Proving the Ideas

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Proving the Ideas

مُساهمة  صمت الحنين في الجمعة ديسمبر 21, 2007 1:25 am

Proving the Ideas
DARPA let three contracts to Stanford (Cerf), BBN (Ray Tomlinson) and UCL (Peter Kirstein) to implement TCP/IP (it was simply called TCP in the Cerf/Kahn paper but contained both components). The Stanford team, led by Cerf, produced the detailed specification and within about a year there were three independent implementations of TCP that could interoperate.

This was the beginning of long term experimentation and development to evolve and mature the Internet concepts and technology. Beginning with the first three networks (ARPANET, Packet Radio, and Packet Satellite) and their initial research communities, the experimental environment has grown to incorporate essentially every form of network and a very broad-based research and development community. [REK78] With each expansion has come new challenges.

The early implementations of TCP were done for large time sharing systems such as Tenex and TOPS 20. When desktop computers first appeared, it was thought by some that TCP was too big and complex to run on a personal computer. David Clark and his research group at MIT set out to show that a compact and simple implementation of TCP was possible. They produced an implementation, first for the Xerox Alto (the early personal workstation developed at Xerox PARC) and then for the IBM PC. That implementation was fully interoperable with other TCPs, but was tailored to the application suite and performance objectives of the personal computer, and showed that workstations, as well as large time-sharing systems, could be a part of the Internet. In 1976, Kleinrock published the first book on the ARPANET. It included an emphasis on the complexity of protocols and the pitfalls they often introduce. This book was influential in spreading the lore of packet switching networks to a very wide community.

Widespread development of LANS, PCs and workstations in the 1980s allowed the nascent Internet to flourish. Ethernet technology, developed by Bob Metcalfe at Xerox PARC in 1973, is now probably the dominant network technology in the Internet and PCs and workstations the dominant computers. This change from having a few networks with a modest number of time-shared hosts (the original ARPANET model) to having many networks has resulted in a number of new concepts and changes to the underlying technology. First, it resulted in the definition of three network classes (A, B, and C) to accommodate the range of networks. Class A represented large national scale networks (small number of networks with large numbers of hosts); Class B represented regional scale networks; and Class C represented local area networks (large number of networks with relatively few hosts).

A major shift occurred as a result of the increase in scale of the Internet and its associated management issues. To make it easy for people to use the network, hosts were assigned names, so that it was not necessary to remember the numeric addresses. Originally, there were a fairly limited number of hosts, so it was feasible to maintain a single table of all the hosts and their associated names and addresses. The shift to having a large number of independently managed networks (e.g., LANs) meant that having a single table of hosts was no longer feasible, and the Domain Name System (DNS) was invented by Paul Mockapetris of USC/ISI. The DNS permitted a scalable distributed mechanism for resolving hierarchical host names (e.g. www.acm.org) into an Internet address.

The increase in the size of the Internet also challenged the capabilities of the routers. Originally, there was a single distributed algorithm for routing that was implemented uniformly by all the routers in the Internet. As the number of networks in the Internet exploded, this initial design could not expand as necessary, so it was replaced by a hierarchical model of routing, with an Interior Gateway Protocol (IGP) used inside each region of the Internet, and an Exterior Gateway Protocol (EGP) used to tie the regions together. This design permitted different regions to use a different IGP, so that different requirements for cost, rapid reconfiguration, robustness and scale could be accommodated. Not only the routing algorithm, but the size of the addressing tables, stressed the capacity of the routers. New approaches for address aggregation, in particular classless inter-domain routing (CIDR), have recently been introduced to control the size of router tables.

As the Internet evolved, one of the major challenges was how to propagate the changes to the software, particularly the host software. DARPA supported UC Berkeley to investigate modifications to the Unix operating system, including incorporating TCP/IP developed at BBN. Although Berkeley later rewrote the BBN code to more efficiently fit into the Unix system and kernel, the incorporation of TCP/IP into the Unix BSD system releases proved to be a critical element in dispersion of the protocols to the research community. Much of the CS research community began to use Unix BSD for their day-to-day computing environment. Looking back, the strategy of incorporating Internet protocols into a supported operating system for the research community was one of the key elements in the successful widespread adoption of the Internet.

One of the more interesting challenges was the transition of the ARPANET host protocol from NCP to TCP/IP as of January 1, 1983. This was a "flag-day" style transition, requiring all hosts to convert simultaneously or be left having to communicate via rather ad-hoc mechanisms. This transition was carefully planned within the community over several years before it actually took place and went surprisingly smoothly (but resulted in a distribution of buttons saying "I survived the TCP/IP transition").

TCP/IP was adopted as a defense standard three years earlier in 1980. This enabled defense to begin sharing in the DARPA Internet technology base and led directly to the eventual partitioning of the military and non- military communities. By 1983, ARPANET was being used by a significant number of defense R&D and operational organizations. The transition of ARPANET from NCP to TCP/IP permitted it to be split into a MILNET supporting operational requirements and an ARPANET supporting research needs.

Thus, by 1985, Internet was already well established as a technology supporting a broad community of researchers and developers, and was beginning to be used by other communities for daily computer communications. Electronic mail was being used broadly across several communities, often with different systems, but interconnection between different mail systems was demonstrating the utility of broad based electronic communications between people
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صمت الحنين
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عدد الرسائل : 102
تاريخ التسجيل : 17/12/2007

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رد: Proving the Ideas

مُساهمة  admin في الجمعة ديسمبر 21, 2007 11:28 am

خيتووو لو كااان عملتي ترجمه لكاان فهمنا هههههههههه



الله يعطيكي العافيه صمت الحنين


تحياتي
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admin
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عدد الرسائل : 176
تاريخ التسجيل : 15/12/2007

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رد: Proving the Ideas

مُساهمة  صمت الحنين في الجمعة ديسمبر 21, 2007 11:45 am

أول شي الله يعافيك يا خيوووو وانا كاتبة الترجمة في مملكة الكمبيوتر والانترنت بعنوان موضوع الانترنت.....
ومرة تانية مغسي بوكوه على الردود الحلوة بتاعتكم تقبلوا مروري
صمت الحنين
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صمت الحنين
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عدد الرسائل : 102
تاريخ التسجيل : 17/12/2007

معاينة صفحة البيانات الشخصي للعضو

الرجوع الى أعلى الصفحة اذهب الى الأسفل

رد: Proving the Ideas

مُساهمة  ابن النصيرات في الأحد ديسمبر 23, 2007 10:54 am

اختي والله ما فهمت ولا كلمةيا ريت ترجمةتحياتي ابن النصيرات

ابن النصيرات

عدد الرسائل : 14
تاريخ التسجيل : 23/12/2007

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الرجوع الى أعلى الصفحة اذهب الى الأسفل

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