Cisco Voice over IP (CVOICE)

Voice over Internet Protocol (VoIP) allows a voice-enabled router to carry voice traffic, such as telephone calls and faxes, over an Internet Protocol (IP) network. This topic introduces the fundamentals of VoIP, the various types of voice gateways, and how to use gateways in different IP telephony environments. Voice over IP is also known as […]

VoIP Fundamentals (Introducing Voice over IP Networks) Part 2

PRI/BRI Backhaul A Primary Rate Interface (PRI) and Basic Rate Interface (BRI) backhaul is an internal interface between the call agent (such as Cisco UCM) and Cisco gateways. It is a separate channel for backhauling signaling information. A PRI backhaul forwards PRI Layer 3 (Q.931) signaling information via a TCP connection. An MGCP gateway is […]

Introducing VoIP Gateways (Introducing Voice over IP Networks) Part 1

Gateways provide a number of ways to connect an IP telephony network to the PSTN, a legacy PBX, key systems, or other TDM systems. Gateways range from specialized, entry-level, and standalone voice gateways to high-end, integrated routers and Cisco IOS gateways. This section introduces voice gateways and deployment models in an IP telephony network. Understanding […]

Introducing VoIP Gateways (Introducing Voice over IP Networks) Part 2

Well-Known and Widely Used Enterprise Models Several Cisco modular access routers that might already be installed in enterprise networks have voice gateway capabilities. Although some of these models are well known and widely used, they have reached end of sale (EOS) status. However, because these routers were the leading voice gateway products for a long […]

Introducing VoIP Gateways (Introducing Voice over IP Networks) Part 3

Cisco AS5850 Universal Gateway The Cisco AS5850 Universal Gateway, as illustrated in Figure 1-21, is a high-density, carrier-class gateway with high capacity and availability. The AS5850 Universal Gateway is specifically designed to meet the demands of large service providers by supporting up to five channelized T3s (CT3s), 96 T1s, or 86 E1s of data, voice, […]

Introducing VoIP Gateways (Introducing Voice over IP Networks) Part 5

Design Guidelines for Multisite WAN with Centralized Call-Processing Deployment Follow these guidelines when implementing the multisite WAN model with centralized call processing: ■ Minimize delay between Cisco UCM and remote locations to reduce voice cut-through delays (also known as clipping). The ITU-T G.114 recommendation specifies a 150 ms maximum one way. ■ Use HSRP for […]

VoIP Fundamentals (Considering VoIP Design Elements) Part 1

Voice over IP (VoIP) introduces additional challenges into a network design. Some of these challenges stem from the necessity of providing a perceptible level of voice quality to end users, while efficiently using available bandwidth. VoIP design also requires additional processing components not necessary in traditional data networks. Specifically, coder/decoders (that is, codecs) convert the […]

VoIP Fundamentals (Considering VoIP Design Elements) Part 2

Audio Quality Measurement Several methods can be used to determine signal quality, including the following: ■ Mean Opinion Score (MOS) ■ Perceptual Speech Quality Measurement (PSQM) ■ Perceptual Evaluation of Speech Quality (PESQ) MOS MOS is a scoring system for voice quality. A MOS score is generated when listeners evaluate prerecorded sentences that are subject […]

VoIP Fundamentals (Considering VoIP Design Elements) Part 3

Understanding Fax/Modem Pass-Through, Relay, and Store and Forward Several features are available to overcome the issues involved with carrying fax and modem signals across an IP network including ■ Fax and Modem Pass-Through ■ Fax and Modem Relay ■ Fax Store and Forward Fax Pass-Through Fax pass-through, as illustrated in Figure 2-6, is the simplest […]

VoIP Fundamentals (Considering VoIP Design Elements) Part 4

Payload Redundancy You can enable payload redundancy so the modem pass-through over VoIP switchover causes the gateway to send redundant packets. 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. When […]