Layer 2 roaming with both static WEP and LEAP has been shown to provide acceptable QoS using either G.711 or G.729. If LEAP is being used, it is recommended that users are defined locally on the ACS server. This is because using off−box databases have potentially unknown response times, which could adversely effect overall QoS during Layer 2 roaming.

Layer 3 Roaming

Layer 3 roaming occurs when a client moves from an AP that covers IP subnet A to an AP that covers IP subnet B. At this point, the client would no longer have an IP address or default gateway that is valid within the new IP subnet. Since the clients￿ IP address and default gateway are no longer valid, its existing data sessions or VoIP calls fail since the remote client can no longer reach the local client.

There are the following ways that clients can work in an environment where they are roaming across Layer 3 boundaries:

∙Obtain a new IP address or default gateway in the new subnet through DHCP. While this is supported on some operating systems, it is not an effective model for VoIP since it would break all existing calls (signaling and media).

∙Mobile IP (MIP) is a mechanism where routers within the network allow end points to keep their existing IP address or default gateway, and the routers handle rerouting packets to the clients on their new IP subnet. MIP requires Home Agent and (optionally) Foreign Agent functionality on the routers, as well as a MIP client on the end points. This functionality is not supported on the Cisco 7920.

Proxy MIP (PMIP) provides similar functionality to MIP, except that the end points do not have to have an embedded MIP client. The MIP client is contained in a network device, such as an AP, and that device acts as a MIP proxy for the end points that reside behind it. PMIP is currently supported on Cisco APs, but it is currently not supported for VoIP applications.

The Cisco 7920 does not currently support native Layer 3 roaming using MIP. In addition, the current lack of VLAN support on the Cisco APs when using PMIP prevents the Cisco 7920s from being deployed for Layer 3 roaming. The use of VLANs to create isolated voice and data traffic is required by Cisco AVVID design guidelines.

Note: In multistory WLAN deployments where the WLANs on each floor have different subnets, particular care needs to be taken in the RF site survey to ensure that stations on one floor do not roam to WLANs on floors above or below.

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

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Cisco Systems 7920 IP manual Layer 3 Roaming
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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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