WakeOnLAN (WOL)

WakeOnLAN is the protocol name given to the so-called Magic Packet technology, developed by AMD and Hewlett Packard for remotely waking up a remote host that may have been automatically powered-down because of its power management features. Although power management allows companies and individuals to cut power usage costs, it presents a problem for IT departments especially in being able to quickly and efficiently remotely manage PC's, especially during off-hours operation when those PC's are most likely to be in a suspended or standby state, assuming power management features are enabled.

History

For a history of WakeOnLAN and Magic Packet technology, refer to either this wikipedia article, or read this AMD white paper.

Protocol dependencies

Packet Format

A physical WakeOnLAN (Magic Packet) will look like this:

Synchronization Stream

Target MAC

Password (optional)

6

96

0, 4 or 6

The Synchronization Stream is defined as 6 bytes of FFh.

The Target MAC block contains 16 duplications of the IEEEaddress of the target, with no breaks or interruptions.

The Password field is optional, but if present, contains either 4 bytes or 6 bytes. The WakeOnLAN dissector was implemented to dissect the password, if present, according to the command-line format that ether-wake uses, therefore, if a 4-byte password is present, it will be dissected as an IPv4 address and if a 6-byte password is present, it will be dissected as an Ethernet address.

Example traffic

Here is a screenshot of some WakeOnLAN traffic:

wol.png

Wireshark

The WOL dissector is fully functional for Ethertype 0x0842 and for UDP only. It was first included with Wireshark starting with SVN revision 23371 on November 6, 2007. General availability began with the 0.99.7 release of Wireshark.

Preference Settings

Currently, there are no preferences for the WOL dissector.

Example capture file

A simple example capture file containing WOL traffic is available on the SampleCaptures page.

Display Filter

A complete list of WOL display filter fields can be found in the display filter reference

Capture Filter

As WOL is currently implemented, you can use the following capture filter to be reasonably assured of capturing most WOL traffic; however, to guarantee all WOL traffic is captured, at least as far as the dissector is concerned, you should omit the "port 9" qualifier in the capture filter expression:

Discussion

WakeOnLAN (last edited 2014-02-11 22:46:57 by ChristopherMaynard)