ISDN Protocol Administrator's and Developer's Guide ... - Intervoice

DPNSS 1 OverviewDPNSS 1 is primarily used between private branch exchanges (PBXs).The main components of DPNSS 1 are the network layer messages.These messages control all information that passes to and from a PBX.The 22 message types must contain specific information dictated by theprotocol.Table 6-1. DPNSS 1 Network Layer MessagesSymbol Message Type DescriptionCCM Call Connected Message This message indicates to the Originating PBX that the call has beenanswered by the called terminal, and that the speech or data phase canbe entered.CIM Clear Indication Message Used to acknowledge a CRM message.CRM Clear Request Message Initiates a clearing sequence.Each PBX in a multi-link call releases the connection, then repeats theCRM to the next link.A Clear Indication Message (CIM) confirms that the channel is nowfree.EEM(C)EEM(I)ERM(C)ERM(I)ISRM(C)End-to-End Message(Complete)End-to-End Message(Incomplete)End-to-End RecallMessage (Complete)End-to-End RecallMessage (Incomplete)Initial Service RequestMessage (Complete)Used only after the routing phase is complete. This message carriesforward and backward end-to-end information between originating,terminating, and branching PBXs.This message is also used to indicate the completion of an end-to-endsequence that was started with an EEM(I).Carries forward or backward end-to-end information betweenoriginating, terminating, and branching PBXs.The message is used when the 45 octets of an EEM(C) are not enoughto hold the supplementary information. The sequence started by anEEM(I) is completed by an EEM(C) unless the call is cleared in themeantime.Used by some supplementary services to establish a second call on thesame channel as an existing call.It contains the complete recall request and should not be followed byany SSRMs.Used by some supplementary services to establish a second call on thesame channel as an existing call.It can be used in place of an ERM(C) message. It is normally followedby at least one SSRM containing further selection information.Establishes a new call across the network.6-2 ISDN Protocol Administrator’s and Developer’s Guide 60001262, First Edition