Lesson
13: Voice Technology Basics
Convergence
of Voice and Data | Voice
Technology Basics | Voice
over Data Transports | Applications
|
Sample Migration
H.323 Interoperability
VoIP works with a company’s existing
telephony architecture, including its private branch exchanges
(PBXs) and analog phones.
VoIP and H.323 enables companies to complete
office-to-office telephone and fax calls across data networks,
significantly reducing tolls. New applications are available,
including unified messaging that integrates e-mail with voice
mail and fax.
Choosing VoIP
Customers may choose VoIP as their voice
transport medium when they need a solution that is simple
to implement, offers voice and fax capabilities, and handles
phone-to-computer voice communications. IP networks are proliferating
throughout the marketplace. Thus, many customers can use VoIP
today.
Integrating Voice and Data on the
WAN
The Voice over IP and H.323 standards define
how analog voice is converted to data packets and back again.
The next step is to use a company’s existing wide-area
network (WAN) to transport voice traffic with data traffic.
Serial (Leased Line) Services
T1 is a private-line digital service, operating
at 1.544 Mbps in a full-duplex, TDM mode. The 1.544-Mbps transmission
rate provides the equivalent capacity of 24 channels running
at 64 Kbps each.
The full-duplex feature of T1 allows the
simultaneous operation of independent transmit and receive
paths. Each data path operates at a transmission rate of 1.544
Mbps. Companies that need less bandwidth can deploy fractional
T1 trunks, using any number of channels needed. A fractional
service is tariffed on a linear pricing schedule, depending
on the number of T1 channels and the distance covered.
The TDM feature allows logical channels to be defined within
the T1 serial bit stream. The T1 bit stream may be channelized
in many different ways, as follows:
- A single 1.544-Mbps digital channel
(non-channelized) between the user’s premises and the
central office (CO)
- 24 independent channels, each providing
64 Kbps of bandwidth
- Any variation of 64-Kbps channel
combinations
Each logical channel may be independently transmitted and
switched. A combination of voice, video, and data may be transmitted
over a single T1 line.
Ideal Applications for T1 Services T1 service is ideal for
applications that require continuous high-speed transmission
capabilities.
Some common T1 applications include the following:
- High-volume LAN interconnection
- Integrated voice, data, video, and
imaging transmission
- Compressed video transmission
- Bulk data transfer
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