As a result of the evolution of wire-speed layer-3 switching from enterprise networks to the core of public data networks, Packet Over SONET/SDH (POS) has emerged as the technology of choice for interconnecting high-speed backbone routers. POS is deployed in the line cards of Gigabit and Terabit routers and is implemented in hardware in order to handle wire speeds ranging from 155 Mb/s to 10 Gb/s. Introduction