Specifications

B-1
Catalyst 4224 Access Gateway Switch Software Configuration Guide
OL-2031-02
APPENDIX
B
Synopsis of Basic VoIP Concepts
The Catalyst 4224 Access Gateway Switch (Catalyst 4224) provides Voice over
IP (VoIP) gateway applications for a micro branch office. This chapter introduces
some basic VoIP concepts.
This chapter contains these sections:
• VoIP Overview, page B-1
• A Voice Primer, page B-2
VoIP Overview
The VoIP application allows a Catalyst 4224 to convert analog voice signals such
as telephone calls and faxes into digital IP packets and distribute these packets
across a WAN. In VoIP technology, a digital signal processor (DSP) segments the
voice signals into frames and stores them in packets. These packets are
transported using IP in compliance with the International Telecommunication
Union-Telecommunication Standardization Sector’s (ITU-T’s) specification
H.323, the specification for transmitting multimedia (voice, video, and data)
across a network.
Because VoIP is a delay-sensitive application, you need to fine-tune your network
from end to end before implementing VoIP. Fine-tuning your network to support
VoIP incorporates a series of protocols and features that improve quality of
service (QoS). Furthermore, you must take traffic shaping into account to ensure
the reliability of VoIP.