Specifications
Table Of Contents
- Cisco Unified Wireless IP Phone 7921G Administration Guide for Cisco Unified CallManager Release 4.1, 4.2, 5.0 and Later
- Contents
- Preface
- An Overview of the Cisco Unified Wireless IP Phone 7921G
- An Overview of the Voice Over IP Wireless Network
- Understanding the Wireless LAN
- Components of the VoIP Wireless Network
- Voice Over IP Wireless Network Configuration
- Site Survey Verification
- Setting Up the Cisco Unified Wireless IP Phone 7921G
- Before You Begin
- Installing the Cisco Unified Wireless IP Phone 7921G
- Powering On the Cisco Unified Wireless IP Phone 7921G
- Understanding the Phone Startup Process
- Using the Cisco Unified Wireless IP Phone 7921G Web Pages
- Using the USB Connection for Initial Phone Configuration
- Updating Phones Remotely
- Configuring Network Profiles
- Configuring USB Settings
- Configuring Trace Settings
- Using System Settings
- Configuring Settings on the Cisco Unified Wireless IP Phone 7921G
- Accessing Network and Phone Settings
- Configuring Network Profile Settings
- Changing Phone Settings
- Configuring the Security Certificate on the Phone
- Changing the USB Configuration
- Configuring Features, Templates, Services, and Users
- Configuring Cisco Unified Wireless IP Phones in Cisco Unified CallManager
- Telephony Features Available for the Phone
- Specific Configuration Options for the Cisco Unified Wireless IP Phone 7921G
- Configuring Softkey Templates
- Modifying Phone Button Templates
- Setting Up Services
- Configuring Corporate and Personal Directories
- Adding Users to Cisco Unified CallManager
- Managing the User Options Web Pages
- Creating Custom Phone Rings
- Viewing Security, Device, Model, and Status Information on the Phone
- Monitoring the Cisco Unified Wireless IP Phone Remotely
- Troubleshooting the Cisco Unified Wireless IP Phone 7921G
- Resolving Startup and Connectivity Problems
- Resolving Voice Quality and Roaming Problems
- General Troubleshooting Information
- Erasing the Local Configuration
- Providing Information to Users By Using a Website
- Supporting International Users
- Physical and Operating Environment Specifications
- Checklist for Deploying the Cisco Unified Wireless IP Phone 7921G
- Index
Chapter 2 An Overview of the Voice Over IP Wireless Network
Components of the VoIP Wireless Network
2-16
Cisco Unified Wireless IP Phone 7921G Administration Guide for Cisco Unified CallManager Release 4.1, 4.2, 5.0
OL-10802-02
access point can provide the best service, and then reassociate with the new
access point. When implementing stronger authentication methods, such as
WPA and EAP, the number of information exchanges increases and causes
more delay during roaming. To avoid additional delays, use CCKM to
manage authentication.
CCKM, a centralized key management protocol, provides a cache of session
credentials on the wireless domain server (WDS). As the phone roams from
one access point to the next, CCKM compresses the number of message
exchanges during roaming by providing a master key stored on the WDS for
the access point to use. The reassociation exchange is reduced to two
messages, thereby reducing the roaming time.
For details about CCKM, refer to the “Cisco Fast Secure Roaming
Application Note” at:
http://www.cisco.com/en/US/products/hw/wireless/ps4570/prod_technical_r
eference09186a00801c5223.html
Note In dual band WLANs, it is possible to roam between 2.4 GHz bands (802.11b/g)
and 5 GHz bands (802.11a). The phone moves out of range of one AP using one
band and into the range of another that has the same SSID but is using a different
band. This can cause gaps in voice communications. To avoid these
communication gaps, try to use only one band for voice communications.
Related Topics
• Voice Quality in a Wireless Network, page 2-16
• Interacting with Cisco Unified Wireless Access Points, page 2-12
• Voice Over IP Wireless Network Configuration, page 2-27
Voice Quality in a Wireless Network
Voice traffic on the Wireless LAN, like data traffic, is susceptible to delay, jitter,
and packet loss. These issues do not impact the data end user, but have serious
implications for a voice call. To ensure that voice traffic receives timely and
reliable treatment with low delay and low jitter, you must use Quality of Service
(QoS), and use separate virtual LANs (VLANs) for voice and data. By isolating
the voice traffic onto a separate VLAN, you can use QoS to provide priority