EXTENT OF SERVICES SUPPORTED BY Q-SIGNALING OVER IP

QSIG is a signaling protocol for controlling the establishment, maintenance and clearing of calls between PINXs, nodal entity known as Private Integrated services Network eXchange. It provides an extremely powerful method of connecting PINX equipment in a corporate network. QSIG is not a proprietary standard. It is an open, international standard and is supported by the world’s leading PBX suppliers. Twelve of the world’s leading PBX manufacturers signed a Memorandum of Understanding (MoU) concerning the development and support of QSIG. The MoU, which came into effect on 1st February 1994, commits the signatories to facilitate the performance of interoperability tests and to:


Introduction
QSIG is a signaling protocol for controlling the establishment, maintenance and clearing of calls between PINXs, nodal entity known as Private Integrated services Network eXchange. It provides an extremely powerful method of connecting PINX equipment in a corporate network. QSIG is not a proprietary standard. It is an open, international standard and is supported by the world's leading PBX suppliers. Twelve of the world's leading PBX manufacturers signed a Memorandum of Understanding (MoU) concerning the development and support of QSIG. The MoU, which came into effect on 1st February 1994, commits the signatories to facilitate the performance of interoperability tests and to: • incorporate a Primary Rate interface (as defined in ETS 300 011) into its products, • support a Basic Call (as defined in ETS 300 172), • implement the generic procedures (as defined in ETS 300 239), • implement QSIG supplementary services as far as each signatory considers to be economically viable, • and participate in interoperability testing with the other signatories.
QSIG standards are developed within ECMA in Technical Committee 32 (TC32) for Communications, networks and systems interconnection. TC32 began to work on QSIG in 1988 and most of these standards were published also as ISO/IEC International Standards, endorsed by ETSI as European Standards and implemented by all major PBX vendors. [2] 2. QSIG protocol stack QSIG standards specify a signaling system at the "Q" reference point, which is primarily intended for use on a common channel;  e.g. G.703 interface. Within the public ISDN the two end PINXs are connected through two reference points using different ISDN protocols, namely DSS1 at the "T" reference point and ISUP within the public ISDN at the "N" reference point. For private ISDNs, only one protocol is necessary as the QSIG protocols have sufficient functionality to be used both within the network at transit nodes and on the outside at access nodes.

EXTENT OF SERVICES SUPPORTED BY Q-SIGNALING OVER IP EXTENT OF SERVICES SUPPORTED BY Q-SIGNALING OVER IP
The architecture of QSIG signaling protocol agrees with the architecture RM OSI, see Figure 1.
The standard for Basic Call is ECMA 143 (ISO/IEC 11572), QSIG generic support for supplementary services is defined in ECMA-165 as a toolkit on which signaling for support of supplementary services can easily be built (ISO/IEC 11582). The QSIG protocol stack is identical in structure to the DSS1 protocol stack. Both follow the ISO reference model. Both can have an identical layer 1 and layer 2 (LAPD). However, at layer 3 QSIG and DSS1 differ.
In the last years significant part of work inside TC32 is concerned with the interoperation of Private Integrated Services Networks (PISN) with IP Networks, in particular with the two following aspects: • Interworking of PISNs and IP networks via Gateway, primarily between QSIG and H.323 and between QSIG and SIP, • Connection of PISN components via IP network infrastructures (i.e. QSIG tunnelling).
Inside the TC32 a new Task Group TG-17 was founded, known as TC32 -TG17, for standardization in the area of IP-based multimedia communications. This group considers possible future work in the area of NGN (Next Generation Networks), where close cooperation with ETSI is anticipated.
New ECMA standards allow tunnelling QSIG over IP network, see Figure 2, these standards are listed below.  Figure 3 shows that for private ISDNs, the QSIG protocols have sufficient functionality to be used both within the network at transit nodes and on the outside at access nodes. Hence QSIG is used between all three PINXs. The "Q" reference point is the logical signaling point between two PINXs. The physical connection to the PINXs is made at the "C" reference point. The Intervening Network (IVN) can be either dedicated channels (analogue or digital) or switched connections (for Virtual Private Networks).

Conditions of QSIG test interoperability
User signaling services can be divided into two groups:  In this QSIG test interoperability individual supplementary services were tested and signalling messages were traced between interconnected equipment in all signalling path. [3], [4], [5], [6].

Set up Notes
The Cisco 1751-V gateway with BRI-ISDN supports protocol QSIG, when the value of Switch-type parameter is set to basic-qsig. The network side on the BRI is set by the following commands: • isdn layer1-emulate network, • isdn protocol-emulate network.
Significant part of configuration in Cisco voice gateway is shown below as an example.

Set up Notes
The Siemens HiPath 4000 supports the protocol QSIG when the value of parameter Protvar in TDCSU command is set to PSS1V2, and the user side on the BRI is set by the following parameters: A significant part of configuration in Siemens HiPath 4000 is shown below as an example.

Decoding of QSIG
To decode the QSIG messages, SW application the WinVisu was used. It supports CORNET-NQ decoding protocol too and all the contents of signaling are in detail displayed in accordance with the recommendation of the chosen protocol, see Figure 5.

Test result
In the table below, the tested supplementary services are listed including the results related to each of these services.
Only one service (of all 22 supplementary services), Call Completion Busy Subscriber -CCBS did not work properly because the SETUP message was not transferred correctly through the IP network.  Table of tested supplementary services  Table 1