1.1 Overview of the Manual

1.2 Supplementary Services and ISDN Variants

1.2.1 ETS 300 Variant

1.2.2 Q.SIG Variant

1.2.3 NI2 Variant

1.3 Supplementary Service Operation Summary

1.4 Supplementary Service Participants

1.5 Supplementary Services Under ETS 300

1.5.1 About the ETS 300 Variant

1.5.2 Subscription and Activation of Supplementary Services

1.5.3 Hold and Retrieve Services

1.5.4 Call Transfer Services

1.5.5 Call Forwarding Services

1.5.6 Advice of Charge

1.5.7 Call Identification Services

1.6 Supplementary Services Under Q.SIG

1.6.1 About the Q.SIG Variant

1.6.2 Using Supplementary Services

1.6.3 Tandem Services

1.6.4 Transfer Services

1.6.5 Call Forwarding Services

1.6.6 Call Identification Services

1.7 Supplementary Services Under NI2

1.7.1 About the National ISDN 2 (NI2) Variant

1.7.2 Using Supplementary Services

1.7.3 PRI Two B Channel Transfer

1.7.4 D Channel Identifier Request

1.1 Overview of the Manual

The NMS ISDN Supplementary Service Developer's Reference Manual describes ISDN supplementary services that can be accessed using NMS ISDN software. This manual provides:

• Background information about each available service, as it is defined in the specification for any applicable variants.

• A programming guide for NMS ISDN Messaging API applications.

• Documentation of a demonstration program included with the software.

This document is intended for developers of telephony and voice applications who are using Natural Access. This document defines telephony terms where applicable, but assumes that the reader is familiar with basic telephony concepts and the C programming language.

Although some introductory material is provided, this manual also assumes that the reader is familiar with the operation of basic ISDN supplementary services, as described in appropriate specifications.

ISDN supplementary services allow an NMS ISDN application to implement powerful functionality beyond basic call control. These functions include:

• Call transfer operations: an application can reroute a call to another user.

• Call forwarding operations: a network or ISDN stack can reroute a call destined for a user to another user.

• Call hold and retrieve services: an application can place a call on hold, and retrieve a held call.

• Advice of charge services: an application can track the costs of a specific call, in real-time.

• Tandem services: an application can support a transit node (one that exists between two other nodes, and route messages from one node to the other).

• Identification services: called or calling parties can exchange information.

• D Channel Identifier service: an application is able to obtain the PRI value assigned by the network.

Your NMS ISDN application can access supplementary services using the standard NMS ISDN Messaging API. Supplementary services messages are included in standard ACU messages sent to or received from the NMS ISDN protocol stack. Each service specification and any associated data is stored in an extended data area appended to the ACU message buffer. You can invoke supplementary services with any primitive passed over the ACU interface.

One primitive may contain multiple extended data structures. This allows the application to invoke multiple services with one primitive, or to receive multiple indications with one primitive coming up from the ACU interface.

1.2 Supplementary Services and ISDN Variants

ISDN supplementary services are implemented differently under various variants. NMS ISDN supports a subset of supplementary services in the three following variants:

• The Digital Signaling System No. One (DSS1) European Telecommunications Standard (ETS) produced by the Signaling Protocols and Switching (SPS) Technical Committee of the European Telecommunications Standards Institute (ETSI). In this document, this variant is referred to as the ETS 300 variant.
  For more detailed information, see Section 1.2.1, ETS 300 Variant.

• The Q.SIG signaling system for corporate networking. Q.SIG is standardized by a consortium of standards-producing bodies, including ETSI, the European Computer Manufacturer's Association (ECMA), and the International Organization for Standardization (ISO). The production effort is coordinated by the IPNS Forum. In this document, this variant is referred to as the Q.SIG variant.
  For more detailed information, see Section 1.2.2, Q.SIG Variant.

• The National ISDN Protocol specified by Telcordia (previously Bellcore). The National ISDN protocol was developed to be a common, vendor neutral protocol for North America that would enhance interoperability of equipment by replacing several proprietary vendor protocols. In this document, this variant is referred to as the National ISDN 2 (NI2) variant.
  For more detailed information, see Section 1.2.3, NI2 Variant.

1.2.1 ETS 300 Variant

The NMS ETS 300 variant implementation is a reference to the Digital Subscriber Signaling System No. One (DSS1) European Telecommunications Standard (ETS) produced by the Signaling Protocols and Switching (SPS) Technical Committee of the European Telecommunications Standards Institute (ETSI). The standard can be categorized as a basic Q.931 protocol with the addition of ASN.1 facilities to support ISDN supplementary services.

The following is a partial list of the documents describing supplementary services as they are implemented in the NMS ETSI supplementary service package:

• ETS 300 102-1 (1990): "Integrated Services Digital Network (ISDN) User- network interface layer 3; Specifications for basic call control."

• ETS 300 195-1: "Integrated Services Digital Network (ISDN); Supplementary service interactions; Digital Subscriber Signaling System No. One (DSS1) protocol; Part 1: Protocol specification."

• ETS 300 196-1 (1993): "Integrated Services Digital Network (ISDN); Generic functional protocol for the support of supplementary services; Digital Subscriber Signaling System No. One (DSS1) protocol; Part 1: Protocol Specification."

• ETS 300 207-1 (1994): "Integrated Services Digital Network (ISDN); Diversion supplementary services; Digital Subscriber Signaling System No. One (DSS1) protocol; Part 1: Protocol Specification."

1.2.2 Q.SIG Variant

Q.SIG specifications are produced by a consortium of standards-producing bodies, including ETSI, the European Computer Manufacturer's Association (ECMA), and the International Organization for Standardization (ISO). The production effort is coordinated by the IPNS Forum.

The NMS ISDN Q.SIG implementation is based on ETSI second-edition specifications. These were produced after ECMA-created standards (based on CCITT standards and enhanced by ECMA after a European Commission mandate to produce such standards) were submitted to the ISO/IEC.

The following table contains a partial list of standards documents that are relevant to the NMS ISDN implementation. Where two standards are listed, the first is the stage 1/stage 2 standard and the second is the stage 3 (Q.SIG) standard.

Q.SIG Service Name	Standard and Publication Date
	ECMA	ETSI	ISO/IEC
Basic Call (64kb/s unrestricted, 3.1kHz audio and speech bearer services)	ECMA-142/143, June 1990	ETS300 171/172, January 1993	IS 11574/11572 1994
Calling Line Identification Presentation	ECMA-148, June 19901	ETS300 173, December 1992*	IS 14136 1995*
Connection Line Identification Presentation	ECMA-148, June 1990*	ETS300 173, December 1992*	IS 14136 1995*
Calling/Connected Line Identification Restriction	ECMA-148, June 1990*	ETS300 173, December 1992*	IS 14136 1995*
Calling Name Identification Presentation	ECMA 163/164, March 1992	ETS300 237/238, June 1993	IS 13864/13868 1995
Connected Name Identification Presentation	ECMA 163/164, March 1992	ETS300 237/238, June 1993	IS 13864/13868 1995
Calling/Connected Name Identification Restriction	ECMA 163/164, March 1992	ETS300 237/238, June 1993	IS 13864/13868 1995
Generic Functional Procedures	ECMA 165, March 1992	ETS300 239, June 1993	IS 11582 1995
Call Forwarding Unconditional	ECMA 173/174, June 1992	ETS300 256/257, November 1993	IS 13872/13873 1995
Call Forwarding Busy	ECMA 173/174, June 1992	ETS300 256/257, November 1993	IS 13872/13873 1995
Call Forwarding No Reply	ECMA 173/174, June 1992	ETS300 256/257, November 1993	IS 13872/13873 1995
Call Transfer	ECMA 177/178, June 1992	ETS300 260/261, November 1993	IS 13865/13869 1995
Advice of Charge, Start of Call	ECMA 211/212, December 1994
Advice of Charge, During Call	ECMA 211/212, December 1994
Advice of Charge, End of Call	ECMA 211/212, December 1994

1 There is no stage 3 standard for this supplementary service. Q.SIG support for this supplementary service is covered by the basic call stage 3 standard.

In the ISO specifications, Q.SIG is referred to as Private Signaling System No. One.

The Q.SIG specifications identify different types of Private ISDN Network Exchanges (PINXs) and different supplementary services. This creates a conformance matrix.

Q Reference Points

The Q reference point is different than typical reference points, in that it describes the functions of a part of the network, rather than describing a point of interface to the network. The reference point location also implies that there is no user or network side of a connection. Rather, all Q.SIG signaling is symmetric between adjacent nodes.

1.2.3 NI2 Variant

The NMS NI2 variant implementation is a reference to the National ISDN Protocol specified by Telcordia. The standard can be categorized as a basic Q.931 protocol with the addition of ASN.1 facilities to support NMS ISDN supplementary services.

The GR-2865-CORE, Issue2 (1997): "Two B Channel Transfer (TBCT) Bellcore Generic Requirements" document describes supplementary services as they are implemented in the NMS NI2 supplementary service package.

1.3 Supplementary Service Operation Summary

The following table shows supplementary service operations, which variants those operations support, and which chapter of this manual contains more information on the operation:

Supplementary Service Operation	ETSI	Q.SIG	NI2	Documented in
Invoke Bridge Calls	-	X	-	Chapter 3
Invoke Call Hold	X	-	-	Chapter 4
Invoke Call Retrieve	X	-	-	Chapter 4
Notify Hold	X	X	-	Chapter 4
Notify Retrieve	X	X	-	Chapter 4
Explicit Call Transfer	X	-	-	Chapter 5
Notify Transfer	X	X	-	Chapter 5
Invoke Two B Channel Transfer	-	-	X	Chapter 5
Notify Two B Channel Transfer	-	-	X	Chapter 5
Invoke D Channel Identifier Request	-	-	X	Chapter 5
Invoke Call Diversion	-	X	-	Chapter 6
Activate Diversion	X	-	-	Chapter 6
Deactivate Diversion	X	-	-	Chapter 6
Enquire Diversion	X	-	-	Chapter 6
Remind Diversion	X	-	-	Chapter 6
Notify Diversion	X	X	-	Chapter 6
Invoke Call Deflection	X	-	-	Chapter 6
Activate Deflection	X	-	-	Chapter 6
Deactivate Deflection	X	-	-	Chapter 6
Advice of Charge Request	X	-	-	Chapter 7
Advice of Charge Inform	X	-	-	Chapter 7
Calling Name Identification Presentation (CNIP)	-	X	-	Chapter 8
Connected Name Identification Presentation (CONP)	-	X	-	Chapter 8
Calling Line Identification Presentation (CLIP)	X	X	-	Chapter 8
Calling Line Identification Restriction (CLIR)	X	X	-	Chapter 8
Connected Line Identification Presentation (COLP)	X	X	-	Chapter 8
Connected Line Identification Restriction (COLR)	X	X	-	Chapter 8

1.4 Supplementary Service Participants

Three parties are identified in the activation or invocation of a supplementary service:

• The served user: The user or node that activates or invokes the supplementary service. If the service is billable, then this is the user or node charged for it.

• The originating user: The user or node that originated the call into the network.

• The diverted-to user: In call forwarding services, this is the user or node to which the call is rerouted.

1.5 Supplementary Services Under ETS 300

This section provides an overview of the supplementary services available with the ETS 300 variant, and how these services operate in the network architecture.

1.5.1 About the ETS 300 Variant

ETS 300 specifications describe a protocol designed to access network services from an intelligent user terminal. The protocol is not symmetric. It requires two distinct roles, the user side and the network side. NMS ISDN supports both sides for basic call control. Supplementary services, at this time, have been implemented only for the user side.

Figure 1 shows a sample network and the points where an NMS ISDN ETS 300 supplementary service application can interface with the network. As shown in the figure, an NMS ISDN application written for the ETS 300 variant interfaces with the network on the user side of the S/T reference point of a CEPT E1 PRI ISDN trunk.

Figure 1. Network Diagram Showing Position of ETSI Application

Supplementary services over the T reference point are generally requests by the application for the network to do something on behalf of a subscriber or interface (for example, transfer a call).

1.5.2 Subscription and Activation of Supplementary Services

Under ETS 300, most supplementary services require subscription. Subscription services are optional services provided by the network operator on a provisioning basis. When the user requests network services from a provider, he/she also can optionally request one or more subscription services. The services are not available unless the interface is provisioned with them.

Note: Some supplementary services may not require subscription. For example, the Call Hold service may be generally available.

Under ETS 300, most supplementary services must be activated before they are used. Activation is the process of turning on a service at the network or stack level. Once a service is activated, the network, the stack and/or the application can invoke (use) the service when needed.

A supplementary service can be activated in at least one of the following ways:

• Some supplementary services are activated the moment they are subscribed to. The Remind Diversion service is one of these. To deactivate this service, the service provider must be contacted.

• Other supplementary services are activated or deactivated by the application as necessary. The Call Diversion service is an example: the application can activate it to configure the network to automatically forward a user's calls.

• Many supplementary services can be set up either way. For example, when subscribing to Advice of Charge (AOC) services, the user can specify that the service is active at all times. Alternatively, they can be configured so they are active only when the application requests an activation.

The act of using an activated supplementary service is called invocation of the service. In some cases, an application can automatically activate an inactive supplementary service by invoking it: the activation and invocation occur simultaneously. The Explicit Call Transfer service is an example: the application can invoke this service on a call-by-call basis.

1.5.3 Hold and Retrieve Services

An application on the user side of the S/T reference point may invoke Hold and Retrieve services on the network. When a call (identified by its connection ID) is placed on hold, the bearer channel (B channel) resource for the call is deallocated without losing the context of the call. The network side of the S/T reference point then reserves the B channel for allocation in a subsequent call offered by the user side.

The following hold and retrieve operations can be performed under ETS 300:

Operation	Usage
Invoke Call Hold	An application sends a request to the network to put a call on hold.
Invoke Call Retrieve	An application sends a request to the network to retrieve a held call.
Notify Hold	The network informs a party that it is on hold.
Notify Retrieve	The network informs a held party that it has been retrieved.

For more information, see Chapter 4.

1.5.4 Call Transfer Services

Call Transfer services allow an application at the user side of the S/T reference point to cause two existing calls to be joined together on the network side.

The following call transfer operations can be performed under ETS 300:

Operation	Usage
Invoke Explicit Call Transfer	An application sends a request to the network to join two existing calls.
Notify Transfer	The network notifies the joined users when a call has been affected by a remote transfer.

1.5.5 Call Forwarding Services

Under ETS 300, two types of call forwarding services are available: Call Diversion and Call Deflection.

Call Diversion is activated by the served user application on the network for all calls for a specific user or trunk. With this service active, the network reroutes calls addressed to a specific user or trunk, without consulting the user side of the S/T reference point. Three types of call diversion are supported: Call Forwarding - Unconditional, Call Forwarding - Busy, and Call Forwarding - No Response.

The following Call Diversion operations can be performed under ETS 300:

Operation	Usage
Activate Diversion	Activates Call Diversion on all calls on a user or trunk.
Deactivate Diversion	Deactivates Call Diversion on a specific user or trunk
Notify Diversion	When a diversion or deflection occurs, the network notifies the diverted-to user or trunk of the rerouting operation.
Enquire Diversion	The served user application can enquire the network, to learn the status of the Call Diversion service for a given user or trunk, or for all users/trunks.

Call Deflection can be activated for all calls, or activated on a call-by-call basis. When invoked, the served user stack (not the network) deflects (redirects) the call to a new destination. With this service, the user side can deflect a call to a different destination, without first answering it.

The following Call Deflection operations can be performed under ETS 300:

Operation	Usage
Activate Deflection	Activates Call Deflection for all calls on a specific trunk.
Deactivate Deflection	Deactivates Call Deflection on a specific trunk.
Invoke Deflection	Invokes Call Deflection on a specific call.

A special Remind Diversion service can also be activated (on a subscription basis) for an ETS 300 application. When a served user initiates an outbound call, the Remind Diversion service causes the network to remind the served user if Call Diversion has been activated for incoming calls.

1.5.6 Advice of Charge

Advice of Charge (AOC) provides the user with a way of tracking the costs of a specific call, in real time. Three separate AOC services are available, depending on when the application requires AOC information:

• AOC at start of call (AOC-S)

• AOC during the call (AOC-D)

• AOC at end of call (AOC-E)

The following Advice of Charge operations can be performed under ETS 300:

Operation	Usage
Advice of Charge Request	An application sends a request to the network to invoke Advice of Charge services for a specific call.
Advice of Charge Inform	This is invoked by the network to pass Advice of Charge information to the application.

1.5.7 Call Identification Services

The following identification services are implemented in NMS ISDN for the ETS 300 variant:

Service	Usage
Calling Line Identification Presentation (CLIP):	The called party receives the calling party's address information.
Calling Line Identification Restriction (CLIR):	Prevents the calling party's address information from being presented to called users.
Connected Line Identification Presentation (COLP):	Allows the calling party to determine the connected party's address information.
Connected Line Identification Restriction (COLR):	Restricts the calling party from determining the connected party's address information.

1.6 Supplementary Services Under Q.SIG

This section provides an overview of the supplementary services available with the Q.SIG variant and how these services are implemented in the network architecture.

1.6.1 About the Q.SIG Variant

Q.SIG specifications describe interactions between nodes in a Private ISDN Network (PISN). Each node is a Private ISDN Network Exchange (PINX). These nodes play identical roles in the network. Q.SIG is a symmetric protocol because there is no distinct user side and network side.

Figure 2 shows a sample Q.SIG network and the reference points where an NMS ISDN Q.SIG supplementary service application can join into the network. As shown in the figure, an NMS ISDN application written for this variant interfaces with the network at the Q reference point. The role of the application is to implement call control, and to control message exchanges at the reference point.

Figure 2. Network Diagram Showing Position of Q.SIG Application

Figure 3 shows the part of an NMS ISDN application that is the Q reference point.

Note: Application code related to local access (such as analog lines) is not considered part of the Q reference point.

Figure 3. Q Reference Point

Supplementary services over the Q reference point are generally requests sent by the application for services from another node in the network, or notifications that the local node has performed various services.

Note: If you are building a Q.SIG application, the PINX node address must be specified in your initial call to isdnStartProtocol. For more information, see Section 2.10.

1.6.2 Using Supplementary Services

Q.SIG applications provide supplementary services as part of their basic duties: the subscription concept has no meaning at this level. All supported services are activated at all times: a Q.SIG application need only invoke a service in order to use it.

1.6.3 Tandem Services

Tandem services support the transit node role. A transit node is an intermediate step in a call being set up through a network. A PINX may take on the responsibilities of a transit node during the call setup procedures, as a result of routing decisions, or it may happen as a result of supplementary service activation (such as call transfer). A transit node must maintain two separate basic calls, and additionally, combine the events from one call with actions on the other call.

NMS ISDN supports the Call Bridging tandem service. When this service is active, all notification and facility information elements are passed from one end to the other through the transit node. However, the application remains responsible for basic call control interaction. For example, the application must handle hanging up.

The Call Bridging service may be invoked in either of the following two ways:

• Explicitly, using the Invoke Bridge Calls operation.

• Implicitly when the Notify Transfer operation is called, and both transfer parties are remote. Implicit call bridging does not take place if one or both calls are local.

1.6.4 Transfer Services

NMS ISDN supports transfer-by-join operations between Q.SIG nodes. In a transfer-by-join operation, the two separate calls are connected through the local node. The local node is still involved in the call (the call is not rerouted).

To transfer a call under Q.SIG, the application must perform the switching required to connect calls together, using standard calls to the Natural Access Switching service. The application also invokes a Notify Transfer operation to notify each remote party that the transfer has taken place.

1.6.5 Call Forwarding Services

Under Q.SIG, Call Diversion supports Call Forwarding - Unconditional, Call Forwarding - Busy, and Call Forwarding - No Response.

The following Call Diversion operations are supported under Q.SIG:

Operation	Usage
Invoke Call Diversion	The served user node sends a request to the originating node to forward a call
Notify Diversion	The originating node notifies the diverted-to node that the call has been forwarded.

1.6.6 Call Identification Services

All of the call identification services for the ETS 300 variant (see Section 1.5.7) are also implemented for Q.SIG. In addition, the following Q.SIG-only identification services are implemented in NMS ISDN:

Service	Usage
Calling Name Identification Presentation (CNIP)	The called party receives the name of the calling party. Available only under the Q.SIG variant.
Connected Name Identification Presentation (CONP)	The calling party receives the name of the called party. Available only under the Q.SIG variant.

1.7 Supplementary Services Under NI2

This section provides an overview of the supplementary services available with the NI2 variant and how these services operate in the network architecture.

1.7.1 About the National ISDN 2 (NI2) Variant

NI2 specifications describe a protocol designed to access network services from an intelligent user terminal. The protocol is not symmetric, and requires two distinct roles, the user side and the network side. NMS ISDN supports both sides for basic call control, but NMS ISDN supplementary services only support the user side.

1.7.2 Using Supplementary Services

Under NI2, most supplementary services require subscription. Subscription services are optional services provided by the network operator by request. When you request network services from a provider, you can also request one or more subscription services. These services are not available unless the interface is provided with them.

Note: Some supplementary services may not require subscription. For example, the D Channel Identifier service may be generally available.

1.7.3 PRI Two B Channel Transfer

The Two B Channel Transfer (TBCT) service allows an application at the user side to request the transfer of two independent calls. To use the service, the user should be subscribed to TBCT.

The following table lists call transfer operations that can be performed under NI2:

Operation	Description
Invoke Two B Channel Transfer	The application sends a request to the network to transfer two independent calls.
Two B Channel Transfer Notification	The network notifies the application that the call previously transferred by TBCT has been cleared. To receive this notification, the user should be subscribed to the "Notification to Controller" feature.

1.7.4 D Channel Identifier Request

The D Channel Identifier service allows you to get the network-assigned value of a particular PRI. This value is unique within a given PRI serving group.