Lesson
13: Voice Technology Basics
Convergence
of Voice and Data | Voice
Technology Basics | Voice
over Data Transports | Applications
|
Sample Migration
Frame Relay Services
Frame Relay is a packet-switching WAN technology
that has achieved widespread support among vendors, users,
and communications carriers. Its development has been spurred
by the need to internetwork LANs at high speeds while maintaining
the lower costs associated with packet-switching networks.
Frame Relay offers very high access speeds. In North America,
initial Frame Relay access rates start at 56 Kbps and go up
to 1.544 Mbps. In Europe, the initial Frame Relay access rates
start at 64 Kbps and go up to 2.048 Mbps. Companies can contract
with their service provider for a committed information rate
(CIR).
The Frame Relay standard today uses permanent virtual circuits
(PVCs). All traffic for a PVC uses the same path through the
Frame Relay network. The endpoints of the PVC are defined
by a data-link connection identifier (DLCI). The CIR, DLCIs,
and PVCs are defined when the user initially subscribes to
a Frame Relay service.
Frame Relay allows remote host access for applications such
as the following:
- Remote host connectivity
- Credit card authorization
- Online information services
- Remote order entry
Frame Relay supports multiple virtual connections over a single
physical interface. This means that Frame Relay is often the
ideal solution to provide many users with simultaneous access
to a remote location. In these cases, the Frame Relay connection
helps optimize the return on investment of the host system.
Voice over Frame Relay
Voice over Frame Relay (VoFR) technology
consolidates voice and voice-band data (including fax and
analog modems) with data services over a Frame Relay network.
The VoFR standard is specified in FRF.11 by the Frame Relay
Forum.
VoFR allows PBXs to be connected using Frame Relay PVCs. The
goal is to replace leased lines and lower costs. With VoFR,
customers can easily increase their link speeds to their Frame
Relay service or their CIR to support additional voice, fax,
and data traffic.
How VoFR Works
A voice-capable router connects both a PBX
and a data network to a public Frame Relay network. A voice-capable
router includes a Voice Frame Relay Adapter (VFRAD) or a voice/fax
module that supports voice traffic on the data network.
Choosing VoFR
Frame Relay provides another popular transport
for multiservice networks since Frame Relay networks are common
in many areas. Frame Relay is a cost-effective service that
supports bursty traffic well.
Frame Relay enables customers to prioritize voice frames over
data frames to guarantee quality of service (QoS).
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