Hubs, Repeaters, Bridges, Switches, Routers and Gateways

I have always wanted to do this. What better way to do this than when I am studying Computer Networks. Knowledge courtesy: Computer Networks by Tanenbaum.

Application Layer : Application Gateway
Transport Layer : Transport Gateway
Network Layer : Router
Data Link Layer : Bridge, Switch
Physical Layer : Repeater, Hub

Repeaters: Just amplify volts.
Hubs: Can connect many entities. Frames arriving from any one is sent out on all others.
Bridges: Bridges are used to connect LANs. They connect 2 ethernets. They do not examine packets. So they can transport any type of payloads - IPv4, IPv6, AppleTalk, ATM, OSI or any other kind. A bridge can have line cards for different network types and different speeds.
Switches: Switches also route on frame addresses. Swich is almost like a multi-port Bridge. However switches often are used to connect individual computers. Switches do not broadcast like hubs.
Routers: Examine addresses in packets and route based on them.

This tablet looks cool!

Nokia N800.. http://www.nseries.com/n800. Priced at $399. Cool device.

Testing Windows Live Writer

Trying Windows Live Writer since w.bloggar isn't working too well with Blogger Beta. Nothing wrong with w.bloggar.. just hoping the broken Blogger Beta might work with this Live Writer!

My Firefox plugins

Here is a list of addons I use for my Firefox:

• Live HTTP Headers: Can't live without this one
  
• Google Toolbar
  
• Web Developer
  
• DOM Inspector
  
• InspectThis
  
• JSView
  
• Map This: Excellent integration with Google Maps (allows you to select multiline addresses!)
  
• FoxyProxy: Allows you to configure many proxies and switch between proxies easily from the status bar!
  
• lori: Life-Of-Request-Info.. nifty.. shows time to first byte, response times, etc.
  
• ViewSourceWith: View source with say TextPad
  

Video Editing, Conversion, Storage and more

VHS Copy Protection:

To prevent unauthorized copying of prerecorded VHS tapes (especially Disney), Macrovision came up with this scheme of copy protection. Came into existence in 1986. When a Macrovision-enabled VHS is played back, it looks normal. However, when you try to copy it using 2 back-to-back VCRs, the electronic pulses added by Macrovision in the non-visible part of the VHS tape (vertical blanking interval) make the copying VCR think that the signals are too strong. So the copying VCR tries to weaken the signals which basically rolls the picture, loses color or brightness randomly or suffer from flashing.

Ways to prevent this:

• Use a very old pre-macrovision VCR
• Use a RCA RF Modulator
• Buy special hardware like GoDVD (there are several out there to remove this copy protection)

Macrovision is an analog copy protection and hence there is no software solution to get rid of it.

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VCD/SVCD

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DVD (DVD-R,DVD-RW,DVD+R,DVD+RW,DVD-RAM)

DVD-ROM Drive: Means a read-only drive where you can play your DVDs.

DVD+R/DVD+RW:
Alliance: Dell, HP, Verbatim, Philips, Ricoh, Sony, Yamaha, Thomson

Links:
http://www.DVDPlusRW.org
http://www.dvdrw.com

DVD+R DL is the double layer DVD+R that can fit upto 4 hours of high quality video. This format is also widely supported in all DVD players. The capacity is whopping 8.5GB!!

DVD-R/DVD-RW: Has a slighly more compatibility percentage that the plus alliance.
Alliance: Pioneer, TDK

Links:
http://www.dvdforum.org

DVD-RAM: Less compatible with DVD Players/ROMs
Writable DVD but works as a virtual hard drive. Random RW access (unlike DVD-RW which is sequential)
Alliance: Panasonic, Toshiba, Hitachi

Links:
http://www.dvdforum.org

MiniDVD/cDVD: Like a mini-CD.

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DVD Regions:

DVDs come in PAL/NTSC formats and they also have an additional thing called the Region code. Motion picture studios in USA release the movie DVDs all over the world. In order to prevent unauthorised export of DVDs which get released in USA before the rest of the world, they introduced the region codes. A DVD released in one region does not play in DVD Players in some other region.

There are 6 regions defined as follows:

Graphics courtesy: Sony

• Region 1 - The U.S., U.S. territories and Canada
• Region 2 - Europe, Japan, the Middle East, Egypt, South Africa, Greenland
• Region 3 - Taiwan, Korea, the Philippines, Indonesia, Hong Kong
• Region 4 - Mexico, South America, Central America, Australia, New Zealand, Pacific Islands, Caribbean
• Region 5 - Russia (okay, former Russia), Eastern Europe, India, most of Africa, North Korea, Mongolia
• Region 6 - China

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NTSC/PAL Formats, Conversion and Multisystem TV/VCRs

Courtesy: Wikipedia
Legend: Yellow: PAL, Green: NTSC, Orange: SECAM

Two main differences:

1. PAL has better resolution
2. NTSC is a higher framerate (29.97 fps vs 25 fps for PAL) so less flicker

(Blank) VHS cassettes by themselves do not have any format attached to them. It is when you record video on them that they get that assigned to them.

A NTSC cassette usually works fine in PAL systems but not vice versa.

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Solutions:

• VHS to DVD/VCD
• Audio Cassettes to CDs
• Analog camcorder to Digital MiniDV/other media
• PAL to NTSC

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Television Types

• CRT
• Projection TV
• Flat Screen

audio post powered by audblog

Customizing your machine and getting rid of OEM specific crap!

1. The Boot logo:
Replace the C:\logo.sys

2. OEM Logo in My Computer Properties:
Your infos and logo are stored under these files: c:\windows\system\oeminfo.ini and c:\windows\system\oemlogo.bmp.
If don't need them, simply delete these files.

3. IE Logo in the top right corner of the browser:
This is a 22x22 icon.
98/ME: Change or simply keep the HKEY_LOCAL_MACHINE\Software\Microsoft\InternetExplorer/Toolbar/SmallBitmap, SmBrandBitmap, BrandBitmap values blank.

4. IE Title will have the OEM name in it:
Check HKEY_LOCAL_MACHINE\Software\Microsoft\InternetExplorer\Main and HKEY_CURRENT_USER\Software\Microsoft\InternetExplorer\Main.
Change "Window Title" value here.

Change 'BigBitmap' value here

XP: Run gpedit.msc

What is HDTV?

HDTV is the broadcast format of the future-and of the present. More and more stations have been upgrading from NTSC to 16:9 HDTV. HDTV broadcasts will be in 16:9 formatting.

There are two types of high-definition televisions:
1. HDTV: Also known as high-definition TV. These have a built-in high-definition receiver that allows the TV to receive over-the-air high-definition broadcasts. These TVs require either an indoor or an outdoor antenna to receive high-definition over-the-air broadcasts (such as CBS or NBC).
2. HDTV Monitors: These are capable of displaying a high-definition TV signal, but require the separate purchase of a high-definition receiver and antenna to receive high-definition broadcasts.

Basically they still fall under the "Rear Projection TV" category - which means the projection cathode ray tubes, commonly known as CRTs, are found within the set and behind a plastic projection screen. The light from the CRTs strikes a mirror and is reflected onto the rear of the screen, where it forms an image you can see on the other side. Instead of the traditional direct view TVs you're used to, where you view the picture directly on a single tube, rear projection TVs use CRTs, a series of focusing lenses, a mirror, and a display screen.

The screens on the TVs most of us are still watching today (referred to these days as "analog" or "traditional") are roughly square and have an "aspect ratio" of 4:3. That is, they're just slightly wider than they are tall. But widescreen HDTVs have an aspect ratio of 16:9. As you can see, they're much wider than they are tall. So, what's the advantage? We thought you'd never ask.

Movies shown at a theater have pictures that are wider than your TV's screen. By the time a movie is released on video tape or shown on TV it has been "modified to fit your screen." Unfortunately, they "modify" it by chopping off the sides of the picture. Widescreen TVs use the entire TV screen to let you see the whole picture.

The resolution for traditional TVs is of the order of 200,000 pixels whereas for HDTV it is ~2 Million. There were several resolution standards that were approved by FCC in 1996 and the most popular ones are 480i (regular analog TV), 480p, 720p and 1080i. The number is number of horizontal lines and how they are drawn (i-nterlace scanning or p-rogressive scan). The traditional TVs actually use 525 lines but some of these lines are used for things other than picture and the number is close to 480 and hence the name 480i instead of 525i. Interlacing means constructing the picture using odd-even lines and Progressive (which is only found in HDTV and HDTV Monitors since only digital broadcasts and digital sources like DVD players send the signal this way) is like computer monitors - from top to bottom in the order of lines.

The audio is CD quality sound as compared to analog sound which is like FM Radio. It supports Dolby® Digital sound that can recreate surround sound effects from five different speakers with the right kind of home theater equipment.

Source: Circuit City Knowledge base

How to CAPTCHA?

Web forms are vulnerable to abuse. An automated agent can create hundreds of logins. Some web services like Yahoo! have implemented a new way to stop this. A dynamically generated image (with some obfuscation) is shown and the user enters the text as he sees it in a form text item. This is validated every time an account gets created. These images are not easily recognizable by a computer program that may maliciously try to simulate a human requesting a userid.

Try ImageMagick at http://www.imagemagick.com. This is a set of open source libraries in C, Perl, Java, PHP, VB and other languages which can be run as a CGI script as /make_image?key.

Hosting PFR Fonts and required software from Bitstream:

Host the WebFont Player on your server. The Javascript file you link on the first html page of your site lets the users download this player. This player is installed in Windows dir / Downloaded Program Files folder -> TDServer Control. It can be removed by right clicking on this file and choosing Remove from the menu.

And there was the w.Bloggar

This is a trial post to my tech blog from w.bloggar.
This thing is cool! Go to http://www.wbloggar.com and download this desktop tool to update your blog

Yahoo! Messenger IMVironment

Yahoo! Messenger IMVironment doesn't work!
If you install the messenger alone, IMVs do not work. You have to install Messenger with Extras (Yahoo! Companion, etc) to make these work.

How to Add a Shortcut Icon to a Web Page?

Creating a Shortcut Icon for a Web Page

The required size of a shortcut icon is 16x16 pixels. Use the following HTML code to enable this:

<HEAD>
<LINK REL="SHORTCUT ICON" HREF="http://www.mydomain.com/myicon.ico">
</HEAD>

The only way a shortcut icon appears on a user's Favorites menu and Address bar is if the user chooses to add your page as a favorite.

This is how you can add a button or a link that prompts user to add your page to favorites. Use the following Javascript code:

<SCRIPT>
<!--
if ((navigator.appVersion.indexOf("MSIE") > 0)
&& (parseInt(navigator.appVersion) >= 4)) {
var sText = "<u><span style='color:blue;cursor:hand;'";
sText += "onclick='window.external.AddFavorite(location.href,";
sText += "document.title);'>Add this page to your favorites</span></u>";
document.write(sText);
}
//-->
</SCRIPT>


Fix for DSL Stall

These instructions are for PPPoE software users only. If you have DHCP or PPPoE through a router this can make things much worse. If your computer has to logon to access the internet ands you notice delays/freezes/stalls while the OS boots up or when browsing or at seemingly random times. The following will likely cure it:

1. Open Control Panel.
   
2. Open Network.
   
3. Look for the first entry in the scroll box marked TCP/IP, that is associated with a hardware ethernet card (ignore dialup, especially Enternet or NTS and VPN type bindings). Note: If you have a 4060 USB modem, select TCP/IP-> Efficient Networks SpeedStream 4060 CIP/1483
   
4. Select it and press properties
   
5. Select IP address from the tab
   Is Obtain IP address automatically checked? If so, change that to Specify an IP address and enter 192.168.1.10, and 255.255.255.0, into IP address and subnet mask fields respectively.
   
6. Click OK and OK, and the computer will build a driver information database and will require a reboot for the changes to take effect.
   

This assignment of a harmless local IP address to the TCP/IP settings bound (connected) to your network adapter, will stop the in-built DHCP services from waking up every 10 minutes to look for a DHCP server so that it can "fill in the blanks".

Enabling Autocomplete for Web forms on XP

In XP, a user login belonging to the Administrator group can not use the "Enable Autocomplete feature for Web Forms" feature.

Microsoft Visual Keyboard

Office 2000 Microsoft Visual Keyboard: "Microsoft Visual Keyboard is a program that supports typing in more than one language on the same computer by showing you a keyboard for another language on your screen."

Microsoft JVM

If you have a new XP machine and you can not view Java applets in Internet Explorer it is probably because it did not come with Microsoft JVM due the legal tussle between Sun and Microsoft. It will prompt you download Microsoft JVM and will tell you to go to Windows Update site. That will not work either. Because Microsoft no longer provides JVM with XP.

No worries.. download a JVM from Sun instead - the makers of Java!
Get it here..

GNOME Desktop for Solaris

Use GNOME desktop on Solaris.
Get it here. It is much better than the CDE!

AIM on Solaris

Use GaIM to use AIM on Solaris!
Get it from sourceforge.net..

WebDAV

Refer to the link below for reference:
WebDAV: mod_dav Installation and Configuration

New Book on Resin

A new book on resin coming up: "Mastering Resin" - Publish date May 2003

Apache htaccess

Apache htaccess files can only be applied to folders and not to individual documents.

WebDAV for apache can be enabled using mod_dav.so module.