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I TEROPERABILITY
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I FO MATIO PACKETAVAI
II of ur minar ar 0 nto th publi. Call for a frinformation pack t:
Aft r Sept. I, regist r on-sit bytaking this form to the generalpublic registration d k at thSan Diego Convention Cent r.Registration is open Sundaythrough Thursday.
by the Internet Engineering Ta k Forceand the Internet Architecture Board.Even if CIDR is adopted though, IP willhave to move to a wider space sooner orlater, and how to do so is the subject ofheated debate.
WAREGISTRATIOPr -regist r by Sept. I
and receive your badge in themail. No need to check inon-site, just walk right in. Complet the form below and nda ch kor money ord r for$20 payabl to the Tel Communications Association.
WHI=1U: TO IL
Mail this compl ted form andyour ch k to:
TCA Annual Confer nced. ui 102
COVina, CA 91724-3674o -SITE REGISTRATIO
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assignment of blocks of Class C addressesto a rvice provider, which then allocatesthem to an organization, a single prefix forthe service pro' r can be announced instead of lots of individual numbers.
CIDR is currently Wlder consideration
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OTE SPEAKER:Lt. General Thomas W. Kelly,Former Director of Operations,Joint Chi fs of Staff
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The most crucial issue in the Internet today twork nwnbers instead of a sin-is routing and addre ing. The combina . 8 address. Just giving lots of Classof not enough addresses and C addresses would ccmpound the rootingrouting tables are threatening to . table problems, so inter-d<xnain routing pro-the network. Here's a party ver- tocoIs would be modified to use variable-sion of the i ues inv eel. length network addresses. With inteDigent
The Internet PI: sa 32-bit r-'-------------------...-----------------------addre field, room for 4.2 billion address-es. You can't u aD potential addressesthough, or you don't have much of a net-
ork. Routing protocol are used by arouter to "armounce" to other routerswhich hosts can be. reached. If each nodegets a unique addres given out at random,like with Ethernet addresses, each hosthas to be individually announced and, in theworst case, routershave to schlepparound 4.2 billionroute announcements.
To avoid the problem of unmanageablerouting tables, the IPaddress is split into anetwork nwnberhost nwnber.of tellingabout available hosts,routers announce which networks th yknow about.
The trick is to balance the split between the network and host number . Ifthe network number uses a lot of bits,then you can have lot of networks, buteach 0 can ha e a' hosts. ForIP, the etwork Information Center assigns three classes, or types, of networkaddresses, Class A networks support 16million hosts, but the larg ho t pacemeans that there are only 126 a.V3lI:·able
Class A networks, of which 46 have already been assigned.
Class 8 networks support 65,534 ho ts.Because the network addre i larger,there are 16,256 po ible Cia 8 networks. Cia C networks support only 255hosts, but there are several million available Class C network nwnbers.
Here's the problem. Most networks are,or plan to be, bigger than 255 oodes. Everybody wants the flexblity of a Class 8 address, but there are 5,400 already a ignedand the figure is doubling every year,
Simple math shows that we will, givencurrent trends, run out of Class 8 spacesometime in 1993. Moreover, routing tables are g tting huge, with more than5,000 networks announced on the ationalScience Foundation' SF et baCJlbOIlle
A proposed solution is known asles Inter-Domain Routing (CIDR), Organizations would be allocated a block of
CARL MALAMUD is writing Exploringthe Internet: A Technical Travelogue, abook that will be featured as T1te lnteropBook at lnterop Fall. Tile opinions expressed are his own,
CheckR servtce No. 15
. July 20, 1992 Communications W