Software outages are challenging even when baseline hardware redundancy is in place. A balance should be maintained when providing HA routing, otherwise router problems typically propagate not only throughout the service provider network, but also externally to other connected networks that potentially belong to other service providers. This could affect customers on a broad scale. The 7210 SAS-R6 and 7210 SAS-R12 devices support several software availability features that contribute to the percentage of time that a router is available to process and forward traffic.
All routing protocols specify minimum time intervals in which the peer device must receive an acknowledgment before it disconnects the session:
OSPF default session timeout is approximately 40 seconds. The timeout intervals are configurable.
BGP default session timeout is approximately 120 seconds. The timeout intervals are configurable.
Therefore, router software must recover faster than the specified time interval to maintain up time.