Cisco Cisco WebEx Meeting Center WBS30 White Paper
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Network Impairment Tolerance
In the top half of Figure 5, you’ll see a sample CMR Hybrid deployment, complete with an on-premises multipoint
control unit (MCU) or telepresence server (TPS). The bottom half retains the same call-control elements, but is
absent for on-premises MCU or TPS. The primary difference in these two environments is that telepresence
endpoints join the on-premises MCU or TPS in CMR Hybrid deployments, and send a single cascade link to
WebEx clients. In CMR Cloud, on the other hand, every telepresence endpoint individually calls into WebEx client.
Point 1 in the figure represents either the cascade link from CMR Hybrid, which is the MCU or TPS dialing into the
WebEx client, or each of the individual calls from telepresence endpoints into CMR Cloud. Point 2 represents the
on-premises endpoints calling into the MCU or TPS and any potential network impairment they may encounter on
this link. Note that if the participant is using Mobile and Remote Access through Cisco Expressway, this link also
would include that path over the public Internet.
For CMR Cloud, please consider this equivalent to any point-to-point testing you can perform on your local
enterprise network. This testing may include WAN or campus links that you must traverse in order to egress the
Expressway/VCS device to leave your network and dial into WebEx meetings. Position 3 in Figure 5 represents
Cisco WebEx desktop or mobile clients that have joined the meeting. When facilitating your own meetings, you’ll
Cisco WebEx desktop or mobile clients that have joined the meeting. When facilitating your own meetings, you’ll
want to note whether the desktop client is User Datagram Protocol (UDP)-capable or in fallback to Transmission
Control Protocol (TCP) mode, because it cannot open a UDP connection.
Figure 5. CMR Hybrid and Cloud Combined Network Requirements
WebEx clients have a limited capability to tolerate network impairments, such as loss, jitter, and high round-trip
times, when TCP-connected versus UDP (Table 7). It is extremely important to ensure that the WebEx client is
successfully connected to a WebEx meeting through UDP. Any WebEx desktop client, whether PC or Mac, simply
needs to check under Meeting > Audio & Video Statistics to see which ports the client is using (Figure 6).