BGP32S07L01.pptVIP

Optimizing BGP Scalability Improving BGP Convergence Outline Overview BGP Convergence BGP Processes CPU Effects of BGP Processes Improving BGP Convergence PMTU Discovery Increasing Input Queue Depth BGP Scan Time BGP Advertisement Interval BGP Nonstop Forwarding Awareness Summary BGP Convergence As the number of routes in the Internet routing table grows, the time it takes for BGP to converge increases. The Internet currently contains more than 110,000 prefixes. Network convergence times can range from 10 minutes to more than one hour. BGP is considered converged when: All routes have been accepted. All routes have been installed in the routing table. The table version for all peers equals the table version of the BGP table. The input queue and output queue for all peers is 0. BGP Processes BGP scanner and BGP router are responsible for a large number of calculations and can lead to high CPU utilization. BGP open As BGP control packets are received BGP scanner BGP router Process Description Interval Performs BGP peer establishment. Handles queuing and processing of BGP packets (updates and keepalives). At initialization, when establishing a TCP connection with a BGP peer BGP I/O Walks the BGP table and confirms reachability of the next hops. BGP scanner also checks conditional advertisement to determine whether or not BGP should advertise condition prefixes. Performs route dampening. Every 60 seconds Calculates the best BGP path and processes any route changes. It also sends and receives routes, establishes peers, and interacts with the routing information base (RIB). Once per second and when adding, removing, or soft-reconfiguring a BGP peer CPU Effects of BGP Processes BGP scanner process High CPU utilization stemming from the BGP scanner process can be expected for short durations on a router carrying a large Internet routing table. While the BGP scanner runs, low-priority processes need to wait a longer time to access the CPU. BGP router process The BGP route