Mạng và viễn thông P29

Network Numbering and Addressing PlansThenetworknumbering or addressingplanis an important part ofthenetworkrouting plan, because the network address is the identification used by a caller to identify the customer or network port to which he wishes to be connected. Based on the network address, switched connectionswithinalltypesofnetwork are established.Inthischapterwediscussthefive basicnumbering and addressing schemes, and the principles that goalongwiththem
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Mạng và viễn thông P29 Networks and Telecommunications: Design and Operation, Second Edition. Martin P. Clark Copyright © 1991, 1997 John Wiley & Sons Ltd ISBNs: 0-471-97346-7 (Hardback); 0-470-84158-3 (Electronic) 29 Network Numbering and Addressing Plans Thenetworknumbering or addressingplanis an important part ofthenetworkrouting plan, because the network address is the identification used by a caller to identify the customer or network port to which he wishes to be connected. Based on the network address, switched connectionswithinalltypesofnetwork are established.Inthischapterwediscussthefive basicnumbering and addressing schemes, and the principles that goalongwiththem.These schemes are 0 international telephone service/ISDN numbering plan according to ITU-T recommendations E.163 and E.164 (recently combined into one recommendation, E.164) 0 international public data networknumberingschemeaccording to ITU-T recommendation x.121 0 international telex service numbering according to ITU-T recommendation F.69 0 addressing scheme for the message handling service (ITU-T recommendations X.500) 0 Internetaddressingscheme29.1 THE INTERNATIONAL TELEPHONE NUMBERING PLAN The international telephone numbering plan was originally defined in 1964 by ITU-T’s recommendationE.163,whichlaiddowntheprinciples of numberingpertinentto publictelephonenetworks.Itremainssubstantiallythesame,buthasrecently been combined with the subsequent recommendation E.164 ‘numbering for the ISDN era’ into a single recommendation E.164. Recommendation E.164 defines the recommended prefixes for international calls(00) and trunk calls (0), the allocation of country codes, and the maximum number length excluding international prefix (15 digits). Figure 29.1 illustrates an E. 164 number or network address. 513514 NETWORK NUMBERING AND ADDRESSING PLANS international country national significant number prefix code NSN 00 cc trunk area code + subscriber number 14 maximum 15 digits 4 - structure of an international teleohone number trunk national significant number prefix NSN 0 trunk area code + subscriber number structure of a national teleohone number Figure 29.1 E.164 format of international telephone numbers The E. 164 numbering plan ensures the allocation of a unique number (string of digits) to identify each individual telephone connected to the worldwide telephone network. line These numbers are analysed by telephone exchanges to determine the appropriate call routing and the appropriate call charging rate. Theydesigned to allow exchanges to are select an economical and satisfactory onward connection analysing only a minimum by number of digits.Therecommendationdoesnotcontroleachindividualcountry’s numbering plan, but allocates instead a large of numbers use in each individual series for national network. This flexibility allows each national network operator to prepare a national numbering plan, optimized for their own particular purposes. Most network operators choose to adopt a three-tier numbering plan. The three tiers correspond to overseas (i.e. international) calls, long distance (i.e. toll or trunk) calls and local calls, and the procedures for each of these types will be discussed in order. To place an international call over the automatic telephone network, a customer must dial first the international prefix code (to indicate that the digits immediatelyfollowing indicate a destination overseas). The next digits be a 1,2 or will 3-digit country code ( C C ) to indicate the particular country required, then the area code and destination cus- tomer number. Figure 29.1 illustrates the component parts an example international of number. The example of Figure 29.2 shows a London, UK, telephone number, when dialled from Switzerland. The ITU-T recommended international prefix ‘00’ is followed by country code digits ‘44’ to signify the United Kingdom, digits ‘171’ to identify Central London, digits ‘234’ to specify the destination exchangeand digits‘5678’ to earmark the customer. Successive ...