Voice Port Configuration Guide, Cisco IOS Release 15M&T
Configuring Digital Voice Ports
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Configuring Digital Voice Ports

Contents

Configuring Digital Voice Ports

The digital voice port commands discussed in this section configure channelized T1 or E1 connections; for information on ISDN connections, refer to the Cisco IOS ISDN Voice Configuration Guide.

The T1 or E1 lines that connect a telephony network to the digital voice ports on a router or access server contain channels for voice calls; a T1 line contains 24 full-duplex channels or timeslots , and an E1 line contains 30. The signal on each channel is transmitted at 64 kbps, a standard known as Digital Signal 0 (DS0); the channels are known as DS0 channels. The ds0-group command creates a logical voice port (a DS0 group) from some or all of the DS0 channels, which allows you to address those channels easily, as a group, in voice-port configuration commands.

Digital voice ports are found at the intersection of a packet voice network and a digital, circuit-switched telephone network. The digital voice port interfaces that connect the router or access server to T1 or E1 lines pass voice data and signaling between the packet network and the circuit-switched network.

Signaling is the exchange of information about calls and connections between two ends of a communication path. For instance, signaling communicates to the call’s endpoints whether a line is idle or busy, whether a device is on-hook or off-hook, and whether a connection is being attempted. An endpoint can be a central office (CO) switch, a PBX, a telephony device such as a telephone or fax machine, or a voice-equipped router acting as a gateway. There are two aspects to consider about signaling on digital lines: one aspect is the actual information about line and device states that is transmitted, and the second aspect is the method used to transmit the information on the digital lines.

The actual information about line and device states is communicated over digital lines using signaling methods that emulate the methods used in analog circuit-switched networks: Foreign Exchange Service (FXS), Foreign Exchange Office (FXO), and Ear and Mouth (E&M).

The method used to transmit the information describes the way that the emulated analog signaling is transmitted over digital lines, which may be common-channel signaling (CCS) or channel-associated signaling (CAS). CCS sends signaling information down a dedicated channel and CAS takes place within the voice channel itself. This chapter describes CAS, which is sometimes called robbed-bit signaling because user bandwidth is robbed by the network for signaling. A bit is taken from every sixth frame of voice data to communicate on- or off-hook status, wink, ground-start, dialed digits, and other information about the call.

In addition to setting up and tearing down calls, CAS provides the receipt and capture of dialed number identification (DNIS) and automatic number identification (ANI) information, which are used to support authentication and other functions. The main disadvantage of CAS is its use of user bandwidth to perform these signaling functions.

For signaling to pass between the packet network and the circuit-switched network, both networks must use the same type of signaling. The voice ports on Cisco routers and access servers can be configured to match the signaling of most COs and PBXs, as explained in this document.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Prerequisites for Configuring Digital Voice Ports

Digital T1 or E1 packet voice capability requires specific service, software, and hardware:

  • Obtain T1 or E1 service from the service provider or from your PBX.
  • Create your company’s dial plan.
  • Establish a working telephony network based on your company’s dial plan.
  • Establish a connection to the network LAN or WAN.
  • Set up a working IP and Frame Relay or ATM network. For more information about configuring IP, refer to the Cisco IOS IP Configuration Guide.
  • Install appropriate voice processing and voice interface hardware on the router. See the Information About Digital Voice Hardware.
  • (Cisco 2600 and Cisco 3600 series routers) For digital T1 packet voice trunk network modules, install Cisco IOS Release 12.2(1) or a later release. The minimum DRAM memory requirements are as follows:
    • 32 MB, with one or two T1 lines
    • 48 MB, with three or four T1 lines
    • 64 MB, with five to ten T1 lines
    • 128 MB, with more than ten T1 lines

The memory required for high-volume applications may be greater than that listed. Support for digital T1 packet voice trunk network modules is included in Plus feature sets. The IP Plus feature set requires 8 MB of flash memory; other Plus feature sets require 16 MB.

  • (Cisco 2600 and Cisco 3600 series routers) For digital E1 packet voice trunk network modules, install Cisco IOS Release 12.2(1) or a later release. The minimum DRAM memory requirements are:
    • 48 MB, with one or two E1s
    • 64 MB, with three to eight E1s
    • 128 MB, with 9 to 12 E1s

For high-volume applications, the memory required may be greater than these minimum values. Support for digital E1 packet voice trunk network modules is included in Plus feature sets. The IP Plus feature set requires 16 MB of flash memory.

  • Before you can run the IP Communications High-Density Digital Voice/Fax Network Module feature on T1/E1 interfaces, you must install an IP Plus image (minimum) of Cisco IOS Release 12.3(7)T or a later release.
  • (Cisco MC3810 concentrators) HCMs require Cisco IOS Release 12.2(1) or a later release.
  • (Cisco 7200 and Cisco 7500 series routers) For digital T1/E1 voice port adapters, install Cisco IOS Release 12.2(1) or a later release. The minimum DRAM memory requirement to support T1/E1 high-capacity digital voice port adapters is 64 MB.

The memory required for high-volume applications may be greater than that listed. Support for T1/E1 high-capacity digital voice port adapters is included in Plus feature sets. The IP Plus feature set requires 16 MB of flash memory.

  • Gather the following information about the telephony network connection of the voice port:
    • Line interface: T1 or E1
    • Signaling interface: FXO, FXS, or E&M. If the interfaces are PRI or BRI, refer to the Cisco IOS ISDN Voice Configuration Guide, and Cisco IOS Terminal Services Configuration Guide.
    • Line coding: AMI or B8ZS for T1, and AMI or HDB3 for E1
    • Framing format: SF (D4) or ESF for T1, and CRC4 or no-CRC4 for E1
    • Number of channels

After the controllers have been configured, the show voice port summarycommand can be used to determine available voice port numbers. If the show voice port command and a specific port number is entered, the default voice-port configuration for that port displays.

The following is show voice port summary sample output for a Cisco MC3810:

Router# show voice port summary
IN      OUT
PORT   CH SIG-TYPE   ADMIN OPER STATUS   STATUS   EC
====== == ========== ===== ==== ======== ======== ==
0:17   18 fxo-ls     down  down idle     on-hook  y
0:18   19 fxo-ls     up    dorm idle     on-hook  y
0:19   20 fxo-ls     up    dorm idle     on-hook  y
0:20   21 fxo-ls     up    dorm idle     on-hook  y
0:21   22 fxo-ls     up    dorm idle     on-hook  y
0:22   23 fxo-ls     up    dorm idle     on-hook  y
0:23   24 e&m-imd    up    dorm idle     idle     y

Note


The slot and port numbering of interface cards differs for each of the voice-enabled routers. For specific slot and port designations, refer to the hardware installation documentation for your router platform. More current information may be available in the release notes that accompany the Cisco IOS software you are using.


Information About Digital Voice Hardware


Note


For current information about supported hardware, refer to the release notes for the platform and Cisco IOS release you are using.


Cisco 880 Series Routers

Beginning with Cisco IOS Release 12.4(15)XZ, the Cisco 880 series fixed router platforms support the implementation of analog (FXS/DID/FXO) and digital (BRI S/T) voice ports. The IAD881B, IAD881F, IAD888B, and IAD888F models support voice interface FXS or BRI. The IAD881F and IAD888F models have four FXS ports and the IAD881B and IAD888B models support two ports for ISDN BRI digital voice interface.

In the IAD881B and IAD888B models, the voice BRI interface presents an ISDN S/T interface to connect either to an NT1 terminating an ISDN telephone network (TE-side) or to a TE user device such as an ISDN telephone or PBX (NT-side). In the IAD881B and IAD888B models, the BRI interface is available as the primary voice interface and is intended to be connected to a PBX (network side trunk). All the voice interfaces are onboard though they are recognized as a 4-port FXS VIC and a 2-port BRI VIC in order to leverage existing voice drivers.

The C881and C888 SRST models automatically detect a failure occuring in the network and initiate a process to auto-configure the router. This process provides call-processing backup redundancy for the IP and FXS phones and helps to ensure that telephony capabilities stay operational. All the IP or analog phones hanging off of a telecommuter site are controlled by the headquarters office call control (Cisco Unified CallManager or CallManager Express). In case of a WAN failure, the telecommuter router allows all phones to re-register to it in SRST mode and allow all inbound and outbound dialing to be routed off to the PSTN (using back up FXO or BRI port). Upon restoration of WAN connectivity, the system automatically shifts call processing back to the primary Cisco Unified Call Manager cluster.


Note


If the primary voice interface is FXS and the backup is BRI, then ports 0, 1, 2, and 3 are analog voice ports, and ports 4 and 5 are digital. If the primary voice interface is BRI, then ports 1, 2, 3, and 4 are digital.


Cisco 2600 Cisco 3600 and Cisco 3700 Series Routers

Digital voice hardware on Cisco 2600 series, Cisco 3600 series, and Cisco 3700 series modular access routers includes the high-density voice (HDV) network module and the multiflex trunk (MFT) voice/WAN interface card (VWIC). When an HDV is used in conjunction with an MFT and packet voice DSP modules (PVDMs), the HDV module is also called a digital packet voice trunk network module. The digital T1 or E1 packet voice trunk network module supports T1 or E1 applications, including fractional use. The T1 version integrates a fully managed DSU/CSU, and the E1 version includes a fully managed DSU. The digital T1 or E1 packet voice trunk network module provides per-channel T1 or E1 data rates of 64 or 56 kbps for WAN services (Frame Relay or leased line).

Digital T1 or E1 packet voice trunk network modules allow enterprises or service providers, using the voice-equipped routers as customer premises equipment (CPE), to deploy digital voice and fax relay. These network modules receive constant bit-rate telephony information over T1 or E1 interfaces and convert that information to a compressed format so that it can be sent over a packet network. The digital T1 or E1 packet voice trunk network modules can connect either to a PBX (or similar telephony device) or to a CO to provide PSTN connectivity.

The MFT VWICs that are used in the packet voice trunk network modules are available in one- and two-port configurations for T1 and for E1, and in two-port configurations with drop-and-insert capability for T1 and E1. MFTs support the following kinds of traffic:

  • Data. As WICs for T1 or E1 applications, including fractional data line use, the T1 version includes a fully managed DSU/CSU, and the E1 version includes a fully managed DSU.
  • Packet voice. As VWICs included with the digital T1 or E1 packet voice trunk network module to provide connections to PBXs and COs, the MFTs enable packet voice applications.
  • Multiplexed voice and data. Some two-port T1 or E1 VWICs can provide drop-and-insert multiplexing services with integrated DSU/CSUs. For example, when used with a digital T1 packet voice trunk network module, drop-and-insert allows 64-kbps DS0 channels to be taken from one T1 and digitally cross-connected to 64-kbps DS0 channels on another T1. Drop and insert, sometimes called time-division multiplex (TDM) cross-connect, uses circuit switching rather than the digital signal processors (DSPs) that VoIP technology employs. (Drop-and-insert is described in the "Trunk Management Features" document.

The digital T1 or E1 packet voice trunk network module contains five 72-pin Single In-line Memory Module (SIMM) sockets or banks, numbered 0 through 4, for PVDMs. Each socket can be filled with a single 72-pin PVDM, and there must be at least one packet voice data module (PVDM-12) in the network module to process voice calls. Each PVDM holds three DSPs, so with five PVDM slots populated, a total of 15 DSPs are provided. High-complexity codecs support two simultaneous calls on each DSP, and medium-complexity codecs support four calls on each DSP. A digital T1 or E1 packet voice trunk network module can support the following numbers of channels:

  • When the digital T1 or E1 packet voice trunk network module is configured for high-complexity codec mode, up to six voice or fax calls can be completed per PVDM-12, using the following codecs: G.711, G.726, G.729, G729 Annex A (E1), G.729 Annex B, G.723.1, G723.1 Annex A (T1), G.728, and fax relay.
  • When the digital T1 or E1 packet voice trunk network module is configured for medium-complexity codec mode, up to 12 voice or fax calls can be completed per PVDM-12, using the following codecs: G.711, G.726, G.729 Annex A, G.729 Annex B with Annex A, and fax relay.

For more information, refer to the following:

Cisco 7200 and Cisco 7500 Series Routers

Cisco 7200 and Cisco 7500 series routers support multimedia routing and bridging with a wide variety of protocols and media types. The Cisco 7000 family Versatile Interface Processor (VIP) is based on a reduced instruction set computing (RISC) engine optimized for I/O functions. To this engine are attached one or two port adapters or daughter boards, which provide the media-specific interfaces to the network. The network interfaces provide connections between the routers’ peripheral component interconnect (PCI) buses and external networks. Port adapters can be placed in any available port adapter slot, in any desired combination.

T1/E1 high-capacity digital voice port adapters for Cisco 7200 and Cisco 7500 series routers allow enterprises or service providers, using the equipped routers as CPE, to deploy digital voice and fax relay. These port adapters receive constant bit-rate telephony information over T1/E1 interfaces and can convert that information to a compressed format for transmission as VoIP. Two types of digital voice port adapters are supported on Cisco 7200 and Cisco 7500 series routers: two-port high-capacity (up to 48 or 120 channels of compressed voice, depending on codec choice), and two-port moderate capacity (up to 24 or 48 channels of compressed voice). These single-width port adapters incorporate two universal ports configurable for either T1 or E1 connection, for use with high-performance DSPs. Integrated CSU/DSUs, echo cancellation, and DS0 drop-and-insert functionality eliminate the need for external line termination devices and multiplexers.

For more information, refer to the following publications:


Note


For current information about supported hardware, refer to the release notes for the platform and Cisco IOS release you are using.


Cisco AS5300

The Cisco AS5300 includes three expansion slots. One slot is for either an Octal T1/E1/PRI feature card (eight ports) or a Quad T1/E1/PRI feature card (four ports), and the other two can be used for voice/fax or modem feature cards. Because a single voice/fax feature card (VFC) can support up to 48 (T1) or 60 (E1) voice calls, the Cisco AS5300 can support a total of 96 or 120 simultaneous voice calls.

Cisco AS5300 VFCs are coprocessor cards, each with a powerful reduced instruction set computing (RISC) engine and dedicated, high-performance DSPs to ensure predictable, real-time voice processing. The design couples this coprocessor with direct access to the Cisco AS5300 routing engine for streamlined packet forwarding.

For more information, refer to the following publications:

Cisco AS5350 and Cisco AS5400 Universal Gateways

The Cisco AS5350 and Cisco AS5400 universal gateways are versatile data and voice communications platforms that provide the functions of a gateway, router, and digital modems in a single modular chassis.

The gateways are intended for Internet service providers (ISPs), telecommunications carriers, and other service providers that offer managed Internet connections, and also medium to large sites that provide both digital and analog access to users on an enterprise network.

The cards that reside in the Cisco AS5350 and AS5400 chassis, sometimes referred to as dial feature cards (DFCs), are of two types: trunk cards, which provide an E1, T1, or T3 interface, and universal port cards, which host the universal DSPs that dynamically handle voice, dial, and fax calls.

For more information, refer to the following publications:

Cisco AS5800

The Cisco AS5800 has two primary system components: the Cisco 5814 dial shelf (DS), which holds channelized trunk cards and connects to the PSTN, and the Cisco 7206 router shelf (RS), which holds port adapters and connects to the IP backbone.

The dial shelf acts as the access concentrator by accepting and consolidating all types of remote traffic, including voice, dial-in analog and digital ISDN data, and industry-standard WAN and remote connection types. The dial shelf also contains controller cards voice feature cards, modem feature cards, trunk cards, and dial shelf interconnect cards.

One or two dial shelf controllers (DSCs) provide clock and power control to the dial shelf cards. Each DSC contains a block of logic that is referred to as the common logic and system clocks. This block of logic can use a variety of sources to generate the system timing, including an E1 or T1/T3 input signal from the BNC connector on the front panel of the DSC. The configuration commands for the master clock specify the various clock sources and a priority for each source (see the Clock Sources on Digital T1 E1 Voice Ports).

The Cisco AS5800 voice feature card is a multi-DSP coprocessing board and software package that adds VoIP capabilities to the Cisco AS5800 platform. The Cisco AS5800 voice feature card, when used with other cards such as LAN/WAN and modem cards, provides a gateway for up to 192 packetized voice/fax calls and 360 data calls per card. A Cisco AS5800 can support up to 1344 voice calls in split-dial-shelf configuration with two 7206VXR router shelves.

For more information, refer to the following publications:

Cisco AS5850 Universal Gateway

The Cisco AS5850 is a high-density ISDN and port WAN aggregation system that provides both digital and analog call termination. It is intended to be used in service-provider dial point-of-presence (POP) or centralized-enterprise dial environments. The feature cards and the route switch controller (RSC) communicate over a nonblocking interconnect that supports Fast Ethernet and full-duplex service.

The Cisco AS5850 contains ingress interfaces (CT3 and CE1/PRI) that terminate ISDN and modem calls and break out individual calls (DS0s) from the appropriate telco services. Digital or ISDN calls are terminated on the trunk-card HDLC controllers, and analog calls are sent to port resources on the same card or on separate port cards. As a result, any DS0 can be mapped to any HDLC controller or port module. Unlike the Cisco AS5800, trunk-termination and port-handling services can be performed on the same card in the same slot.

For more information, refer to the following publications:

Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers

The Communication Media Module (CMM) acts as the VoIP gateway and media services module by using Media Gateway Control Protocol (MGCP), H.323, and SIP protocols with Cisco CallManager and other call agents. The CMM can support single or multiple Cisco CallManagers in an IP communication network.

These VoIP gateway and media services features are provided through the four different types of CMM port adapters as shown in the table below.

Table 1 CMM Port Adapters

CMM Port Adapters

Description

  • WS-SVC-CMM-6T1
  • WS-SVC-CMM-6E1

The 6-port T1 and E1 port adapters have onboard digital signal processor (DSP) resources that allow you to connect the interfaces to the public switched telephone network (PSTN) or private branch exchanges (PBXs) through T1/E1R2 Channel Associated Signaling (CAS) or T1/E1 ISDN Primary Rate Interface (PRI). The DSP resources on the port adapters provide packetization, echo cancellation, fax relay, tone detection and generation, concealment, and jitter buffers.

WS-SVC-CMM-24FXS

The 24-port FXS port adapter has onboard DSP resources that allow the FXS interfaces to emulate the central office (CO) or PBX analog trunk lines by providing service to analog phones and fax machines, which behave as if connected to a standard CO or PBX line.

WS-SVC-CMM-ACT

The ACT port adapter has DSP resources for conferencing, transcoding, and media termination point (MTP) services. A CMM with an ACT port adapter supports a single conference with up to 64 participants. A single ACT port adapter supports up to 128 audio conference ports, which can be distributed among different conferences of two or more parties.

For specific configuration information for the Catalyst 6500 series and Cisco 7600 series, see the following documents:

For specific installation and configuration information for the CMM, see the following document:

Cisco MC3810

To support a T1 or E1 digital voice interface, the Cisco MC3810 must be equipped with a digital voice interface card (DVM). The DVM interfaces with a digital PBX, channel bank, or video codec. It supports up to 24 channels of compressed digital voice at 8 kbps, or it can cross-connect channelized data from user equipment directly onto the router’s trunk port for connection to a carrier network.

The DVM is available with a balanced interface using an RJ-48 connector or with an unbalanced interface using BNC connectors.

Optional HCMs can replace standard VCMs to operate according to the voice compression coding algorithm (codec) specified when the Cisco MC3810 is configured. The HCM2 provides 4 voice channels at high codec complexity and 8 channels at medium complexity. The HCM6 provides 12 voice channels at high complexity and 24 channels at medium complexity. You can install one or two HCMs in a Cisco MC3810, but an HCM cannot be combined with a VCM in the same chassis.

For more information, refer to the following publications:

How to Configure Digital T1 E1 Voice Ports

This section describes commands for the basic configuration of digital voice ports. Make sure you have all the data recommended in the Prerequisites for Configuring Digital Voice Ports before starting these procedures.

The basic steps for configuring digital voice ports are described in the next three sections. They are grouped by the configuration mode from which they are executed, as follows:

Configuring Codec Complexity on Digital T1 E1 Voice Ports

This section provides two configuration task tables: one for the Cisco 2600, Cisco 3600, and Cisco 3700 series routers and the Cisco MC3810 concentrator, which use voice-card configuration mode, and the second for the Cisco 7200 and Cisco 7500 series routers, which use DSP interface configuration mode. The task tables can be found in the following sections:

Configuring Codec Complexity on Cisco 880 Series, Cisco 2600, Cisco 3600, Cisco 3700 Series and Cisco MC3810:

Codec complexity refers to the amount of processing power assigned to a codec method on a voice port. On most router platforms that support codec complexity, codec complexity is selected in voice-card configuration mode, although it is selected in DSP interface mode on the Cisco 7200 and Cisco 7500 series. On the Cisco 880 series, Cisco 2600, Cisco 3600, Cisco 3700, Cisco 7200, and Cisco 7500 routers, codec complexity can be configured separately for each T1/E1 digital packet voice trunk network module or port adapter. On a Cisco MC3810, the codec complexity setting applies to both HCMs if two HCMs are installed.


Note


On Cisco 2600, Cisco 3600, and Cisco 3700 series routers with digital T1/E1 packet voice trunk network modules, codec complexity cannot be configured if DS0 or PRI groups are configured. If DS0 or PRI groups are configured, see the Changing Codec Complexity.


To configure codec complexity for digital voice ports on the Cisco 880 series, Cisco 2600 series, Cisco 3600 series, and Cisco 3700 series routers, and for voice ports on HCMs on the Cisco MC3810, use the following commands:

SUMMARY STEPS

    1.    enable

    2.    show voice dsp

    3.    configure terminal

    4.    voice-card slot

    5.    codec complexity {high | medium}


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Router> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.
     
    Step 2 show voice dsp


    Example:
    Router# show voice dsp
     

    Checks the DSP voice channel activity. If any DSP voice channels are in the busy state, codec complexity cannot be changed. When all DSP channels are in the idle state, continue to Step 2.

     
    Step 3 configure terminal


    Example:
    Router# configure terminal
     

    Enters global configuration mode.

     
    Step 4 voice-card slot


    Example:
    Router(config)# voice-card 0
     

    Enters voice card-configuration mode for the card or cards in the slot specified. Range is 0 to 5.

     
    Step 5 codec complexity {high | medium}


    Example:
    Router(config-voicecard)# codec complexity high
     

    Specifies codec complexity based on the codec standard being used. This setting restricts the codecs available in dial peer configuration. All voice cards in a router must use the same codec complexity setting. Default is medium.

    Note   

    On the Cisco MC3810, this command is valid only with one or more HCMs installed, and voice card 0 must be specified. If two HCMs are installed, this command configures both HCMs at once.

     

    Changing Codec Complexity

    To change codec complexity on Cisco 880 Series, Cisco 2600 Series, Cisco 3600 Series, Cisco 3700 Series, and Cisco MC3810 after the controller and voice ports have already been configured, use the following commands:


    Note


    Use the show voice dsp command to check the DSP voice channel activity. If any DSP voice channels are in the busy state, the codec complexity cannot be changed. You must clear all calls before performing the following task.


    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    voice-port slot / port:ds0-group-number

      4.    shutdown

      5.    exit

      6.    controller {t1 | e1} slot/port

      7.    Do one of the following:

      • no ds0-group ds0-group-number
      • no pri-group timeslots timeslot-list

      8.    exit

      9.    voice-card slot

      10.    codec complexity {high | medium} [ecan-extended]

      11.    exit

      12.    Repeat Step 6, then continue with Step 13.

      13.    Do one of the following:

      • ds0-group ds0-group-number timeslots timeslot - list type {e&m-immediate | e&m-delay | e&m-wink-start | fxs-ground-start | fxs-loop-start | fxo-ground-start | fxo-loop-start}
      • pri-group timeslots timeslot - list

      14.    exit

      15.    Repeat Step 3, then continue with Step 16.

      16.    no shutdown

      17.    end


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example:
      Router> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.
       
      Step 2 configure terminal


      Example:
      Router# configure terminal
       

      Enters global configuration mode.

       
      Step 3 voice-port slot / port:ds0-group-number


      Example:
      Router(config)# voice-port 1/0:23
       

      Enters voice-port configuration mode on the selected slot, port, and DS0 group.

      Note   

      The syntax of this command is platform-specific. For the syntax for your platform, refer to the Cisco IOS Voice Command Reference.

      Note   

      For the Cisco 880 series platforms, the command syntax does not include a slot number, only the port is identified. If the primary voice interface is FXS and the backup is BRI, then ports 0, 1, 2, and 3 are analog voice ports, and ports 4 and 5 are digital. If the primary voice interface is BRI, then ports 1, 2, 3, and 4 are digital.

       
      Step 4 shutdown


      Example:
      Router(config-voiceport)# shutdown
       

      Shuts down all voice ports assigned to the T1 interface on the voice card.

       
      Step 5 exit


      Example:
      Router(config-voiceport)# exit
       

      Exits voice-port configuration mode.

       
      Step 6 controller {t1 | e1} slot/port

      Example:
      Router(config)# controller t1 1/0
       

      Enters controller configuration mode on the T1 controller on the selected slot and port.

       
      Step 7Do one of the following:
      • no ds0-group ds0-group-number
      • no pri-group timeslots timeslot-list


      Example:
      Router(config-controller)# no ds0-group 1


      Example:
      Router(config-controller)# no pri-group timeslots 1,7,9
       

      Removes the related DS0 groups.

      or

      Removes the related PRI group.

       
      Step 8 exit


      Example:
      Router(config-controller) exit
       

      Exits controller configuration mode and returns to global configuration mode.

       
      Step 9 voice-card slot

      Example:
      Router(config)# voice-card 1
       

      Enters voice-card configuration mode on the specified slot.

      • slot--Slot number of the voice card. Range is 0 to 6, depending on platform.
       
      Step 10 codec complexity {high | medium} [ecan-extended]


      Example:
      Router(voice-card)# codec complexity high ecan-extended


      Example:
      
       
      		  
       

      Changes codec complexity or changes the echo canceller (EC) from the proprietary Cisco G.165 EC to the G.168 extended EC.

      • high --Supports up to six voice or fax calls per DSP module (PVDM-12), using the codecs: G.723, G.728, G.729, G.729 Annex B, GSMEFR, GSMFR, fax relay, or any of the medium complexity codecs.
      • medium --Supports up to 12 voice or fax calls per DSP module (PVDM-12), using the codecs: G.711, G.726, G.729 Annex A, G.729 Annex A with Annex B, and fax relay. Default value.
      • ecan-extended --(Optional) Selects the G.168 extended echo canceller. For more information, see the "How to Configure the Extended G.168 Echo Canceller" section.

      Specifying the codec complexity restricts the codecs available in dial-peer configuration mode. All voice cards in a gateway must use the same codec complexity.

       
      Step 11 exit


      Example:
      Router(voice-card) exit
       

      Exits voice-card configuration mode and returns to global configuration mode.

       
      Step 12 Repeat Step 6, then continue with Step 13.  

      --

       
      Step 13Do one of the following:
      • ds0-group ds0-group-number timeslots timeslot - list type {e&m-immediate | e&m-delay | e&m-wink-start | fxs-ground-start | fxs-loop-start | fxo-ground-start | fxo-loop-start}
      • pri-group timeslots timeslot - list


      Example:
      Router(config-controller)# ds0-group 0 timeslots 1-24 type e&m-wink-start


      Example:
      Router(config-controller)# pri-group timeslots 1,7,9
       

      Defines the T1 or E1 channels for use by compressed voice calls and the signaling method that the router uses to connect to the PBX or CO.

      Note   

      If you are configuring PRI groups instead of DS0 groups, omit this step and proceed to Step 15.

      or

      Specifies an ISDN PRI on a channelized T1 or E1 controller.

      Note   

      When configuring PRI groups, you must also configure the isdn switch-type command. Also, only one PRI group can be configured on a controller.

       
      Step 14 exit


      Example:
      Router(config-controller)# exit
       

      Exits controller configuration mode and completes the process for adding back the PRI groups or DS0 groups.

       
      Step 15 Repeat Step 3, then continue with Step 16.  

      --

       
      Step 16 no shutdown


      Example:
      Router(config-controller)# no shutdown
       

      Saves the controller configurations on the slot and port specified.

       
      Step 17 end


      Example:
      Router(config-controller)# end
       

      Exits controller configuration mode and completes the process for bringing the T1 controller back up.

       

      Configuring the Flex Option on Codec Complexity

      The IP Communications High-Density Digital Voice/Fax Network Module feature enables the flex option for configuring codec complexity.

      On the Cisco 2600 XM, Cisco 2691, Cisco 3700 series routers, codec complexity can be configured using the flex option for configuring codec complexity. This option allows the DSP to process up to 16 channels. In addition to continuing support for configuring a fixed number of channels per DSP, the flex option enables the DSP to handle a flexible number of channels. The total number of supported channels varies from 6 to 16, depending on which codec is used for a call. Therefore, the channel density varies from 6 per DSP (high-complexity codec) to 16 per DSP (g.711 codec).

      The following requirements apply to the IP Communications High-Density Digital Voice/Fax Network Module feature.

      • When the IP Communications High-Density Digital Voice/Fax Network Module feature is used in a Cisco CallManager network, the CCM 4.0(1) SR1 or CCM 3.3(4) release must be installed.
      • Software echo cancellation is the default configuration--G.168-compliant echo cancellation is enabled by default with a coverage of 64 milliseconds.
      • Only Packet Fax/Voice DSP modules (PVDM2s) are supported on the IP Communications High-Density Digital Voice/Fax Network Module.
      • Only voice interface cards that start with VIC2 are supported in the IP Communications High-Density Digital Voice/Fax Network Module feature except for VIC-1J1, VIC-2DID, and VIC-4FXS/DID.
      • The direct inward dial (DID) feature in VIC-4FXS/DID is not supported.
      • The CAMA card (VIC-2CAMA) is not supported. Any port on the VIC2-2FXO and the VIC2-4FXO can be software configured to support analog CAMA for dedicated E-911 services (North America only).

      Codec Combinations for DSP Sharing:

      When network modules or PVDM2s on the motherboard are configured for DSP sharing, the codec complexity has to match. A local resource sharing or importing from a remote network module must match its characteristics, that is, a high-complexity network module can only share from another high-complexity network module, whereas a flex-complexity network module can share DSPs from both high-complexity and flex-complexity network modules. The table below summarizes the codec combinations for DSP-sharing.

      Using Flex Mode

      In flex mode, you can connect (or configure in the case of DS0 groups and PRI groups) more voice channels to the module than the DSPs can accommodate. This is referred to as oversubscription. If all voice channels should go active simultaneously, the DSPs will be oversubscribed and calls that are unable to allocate a DSP resource will fail to connect.


      Caution


      If you are configuring a Cisco 2600 XM router, you should not use the network-clock-participate command for slot 1 of the router. This may cause a disruption in service to the router.


      Table 2 Codec Complexity Settings for DSP Resource Sharing Between Local and Remote Sources

      Local DSP Resource (Import)

      Remote DSP Resource (Export)

      High complexity

      Medium complexity

      Flexible complexity

      High complexity

      Yes

      No

      No

      Medium complexity

      Yes

      Yes

      No

      Flexible complexity

      Yes

      No

      Yes

      To enable the IP Communications Voice/Fax Network Module feature, perform this task to configure the voice card for the flex option in codec complexity.

      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    voice-card slot

        4.    codec complexity flex [reservation - fixed {high | medium}]

        5.    voice local-bypass

        6.    exit


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 enable


        Example:
        Router> enable
         

        Enables privileged EXEC mode.

        • Enter your password if prompted.
         
        Step 2 configure terminal


        Example:
        Router# configure terminal
         

        Enters global configuration mode.

         
        Step 3 voice-card slot


        Example:
        Router(config)# voice-card 1
         

        Enters voice-card configuration mode and specifies the slot location.

        • For the slotargument, specify a value from 1 to 4, depending on your router.
         
        Step 4 codec complexity flex [reservation - fixed {high | medium}]


        Example:
        Router(config-voicecard)# codec complexity flex
         

        Specifies the flex option for codec complexity.

        • flex --Up to 16 calls can be completed per DSP. The number of supported calls varies from 6 to 16, depending on the codec used for a call. In this mode, reservation for analog VICs may be needed for certain appplications such as CAMA E-911 calls because oversubscription of DSPs is possible. If this is true, then the reservation-fixed option may be enabled. There is no reservation by default.
          • reservation-fixed--Appears as an option only when there is an analog VIC present. Ensures that sufficient DSP resources are available to handle a call. If you enter this keyword, then specify if the complexity should be high or medium.
        Note   

        You cannot change codec complexity while DS0 groups are defined. If they are already set up, perform the steps in the Changing Codec Complexity.

         
        Step 5 voice local-bypass


        Example:
        Router(config-voicecard)# voice local-bypass
         

        Configures local calls to bypass the DSP. This is the default.

        • Using this command enables intranetwork-module hairpinning (no DSPs).
        Note   

        For POTS-to-POTS calls between two network modules, hairpinning is not supported. If the connection manager in Cisco IOS software does not automatically handle this, it might be necessary to disable local-bypass so that DSPs are used for these calls.

         
        Step 6 exit


        Example:
        Router(config-voicecard)# exit
         

        Exits voice-card configuration mode and returns the router to global configuration mode.

         

        Configuring Codec Complexity

        On Cisco 7200 series and Cisco 7500 series routers, codec complexity is configured in the DSP interface.


        Note


        Use the show interfaces dspfarmcommand to check the DSP voice channel activity. If any DSP voice channels are in the busy state, the codec complexity cannot be changed. You must clear all calls before performing the following task.


        SUMMARY STEPS

          1.    enable

          2.    configure terminal

          3.    Do one of the following:

          • dspint dspfarm slot /0
          • dspint dspfarm slot / port-adapter / port

          4.    codec {high | medium} [ecan-extended]

          5.    exit


        DETAILED STEPS
           Command or ActionPurpose
          Step 1 enable


          Example:
          Router> enable
           

          Enables privileged EXEC mode.

          • Enter your password if prompted.
           
          Step 2 configure terminal


          Example:
          Router# configure terminal
           

          Enters global configuration mode.

           
          Step 3Do one of the following:
          • dspint dspfarm slot /0
          • dspint dspfarm slot / port-adapter / port


          Example:
          Router(config)# dspint dspfarm 2/0
           

          Enters DSP interface configuration mode for the Cisco 7200 series.

          or

          Enters DSP interface configuration mode for the Cisco 7500 series.

           
          Step 4 codec {high | medium} [ecan-extended]


          Example:
          Router(config-dspfarm)# codec medium ecan-extended
           

          Sets the codec complexity.

          • The optional ecan-extended keyword selects the G.168 extended echo canceller. This keyword is supported only in Cisco IOS Release 12.2(13)T. For more information, see the "How to Configure the Extended G.168 Echo Canceller" section.
          • This command affects the choice of codecs available when the codec command is used in dial-peer configuration mode.
           
          Step 5 exit


          Example:
          Router(config-dspfarm)# exit
           

          Exits to global configuration mode.

           
          What to Do Next

          Cisco 7200 Series:

          On the Cisco 7200 series, the PA-MCX-2TE1 port adapter (PA) card can be used for making voice calls. This PA does not have any DSPs but uses the DSP resources of the PA-VXC-2TE1+ card present in another slot. If the PA-MCX card is used, codec complexity is configured for PA-VXC, while all other echo cancellation configurations are done for PA-MCX.

          The PA-MCX card borrows the DSP resources from the PA-VXC, PA-VXB, or PA-VXA card. If one of the PA-VXC, PA-VXB, or PA-VXA cards has extended echo cancellation configured on the DSP interface, extended echo cancellation is enabled for the PA-MCX card. It is recommended that you have the same codec complexity and echo cancellation configuration on all the PA-VXC, PA-VXB, or PA-VXA cards in the router.

          Cisco AS5300:

          Codec support on the Cisco AS5300 is determined by the capability list on the voice feature card, which defines the set of codecs that can be negotiated for a voice call. The capability list is created and populated when VCWare is unbundled and DSPWare is added to VFC flash memory. The capability list does not indicate codec preference; it simply reports the codecs that are available. The session application decides which codec to use. Codec support is configured on dial peers rather than on voice ports; refer to the "Dial Peer Configuration on Voice Gateway Routers" document.

          Cisco AS5800:

          Codec support is selected on Cisco AS5800 access servers during dial peer configuration. Refer to the "Dial Peer Configuration on Voice Gateway Routers" document.

          Configuring Controller Settings for Digital T1 E1 Voice Ports

          The controller configuration for digital T1/E1 voice ports must match the line characteristics of the telephony network connection so that voice and signaling can be transferred between them and so that logical voice ports, or DS0 groups, may be established.

          Specific line characteristics must be configured to match those of the PSTN line that is being connected to the voice port. These are typically configured in controller configuration mode.

          The figure below shows how a ds0-group command gathers some of the DS0 time slots from a T1 line into a group that becomes a single logical voice port that can later be addressed as a single entity in voice port configurations. Other DS0 groups for voice can be created from the remaining time slots shown in the figure, or the time slots can be used for data or serial pass-through.


          Note


          All controller commands shown in the figure below, other than ds0-group, apply to all time slots in the T1 line.


          Figure 1. T1 Controller Configuration on Cisco 2600 or Cisco 3600 Series Routers

          Voice port controller configuration includes setting the parameters described in the following sections:

          Another controller command that might be needed, cablelength, is discussed in the Cisco IOS Interface and Hardware Component Command Reference.

          Framing Formats on Digital T1 E1 Voice Ports

          The framing format parameter describes the way that bits are robbed from specific frames to be used for signaling purposes. The controller must be configured to use the same framing format as the line from the PBX or CO that connects to the voice port you are configuring.

          Digital T1 lines use SF or ESF framing formats. SF provides two-state, continuous supervision signaling, in which bit values of 0 are used to represent on-hook and bit values of 1 are used to represent off-hook. ESF robs four bits instead of two, yet has little impact on voice quality. ESF is required for 64-kbps operation on DS0 and is recommended for PRI configurations.

          E1 lines can be configured for CRC4 or no cyclic redundancy check, with an optional argument for E1 lines in Australia.

          Clock Sources on Digital T1 E1 Voice Ports

          Digital T1/E1 interfaces use timers called clocks to ensure that voice packets are delivered and assembled properly. All interfaces handling the same packets must be configured to use the same source of timing so that packets are not lost or delivered late. The timing source that is configured can be external (from the line) or internal to the router’s digital interface.

          If the timing source is internal, timing derives from the onboard phase-lock loop (PLL) chip in the digital voice interface. If the timing source is line (external), then timing derives from the PBX or PSTN CO to which the voice port is connected. It is generally preferable to derive timing from the PSTN becauseits clocks are maintained at an extremely accurate level. This is the default setting for the clocks. When two or more controllers are configured, one should be designated as the primary clock source; it will drive the other controllers.

          The line keyword specifies that the clock source is derived from the active line rather than from the free-running internal clock. The following rules apply to clock sourcing on the controller ports:

          • When both ports are set to line clocking with no primary specification, port 0 is the default primary clock source and port 1 is the default secondary clock source.
          • When both ports are set to line and one port is set as the primary clock source, the other port is by default the backup or secondary source and is loop-timed.
          • If one port is set to clock source line or clock source line primary and the other is set to clock source internal, the internal port recovers clock from the clock source line port if the clock source line port is up. If it is down, then the internal port generates its own clock.
          • If both ports are set to clock source internal, there is only one clock source: internal.

          This section describes the five basic timing scenarios that can occur when a digital voice port is connected to a PBX or CO. In all the examples that follow, the PSTN (or CO) and the PBX are interchangeable for purposes of providing or receiving clocking.

          • Single voice port providing clocking--In this scenario, the digital voice hardware is the clock source for the connected device, as shown in the figure below. The PLL generates the clock internally and drives the clocking on the line. Generally, this method is useful only when connecting to a PBX, key system, or channel bank. A Cisco VoIP gateway rarely provides clocking to the CO because CO clocking is much more reliable. The following configuration sets up this clocking method for a digital E1 voice port:
          controller E1 1/0
           framing crc4
           linecoding hdb3
           clock source internal
           ds0-group timeslots 1-15 type e&m-wink-start
          Figure 2. Single Voice Port Providing Clocking

          • Single voice port receiving internal clocking--In this scenario, the digital voice hardware receives clocking from the connected device (CO telephony switch or PBX) (see the figure below). The PLL clocking is driven by the clock reference on the receive (Rx) side of the digital line connection.
          Figure 3. Single E1 Port Receiving Clocking from the Line

          The following configuration sets up this clocking method:

          controller T1 1/0
           framing esf
           linecoding ami
           clock source line
           ds0-group timeslots 1-12 type e&m-wink-start
          
          • Dual voice ports receiving clocking from the Line--In this scenario, the digital voice port has two reference clocks, one from the PBX and another from the CO, as shown in the figure below.
          Figure 4. Dual E1 Ports Receiving Clocking from the Line

          Because the PLL can derive clocking from only one source, this case is more complex than the two preceding examples. Before looking at the details, consider the following as they pertain to the clocking method:

            • Looped-time clocking--The voice port takes the clock received on its Rx (receive) pair and regenerates it on its Tx (transmit) pair. While the port receives clocking, the port is not driving the PLL on the card but is "spoofing" (that is, fooling) the port so that the connected device has a viable clock and does not see slips (that is, loss of data bits). PBXs are not designed to accept slips on a T1 or E1 line, and such slips cause a PBX to drop the link into failure mode. While in looped-time mode, the router often sees slips, but because these are controlled slips, they usually do not force failures of the router’s voice port.
            • Slips--These messages indicate that the voice port is receiving clock information that is out of phase (out of synchronization). Because the router has only a single PLL, it can experience controlled slips while it receives clocking from two different time sources. The router can usually handle controlled slips because its single-PLL architecture anticipates them.

          Note


          Physical layer issues, such as bad cabling or faulty clocking references, can cause slips. Eliminate these slips by addressing the physical layer or clock reference problems.


          In the dual voice ports receiving clocking from the line scenario, the PLL derives clocking from the CO and puts the voice port connected to the PBX into looped-time mode. This is usually the best method because the CO provides an excellent clock source (and the PLL usually requires that the CO provide that source) and a PBX usually must receive clocking from the other voice port.

          The following configuration sets up this clocking method (controller E1 1/0 is connected to the CO; controller E1 1/1 is connected to the PBX:

          controller E1 1/0
           framing crc4
           linecoding hdb3
           clock source line primary
           ds0-group timeslots 1-15 type e&m-wink-start
          !
          controller E1 1/1
           framing crc4
           linecoding hdb3
           clock source line
           ds0-group timeslots 1-15 type e&m-wink-start
          

          The clock source line primary command tells the router to use this voice port to drive the PLL. All other voice ports configured as clock source line are then put into an implicit loop-timed mode. If the primary voice port fails or goes down, the other voice port instead receives the clock that drives the PLL. In this configuration, port 1/1 might see controlled slips, but these should not force it down. This method prevents the PBX from seeing slips.


          Note


          When two T1/E1 lines terminate on a two-port interface card, such as the VWIC-2MFT, and both controllers are set for line clocking but the lines are not within clocking tolerance of one another, one of the controllers is likely to experience slips. To prevent slips, ensure that the two T1 or E1 lines are within clocking tolerance of one another, even if the lines are from different providers.


          • Dual voice ports (one receives clocking and one provides clocking)--In this scenario, the digital voice hardware receives clocking for the PLL from E1 0 and uses this clock as a reference to clock E1 1 (see the figure below). If controller E1 0 fails, the PLL internally generates the clock reference to drive E1 1.
          Figure 5. Dual E1 Ports--One Receiving and One Providing Clocking

          The following configuration sets up this clocking method:

          controller E1 1/0
           framing crc4
           linecoding hdb3
           clock source line 
           ds0-group timeslots 1-15 type e&m-wink-start
          !
          controller E1 1/1
           framing crc4
           linecoding hdb3
           clock source internal
           ds0-group timeslots 1-15 type e&m-wink-start
          
          • Dual voice ports (router provides both clocks)--In this scenario, the router generates the clock for the PLL and, therefore, for both voice ports (see the figure below).
          Figure 6. Dual E1 Ports--Both Clocks from the Router

          The following configuration sets up this clocking method:

          controller E1 1/0
           framing crc4
           linecoding hdb3
           clock source internal
           ds0-group timeslots 1-15 type e&m-wink-start
          !
          controller E1 1/1
           framing esf
           linecoding b8zs
           clock source internal
           ds0-group timeslots 1-15 type e&m-wink-start

          Network Clock Timing

          Voice systems that pass digitized (pulse code modulation or PCM) speech have always relied on the clocking signal being embedded in the received bit stream. This reliance allows connected devices to recover the clock signal from the bit stream, and then use this recovered clock signal to ensure that data on different channels keep the same timing relationship with other channels.

          If a common clock source is not used between devices, the binary values in the bit streams may be misinterpreted because the device samples the signal at the wrong moment. As an example, if the local timing of a receiving device is using a slightly shorter time period than the timing of the sending device, a string of eight continuous binary 1s may be interpreted as nine continuous 1s. If this data is then re-sent to further downstream devices that used varying timing references, the error could be compounded. By ensuring that each device in the network uses the same clocking signal, you can ensure the integrity of the traffic.

          If timing between devices is not maintained, a condition known as clock slip can occur. Clock slip is the repetition or deletion of a block of bits in a synchronous bit stream due to a discrepancy in the read and write rates at a buffer.

          Slips are caused by the inability of an equipment buffer store (or other mechanisms) to accommodate differences between the phases or frequencies of the incoming and outgoing signals in cases where the timing of the outgoing signal is not derived from that of the incoming signal.

          A T1 or E1 interface sends traffic inside repeating bit patterns called frames. Each frame is a fixed number of bits, allowing the device to see the start and end of a frame. The receiving device also knows exactly when to expect the end of a frame simply by counting the appropriate number of bits that have come in. Therefore, if the timing between the sending and receiving device is not the same, the receiving device may sample the bit stream at the wrong moment, resulting in an incorrect value being returned.

          Even though Cisco IOS software can be used to control the clocking on these platforms, the default clocking mode is effectively free running, meaning that the received clock signal from an interface is not connected to the backplane of the router and used for internal synchronization between the rest of the router and its interfaces. The router will use its internal clock source to pass traffic across the backplane and other interfaces.

          For data applications, this clocking generally does not present a problem as a packet is buffered in internal memory and is then copied to the transmit buffer of the destination interface. The reading and writing of packets to memory effectively removes the need for any clock synchronization between ports.

          Digital voice ports have a different issue. It would appear that unless otherwise configured, Cisco IOS software uses the backplane (or internal) clocking to control the reading and writing of data to the DSPs. If a PCM stream comes in on a digital voice port, it will be using the external clocking for the received bit stream. However, this bit stream will not necessarily be using the same reference as the router backplane, meaning the DSPs may misinterpret the data coming in from the controller.

          This clocking mismatch is seen on the router’s E1 or T1 controller as a clock slip--the router is using its internal clock source to send the traffic out the interface but the traffic coming in to the interface is using a completely different clock reference. Eventually, the difference in the timing relationship between the transmit and receive signal becomes so great that the controller registers a slip in the received frame.

          To eliminate the problem, change the default clocking behavior through Cisco IOS configuration commands. It is absolutely critical to set up the clocking commands properly.

          Even though these commands are optional, we strongly recommend you enter them as part of your configuration to ensure proper network clock synchronization:

          network-clock-participate [slot slot-number | wic wic-slot | aim aim-slot-number network-clock-select priority{bri | t1 | e1} slot / port

          The network-clock-participate command allows the router to use the clock from the line via the specified slot/WIC/AIM and synchronize the onboard clock to the same reference.

          If multiple VWICS are installed, the commands must be repeated for each installed card. The system clocking can be confirmed using the show network clocks command.


          Caution


          If you are configuring a Cisco 2600 XM voice gateway with an NM-HDV2 or NM-HD-2VE installed in slot 1, do not use the network-clock-participate slot 1 command in the configuration. In this particular hardware scenario, the network-clock-participate slot 1 command is not necessary. If the network-clock-participate slot 1 command is configured, voice and data connectivity on interfaces terminating on the NM-HDV2 or NM-HD-2VE network module may fail to operate properly. Data connectivity to peer devices may not be possible, and even loopback plug tests to the serial interface spawned via a channel group configured on the local T1/E1 controller will fail. Voice groups such as CAS DS0 groups and ISDN PRI groups may fail to signal properly. The T1/E1 controller may accumulate large amounts of timing slips and Path Code Violations (PCVs) and Line Code Violations (LCVs).


          Line Coding on Digital T1 E1 Voice Ports

          Digital T1/E1 interfaces require that line encoding be configured to match that of the PBX or CO that is being connected to the voice port. Line encoding defines the type of framing used on the line.

          T1 line encoding methods include AMI and B8ZS. AMI is used on older T1 circuits and references signal transitions with a binary 1, or "mark." B8ZS, a more reliable method, is more popular and is recommended for PRI configurations as well. B8ZS encodes a sequence of eight zeros in a unique binary sequence to detect line-coding violations.

          Supported E1 line encoding methods are AMI and HDB3, which is a form of zero-suppression line coding.

          DS0 Groups on Digital T1 E1 Voice Ports

          For digital voice ports, a single command, ds0-group, performs the following functions:

          • Defines the T1/E1 channels for compressed voice calls.
          • Automatically creates a logical voice port.

          The numbering for the logical voice port created as a result of this command is controller:ds0-group-number , where controller is defined as the platform-specific address for a particular controller. On a Cisco 3640 router, for example, ds0-group 1 timeslots 1-24 type e&m-wink automatically creates the voice port 1/0:1 when issued in the configuration mode for controller 1/0. On a Cisco MC3810 universal concentrator, when you are in the configuration mode for controller 0, the ds0-group 1 timeslots 1-24 type e&m-winkcommand creates logical voice port 0:1.

          To map individual DS0s, define additional DS0 groups under the T1/E1 controller, specifying different time slots. Defining additional DS0 groups also creates individual DS0 voice ports.

          • Defines the emulated analog signaling method that the router uses to connect to the PBX or PSTN.

          Most digital T1/E1 connections used for switch-to-switch (or switch-to-router) trunks are E&M connections, but FXS and FXO connections are also supported. These are normally used to provide emulated-OPX (Off-Premises eXtension) from a PBX to remote stations. FXO ports connect to FXS ports. The FXO or FXS connection between the router and switch (CO or PBX) must use matching signaling, or calls cannot connect properly. Either ground-start or loop-start signaling is appropriate for these connections. Ground-start provides better disconnect supervision to detect when a remote user has hung up the telephone, but ground-start is not available on all PBXs.

          Digital ground start differs from digital E&M because the A and B bits do not track each other as they do in digital E&M signaling (that is, A is not necessarily equal to B). When the CO delivers a call, it seizes a channel (goes off-hook) by setting the A bit to 0. The CO equipment also simulates ringing by toggling the B bit. The terminating equipment goes off-hook when it is ready to answer the call. Digits are usually not delivered for incoming calls.

          E&M connections can use one of three different signaling types to acknowledge on-hook and off-hook states: wink start, immediate-start, and delay-start. E&M wink start is usually preferred, but not all COs and PBXs can handle wink-start signaling. The E&M connection between the router and switch (CO or PBX) must match the CO or PBX E&M signaling type, or calls cannot be connected properly.

          E&M signaling is normally used for trunks. It is normally the only way that a CO switch can provide two-way dialing with DID. In all the E&M protocols, off-hook is indicated by A=B=1 and on-hook is indicated by A=B=0 (robbed-bit signaling). If dial pulse dialing is used, the A and B bits are pulsed to indicate the addressing digits. The are several further important subclasses of E&M robbed-bit signaling:

            • E&M wink-start--Feature Group B

          In the original wink start handshaking protocol, the terminating side responds to an off-hook from the originating side with a short wink (transition from on-hook to off-hook and back again). This wink tells the originating side that the terminating side is ready to receive addressing digits. After receiving addressing digits, the terminating side then goes off-hook for the duration of the call. The originating endpoint maintains off-hook for the duration of the call.

            • E&M wink-start--Feature Group D

          In Feature Group D wink-start with wink acknowledge handshaking protocol, the terminating side responds to an off-hook from the originating side with a short wink (transition from on-hook to off-hook and back again) just as in the original wink-start. This wink tells the originating side that the terminating side is ready to receive addressing digits. After receiving addressing digits, the terminating side provides another wink (called an acknowledgment wink ) that tells the originating side that the terminating side has received the dialed digits. The terminating side then goes off-hook to indicate connection. This last indication can be due to the ultimate called endpoint’s having answered. The originating endpoint maintains an off-hook condition for the duration of the call.

            • E&M immediate-start

          In the immediate-start protocol, the originating side does not wait for a wink before sending addressing information. After receiving addressing digits, the terminating side then goes off-hook for the duration of the call. The originating endpoint maintains off-hook for the duration of the call.


          Note


          Feature Group D is supported on Cisco AS5300 platforms, and on Cisco 2600, Cisco 3600, and Cisco 7200 series with digital T1 packet voice trunk network modules. Feature Group D is not supported on E1 or analog voice ports.


          To configure controller settings for digital T1/E1 voice ports, use the following commands:

          SUMMARY STEPS

            1.    enable

            2.    configure terminal

            3.    card type {t1 | e1} slot

            4.    Do one of the following:

            • controller {t1 | e1} slot / port
            • controller {t1 | e1} number
            • controller {t1 | e1} shelf / slot / port

            5.    Do one of the following:

            • framing {sf | esf}
            • framing {crc4 | no-crc4} [australia]

            6.    clock source {line [primary | secondary] | internal}

            7.    Do one of the following:

            • linecode {ami | b8zs}
            • linecode {ami | hdb3}

            8.    ds0-group ds0-group-number timeslots timeslot-list type {e&m-delay-dial | e&m-fgd | e&m-immediate-start|e&m-wink-start | ext-sig | fgd-eana | fxo-ground-start | fxo-loop-start | fxs-ground-start | fxs-loop-start}

            9.    no shutdown


          DETAILED STEPS
             Command or ActionPurpose
            Step 1 enable


            Example:
            Router> enable
             

            Enables privileged EXEC mode.

            • Enter your password if prompted.
             
            Step 2 configure terminal


            Example:
            Router# configure terminal
             

            Enters global configuration mode.

             
            Step 3 card type {t1 | e1} slot


            Example:
            Router(config)# card type t1 0
             

            Defines the card as T1 or E1 and identifies the location.

             
            Step 4Do one of the following:
            • controller {t1 | e1} slot / port
            • controller {t1 | e1} number
            • controller {t1 | e1} shelf / slot / port


            Example:
            Router(config)# controller t1 1/0


            Example:
                      


            Example:
            Router(config)# controller t1 1


            Example:
            or 


            Example:
            Router(config)# controller t1 1/0/0
             

            Enters controller configuration mode and specifies either T1 or E1 for the line.

            • For the Cisco 2600, Cisco 3600 series, Cisco MC3810, and Cisco 7200 series, identifies the slot and port.
            • For the Cisco AS5300, identifies the port number.
            • For the Cisco AS5800 and Cisco 7500 series, identifies the shelf, slot, and port number.
             
            Step 5Do one of the following:
            • framing {sf | esf}
            • framing {crc4 | no-crc4} [australia]


            Example:
            Router(config-controller)# framing esf


            Example:
            
             
            		  


            Example:
                      


            Example:
            Router(config-controller)# framing crc4
             

            Selects frame type for T1 or E1 line.

            • For T1, the frame type can be sf or esf. Default for T1 is sf.
            • For E!, the frame type can be crc4 or no crc4 or australia. Default for E1 is crc4.
             
            Step 6 clock source {line [primary | secondary] | internal}


            Example:
            Router(config-controller)# clock source line primary
             

            Configures the clock source.

             
            Step 7Do one of the following:
            • linecode {ami | b8zs}
            • linecode {ami | hdb3}


            Example:
            Router(config-controller)# linecode b8zs


            Example:
                      


            Example:
            Router(config-controller)# linecode hdb3
             

            Specifies the line encoding to use for T1 or E1 line.

            • For T1, the line encoding can be ami or b8zs. Default for T1 is ami.
            • For E1, the line encoding can be ami or hdb3. Default for E1 is hdb3.
             
            Step 8 ds0-group ds0-group-number timeslots timeslot-list type {e&m-delay-dial | e&m-fgd | e&m-immediate-start|e&m-wink-start | ext-sig | fgd-eana | fxo-ground-start | fxo-loop-start | fxs-ground-start | fxs-loop-start}


            Example:
            Router(config-controller)# ds0-group 30 timeslots 0 type e&m-immediate-start
             

            Defines the T1 channels for use by compressed voice calls and the signaling method that the router uses to connect to the PBX or CO.

            Note   

            This step shows the basic syntax and signaling types available with the ds0-group command. For the complete syntax, refer to the Cisco IOS Voice Command Reference.

             
            Step 9 no shutdown


            Example:
            Router(config-controller)# no shutdown
             

            Activates the controller.

             

            Configuring Basic Voice Port Parameters for Digital T1 E1 Voice Ports

            For FXO and FXS connections the default voice-port parameter values are often adequate. However, for E&M connections, it is important to match the characteristics of your PBX, so voice port parameters may need to be reconfigured from their defaults.

            Each voice port that you address in digital voice port configuration is one of the logical voice ports that you created with the ds0-group command.

            Companding (from compression and expansion), used in Step 6 of the following table, is the part of the PCM process in which analog signal values are logically rounded to discrete scale-step values on a nonlinear scale. The decimal step number is then coded in its binary equivalent prior to transmission. The process is reversed at the receiving terminal using the same nonlinear scale.

            Voice-port configuration mode allows many of the basic voice call attributes to be configured to match those of the PSTN or PBX connection being made on this voice port.

            In addition to the basic voice port parameters, there are commands that allow for the fine- tuning of the voice port configurations or for configuration of optional features. In most cases, the default values for these commands are sufficient for establishing voice port configurations. If it is necessary to change some of these parameters to improve voice quality or to match parameters in proprietary PBXs to which you are connecting, use the commands in the "Fine-Tuning Analog and Digital Voice Ports" section.

            After voice port configuration, make sure the ports are operational by following the steps described in these chapters:

            For more information on voice port commands, refer to the Cisco IOS Voice Command Reference


            Note


            The commands, keywords, and arguments that you are able to use may differ slightly from those presented here, based on your platform, Cisco IOS release, and configuration. When in doubt, use Cisco IOS command help to determine the syntax choices that are available.


            To configure basic parameters for digital T1/E1 voice ports, use the following commands:

            SUMMARY STEPS

              1.    enable

              2.    configure terminal

              3.    Do one of the following:

              • voice-port port
              • voice-port slot / port:ds0-group-number
              • voice-port slot / port-adapter :ds0-group-number
              • voice-port slot / port-adapter/slot :ds0-group-number
              • voice-port controller :{ds0-group-number | D}
              • voice-port slot / controller :{ds0-group-number | D}
              • voice-port shelf / slot / port:ds0-group-number

              4.    type {1 | 2 | 3 | 5}

              5.    cptone locale

              6.    compand-type {u-law | a-law}

              7.    ring frequency {25 | 50}

              8.    ring number number

              9.    ring cadence {[pattern01 | pattern02 | pattern03 | pattern04 | pattern05 | pattern06 | pattern07 | pattern08 | pattern09 | pattern10 | pattern11 | pattern12] [define pulse interval]}

              10.    description string

              11.    no shutdown


            DETAILED STEPS
               Command or ActionPurpose
              Step 1 enable


              Example:
              Router> enable
               

              Enables privileged EXEC mode.

              • Enter your password if prompted.
               
              Step 2 configure terminal


              Example:
              Router# configure terminal
               

              Enters global configuration mode.

               
              Step 3Do one of the following:
              • voice-port port
              • voice-port slot / port:ds0-group-number
              • voice-port slot / port-adapter :ds0-group-number
              • voice-port slot / port-adapter/slot :ds0-group-number
              • voice-port controller :{ds0-group-number | D}
              • voice-port slot / controller :{ds0-group-number | D}
              • voice-port shelf / slot / port:ds0-group-number


              Example:
              Router(config)# voice-port 1:0


              Example:



              Example:
              Router(config)# voice-port 1/1:0


              Example:
              Router(config)# voice-port 1/1/1:1


              Example:
              Router(config)# voice-port 1:1


              Example:
              Router(config)# voice-port 1/0 D


              Example:
              Router(config)# voice-port 1/2/0:1
               

              Enters voice-port configuration mode and identifies the port to be configured.

              • For the Cisco 880 series, specify the port number.
              • For the Cisco 2600, Cisco 3600, and Cisco 3700 series, specify the slot, port, and DS0 group number.
              • For the Cisco 7200 series, specify the slot, port adapter,and DS0 group number.
              • For the Cisco 7500 series, specify the slot, port adapter, slot, and DS0 group number.
              • For the Cisco AS5300, specify the controller and DS0 group number or the keyword D.
              • For the Cisco AS5350, Cisco AS5400, and Cisco AS5850 universal gateways, specify the slot, controller, and DS0 group number or the keyword D.
              • For the Cisco AS5800, specify the shelf, slot, port, and DS0 group number.
               
              Step 4 type {1 | 2 | 3 | 5}


              Example:
              Router(config-voiceport)#
               
              type 1
               

              (E&M only) Specifies the type of E&M interface to which this voice port is connected. See Table 3 in the "Voice Port Configuration Overview" chapter for an explanation of E&M types.

              • Default is 1.
               
              Step 5 cptone locale


              Example:
              Router(config-voiceport)# cptone us
               

              Selects a two-letter locale keyword for the voice call progress tones and other locale-specific parameters to be used on this voice port. Voice call progress tones include dial tone, busy tone, and ringback tone, which vary with geographical region.

              • Other parameters include ring cadence and compand type. Cisco routers comply with the ISO3166 locale name standards; to see valid choices, enter a question mark (?) following the cptone command.
              • Default is us.
               
              Step 6 compand-type {u-law | a-law}


              Example:
              Router(config-voiceport)# compand-type u-law
               

              (Cisco 2600 and Cisco 3600 series routers.) Specifies the companding standard used. This command is used in cases when the DSP is not used, such as local cross-connects, and overwrites the compand-type value set by the cptone command.

              • The default for E1 is a-law.
              • The default for T1 is u-law.
              Note   

              If you have a Cisco 3660 router, the compand-type a-law command must be configured on the analog ports only. The Cisco 2660, 3620, and 3640 routers do not require the compand-type a-law command configured. However, if you request a list of commands, the compand-type a-law command will display.

               
              Step 7 ring frequency {25 | 50}


              Example:
              Router(config-voiceport)# ring frequency 50
               

              (FXS only) Selects the ring frequency, in hertz, used on the FXS interface. This number must match the connected telephony equipment, and can be country-dependent. If the ring frequency is not set properly, the attached telephony device may not ring or it may buzz.

              • Default is 25.
               
              Step 8 ring number number


              Example:
              Router(config-voiceport)# ring number 1
               

              (FXO only) Specifies the maximum number of rings to be detected before an incoming call is answered by the router.

              • Default is 1.
               
              Step 9 ring cadence {[pattern01 | pattern02 | pattern03 | pattern04 | pattern05 | pattern06 | pattern07 | pattern08 | pattern09 | pattern10 | pattern11 | pattern12] [define pulse interval]}


              Example:
              Router(config-voiceport)# ring cadence pattern01 define 12 15
               

              (FXS only) Specifies an existing pattern for ring, or defines a new one. Each pattern specifies a ring-pulse time and a ring-interval time. The keywords and arguments are as follows:

              • pattern01 through pattern12--Specifies preset ring cadence patterns. Enter ring cadence ? to see ring pattern explanations.
              • define pulse interval --Specifies a user-defined pattern as follows:
                • pulse is a number (1 or 2 digits from 1 to 50) specifying ring pulse (on) time in hundreds of milliseconds.
                • interval is a number (1 or 2 digits from 1 to 50) specifying ring interval (off) time in hundreds of milliseconds.
              • The default is the pattern specified by the configured cptone locale command.
               
              Step 10 description string


              Example:
              Router(config-voiceport)# description 1
               

              Attaches a text string to the configuration that describes the connection for this voice port. This description appears in various displays and is useful for tracking the purpose or use of the voice port. The string argument is a character string from 1 to 255 characters in length.

              • The default is that no description is attached to the configuration.
               
              Step 11 no shutdown


              Example:
              Router(config-voiceport)# no shutdown
               

              Activates the voice port.