Foreword Network consolidation has been an industry trend since the turn of the century. Reducing capital investment by converging data, voice, video, virtual private networks (VPNs), and other services onto a single shared infrastructure is finan- cially attractive; but the larger benefit is in not having to maintain and operate multiple, service-specific infrastructures. Fundamental to network consolidation-- supporting a diverse set of services with a single infrastructure--is a common encapsulating protocol that accommodates different service transport require- ments.The Internet protocol (IP) is that protocol. Everything over IP Things move fast in the networking industry; technologies can go from cutting edge to obsolete in a decade or less (think ATM, frame relay, token ring, and FDDI among others). It is therefore amazing that TCP/IP is 35 years old and evolved from ideas originating in the early 1960s. Yet while the protocol invented by Vint Cerf and Bob Kahn in 1973 has undergone--and continues to undergo--hundreds of enhancements and one ver- sion upgrade, its core functions are essentially the same as they were in the mid 1980s. TCP/IP's antiquity, in an industry that unceremoniously discards technolo-