The Wired for Management (WfM) Initiative


So far, this chapter has discussed some of the more typical factors to consider when choosing a network card for an upgrade or for retaining existing network cards for use in new computer acquisitions. However, depending on the size of your network, there is another factor to consider: the total cost of managing the computers on your network. The Wired for Management (WfM) initiative is a framework that most of the industry's major players have adopted. You'll find most of the information about WfM at Intel's developer's Web site (www.intel.com/design/archives/wfm/index.htm), including one particular key component: Wake on LAN (WOL) technology for network adapter cards.

To understand how WOL fits into this scheme, it's best to start with a simple understanding of the key components of WfM:

  • Universal Network Boot

  • Asset Management

  • Power Management

  • Remote Wake-Up (Wake on LAN and Wake on Ring)

Universal Network Boot

The Universal Network Boot component is based on technology that allows a computer to boot over a network and download an operating system, or other software, from a management server. The Preboot Execution Environment (PXE) technology is the key part of this component. PXE allows a computer to be remotely booted after the remote wakeup function is invoked. By using industry standard techniques, such as DHCP, TFTP, and TCP/IP, adopting PXE technology does not require extensive changes to incorporate it into new PCs. It also allows for older systems, which do not understand the extended uses of these standard protocols, to continue to function because they can simply ignore the extensions.

For more information about the specifics of how PXE uses DHCP, TFTP, and TCP/IP and other protocols, see Chapter 28, "BOOTP and Dynamic Host Configuration Protocol (DHCP)."


Asset Management

The Asset Management component includes a database that keeps an inventory of software and hardware for systems on the network, and allows polling computers to get this information.

This means that a computer which hosts a database of the software and hardware components for other computers in the network can periodically query other computers on the network to ensure that those computers do indeed have the hardware/software components installed that the Asset Management software has stored in its database. This technology can detect such things as hardware additions (or software downloads performed by users).

From a security standpoint this is very important. For example, one of the major security problems in a large network is a user installing a modem (and thus bypassing all your network security mechanisms, such as a firewall). For software downloads, this component can also be an important security measure to ensure that "shareware" and other products are not downloaded to desktop computers. Any software that will be placed on desktop computers should undergo testing by your network administrative personnel before it is deployed on computers in the network.

Power Management

The Power Management component is included to provide support for the Advanced Configuration and Power Management Interface (ACPI) and for Advanced Power Management (APM), which helps reduce costs by reducing power consumption that PCs and assorted peripherals use. ACPI is a newer technology that has replaced APM. By placing a computer and its peripherals into a lower power state after a predefined time has passed with no user interaction, the computer's electricity use is greatly reduced. This results in money saved and, in some cases, less stress on the computer's components.

Remote Wake-Up

The Remote Wake-Up component is the component that is most relevant to this chapter. The WfM initiative supports two kinds of remote wake-ups for computers: by the LAN to which the system is connected, or through a telephone line connected to a modem (Wake on Ring). This second component is considered optional, but the capability to power up a computer by sending a specialized datagram to the computer is a key component that makes other components possible.

For example, taking inventory of existing software, or installing new software on a user's computer, usually must be done during normal working hours. This can result in lost productivity because the user is not able to use his workstation. Performing this same function during off-hours, such as in the middle of the night, removes this expensive obstacle. One alternative is to tell users to leave their computers up and running so that you can use an automated software package to perform the inventory or software installation functions. Yet there will always be someone who forgets. And there's the fact that while that computer is up and running, waiting to be inventoried or upgraded, electricity is being consumed. When you're talking about hundreds of computers, that also can be an important cost factor.

To wake up a computer from a low-power state or to boot the system if it has been powered off, the network adapter must be capable of sensing a "magic packet" that is directed to it, or to use the newer "packet filtering" method.

The WOL Network Adapter Card

The network adapter that is used in a WOL situation can be a PCI card that you install in a computer just like any other network card. There is also a LAN on Motherboard (LOM) specification that places the network card function directly on the motherboard, eliminating the need for a separate card that uses up an expansion slot. The most common method at this time is to use a network card that you have to install, however.

Because the adapter card must be capable of listening to the network, awaiting a signal telling it that it's time to wake up the computer, the card must have a power source. In Figure 7.4 you can see an example of this kind of card. The small cable is used to connect the adapter card to the motherboard to supply a power source so that the card is always listening for wake-up packets.

Figure 7.4. A small cable is used on some WOL cards to connect the card to the motherboard so that power can be supplied to the card.


You don't have to do anything for motherboard solutions. The network adapter circuitry on the motherboard is already connected to the computer's power source. However, most PCI cards available today require that you make a connection between the PCI card and the motherboard, using a small power cable supplied with the card just for this purpose. Read the documentation if you decide to use WOL cards on your network. Note that not only must the LAN card be WOL compliant, but the motherboard also must support this connection. Check the documentation!

The Alarm Clock: Magic Packets and Packet Filtering

There are two recommendations for signaling the LAN card that it's time to wake up the computer:

  • Magic Packets The first method uses a "magic packet," which is a special packet designed just for this purpose. When a specialized circuit in the network adapter card sees this packet on the network, it initiates the system wake-up.

  • Packet Filtering In the second method, which is the preferred method in version 2.0 of the WfM specifications, the card recognizes ordinary network packets addressed to it, instead of a specialized magic packet. This second method is referred to in the specifications as packet filtering and is not to be confused with the same term when applied to firewall technology.

Whichever method is used, either the computer can be booted when the LAN card receives a wake-up call, or it can simply resume normal operations if the computer has been put into a suspended low-power state without performing a complete shutdown. The preferred method is that the computer be placed in a suspended low-power state, but this is not an absolute requirement.

The "magic packet" method uses a special datagram that contains a source and destination address. The destination address can be a particular workstation's address, or it can be a broadcast address used to wake up multiple systems. The data portion of the packet contains synchronization bytes and the workstation's address repeated 16 times. Optional fields are also present in this datagram, but the point is that, by using this special kind of packet, the WOL network adapter to which it is addressed can begin the wake-up sequence of events. This allows it to either boot the computer or revive it from its low-power suspended state.

Should You Enable WOL?

Whether Wake on LAN is suitable for your LAN depends on how you manage your network. If you have frequent software updates or must be able to remotely manage workstations without having a technician sitting at the keyboard entering commands, you should consider using WOL and other WfM technologies. To do so you'll also have to use management software capable of formulating and sending out WOL packets, if the network adapter requires it. Using the newer specifications, you might want to purchase cards that can wake the dead, so to speak, by detecting any network traffic directed to them.

If you manage a small network and need to make only infrequent changes, or if all of your computer systems are located in close proximity to each other, you might find WOL unnecessary since you can do things the old-fashioned way, by visiting each computer when an upgrade is needed or a problem arises.

WfM and WOL are standard on most 10/100Mbps network cards, except for the least expensive models. However, for any network in which stability is of even minor importance it's generally not a good idea to opt for bargain basement NICs that may have problems further on down the line.




Upgrading and Repairing Networks
Upgrading and Repairing Networks (5th Edition)
ISBN: 078973530X
EAN: 2147483647
Year: 2006
Pages: 411

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