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Overview of ISDN Voice Interfaces
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Overview of ISDN Voice Interfaces

Table Of Contents

Overview of ISDN Voice Interfaces

Contents

Prerequisites for Configuring ISDN Voice Interfaces

Restrictions for Configuring ISDN Voice Interfaces

Information About ISDN Voice Interfaces

ISDN Media Types

Interface Cards and Network Modules

Typical ISDN Application

QSIG Protocol

QSIG Basics

ISDN Switch Types for Use with QSIG

Traceability of Diverted Calls

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance


Overview of ISDN Voice Interfaces


This chapter provides an overview of ISDN Basic Rate Interface (BRI) and Primary Rate Interface (PRI) for support of voice traffic. With those ports so configured, you can do the following:

Bypass PSTN tariffed services such as trunking and administration.

Connect your PBXs directly to a Cisco router and route PBX station calls automatically to the WAN.

Configure a voice interface on a Cisco router to emulate either a terminal-equipment (TE) or network-termination (NT) interface. All types of PBXs can send calls through a router and deliver those calls across the customer network.

Configure Layer 2 operation as point-to-point (static terminal endpoint identifier [TEI]) or point-to-multipoint (automatic TEI).

Contents

Prerequisites for Configuring ISDN Voice Interfaces

Restrictions for Configuring ISDN Voice Interfaces

Information About ISDN Voice Interfaces

Additional References

Prerequisites for Configuring ISDN Voice Interfaces

Obtain PRI or BRI service and T1 or E1 service from your service provider, as required. Ensure that the BRI lines are provisioned at the switch to support voice calls.

Establish a working IP, Frame Relay, or ATM network. Ensure that at least one network module or WAN interface card is installed in the router to provide connection to the LAN or WAN.

Complete your company's dial plan.

Establish a working telephony network based on your company's dial plan and configure the network for real-time voice traffic. This chapter describes only a portion of the process; for further information, see the chapter "Cisco Voice Telephony."

Cisco 2600 series and Cisco 3600 series routers—Install digital T1 or E1 packet-voice trunk network modules, BRI voice interface cards, and other voice interface cards as required on your network.

Cisco 7200 series routers—Install a single-port 30-channel T1/E1 high-density voice port adapter.

Cisco MC3810 multiservice concentrators—Install the required digital voice modules (DVMs), BRI voice module (BVM), and multiflex trunk modules.

Configure, for all platforms (as required), the following:

Voice card and controller settings

Serial and LAN interfaces

Voice ports

Voice dial peers

Restrictions for Configuring ISDN Voice Interfaces

ISDN Voice Interface Limitations

Basic-net3 and basic-qsig are the only ISDN switch types currently supported for an NT interface.

When the ISDN BRI port on the router is configured as an NT port, you must use a "rolled" cable (one with the transmit and receive leads swapped) to connect to a TE interface.

Layer 1 can be configured only as point-to-point (that is, with one TE connected to each NT). Automatic TEI support issues only one TEI.

QSIG Support Limitations

Cisco 2600 series routers do not support VoATM.

The following restrictions apply to the Cisco MC3810 multiservice concentrator:

QSIG data calls are not supported. All calls with bearer capability indicating a nonvoice type (such as for video telephony) are rejected.

Cisco MC3810 supports only one T1/E1 interface with direct connectivity to a private integrated services network exchange (PINX).

Cisco MC3810 supports a maximum of 24 B channels.

When QSIG is configured, serial port 1 does not support speeds higher than 192 kbps. This restriction assumes that the MFT is installed in slot 3 on the Cisco MC3810. If the MFT is not installed, then serial port 1 does not operate.

The following restrictions apply to Cisco 7200 series routers:

VoATM is not supported.

BRI is not supported.

Information About ISDN Voice Interfaces

ISDN Media Types

Interface Cards and Network Modules

Typical ISDN Application

QSIG Protocol

Traceability of Diverted Calls

ISDN Media Types

Cisco routing devices support ISDN BRI and ISDN PRI. Both media types use bearer (B) channels and data (D) channels as follows:

ISDN BRI (referred to as "2 B + D") uses the following:

Two 64-kbps B channels that carry voice or data for a maximum transmission speed of 128 kbps

One 16-kbps D channel that carries signaling traffic—that is, instructions about how to handle each of the B channels.

ISDN PRI (referred to as "23 B + D" or "30 B + D") uses the following:

23 B channels (in North America and Japan) or 30 B channels (in the rest of the world) that carry voice or data

One 64-kbps D channel that carries signaling traffic

The D channel, in its role as signal carrier for the B channels, directs the central-office switch to send incoming calls to particular timeslots on the Cisco access server or router. It also identifies the call as a circuit-switched digital call or an analog modem call. Circuit-switched digital calls are relayed directly to the ISDN processor in the router; analog modem calls are decoded and then sent to the onboard modems.

Interface Cards and Network Modules

The VIC-2BRI-NT/TE voice interface card for the Cisco 2600 series and Cisco 3600 series routers and the BVM4-NT/TE voice module for the Cisco MC3810 multiservice concentrator enable Cisco IOS software to replicate the PSTN interface to a PBX that is compatible with European Telecommunications Standards Institute (ETSI) NET3 and QSIG switch types.

Before these cards and modules became available, if your PBXs implemented only a BRI TE interface, you had to make substantial hardware and software changes on the PBX to provide an NT interface to the router. provide an NT interface to the router. VIC-2BRI-NT/NE and BVN4-NT/NE allow you to connect ISDN PBXs and key systems to a multiservice network with minimal configuration changes on the PBX.

Typical ISDN Application

A typical application (see Figure 1) allows an enterprise customer with a large installed base of legacy telephony equipment to bypass the PSTN.

Figure 1 Typical Application Using BRI-NT/TE Voice Interface Cards or BVM4-NT/TE Voice Modules

QSIG Protocol

This section contains the following information:

QSIG Basics

ISDN Switch Types for Use with QSIG

QSIG Basics

QSIG is a variant of ISDN Q.921 and Q.931 ISDN D-channel signaling, for use in private integrated-services network-exchange (PINX) devices such as PBXs or key systems. Using QSIG signaling, a router can route incoming voice calls from a PINX across a WAN to a peer router, which can then transport the signaling and voice packets to another PINX.

The QSIG protocol was originally specified by European Computer Manufacturers Association (ECMA), and then adopted by European Telecommunications Standards Institute (ETSI) and the International Organization for Standardization (ISO). It is becoming the standard for PBX interoperability in Europe and North America.

Table 1 identifies the ECMA standards and the OSI layer of the QSIG protocol stack to which they relate.

Table 1 QSIG Protocol Stack

OSI Layer
Standard
Description

7 to 4

Application mechanisms

End-to-end protocols; network transparent

3

Multiple ECMA standards

Standards for supplementary services and advanced network features

ECMA-165

QSIG generic functional procedures

ECMA-142/143

QSIG basic call

2

ECMA-141

Interface-dependent protocols

1

I.430 / I.431

PRI and BRI


QSIG enables Cisco networks to emulate the functionality of the PSTN. A Cisco device routes incoming voice calls from a PINX across a WAN to a peer device, which then transports the signaling and voice packets to a second PINX (see Figure 2).

Figure 2 QSIG Signaling

The Cisco voice-packet network appears to the QSIG PBXs as a distributed transit PBX that can establish calls to any PBX, non-QSIG PBX, or other telephony endpoint served by a Cisco gateway, including non-QSIG endpoints.

QSIG messages that originate and terminate on QSIG endpoints pass transparently across the network; the PBXs process and provision any supplementary services. When endpoints are a mix of QSIG and non-QSIG, only basic calls that do not require supplementary services are supported.

QSIG signaling provides the following benefits:

It provides efficient and cost-effective telephony services on permanent (virtual) circuits or leased lines.

It allows enterprise networks that include PBX networks to replace leased voice lines with a Cisco WAN.

It eliminates the need to route connections through multiple tandem PBX hops to reach the desired destination, thereby saving bandwidth, PBX hardware, and switching power.

It improves voice quality through the single-hop routing provided by voice switching while allowing voice to be compressed more aggressively, resulting in additional bandwidth savings.

It supports PBX feature transparency across a WAN, permitting PBX networks to provide advanced features such as calling name and number display, camp-on/callback, network call forwarding, centralized attendant, and centralized message waiting. Usually these capabilities are available on only a single site where users are connected to the same PBX.

QSIG support enables the following:

Digit forwarding on POTS dial peers

On Cisco 2600 series, QSIG-switched calls over VoFR and VoIP for T1/E1 and BRI voice interface cards

On Cisco 3600 series, QSIG-switched calls over VoFR, VoIP, and VoATM for T1/E1 and BRI voice interface cards

On Cisco 7200 series, QSIG-switched calls over VoFR and VoIP on T1/E1 voice interface cards

On Cisco MC3810, T1 or E1 PRI and BRI QSIG-switched calls over VoFR, VoIP, and VoATM for Cisco MC3810 digital voice modules and BRI voice module.

Figure 3 shows an example of how QSIG support can enable toll bypass.

Figure 3 QSIG Toll-Bypass Application

ISDN Switch Types for Use with QSIG

You can configure QSIG at either the global configuration level or the interface configuration level. To do so requires that you know your switch type. Available types are shown in Table 2.

Table 2 ISDN Central-Office Switch Types 

Country
ISDN Switch Type
Description

Australia

basic-ts013

Australian TS013 switches

Europe

basic-1tr6

German 1TR6 ISDN switches

basic-nwnet3

Norwegian NET3 ISDN switches (phase 1)

basic-net3

NET3 ISDN switches (United Kingdom and others)

vn2

French VN2 ISDN switches

vn3

French VN3 ISDN switches

Japan

ntt

Japanese NTT ISDN switches

New Zealand

basic-nznet3

New Zealand NET3 switches

North America

basic-5ess

Lucent Technologies basic rate switches

basic-dms100

NT DMS-100 basic rate switches

basic-ni1

National ISDN-1 switches


Table 3 lists the ISDN service-provider BRI switch types.

Table 3 ISDN Service-Provider BRI Switch Types 

ISDN Switch Type
Description

basic-1tr6

German 1TR6 ISDN switches

basic-5ess

Lucent Technologies basic rate switches

basic-dms100

NT DMS-100 basic rate switches

basic-net3

NET3 (TBR3) ISDN, Norway NET3, and New Zealand NET3 switches. (This switch type covers the Euro-ISDN E-DSS1 signaling system and is ETSI-compliant.)

basic-ni1

National ISDN-1 switches

basic-nwnet3

Norwegian NET3 ISDN switches (phase 1)

basic-nznet3

New Zealand NET3 switches

basic-qsig

PINX (PBX) switches with QSIG signaling in compliance with Q.931

basic-ts013

Australian TS013 switches

ntt

Japanese NTT ISDN switches

vn2

French VN2 ISDN switches

vn3

French VN3 ISDN switches


Cisco platforms that support Q.931 offer both user-side and network-side switch types for ISDN call processing, providing the following benefits:

User-side PRI enables the Cisco device to provide a standard ISDN PRI user-side interface to the PSTN.

Network-side PRI enables the Cisco device to provide a standard ISDN PRI network-side interface via digital T1/E1 packet voice trunk network modules on Cisco 2600 series and Cisco 3600 series routers.

Traceability of Diverted Calls

European Telecommunication Standard ETSI 300 207-1 specifies that calls must be traceable if diverted. This requires that a VoIP call, when diverted, must translate into divertingLegInformation2 instead of Redirection IE. Cisco's ISDN implementation satisfies this requirement.

Additional References

The following sections provide references related to ISDN.


NoteIn addition to the references listed below, each chapter provides additional references related to ISDN.

Some of the products and services mentioned in this guide may have reached end of life, end of sale, or both. Details are available at http://www.cisco.com/en/US/products/hw/tsd_products_support_end-of-sale_and_end-of-life_products_list.html


Related Documents

Related Topic
Document Title

AIM, ATM, and IMA

AIM-ATM, AIM-VOICE-30, and AIM-ATM-VOICE-30 on the Cisco 2600 Series and Cisco 3660 at http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/122t/122t8/ft_04gin.htm

ATM Software Segmentation and Reassembly (SAR) at http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/122limit/122x/122xb/122xb_2/ft_t1atm.htm

Cisco IOS Wide-Area Networking Configuration Guide, chapter on configuring ATM at http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fwan_c/wcfatm.htm

Installing the High Performance ATM Advanced Integration Module in Cisco 2600 Series Routers at http://www.cisco.com/en/US/products/hw/routers/ps259/tsd_products_support_reference_guides.html

Basic router configuration

Cisco 2600 series documentation at http://www.cisco.com/en/US/products/hw/routers/ps259/tsd_products_support_reference_guides.html

Cisco 3600 series documentation at http://www.cisco.com/en/US/products/hw/routers/ps274/tsd_products_support_reference_guides.html

Cisco 3700 series documentation at http://www.cisco.com/univercd/cc/td/doc/product/access/acs_mod/cis3700/index.htm

Cisco AS5300 documentation at http://www.cisco.com/univercd/cc/td/doc/product/access/acs_serv/5300/index.htm

Cisco IOS command references

Cisco IOS Debug Command Reference, Release 12.3T at http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123tcr/123dbr/index.htm

Cisco IOS Voice Command Reference, Release 12.3T at http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123tcr/123tvr/index.htm

Cisco IOS configuration fundamentals and examples

Cisco IOS Configuration Fundamentals Configuration Guide at http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/ffun_c/

Cisco IOS Interface Command Reference at http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/finter_r/index.htm

Cisco IOS Interface Configuration Guide at http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/finter_c/

Cisco Systems Technologies website at http://cisco.com/en/US/tech/index.html

From the website, select a technology category and subsequent hierarchy of subcategories, then click Technical Documentation > Configuration Examples.

Cisco IOS Voice Configuration Library, including library preface and glossary

Cisco IOS Voice Configuration Library at http://www.cisco.com/en/US/docs/ios/12_3/vvf_c/cisco_ios_voice_configuration_library_glossary/vcl.htm

Clock sources

Cisco IOS Voice, Video, and Fax Configuration Guide chapter on configuring voice ports at http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fvvfax_c/vvfport.htm#18533

ISDN basics

Cisco IOS Release 12.2 Configuration Guides and Command References library at http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/

Cisco IOS Release 12.3 Configuration Guides and Command References library at http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123cgcr/index.htm

ISDN cause codes

ISDN Switch Types, Codes, and Values at http://www.cisco.com/univercd/cc/td/doc/product/software/ios113ed/dbook/disdn.htm

ISDN configuration

Cisco IOS Voice, Video, and Fax Configuration Guide at http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fvvfax_c/vvfisdn.htm

ISDN Basic Rate Service Setup Commands at http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/12cgcr/dial_r/drprt1/drbri.htm

ISDN interfaces for voice

Cisco 7200 Series Port Adapter Hardware Configuration Guidelines at http://www.cisco.com/univercd/cc/td/doc/product/core/7206/port_adp/config/

Cisco MC3810 Multiservice Concentrator Hardware Installation at http://www.cisco.com/univercd/cc/td/doc/product/access/multicon/3810hwig/

Quick Start Guide: Cisco MC3810 Installation and Startup at http://www.cisco.com/univercd/cc/td/doc/product/access/multicon/3810qsg.htm

 

ISDN network modules and interface cards

Cisco Network Modules Hardware Installation Guide at http://www.cisco.com/univercd/cc/td/doc/product/access/acs_mod/cis2600/hw_inst/nm_inst/nm-doc/

Cisco WAN Interface Cards Hardware Installation Guide at http://www.cisco.com/univercd/cc/td/doc/product/access/acs_mod/cis3600/wan_mod/

Installing and Configuring 1-Port J1 Voice Interface Cards at http://www.cisco.com/univercd/cc/td/doc/product/access/acs_mod/cis3600/hw_inst/hw_notes/j1vwic.htm

Update to Cisco WAN Interface Cards Hardware Installation Guide at http://www.cisco.com/univercd/cc/td/doc/product/access/acs_mod/cis2600/hw_inst/wic_inst/wan_updt.htm

Voice Network Module and Voice Interface Card Configuration Note at http://www.cisco.com/univercd/cc/td/doc/product/access/acs_mod/cis3600/voice/4712voic.htm

MIX module

Multiservice Interchange (MIX) for Cisco 2600 and 3600 Series Multiservice Platforms at http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/122t/122t4/ft_24mix.htm

RADIUS VSA configuration

RADIUS VSA Voice Implementation Guide at http://www.cisco.com/univercd/cc/td/doc/product/access/acs_serv/vapp_dev/vsaig3.htm

SCTP

Stream Control Transfer Protocol (SCTP) at http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/122t/122t8/ft_sctp2.htm

Security

Cisco IOS Security Configuration Guide at http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fsecur_c/index.htm

SS7 for voice gateways

Configuring Media Gateways for the SS7 Interconnect for Voice Gateways Solution at http://www.cisco.com/univercd/cc/td/doc/product/access/sc/rel7/soln/das22/gateway/dascfg5.htm

Tcl IVR programming

Tcl IVR API Version 2.0 Programmer's Guide at http://www.cisco.com/univercd/cc/td/doc/product/access/acs_serv/vapp_dev/tclivrv2/index.htm

Troubleshooting

Cisco IOS Debug Command Reference, Release 12.3T at http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123tcr/123dbr/index.htm

Cisco IOS Voice Troubleshooting and Monitoring Guide at http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123cgcr/vvfax_c/voipt_c/index.htm

Internetwork Troubleshooting Guide at http://www.cisco.com/univercd/cc/td/doc/cisintwk/itg_v1/index.htm

Voice over IP Troubleshooting and Monitoring at http://cisco.com/univercd/cc/td/doc/product/software/ios123/123cgcr/vvfax_c/voipt_c/index.htm

VoATM configuration

Configuring AAL2 and AAL5 for the High-Performance Advanced Integration Module on the Cisco 2600 Series at http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/122limit/122x/122xa/122xa_2/ft_ataim.htm

VoIP configuration

Voice over IP for the Cisco 2600/3600 Series at http://www.cisco.com/univercd/cc/td/doc/product/access/nubuvoip/voip3600/index.htm

Voice over IP for the Cisco AS5300 at http://www.cisco.com/univercd/cc/td/doc/product/access/nubuvoip/voip5300/index.htm

Voice over IP for the Cisco AS5800 at http://www.cisco.com/univercd/cc/td/doc/product/access/nubuvoip/voip5800/index.htm

WAN configuration

Cisco IOS Wide-Area Networking Command Reference at http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fwan_r/index.htm

Cisco IOS Wide-Area Networking Configuration Guide at http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fwan_c/wcfatm.htm


Standards

Standards
Title

014-0018-04.3D-ER

CPE Requirements for MCI ISDN Primary Rate Interface, revision 4.3D, February 10, 1998

ETSI 300 207-1

Integrated Services Digital Network (ISDN): Diversion supplementary services; Digital Subscriber Signalling System No. one (DSS1) protocol; Part 1: Protocol specification, December 1994

TR-41459

AT&T Network ISDN Primary Rate Interface and Special Applications Specifications, User-Network Interface, 1999

TTC JJ-20.10 to JJ-20.12

PBX


MIBs

MIBs
MIBs Link

CISCO-CAS-IF-MIB.my

CISCO-ICSUDSU-MIB

RFC 1407 MIB

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL: http://www.cisco.com/go/mibs


RFCs


Technical Assistance

Description
Link

The Cisco Technical Support website contains thousands of pages of searchable technical content, including links to products, technologies, solutions, technical tips, and tools. Registered Cisco.com users can log in from this page to access even more content.

http://www.cisco.com/techsupport



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