Cisco ASR1002 Network Positioning Guide - Page 26

PXE Data Elements Configuring the Routing Protocols Used for Network Proximity provider edge routers (PE) in AS1. PE-1 forms the PSA. PXE runs an IGP proximity algorithm and picks DCE-2 as the "closest" and returns the ranked list DCE-2, DCE-3, DCE-4. Figure 3: Data Center Selection by Network Proximity PXE Data Elements The PXE operations depend on these data elements: • PSA-Proximity Source Address. This is the source IP address of the end-user or client requesting proximity calculation for a set of target data center locations. • PTA-Proximity Target Address. This is the IP address of a given data center location. Proximity calculation is performed for a given PSA-PTA pair. • PTL-Proximity Target List. This is a collection (ranked or unranked) of PTAs. The conventional value for a PSA or PTA is an IP address/mask combination. Cisco NPS, PXE is expected to process IP addresses; therefore, outside of PXE, any other form of identifier must be converted to an IP address/mask. PXE Peering and Ranking The PXE peers passively with other routers in the network; that is, PXE only learns routes. PXE never injects any routes into the network. PXE fully participates in the appropriate IGP/EGP control plane operations. However, PXE uses learned routes only for proximity calculations and never interferes with the main router control plane routing information base (RIB). PXE maintains a separate copy of the RIB for this purpose. Cisco Network Positioning System Configuration Guide for the Cisco ASR 1000 Router, Release 1.0 20 OL-25794-01