TD 92326GB
2009-03-10 / Ver. E
Installation and Operation Manual
VoIP Gateway
155
TX/RX Lead Gateway settings
22.4 The Signalling Protocols
The VoIP Gateway supports different D channel
1
protocols on the ISDN interfaces; Euro
ISDN (EDSS1), NI, 15ESS, DMS100 and QSIG.
Euro-ISDN is the type of signalling that has gained worldwide acceptance for ISDN
subscriber interfaces and, despite the name, is also common outside Europe. The chief
exception at the moment is the United States, where other digital signalling methods are
generally used.
NI-1 (National ISDN-1) and NI-2 (National ISDN-2) are specifications for a “standard” ISDN
phone line. National ISDN 1 and National ISDN 2 are intended to be a set of standards to
which every manufacturers' equipment should conform for maximum interoperability. NI3
is a future standard currently under development.
5ESS is an ISDN protocol used in the USA by AT&T. It is the most widely used of the ISDN
protocols and contains 19 network-specific message types. It has no Codeset 5, but does
have 18 Codeset 6 elements and an extensive information management element.
DMS100 is the name of a central office switch manufactured by Northern Telecom. These
switches use Custom (proprietary) or National ISDN-1 (NI-1) software. The DMS switches
used by Southwestern Bell currently support the NI-1 standard
QSIG is a common channel signalling protocol based on ISDN Q.931 standards, that is
mainly used to connect PBXs. QSIG is used for the establishment and release of calls and
for the control of a large number of features. Here, “basic call” and “tunnelling” are
supported by the VoIP Gateway. This allows, in particular, homogenous PBX systems to be
linked with QSIG, in which manufacturer- specific properties are exchanged via QSIG.
There are several variants of the QSIG standard and various implementations; some
conform more and some less to the standard. The VoIP Gateway supports 3 different
variants which vary with regard to the following:
• length of the call reference
• coding of the channel id
• numbering of the B channels
The following table specifies the differences.
NT Mode = Checked (We are Network/Master)
Gateway TX Lead
Clock Mode = Derived from NT Mode
1&2
Clock Mode = Slave
4&5
Clock Mode = Master
1&2
NT Mode = Unchecked (we are User/Slave)
Clock Mode = Derived from NT Mode
4&5
Clock Mode = Slave
4&5
Clock Mode = Master
1&2
Note that the TX/RX leads always follow the clock source. If we are receiving clock, then
the TX leads are pins 4&5. If we are providing clock, the TX leads are 1&2.
1.Short for Delta-channel, the channel in an ISDN connection that carries control and signaling information.
