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
2-18
Cisco Unified Wireless IP Phone 7921G Administration Guide for Cisco Unified CallManager Release 4.1, 4.2, 5.0
OL-10802-02
• VLANs for specific traffic
• Dynamic registration of devices
Although you can have up to eight queues on the access point, you should use only
two queues for voice traffic to ensure the best possible voice QoS. Place voice
(RTP) and signaling (SCCP) traffic in the highest priority queue, and place data
traffic in a best-effort queue.Although 802.11b/g EDCF does not guarantee that
voice traffic is protected from data traffic, you should get the best statistical
results by using this queuing model.
Note The Cisco Unified Wireless IP Phone 7921G marks the SCCP signaling
packets with a DSCP value of 24 and RTP packets with DSCP value of 46.
To improve reliability of voice transmissions in a nondeterministic environment,
the Cisco
Unified Wireless IP Phone 7921G supports the IEEE 802.11e industry
standard and is Wi-Fi Multimedia (WMM) capable. WMM enables differentiated
services for voice, video, best effort data and other traffic. However, in order for
these differentiated services to provide sufficient QoS for voice packets, only a
certain amount of voice bandwidth can be serviced or admitted on a channel at
one time. If the network can handle “N” voice calls with reserved bandwidth,
when the amount of voice traffic is increased beyond this limit, (to N+1 calls), the
quality of all calls suffers.
To help address the problems of VoIP stability and roaming, an initial Call
Admission Control (CAC) scheme is required. With CAC, QoS is maintained in a
network overload scenario by ensuring that the number of active voice calls does
not exceed the configured limits on the access point. The Cisco
Unified Wireless
IP
Phone 7921G can integrate layer 2 TSpec admission control with layer 3 Cisco
Unified CallManager admission control (RSVP). During times of network
congestion, calling or called parties receive a fast busy indication. The system
maintains a small bandwidth reserve so wireless phone clients can roam into a
neighboring access point (AP), even when the AP is at “full capacity”. After
reaching the voice bandwidth limit, the next call is load-balanced to a neighboring
AP without affecting the quality of the existing calls on the channel.
Implementing Quality of Service in the connected Ethernet switch is highly
desirable to maintain good voice quality. The COS and DSCP values that the
Cisco
Unified Wireless IP Phone 7921G sets do not need to be modified. To
configure QoS correctly on the access point, see the
“Configuring the Wireless
Network for Voice” section on page 2-28.