Network interconnection and gateways

Major technical issues for interconnecting computer networks that must be solved, which include selection of a protocol level at which to interconnect, addressing, routing, fragmentation, and congestion control, are discussed. Specialized gateway devices used to interconnect networks and implement any necessary internet protocols are examined. Two leading alternatives have been developed by the DARPA (Defense Advanced Research Projects Agency) Internet community (datagram internet protocol) and by the CCITT (International Telegraphy and Telephony Consultative Committee) for public data networks (concatenation of virtual circuits). The new ISO standards encompass both approaches, but providing interoperability between them is still a problem