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Monday, October 15, 2007

Palm Centro review



Okay, now we know what you're thinking. Sure, we (lovingly) raked Palm over the coals in our open letter to the company, and yeah, we haven't been the sweetest of hearts to the crew from Sunnyvale (with good reason, of course). However, If you've paid attention to our past good-intentioned prodding, then you'll know that getting our hands on a new Palm device still gives some of us geeky chills.

After seeing scores of "leaked" photos of the Centro, and hearing enough internet chatter about the device to make your brain vibrate like a tightly-wound piano string, actually getting our hands on the phone was honestly a bit of a surprise, both bad and good. We're going to break it down piece by piece and hopefully give you a rounded impression of the smartphone crown-chaser (or at least princess-in-waiting).

The design

First off, let's get a few basics out of the way. Yes, the phone is considerably smaller than past Treo devices. Having used a 650, 680, and 750, we can honestly say there is a massive difference between holding this phone in your hands and holding any other Palm device. Is this a good thing? For the most part, yes, though there are drawbacks to its diminutive size, which we'll get to in a moment. But for now, let's talk aesthetics.

The Centro has a rounded, symmetrical design that works without being especially fussy or impressive. We would have liked to see Palm put the real estate to better use with a larger screen and less plastic, but this is certainly a step in the right direction for the company... though a few more steps would have gone a long way.






The major difference beyond the overall width and length is the thickness. The phone is thin, though not as lean as the BlackJack, Q, iPhone, or Pearl (which it most closely relates to in terms of size). No, the fact is this: amongst all of these phones, the Centro is still the fattest, though we couldn't tell you why.





The phone comes in two glossy colors, a cherry red and metallic black (it's actually got silver flecks in it). They're attractive enough, but we continue to take fault with Palm over the gray stripe -- it makes the phone look like a Sony Ericsson from 1999 2001, and serves no purpose as far as we can tell. When Helio designed the Ocean, they used a silver line splitting the sides to create a slimming effect, and if we didn't know better, we'd say that's the impetus for this out-of-place touch.






The screen is a miniature 2-inches, though it looks fantastic at its 320 x 320 resolution and fairly high pixel density. It's impressive for its size, and certainly easy on your eyeballs. We'd again like to congratulate Palm on overcoming the 2-pixel white border surrounding the screen which has plagued the company's devices for as long as we can remember. Kudos.





We know the keyboard is on your mind, so here's the deal: it isn't that great, but it isn't a deal breaker. The phone is designed with the youth market (and women, from what we can tell) in mind, and if that's the case, they should be happy with the full QWERTY of the Centro. The jelly-ish buttons aren't exactly a joyride for us to press, though we've got massive, bear-like claws. The keyboard works; certainly better than T9, and definitely better than no keyboard at all. Still, you'll find yourself backtracking plenty when your nail hits a key next to the letter you meant to press.





The buttons on the "gray stripe" are more standard Treo fare, though their tactile feel on this phone is nonexistent, and we found ourselves re-pressing them constantly. They're too flush, and frankly too big for the purpose they serve. The 4-way rocker is good, however, and should be plenty responsive for anything you'll need it for. This is a good time to nitpick Palm on a design change they made a while back that really rears its ugly head here -- the movement of the "menu" button to the lower right hand corner of the keyboard. Sorry guys, you have to get to drop-down menus too often for it to be relegated to this useless and hard-to-reach corner. Fix please.





Another flaw which Palm's designers don't seem to get is the sunken screen. Look, do you even use your devices? It's a nerve-rattling pain to try and tap the sides of the touchscreen when you've got it buried seemingly four-inches-deep in the phone. The screen needs to be flush with the surface, or near-to -- this is a maddening and obvious problem which the Centro does nothing to correct. In fact, it seems to be amplified here.






Other than that there are no design surprises. All of the side buttons, sound on / off switch, awkward HotSync port, and 2.5mm headphone jack are in exactly the same place as every other Treo.

The OS

You'd think there wasn't much to say here that hasn't already been said, and you would be mostly correct. We won't bore you by detailing our complaints about Palm's aging (aged, rather) OS, but we will point out a few items of interest.





Firstly, this reviewer, having switched to the 750 and its Windows Mobile interface, had quite a shock returning to the Palm OS. We forgot how fast and responsive it can be, and it was a reminder of why we liked Palm to begin with. We know that WM has a lot more bells and whistles, Symbian is kept current, and the iPhone's OS X iteration is fancy as all get-out, but Palm still shines in a lot of ways. The system is fast, has very low loading times for applications, and makes getting most tasks done crushingly simple.






Of course, you know the trade-offs. This is not current software, and it shows. Palm has gone to the trouble of updating the look and functionality of some apps, like the camera and PTunes, yet most remain staid and ancient in appearance. We don't get it -- why not just give the OS a paint job if you can't rebuild it? Our minds are still boggled by the fact that Palm can't even fix the anti-aliasing on highlighted icons. Call us Ed, we know anxious teenagers just dying to skin your UI.





The company has added a few new apps as they've gone along, bundling the aforementioned PTunes, plus Google Maps, as well as a new IM app, On Demand (a kind of one-stop portal), and of course Sprint TV.





Speaking of, Sprint TV is a nice addition, giving you a pretty wide range of channels to view, with solid EV-DO connections -- though the resolution leaves something to be desired.





The IM app is also a plus, with a simple and straightforward interface that doesn't require much time to get comfortable with.

They also include DataViz's DocumentsToGo, a PDF / Word / Excel editor, but you're still stuck with Blazer for web duties, and the rest of Palm's vintage fare for general tasks. It works... but, bleh.

The phone

What can we say? The phone is good, and the sound quality is solid. Palm equipped the Centro with a nice loud earpiece and speaker, and both do their job admirably. One problem of note is that if you lay this phone on its back during a speakerphone call, you lose about 50-percent of your sound. The effect is almost akin to sweeping a resonant filter down on the signal, like the "underwater" effect you hear in your favorite rave anthems. Point being: keep it on its face (hey, you won't have to worry about scratching that screen!).






The 1.3-megapixel camera is nothing to write home about -- in fact, it's terrifically mediocre. The performance on the camera and camcorder apps is also sluggish to the point of annoyance, but we've learned to not expect too much in this department.

Little details -- like the prompt to add a number you've dialed that isn't stored in your contacts, and the "avoid with SMS" feature for incoming calls -- are Palm hallmarks that still feel plenty helpful.

Wrap-up

The real selling point on this device for a lot of people has been its much-touted $99 price point. Of course, you have to keep in mind that the figure takes into account an "instant discount, mail-in rebate, and qualifying two-year Sprint service agreement." Which means the phone isn't nearly as cheap as it sounds. That said, the fact the offer is on the table is a great move for Palm, and should help push a lot of these out the door.

It would be easy to love this phone, but there are too many minor hang-ups that contribute to an overwhelming sense of letdown. Nostalgic affection aside, it doesn't feel like Palm is taking advantage of the opportunities it has right now. Things like its complicated syncing process (particularly with Macs) don't jive with Palm's bid for the "youth market," who undoubtedly are interested in iTunes-like simplicity

Still, brainy teens, casual tinkerers, and young technophiles of all suits will probably be stoked on the wide variety of options for the money. Power users, early adopters, and those seriously jaded by Palm's inability to really deliver something new might want to look elsewhere.

Hitachi breakthrough: 4TB disks by 2011

When Hitachi -- the first disk manufacturer to go perpendicular and subsequently break the 1TB consumer disk drive barrier -- speaks about advances in hard disk technology, you'd be wise to listen. Today they're touting the world's smallest read-head technology for HDDs. The bold claim? 4TB desktop (3.5-inch) and 1TB laptop (2.5-inch) drives within the next 4 years. The new recording heads are more than 2x smaller than existing gear or about 2,000 times smaller than a human hair. Hmmm, Samsung may have to update their SSD vs. HDD graph after this, eh?

Lumenlab shoves PC inside 42-inch 1080p display, calls it Q



There's all-in-one PCs, and then there's the Q. This behemoth sports a unique identity crisis, as it attempts to pose as an aluminum-framed HDTV while featuring a full-fledged computer within. Nevertheless, the 42-inch Q packs a 1080p panel, compatibility with the Lumenlab's own Hotwire PnP powerline networking technology, a fanless design, 1TB of HDD storage, 2GB of RAM and an Intel Core Duo processor. Unfortunately, details beyond that are fairly slim, but we should get a better idea of specifications and pricing when its ship date draws closer.

K850 all set for release

The greatest camera phone you'll ever own gets official. And ours has just arrived.








The new K850 is official and good to go. [more images]




Sony Ericsson has upped its game again. We've just taken delivery of our K850 and it really is one of the best camera phones we've ever got hold of.


The new cell, which Sony today confirmed would be in stores this month, packs so many features, it's obscene.


The 5-meg snapper, which matches the N95 and G600, is a winner, with auto focus, a Xenon flash and Photo Fix to improve light balance.


Best of all, the lens is properly protected, with the cap sitting inside the body. So no accidentally opening it in your pocket, a la every top notch camera phone on the market.



It's incredibly small too, and still manages to add HSDPA and video at 30 fps. Tasty.


Keep your eyes glued right here for a full gallery and video tomorrow.


Old iPods get new features

Apple’s not bringing its new iPod interface to old models. So hackers have instead!







Take one iPod, add a pinch of new menus, save a fortune on a new model!... [more images]




There’s a good chance you’re disappointed by the new iPods. Not because they’re anything short of brilliant, but because yours now looks a bit dated next to the new interface.


Fear not, however! Intrepid hackers have brought Apple’s shiny new menus to older models, proving you can indeed teach an old ‘Pod new tricks.


You should be warned that the process involves modifying your iPod’s firmware – something that’ll almost certainly void what warranty you’ve got left.



Still, it beats shelling out for a new iPod if there’s still plenty of life in your current model. Head here to download the modified firmware. Happy hacking!


10 Valuable Tips for Creating Your Web Site

Introduction

When looking for ways to build of your web site, even minor steps can make a huge difference. The most helpful information and best content will have little impact without simple protocols that make your Web site easier to use and more visually appealing. This paper focuses on 10 tips you can employ to ensure your web site is effec- tive from the day it goes live.

1. Accessibility

Web site accessibility has recently become a very important issue in the web community. Because of Section 508 of the Rehabilitation Act of 1973, all web sites and pages created by Federal agencies and Federal contrac-tors after June 21, 2001 must comply with its provisions. The purpose of the law is to make web sites accessi-ble to all individuals, including those with disabilities. The World Wide Web Consortium (W3C) developed Web
Content Accessibility Guidelines (May 1999), which expand the scope of Section 508.

This is very important to all web developers, whether you are a government agency, a contractor who does work for the government, or a private firm with its own web site. An accessible web site refers to any content or information provided via an online medium that all individuals (including those with disabilities) could easily access and understand. Disabilities include not only visual impairments, but auditory, cognitive, and physical
impairments as well. They can range from very severe (total blindness, for example) to something as simple as the increasing inability to see contrasts that develop as we age. Greater accessibility means more people can fully utilize your web site’s features.

There are a number of aids available for enhancing accessibility. These range from programs like Jaws or IBM’s Home Page Reader—which read the page aloud for the visually impaired—to sip-and-puff systems for the quadriplegic. It is up to the web developer to create pages that allow these systems to provide an equivalent alternative for these individuals. Think of accessing a web page as being similar to a play or opera. If you read the script without benefit of the actors’ interpretation, lights, scenery, or music, you are only experiencing one aspect of the author’s intent. The same is true of web access: if you can only hear the words being read, for example, with no description of the images on the page or other visual components, you would not fully expe-rience the information being provided on the page. That is why, when we include an image, it is important to use the “alt” attribute to provide a description of the image. This enables a screen reader to read this informa-
tion aloud for a visually impaired user.

There are several other tips like using table headers with tables of information, not just placeholders. Be careful of using the colors red and green together because of red/green colorblindness. Use sounds with care. Not everyone can hear, nor does everyone have speakers set up on their computers.

So how do you know if your web site is accessible? Go to http://webxact.watchfire.com and enter the URL for a web page. This free application will test your page and let you know where it does not comply

2. Security

Security is crucial to the success of your web site. There are several steps you can take to minimize the risk that your web sites will be subjected to a breech in security.

Security Updates
Be sure you are running the most current version of your web Server. Monitor your vendor updates, and per-form regular maintenance.

Validate User Input on the Client and the Server
Validating user input on the client is great for user experience. However, you need to validate input on the server side as well. Consider that there are tools that look and feel to your sever like a web site when in fact they are actually designed to fake input such as passwords.

Audit Logs
Maintain and review server logs to check for suspicious activity.

Common Settings
Be sure to minimize the risk to your server by minimizing the things users can do on your server. For example, don’t permit users to browse the directory structure of your site unless it’s necessary.

Lockdown Your Server
Most servers have standard development mode and then a production mode. For example, Microsoft’s Internet Information Server (IIS) has a lockdown utility that minimizes the attack surface for your web site.

3.Web Server Statistics

How many visitors do you have? What pages do they frequent? What times do they log on? Utilize a web tool to assist you in not only collecting these statistics but also analyzing and correlating them. Web tools, such as Web Trends, will aid you in collecting and utilizing this knowledge to answer these questions about your site. Build a web page that not only follows appropriate standards, but also drives repeat visitations.

4. Dynamic Technologies Styles
Are the pages within your site beginning to feel and act a little plain? Would you like more ways to format your documents and give users more interaction with them? If so, then your site could make use of languages such as Cascading Style Sheets and JavaScript.

Cascading Style Sheets (CSS) technology gives you more control of page layout and the ability to control the design of multiple pages on your site from a single file. Additionally, CSS allows you to develop more sophisticat- ed layouts, more font schemes, and even more interactivity for your pages than was possible using just HTML.

JavaScript techniques are needed to develop cutting-edge, interactive web sites. From opening windows to image-flipping and form validation, Javascript can help you build exciting, dynamic web pages.

Integrating HTML, JavaScript, and Cascading Style Sheets techniques are collectively known as Dynamic HTML or DOM Scripting. Utilizing all three languages allow you to fully exploit the capabilities of Netscape Communicator, Firefox, and Microsoft Internet Explorer.

5. Efficient Use of Appropriate Design Software

In the past, many web developers eschewed graphical web editing packages and boasted of developing pages using a simple text editor (for example, Notepad). There is still a place for text editors, but efficient designers and developers both use appropriate design software, often manually tweaking the code. Such packages offer a what- you-see-is-what-you-get (WYSIWYG) environment for designers and code-writing tools for developers. These have
the software-complete repetitive steps, and let designers and developers focus on what they do best.

There are many options, but here are some of the major ones:
Dreamweaver (Adobe, formerly Macromedia)
• The most popular package
• Offers both design (layout) and development (programming) support
• Supports all major server-side scripting languages (ColdFusion, ASP, PHP, JSP), Javascript, XML, and

ASP.NET (VB.NET and C#)
• Integrates well with Adobe Flash and Adobe Fireworks (both formerly Macromedia)

GoLive (Adobe)
• Offers both design (layout) and development (programming) support
• Supports several scripting and markup languages (PHP, JavaScript, SVG-t, SMIL)
• Integrates well with long-standing Adobe products (Photoshop, Illustrator, InDesign)

FrontPage (Microsoft)
• Offers both design (layout) and development (programming) support
• Supports Microsoft JScript and ASP.NET (VB.NET and C#)
• Integrates well with Visual Studio .NET and the Microsoft Office Suite

Microsoft Visual Studio (Microsoft)
• Primarily provides development (programming) support
• Integrated Design Environment (IDE) for developing in .NET environment
• Supports .NET languages (primarily VB.NET and C#, but other extensions for other
languages provided by third parties)

Eclipse (open source)

• Primarily provides development (programming) support
• Integrated Design Environment (IDE) for developing in any environment, but mostly
ommonly used for J2EE
• Supports a multitude of programming languages (not language-specific).


6. Standards and Browser Independence

Web site development has come a long way. There are lots of new tools that will help with web-page design, not to mention web sites that offer suggestions and ideas for making your web site absolutely incredible. Probably the biggest movement is the increasing use of Cascading Style sheets to separate page content from formatting. We are also seeing more sophisticated use of JavaScript to make pages more dynamic and, therefore, more interesting. Along with this, the World Wide Web Consortium (W3C) has instituted an effort to standardize how browsers handle the display of web pages through the use of XHTML. It is hoped that among all of these initiatives, programming for the web will become less a matter of making sure our pages work on all browsers by testing against each one, and more one of creating web pages that are useful, accessible, and exciting.

There are a vast number of resources on the web to help improve web sites. For information about the new XHTML standards, as well as help with Cascading Style Sheets and DOM Scripting (using JavaScript to make your web pages more dynamic), the W3C pages (http://www.w3.org) are invaluable. They include examples and tutorials, both of which are very well done. For some wonderful examples of Cascading Style Sheets, we recommend CSSZenGarden.com (http://www.csszengarden.com). The organization that runs this site supplies an html page with the required content. Designers are invited to create an external style sheet to format the page. New contributions are regularly posted.

Another excellent resource is http://www.dynamicdrive.com. The Internet group on Google groups, formerly Deja, http://groups.google.com/groups is helpful as well. The good news is that you can post a question through Deja/Google groups. Within 24 hours you will usually get one-to-three technically correct answers. Other potential resources include:

http://www.developer.com
This is a solid resource for most scripting/programming languages and is top-notch for Java.
http://www.codehound.com
This is another language resource and is especially helpful with Microsoft .NET technologies.
http://www.4GuysFromRolla.com
This is the definitive place to get ASP or ASP.NET information.
http://www.php.net A good resource for php.
http://www.news.com CNET news.
This site keeps you up-to-date on IT news.
http://www.theinquirer.net
This site provides a hardware outlook for six months to a year-and-a half.

7. Database Access with Server-side Scripting Languages

Static web pages are good place to start, but they quickly can become time intensive and not an efficient use of a designer or developer’s time. Database-driven web sites can refresh their own data, presenting up-to-the- minute data in way manual updates could never do. A dozen or so programmed pages can dynamically change so that they do the job of thousands of static pages. The benefits are clear: more timely information; fewer pages to maintain; and a freeing up of both designers and developers to enhance and further develop the functionality of a site, rather than its content.

But by itself, HTML is not up to this kind of job; that’s not what it was designed to do. A server-side program-
ming language is needed. There are several options, but here are a few of the major products available:

Active Server Pages (ASP) (Microsoft)
• Written using VBScript (server-side JavaScript also possible, but rare)
• Comes installed with Windows servers
• Can run in UNIX/Linux environment using Sun ONE
• Being somewhat overshadowed by ASP.NET

PHP Hypertext Preprocessor (PHP) (open source)
• C-like programming language
• No licensing cost (open-source)
• Can run on UNIX/Linux servers or Windows-based servers
• Close integration with MySQL database

ColdFusion (Adobe)
• Written using tag-based language which integrates well with web-editing software (can also be written using a scripting-like language)
• Easy to learn, quick to create and maintain pages
• Java-based architecture
• Can run on UNIX/Linux server or Windows-based servers

Java 2 Enterprise Edition (J2EE) (Sun)
• Written using cross-platform Java language
• Most often deployed on UNIX/Linux, but can run on any system
• Web page scripting using Java Server Pages (JSP)
• Most appropriate for enterprise-wide installations involving multiple servers, databases, and possibly
mainframe.

ASP.NET (Microsoft)
• Written using VB.NET or C# (other languages possible)
• Deployed in a Windows server environment
• Requires use of Visual Studio .NET for development
• Most appropriate for enterprise-wide installation with other Microsoft solutions

Perl (open source)
• Not really a scripting language (doesn’t co-habitate with HTML)
• Powerful, flexible language, good for dealing with patterns or manipulating data
• Uses less modern Common Gateway Interface (CGI) model
• More appropriate for communication between different applications on a server

Any of these will work with any Relational Database Management System (RDBMS). Here are some common ones:

Oracle (Oracle Corporation)
• Fully featured, flexible, scalable
• Works on UNIX/Linux or Windows servers

SQLServer (Microsoft)
• Fully featured, flexible, scalable
• Works on Windows servers
• Integrates well with .NET

MySQL (open source)
• Fully featured, flexible, scalable
• No licensing costs (open-source)
• Integrates especially well with PHP

Access (Microsoft)
• Friendly user-interface for database management
• Integrates well with MS Office suite
• Not fully featured, limited capabilities, only appropriate for small-scale implementations.

8. Using Image Editors for Fast Loading Graphics

Use Adobe Photoshop/Imageready or Fireworks to create the appropriate type of graphic file Typically GIF or
JPEG. There are other Image Editors available but Photoshop/Imageready and Fireworks are currently the most
popular and are considered the industry standard.


9. Site Planning, Design, and Management

“On time, within scope, and within budget” is the project management motto these days. This is also true for IT projects. IT managers can no longer live in the IT black hole. All IT requires fundamental project manage- ment best practices. Learn how to communicate with your staff. Clarify your project’s business goals to ensure that your project is aiding in the vision and meets your company’s vision. Learn how to follow through your project from inception to implementation. Apply your management skills to the concepts of web design. Apply a strategic focus within your organization to help save time and resources. Learn the benefits of various soft- ware packages to aid in efficiency.

All of these project management practices can help your web site design projects run more smoothly and ensure your web site does what it’s suppose to do.

10.Technological Flexibility

If your web application is Data driven, it is imperative that sharing information with different applications and/or platforms be done in the most flexible way possible. Transforming Data from one format to the next, however, can be arduous and considerably time consuming. Fortunately, storing data in an extensible format, and working with it using XSL, has become relatively easy.


Extensible Markup Langauge (XML) allows developers to store raw data in a text file make up with an HTML-like syntax. With the use of Extensible Style Sheet Transformations (XSL - T), Formatting Objects (XSL - FO), and CSS developers now are able to transform this raw data into an application specific format. Languages com- monly used to augment an XML application are listed below:

• Extensible Markup Langauge (XML): Used to store raw data files
• Document Type Definitions (DTDs): Used to validate XML documents
• eXtensible Stylesheet Language (XSL) and Cascading Style Sheets (CSS): Used to transform the display of XML document into an application specific format. XML utilizes complexities like XPath, functions, modes, and dynamic modification of stylesheets commonly featured in many scripting and programming languages


To Summarize
1. Make sure your web pages are accessible
2. Take steps to minimize security risks
3. Use web server statistics to determine how popular your site is
4. Utilize dynamic technologies styles
5. Be aware of web development software and how to use it efficiently to enhance your web site
6. Use XHTML, DOM Scripting, and CSS to make your site browser and rule independent
7. Choose an appropriate database to ensure it is more dynamic, and does the job of many static pages
8. Use image editors for fast-loading graphics
9. Learn to use planning and project management techniques to build great web sites with large teams
10. Use new technologies like XML, DTDs, and XSL to help your application communicate with other plat-forms in the most flexible manner

If you follow these simple rules, you too can create an excellent web site.

Understanding Domain Name System (DNS)

Domain Name System (DNS) makes it possible to refer to Internet Protocol (IP) based systems (hosts) by human-friendly names (domain names). Name Resolution is the act of determining the IP address (or addresses) of a given host name.

Benefits of DNS
  • Domain names can be logical and easily remembered.
  • Should the IP address for a host change, the domain name can still resolve transparently to the user or application.
The structure of Domain Names
  • Domain names are separated by dots, with the topmost element on the right. Eg: www.yahoo.com . IP addresses have topmost element on the left.
  • Each element may be up to 63 characters long. The entire name may be atmost 255 characters long.
  • The right most element in a domain name is called the Top-Level Domain (TLD). Referring the above example (www.yahoo.com), TLD is 'com'.
  • If a domain name is not shortened, it is called the Fully Qualified Domain Name (FQDN). For example, briefcase.yahoo.com can be specified by a machine in the yahoo.com domain as either briefcase.yahoo.com (FQDN) or as briefcase.
Host names map to IP addresses in a many-to-many relationship. A host name may have one or more IP addresses. Conversely, an IP address may have multiple host names associated with it.

Hosts that are designed to perform email routing are known as mail exchangers. These machines should have special purpose records in DNS called Mail eXchanger (MX) records. When a SMTP server or mail server, needs to send mail to a remote domain, it does a DNS lookup for the Mail Exchanger (MX) of that remote domain. A domain can and should have multiple mail exchangers. Mail that cannot be sent to one mail exchanger, can instead be delivered to an alternative server, thus providing failsafe redundancy.

Different types of Domain Name Servers
  1. Root Name server - Each top level domain (such as in,edu,com etc) has one or more root name servers which are responsible for determining where the individual records are held. These servers are fairly static and every machine on the internet has the capability of reaching any of them. A root name server is allocated like just one to three per country. For example, India has only 2 root name servers.
  2. Authoritative Name Servers - These are the servers that the Root name servers sent queries to. These servers hold the actual information on an individual domain. This information is stored in a file called a zone file. Zone files are updated versions of the original HOSTS.TXT file.
  3. Resolving Name Server - These are the servers that do most of the work when you are trying to get to a machine with a certain host name. Besides being responsible for looking up data, they also temporarily store the data for host names that they have searched out in a cache, which allows them to speed up the resolution for host names that are frequently visited.
Zone
A zone keeps the information about the domain database. It does this by maintaining two types of files:
Zone File - It is used to map host names to address, to identify the mail servers, and to provide other domain information.
Reverse Zone File - This file is responsible for mapping IP address to host names, which is exactly the opposite of what the zone file does.

Note: The zone file and the reverse zone file has to be maintained by the user.

Name Server Hierarchy
Master Name Server - Also called primary server. This contains the master copy of data for a zone.
Slave Name Server - Also known as secondary server. This provides a backup to the master name server. All slave servers maintain synchronization with their master name server.
A zone may have multiple slave servers. But there will be only one master name server per zone.

Apache : Name-based Vs IP Based Virtual Hosting

Often when, you attend interviews for network administration related jobs , the one question you may encounter while discussing about web servers is the difference between name-based and IP based virtual hosting. Here I will explain the difference between the two.

In IP-based virtual hosting, you are running more than one web site on the same server machine, but each web site has its own IP address. In order to do this, you have to first tell your operating system about the multiple IP addresses. See here configuring multiple IP addresses on a single NIC . You also need to put each IP in your DNS, so that it will resolve to the names that you want to give those addresses .

In Name-based virtual hosting, you host multiple websites on the same IP address. But for this to succeed, you have to put more than one DNS record for your IP address in the DNS database. This is done using CNAME tag in BIND. You can have as many CNAME(s) as you like pointing to a particular machine. Of course, you also have to uncomment the NameVirtualHost section in httpd.conf file and point it to the IP address of your machine.

#FILE: httpd.conf
...
NameVirtualHost 192.168.0.1
...

Setting up multiple IP addresses on a single NIC

In linux, you can bind multiple IP addresses on a single NIC. This is usually done in case you are using your linux machine as a webserver and is hosting multiple domains and you want to bind each domain to a unique IP address. This is how it is done.
Let us assume that you already have a NIC which is bound with a static IP address. Then you will have a file called /etc/sysconfig/network-scripts/ifcfg-eth0 .My ifcfg-eth0 file has the following entries:
# File: ifcfg-eth0
DEVICE=eth0
ONBOOT=yes
BOOTPROTO=static
IPADDR=192.168.0.1
NETMASK=255.255.255.0
BROADCAST=192.168.0.255
NETWORK=192.168.0.0
HWADDR=00:80:48:34:C2:84
Now to bind another IP address to the same NIC, I create a copy of the above file ifcfg-eth0 and name it as ifcfg-eth0:1
# cd /etc/sysconfig/networking-scripts
# cp ifcfg-eth0 ifcfg-eth0:1
Now just change the values of the DEVICE and IPADDR in the file as follows:
# File: ifcfg-eth0:1
DEVICE=eth0:1
ONBOOT=yes
BOOTPROTO=static
IPADDR=192.168.0.5
NETMASK=255.255.255.0
BROADCAST=192.168.0.255
NETWORK=192.168.0.0
HWADDR=00:80:48:34:C2:84
And lastly, restart the networking service. If you are using RedHat, then it is as simple as :
# service network restart

How to install a Network card in linux

There are different ways of installing a network card in linux - and that too depending on the linux distribution that you are using. I will explain each one of these methods here.
1) The Manual method
First open the computer case and insert the network card into an empty PCI slot. Then boot up your machine to load linux. In linux login as root and then navigate to the directory /lib/modules/kernel_version_number/net/ . Here you will find the modules supported by your system. Assuming that you have a 3Com ethernet card, in which case, the module name is 3c59x , you have to add this in the /etc/modules.conf file to let the machine detect the card each time the machine boots.
#File: /etc/modules.conf
alias eth0 3c59x
Note: If you have only one network card, it is known by the name eth0, the succeeding network cards in your computer go by the name eth1, eth2 ... and so on.
Now you have to load the module into the kernel.
root# /sbin/insmod -v 3c59x
Next configure an IP address for the network card using ifconfig or netconfig or any other method if your machine gets its IP address from a DHCP server. Eg:
root# ifconfig eth0 192.168.1.5 netmask 255.255.255.0 broadcast 192.168.1.255
2) The Easy way
RedHat/Fedora distributions of linux ships with Kudzu a device detection program which runs during systems initialization (/etc/rc.d/init.d/kudzu). This can detect a newly installed NIC and load the appropriate driver. Then use the program /usr/sbin/netconfig to configure the IP address and network settings. The configuration will be stored so that it will be utilized upon system boot.


How to Assign an IP address

Computers may be assigned a static IP address or assigned one dynamically (via DHCP). Here I will explain the steps needed to assign an IP address to your NIC.
Choose one of the following methods:

=> Dynamic Host Configuration Protocol (DHCP) is a protocol used by networked computers (clients) to obtain IP addresses and other parameters such as the default gateway, subnet mask, and IP addresses of DNS servers from a DHCP server.
Command line :
/sbin/ifconfig eth0 192.168.1.3 netmask 255.255.255.0 broadcast 192.168.1.255
GUI tool : You can use the GUI tool /usr/bin/neat - Gnome GUI network administration tool. It handles all interfaces and configures for both static assignment as well as dynamic assignment using DHCP.

Console tool : /usr/sbin/netconfig (Only seems to work for the first network interface eth0 but not eth1,...)

The ifconfig command does NOT store this information permanently. Upon reboot this information is lost. (Manually add the commands to the end of the file /etc/rc.d/rc.local to execute them upon boot.) The command netconfig and /usr/bin/neat make permanent changes to system network configuration files located in /etc/sysconfig/network-scripts/ , so that this information is retained.
The Red Hat configuration tools store the configuration information in the file /etc/sysconfig/network. They will also allow one to configure routing information.
# File: /etc/sysconfig/network
# Static IP address Configuration:
NETWORKING=yes
HOSTNAME=my-hostname # Hostname is defined here and by command hostname
FORWARD_IPV4=true # True for NAT firewall gateways and linux routers. False for
# everyone else - desktops and servers.
GATEWAY="XXX.XXX.XXX.YYY" # Used if your network is connected to another
# network or the internet.

# Gateway not defined here for DHCP.

# Or for DHCP configuration: in the same file /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=my-hostname # Hostname is defined here and by command hostname
# Gateway is assigned by DHCP.
# File: /etc/sysconfig/network-scripts/ifcfg-eth0
# Static IP address configuration:
DEVICE=eth0
BOOTPROTO=static
BROADCAST=XXX.XXX.XXX.255
IPADDR=XXX.XXX.XXX.XXX
NETMASK=255.255.255.0
NETWORK=XXX.XXX.XXX.0
ONBOOT=yes
# OR for DHCP configuration:
DEVICE=eth0
ONBOOT=yes
BOOTPROTO=dhcp
Used by script /etc/sysconfig/network-scripts/ifup to bring the various network interfaces on-line.
To disable DHCP change BOOTPROTO=dhcp to BOOTPROTO=none
In order for updated information in any of these files to take effect, one must issue the command:
root# service network restart