Cisco Systems 7920 IP manual

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this AP. If either the association or authentication fails, it continues to try the next best AP.

Note: As a Cisco 7920 roams between APs, it re−authenticates with each new AP.

2.AP B sends a null MAC multicast using the source address of the Cisco 7920. This updates the Content Addressable Memory (CAM) tables in upstream switches and directs further LAN traffic for the Cisco 7920 to AP B, and not AP A.

3.AP B sends a MAC multicast using its own source address telling the old AP that AP B now has the client associated to it. AP A receives this multicast and removes the client MAC address from its association table. This message uses the Inter−AP Protocol (IAPP).

In trying to determine potential candidate APs for Layer 2 roaming, the Cisco 7920 uses several variables to determine the best AP to associate with. The variables are RSSI and QBSS. Definitions of these terms follow:

∙RSSI ￿ This is used by the Cisco 7920 to determine the signal strength and quality of available APs within an RF coverage area. The Cisco 7920 attempts to associate with the AP that has the highest RSSI value (and matching authentication or encryption Type).

∙QBSS ￿ This is a beacon Information Element (IE) that allows the AP to communicate the Channel Utilization (CU) to the Cisco 7920. The Cisco 7920 uses the QBSS value to determine if it should attempt to roam to another AP, as APs with high CU may not be able to effectively handle VoIP traffic.

When roaming, the Cisco 7920 uses the following model to determine which AP should be used as the handoff candidate:

1.Determine which APs are advertising QBSS in their beacons. These should be considered handoff candidates before APs that are not advertising QBSS. If any of these meet the threshold criteria, begin the roaming process.

2.If no APs advertise QBSS, or those advertising do not meet the threshold criteria, look for APs that are not advertising QBSS but have acceptable RSSI levels.

The amount of time it takes for the Cisco 7920 to roam between APs is dependent on the security model used (average times):

∙Layer 2 roaming with static WEP: less than 100ms.

∙Layer 2 roaming with LEAP (local ACS authentication): 200 to 400ms

Note: Delay times with LEAP could be longer than 200 to 300ms if the ACS server is heavily used by other applications (such as remote access dial−up or VPN, or TACACS authentication).

Layer 2 roaming time is the time between the last RTP packet seen on AP1 and the first RTP packet seen on AP2. It also includes the times it takes to re−authenticate and reassociate with AP2.

The following image shows a sample trace of a Cisco 7920 roaming to a new AP and the LEAP messaging that is between the Cisco 7920 and the AP:

Cisco − Wireless IPT Design Guide for the Cisco 7920 IP Phone

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Contents Table of Contents Introduction PrerequisitesRequirements Cisco 7920 IP Phone Overview Wlan OverviewRF Overview Site Surveys and Design Recommendations Components UsedVoIP QoS Rssi∙ Delay Variation Jitter Not to exceed 30ms Security for the Cisco 7920 and Wlan Networks Network Sizing Number of 802.11b Devices per APNumber of 802.11b IP Phones per AP Page Numbers of 802.11b Phones per Layer 2 Subnet or Vlan Understanding Layer 2 and Layer 3 Roaming Understanding Roaming TerminologyLayer 2 Roaming Page Layer 3 Roaming VLANs Wlan QoS for VoIP Page Page Page Interconnecting WLANs to Cisco Campus Infrastructure Connecting APs to the Catalyst 3550 SMI or EMI Connecting APs to the Catalyst 2950 EI Connecting APs to the Catalyst 2950 SICaveats and Limitations Call Admission Control Designing Around the Lack of Layer 3 RoamingOther Caveats and Limitations Related Information

7920 IP specifications

The Cisco Systems 7920 IP phone represents a significant advancement in wireless communication technology, designed specifically for enterprises that require mobility and efficiency in their communication systems. This versatile device integrates seamlessly into a Cisco IP telephony network, allowing users to maintain connectivity while on the move, which is essential in fast-paced business environments.

One of the key features of the Cisco 7920 is its robust wireless capabilities. Operating on the IEEE 802.11b/g Wi-Fi standards, it provides a reliable connection to corporate networks, ensuring that users can access voice, data, and video services without being tethered to a desk. The phone supports dynamic call handling and features a responsive LCD display that enhances user interaction, making it easier to navigate menus and manage calls.

The Cisco 7920 also offers exceptional sound quality, thanks to its advanced audio technology. With Wideband audio support, users can experience clarity in conversations, which is particularly important in environments where clear communication is vital. The phone is equipped with noise-canceling capabilities that reduce background noise, allowing users to focus on their conversations without distractions.

Security is another critical aspect of the Cisco 7920. The device supports several security protocols, including WPA and WPA2, ensuring that all communications are encrypted and secure. This is crucial for organizations that handle sensitive information and need to comply with industry regulations.

Additionally, the Cisco 7920 features an extended battery life, enabling users to make calls throughout the day without frequent recharging. Its lightweight design and ergonomic build make it comfortable to use for extended periods.

In terms of integration, the Cisco 7920 IP phone is compatible with various Cisco Unified Communications Manager software versions, allowing for easy configuration and management within existing network infrastructures. Its support for multiple languages also makes it a suitable choice for international organizations, accommodating diverse user groups.

Overall, the Cisco Systems 7920 IP phone combines the necessary features, technologies, and characteristics to meet the demands of modern enterprise communication. Its blend of wireless capability, superior audio quality, security measures, and integration versatility makes it an excellent choice for organizations seeking efficient and reliable communication solutions.
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