SIST-TS ETSI/TS 102 037 V1.2.1:2005

• Abstract:

  This revision takes into account the recent development of H.323.

• Status: Published
• Publication Date: 28-Feb-2005
• ICS: 33.040.35 - Telephone networks
• Technical Committee: SPN - Services and Protocols for Networks
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Mar-2005
• Due Date: 01-Mar-2005
• Completion Date: 01-Mar-2005
• Ref Project: ETSI TS 102 037 V1.2.1 (2004-03) - Private Integrated Services Network (PISN); Mapping functions for the tunnelling of QSIG through H.323 networks

SIST-TS ETSI/TS 102 037 V1.2.1:2005 is the Slovenian adoption of ETSI TS 102 037 V1.2.1, a Technical Specification for mapping QSIG signalling through H.323 networks. It specifies how Private Integrated Services Network eXchanges (PINXs) use an H.323 packet network as the intervening network to carry inter-PINX signalling and user information. It is aimed at engineers, gateway designers, and conformance teams that need a defined way to connect parts of a Private Integrated Services Network (PISN) over H.323.

What does SIST-TS ETSI/TS 102 037 V1.2.1:2005 specify?

SIST-TS ETSI/TS 102 037 V1.2.1:2005 specifies mapping functions for using H.323 to interconnect two PINXs that belong to a PISN. The document covers how QSIG signalling is tunneled over the H.323 call signalling channel and how user traffic is carried over H.323 logical channels.

The standard is organized into scope, conformance, references, definitions, acronyms, an introduction to the reference configuration, capabilities at the Q and C reference points, mapping functions, IPC control procedures, and scenario-specific procedures.

Annex	What it covers
Annex A	Normative Implementation Conformance Statement (ICS) proforma used to state what an implementation supports
Annex B	Informative example message sequences for call setup and call clearing

The scope also draws a clear boundary around the model it uses. It covers H.323 as the intervening network for tunneling QSIG between PINXs, and it treats true QSIG-H.323-QSIG interworking as outside the document’s scope.

What are the key requirements of SIST-TS ETSI/TS 102 037 V1.2.1:2005?

The most important requirements are in the conformance clause, the mapping clauses, and the IPC control procedures. In practice, these clauses tell a PINX vendor what must be supported, how signalling is carried, and how calls are established and cleared.

• Conformance is based on Annex A. Clause 2 requires a conforming PINX to satisfy the items in the Implementation Conformance Statement (ICS) proforma. In practice, this means suppliers must declare which roles, scenarios, and protocol features their implementation actually supports.

• The Q reference point carries one D-channel and zero or more U-channels. Clause 7 defines the signaling channel for call control and the user channels for bearer traffic. For implementers, this means the PINX must support the signaling plane separately from the media plane and map each one correctly.

• The C reference point must support H.323, H.225.0, H.245, and protocol tunnelling. Clause 8 requires a packet-network interface suitable for H.323 multimedia communication and tunnelling according to H.323 annex M.1. Practically, this is the gateway-side capability that makes the whole model work.

• The D-channel is tunneled as a complete QSIG message with no segmentation. Clause 9.2 says the PINX embeds an entire QSIG message in the carrying H.225.0 structure and does not split it across messages. That matters because signalling must survive transport intact and in order.

• Each U-channel is mapped to H.323 logical channels. Clause 9.3 requires each user channel to be carried by a pair of unidirectional logical channels using RTP over UDP. In the on-demand case, clause 9.3.1 uses one fixed mapping per call; in the semi-permanent case, clause 9.3.2 allows channels to be opened and closed as needed. In practice, this tells the implementer how to build media paths and when to create them.

• Gatekeeper control is explicit when a gatekeeper is present. Clause 10.2 requires the PINX to register as a gateway, and clause 10.4.1 defines the admission procedure using ARQ and ACF messages. If there is no gatekeeper, clause 10.3 requires the PINX to know peer IP address information by configuration. This affects deployment planning and address management.

• Call establishment and clearing follow H.323 rules, with QSIG tunnelling layered on top. Clauses 10.4.2, 10.4.3, and 10.6 define outgoing setup, incoming acceptance, and clearing. The practical rule is simple: once an H.323 call carries the IPCs, the H.323 call must stay up only while the related PISN call still needs those IPCs.

• Scenario-specific behavior differs between on-demand and semi-permanent use. Clause 11.1 ties one H.323 call to one PISN call, while clause 11.2 allows one H.323 call to serve multiple PISN calls. That distinction matters when choosing whether the implementation is optimized for single-call setup or for carrying several calls over a persistent H.323 connection.

What terms does SIST-TS ETSI/TS 102 037 V1.2.1:2005 define?

The document defines the core network objects and roles used in the mapping model.

• PINX - A Private Integrated services Network eXchange, meaning the exchange that participates in a PISN and terminates the inter-PINX link.
• PISN - A Private Integrated Services Network, the private network structure that the document connects through H.323.
• IPL - An Inter-PINX Link, meaning the total signaling and user-information path between two PINXs.
• IPC - An Inter-PINX Connection, the connection provided by the intervening network between the C reference points.
• D-channel - The channel used for call control information between peer PINXs.
• U-channel - The channel used for user information between peer PINXs.
• Gatekeeper (GK) - The H.323 network element that handles registration and admission control when present.
• QSIG - The signaling system for the Q reference point that is tunneled through H.323 in this specification.

Who uses SIST-TS ETSI/TS 102 037 V1.2.1:2005?

SIST-TS ETSI/TS 102 037 V1.2.1:2005 is used by vendors and integrators building PINXs, H.323 gateways, and trunking gateways for enterprise telephony networks. It is also relevant to system designers who need to carry QSIG signaling across an H.323 packet network while keeping the PISN feature model intact.

Quality and conformance teams use Annex A to prepare an ICS and check which options are implemented. Test labs and interoperability engineers use the procedure clauses and the message examples in Annex B to validate setup, clearing, and signalling transport.

What changed in SIST-TS ETSI/TS 102 037 V1.2.1:2005 from the previous edition?

SIST-TS ETSI/TS 102 037 V1.2.1:2005 is fully compatible with the first edition. The brief history also states that this second edition gives more detail for one part of the optional semi-permanent scenario procedures.

Which standards are used with SIST-TS ETSI/TS 102 037 V1.2.1:2005?

The document relies on several referenced standards that supply the surrounding PISN and H.323 model.

• ECMA-133 - Provides the reference configuration for PISN exchanges and the Q and C reference points.
• ECMA-143 - Supplies the circuit mode bearer services and inter-exchange signaling procedures for QSIG-BC.
• ECMA-165 - Supplies the generic functional protocol for supplementary services and QSIG-GF procedures.
• ITU-T H.225.0 - Provides call signalling and media stream packetization for packet-based multimedia systems.
• ITU-T H.245 - Provides multimedia control procedures, including logical channel control.
• ITU-T H.323 - Defines the packet-based multimedia communications system used as the intervening network.
• ITU-T H.323 annex M.1 - Defines tunnelling of signalling protocols, including QSIG, in H.323.

What does the SIST-TS ETSI/TS 102 037 V1.2.1:2005 document contain?

SIST-TS ETSI/TS 102 037 V1.2.1:2005 contains the mapping rules, control procedures, and conformance material needed to implement QSIG tunnelling through H.323. The core body covers the reference configuration, the roles of the D- and U-channels, gatekeeper registration, call admission, call establishment, and call clearing.

Annex A contains the ICS proforma that implementers complete to declare support and optionality. Annex B contains worked message-sequence examples, including successful call setup in direct-call and gatekeeper-routed cases, and normal call clearing.

The figures in the document illustrate the IPL concept, the relationship between the PISN call and the underlying H.323 call, and the U-channel mapping procedures for the two scenario types. For implementers, those examples are mainly useful for protocol design, interop testing, and verification of call flow behavior.

SLOVENSKI STANDARD
01-marec-2005
Zasebno omrežje z integriranimi storitvami (PISN) - Funkcije preslikav za
tuneliranje QSIG skozi omrežja H.323
Private Integrated Services Network (PISN); Mapping functions for the tunnelling of
QSIG through H.323 networks
Ta slovenski standard je istoveten z: TS 102 037 Version 1.2.1
ICS:
33.040.35 Telefonska omrežja Telephone networks
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

Technical Specification
Private Integrated Services Network (PISN);
Mapping functions for the tunnelling of
QSIG through H.323 networks
2 ETSI TS 102 037 V1.2.1 (2004-03)

Reference
RTS/ECMA-00287
Keywords
H.323, PINX, QSIG
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ETSI
3 ETSI TS 102 037 V1.2.1 (2004-03)

Contents
Intellectual Property Rights.5
Foreword.5
Brief history.5
1 Scope.6
2 Conformance.6
3 References.6
4 Definitions.7
4.1 External definitions.7
4.2 Other definitions.7
4.2.1 Call.7
4.2.1.1 H.323 call.7
4.2.1.2 PISN call.7
4.2.1.3 Call segment.7
4.2.2 Channel.7
4.2.2.1 D -Channel .7
Q
4.2.2.2 U -Channel .8
Q
4.2.3 Inter-PINX Connection (IPC).8
4.2.4 Inter-PINX Link (IPL).8
4.2.5 PINX roles.8
4.2.5.1 Initiating PINX.8
4.2.5.2 Accepting PINX.8
5 List of acronyms.8
6 Introduction.8
6.1 Reference configuration.8
6.2 Specific scenarios.9
6.3 Relationship with H.323 gateways .10
7 Capabilities at the Q reference point .10
8 Capabilities at the C reference point .11
9 Mapping functions.11
9.1 General requirements.11
9.2 Mapping of the D -channel.11
Q
9.3 Mapping of the U -channel(s).12
Q
9.3.1 On-demand scenario.12
9.3.2 Semi-permanent scenario.12
10 IPC control procedures.12
10.1 Protocol identification.12
10.2 Registration with gatekeeper .12
10.3 Systems without gatekeeper .13
10.4 H.323 call establishment .13
10.4.1 Call admission.13
10.4.2 Outgoing call establishment.13
10.4.3 Incoming call establishment .14
10.5 Transfer of inter-PINX signalling information.14
10.6 H.323 call clearing .14
11 Scenario specific procedures .15
11.1 On-demand scenario.15
11.2 Semi-permanent scenario.15
Annex A (normative): Implementation Conformance Statement (ICS) Proforma.18
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4 ETSI TS 102 037 V1.2.1 (2004-03)

A.1 Introduction.18
A.1.1 Purpose of an ICS proforma.18
A.2 Instructions for completing the ICS proforma.18
A.2.1 General structure of the ICS proforma .18
A.2.2 Additional information.19
A.2.3 Exception information.19
A.2.4 Further indications of the ICS proforma tables .20
A.3 Identification of the implementation .20
A.3.1 Implementation Identification.20
A.3.2 Specification for which this ICS applies .20
A.4 General requirements.21
A.5 Procedures.21
A.6 Coding.22
Annex B (informative): Examples of message sequences.23
B.1 Successful call setup.23
B.1.1 Enbloc sending.23
B.1.2 Overlap sending.24
B.2 Normal call clearing.25
History .26

ETSI
5 ETSI TS 102 037 V1.2.1 (2004-03)

Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://webapp.etsi.org/IPR/home.asp).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This Technical Specification (TS) has been produced by ECMA on behalf of its members and those of the European
Telecommunications Standards Institute (ETSI).
Brief history
The present document is one of a series of ECMA standards defining mapping functions in exchanges of Private
Integrated Services Networks required for the utilization of intervening network scenarios. The series uses the ISDN
concepts as developed by ITU-T (formerly CCITT) and is also within the framework of standards for open systems
interconnection as defined by ISO.
The present document specifies mapping functions for the type of scenarios where two or more PINXs are
interconnected via on-demand connections using an H.323 packet network as the IVN.
The present document is based upon the practical experience of ECMA member companies and the results of their
active and continuous participation in the work of ISO/IEC JTC1, ITU-T, ETSI and other international and national
standardization bodies. It represents a pragmatic and widely based consensus.
The second edition is fully compatible with the first edition. It specifies one part of the procedures of the optional
semi-permanent scenario in more detail.
ETSI
6 ETSI TS 102 037 V1.2.1 (2004-03)

1 Scope
The present document specifies functions for using an H.323 packet network in order to interconnect two Private
Integrated services Network eXchanges (PINXs) forming part of a Private Integrated Services Network (PISN).
Interconnection is achieved by carrying the inter-PINX signalling protocol over the H.323 call signalling channel,
making use of the protocol tunnelling facilities of H.323, and inter-PINX user information (e.g. voice) over logical
channels established through H.323. Each logical channel usually represents a unidirectional media stream conveyed by
means of the Real-time Tranport Protocol (RTP). The inter-PINX signalling protocol is assumed to be QSIG, as
specified in ECMA-143 [2], ECMA-165 [3] and other standards.
The present document provides for an on-demand type of interconnection, where a separate H.323 call is established at
the start of each PISN call and cleared down at the end of that call. A semi-permanent scenario where a single H.323
call with an indefinite lifetime carries QSIG on behalf of many PISN calls is described as an additional option.
In the scenarios covered in the present document, the PINXs participating in a call are not necessarily aware of the
H.323 network providing the interconnection, and the features available are those of the QSIG network. This is different
from a scenario where true interworking between QSIG and H.323 (i.e. QSIG-H.323-QSIG) is used to connect two
PISNs or two parts of the same PISN. In this latter case all networks participate in a call on equal terms, and features are
limited to those available in all networks and supported by the gateways. This latter scenario is outside the scope of the
present document.
The present document is applicable to PINXs that can be interconnected to form a PISN using QSIG as the inter-PINX
signalling protocol.
2 Conformance
In order to conform to the present document, a PINX shall satisfy the requirements identified in the Implementation
Conformance Statement (ICS) proforma in annex A.
3 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
• References are either specific (identified by date of publication and/or edition number or version number) or
non-specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
[1] ECMA-133: "Private Integrated Services Network (PISN) - Reference Configuration for PISN
Exchanges (PINX)".
[2] ECMA-143: "Private Integrated Services Network (PISN) - Circuit Mode Bearer Services -
Inter-Exchange Signalling Procedures and Protocol (QSIG-BC)".
[3] ECMA-165: " Private Integrated Services Network (PISN) - Generic Functional Protocol for the
Support of Supplementary Services - Inter-Exchange Signalling Procedures and Protocol
(QSIG-GF)".
[4] ITU-T Recommendation H.225.0: "Call signalling protocols and media stream packetization for
packet-based multimedia communication systems".
[5] ITU-T Recommendation H.245: "Control protocol for multimedia communication".
ETSI
7 ETSI TS 102 037 V1.2.1 (2004-03)

[6] ITU-T Recommendation H.323: "Packet-based multimedia communications systems".
[7] ITU-T Recommendation H.323 annex M.1: "Tunnelling of signalling protocols (QSIG) in H.323".
4 Definitions
4.1 External definitions
For the purposes of the present document, the following definitions apply:
- Call independent signalling connection (ECMA-165 [3]);
- C reference point (ECMA-133 [1]);
- Gatekeeper (ITU-T Recommendation H.323 [6]);
- Gateway, Trunking Gateway (ITU-T Recommendation H.323 [6]);
- Intervening network (ECMA-133 [1]);
- Logical channel (ITU-T Recommendation H.323 [6]);
- Preceding PINX (ECMA-165 [3]);
- Private Integrated Services Network (ECMA-133 [1]);
- Private Integrated services Network eXchange (ECMA-133 [1]);
- Q reference point (ECMA-133 [1]);
- Subsequent PINX (ECMA-165 [3]).
4.2 Other definitions
4.2.1 Call
4.2.1.1 H.323 call
A call as defined in ITU-T Recommendation H.323 [6], i.e. a point-to-point communication between two H.323
endpoints. Here specifically a call in the H.323 network between two gateways.
4.2.1.2 PISN call
A call as defined in ECMA-143 [2] and ECMA-165 [3].
4.2.1.3 Call segment
A portion of a (PISN) call between two entities taking part in that call. The smallest segment is between adjacent
entities, e.g. between two PINXs across one Inter-PINX link.
4.2.2 Channel
A means of bi-directional transmission of user or signalling information between two points.
4.2.2.1 D -Channel
Q
A channel used to convey call control information between the Q reference points of two peer PINXs.
ETSI
8 ETSI TS 102 037 V1.2.1 (2004-03)

4.2.2.2 U -Channel
Q
A channel used to convey user information between the Q reference points of two peer PINXs.
4.2.3 Inter-PINX Connection (IPC)
A connection provided by an IVN between two C reference points used to transport inter-PINX information from the
PISN control plane and/or the PISN user plane.
4.2.4 Inter-PINX Link (IPL)
A link between the Q reference points of two PINXs, comprising the totality of signalling transfer and user information
transfer means.
4.2.5 PINX roles
4.2.5.1 Initiating PINX
The PINX that initiates an IPL establishment request.
4.2.5.2 Accepting PINX
The PINX that accepts an IPL establishment request.
5 List of acronyms
For the purposes of the present document, the following abbreviations apply:
GK Gatekeeper
ICS Implementation Conformance Statement
IP Internet Protocol
IPC Inter-PINX Connection
IPL Inter-PINX Link
IVN InterVening Network
PINX Private Integrated services Network eXchange
PISN Private Integrated Services Network
QSIG SIGnalling system for the Q reference point
RAS Registration, Admission and Status
RRQ Register ReQuest message
RTP/RTCP Real-time Tranport Protocol / Real Time Control Protocol
TCP Transmission Control Protocol
UDP User Datagram Protocol
6 Introduction
6.1 Reference configuration
ECMA-133 [1] defines a reference configuration for a PINX. Logically the switching and call control functions of a
PINX communicate over an instance of the Q reference point with a peer PINX. This communication is known as an
Inter-PINX Link (IPL) and comprises a signalling channel, known as a D -channel, and one or more user information
Q
channels, each known as a U -channel; see figure 1. One or more IPLs can be established between the same pair of
Q
PINXs.
ETSI
9 ETSI TS 102 037 V1.2.1 (2004-03)

PINX PINX
Q reference
Q reference
point
point
Switching
Switching
and Call
and Call
D -channel
Q
Control
Control
functions
functions
BQ-channel
B -channel
Q
Inter-PINX link
Figure 1: IPL concept
There are many ways of implementing an IPL. In general, the IPL uses services of another network, known as an
InterVening Network (IVN). A PINX interfaces to the IVN at the C reference point. The IVN provides connections,
known as Inter-PINX Connections (IPCs) between the C reference points of the peer PINXs. Mapping functions within
each PINX map the D -channel and the U -channels at the Q reference point onto one or more IPCs at the C reference
Q Q
point.
6.2 Specific scenarios
The present document specifies mapping functions for use when the IVN is an H.323 packet network that is used to
provide the following types of IPC:
• a signalling connection for carrying signalling information; and
• a pair of UDP streams, one stream in each direction, for carrying user information over RTP.
NOTE: Other means of transporting user information can be used, e.g. T.38 fax without RTP, an ATM virtual
channel, or a bi-directional TCP connection instead of UDP streams. See ITU-T Recommendation
H.323 [6] for more details. These cases are outside the scope of the present document.
A single IPL requires a single signalling connection, for support of the D -channel, and one pair of UDP streams per
Q
U -channel.
Q
The main inter-PINX connection scenario described in the present document is an on-demand connection scenario. This
means that an IPL is established whenever a PISN call segment is to be set up between two PINXs and released when
the PISN call ends. An optional semi-permanent scenario is also described, where multiple concurrent or consecutive
PISN calls can use the same IPL.
In both scenarios the signalling connection is established by means of an H.323 call, using the protocol tunnelling
facilities provided by ITU-T Recommendations H.225.0 [4] and H.323 annex M.1 [7]. The H.225.0 call signalling
connection in conjunction with the tunnelling of the QSIG signalling is used to provide the D -channel. The pair of
Q
UDP streams used to provide an inter-PINX user connection (U -channel) is established as H.323 logical channel(s).
Q
An IPL may have multiple U -channels.
Q
Figure 2 illustrates these concepts.
IVN (IP network using
PINX PINX
C reference
Q reference C reference Q reference
H.323)
point
point point point
Switching Mapping H.225.0 call Mapping Switching
signalling channel
and Call functions functions and Call
D -channel D -channel
Q Q
Control Control
functions functions
B -channel Pair of UDP streams B -channel
Q Q
B -channel Pair of UDP streams B -channel
Q Q
Inter-PINX connections
Inter-PINX link
Figure 2: H.323 as InterVening Network (IVN)
ETSI
10 ETSI TS 102 037 V1.2.1 (2004-03)

IPCs in support of these scenarios can be established and released at any time under the control of either PINX. In case
of IPC failure, the H.323 network may reject a call establishment request or release an already established call.
A single PINX can terminate a multiplicity of IPLs leading to the same and/or different peer PINXs. Each IPL
comprises a single H.323 call.
6.3 Relationship with H.323 gateways
Each PINX connected to another PINX via an H.323 network represents a trunking gateway in H.323 terms. The H.323
gateway functionality is part of the mapping functions of the PINX. No specific implementation is implied by the
present document. The gateway function may be fully integrated or decomposed into several components (e.g. media
gateway controller and media gateway), as explained in ITU-T Recommendation H.323 [6].
The tasks of the gateway include the handling of user data or media, e.g. packetization / de-packetization, and signalling
interworking. The latter mainly enables QSIG to be tunnelled over an H.323 call, as specified in more detail in
subsequent clauses.
Figure 3 shows an example of the relationship between a PISN call and the underlying H.323 call which provides the
inter-PINX link for one segment of the PISN call.
PINX PINX PINX PINX
Switching
Switching
and Call
and Call
PISN call
PISN call PISN call
Control
Control
segment
segment segment
functions H.323 functions
H.323
gateway
gateway
H.323 call
Figure 3: Example of the relationship between PISN call and H.323 call
7 Capabilities at the Q reference point
For each instance of the Q reference point:
• one signalling channel (D ) for carrying the inter-PINX Layer 3 signalling protocol; and
Q
• zero, one or more user channels (U )
Q
are provided.
NOTE: If the D -channel is used only to support QSIG call-independent signalling connections, no U -channels
Q Q
are required.
For a U -channel the following bearer capability shall be provided:
Q
• transfer mode: circuit mode;
• information transfer rate: 64 kbit/s;
• information transfer capability: speech or 3,1 kHz audio;
• user information layer 1 protocol: G.711 A or µ law.
Other bearer capabilities may also be provided (e.g. 64 kbit/s unrestricted digital information, or transfer rates other
than 64 kbit/s).
ETSI
11 ETSI TS 102 037 V1.2.1 (2004-03)

For a D -channel the following bearer capability shall be provided:
Q
• transfer mode: packet mode;
• information transfer rate: implementation-dependent;
• information transfer capability: unrestricted digital information.
The functions to map D - and U -channels to an Inter-PINX Connection (IPC) at the C reference point are described in
Q Q
clause 9.
8 Capabilities at the C reference point
A PINX shall support a packet network interface suitable for multimedia communication according to
ITU-T Recommendation H.323 [6]. The protocol stack shall conform to ITU-T Recommendations H.323 [6],
H.225.0 [4] and H.245 [5] and shall support protocol tunnelling according to ITU-T Recommendation H.323
annex M.1 [7].
NOTE: This means that the following protocols are used:
- H.225.0 RAS, if a gatekeeper is present, over UDP/IP;
- H.225.0 call control signalling, with embedded QSIG tunnel, over TCP/IP;
- H.245 within fastStart elements and/or embedded in H.225.0 call control or explicit over TCP/IP;
- RTP/RTCP over UDP/IP.
The protocol tunnelling capability of the H.323 call signalling channel serves as the IPC for the D -channel. A pair of
Q
H.323 logical channels for media transport serves as the IPC for a U -channel.
Q
For the on-demand scenario a new H.323 call is established every time a PISN call occurs and cleared when the PISN
call finishes.
For the optional semi-permanent scenario the same H.323 call serves multiple concurrent or consecutive PISN calls. In
this case logical channels are dynamically opened and closed according to the number of U -channels required at the
Q
time.
9 Mapping functions
9.1 General requirements
For each IPL terminating at a PINX, the PINX shall provide mapping functions for:
• mapping of the D -channel onto a packet mode IPC as provided by the H.323 call signalling channel with
Q
embedded QSIG tunnel;
• mapping of the U -channel(s) onto the corresponding IPC(s) with an information transfer rate of 64 kbit/s as
Q
provided by H.323 logical channels (pair(s) of UDP streams).
9.2 Mapping of the D -channel
Q
The signalling carriage mechanism (see clause 6.3 of ECMA-143 [2]) is provided by the protocol tunnelling facilities of
H.323. There is no layer 2 frame structure. The PINX shall embed a complete QSIG message in the appropriate data
structure of the transporting H.225.0 message without segmentation.
ETSI
12 ETSI TS 102 037 V1.2.1 (2004-03)

The services and primitives listed in ECMA-143 [2] clause 6.3 can be mapped to the sending and receipt of appropriate
H.225.0 messages. Details are left to the implementation.
9.3 Mapping of the U -channel(s)
Q
The PINX shall map each U -channel to a pair of unidirectional H.323 logical channels with suitable tr
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