Specifications

pression codec’s. This allows for a selectable 64kbps (G711), 8Kbps (G729A) or 6.3Kbps (G723) bandwidth use
when preparing voice compression for IP transport. Compression is used to reduce the digitized voice into a
smaller bandwidth that can be carried in smaller packets. The VoIP gateway determines the compression
method for each call setup. There is also a certain amount of frame/packet overhead in each compression
channel. 64K of bandwidth can support 6~7 calls simultaneously. This can vary depending on efficiency fea-
tures like Silence Suppression and multiframe counts. Unlike switched networks, VoIP connections consist of
a sequence of numbered data packets. Since voice conversation is usually considered “real time” these pack-
ets need to be delivered in a consistent manner with minimal delay. This can be controlled via a Gatekeeper
which tracks and monitors voice packets. Gatekeepers are part of the H.323 standard but are not required.
The OfficeServ 7400 MGI cards are Gatekeeper compliant.
In any Ethernet environment, packet transfers are subject to delays and/or loss. If these delays are greater
than 200ms the voice quality will deteriorate. The Ethernet data traffic and network topology should be a
consideration when using VoIP. Network congestion will affect call quality in any VoIP application.
WALKING CLASS OF SERVICE
This feature allows users to make calls or use features from a station that is restricted. The users may either
use the WCOS feature code or the authorization code feature. Both methods change the class of service to
correspond with the station passcode or authorization code that is dialed. After the call is completed, the sta-
tion returns to its programmed class of service.
WIRELESS LAN—See Section 2.4.6
4.34