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The Cisco IOS Multiservice Applications Configuration Guide shows you how to configure your Cisco router or access server to support voice, video, and broadband transmission.
The Cisco IOS Multiservice Applications Configuration Guide document is divided into three parts:
Each part contains one or more chapters that describe configuration procedures for each respective technology. The following sections describe the chapter contents for each part of this configuration guide.
Cisco offers the following implementations of voice technology, depending on the particular Cisco device you are using:
The key to understanding the Cisco voice implementation is to understand the use of dial peers. Dial peers describe the entities to or from which a call is established. All voice technologies use dial peers to define the characteristics associated with a call leg. A call leg is a discrete segment of a call connection that lies between two points in the connection. Four call legs comprise an end-to-end call, two from the perspective of the source route, and two from the perspective of the destination route. You use dial peers to apply specific attributes to call legs and to identify call origin and destination. Attributes applied to a call leg include specific quality of service (QoS) features (such as IP RTP Priority and IP Precedence), compression/decompression (codec), voice activity detection (VAD), and fax rate.
There are basically two different kinds of dial peers with each voice implementation:
Other applications (like store and forward fax, which uses the infrastructure of VoIP but is not strictly a voice technology) also use dial peers to assign attributes to call legs.
Voice port commands define the characteristics associated with a particular voice-port signalling type. The Cisco implementation of voice supports both analog and digital telephony connections. The connection supported (and the associated signalling) depends on the type of voice network module (VNM) or voice feature card (VFC) installed in your Cisco router or access server.
Voice ports provide support for three basic analog voice signalling formats:
Depending on the Cisco device you are configuring, the following digital signalling is supported:
The voice port syntax depends on the hardware platform on which it is being configured.
Cisco IOS Release 12.1 offers the following voice and voice-related technologies:
VoIP enables Cisco routers and access servers to carry voice traffic (for example, telephone calls and faxes) over an IP network. In VoIP, the digital signal processor (DSP) segments the voice signal into frames that are then coupled in groups of two and stored in voice packets. These voice packets are transported using IP in compliance with ITU-T specification H.323. Because VoIP is a delay-sensitive application, you need to have a well-engineered network end-to-end to successfully use VoIP. Fine-tuning your network to adequately support VoIP involves a series of protocols and features geared toward QoS. Traffic shaping considerations must be taken into account to ensure the reliability of the voice connection.
VoFR enables a Cisco device to carry voice traffic (for example, telephone calls and faxes) over a Frame Relay network. When voice traffic is sent over Frame Relay, the voice traffic is segmented and encapsulated for transit across the Frame Relay network. The segmentation engine uses FRF.12 fragmentation. FRF.12 (also known as FRF.11 Annex C) allows long data frames to be fragmented into smaller pieces and interleaved with real-time frames. In this way, real-time voice and nonreal-time data frames can be carried together on lower speed links without causing excessive delay to the real-time traffic.
The segmentation size configured must match the line rate, or the port access rate. To ensure a stable voice connection, you must configure the same data segmentation size on both sides of the voice connection. When voice segmentation is configured, all priority queueing, custom queueing, and weighted fair queueing is disabled on the interface.
When you configure voice and data traffic over the same Frame Relay DLCI, you must take traffic shaping considerations into account to ensure the reliability of the voice connection.
Cisco VoFR implementation supports the following types of VoFR calls:
VoATM enables a Cisco MC3810 multiservice concentrator to carry voice traffic (for example, telephone calls and faxes) over an ATM network. The Cisco MC3810 multiservice concentrator supports compressed VoATM on ATM port 0 only.
When voice traffic is sent over ATM, the voice traffic is encapsulated using a special AAL5 encapsulation for multiplexed voice. The ATM permanent virtual circuit (PVC) must be configured to support real-time voice traffic, and the AAL5 voice encapsulation must be assigned to the PVC. The PVC must also be configured to support variable bit rate (VBR) for real-time networks for traffic shaping between voice and data PVCs.
Traffic shaping is necessary so that the carrier does not discard the incoming calls from the MC3810. To configure voice and data traffic shaping, you must configure the peak, average, and burst options for voice traffic. Configure the burst value if the PVC will be carrying bursty traffic. The peak, average, and burst values are needed so the PVC can effectively handle the bandwidth for the expected number of voice calls.
VoHDLC enables a Cisco MC3810 multiservice concentrator to carry live voice traffic (for example, telephone calls and faxes) back-to-back to a second Cisco MC3810 multiservice concentrator. VoHDLC on the Cisco MC3810 multiservice concentrator is supported on serial ports 0 or 1, or on 0:x (the T1/E1 trunk, where x represents the channel group number). VoHDLC traffic is carried over a serial line. As a result, configuration is simpler than for VoIP, VoFR, or VoATM.
The Multimedia Conference Manager provides both gatekeeper and proxy capabilities, which are required for service provisioning and management of H.323 networks. With Multimedia Conference Manager you can configure your current internetwork to route bit-intensive data such as audio, telephony, video and audio telephony, and data conferencing using existing telephone and ISDN links, without degrading the current level of service in the network. In addition, you can implement H.323-compliant applications on existing networks in an incremental fashion without upgrades.
With Multimedia Conference Manager, you can provide the following services:
The Store and Forward Fax feature enables Cisco AS5300 access servers to send and receive faxes across packet-based networks. This feature is an implementation of the RFC 2305 proposed standard from the Internet Engineering Task Force (IETF), which is the same as the T.37 recommendation from the ITU. With Store and Forward Fax, your access server becomes a multiservice platform, supplying both data and fax communication. Because Store and Forward Fax uses the infrastructure of VoIP, it has been included in the Cisco IOS Multiservice Applications Configuration Guide as a voice-related technology.
Store and Forward Fax functionality is facilitated through the Simple Mail Transfer Protocol (SMTP). Additional functionality is provided to confirm delivery using existing SMTP mechanisms, such as Extended Simple Mail Transfer Protocol (ESMTP), for those features.
Cisco supports video traffic within a data stream in three ways:
Cisco offers broadband Internet or intranet access and packet telephone services through a shared two-way cable system and IP backbone network. At the cable service provider side of the network, Cisco provides the Cisco uBR7200 series universal broadband routers. Cisco uBR7200 series universal broadband routers are Data-over-Cable Service Interface Specifications (DOCSIS)-based cable modem termination systems (CMTSs) that serve as interfaces between a WAN backbone and a hybrid fiber-coaxial (HFC) cable network. The Cisco uBR7200 series cable routers support both two-way and telephone return cable modems on a single downstream channel. As many as six upstream channels are supported on a single cable modem card, and as many as five cable modem cards can be installed in a single Cisco uBR7200 series chassis.
At the subscriber end of the network, Cisco provides the DOCSIS-based Cisco uBR900 series cable access routers. Cisco uBR900 series cable access routers provide the residential or small office, home office (SOHO) subscriber with high-speed Internet or intranet access with data and VoIP services over the HFC network.
Posted: Thu Jul 27 00:07:19 PDT 2000
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