Cisco Cisco Unified MeetingPlace Express 2.0 White Paper
Cisco Systems
Network Provisioning and Configuration
Page 7
server limits the output to each client according to the lesser of that client’s connection
setting and the meeting room setting.
For example, say the meeting room is set to DSL, the presenter is set to LAN, one client
is set to DSL, and one client is set to Modem.
The meeting room setting of DSL overrides the presenter’s LAN setting, so the presenter
transmits to the server at a maximum of 250Kbs. The server then retransmits that back to
the presenter and to the DSL client as is, and to the Modem client at 40Kbs. To achieve
40Kbs, the system may have to drop some content, depending on the activity level of the
presenter.
The resolution setting also controls the traffic by limiting the bits per image. A meeting
room set at 640x480 will typically generate less than one third of the traffic at 1280x1024.
setting and the meeting room setting.
For example, say the meeting room is set to DSL, the presenter is set to LAN, one client
is set to DSL, and one client is set to Modem.
The meeting room setting of DSL overrides the presenter’s LAN setting, so the presenter
transmits to the server at a maximum of 250Kbs. The server then retransmits that back to
the presenter and to the DSL client as is, and to the Modem client at 40Kbs. To achieve
40Kbs, the system may have to drop some content, depending on the activity level of the
presenter.
The resolution setting also controls the traffic by limiting the bits per image. A meeting
room set at 640x480 will typically generate less than one third of the traffic at 1280x1024.
2.2.2 B e h a v i o r o n Sl o w a n d Co n g e s t e d Li n k s
Cisco MeetingPlace Express limits client output to a client in two circumstances:
•
The client’s connection bandwidth setting
•
When the server gets an output buffer full condition, typically due to slow or
congested links
In both cases, Cisco MeetingPlace Express responds by dropping content. It attempts to
do this in a smart fashion, meaning that the client’s display is usually still coherent, just
not updating as rapidly or dynamically as a faster client.
If the connection is sufficiently congested, which typically only happens on links shared
between multiple users or applications, the client eventually gives up and drops its
connection. It will attempt to reconnect, but if the conditions have not improved this may
not work.
While the difference between output limited by the bandwidth setting versus output
limited by congestion is not always obvious, there are several reasons to prefer that the
output be limited by the bandwidth. The bandwidth setting should be set appropriately if
possible. Advantages of using the bandwidth setting include:
do this in a smart fashion, meaning that the client’s display is usually still coherent, just
not updating as rapidly or dynamically as a faster client.
If the connection is sufficiently congested, which typically only happens on links shared
between multiple users or applications, the client eventually gives up and drops its
connection. It will attempt to reconnect, but if the conditions have not improved this may
not work.
While the difference between output limited by the bandwidth setting versus output
limited by congestion is not always obvious, there are several reasons to prefer that the
output be limited by the bandwidth. The bandwidth setting should be set appropriately if
possible. Advantages of using the bandwidth setting include:
•
Generally better responsiveness. When buffers are always full, the latency for
client updates is significantly increased.
•
Reduced network congestion. The server will be more likely to limit traffic before
links are congested.
•
Better server performance. Backed-up connections increase memory usage and
put a greater load on the processor
Note that congestion does not cause the server to change the bandwidth setting for client.
2.2.3 R o s t e r -On l y Me e t i n g s
Roster-only meetings, which are meetings with no application sharing, use the same rules
as above, but the server does not generate more than about 1Kbs per client.
as above, but the server does not generate more than about 1Kbs per client.