Advantages of Cisco NSF Variation Over IETF NSF

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NSF (Non-Stop Forwarding) is a feature in routing protocols that helps to minimize the impact of network outages and improve network availability. It allows a network device to continue forwarding packets while the routing protocol reconverges after a failure or a planned change. There are two variations of NSF: Cisco NSF and IETF NSF.

When enabling NSF for IS-IS, Cisco NSF has two advantages over IETF NSF, which are:

A. It does not rely on NSF-aware neighbors: With IETF NSF, the neighboring routers need to be NSF-aware for the feature to work properly. If a neighboring router does not support NSF, it may cause a routing protocol reconvergence, which could lead to a network outage. However, Cisco NSF does not rely on the NSF-awareness of neighboring routers. Therefore, even if a neighboring router does not support NSF, Cisco NSF can still help to minimize the impact of network outages.

B. It continues forwarding IP packets until route convergence is complete: With IETF NSF, the forwarding of IP packets stops as soon as a switchover occurs, and the new active router begins the routing protocol reconvergence process. As a result, some packets may be dropped, and applications may experience disruption. However, with Cisco NSF, the active router continues forwarding IP packets until the routing protocol has completely converged. This ensures that there is no disruption to the network during the reconvergence process.

C. It provides NSR in addition to NS: NSR (Non-Stop Routing) is a feature that allows a network device to maintain its routing state during a switchover from the active to the standby router. This helps to minimize the impact of network outages and improve network availability. Cisco NSF provides both NSR and NS (Non-Stop Forwarding) capabilities, while IETF NSF only provides NS capabilities.

D. NSF-capable router receives the adjacency and link-state information from NSF-aware neighbors: NSF-capable routers can receive adjacency and link-state information from NSF-aware neighbors during a switchover. This helps to reduce the time it takes to reconverge the routing protocol and minimize the impact of network outages. However, this advantage is not specific to Cisco NSF and is also available in IETF NSF.

E. It allows the standby RP to take control of the device after a hardware or software fault on the active RP: In a redundant system with a standby RP (Route Processor), Cisco NSF allows the standby RP to take control of the device after a hardware or software fault on the active RP. This helps to minimize the impact of network outages and improve network availability. However, this advantage is not specific to Cisco NSF and is also available in IETF NSF.