Network Router User Manual
(off−ACS) database to store the user names and passwords for the badges, Cisco does not recommend this
practice. Because the ACS must be queried whenever the badge roams between access points, the
unpredictable delay to access an off−ACS database could cause excessive delay and poor voice quality.
Wireless Network Infrastructure
The wireless IP Telephony network, just like a wired IP Telephony network, requires careful planning for
VLAN configuration, network sizing, multicast transport, and equipment choices. For both wired and wireless
IP Telephony networks, separate voice and data VLANs is often the most effective way of suggested
deployment to ensure sufficient network bandwidth and ease of troubleshooting.
Voice, Data and Vocera VLANs
VLANs provide a mechanism for segmenting networks into one or more broadcast domains. VLANs are
especially important for IP Telephony networks, where the typical recommendation is to separate voice and
data traffic into different Layer 2 domains. Cisco recommends that you configure separate VLANs for the
Vocera Badges from other voice and data traffic: a native VLAN for access point management traffic, data
VLAN for data traffic, a voice or auxiliary VLAN for voice traffic, and a VLAN for the Vocera Badges. A
separate voice VLAN enables the network to take advantage of Layer 2 marking and provides priority
queuing at the Layer 2 access switch port. This ensures that appropriate QoS is provided for various classes of
traffic and helps to resolve addressing issues such as IP addressing, security, and network dimensioning. The
Vocera Badges use a broadcast feature that utilizes multicast to deliver. This common VLAN ensures that
when a badge roams between controllers, it remains part of the multicast group. This last process is discussed
in detail when multicast is addressed later in this document.
Network Sizing
IP Telephony network sizing is essential to ensure that adequate bandwidth and resources are available to
meet the demands presented by the presence of voice traffic. In addition to the usual IP Telephony design
guidelines for sizing components such as PSTN gateway ports, transcoders, WAN bandwidth, and so forth,
also consider these 802.11b issues when you size your wireless IP Telephony network. The Vocera Badges
are a specialized application that stretch the number of wired clients beyond our typical deployment
recommendations.
Number of 802.11b Devices per Access Point
Cisco recommends that you have no more than 15 to 25 802.11b devices per access point.
Number of Active Calls per Access Point
Vocera uses two different codecs based on if it is a badge−to−badge (proprietary low−bit rate codec) call or a
badge−to−phone (G.711 codec) call. This table shows a percentage of available bandwidth by data rates and
gives you a clearer picture of the expected throughput:
Call Process 1
Mbps
2
Mbps
5.5
Mbps
11
Mbps
Badge−to−Phone (G.711)
20.7% 11.8% 6.3% 4.7%
Badge−to−Badge
(Proprietary Low−bit rate
codec)
9.4% 6.1% 4.2% 3.6%