7-6 Netopia ISDN Router Reference GuideCalling number authentication (CNA)Calling number authentication (CNA), an application of caller ID, is amethod of verifying that an incoming call is originating from theexpected site. Using CNA, you can increase the security of yournetwork by requiring that callers not only possess the correct PAP orCHAP information, but also that they are calling from a particularphysical location.CNA works by checking the calling number that the Netopia ISDNRouter receives during the initial setup phase of an incoming callagainst a set of stored numbers. Each number in the stored set isdefined in a specific connection profile. When a match occurs, theincoming call is handled by the connection profile containing thematched number.Using CNA can also provide cost savings because calls are notbilled during the CNA phase. With CNA, a caller can set up aconnection to the Netopia ISDN Router without incurring anycharges by accessing a dial-back connection profile. If the caller’srates are higher than those charged to the Netopia ISDN Router’sreturn call, then using CNA has saved the difference.CNA should be available where caller ID services are available, butconsult with your ISDN service provider to find out if your ISDN lineis provisioned for caller ID.Also note that if the calling side has instructed the phone companyto block delivery of its caller ID, the answering side will not be ableto authenticate.North American models If you have a Northern Telecom DMS-100 line (either custom or NI-1)you should verify that the line supports "Calling Number Delivery"service.If your line is an AT&T 5ESS (either custom or NI-1) verify that itsupports "CPN/BN (Calling Party Number/Billing Number) Delivery"service.If your line does not support the appropriate service, CNA may notwork properly.
