ISO/IEC 22535:2005

Information technology — Telecommunications and information exchange between systems — Corporate telecommunication networks — Tunnelling of QSIG over SIP

ISO/IEC 22535:2005 specifies tunnelling of "QSIG" over the Session Initiation Protocol (SIP) within a corporate telecommunication network (CN). "QSIG" is a signalling protocol that operates between Private Integrated services Network eXchanges (PINX) within a Private Integrated Services Network (PISN). A PISN provides circuit-switched basic services and supplementary services to its users. QSIG is specified in International Standards, in particular ISO/IEC 11572 and ISO/IEC 11582.

Technologies de l'information — Télécommunications et échange d'information entre systèmes — Réseaux de télécommunications "corporate" — "Tunnelling" de QSIG sur SIP

General Information

• Status: Withdrawn
• Publication Date: 19-May-2005
• Withdrawal Date: 19-May-2005
• ICS: 35.100.30 - Network layer
• Technical Committee: ISO/IEC JTC 1/SC 6 - Telecommunications and information exchange between systems
• Drafting Committee: ISO/IEC JTC 1/SC 6 - Telecommunications and information exchange between systems
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 25-Apr-2006

Relations

• Revised: ISO/IEC 22535:2006 - Information technology — Telecommunications and information exchange between systems — Corporate Telecommunication Networks — Tunnelling of QSIG over SIP
• Effective Date: 15-Apr-2008
• Consolidated By: ISO 1288-1:2016 - Glass in building — Determination of the bending strength of glass — Part 1: Fundamentals of testing glass
• Effective Date: 06-Jun-2022

Standards Content (Sample)

INTERNATIONAL ISO/IEC
STANDARD 22535
First edition
2005-05-01


Information technology —
Telecommunications and information
exchange between systems — Corporate
telecommunication networks —
Tunnelling of QSIG over SIP
Technologies de l'information — Télécommunications et échange
d'information entre systèmes — Réseaux de télécommunications
«corporate» — «Tunnelling» de QSIG sur SIP




Reference number
ISO/IEC 22535:2005(E)
©
ISO/IEC 2005

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ISO/IEC 22535:2005(E)
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©  ISO/IEC 2005
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ISO/IEC 22535:2005(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 2
3.1 External definitions. 2
3.2 Other definitions. 2
4 Abbreviations and acronyms. 3
5 Background and architecture . 3
6 Procedures. 5
6.1 General. 5
6.2 Encapsulation of QSIG messages in SIP messages . 5
6.3 QSIG SETUP message handling at an ingress gateway. 5
6.3.1 Sending a SIP INVITE request. 5
6.3.2 Receipt of responses to the INVITE request . 6
6.4 QSIG SETUP message handling at an egress gateway . 6
6.4.1 Receiving a SIP INVITE request. 6
6.4.2 Rejecting a QSIG message in an INVITE request . 7
6.5 Subsequent QSIG messages . 7
6.6 Terminating the SIP dialog. 7
7 Example message sequences . 8
7.1 Call establishment. 8
7.2 Call clearing. 9
7.3 Call establishment with m=0 in first SDP answer. 10
8 Security considerations. 10

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ISO/IEC 22535:2005(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO/IEC 22535 was prepared by Ecma International (as ECMA-355) and was adopted, under a special “fast-
track procedure”, by Joint Technical Committee ISO/IEC JTC 1, Information technology, in parallel with its
approval by national bodies of ISO and IEC.

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ISO/IEC 22535:2005(E)
Introduction
This International Standard is one of a series of Standards defining the interworking of services and signalling
protocols deployed in corporate telecommunication networks (CNs) (also known as enterprise networks). The
series uses telecommunication concepts as developed by ITU-T and conforms to the framework of
International Standards on Open Systems Interconnection as defined by ISO/IEC.
This International Standard specifies tunnelling of QSIG over the Session Initiation Protocol (SIP). This
enables calls between "islands" of circuit switched networks that use QSIG signalling to be interconnected by
an IP network that uses SIP signalling without loss of QSIG functionality.
This International Standard 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 JTC 1, ITU-T, IETF, ETSI and other
international and national standardization bodies. It represents a pragmatic and widely based consensus.

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INTERNATIONAL STANDARD ISO/IEC 22535:2005(E)

Information technology — Telecommunications and information
exchange between systems — Corporate telecommunication
networks — Tunnelling of QSIG over SIP
1 Scope
This International Standard specifies tunnelling of "QSIG" over the Session Initiation Protocol (SIP) within a
corporate telecommunication network (CN).
"QSIG" is a signalling protocol that operates between Private Integrated services Network eXchanges (PINX)
within a Private Integrated Services Network (PISN). A PISN provides circuit-switched basic services and
supplementary services to its users. QSIG is specified in Standards, in particular [1] (call control in support of
basic services), [2] (generic functional protocol for the support of supplementary services) and a number of
Standards specifying individual supplementary services.
NOTE The name QSIG was derived from the fact that it is used for signalling at the Q reference point. The Q
reference point is a point of demarcation between two PINXs.
SIP is an application layer protocol for establishing, terminating and modifying multimedia sessions. It is
typically carried over IP [4], [6]. Telephone calls are considered as a type of multimedia session where just
audio is exchanged. SIP is defined in [9].
Often a CN comprises both PISNs employing QSIG and IP networks employing SIP. A call can originate at a
user connected to a PISN and terminate at a user connected to an IP network or vice versa. In either case, a
gateway provides interworking between QSIG and SIP at the boundary between the PISN and the IP network.
Basic call interworking at a gateway is specified in [3]. Another case is where a call originates at a user
connected to a PISN, traverses an IP network using SIP, and terminates at a user connected to another (or
another part of the same) PISN. This document addresses this last case in a way that preserves all QSIG
capabilities across the IP network. It achieves this by tunnelling QSIG messages within SIP requests and
responses in the context of a SIP dialog.
The tunnelling of QSIG through a public IP network employing SIP is outside the scope of this specification.
However, the functionality specified in this specification is in principle applicable to such a scenario when
deployed in conjunction with other relevant functionality (e.g., address translation, security functions, etc.).
This specification is applicable to any interworking unit that can act as a gateway between a PISN employing
QSIG and a corporate IP network employing SIP, with QSIG tunnelled within SIP requests and responses.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
[1] International Standard ISO/IEC 11572 Information technology — Telecommunications and information
exchange between systems — Private Integrated Services Network — Circuit mode bearer services —
Inter-exchange signalling procedures and protocol (also published by Ecma as Standard ECMA-143).
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ISO/IEC 22535:2005(E)
[2] International Standard ISO/IEC 11582 Information technology — Telecommunications and information
exchange between systems — Private Integrated Services Network — Generic functional protocol for the
support of supplementary services — Inter-exchange signalling procedures and protocol (also published by
Ecma as Standard ECMA-165).
[3] International Standard ISO/IEC 17343 Information technology — Telecommunications and information
exchange between systems — Corporate telecommunication networks — Signalling interworking between
QSIG and SIP — Basic services (also published by Ecma as Standard ECMA-339).
[4] Postel, J., "Internet Protocol", RFC 791.
[5] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119.
[6] Deering, S., Hinden, R., "Internet Protocol, Version 6 (IPv6)", RFC 2460.
[7] Donovan, S., "The SIP INFO Method", RFC 2976.
[8] Zimmerer, E., Peterson, J., Vemuri, A., Ong, L., Audet, F., Watson, M. and Zonoun, M., "MIME media
types for ISUP and QSIG objects", RFC 3204.
[9] Rosenberg, J., Schulzrinne, H. et al., "SIP: Session initiation protocol", RFC 3261.
[10] Rosenberg, J., Schulzrinne, H. et al., "An Offer/Answer Model with the Session Description Protocol
(SDP)", RFC 3264.
[11] Rosenberg, J., "The Session Initiation Protocol (SIP) UPDATE message”, RFC 3311.
3 Terms and definitions
In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
"SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in [5] and
indicate requirement levels for compliant SIP implementations.
For the purposes of this document, the following definitions apply.
3.1 External definitions
The definitions in [1] and [9] apply as appropriate.
3.2 Other definitions
3.2.1
Corporate telecommunication Network (CN)
Sets of privately-owned or carrier-provided equipment that are located at geographically dispersed locations
and are interconnected to provide telecommunication services to a defined group of users.
NOTE A CN can comprise a PISN, a private IP network (intranet) or a combination of the two.
3.2.2
Egress gateway
A gateway handling a QSIG call or call-independent signalling connection established in the direction IP
network to PISN.
3.2.3
Gateway
An entity that behaves as a QSIG Transit PINX with QSIG carried over a circuit-switched link within a PISN on
one side and QSIG tunnelled over SIP within an IP network on the other side.
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ISO/IEC 22535:2005(E)
3.2.4
Ingress gateway
A gateway handling a QSIG call or call-independent signalling connection established in the direction PISN to
IP network.
3.2.5
IP network
A network, unless otherwise stated a corporate network, offering connectionless packet-mode services based
on the Internet Protocol (IP) as the network layer protocol.
3.2.6
Media stream
Audio or other user information transmitted in UDP packets, typically containing RTP, in a single direction
between the gateway and a peer entity participating in a session established using SIP.
NOTE Normally a SIP session establishes a pair of media streams, one in each direction.
3.2.7
Private Integrated Services Network (PISN)
A CN or part of a CN that employs circuit-switched technology and QSIG signalling.
3.2.8
Private Integrated services Network eXchange (PINX)
A PISN nodal entity comprising switching and call handling functions and supporting QSIG signalling in
accordance with [1].
4 Abbreviations and acronyms
CN corporate telecommunication network
IP Internet Protocol
PINX Private Integrated services Network eXchange
PISN Private Integrated Services Network
QSIG Signalling system for the Q reference point
RTP Real-time Transport Protocol
SDP Session Description Protocol
SIP Session Initiation Protocol
TCP Transmission Control Protocol
TLS Transport Layer Security
UA User Agent
UAC User Agent Client
UAS User Agent Server
UDP User Datagram Protocol
URI Universal Resource Identifier
5 Background and architecture
This document concerns the case of a call that originates at a user connected to a PISN employing QSIG,
traverses an IP network employing SIP, and terminates at a user connected to another (or another part of the
same) PISN. This can be achieved by employing a gateway at each boundary between a PISN employing
QSIG and an IP network employing SIP, as shown in Figure 1.
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ISO/IEC 22535:2005(E)

Figure 1 — Call from QSIG via SIP to QSIG
Each gateway can provide interworking as specified in [3]. This provides a basic call capability. However, [3]
only specifies interworking for QSIG basic call, as specified in [1]. Many of the other capabilities of QSIG
(support for supplementary services and additional network features) as specified in other standards and in
vendor-specific specifications are not covered. Some of these additional capabilities of QSIG are suitable for
interworking with SIP and might be the subject of future Standards or other specifications. Other capabilities of
QSIG are unsuitable for interworking with SIP because corresponding capabilities do not exist in SIP or are
achieved in ways that are incompatible with QSIG. Therefore interworking at a gateway between QSIG and
SIP will be limited to those QSIG capabilities that have sufficiently compatible equivalents in SIP. Each
capability requires special implementation in the gateway, and therefore a
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