Table Of Contents
SIP-to-SIP Extended Feature Functionality for Session Border Controllers
Prerequisites for SIP-to-SIP Extended Feature Functionality for Session Border Controllers
SIP-to-SIP Extended Feature Functionality for Session Border Controllers
The SIP-to-SIP Extended Feature Functionality for Session Border Controllers enables SIP-to-SIP functionality to conform with RFC 3261 to interoperate with SIP user agents (UAs). The SIP-to-SIP Extended Feature Functionality includes:
•Call Admission Control (based on CPU, memory, and total calls)
•Delayed Media Call
•ENUM support
•Configuring SIP Error Message Pass-Through
•Interoperability with Cisco Unified Communications Manager 5.0 and BroadSoft
•Lawful Intercept
•Media Inactivity
•TCP and UDP interworking
•Tcl scripts with SIP NOTIFY VoiceXML with SIP-to-SIP
•Transport Layer Security (TLS)
Prerequisites for SIP-to-SIP Extended Feature Functionality for Session Border Controllers
Cisco Unified Border Element
•Cisco IOS Release 12.4(6)T or a later release must be installed and running on your Cisco Unified Border Element.
Cisco Unified Border Element (Enterprise)
•Cisco IOS XE Release 3.1S or a later release must be installed and running on your Cisco ASR 1000 Series Router.
Modem Pass-through over VoIP
This feature module describes the Modem Passthrough over Voice over IP (VoIP) feature on Cisco Unified Border Element and Cisco Unified Border Element (Enterprise) and includes information in the following sections:
•Information about Modem Passthrough over VoIP
•Restrictions for the Modem Passthrough over VoIP Feature
•Prerequisites for the Modem Passthrough over VoIP Feature
•How to Configure Modem Passthrough over VoIP
•Monitoring and Maintaining Modem Passthrough over VoIP
Information about Modem Passthrough over VoIP
The Modem Passthrough over VoIP feature provides the transport of modem signals through a packet network by using pulse code modulation (PCM) encoded packets.
The Modem Passthrough over VoIP feature performs the following functions:
•Represses processing functions like compression, echo cancellation, high-pass filter, and voice activity detection (VAD).
•Issues redundant packets to protect against random packet drops.
•Provides static jitter buffers of 200 milliseconds to protect against clock skew.
•Discriminates modem signals from voice and fax signals, indicating the detection of the modem signal across the connection, and placing the connection in a state that transports the signal across the network with the least amount of distortion.
•Reliably maintains a modem connection across the packet network for a long duration under normal network conditions.
For further details, the functions of the Modem Passthrough over VoIP feature are described in the following sections.
Modem Tone Detection
The gateway is able to detect modems at speeds up to V.90.
Passthrough Switchover
When the gateway detects a data modem, both the originating gateway and the terminating gateway roll over to G.711. The roll over to G.711 disables the high-pass filter, disables echo cancellation, and disables VAD. At the end of the modem call, the voice ports revert to the prior configuration and the digital signal processor (DSP) goes back to the state before switchover. You can configure the codec by selecting the g711alaw or g711ulaw option of the codec command.
See also the "How to Configure Modem Passthrough over VoIP" section in this document.
Controlled Redundancy
You can enable payload redundancy so that the Modem Passthrough over VoIP switchover causes the gateway to emit redundant packets.
Packet Size
When redundancy is enabled, 10-ms sample-sized packets are sent. When redundancy is disabled, 20-ms sample-sized packets are sent.
Clock Slip Buffer Management
When the gateway detects a data modem, both the originating gateway and the terminating gateway switch from dynamic jitter buffers to static jitter buffers of 200-ms depth. The switch from dynamic to static is to compensate for Public Switched Telephone Network (PSTN) clocking differences at the originating gateway and the terminating gateway. At the conclusion of the modem call, the voice ports revert to dynamic jitter buffers.
Figure 1 illustrates the connection from the client modem to a MICA technologies modem network access server (NAS).
Figure 1 Modem Passthrough Connection
Prerequisites for the Modem Passthrough over VoIP Feature
•VoIP enabled network.
•Cisco IOS Release 12.1(3)T must run on the gateways for the Modem Passthrough over VoIP feature to work.
•Network suitability to pass modem traffic. The key attributes are packet loss, delay, and jitter. These characteristics of the network can be determined by using the Cisco IOS feature Service Assurance Agent.
Cisco Unified Border Element
•Cisco IOS Release 12.4(6)T or a later release must be installed and running on your Cisco Unified Border Element.
Cisco Unified Border Element (Enterprise)
•Cisco IOS XE Release 3.3S or a later release must be installed and running on your Cisco ASR 1000 Series Router.
Restrictions for the Modem Passthrough over VoIP Feature
Cisco Unified Border Element (Enterprise)
•If call started as g729, upon modem tone (2100Hz) detection both the outgoing gateway (OGW) and the trunking gateway (TGW) will genearate NSE packets towards peer side and up speed to g711 as Cisco UBE(Enterprise) passes these packets to the peer side.
Note That OGW and TGW display the new codec, but the Cisco UBE (Enterprise) continues to show the original codec g729 in the show commands.
How to Configure Modem Passthrough over VoIP
By default, modem passthrough over VoIP capability and redundancy are disabled.
Tips You need to configure modem passthrough in both the originating gateway and the terminating gateway for the Modem Passthrough over VoIP feature to operate. If you configure only one of the gateways in a pair, the modem call will not connect successfully.
Redundancy can be enabled in one or both of the gateways. When only a single gateway is configured for redundancy, the other gateway receives the packets correctly, but does not produce redundant packets.
See the following sections for the Modem Passthrough over VoIP feature. The two configuration tasks can configure separately or together. If both are configured, the dial-peer configuration takes precedence over the global configuration. Consequently, a call matching a particular dial-peer will first try to apply the modem passthrough configuration on the dial-peer. Then, if a specific dial-peer is not configured, the router will use the global configuration:
•Configuring Modem Passthrough over VoIP Globally
•Configuring Modem Passthrough over VoIP for a Specific Dial Peer
Configuring Modem Passthrough over VoIP Globally
For the Modem Passthrough over VoIP feature to operate, you need to configure modem passthrough in both the originating gateway and the terminating gateway so that the modem call matches a voip dial-peer on the gateway.
When using the voice service voip and modem passthrough nse commands on a terminating gateway to globally set up fax or modem passthrough with NSEs, you must also ensure that each incoming call will be associated with a VoIP dial peer to retrieve the global fax or modem configuration. You associate calls with dial peers by using the incoming called-number command to specify a sequence of digits that incoming calls can match.
To configure the Modem Passthrough over VoIP feature for all the connections of a gateway, use the following commands beginning in global configuration mode:
SUMMARY STEPS
1. enable
1. voice service voip
2. modem passthrough nse [payload-type number] codec {g711ulaw | g711alaw} [redundancy] [maximum-sessions value]
3. exit
4. exit
Detailed Steps
Configuring Modem Passthrough over VoIP for a Specific Dial Peer
You can configure the Modem Passthrough over VoIP feature on a specific dial peer in two ways, as follows:
•Globally in the voice-service configuration mode
•Individually in the dial-peer configuration mode on a specific dial peer
The default behavior for the voice-service configuration mode is no modem passthrough. This default behavior implies that modem passthrough is disabled for all dial peers on the gateway by default.
To enable Modem Passthrough on the VoIP dial peers on both the originating and terminating gateway, configure modem passthrough globally or explicitly on the dial peer.
For modem passthrough to operate, you must define VoIP dial peers on both gateways to match the call, for example, by using a destination pattern or an incoming called number. The modem passthrough parameters associated with those dial peers then will apply to the call.
Note When modem passthrough is configured individually for a specific dial peer, that configuration for the specific dial peer takes precedence over the global configuration.
To configure the Modem Passthrough over VoIP feature for a specific dial peer, use the following commands beginning in global configuration mode:
SUMMARY STEPS
1. enable
1. voice service voip
2. modem passthrough nse [payload-type number] codec {g711ulaw | g711alaw} [redundancy] [maximum-sessions value]
3. exit
4. exit
DETAILED STEPS
Verifying Modem Passthrough over VoIP
To verify that the Modem Passthrough over VoIP feature is enabled, perform the following steps:
Step 1 Enter the show run command to verify the configuration.
Step 2 Enter the show dial-peer voice command to verify that Modem Passthrough over VoIP is enabled.
Troubleshooting Tips
To troubleshoot the Modem Passthrough over VoIP feature, perform the following steps:
•Make sure that you can make a voice call.
•Make sure that Modem Passthrough over VoIP is configured on both the originating gateway and the terminating gateway.
•Make sure that both the originating gateway and the terminating gateway have the same named signaling event (NSE) payload-type number.
•Make sure that both the originating gateway and the terminating gateway have the same maximum-sessions value when the two gateways are configured in the voice-service configuration mode.
•Use the debug vtsp dsp and debug vtsp session commands to debug a problem.
Monitoring and Maintaining Modem Passthrough over VoIP
To monitor and maintain the Modem Passthrough over VoIP feature, use the following commands in privileged EXEC mode:
Configuration ExamplesThe following is sample configuration for the Modem Passthrough over VoIP feature:
version 12.1service timestamps debug uptimeservice timestamps log uptimeno service password-encryption!voice service voipmodem passthrough nse codec g711ulaw redundancy maximum-session 5!!resource-pool disable!!!!!ip subnet-zeroip ftp source-interface Ethernet0ip ftp username labip ftp password labno ip domain-lookup!isdn switch-type primary-5esscns event-service server!!!!!mta receive maximum-recipients 0!!controller T1 0framing esfclock source line primarylinecode b8zspri-group timeslots 1-24!controller T1 1shutdownclock source line secondary 1!controller T1 2shutdown!controller T1 3shutdown!!!interface Ethernet0ip address 1.1.2.2 255.0.0.0no ip route-cacheno ip mroute-cache!interface Serial0:23no ip addressencapsulation pppip mroute-cacheno logging event link-statusisdn switch-type primary-5essisdn incoming-voice modemno peer default ip addressno fair-queueno cdp enableno ppp lcp fast-start!interface FastEthernet0ip address 26.0.0.1 255.0.0.0no ip route-cacheno ip mroute-cacheload-interval 30duplex fullspeed autono cdp enable!ip classlessip route 17.18.0.0 255.255.0.0 1.1.1.1no ip http server!!!!voice-port 0:D!dial-peer voice 1 potsincoming called-number 55511..destination-pattern 020..direct-inward-dialport 0:Dprefix 020!dial-peer voice 2 voipincoming called-number 020..destination-pattern 55511..modem passthrough nse codec g711ulaw redundancysession target ipv4:26.0.0.2!!line con 0exec-timeout 0 0transport input noneline aux 0line vty 0 4login!!end