A new IEEE working group plans to standardize the way session handoffs take place between heterogeneous types of 802-based networks.

The 802.21 working group is slated to officially begin work in March 2004, says David Johnston, the group's interim chair and a senior communications engineer at Intel. Its goal is to eventually enable client devices to automatically choose the best available network connection type and to seamlessly hand off sessions among networks during roaming without user involvement. 

This capability will grow increasingly important as mobile networks begin supporting real-time applications such as voice, conferencing, remote monitoring and video transport, which can't tolerate any perceptible session interruption.

Inter-network roaming will be achieved by standardizing how 802 networks, each with different media access control (MAC) mechanisms, pass important network information to Layer 3, where handoffs actually take place, says Johnston.

"From an IEEE 802 perspective, there are no procedures for seamless handover today," he explains. "We are interested in creating a generic mechanism that works for any 802 network."

Such networks, for example, include the suite of 802.11a/b/g wireless LANs, emerging 802.16e mobile metro Ethernet networks and 802.3 wired Ethernet LANs. Using Mobile IP for roaming today, Johnston says, "there are problems with network discovery and timing that cause breaks that can last several seconds."

This is because Mobile IP as yet has no way to gather relevant information about lower-layer network conditions from 802, he says.

Note that proprietary solutions for inter-network roaming exist from companies such as NetMotion Wireless, which claims hand-off, session persistence and no disruptions as users roam among IP networks of any kind. As time marches on, though, having a standard way to achieve this function will be important to accommodate all users, independent of vendor.

Johnston estimates that 802.21 standardization will take between one year (an optimistic view) and three years (the typical time frame for IEEE standards that are more complex than 802.21).

Joanie Wexler is an independent networking technology writer/editor in Silicon Valley.