Introduction to IP Telephony

TECHBEE is one of the leading Cisco IP-Telephony Partner in Dubai. IP telephony refers to communication services such as phone, fax, and voice-messaging that are delivered over a packet-switched IP network rather than a circuit-switched PSTN.

KEY POINT

VoIP converts voice into IP packets and routes them to corresponding locations using voice-enabled routers. Users are typically unaware that VoIP has been implemented in the network; they continue to use their traditional phones, which are connected to a PBX. The PBX, on the other hand, is connected to a voice-enabled router that serves as an entrance point to VoIP rather than the PSTN or another PBX.

Traditional phones are replaced with IP phones, and PBXs are replaced with the Cisco Unified Communications Manager, a server for call control and signalling. Voice-to-IP conversion is handled by the IP phone itself, therefore voice-enabled routers aren’t required in the workplace network. If a link to the PSTN is necessary, a voice-enabled router or other gateway that forwards calls to the PSTN must be installed.

Converting an analogue speech signal into a digital format, then compressing and translating the digital signal into IP packets for transmission across an IP network, are the main processes in placing an IP telephone call. At the receiving end, the process is reversed.

The IP telephony architecture, includes four distinct components: infrastructure, call processing, applications, and client devices. These components are described as follows:

• Infrastructure: Data link layer and multilayer switches, as well as voice-enabled routers, are used to connect endpoints to the IP and PSTN networks. Switched 10/100 Ethernet ports connect endpoints to the network. Power over Ethernet (PoE) ports on switches detect the presence of IP devices that require inline power, such as Cisco IP phones and wireless access points, and supply it. Conversions between the circuit-switched PSTN and IP networks are performed by voice-enabled routers.
• Call processing: Cisco Unified Communications Manager is the Cisco enterprise IP telephony solution’s software-based call-processing component. Cisco Unified Communications Manager is an enterprise IP telephony call processing system that is scalable, distributable, and highly available. It acts similarly to a traditional telephone network’s PBX, including call setup and processing.

The Cisco Unified Communications Manager can be installed on Cisco MCS 7800 Series server platforms and selected third-party servers.

• Applications: Applications enhance the IP telephony infrastructure by adding new functionalities. Cisco Unity unified messaging (which combines e-mail and voice mail), Cisco Unified MeetingPlace (multimedia conferencing), Cisco Unified IP IVR, and Cisco Unified Contact Center products (which include intelligent contact routing, call treatment, network-to-desktop computer telephony integration, and multichannel automatic call distribution) are just a few of the Cisco IP telephony applications. Third-party organisations can create software that works with Cisco Unified Communications Manager thanks to the open-source application layer.
• Client devices are IP phones and software programmes that allow users to communicate over an IP network. The IP telephones are managed centrally by Cisco Unified Communications Manager via Ethernet connections in the Building Access Layer switches.

• Voice Messaging and Applications
• Call-Processing Engine
• Cisco Unifi Communications Manager
• Voice Messaging and Applications
• Call-Processing Engine
• Cisco Unifi Communications Manager
• PSTN Gateway or Router

• DSP Resources for Conferencing
• QoS-Enabled WAN Infrastructure
• PSTN Gateway or Router
• QoS-Enabled WAN Infrastructure

• IP Telephony Design Goals

Typical design goals of an IP telephony network are as follows:

End-to-end IP telephony: Using end-to-end IP telephony between sites that have previously established IP connectivity. IP telephony can be implemented as an add-on service to existing infrastructure.

• Widely usable IP telephony: To make IP telephony broadly useful, speech quality must be on par with traditional telephone; this is referred to as toll quality voice.
• Reduced long-distance costs: Long-distance charges should be lower than with standard phone service. This can be accomplished by routing phone calls through private IP networks or even the public Internet.
• Cost-effective: Using existing WAN capacity more efficiently and the cost of updating current IP network infrastructure to support IP telephony are both important factors in making IP telephony cost effective. In some circumstances, this purpose can be achieved by routing phone calls across the public Internet or private IP networks.
• High availability: Using existing WAN capacity more efficiently and the cost of updating current IP network infrastructure to support IP telephony are both important factors in making IP telephony cost effective. In some circumstances, this purpose can be achieved by routing phone calls across the public Internet or private IP networks.
• Lower total cost of ownership: Traditional telephony should have a higher total cost of ownership and less flexibility than IP telephony. The costs of implementing and operating two infrastructures are higher than the expenses of implementing and operating a unified system.
• Enable new applications on top of IP telephony via third-party software: An intelligent phone, for example, used to access database information instead of a PC, is expected to be easier to use and less expensive to acquire, operate, and maintain.
• Improved productivity: By extending productivity-enhancing enterprise telephony capabilities like voice mail and voice conferencing to distant teleworkers, IP telephony should boost the productivity of remote workers, agents, and stay-at-home employees.
• Facilitate data and telephony network consolidation: Consolidation can help save money on operations and equipment.

The following sections illustrate some sample IP telephony designs:

Cisco Unified Communications Manager, IP telephones, LAN switches with inline power (PoE), applications such as voice mail, and a voice-enabled router are all part of a single-site IP telephony solution. The IP telephones are powered by the LAN switch via their Ethernet interface. Users can make external calls using gateway trunks that are connected to the PSTN, CIsco Dubai, UAE.

Each site can be totally self-contained with single-site deployment. The PSTN is used to make all calls to the outside world and to remote areas. If an IP WAN is used in the single-site model, it is exclusively for data traffic and does not provide telephony services. As a result, if an IP WAN fails or the WAN’s capacity is insufficient, the call processing service or functionality is not affected. The only external requirements are a PSTN carrier and PSTN network route diversity. Use this strategy for a single campus or a facility with fewer than 30,000 lines as a best practise, cisco-ip-telephony-partner-in-Dubai, UAE

Multisite WAN with Centralized Call Processing Design

Cisco Unified Communications Manager at the central site links to outlying locations over the IP WAN in a multisite WAN design model with centralised call processing. The centralised Cisco Unified Communications Manager handles call processing for remote IP telephones. The IP WAN transfers voice traffic between locations and calls control signalling between the central and remote sites. Voice mail and IVR systems are likewise consolidated, lowering the total cost of ownership and allowing for centralised management and maintenance.

Cisco IP Phone: Communications Manager

The Enterprise Campus requires IP connectivity from the remote locations. Voice is converted into IP packets and sent to the local LAN through IP telephones, which are powered by a local LAN switch. The packets are forwarded to the right destination by the local router using its routing table. With Cisco Unified Survivable Remote Site Telephony (SRST) services, voice-enabled routers at remote sites can provide backup call processing functionality in the case of a WAN outage. Cisco Unified SRST provides backup call processing functionality on voice-enabled routers, extending high-availability IP telephony to branch offices.

The service provider must integrate QoS measures if a company demands high-quality voice communication over the WAN. A service level agreement (SLA) is a contract between a company and a service provider that ensures bandwidth and latency standards adequate for voice transfer, CIsco Dubai, UAE.

NOTE: The routers have speech capabilities, allowing voice communication with the rest of the world via the PSTN.

Use this architecture for a main site with numerous smaller remote sites connected via a QoS-enabled WAN but not requiring full capabilities and operation during a WAN outage, as a best practise, cisco-ip-telephony-partner-in-Dubai, UAE

Multisite WAN with Call Processing Distributed Design

A multisite WAN design architecture with distributed call processing is illustrated in Figure 8-21. This paradigm consists of a number of separate sites, each with its own call processing agent and connected to an IP WAN that transports voice traffic between them. Because each site has its own call processing agent, the IP WAN in this approach doesn’t transmit call control signalling between the sites. In most cases, the PSTN acts as a backup connection between the sites in the event that the IP WAN connection breaks or has inadequate bandwidth for incremental calls.

NOTE: A standalone site is one that is solely connected to the PSTN and is not covered by the distributed call processing architecture.

Use this architecture for a big central site with more than 30,000 lines or a deployment with more than six large sites (totaling more than 30,000 lines) interconnected via a QoS-enabled WAN as a best practise, CIsco Dubai, UAE

NOTE: Cisco Unified Communications Manager Express, which is embedded in Cisco IOS software and enables call processing for up to 240 Cisco Unified IP phones, may extend IP telephony capability to a small site or branch office. Customers can use this product to deploy a low-cost, dependable, and feature-rich solution.