Cisco IGX 8400 Series Voice Service

Signaling allows a phone or other device to communicate with the network and destination device in order to set up and tear down a call and provide other necessary functions.

Signaling techniques are categorized as either supervision, addressing, or alerting. A call cannot take place without all of these signaling techniques.

Supervision signaling involves detecting changes to the status of a loop or trunk and, in response, generating a predetermined response such as closing a circuit (loop) to connect a call.
Addressing signaling involves passing dialed digits to a private branch exchange (PBX), central office (CO), or other switching device, which then sets up a path between calling and called party.
Alerting signaling provides audible tones such as dial tone, ringing, number dialing, busy signal, and off-hook notification to the user.

Signaling can be in-band (carried on the same circuit as the data path) or, more commonly now, out-of-band (carried on a separate circuit).

Switching

Switching involves connecting a calling party or device to a called party or device. A switch examines incoming data, determines their destination, and sets up a transmission path through its switching matrix to connect the incoming port to the appropriate outgoing port.

Voice Connections Supported on the IGX

For further information on the following topics, proceed as follows:

Connections supported on the IGX, see Table 7-1
Signaling on the CVM, see the "Signaling on the CVM" section
Signaling on the URM, see the "Signaling on the URM" section
Signaling on the UVM, see the "Signaling on the UVM" section

Table 7-1 Voice Connections Supported on the IGX

Origin Endpoint	Destination Endpoint	Connection Type
CVM	CVM	Voice, data, voice+data
	HDM (IGX)	Data
	UVM	Voice, data, voice+data
URM	UFM	VoFR
	URM	Voice+data (CBR, VBRrt, VBRnt), VoFR, VoATM, data (ABR, UBR, FST)
	UXM	Voice+data (CBR, VBRrt, VBRnt), data (ABR, UBR, FST)
UVM	CVM	Voice, data, voice+data Note The CVM cannot terminate connections using LDCELP or CSACELP compression
	HDM (IGX)	Data
	UVM	Voice, data, voice+data

Signaling on the UVM

The UVM provides toll-quality voice and efficiently utilizes wide-area bandwidth for enterprise and service-provider voice applications. Bandwidth savings achieved through voice compression and silence suppression can be applied to bursty traffic and a higher number of voice channels per trunk. It supports channelized T1, E1, or J1 lines for carrying voice, data, or both types of traffic.

You can configure voice-channel signaling of any of the following types on the UVM:

Robbed-bit signaling (either D4 or ESF frame format)—For T1 lines
Channel-associated signaling (CAS)—For E1 or J1 lines
Transparent CCS (ISDN & DPNSS)—For all lines
E&M-to-DC5A and DC5A-to-E&M conversion—For international applications

The UVM supports both CAS and CSS signaling. However, CSS (such as DPNSS and ISDN signaling) is supported through a clear (transparent) channel. See Table 7-2 for signaling formats supported on the UVM.

Table 7-2 Signaling Formats Supported on the UVM

Line Type	Line Framing	Signaling Format	Signaling Bit
T1	D4	CSS	—
T1	ESF	CSS	—
T1	ESF	CAS	ABAB
T1	ESF	CAS	ABCD
T1	D4	CAS	AB
E1or Y1	—	CAS	ABCD
E1or Y1	—	CSS	—

The UVM extracts information from the CAS signaling bits in the T1, E1, or J1 frame. When a signaling bit changes state, the UVM sends signaling packets to the card at the other end of the connection. The UVM can set, invert, and clear AB or ABAB bits (T1 lines) or ABCD bits (E1 or Y1 lines) to allow for some types of signaling conversion.

Tip To see the signaling configuration, enter the switch software dsplncnf command. To configure the line's signaling, enter the switch software cnfln command.

Tip On CCS, E1 or J1 lines, configure channel 16 as a t-type or td-type connection.

Signaling bits are forced to a predetermined state when a transmission link fails, in order to drop calls in progress and block new access to the voice circuits. Usually, the predetermined state is "idle then busy," (idle for a short interval to drop all calls in progress followed by permanent busy until the fault clears) but other conditioning sequences are allowed.

Tip To condition voice-frequency (VF) signaling—that is, to specify the channel on-hook (idle) state and the signaling state forced by the CVM or UVM when a connection fails—enter the switch software cnfcond and cnfvchtp commands. From the options under the cnfvchtp command, select one of the voice interface types from the screen. If a connection fails, channel voice and signaling conditions are instantaneously applied.

D-Channel Compression on the UVM

D-channel compression reduces the bandwidth consumed by a CCS signaling channel by eliminating idle patterns from the data stream. This may reduce the consumed bandwidth by as much as 75 percent.

Tip To enable D-channel compression, add the signaling connection through Cisco WAN Manager or enter the switch software addcon command, and specify the connection type as "td." The maximum number of td connections on a UVM is 32.

Signaling on the CVM

The CVM extracts signaling information from the signaling bits in an E1, T1, or J1 frame. When a signaling bit changes state, the CVM or UVM generates signaling packets for the CVM at the other end of the connection.

You can configure voice-channel signaling of any of the following types on the CVM:

Robbed-bit signaling (either D4 or ESF frame format) for T1 lines
Channel-associated signaling (CAS) for E1 or J1 lines
Transparent CCS (ISDN & DPNSS) for all lines
E&M-to-DC5A and DC5A-to-E&M conversion for international applications

The CVM supports both CAS and CSS signaling. However, CSS (such as DPNSS and ISDN signaling) is supported through a clear (transparent) channel. See Table 7-2 for signaling formats supported on the UVM.

Table 7-3 Signaling Formats Supported on the CVM

Line Type	Line Framing	Signaling Format	Signaling Bit
T1	ESF	CAS	ABAB
T1	ESF	CAS	ABCD
T1	D4	CAS	AB
T1	-	CSS	-
E1	-	CAS	ABCD
E1	-	CSS	-

Tip For CSS on an E1 line, configure channel 16 as a t-type connection to carry the signaling.

The CVM extracts CAS signaling information from the signaling bits in the E1 or T1 frame. When a signaling bit changes state, the CVM generates signaling packets to the CVM or UVM at the other end of the connection. You can select any one of many voice-interface types, such as 2-W E&M, FXO/FXS, or DPO/DPS, from a template to condition the VF signaling. You can also specify customized signal conditioning.

Signaling on the URM

The URM offers a full suite of IP services, including VoIP, and end-to-end operability with any Cisco IOS-based platform. It extracts information from the CAS signaling bits in the T1 or E1 frame. When a signaling bit changes state, the URM sends signaling packets to the card at the other end of the connection. CSS signaling, such as DPNSS and ISDN signaling, are supported through a clear (transparent) channel.

You can configure voice channel signaling of any of the following types on the URM:

CAS: telephony interface signaling T1 CAS, transparent CAS signaling
CCS: Q.Sig T1/E1, Q.921, ISDN PRI (user side), CCS-DPNSS, transparent (IP and ATM)

Idle-Code Suppression

Idle-code suppression (ICS) detects the idle (on-hook) state of a video call, which uses an nx64 kbps data connection, and suppresses packet transmission during an idle condition. The UVM or CVM identifies the idle condition by detecting the repetition of idle codes. IGX switch software enables or disables the ICS feature dynamically.

Tip To enable ICS on a data channel, enter the switch software cnfdch command.

Channel Pass-Through

Channel pass-through allows two locally-connected voice card sets to support the maximum number of channels on a T1, E1, or J1 line.

For example, only 16 channels can use G.728 (LDCELP) or G.729 CSACELP compression, but the total number of channels allowable on a line may be greater than 16. With channel pass-through, the remaining channels available on the line are passed from the first (or primary) voice card set to the secondary card set for processing.

Channel pass-through is not necessary for G.729A CSACELP, and does not apply to channels that use PCM, or ADPCM.

Tip To enable channel pass-through on a line, enter the switch software cnflnpass command.

Time-Division Multiplexing Transport

Time-division multiplexing (TDM) transport is only supported on Model C CVM cards.

TDM transport allows you to bundle time slots to form a single, transparent connection through the network. TDM transport supports the following features:

Bundling of 1-31 time slots for rates ranging from 64 kbps to 1984 kbps
8/8 line coding
Preservation of time slot alignment within frames
Supports data channel bundling only

Voice Service Provisioning

This section provides information on how to provision voice services on an IGX node. Information in this section applies to the UVM and CVM. For information on how to provision voice services using the URM card, refer to Cisco IOS documentation supporting your Cisco IOS release (also see the "Accessing User Documentation" section).

For more information on the UVM, CVM, and URM card sets, see the "Universal Voice Module" section, the "Channelized Voice Module" section, and the "Universal Router Module" section.

When provisioning voice service, you will complete the following tasks:

1. Configure and activate the line (see the "IGX Line Configuration" section).

2. (optional—UVM only) Configure channel pass-through (see the "Channel Pass-Through" section).Configure channel parameters for the voice connection (see the "Setting Up a Voice Connection" section).

3. Add the voice connection to the line.

a. Configure voice channel parameters using the switch software commands outlined in Table 7-4.

Setting Up a Voice Connection

Before setting up a voice connection, you must configure the node, trunks, and the line to be used for the voice connection. For information on configuring the node, see "Cisco IGX 8400 Series Nodes" For information on configuring a trunk, see "Cisco IGX 8400 Series Trunks" For information on configuring the line, see "Cisco IGX 8400 Series Lines"

To set up a voice connection, use the following procedure:

Step 1 Add the voice connection to the line with the switch software addcon command.

Step 2 Configure the dial-type for the channel with the switch software cnfchdl command.

Step 3 Configure the echo canceller for the channel with the switch software cnfchec command.

Step 4 Configure the amount of gain inserted in a voice channel with the switch software cnfchgn command.

Step 5 (Optional) Develop or adapt conditioning templates and voice interface types to configure signaling types to be used by the channel with the switch software cnfcond and cnfvchtp commands.

Step 6 (Optional) Configure the receive and transmit signaling for the voice channel with the switch software cnfrcvsig and cnfxmtsig commands.

Step 7 (Optional) Configure channel utilization with the switch software cnfchutl command.

Switch Software Commands Related to Voice Service

Full command descriptions for the switch software commands listed in Table 7-4 can be accessed at one of the following links:

For commands addad through cpytrkict, see "Alphabetical List of Commands addad through cpytrkict" in the Cisco WAN Switching Command Reference.
For commands dchst through window, see "Alphabetical List of Commands dchst through window" in the Cisco WAN Switching Command Reference.

Table 7-4 Switch Software Commands Related to Voice Service

Command	Description
cnflnpass	(Applies to UVM using LDCELP or CACELP per G.729) Configures the UVM for channel pass-through.
cnfchdl	Configures a channel's dial type. Options are inband, pulse, and user-configured.
cnfchec	Configures the echo canceller for the channel—enables or disables the echo canceller for a range of voice channels and configures other echo canceller functions.
cnfchgn	Configures the amount of gain inserted in a voice channel.
cnfchutl	Configures channel utilization for the channel.
cnfcond	Configures a conditioning template for the channel.
cnfln	Configures the line.
cnfrcvsig	Configures receive signaling for the channel.
cnfuvmchparm	(UVM only) Configures channel parameters.
cnfvchparm	Configures voice channel parameters.
cnfvchtp	Configures a voice interface type for the channel.
cnfxmtsig	Configures transmit signaling for the channel.
dspchan	Displays data structures defining a voice channel.
dsplncnf, dspln	Displays the current line configuration.
dspsig	Displays the current signaling state received at the local node from a voice channel.
dsputl	Displays the utilization factors for all voice connections on the line.
dnln	Deactivates (downs) the line.
upln	Activates (ups) the line.

Where to Go Next

For information on IGX ATM service, refer to Chapter 8, "Cisco IGX 8400 Series ATM Service"

For installation and basic configuration information, see the Cisco IGX 8400 Series Installation Guide, Chapter 1, "Cisco IGX 8400 Series Product Overview"

For more information on switch software commands, refer to the Cisco WAN Switching Command Reference, Chapter 1, "Command Line Fundamentals ."

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