Part I Part 1: Voip Reference Manual; 1. What Is Voice Over Ip? (Voip) - NEC UNIVERGE SV9100 Manual

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1 Part 1: VoIP Reference Manual
Voice Over IP Reference Manual
Rev 1.2 May 2015
1.1

1. What is Voice over IP? (VoIP)

Voice over IP (VoIP) is a technology that converts speech into data packets and transmits these
packets over IP (Internet Protocol) networks. As most organisations already have existing data
networks in place, considerable cost savings can be achieved by utilizing these networks for speech
transmission.
There are many factors that should be considered when implementing VoIP. Without careful planning
and installation there is the potential for poor quality speech, unreliability, and disruption to the
existing data networks.
This document describes the potential problems and possible solutions to these problems. There is
also a troubleshooting section to help with problems that can occur.
1.1 TDM to IP Conversion?
TDM (Time Division Multiplexing) is a technique used in traditional telephone systems to allow
multiple channels of information to be transmitted over the same physical medium by allocating a
different time interval ("slot" or "slice") for the transmission of each channel. This technique is used
internally in the telephone system but cannot be used over IP based data networks.
Therefore, it is necessary for the telephone system to convert the TDM data to IP packets. This
conversion is carried out by a DSP (Digital Signal Processors) on the GPZ-IPLE card. Each DSP
can handle one TDM-to-IP conversion. For example, a licensed 32 voip channel GPZ-IPLE card
allows 32 DSP resources to be used and can support 32 simultaneous TDM - IP calls.
1.2 VoIP Mode?
There are several methods of VoIP operation. These can be categorized as:
· Extensions (standards based phones)
· Extensions (proprietary – with greater feature transparency)
· Trunks (basic calls between multiple telephone systems or ITSPs)
· Networking (feature-rich networking between telephone systems)
The modes available depend on the model of telephone system and the hardware/software installed.
Please refer to the specific manual for your product to determine which modes are available.
1.3 Protocols and Standards?
VoIP is commonly used to connect telephone systems and telephones from different manufacturers
together. To allow this interoperability each system must adhere to the same standard and "talk the
same language" (known as a protocol). There are various standards and protocols that are used. The
most common types (and those used by NEC equipment) are: