174 CHAPTER 6: DCC C ONFIGURATIONn To leave enough time for a server to call back, the interval between two calls onthe client need to be at least 10 seconds longer than that of the server. It isrecommended that the interval on the server be set to 5 seconds (the default) andthat on the client be set to 15 seconds.Configuring ISDN CallerIdentification CallbackIn an ISDN environment, implementing DCC callback through ISDN calleridentification function does not require authentication configuration.This section covers these topics:■ “Features of ISDN caller Identification callback” on page 174■ “Configuring ISDN caller identification callback with C-DCC” on page 175■ “Configuring ISDN caller identification callback with RS-DCC” on page 176Features of ISDN caller Identification callback1 In the applications of ISDN caller Identification callback, the callback server canprocess an incoming call in three ways, depending on the result of matching thedial-in number against numbers configured in dialer call-in commands at thelocal end:■ Deny the incoming call, if one or multiple dialer call-in commands exist, butno match is found.■ Accept the incoming call, if the call-in number matches a dialer call-incommand without the callback keyword or if no dialer call-in commandexists.■ Call back, if the call-in number matches a dialer call-in command with thecallback keyword.2 Dial-in numbers are matched against numbers configured in dialer call-incommands starting with the right-most character. In addition, asterisks (*) areused as wildcards to match any character. If a dial-in number matches multipledialer call-in commands, the best match is selected in the following order:■ The one with the fewest asterisks (*).■ The one that is found first.3 At the server end, identify the dialer call-in commands matching incoming calls■ In C-DCC, upon receipt of an incoming call, the server compares the incomingnumber against the dialer call-in commands configured on the physical dialinterface or its corresponding dialer interface for a match.■ In RS-DCC, upon receipt of an incoming call, the server compares the incomingnumber against the dialer call-in commands configured on the involved dialerinterface for a match.Configure a dial string forcallbackservice-type ppp[ callback-nocheck |callback-numbercallback-number |call-number call-number[:subcall-number ] ]RequiredWhen placing a return call,DCC identifies which dialstring to be used according tothe remote usernameobtained through PPPnegotiation.To do... Use the command... Remarks
