| Description: |
In 1981, Saltzer, Reed, and Clark identified "end-to-end" principles related to the design of modern layered protocols. The Internet started out as a network in which all "intelligence" was placed in the end-nodes (hosts), while the network is strictly concerned with the best-effort delivery of individual packets. To an application residing on several hosts the network is therefore "transparent" in that it has no effect on the application other than facilitating the delivery of information between the applications. The Internet today is not as transparent as Saltzer et al. had envisioned. While most of the intelligence remains concentrated in end systems, users and network * supported in part by a grant from NASA #NGT-30019 and the John Deere & Company 1 author for correspondence; contact information: hkruse1@ohiou.edu telephone/fax (740) 593-4891/4889 hardcopy mail J. Warren McClure School of Communication Systems Management, 9 South College Street, Room 197, Athens, OH 45701-2979 USA 2 Telecommunications Program within Department of Applied Computer Science, Email: wjyurci@ilstu.edu 3 Email: lessig@pobox.com 2 operators are now deploying more sophisticated processing within the network for a variety of reasons including security, network management, E-commerce, and survivability. For example end-users are deploying Network Address Translators (NATs) to circumvent problems related to IP address allocation, and firewalls and proxy servers for security at the interface between the user's network and the Internet. Network operators use packet filters and application level gateways to deal with security issues ranging from "spam" to denial of service attacks. In addition, network operators are deploying router software to enable differentiated levels of servi. |