IEEE approves formation of mesh study group for 802.11 protocols: The IEEE has approved the formation of a study group for fulfilling the promise of the wireless distribution system (WDS) that's been part of 802.11 since the beginning, Robert Moskowitz of TruSecure's ICSA Labs wrote in to tell us. The mesh study group will work inside of the 802.11 Working Group to take the extremely vague specification for the WDS and provide a protocol for auto-configuring paths between APs over self-configuring multi-hop topologies in a WDS to support both broadcast/multicast and unicast traffic in an ESS Mesh, according to the group formation proposal that was approved.
The study group isn't yet a task group--one of those 802.11 plus a letter designations--so the outcome of their work won't have as few steps to becoming a ratified standard.
The WDS part of 802.11 specifies the original and destination machine's MAC addresses, but also provides for two addresses for intermediate machines. In practical use of WDS to bridge wireless networks using gear from Linksys, D-Link, Buffalo, Apple, and others, each access point has a very loosely defined idea of where to pass traffic to get it closer to the destination address. The current implementations -- mostly a single Broadcom standard -- broadcast MAC addresses across access points as if the access points were ports on an Ethernet switch.
The new study group will provide a wider range of tools for establishing the paths between access points while also providing a protocol that can be developed against. Right now, multiple implementations of simple WDS don't always work together, and even multiple devices all using Broadcom's chipset and firmware use different ways of connecting and won't always interconnect.
Bonus: Explanation of WDS from The Wireless Networking Starter Kit, 2nd Edition
Here's how my co-author Adam Engst and I describe how WDS works from our book on wireless (2nd edition released last fall):
WDS is a clever part of the original 802.11b specification from 1999, but it wasn’t until 2003 that it started appearing in standard, inexpensive equipment. WDS connects access points wirelessly as if they were ports on an Ethernet switch.
On an Ethernet switch, each port keeps a list of all the machines connected to it and broadcasts that list to each other’s port. Every computer on the switch’s network receives these broadcasts and uses them to discover the MAC addresses of all the other accessible machines. Whether a computer wants to send data to another computer that’s on the same or a different port, it makes no difference: the originating computer still puts the same destination address on the packet. The switch, however, recognizes the destination address of each packet and routes it to the correct port and on to the destination computer.
Each access point in a WDS-connected network works in just the same way as a port, tracking the MAC addresses of all the connected computers and broadcasting lists of addresses to other access points. When a computer connected to one access point wants to send a packet to a computer connected to another, WDS ensures that the first access point delivers the packet to the appropriate access point, even through intermediate access points.
In the end, WDS appears seamless to you, and no special magic is involved. It’s just a clever way of keeping track of which computers are connected to which access points and making sure data can flow from any computer on the network to any other computer.