see relevant protocols. |
Non-Stop Routing (NSR) |
NSR ensures nonstop service transmission when an active/standby switchover occurs. NSR backs up forwarding information such as IP/MPLS information from the active MPU to the standby MPU. When an active/standby switchover occurs, the forwarding
information can be backed up and restored without the help of neighboring devices. NSR can be used for IS-IS, IS-ISv6, OSPF, OSPFv3, BGP, BGP4+, IGMP/MLD, PIM, MSDP, IPv4 L3VPN, RSVP, and LDP.
NOTE:
Only the AR2240C supports NSR. |
|
Interface monitoring group |
After network-side interfaces are added to an interface monitoring group, the status changes of the network-side interfaces trigger the status of corresponding access-side interfaces to change. This, in turn, triggers an access-side active/standby switchover of access-side links. |
|
Virtual Router Redundancy Protocol (VRRP) |
VRRP is a fault-tolerant protocol that allows the device to provide the default link when the default becomes faulty on LANs with multicast or broadcast capabilities. VRRP prevents network interruptions caused by the fault of the single link. |
|
Hot standby backup (HSB) |
HSB provides a unified backup mechanism for service modules. When the master device becomes faulty, the backup device takes over services on the master service, which improves network reliability. |
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