Data Network Design [3 ed.]

Design a successful data network with help from this definitive guide. Covering all the key processes and technologies -

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Data Network Design [3 ed.]

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Data Comrnunication: · Past to Future

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Data Network Design, Third Edition

his chap ter focu ses first o_n defin ing data netw ork desig n and identif.·yin.·g the need for a data com mun icati ons netw ork. We first turn our atten tion to a discu ssion of· the histo rical direc tions of com putin g and netw orkin g. Afte r desc ribin g mod ern day lega cy com mun icati ons, we expl ore the com putin g and netw ork~ g qirec fions that . will carry us thro ugh the first few deca des of the twen ty-fi rst centu ry. · A shor t revie w of rece nt late twen tieth cent ury histo ry show s a majo r ·sruft of · reso urce s (peo ple, syste ms, infra struc ture, and fund ing) away from voice and towa rds data com mun icati ons, as data traff ic volu mes far outp ace thos e of legac y voice. This ·acceleration is prec ipita ted by the infor mati on revo lutio n and an incre ased depe nden ce, from cons ume rs to the large st corp orati ons, upon data com mun icati ons. In this proc ess, we expl ore the worl d from the pers pect ive of the infor mati on tech nolo gy exec utive , network man ager , and engi neer , focu sing on legacy, matu re, and futur e techn olog ies with a view towa rd eme rgin g techn olog ies of the early twen ty-fi rst centu ry.

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WHAT IS NETWORK DESIGN? Netw ork desig n, spec ifica lly data netw ork design,· is a broa d field of stud y. It enco mpass es and inter acts with almQ§t ever y aspe ct of the busi ness and relies heav ily on its in_ tegr ation with t€~c hnol 0gy@ ata is defin ed as info- tmat ion fron:1:_~nlch conciusio_!Jr__ ,.ue 1_ra~n. D~f~-i~ft~n.u.s.e_d..in.tlJg_~Lu_ral t oyhis

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measured in$ per MB (hard drives are now measured in GBs). Desktop RAM was measured.in$ per MB. LAN bandwidth was measured in$ per Mbps, understan ding that it is mostly capital cost and wiring. WAN bandwidt h was measured in $ per Mbps per mile, and was the hardest to quantify since private line pricing is all across the board (we took averages); All of these costs decrease over time, but it can be seen that the cost of local storage is decreasing more rapidly than the cost of WAN bandwidth . The exponenti al increase in computin g speed and accessible memory is a well-established trend, driven by integrated circuit technolog y that will continue to extend well into the 21st century. Recent trends in processor and memory technolog y may even exceed exponenti al growth! Note that the cost of transmissi on is decreasing much slower than all other trends, and in some markets is increasing. The rapid drop in the cost of local storage has tracked to LAN bandwidt h, butnot WAN bandwidth , showing that the WAN is still the bottleneck. The vision of network computers running applicatio ns within the network and requesting applicatio ns on demand never materializ ed in force because the cost of local processing and storage dropped much faster than WAN bandwidth , and this trend is despite services like FR, ATM, IP VPNs, and even the public Internet.

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Power to the Desktop Obviously , one of the biggest trends influencin g the explosion of bandwidt h requirements and the subsequen t success of transport technologies like FR, ATM, and IP is the proliferati on of computing power to the desktop and its subsequen t use in distribute d computing . Personal computer and workstatio n processing power (MIPS, displayed to the user as MHz), memory size (once MB, now GB, and soon TB), and display size {Megapixels and now Gigapixels) are increasing at an exponentia l rate. This increase, coupled with an ever-incre asing need to interconne ct these desktops and laptops, is occurring at a rate faster than the computing performan ce metrics due to the acceleratin g bandwidt h principle. Personal computers (PCs) such as the Apple computer were born in "garage shops" and were initially looked at as toys for games and other amusemen ts. That has changed as the PC matured and had an even more powerful offspring referred to as a workstatio n. Workstati ons, also called clients or hosts, have now taken the premier position in the computin g industry as a requireme nt for every home user through corporate executive. From the PC's humble beginning s, as software applicatio ns were developed and speeds and memory increased while costs dropped, the larger computer manufactu rers began to notice PCs on the desks of us~rs who previously had a "dumb" terminal connected to the host. The personal computer was legitimize d by the IBM announce ment of its personal computer in 1983. In an ironic twist of fate, IBM attempted to set a proprietar y de facto industry standard by introducin g the micro-channel architecture, not making it open like the initial PC Industry Standard Architectu re (ISA). Soon after, several other manufactu rers surpassed IBM in PCmarke tshare, including the upstart garage shop Apple! Nowthe standard PC with the Microsoft Windows operating system is clearly the worldwid e standard of choice.

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Data .Communication: Past ta FutuPe

The PC has provided the user with the device for desktop access to the world of information. Mass storage of information has shrunk to a fraction of its original size and cost. Now the critical element is no longer hardware, but software. Indeed, the cost of software over the life of a modem PC can easily exceed that of the hardware investment. Since 1983, the PC has been the industry standard for corporate and government mi~ era-computi ng. Figure 1-15 shows the growth in the number of professional s using PCs. This trend has continued to the point where virtually every desktop has a personal computer, where mobile and wireless personal computing devices have gone beyond the laptop to the palmtop, and to Personal Digital Assistants (PDAs).

COMMUNICATIONS TECHNOLOGIES AS ENABLERS The applications driving the need for high-perform ance data communicat ions networksin particular, a high-bandw idth LAN and WAN-have already been reviewed. This section now explores technology that enables the business. Technology enablers take on many forms, from the need for higher speeds, increased flexibility, improved efficiency, and support for multiple traffic types to support required for entirely new applications. To under:.. stand where a technology is going and its short'" and long-term benefit to the user, you must first understand the S-curves of technological evolution and the phases by which it is accepted (or rejected) by users.

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