As end users and managers of both corporate and Internet service provider (ISP) IP networks, we ask a lot of those devices called routers. They must be reliable and easy to manage, while supporting a variety of LAN and WAN interfaces at a reasonable price. They must forward hundreds of thousands or even millions of packets per second. For each packet, this means the router receives it, extracts the destination address contained in the header, performs a lookup in a local routing table, finds the best match, and then transmits the packet to the next-hop router. The router may even be configured to examine additional fields in the packet and, based on this analysis, decide whether to place the packet in a high-priority transmission queue for expedited service. The author discusses link-state routing protocols.