Data Communications Networking Devices - 4th Ed.pdf

10 _______________________________ FUNDAMENTAL WIDE AREA NETWORKING CONCEPTSWATSthe time of day a long-distance call is initiated and its destination intrastate orinterstate),discounts from normal long-distance tolls are available for selected callsmade without operator assistance.Introduced by AT&T for interstate use in 1961,wide area telephone serviceWATS) is now offered by most long-distance communications carriers. Its scopeof coverage has been extended from the continental United States to Hawaii,Alaska,Puerto Rico,the US Virgin Islands,and Europe,as well as selected Paci®cand Asian countries.Wide area telephone service WATS) may be obtained in two different forms,each designed for a particular type of communications requirement. OutwardWATS is used when a speci®c location requires placing a large number of outgoingcalls to geographically distributed locations. Inward WATS service provides thereverse capability,permitting a number of geographically distributed locations tocommunicate with a common facility. Calls on WATS are initiated in the samemanner as a call placed on the public switched telephone network. However,instead of being charged on an individual call basis,the user of WATS facilitiespays a ¯at rate per block of communications hours per month occurring duringweekday,evening,and night and weekend time periods.A voice-band trunk called an access line is provided to the WATS users. Thisline links the facility to a telephone company central of®ce. Other than costconsiderations and certain geographical calling restrictions which are a function ofthe service area of the WATS line,the user may place as many calls as desired onthis trunk if the service is outward WATS or receive as many calls as desired if theservice is inward. Inward WATS,the well-known `800' area code which wasextended to the `888' area code during 1996,permits remotely located personnel tocall your facility toll-free from the service area provided by the particular inwardWATS-type of service selected. The charge for WATS is a function of the servicearea. This can be intrastate WATS,a group of states bordering the user's statewhere the user's main facility is located,a grouping of distant states,orInternational WATs which extends inbound 800 service to the United Statesfrom selected overseas locations. Another service very similar to WATS is AT&T's800 READYLINE SM service. This service is essentially similar to WATS;however,calls can originate or be directed to an existing telephone in place of theaccess line required for WATS service.Figure 1.6 illustrates the AT&T WATS service area one for the state of Georgia.If this service area is selected and a user in Georgia requires inward WATS service,he or she will pay for toll-free calls originating in the states surrounding Georgia±Florida,Alabama,Mississippi,Tennessee,Kentucky,South Carolina,and NorthCarolina. Similarly,if outward WATS service is selected for service area one,aperson in Georgia connected to the WATS access line will be able to dial alltelephones in the states previously mentioned. The states comprising a service areavary based upon the state in which the WATS access line is installed. Thus,thestates in service area one when an access line is in New York would obviously differfrom the states in a WATS service area one when the access line is in Georgia.Fortunately,AT&T publishes a comprehensive book which includes 50 maps of