Robbed Bit Signaling for the Cisco AS5200

Description

The Cisco AS5200 Universal Access Server supports different types of robbed bit signaling for receiving and transmitting analog calls. Robbed bit signaling emulates older analog trunk and line signal methods that are transmitted in many networks. In countries that support T1 framing (such as the United States and Canada), many networks send supervisory and signaling information to each other by removing the 8th bit of each timeslot of the 6th and 12th frame for superframe (SF) framing. For networks supporting extended superframe (ESF) framing, the 6th, 12th, 18th, and 24th frames are affected. Robbed bit signaling must be enabled on the Cisco AS5200's T1 lines. This is done to support channel banks in the network that convert various battery and ground operations on analog lines into signaling bits that are forwarded over digital lines.

Benefits

Robbed bit signaling configured on the Cisco AS5200 enables the integrated modems in the access server to answer and transmit analog calls.

List of Terms

The following term is defined for configuring robbed bit signaling on the Cisco AS5200.

E&M signaling--A two-way analog signal, such as on-hook and off-hook, that has two leads. The E lead is used for the receive signal. The M lead is used for the transmit signal. This signal is also known as ear and mouth signaling.

Prerequisites

The signal type configured on the access server must match the signal type offered by your telco provider. Ask your telco provider which signal type to configure on each T1 controller. The Cisco AS5200 has two controllers: controller T1 1 and controller T1 0.

Configuration Tasks

Both T1 controllers are configured individually. The Cisco AS5200 Universal Access Server is an ISDN-capable access server that can transmit and receive ISDN and analog calls from remote clients needing access to network resources.

On a Cisco AS5200, you can allocate the 24 available channels for channelized T1 in the following four ways:

All 24 channels can be configured to support ISDN PRI.
If you are not running PRI ISDN, all channels can be configured to support robbed bit signaling (also known as channel-associated signaling), which enables a Cisco AS5200 modem to receive and transmit analog calls.
All 24 channels can be configured in a single channel group.
Mix and match channels supporting ISDN PRI, robbed bit signaling, and channel grouping across the same T1 line.

For example, on the same channelized T1 you can configure the pri-group timeslots 1-10 command, channel-group 11 timeslots 11-16 command, and cas-group 17 timeslots 17-23 type e&m-fgb command. This is a rare configuration because it requires you to align the correct range of timeslots on both ends of the connection.

To configure the T1 controllers in the Cisco AS5200, perform the tasks in the following sections:

Configure the T1 Controllers to Transmit and Receive Calls

Set parameters for a T1 controller to make and receive calls. To do so, perform the following steps beginning in global configuration mode:

Task	Command
Step 1 Enable the T1 0 controller, and enter controller configuration mode.	controller t1 0
Step 2 If the channelized T1 line connects to a smart jack instead of a CSU, set pulse equalization (use parameter values specified by your telco).	cablelength long dbgain-value dbloss-value
Step 3 Set the framing to match your telco's offering, which in most cases is esf.	framing esf
Step 4 Set the line code type to match your telco's offering, which in most cases is `b8zs.`	linecode b8zs
Step 5 Configure one T1 line to serve as the primary or most stable clock source line.	clock source line primary ¹
Step 6 Configure channels on this T1 controller for ISDN PRI. or If you are not running ISDN, configure channels to accept voice calls. or If you are not running ISDN, configure channels for synchronous serial communications. This step creates interfaces that you can configure.	pri-group [timeslots range] cas-group channel-number timeslots range type signal-type channel-group number [timeslots range]
Step 7 Set the facilities data link exchange standard for the CSU, as specified by your service provider.	fdl {att \| ansi}

¹ Configure the other T1 line as the secondary clock source with the clock source line secondary command.

Repeat Step 1 through Step 7 to configure T1 controller 1, making sure in Step 5 to select T1 controller 1's line as the secondary clock source. You do not have to configure the timeslots in the same way on the two T1 controllers. You can configure the timeslots on this second controller as needed, no matter how you configured the timeslots in T1 controller 0.

Configure the ISDN D-Channel Serial Interfaces

Once you create the interfaces, two corresponding D-channel serial interfaces are automatically created. Serial interface 0:23 is the D channel for T1 controller 0, and serial interface 1:23 is the D channel for T1 controller 1. You must configure each serial interface to receive and make calls.

To configure an ISDN D-channel serial interface, perform the following steps beginning in global configuration mode:

Task	Command
Step 1 Specify the D channel of the first PRI line.	interface serial 0:23
Step 2 Configure all incoming voice calls to go to the Cisco AS5200's integrated modems.	isdn incoming-voice modem ¹^, ²
Step 3 Assign this interface to a dialer interface. The dialer interface's protocol characteristics apply to each interface assigned to it.	dialer rotary-group number ³

¹ Because some telcos charge more for ISDN data calls, you might want to configure the isdn incoming-voice isdn command to process ISDN calls as voice calls, which provides you with data service at a voice billing rate.
² Native ISDN calls are directed like a protocol.
³ The address you will assign to the dialer interface is used for the hunt group provided by the phone company.

Repeat Step 1 through Step 3 for serial interface 1:23, which is the D channel on the second T1 controller.

Configuration Examples

This section provides sample configurations for the Cisco AS5200's T1 controllers. You can configure the 24 channels of a channelized T1 to support ISDN PRI, robbed bit signaling, channel grouping, or a combination of all three. It provides the following sections:

Allocating All Channels for ISDN PRI

The following example shows you how to configure all 24 channels to support ISDN PRI on a Cisco AS5200:

AS5200(config)# controller T1 0
AS5200(config-controller)# pri-group timeslots 1-24
AS5200(config-controller)#
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:0, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:1, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:2, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:3, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:4, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:5, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:6, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:7, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:8, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:9, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:10, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:11, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:12, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:13, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:14, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:15, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:16, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:17, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:18, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:19, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:20, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:21, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:22, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:23, changed state to up
%LINK-3-UPDOWN: Interface Serial1:23, changed state to up

Allocating All Channels for Robbed Bit Signaling

The following example shows you how to configure all 24 channels to support robbed bit signaling feature group b on a Cisco AS5200:

AS5200(config)# controller T1 0
AS5200(config-controller)# cas-group 1 timeslots 1-24 type e&m-fgb
AS5200(config-controller)#
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 1 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 2 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 3 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 4 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 5 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 6 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 7 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 8 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 9 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 10 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 11 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 12 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 13 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 14 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 15 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 16 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 17 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 18 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 19 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 20 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 21 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 22 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 23 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 24 is up

Allocating All Channels to Serve as One Channel Group

The following example shows you how to configure all 24 channels as one channel group on a Cisco AS5200:

AS5200(config)# controller T1 0
AS5200(config-controller)# channel-group 1 timeslots 1-24
AS5200(config-controller)#
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:1, changed state to down
%LINK-3-UPDOWN: Interface Serial1:1, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:1, changed state to up

Mixing and Matching Channels

The following example shows you how to configure all 24 channels to support a combination of ISDN PRI, robbed bit signaling, and channel grouping. The range of timeslots that you allocate must match the timeslot allocations that your central office chooses to use. This is a rare configuration due to the complexity of aligning the correct range of timeslots on both ends of the connection.

The following configuration creates serial interfaces 0 to 9, which correspond to ISDN PRI timeslots 1 to 10 (shown as serial 1:0 through serial 1:9). The serial line 1:23 is the D channel, which carries the analog signal bits that dial a modem's phone number and determine if a modem is busy or available. The D channel is automatically created and assigned to timeslot 24.

AS5200(config)# controller T1 0
AS5200(config-controller)# pri-group timeslots 1-10
AS5200(config-controller)#
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:0, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:1, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:2, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:3, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:4, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:5, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:6, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:7, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:8, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:9, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:23, changed state to up
%LINK-3-UPDOWN: Interface Serial1:23, changed state to up

Channelized T1 data is transmitted over timeslots 11 through 16, which are assigned to serial interface 1 and virtual channel group 11 (shown as serial 1:11) in the next configuration example. However, notice how the earlier attempt to configure channel group 1 is denied because timeslot 1 is used by the previous ISDN PRI group configuration:

AS5200(config-controller)# channel-group 1 timeslots 11-16
%Channel-group 1 is already an isdn channel
AS5200(config-controller)# channel-group 11 timeslots 11-16
AS5200(config-controller)#
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:11, changed state to down
AS5200(config-controller)#
%LINK-3-UPDOWN: Interface Serial1:11, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1:11, changed state to up

The channel associated signal ear and mouth feature group b is configured on virtual signal group 17 for the remaining 17 to 23 timeslots, which are used for incoming and outgoing analog calls. There is no specific interface, such as the serial interface show in the earlier examples, that corresponds to the timeslot range. Notice how channel number 12 cannot be used to configure these timeslots, because it is used in the previously configured channel group range, which is timeslots 11 to 16.

AS5200(config-controller)# cas-group 12 timeslots 17-23 type e&m-fgb
The channel has been assigned to pri or channel-group
AS5200(config-controller)# cas-group 17 timeslots 17-23 type e&m-fgb
AS5200(config-controller)#

Command Reference

This section provides command reference documentation for the cas-group command, which has been modified to support additional types of robbed bit signaling.

Additional commands used with this feature are documented in the Cisco IOS Release 11.2 Configuration Fundamentals Command Reference.

cas-group

To configure channelized T1 timeslots with channel associated signaling (also known as robbed bit signaling), which enables a Cisco AS5200 modem to receive and transmit analog calls, use the cas-group controller configuration command. Use the no form of this command to disable channel associated signaling for one or more timeslots.

cas-group channel-number timeslots range type signal-type
no cas-group channel-number timeslots range type signal-type

Syntax Description

channel-number

Specifies a single channel group number, which can be between 0 and 23.

timeslots range

(Optional) Specifies a timeslot range of values from 1 to 24.

type signal-type

Specifies the type of channel associated signaling. Choose one of the following signal types to configure:

· e&m-fgb--Specifies ear and mouth channel signaling with feature group b support.

· e&m-fgd--Specifies ear and mouth channel signaling with feature group d support.

· fxs-loopstart-- Specifies foreign exchange system loopstart signaling support.

· fxs-groundstart--Specifies foreign exchange system ground start signaling support.

· sas-loopstart--Specifies specific access station loopstart signaling support.

· sas-groundstart--Specifies specific access station ground start signaling support.

Default

No channelized T1 robbed bit signaling is configured.

Command Mode

Controller configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

Use this command to enable a Cisco AS5200 modem to receive and transmit incoming and outgoing call signaling (such as on-hook and off-hook) through each T1 controller that is configured for a channelized T1 line.

Switched 56 digital calls are not supported in this feature.

Example

The following example configures all 24 channels with ear and mouth channel signaling with feature group b support on a Cisco AS5200:

AS5200(config)# controller T1 0
AS5200(config-controller)# cas-group 1 timeslots 1-24 type e&m-fgb
AS5200(config-controller)#
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 1 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 2 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 3 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 4 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 5 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 6 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 7 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 8 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 9 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 10 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 11 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 12 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 13 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 14 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 15 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 16 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 17 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 18 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 19 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 20 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 21 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 22 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 23 is up
%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 24 is up

What to Do Next

Refer to the Cisco AS5200 Universal Access Server Software Configuration Guide for complete information on configuring additional aspects of the access server.

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