Reliant Octel 300 Spezifikationen Seite 134

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IP Office Product Description
IP Office 4.2
© 2008 AVAYA All rights reserved.
Page 134
Issue 18.b.- (08 July 2008)
VoIP FAQ
Network Requirements
Quality of Service (QoS) is a measure of the performance of a network that reflects the availability of network
service and the quality of network transmissions. The term itself refers to a number of networking technologies
and techniques and does not necessarily restrict itself to any single protocol or standard.
There are a number of measures that can be taken on the LAN and WAN to make them 'good enough' to carry
voice traffic. Some of these are the implementation of standards based QoS protocols while are simply a
matter of network architecture and good network management practices.
The term 'good enough' is intentional. Every customer will have different expectations and different budgets to
work to. Some will be willing to upgrade their networks to use the best possible equipment and practices. To
others the additional expense may be viewed as unnecessary.
Examples of standards based Quality of Service protocols include DiffServ and 802.1p/q.
What are Voice Compression Modules (VCM's) for?
VCMs are required to support the following scenarios:
· Usage of Embedded Voicemail on the Small Office Edition (used as a memory boost by compressing the
voice files).
· Internal phone calls between an IP device and a non-IP device.
· Analog/digital phones to IP trunks (SIP/H.323) including managed Frame Relay and managed IP VPN
(provides echo cancellation).
· IP phones to ISDN or PSTN trunks (convert IP to TDM and vice-versa).
· Call set up between IP phones (VCM resource will be released after call set up if direct media is used) to
provide dial tone, busy tone etc. Direct media is a VoIP concept within the system that allows direct
connection of the media steam (IP packets containing voice samples of the telephone call) between the
two IP devices on the network.
VCMs are NOT required for:
· Calls between IP phones on the same system after call set-up (“Direct Media”), unless call recording is
enabled.
“Direct Media” is a VoIP concept that circumvents resources (TDM bus, Gateway) within the system and
improves the voice quality. If two IP devices are connected on the same system, a direct LAN connection
between them will be established once the call has been set up (as long as they use the same Codecs).
It is possible for an IP device to be physically located at one site while being registered at a different site. In
this case, even for VoIP across the WAN the VCM would not be used, as long as the two IP devices involved in
a phone call are registered on the same system.
Data Channels
A Data Channel is only required for Remote Access (RAS), Internet Access, and Voicemail connections:
· 10 PCs accessing the Internet over a single line = 1 Data Channel. If multiple lines are used (Multi-Link
PPP) then as many data channels are required (e.g. 128k i.e. 2B channels requires 2 data channels)
· 10 users dialing in from home on 10 separate lines onto the LAN = 10 Data Channels
· Voicemail is an IP application on the LAN (i.e. one data channel is required for each voicemail port used)
Note: IP end-points do NOT require data channels
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