This is a read-write text field, up to 32 characters, specifying a prefix used to match against incoming DNIS digits, which, when matched, causes the associated dialCtlPeerCfgInfoType to be used to discriminate the call as speech, data, fax, video, or modem. An admin configures this so the gateway can automatically classify and route incoming calls differently based on the dialed number pattern they arrive with. For example, calls arriving with a DNIS prefix reserved for a fax line would be classified and handled as fax traffic rather than voice, based on this configured prefix match.