What is a Computer Virus?

Ah, nature.  The original model for everything we build.  The computer virus is no different.  It derives its name from its biological counterpart because they share similar characteristics.  A computer virus is a small software program that is designed to copy itself and spread from one machine to another.  Again, just like their biological counterparts, they are crafty devils.  Computer viruses have developed the ability to transfer copies of themselves over networks, on removable media such as CD/DVD’s, USB Drives, Memory Cards, etc.

Once again, just like their biological namesakes, computer viruses attach themselves to a host (some form of executable file – a program, video, song, etc.) in order to spread from machine to machine.  If the user tries to launch this infected program, the viruses code is executed as well, infecting the user.

There are two types of viruses:  resident and nonresident.  Nonresident viruses immediately look for other hosts that they can infect, do so, and then hand over control of the machine to the author of the malware.  Resident viruses make a nice home in your system’s memory, stay active in the background, and infect new hosts when the opportunity arises.  They also transfer control back to their maker.

The venerable John von Neumann led the work that pushed the “Theory of self-replicating automata” in the late 1940′s and early ’50′s.  In what Generation Y or the Millenials are sure to find funny, the first computer virus was the CREEPER virus.  The capabilities of viruses are similar to other forms of malware in that they can overtake your computer, harvest your personal information, turn your computer into a zombie on a botnet, etc.

What Can You Do?

Head over to my Removing Malware/Spyware/Viruses page.  You are going to want to download a free program from Microsoft called the Microsoft Safety Scanner.  This tool is a couple of notches above amazing.  That isn’t hyperbole, this tool will root out almost anything you throw at it.  I suggest that you follow the steps on that page.  You will now be sporting a nice, clean computer system.  Feels good, doesn’t it?

Prevent Viruses

An ounce of prevention is worth a pound of cure.  This statement could not be more true in the computer world.  Your behavior and computing habits will have much more to do with whether or not your computer gets infected than any other factor.  You MUST read my Secure Computing Habits page, and heed its advice.  Feel free to check out my Software to Prevent Problems page for my recommendations for FREE software that does a fantastic job of keeping your system clean should your guard ever drop.

There are tons of viruses out there, and they are all looking for a system to get into.  Don’t let yours be one of them.  Follow this advice, and the risk that you will be infected will decrease dramatically!

Oh, and don’t forget to hug your favorite Geek!

What is a Trojan Horse?

Perhaps not very shockingly, a trojan horse works just like the one from the myths.  A piece of malware masquerades as a safe application or file, but once it is executed, it infects your system.  A trojan horse can piggyback on a legitimate piece of software, an image, an mp3, a video, a PDF, you get the idea.  A trojan horse can attach itself to almost any kind of file, and once you open that file (sometimes your input isn’t even needed to execute a file), it is installed on your system.  In the early days, they were relatively tame compared to their modern counterparts.  Early trojan horses would change your desktop picture, screw around with your volume controls, change mouse and keyboard settings, etc.  Modern trojan horses typically install a backdoor into your system that allows an outsider access to your system.  The attacker can then copy or erase files, intercept your internet traffic – perhaps stealing your passwords, basically do anything that you can do, they can do.  Typically however, they are used to turn your computer into a zombie on a botnet.  The attacker then uses your computer along with thousands of others just like it, to send spam, issue denial of service attacks on websites (DDOS), or worse.

Malware is no longer the realm of one form of malware however.  I am afraid that those days are behind us.  Modern malware is typically part of a blended threat that combines portions of viruses, worms, trojan horses, and rootkits.  This amalgamation can be truly devastating.  These blended attacks will do things such as install a backdoor into your system, turn off your spyware, clean out the event log, become part of a botnet, self-propagate, and can even use scareware to trick a user into thinking that they have a virus on their machine, even when they don’t in order to get $69.99 and your credit card number(s).

Crap.  You Have One.  Now What?

Scary huh?  Don’t fret!  With some due diligence, you can defeat the infamous trojan horse!  The number one thing to do is to read my Secure Computing Habits page, and follow the advice.  I cannot stress this enough.  Your behavior will do more to prevent malware than any security system ever could.  Should you get bitten however, the only way to be 100% sure that it is gone from your system is to re-install your operating system.  Do I have your attention yet?  I thought so…you don’t want to do that.  You should, but you won’t.  It’s ok, I understand.  What you can do then is download Microsoft’s Safety Scanner.  If you run this, I am 99% confident that whatever malware you have on your machine will be detected and removed.  That 1% is something that you need to determine for yourself.

Want to learn more about trojan horses, viruses, worms, and rootkits in depth?  Check out Geek University!

As always, hug your favorite Geek!

In the continuing series on Malware, we have reached one of the most scary – and potent – forms of malware out there:  the rootkit.  In this article I’ll explain what a rootkit is, why it is dangerous, what different forms there are of this beasty, and what you can do to protect yourself.  It is very important to be aware of this form of malware as it will not make itself known to you unless you actively hunt it down.  Let’s dive in and figure out just what the heck these things are, shall we?

A What Now?

A rootkit originally came from UNIX-land and was a set of tools (some of which you may have heard of – netstat, passwd, etc.) that an attacker modified to gain full control of the computer – all the while being undetectable to the systems administrators.  It is extremely unlikely that you are here on a UNIX system, so let’s investigate what a rootkit is on a Windows machine.

A rootkit on Windows is a program that hides things (files, memory addresses, network connections and activity, processes, etc.) from the operating system, the user, and from other programs such as anti-spyware.  While a rootkit isn’t inherently evil, it usually is – since you are here.   It is easiest to think of Windows as analogous to the earth’s crust that you learned about in middle school:  it is a layered object with several rings.  At the center of this object is the kernal – the heart of Windows.  This is known as Ring 0; each ring outward from the core steps out (Ring 1, Ring 2, Ring 3) from the center.

Don’t worry, I won’t get too technical here.  Just know that each ring inwards gets more serious as we approach the core (the kernel).  For example:

A Ring 3 level rootkit may include the ability to intercept messages, exploit security vulnerabilities, or hook onto a common API to mask/hide a running process or file that is on your system.

A Ring 0 rootkit, also known as a Kernel-mode rootkit is very serious and can add to or replace portions of the operating system, portions of drivers, or even the kernel itself!  Kernel-mode rootkits are almost impossible to detect, and can be very hard to remove (I’ll get to that – no worries).  This is because they operate with the same level of permission and access that the operating system has.  This enables them to subvert monitoring by anti-malware tools, and many or all of the protections built into the operating system.

How does it do this you are wondering, aren’t you?  You are wondering right?  Well, I’m going to tell you anyway.  A rootkit uses a method called Direct Kernel Object Modification (DKOM) to hook kernel functions into the System Service Descriptor Table (the SSDT), or it modifies the gates between user mode and kernel mode.  Lost you didn’t I?  Think of it as a baddie that sneaks in a closing door to reach the vault with all of the money in it.  That still doesn’t answer how they got on your computer though, does it?  Typically, rootkits are installed by taking advantage of a security vulnerability in a piece of software (*cough* Adobe Reader *cough* Adobe Flash).  They can infect your machine through more traditional means as well (Trojan Horses, for example).  But you don’t get those, right?  Right?

Am I Screwed?

How do you know if you have one?  You don’t.  Unless you run this tool from Microsoft.  Download this tool and burn or transfer it to a blank CD/DVD/USB drive.  Put it into your machine and reboot.  Follow the steps necessary to scan your computer.  Simple.  Nice.

Don’t Get Screwed!

What can you do to prevent getting a rootkit?  Read my Secure Computing Habits page.  Download a strong anti-malware program, keep it updated, and scan your computer regularly.  Turn on your firewall, if it isn’t already.  This last step is the most difficult, only because it is a total pain in the you-know-what:  keep the applications that you use up to date.  I know that is almost impossible with Adobe updating their software every other day, and Apple updating iTunes daily.  Why are you using iTunes again?  Why (there isn’t a good answer here)?

For all intents and purposes, that is what rootkits are.  They are forms of malware that dig deep into your system and attach themselves to the very heart of your machine.  They are able to modify your system in order to prevent you from knowing that they are there, and thus removing them.  They can track you, steal your personal information, the sky is the limit with a rootkit.  It is probably the most dangerous form of malware you will come across.

If you’d like to know more, please check out Geek University where I will dive into these topics in-depth.  In the meantime, hug your favorite Geek!

I figure that the best way to answer this question is to show what equipment I use, talk a little bit about it, and show how it is set up.

Photo of my Main Desk

Once you walk into my office, the first thing that you are likely to notice is my main desk.  It is an L-shaped desk, and over the years, I have become accustomed to the versatility and desk space that an L-shaped desk affords.  I have had this desk for a long time, and I will probably cry when the time comes for a new one.

Where are the books!?

In this photo, you can see my UPS along the wall on the left.  My router shares a shelf with a RAIDGear NAS box that houses 4 1TB drives.  On the shelf below that, you will find two Mediasonic USB 3.0 drive enclosures that each house 4 2TB drives.  On the top right shelf, are two “ruggedized” external hard drives that are each 500GB.  On the shelf below, is an unused D-Link Gigabit switch, and some basic office supplies.

The left wing

This shot shows how the left wing of my desk is laid out.  I will detail the equipment in the next shot.

Equipment on the Left Side

In this shot, you will see my Logitech speakers (the old, good ones) that I have had as long as I have had the desk practically.  You will notice the charging station for my Logitech Revolution MX mouse (favorite mouse ever) next in line.  Sitting next to that is my Samsung Epic 4G which is a good phone, but Android is severely lacking in my opinion.  Sitting on the monitor base is a Seagate FreeAgent 500GB laptop drive.  One of my Zune HD’s (this one is the 32GB version, but I also have a 16GB and a Zune 80) is sitting in its dock next to it.  The next thing you will notice is the Wacom Intuous 4 tablet that I am woefully inadequate at using still.  There is a bluetooth receiver, and some cool USB hubs (there are 14 ports! – all filled – lol), and my Logitech Clearchat wireless headset that I use for dictating hanging from the monitor.  The monitor is a Samsung 22″ that I love due to its long neck that allows me to keep everything below.

The Corner

In the corner you will notice regular office supplies, a Thermaltake Black X2 with 2 2TB Western Digital Green drives.  I have had mixed luck with the Thermaltake enclosures, but the idea is great.  The center channel speaker is hidden behind my other phone, the Palm Pre.  You can see another Thermaltake enclosure in the background on the right side that houses a single 2 TB drive.  The monitor is an Acer 23″ that is good for what I use it for, and the 1920 resolution is very handy.  What you can’t see is the Western Digital 2TB external drive behind the center channel speaker.

The view from the cockpit

This is the view from where I sit.  You can see my favorite keyboard of all time, the Microsoft Ergo 4000 (of which I have 3 spares), and my Logitech mouse.  In front of me is an HP 27″ monitor that I love!  I do all of my photo and design work on it, and I do take the time to calibrate it if you are curious.  You can also see the 4th monitor on the desk, an AOC 23″ panel that I use for Twitter clients.  On top of that monitor is a Microsoft HD webcam, and I forgot to mention that the Acer monitor has a Logitech webcam on it as well.

The right side

You can see the rest of the desk in this shot.  Along the right, on the media cart is a Brother laser printer and a Western Digital 1TB external hard drive.  You also can see my killer paper puncher.

Secondary Desk

This is my secondary desk.  On the bottom left, the Cooler Master Wavemaster case houses an Exchange 2010 server that I run for some unknown reason.  I know that I will be going to Office 365 as soon as it is available.  The next case houses a home built Windows Home Server 2011 box with 12TB of internal storage.  The PC next to it is both my Linux Mint machine, and the machine that I use to run iTunes.  I would NEVER run iTunes on my main PC.  You can also see my Epson Artisan 830 printer on my file cart.  Behine the printer are 2 Seagate 1TB external drives, and a Maxtor 1TB external drive (which really sucks – btw).

The Secondary Desk

The glass top of the desk shows the myriad office supplies that I use.  The ’off ‘ monitor is used to manage the Exchange server, as a secondary monitor for Windows 7 and for Linux Mint.  It is a 19″ monitor from Balance – a company I never heard of, but I needed a monitor at the time.  The main monitor on this desk is a Samsung 22″.  In between those two monitors, is a Wacom Bamboo tablet.  You can also see my Plantronics bluetooth charging near the right corner of the monitor.  The laptop stand houses my main laptop – an Acer Timeline – that I really like.  Underneath it is an Acer Aspire One netbook that runs Backtrack.  You can see the iPad on its stand on the right side of the desk.  Front and center is my Toshiba netbook that I use mainly as a remote (as in remote control) server for the iPad so that I can use the iPad to wirelessly control my camera. Yes, I am a dork.

The Whiteboard Wall

All those classes on Geek University?  Well, this is where they begin.  I use my whiteboard a TON - for the classes on Geek University, for college projects, and for mind mapping programs and design ideas.  Yes, I know I need to clean it.  I do every week.  Seriously.

A bit of the 4th Wall

Photo of the Picture Wall

It’s a room right?  It has 4 walls.  I figured I would show you the 4th wall.  It is just decorative, with a tall media organizer housing some games and a few movies.  You can also catch a glimpse of the closet on the left that houses even more technology madness.  The keen-eyed will notice the autographed set piece from Hak 5′s Darren Kitchen (@hak5darren) and Shannon Morse (@snubsie). 

All that, and I realize that I didn’t talk about my PC!  The people that ask about my equipment are either those that are geeks themselves, or they don’t understand technology very well.  The geeks always want to know the details of your computer, so here goes:

I have a Cooler Master Cosmos case.  A good case is one of the best investments you can ever make when building a PC, and I live this case.  In it, is a Gigabyte motherboard (the ONLY motherboards I use), and Intel Q9450, and a Sapphire Radeon 4850X2.  I don’t play games on the computer AT ALL, so the 4 DVI’s on the card are way more horsepower than I need.  I use an OCZ Vertex 2 160GB SSD as my main drive, and an OCZ Agility 60GB drive as a scratch drive for Photoshop.  These two SSD’s are mounted in one drive cage, and the other 5 drive cages house 5 2TB drives.  I use a BFG ES-800 power supply.

A brief bit about how I use it:  on my main desk, the monitor on the left always has Outlook open so that I can keep track of appointments, deadlines, tasks, email, and contacts.  The main and secondary monitors are used for all of my main computing tasks.  The monitor on the left always has Zune running, and is where I put whatever I am researching.  The monitor in front of me is the production monitor where I create the content.  The monitor on the right is used for all instances of Explorer and for my Twitter client (which can either be Tweetdeck or MetroTwit).

There you have it.  I think that is all of the prudent technology in my office.  I must admit that it is a pretty sweet setup for what I use it for.  I think that is the key.  Each of us has different needs, and it is important to create an environment that suits that.  Set it up best for you, keep it clean and organized, and you are well on your way to becoming a happy Geek!

System Architecture

The above figure shows the architecture of a powerline networking system (in particular a HomePlug AV system).  The Higher Layer Entities (HLEs) above the H1 (Host) Interface may be bridges, applications or servers that provide off-chip services to clients below the H1 Interface. The Data Service Access Point (SAP) accepts Ethernet format packets, so all IP based protocols are easily handled.

The Architecture defines two planes as shown in Figure 1. The data plane provides the traditional layered approach with the M1 interface between the Convergence Layer (CL) and the MAC, and the PHY interface between the MAC and the PHY. In the control plane, the MAC is a monolith without conventional layering. In Figure 1 it is labeled as the Connection Manager (CM) since that is its primary function. The approach adopted for the control plane was chosen to provide more efficient processing and to provide implementers greater flexibility for innovation. Although part of the control plane in all stations, the Central Coordinator (CCo) entity will be active in one and only one station in a single HPAV network.

The Physical Layer

The Physical Layer (PHY) operates in the frequency range of 2 – 28 MHz and provides a 200 Mbps PHY channel rate and a 150 Mbps information rate. It uses windowed OFDM and a powerful Turbo Convolutional Code (TCC), which provides robust performance within 0.5 dB of Shannon Capacity. Windowed OFDM provides flexible spectrum notching capability where the notches can exceed 30 dB in depth without losing significant useful spectrum outside of the notch. Long OFDM symbols with 917 usable carriers (tones) are used in conjunction with a flexible guard interval. Modulation densities from BPSK (which carries 1 bit of information per carrier per symbol) to 1024 QAM (which carries 10 bits of information per carrier per symbol) are independently applied to each carrier based on the channel characteristics between the transmitter and the receiver.

This diagram shows a block diagram representation for the physical layer of a powerline transmitter and receiver (specifically a Homeplug AV specification).

On the transmitter side, the PHY layer receives its inputs from the Medium Access Control (MAC) layer. There are separate inputs for HPAV data, HPAV control information, and HomePlug 1.0 control information (the latter in order to support HomePlug 1.0 compatibility). HPAV control information is processed by the Frame Control Encoder block, which has an embedded Frame Control FEC block and Diversity Interleaver. The HPAV data stream passes through a Scrambler, a Turbo FEC Encoder and an Interleaver. The outputs of the three streams lead into a common OFDM Modulation structure, consisting of a Mapper, an IFFT processor, Preamble and Cyclic prefix insertion and a Peak Limiter. This output eventually feeds the Analog Front End (AFE) module which couples the signal to the Powerline medium.

At the receiver, an AFE operates in conjunction with an Automatic Gain Controller (AGC) and a time synchronization module to feed separate data information and data recovery circuits. The HPAV Frame Control is recovered by processing the received stream through a 3072-point FFT, a Frame Control Demodulator and a Frame Control Decoder. The HomePlug 1.0 Frame Control, if present, is recovered by a 384-point FFT. In parallel, the data stream is retrieved after processing through a 3072-point FFT for HPAV, a demodulator with SNR estimation, a De-mapper, De-interleaver, Turbo FEC decoder, and a De-scrambler for HPAV data.

The HPAV PHY provides for the implementation of flexible spectrum policy mechanisms to allow for adaptation in varying geographic, network and regulatory environments. Frequency notches can be applied easily and dynamically, even in deployed devices. Region-specific keep-out regions can be set under software control. The ability to make soft changes to alter the device’s tone mask (enabled tones) allows for implementations that can dynamically adapt their keep-out regions.

MAC Protocols and Services

HPAV provides connection-oriented Contention Free (CF) service to support the QoS requirements (guaranteed bandwidth, latency and jitter requirements) of demanding AV and IP applications. This Contention Free service is based on periodic Time Division Multiple Access (TDMA) allocations of adequate duration to support the QoS requirements of a connection.

HPAV also provides a connectionless, prioritized Contention based service to support both best-effort applications and applications that rely on prioritized QoS. This service is based on Collision Sense Multiple Access/Collision Avoidance (CSMA/CA) technology which is applied to only traffic at the highest pending priority level after the pending traffic with lower priority levels has been eliminated during a brief Priority Resolution phase at the beginning of the contention window.

To efficiently provide both kinds of communication service, HPAV implements a flexible, centrally-managed architecture. The central manager is called a Central Coordinator (CCo). The CCo establishes a Beacon Period and a schedule which accommodates both the Contention Free allocations and the time allotted for Contention-based traffic. As shown in Figure 3, the Beacon Period is divided into 3 regions:

• Beacon Region
• CSMA Region
• Contention-Free Region

The Central Coordinator broadcasts a beacon at the beginning of each Beacon Period; it uses the beacon to communicate the scheduling within the beacon period. The beacons are extremely robust and reliable. The schedules advertised in the Beacon are persistent—i.e., the Central Coordinator promises not to change the schedule for a number of Beacon Periods—and the persistence is also advertised in the beacon so that the transmitting station for a connection can confidently transmit during its persistent allocation(s) even if it has missed several beacons within the advertised persistence of the schedule. This provides additional continuity even if a few beacons are missed. The CSMA periods are also persistent so that stations wishing to send CSMA traffic can do so even if they miss a few beacons.

The MAC layer provides both Contention (CSMA) and Contention Free (CF) services through the respective regions in the Beacon Period. The Central Coordinator-managed Persistent Contention Free (PCF) Region enables HPAV to provide a strict guarantee on Higher Layer Entity (HLE) QoS requirements. An HLE uses the Connection Specification (CSPEC) to specify its QoS requirements. The Connection Manager (CM) in the station evaluates the CSPEC and, if appropriate, communicates the pertinent requirements to the Central Coordinator  and asks the Central Coordinator for a suitable Contention Free allocation. QoS features specified in the CSPEC include:

• Guaranteed bandwidth
• Quasi-Error free service
• Fixed Latency
• Jitter control

If the CCo is able to accommodate the connection request, it will ask the stations to “sound” the channel. This allows the stations to perform the initial channel estimation (i.e., establish a Tone Map specifying the optimal modulation on each OFDM tone). The Tone Map is communicated from the receiver to the transmitter; the channel estimation is also communicated in abbreviated form to the CCo to help it determine how much time should be allocated to the connection. Based on the CSPEC and the channel sounding results, the CCo provides one or more persistent time allocations—Transmit Opportunities (TXOPs)—for the connection within the PCF Region.

The PCF Region also contains time for non-persistent allocations good only in the current beacon period. These non-persistent allocations are used to provide additional short term bandwidth to connections that require it (e.g., because of transient errors or changing channel conditions) to meet their QoS requirements, providing that the transmitting station hears the beacon at the beginning of the Beacon Period. When this time is not used for non-persistent CF allocations, in may be used for CSMA traffic. Again, stations must hear the beacon in order to know whether the time is available for CSMA traffic.

Messaging in HPAV is direct from station to station; however, the Central Coordinator monitors the messages. The header of each message contains information about how much data is pending for transmission on the connection; if this amount becomes large on a given connection, the Central Coordinator may allocate additional non-persistent time to the connection in the PCF Region.

The Persistent CSMA Region provides prioritized contention-based communication. It is used where there is no CSPEC and/or the traffic is of short duration. When operating in 1.0 Coexistence mode, or “Hybrid Mode”, AV coordinates with HomePlug 1.0 devices and permits them to communicate during the CSMA period.

As shown in the diagram below, the Beacon Period is synchronized to the AC line cycle. By synchronizing to the line cycle, HPAV provides stability of the periodic allocations relative to the line cycle. This, in turn, provides better channel adaptation to the synchronous (to the line cycle) interference, resulting in improved throughput. The beacon provides announcements of where the beacon will occur over the next few beacon periods—i.e., beacon persistence—to enable continued communications by stations that miss an occasional beacon.

MAC Control Plane

The Medium Access Control (MAC) Layer contains an integrated Connection Manager (CM). HLEs provide a Connection Specification (CSPEC) that details QoS requirements for application data. For bridged traffic, CSPECs may be generated dynamically by the Auto Connection Service (ACS) or by a higher layer QoS Manager that coordinates QoS over multiple network segments; otherwise the traffic is transmitted as prioritized CSMA traffic.

The Control Plane provides a seamless interface to the application layer. Application requirements are received at the H1 Control SAP in the CSPEC and are interpreted by the CM. The CM is responsible for evaluating the CSPEC and setting up the appropriate connection in conjunction with the CM in the station at the other end of the connection and with the CCo. It is the Connection Manager’s responsibility to ensure that the appropriate AV mechanisms are engaged in order to provide the application with the bandwidth it requires. It must also monitor the level of service that the connection is receiving and take remedial action if the guaranteed QoS is not being provided.

The MAC also maintains a clock that is tightly synchronized to the Central Coordinator’s clock (the Central Coordinator includes a timestamp in the beacon). This means that the entire HPAV network shares a common network clock for use by HLEs that have tight timing constraints (e.g., to synchronize surround sound speakers).

MAC Data Plane

In the Data Plane, the MAC accepts MSDUs (e.g., Ethernet packets) arriving from the Convergence Layer and encapsulates them with a header, optional Arrival Time Stamp (ATS) and Check Sum to create a MAC Frame. The MAC Frames are then en-queued into the appropriate MAC Frame Stream. It is the MAC’s responsibility to ensure that the MSDUs related to a given connection are delivered to the PHY in a timely fashion for transmission during the time allocated for the connection. For this purpose, it maintains individual queues for each connection’s data, for each priority level of CSMA traffic and for each priority level of Control Messages.

Each MAC frame stream is divided into 512 octet segments each of which is encrypted and encapsulated into a serialized PHY Block (PB). As shown in Figure 4, the PBs are packed into an MPDU which is delivered to the PHY. The PHY transmitter applies forward error correction and places the resulting PPDU onto the power line as described in the PHY section above.

As the receiver reconstructs the MSDUs, it selectively acknowledges the PBs; those that are not positively acknowledged are retransmitted during the next TXOP. The Selective Acknowledge (SACK) is an integral part of the TDMA allocation. When all the PBs composing an MSDU have been received correctly, the segments are decrypted and the resulting MSDU is passed to the Convergence Layer for delivery to the appropriate HLE.

Control messages are processed in an analogous fashion.

Since FEC and Selective Acknowledgment (SACK) are performed on relatively small blocks of data, the FEC is more robust and retransmissions are minimized. These two features contribute to HPAV’s ability to operate at near channel capacity.

Central Coordinator

Each Central Coordinator controls an AV Logical Network (AVLN) which consists of several AV stations which all share a common Network Membership Key (NMK). The NMK and other details of security and encryption are discussed below. For now, it is sufficient to know that the NMK provides exclusive access to an AVLN so that the member stations can communicate in a private and secure environment.

As described above, the Central Coordinator provides bandwidth management services for the AVLN. These include admission control (determining whether to admit a new connection when it is requested). If the connection is admitted, the Central Coordinator schedules time allocations for the connection in the PCF Region. It manages this schedule via the beacon, which contains:

• the current schedule and the minimum number of Beacon Periods for which it will remain valid, and/or
• the new schedule and the number of Beacon Periods which will pass before it becomes valid.

When an AV Station is powered on, it listens to the medium. If it hears an existing AVLN, it will attempt to join it. If it does not hear an existing AVLN, it will form its own network by becoming a Central Coordinator and broadcasting a beacon. Eventually, another AV Station will be powered up and the two will associate and form an AVLN. (This is a highly simplified description; in reality, the HPAV specification provides for various cases of encountering more than a single AVLN, encountering HomePlug 1.0 devices, encountering other Powerline Networks and combinations thereof.)

The Central Coordinator attempts to learn the topology of its AVLN and of any neighboring AVLNs. To achieve this, each AV station broadcasts a Discover Beacon periodically (at a time allocated by the Central Coordinator in the non-persistent portion of the PCF Region). This Discover Beacon contains information about the station and the AVLN to which it belongs.

Each station that hears the Discover Beacon adds the information it contains to a Discovered Station List (DSL). While building its DSL, if the station encounters a Discover Beacon from a station in a different AVLN, it adds the information about the other network to a Discovered Networks List (DNL). Periodically the Central Coordinator asks each station for its DSL and DNL and use the collected lists to compose a topology map.

The Central Coordinator uses the topology map it builds from the collected DSLs and DNLs to determine if there is another station in the AVLN that would make a better Central Coordinator than it. The criteria for making this decision, in order of priority, are:

1. User’s Selection
2. Central Coordinator Capability
3. Number of discovered STAs in the Discovered Station List
4. Number of discovered AVLNs in the Discovered Network List

If the current Central Coordinator finds another station that would make a better Central Coordinator, it will negotiate a handover of Central Coordinator functions to the new Central Coordinator. Depending upon the capabilities of the old and new Central Coordinators, the handover may or may not result in existing connections being torn down.

The Central Coordinator may also select another Central Coordinator-capable station to be its backup in case of failure. If the station accepts the backup role, it will monitor the AVLN and, if the Central Coordinator’s beacon is not heard by any stations in the AVLN for a specified number of Beacon Periods, the backup Central Coordinator will assume the role of Central Coordinator and attempt to maintain the existing connections without disruption.

Since a station must be capable of communicating with the Central Coordinator in order to join an AVLN and establish connections, a proxy capability is provided to support stations that are hidden from (i.e., unable to communicate with) the Central Coordinator. This capability provides for the creation of a Proxy Coordinator (PCo) to repeat the beacon information in Proxy Beacons and to relay control messages between the hidden station and the Central Coordinator. Note that only control messages are relayed. The station must be able to communicate directly with any stations with which it wishes to establish a connection. The PCo also transmits a Proxy Beacon during each Beacon Period to convey scheduling and other information to the hidden station.

When all stations are idle, the Central Coordinator causes the AVLN to enter a power saving mode. In this mode, there is only a small CSMA Region (so stations can initiate communication) and a small PCF Region (just long enough for Discover and Proxy beacons). Stations must have their receivers on during these small regions to participate in the AVLN; they may turn their transmitters and receivers off for the remainder of the Beacon Period. This makes it easier for stations to qualify for Energy Star certification.

Convergence Layer

The Convergence Layer (CL) serves as the interface between the HLEs and the MAC in the Data Plane. It accepts data payloads through Service Access Points (SAPs) at the H1 Interface and processes them as needed prior to handing them off to the MAC through the M1 interface. The only Data SAP specified by AV is the Ethernet II-class stack. This stack supports packet formats as specified by IEEE 802.3 with or without IEEE 802.2 (LLC), IEEE 802.1H (SNAP) extensions, and/or VLAN tagging. Using the Ethernet format makes it easy for AVLNs to interface to other LANs.

Among the services the CL provides on the transmit side are classification and auto connection. If requested for a connection, the CL will also associate an Arrival Time Stamp (ATS) with the data payload. On the receive side, the CL provides (optional) smoothing and insures that the received MSDUs are delivered to the appropriate H1 Service Access Point (SAP). On both sides, it provides the Connection Manager sufficient information to monitor the level of QoS being provided by the connection.

When a connection is established, the CM provides the classifier with a set of rules that will enable the classifier to uniquely associate incoming packets with the connection. For example, a set of rules might specify the source and destination MAC addresses and the TCP source and destination ports of the connection.

The classifier examines each packet received at the H1 interface and attempts to match it with a connection using the classification rules that have been provided to it. If it finds a match it will label the packet with the Connection ID (CID) of the appropriate connection, otherwise the classifier will release the packet for transmission in the CSMA region at the appropriate priority level.

If the transmitting station supports the optional Auto Connect Service (ACS), all packets which are released by the classifier without being associated with a connection will be examined by the ACS which will evaluate the data flow(s) between a given source and destination and attempt to identify flows which are worthy of a connection. This evaluation and identification may be based on a mix of the following:

• Policies established by an HLE (or a manufacturer),
• Templates such as traffic associated with ports known to have a particular usage,
• Heuristics such as the volume and regularity of data which is being transmitted.

Until the ACS identifies a connection, it releases the packets for transmission in the CSMA period immediately upon completion of the packet’s inspection.

If the ACS identifies a particular data flow as connection worthy, it behaves in a manner analogous to an HLE and asks the CM to set up a connection, providing classifier rules, etc. When the CM establishes the connection, the Classifier will start associating the packets with the newly established connection and the ACS will no longer see them. The ACS is, however, responsible for servicing the connection in the same way that an HLE would.

At the receiving station, the CL demuxes the received packets. If the packets are associated with a connection for which smoothing (a.k.a. de-jittering) has been requested, the CL will buffer the packets for the appropriate time so that all packets are released to the HLE at a fixed interval after they arrived at the H1 interface at the transmitter, which the receiver knows from the ATS it received with the packet and the synchronized network clock.

On both ends of a connection, the CLs provide sufficient information to the CM that it can monitor the level of QoS being provided to a connection to insure that the guarantees are being met. The CM will take corrective measures specified by the CSPEC if there are any violations to the QoS guarantees.

System virtual machines fall into two categories: Type 1 hypervisors (on the left), which run directly on the host hardware, and Type 2 hypervisors (on the right), which run on top of another operating system. Both are capable of running multiple independent instances of one operating system or different operating systems, all of which behave as though they are solely in control of the system.

Can a computer exist without hardware? It can if it’s a virtual machine. A virtual machine is software that’s capable of executing programs as if it were a physical machine—it’s a computer within a computer. Virtual machines can be divided into two broad categories: process virtual machines and system virtual machines.

A process virtual machine is limited to running a single program, which makes sense if you think about it. A system virtual machine, on the other hand, enables one computer to behave like two or more computers by sharing the host hardware’s resources. A system virtual machine consists entirely of software, but an operating system and the applications running on that OS see a CPU, memory, storage, a network interface card, and all the other components that would exist in a physical computer. For the remainder of this article, we’ll use the term “virtual machine” to refer to a system virtual machine.

Software running on a virtual machine is limited to the resources and abstract hardware that the virtual machine provides. Since a virtual machine can provide a complete instruction set architecture (ISA, a definition of all the data types, registers, address modes, external input/output, and other programming elements that a given collection of hardware is capable of working with), a virtual machine can simulate hardware that might not even exist in the physical world.

Using virtual machines, a computer can run several iterations of an operating system—or even several different operating systems—with each OS isolated from and oblivious to the existence of the others. The only requirement is that each operating system must be capable of supporting the underlying hardware. And, of course, there must be enough resources (memory, hard disk space, CPU cycles, and so on) to support everything. You could use a virtual machine to run Linux on top of Windows, for instance, or you could run two versions of Windows and use one as a sandbox for testing software you wouldn’t trust on a “real” – ie. physical – computer.

More Powerful than a Supervisor

The software that manages this trick is known as a hypervisor. A Type 1 (native) hypervisor is a program that runs directly on the host hardware, i.e., as an operating system in and of itself. Microsoft’s Hyper-V, formerly known as Windows Server Virtualization, is one example of a Type 1 hypervisor. A Type 2 (hosted) hypervisor, such as Microsoft’s Virtual PC 2007, runs on top of another operating system.

IBM developed the technology for its big-iron mainframe computers in 1967, but the Intel x86 architecture at the foundation of IBM PC-compatible machines was not well suited for running hypervisors. Achieving full virtualization required exceedingly complex code, which hampered runtime performance. Although it remained a fixture in mainframe and midrange computer systems, virtual machine technology saw very little progress during the 1980s and 1990s.

In the last few years, however, AMD and Intel both developed extensions to their x86 architectures that render newer CPUs much more suitable for running hypervisors. AMD has dubbed its extensions AMD Virtualization (AMD-V); Intel calls its extensions Intel Virtualization Technology (Intel VT). AMD-V is present in many newer AMD CPUs, including the Athlon 64 and Athlon 64 X2 (socket AM2 only), the Phenom X3 and X4, and second-generation Opteron server parts.

You’ll find Intel VT in about half of Intel’s Core 2 Duo desktop processors (the E6600 through E6850, and the E8200 through E8600), all of its Core 2 Quad and Core 2 Extreme desktop processors, and its quad-core Xeon and Itanium server procs (the Itanium version is formally known as Virtualization Technology for IA-64). Intel’s upcoming Core CPU will feature Intel’s VT-d (Virtualization Technology for Directed I/O), which will enable guest virtual machines to directly use peripheral devices, such as a network interface device. Although AMD-V and Intel VT are similar, they’re not compatible; a hypervisor that supports only AMD-V will not take advantage of the virtualization extensions in an Intel CPU and vice versa. Fortunately, hypervisors that support both sets of extensions are common.

Applications for Virtual Machines

What are virtual machines good for? The most common application today is server deployment. A virtual machine can make much more efficient use of a server’s hardware by running several instances of the same operating system and the same applications in parallel, or even different operating systems and applications.

In either scenario, each instance thinks it has sole access to the hardware and behaves accordingly. The hypervisor dynamically assigns virtual resources (such as processors and memory) to physical resources so that the hardware is never left idle. Think of it as maximizing the capabilities of your hardware all the time.  Virtual machines are also useful as test platforms: System designers and application developers can experiment with new code without disrupting or interfering with the usual production environment.

But virtual machines are useful for individual users, too. Experimenting with different operating systems—such as Linux—on one computer is just one example. Trying out new software—especially shareware—is another. If a program renders your system unstable, you can blow away the virtual machine without any consequences. Or if you’re paranoid about privacy, you could create a virtual machine explicitly for web browsing: Isolate all your personal information on one installation that you never use for web surfing. Fire up the virtual machine when you do want to browse the web and tracking cookies, spyware, and any other Internet detritus you encounter will be trapped there, where it can’t harm your production environment.

Getting started with virtual machines is certainly cheap enough: Several programs are available for free, including Microsoft’s Virtual PC and Oracle’s VirtualBox (the latter of which is capable of running Windows as a guest operating system running on Linux).  There are apps you can download such as Sandboxie which will place your browser in a sandboxed instance, protecting you from threats from the internet.

DirectX 10 marked a radical departure from DirectX 9: In order to be compatible, a graphics processor must feature a unified architecture in which each shader unit is capable of executing pixel-, vertex-, and geometry-shader instructions. The changes in DirectX 11 aren’t quite as fundamental, but they could have just as big an impact—and not only with games.  DirectX 11 features improved parallelism, improved precision and integer processing, tight integration between compute shaders and the rendering pipeline, and improved ease of programming along with better memory usage.

DirectX 11 is a superset of DirectX 10, so everything in DirectX 10 is included in the new collection of APIs. In addition, DX11 offers several new features and three additional stages to the Direct3D rendering pipeline: the Hull Shader, the Tessellator, and the Domain Shader. And in an effort to deliver cross-hardware support for general-purpose computing on graphics processors, Microsoft has come up with a new Compute Shader.  One advantage of compute shaders over other programming models for parallel processors is that they share a unified instruction set with other shader types used for graphics programming, such as pixel and vertex shaders.  So although compute shaders are something new to DirectX 11, some shader models with reduced feature sets can run on earlier (pre-DirectX 11) hardware:

Shader Model 4.0 – DirectX 10 or newer hardware
Shader Model 4.1 – DirectX 10.1 or newer hardware
Shader Model 5.0 – Direct X 11 or newer hardware

DirectX 11 will be compatible with both Vista and Windows 7, but many of its graphics features will be available on GPUs designed for previous iterations of Direct3D. Tapping into the Tessellator’s power, however, will require a GPU with transistors dedicated to the task (in this sense, DX11 marks a slight departure from DX10’s vision of a unified architecture). Let’s explore the concept of tessellation now.

Mmmmm….Tessellation…

The three new pipeline stages we mentioned earlier are all related to tessellation. They reside in the geometry-processing stage, between the Vertex Shader and the Geometry Shader. Tessellation can rapidly create the primitive elements that go into the creation of a complex three-dimensional object by subdividing just a few at a time. In this case, the primitives are called patches, which are defined by control points (visualize Photoshop’s pen tool, except that DX11’s control points manipulate a surface instead of a line). Patches replace the triangles used in previous versions of DirectX. Each subsequent subdivision creates more primitives, with each group being smaller than the last. Increasing the number of primitives in a model makes that model look more realistic. The Tessellator can also reshape these primitives by adjusting the control points to form more complex geometry.

While it’s very easy for GPUs to produce coarse objects like cubes, they have a much harder time creating objects with smooth curves. By tessellating a coarse object, a cube, for example—a GPU can transform that object into something that does have smooth curves, such as a sphere—and the kicker is that this process requires relatively little GPU horsepower and graphics memory.

(Click on the image to enlarge. Image courtesy of How Stuff Works.com)

Here’s a broad overview of how tessellation works: The Vertex Shader outputs patches, which then travel down the pipeline to the Hull Shader. The Hull Shader analyzes the patches’ control points to determine how the Tessellator should be configured (generating so-called “tessellation factors”) and then sends the patches on to the Tessellator. The Tessellator, in turn, subdivides the patches and feeds a stream of points to the Domain Shader. The Domain Shader manipulates these points to form the appropriate geometry and sends the resulting vertices to the Geometry Shader.

Hardware tessellation isn’t a new concept. Animators at Pixar began using tessellation to create their highly detailed characters beginning with A Bug’s Life, and they’re still using it today. The GPU that AMD designed for Microsoft’s Xbox 360 gaming console features a tessellation unit, and AMD integrated something similar in its Radeon GPUs for the PC, beginning with the Radeon HD 2000 series. This led many to predict that Microsoft would expose tessellation in DirectX 10. But that didn’t happen, and DirectX 11 won’t be able to tap AMD’s tessellator, either, because AMD’s original implementation of the technology isn’t compatible with Microsoft’s.

GPU’s Grow Up

If you’ve followed the evolution of modern GPUs, you know that they’ve moved from being single-core processors designed for one specific purpose—processing graphics—to massively parallel devices with hundreds of processing cores. Modern GPUs are capable of performing more than a trillion floating-point operations per second, which has been a boon for the types of graphics processing and real-time animation needed for computer gaming. But this hardware can be tapped to perform other types of computations, too; the concept is known as GPGPU computing (the acronym stands for general-purpose graphics processing unit). Most software applications, however, as well as the tools used to develop them, are designed for serial execution, not parallel.

GPGPU computing, therefore, requires brand-new tools, and AMD and Nvidia have invested significant amounts of time and effort to both create them and spur the development of GPGPU applications. AMD’s initiative is known as Stream SDK (Software Development Kit) and Nvidia’s is called CUDA (Compute Unified Device Architecture). The growth of GPGPU computing, however, has been hindered by the fact that each company’s tools work with only that company’s GPU. Microsoft hopes to change that with the addition of the Compute Shader to DirectX 11. The Compute Shader will enable developers to write GPGPU code that will run on any graphics processor, be it Nvidia’s GeForce platform, AMD’s Radeon, or Intel’s upcoming Larabee.

Although the Compute Shader is integrated with DirectX 11, it’s not actually a stage in the Direct3D pipeline. It can, however, take data structures from the Pixel Shader stage, manipulate them using the GPU’s resources, and then apply them to the final image in a post-processing stage. Microsoft has identified a range of target applications specifically related to graphics processing that should improve games, including effects physics (particles, smoke, water, cloth, etc.), ray tracing, gameplay physics, and even AI.

Let’s look at some of the benefits of DirectX 11 vs DirectX 10:

1. Improved Parallelism -

The following features of DirectX 11-enabled GPUs greatly enhance a programmer’s ability to exploit parallelism:
Increased Thread Group Size and 3D Thread Dispatch: A Thread Group is a set of threads that work together to efficiently implement a partitioned data parallel algorithm. DirectX 11-enabled GPUs improve the efficiency of memory accesses by allowing the coherent exchange of data between threads within a group, thus enabling parallel algorithms to execute in fewer passes. This is designed to not only increases processing speed, but to improve power efficiency as well, by allowing higher throughput with fewer accesses to offchip memory. Shader Model 5.0 supports larger and more flexible thread groups with 3D indexing, giving programmers improved control over the domain of defining their algorithms, and enabling additional throughput due to increased multi-threading in the GPU.
Atomic Operation Support: This is a key feature of CPUs that programmers have been demanding for GPUs as well. Atomic operations enable the more efficient and accurate combination of operations that try to modify the same memory addresses. GPUs are capable of running thousands of threads or thread groups in parallel, and if two or more of these threads try to manipulate the same variable or access the same memory location, it could result in data corruption. Without atomic operations, programmers either had to modify their algorithms to avoid these situations, or otherwise serialize updates to shared variables or memory locations (effectively eliminating much of the performance benefit from parallel processing). Atomic operations allow these situations to be handled gracefully regardless of the number of parallel threads being executed, which helps maximize performance and simplify porting of algorithms from the CPU to the GPU.
Gather4: Modern GPUs use dedicated hardware blocks known as texture units to fetch data rapidly into their processing cores. These texture units have historically been optimized for rendering graphics, where techniques such as bilinear filtering are typically used to improve image quality. Compute Shaders often make use of these same units to fetch data as well, but they generally have no use for their filtering capabilities, leaving them underutilized. GPUs with Shader Model 5.0 support have the ability to use the excess fetch capability with the Gather4 operation, which can fetch up to 4 values simultaneously and provide a 4xincrease in data bandwidth.

2. Improved Precision and Integer Processing:

DirectX 11 enables support for double precision (64-bit) floating point operations on the GPU, according to the IEEE-754 standard. Until recently, this level of precision was only supported on CPUs, with GPUs being limited to single precision (32-bit) operations. While single precision is sufficient for most graphics applications, it can be insufficient for some simulation or number-crunching tasks that require large numbers of iterations on a single data value, or work with very large or very small values. Shader Model 5.0 also adds new integer and bit manipulation operations, such as count bits set, find first bit, insert/extract bit fields, reverse bits, and new bit shift operations. Applications such as video processing and cryptography use operations like these extensively, and can therefore benefit from improved performance on DirectX 11 GPUs.

3. Tight Integration between Compute Shaders and Rendering Pipeline:

Although Compute Shaders are primarily intended to handle non-graphics tasks, they can often be used to enhance or interface with a rendering pipeline to influence what is sent to a display. Examples include simulation tasks, like game physics or artificial intelligence, that can control the movement or behavior of objects and characters that are drawn on-screen; sorting techniques, like order independent transparency, that optimize the rendering of large numbers of objects; and postprocessing effects, like tone mapping and depth of field, which can apply various filters to modify and enhance an image after it has finished rendering. DirectX 11 Compute Shaders share a common instruction set with other DirectX 11 shader types used for rendering (including Vertex, Hull, Domain, Geometry, and Pixel Shaders), and can share data structures to implement these techniques in a much more practical and efficient manner.

4. Improved Ease of Programming and more efficient memory usage:

Powerful hardware is useless without software that can take advantage of the hardware’s capabilities. As a compute language, Shader Model 5.0 enables significant improvements that can enhance a programmer’s ability to model programs and algorithms for the GPU that were once impractical or impossible. By liberating development time from working around the restrictions of earlier GPU compute languages, the programmer’s imagination and energies can be focused instead on the actual compute problem. Shaders Model 5.0 adds some key features that make it easier to model and solve compute problems on the GPU, including:
Increased Shared Memory with Improved Access: A key feature of DirectX 11 Compute Shaders is support for shared memory, which allows communication between threads. Shader Model 5.0 doubles the amount of shared memory available to a thread group, from 16 to 32 kilobytes. In addition to more shared memory, DirectX 11 class GPUs allow indexed reads and writes to this memory, whereas older DirectX 10 / 10.1 class GPUs limited access to private writes with shared reads. Allowing threads to directly read and write shared memory increases data parallelism within thread groups and simplifies porting of CPU code to run on the GPU. The combination of larger thread groups and more shared memory can also greatly reduce the number of non-local memory accesses required by some algorithms, which would reduce memory bandwidth requirements and improve performance.

Append/Consume Buffers: Shader Model 5.0 supports a new type of data buffer that behaves like a stack or a list, instead of a fixed array of values. New data values are written to the end of the list as they are generated, or read from the end of the list as they are required. This is useful for implementing irregular data structures that require a different number of data values for each element, or for adaptive techniques like stream compaction that do a variable amount of processing for each element. Append buffers allow these processes to be performed in a single pass over the data, instead of requiring multiple passes which consume more memory bandwidth and compute cycles.

Unordered Access Views (UAV): A UAV is a buffer that allows data to be written to or read from arbitrary locations, instead of a pre-defined order. Also known as “scatter/gather” operations, these add a great deal of flexibility that was not available in older GPUs. DirectX 11 extends this flexibility beyond what was possible with DirectX 10 class GPUs by allowing Compute Shaders to access up to 8 different UAVs at a time instead of just one. The DirectX 11 programming interface allows these UAVs to be accessed by Pixel Shaders as well, which facilitates data sharing between Compute Shaders and the rendering pipeline. These enhancements allow a variety of pre- and post-processing algorithms to be implemented more efficiently with DirectX 11 class GPUs.

Indirect Compute Dispatch: This feature enables the generation of new workloads created by previous rendering or compute shading without CPU intervention. This further reduces CPU overhead and frees up more processing time to be used on other tasks.

I would like to thank AMD, the forums at Beyond3D and Bjorn3D and Michael Brown from Maximum PC for their help.

[uds-billboard name ="My Office"]

The wireless antenna on your router is omni-directional because it is designed to emit the signal in all directions from its location.  That is great in theory.  Raise your hand if you placed your router in the corner or against the wall.  I seen that.  You can increase the range of your router by using aluminum foil.  Yes, aluminum foil.  Mount some aluminum foil on a piece of cardboard or some other material that you can bend into a soft-curved U shape.  Place this behind your antenna on the wall side.  That is it.  It was that easy.  If you are still having issues, then try the next step.  There isn’t any need to spend extra money yet!
If you have the venerable Linksys WRT54(X) or any other Broadcom based router then I recommend using Tomato firmware, but you can use DD-WRT if you like. Because of its support for a wider variety of routers, I will be using DD-WRT in this article. You can check to see if your router is compatable by checking this list.
Once you have determined if your router is compatible, the next step is to download the firmware. You are going to want to go to the downloads page of DD-WRT.com and download the firmware. But wait! you say…you may have noticed that this isn’t exactly the most user-friendly page. How do you know where to click? You are going to want to click on the stable link and then you will scroll down to the latest version of the firmware (dd-wrt.v24 as of this writing). The next step is to determine which version you want. Consult the list (if you haven’t already) and determine what chip is in your exact router. Then select your router make, followed by its model number and simply download the correct firmware.

It is important to check the list again, because the process of flashing the firmware varies among the different routers. The page should have the instructions on the under Additional Information with the name of your router, followed by a Wiki. I will go through the process for a Linksys router that I used to have just so you get an idea of how it will work.

Step 1: Reset router to its default settings and then reboot the router
Step 2: Go to the admin page (192.168.1.1 in your address bar of your browser) and go to the firmware page. Browse to your downloaded firmware (it will be a .bin file) and click the upgrade page. Wait for a minute or so and it should reboot on its own. If it doesn’t, simply unplug it for 30 seconds and plug it back in again.
Step 3: Confirm it worked by logging into your admin page again.

Once you are in your routers settings, look for the transmit power option, and crank it up from 10-25 up to the 60-80 range.  Don’t go any higher or your router will overheat and shut itself off all of the time.

Bonus Tip:

Place your router up high, in a central location if possible – and away from anything that is metallic.

Things to do if you still aren’t getting a signal:

If you still aren’t getting a decent signal, you are going to have to spend some money sadly.  Make sure that you are using a Wireless N router and that the wireless devices that you have are using N.  Just because your router is N, doesn’t mean that you will be getting the benefits of N.  In fact, in one of the biggest gotchas out there, if even one Wireless B or G device connects to your network, then the entire thing reverts down to those older and slower standards, thus giving you less range in the process.  If you have an older device that uses B or G, consider picking up an N adapter to remedy the situation.

You can pick up a wireless repeater (stick with the same manufacturer as your router – it shouldn’t matter, but it kinda does) and place it just inside of where your signal starts to get slow.

You can also change your wireless channel, as there may be congestion from your neighbors.  Wireless routers can broadcast on several different channels, similar to the way radio stations use different channels. In the United States and Canada, these channels are 1, 6, and 11. Just as you’ll sometimes hear interference on one radio station while another is perfectly clear, sometimes one wireless channel is clearer than others. Try changing your wireless router’s channel through your router’s configuration page to see if your signal strength improves. You don’t need to change your computer’s configuration, because it can automatically detect the new channel.

Reference:

Router

3Com

http://192.168.1.1

D-Link

http://192.168.0.1

Linksys

http://192.168.1.1

Microsoft Broadband

http://192.168.2.1

Netgear

http://192.168.0.1

Actiontec

http://192.168.0.1

Since I know that you have a computer, lets begin there shall we? Its important to clean your computer, because dust and dirt can harm it and shorten its lifespan. You are going to need the following:

• A can of compressed air
•  Some water (preferably distilled, but that may be me taking it too far…)
•  A microfiber cloth (or a piece of soft cotton will do in a pinch)

Computer

Your computer has fans in it that are constantly moving. They are designed to keep air flowing through your computer to keep your components cool, but as you are about to find out, dust accumulates - en masse – inside your PC. It is a good idea to clean the inside of your computer about once every four months, and no less than once every six months. To clean your computer, grab your compressed air, a small vacuum, and a screwdriver to open your case if necessary.
 Once your computer is open, you are going to want to use the can of compressed air to blow off all the dust from your PC’s components. Make sure to get all of the fans really well as well as the heatsinks and corners of the case.
 Notice something? Did the compressed air just blow the dust around? Yep, but it did clean your fans and heatsinks didn’t it? What you want to do now is vacuum up all of that dust. If you have a horsehair attachment for your vacuum, now is the time to use it.  Be careful not to physically touch any of the components. If you still have some dust that you can’t get rid of, then take a very small amount of rubbing alcohol on a soft cloth and VERY GENTLY dab or wipe the dust away.
 If you are a real geek, then remove any of your cards that have their own cooler (such as a graphics card) and clean that by blowing all of the dust out of its fan/heatsink combo. Once it is clean, go ahead and replace the card.
 That is it. You have now cleaned the inside of your computer. Go ahead and put it back together. Let’s clean the outside shall we? This is quite easy, and you can work it into your normal routine of household cleaning. Simply take some Formula 409 (or equivalent) and a soft cloth and wipe down all the sides of your case. Clean near your power and reset buttons and pay attention to your CD/DVD tray as well. Leave all of the ports on the back of your computer alone.

Gadgets

I have been using a PDA since the Palm III, and I am hopelessly addicted to my smartphones. The downside to all of this is that these touchscreen LCD displays get dirty. Real dirty. How do you clean them? If you answered that you use your shirt, then you need to stop. The best thing to do is go to Walmart and grab an eyeglass cleaning kit. They are $1.97 and include a microfiber cloth and some cleaning solution. When you clean your screen, NEVER spray directly onto the screen. Spray a small bit onto the cloth and then clean your screen. This is the method that you want to use on every device from your cellphone to your mp3 player to your portable gaming system.

BONUS TIP:  If you can, grab a Zagg Invisible shield for your gadget.  They are amazing.  The screens on my smartphones, Zunes, and iPad look like new despite the fact that I take no precautions to protect them.  (I to this because of the Invisible Shield).

Peripherals

Do you know what one of the dirtiest things in your house is? Odds are you just touched it. Your keyboard and mouse are filthy. Don’t worry, mine are too. In fact, mine is probably worse since I am pretty sure I live at my computer. Let’s clean them up a bit shall we?
 Let’s start at the mouse. Simply take a small amount of cleaner and spray it on a microfiber or soft cloth and wipe down all the surfaces of your mouse. If you want to be really anal about your cleaning, dip a Q-tip into rubbing alcohol and clean the hole for your laser or optical sensor.
 To clean our keyboards, we will follow a similar process to cleaning your mouse. Dab some cleaning solution on a soft cloth and wipe down the surface of your keys. Its that simple. Or is it? Do you have dirt and crumbs in your keyboard? I bet you do! If that is the case, I have some bad news for you and some kinda bad news for you. It used to be easy to pop off your keys with a screwdriver and clean out the inside that way, but on many modern high-tech keyboards not only is it really difficult, it also voids the warranty.
 Best tip: Leave the crumbs, and stop eating at the keyboard.
 Bonus tip: This may sound crazy but it actually works. I recommend this only for aspiring geeks however. You can actually place your keyboard in the dishwasher! Place your keyboard in the dishwasher, but make sure not to use detergent!!! After it is clean, you MUST, I repeat you MUST not plug it in for at least one week. If you can wait two weeks that is even better. After you wait, go ahead and plug in your clean and fresh keyboard!

Flat Screen Monitor (LCD and Plasma TV’s as well)

Take your can of compressed air and blow all of the dust off of your screen. Then take a microfiber cloth and wipe off any remaining dust. These screens have a coating on them that Windex and other cleaners will remove, so its important NOT to use any sort of cleaner on them. Take some distilled water and dampen your cloth. Now all you have to do is clean away those fingerprints and smudges. Make sure not to use too much liquid as you don’t want any dripping down into the insides of the scree.

Well, that is it. All of your tech gear is now clean! Not only will it look better, but it will last longer as well! I recommend that you take a shower yourself, make a nice dinner, and hug your favorite Geek! We like that.