JUNOS High Availability

Non-Stop Active Routing

Having a highly available routing node in the middle of your network running GRES with two REs is a great way to build a core infrastructure supporting seven 9s network uptime. The problem is that ensuring a zero-loss environment requires GRES to be supplemented with GR protocol extensions on all running protocols on all surrounding routers. This is easily done in the core network, where you have the control of platform selection, protocol support, and software version. However, that is not the case at the edge of the network, where you face customer-controlled devices. More often than not, you do not know the hardware type or software versions and protocol support of your customer peering routers. Moreover, even if you do know, you cannot control their hardware and software selection. Thus, you cannot rely on GR protocol extensions to integrate seamlessly into your node redundancy design with GRES.

A provider also cannot always rely on network-based availability by means of redundant network paths toward the customer. Often, the customer is dual-homed to different service providers for better redundancy. It is most likely that catastrophic events, such as a natural disaster, will not affect different service providers in the same manner. While one ISP might lose portions of its data center and upstream peerings, another ISP might be located far away from the disaster site and will be able to preserve all routing state with the rest of the Internet.

Additionally, ...