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ViewStation EX User Guide
184 www.polycom.com
Table 6-2. Mixed Protocol Dialing Speeds
Multipoint Downspeeding
When necessary, the ViewStation EX system is able to downspeed
calls, meaning that it can dynamically reduce the data rate of the call
to accommodate incoming calls. For example, if there is an existing
point-to-point conference at 384 Kbps and an endpoint calls into the
conference at 128 Kbps, the conference systems will downspeed the
384 Kbps call to 128 Kbps so that all the sites are connected at 128
Kbps. Conversely, incoming IP and ISDN calls dialed at speeds
greater than the current conference speed are negotiated down to
the current conference speed and admitted into the conference (rate
matching).
However, if one of the systems cannot downspeed, the conference is
kept at the original data rate, while the incoming call keeps its own
data rate. The system with the lower data rate can send and receive
audio. It can also send video, but cannot receive video. For example,
if a system that is not capable of downspeeding connects at 384
kbps, the conference proceeds at 384 Kbps and admits the new
Network
Interface
Number of
Endpoints and
Type of Calls
Maximum Speed For Each
Party in the Call
(in Kbps)
ISDN(H.320) IP (H.323)
BRI with Mixed
Protocols (ISDN
and IP)
2 lines with:
1 ISDN + 1 IP
2 ISDN + 1 IP
2 IP + 1 ISDN
3 lines with:
1 ISDN + 1 IP
2 ISDN + 1 IP
2 IP + 1 ISDN
4 lines with:
1 ISDN + 1 IP
2 ISDN + 1 IP
2 IP + 1 ISDN
256
128
256
384
192
256
384
256
256
256
128
256
384
192
256
384
256
256