Under the Hood of the Routing Engine
To utilize the robust high availability toolkit provided in JUNOS, one must fully understand the software components of the RE and how they work together to build a highly available operating system. As we discussed in Chapter 3, JUNOS provides a clear separation between the forwarding and control planes. This separation creates an environment in which the router can still forward the traffic when its control plane is down. As long as the traffic is actually flowing through the router, users do not experience any network-related issues.
The RE is the brain that stores the building blocks of system availability, providing all the necessary tools for routing protocols and route calculations. The main function of the RE is to perform route management, using a vastly modified Unix Routing Protocol Daemon (RPD). Because route management is a complex function, the RPD divides its work into many tasks and runs its own scheduler to prioritize them, ensuring that each protocol and route calculation receives the appropriate resources to perform its job.
The primary goal of the RPD is to create and maintain the Routing Information Base (RIB), which is a database of routing entries. Each routing entry consists of a destination address and some form of next hop information. RPD maintains the routing table and properly distributes routes from the routing table into the kernel and the hardware complexes used for traffic forwarding.
While almost all network equipment ...