WHAT IS IPv6?

IPv6 is an ever-emerging star of the Internet. Several years ago, when the protocol started to be drafted, it immediately entered under every spotlight available in IT. Back then, the perspective of not having any more IPv4 addresses to assign seemed horrifying: nobody was ready for it, and there were quite a few people who expected the Internet to be dead and buried in a few months.

The fears seemed to be premature back then. Indeed, five years after news of IPv6 started grabbing the headlines, the perspective of IPv4 depletion is still at least five years away. This does serve IANA's purposes: the migration is slow and gradual.

But most important, the migration is not determined only by the depletion problem. IPv6 offers several advantages of its own, besides the much larger address space, which ensures that IPv6 addresses will certainly not be depleted anywhere in the following decades.

What are these advantages? The IPv6 protocol includes many innovations, along with some features that are present in IPv4, but were developed after the IPv4 protocol itself. The most important of these are link-local addresses, jumbograms, link-layer level error checking, as well as native support for multicasting and network-layer security.

Link-local addresses are also present in IPv4. These are special addresses used in addition to global addresses, which applications can use. Link-local addresses are always present and never change, greatly simplifying the configuration and routing protocols.

Jumbograms are very large packets, potentially much larger than the IPv4-standard 64 kB packets. In a network, the data stream is not continuous, but discrete, carried using so-called packets, standard-sized pieces of information, which include not only the information itself, but also other details used for routing, error checking and so on. When IPv4 was designed, 64 kB packets were practical enough. Today, however, something as simple as a photograph requires hundreds of packets, each containing more than just the information. Thus, some traffic is, essentially, "wasted". Jumbograms come to alleviate this: since several hundreds of KiB (or even more - up to 4 GB) can be packed into a single packet, the transfer of large files requires fewer packets, and hence less traffic used for something else than information. Furthermore, jumbograms can considerably simplify the design of protocols and low-level applications.

Unlike IPv4, IPv6 does not rely on network-level checksum fields to ensure that information is correctly transmitted. When IPv4 was designed, the network infrastructure was less reliable than today, meaning that errors were often occurring during transmission. It is thought that errors are much less common today, and thus, it makes sense to transfer error-checking to transport layers (protocols like TCP or UDP). As a consequence, IPv6 is quite easier to implement - an important advantage in the development of embedded systems, like network-enabled house appliances.

Finally, IPv6 has native support for IPsec, a network-layer encryption and authentication protocol. Unlike IPv4, IPv6 requires that this protocol is implemented.

IPv6 under Windows

Configuring Windows for IPv6 support is not very difficult. In fact, if you have Windows Vista or Windows Server 2008, you need not do anything - IPv6 is already there and enabled. Due to IPv6's support for link-local addresses and DHCP, chances are you do not even need to go through any additional configuration tasks.

If you are using Windows XP, you will have to install the IPv6 protocol first. To do so, open the Command Prompt (Start -> Programs -> Accessories -> Command Prompt) and type:

C:>netsh interface ipv6 install

To make sure that the installation has been successful, run ipconfig. The output should include a list of IPv6 addresses, along with some other IPv6 and IPv4-related output. It may look quite similar to this:

c:>ipconfig

Ethernet adapter Ethernet:
Connection-specific DNS Suffix . : iptest.example.com
IP Address. . . . . . . . . . . . : 192.168.123.254
Subnet Mask . . . . . . . . . . . : 255.255.252.0
IP Address. . . . . . . . . . . . : 2001:db8:8311:f282:2461:6134:a4a7:faa7
IP Address. . . . . . . . . . . . : 2001:db8:8311:f282:a451:f134:64a1:b944
IP Address. . . . . . . . . . . . : 2001:db8:8311:f282:651:f5ff:ab05:ac75
IP Address. . . . . . . . . . . . : fec0::f282:200:ab8a:ab3e:fc61%1
IP Address. . . . . . . . . . . . : fe80::200:ab8a:ab3e:fc61%4
Default Gateway . . . . . . . . . : 192.168.123.254
fe80::210:ffff:fed6:61c0%4

In most IPv6 networks, it is highly unlikely that you will need to change the IPv6 address. However, if you need to, you can do so by running the following command in the Command Prompt:

c:>netsh interface ipv6 add (address)
replacing (address) with the IPv6 you want to use.

IPv6 under Linux

Most Linux distributions come with an IPv6-ready kernel and userpace toolset. If you are using an older distribution, or if you have compiled the kernel manually, you may want to check that IPv6 support is available. If it does, your /proc filesystem will include the file /proc/net/if_inet6. If it is not, it means you need to load the IPv6 module, or, if it is not available, to recompile the kernel.

Loading the IPv6 modprobe is done by running modprobe:
$ modprobe ipv6

The module will be loaded if it exists. If not, you will have to recompile the kernel, or at least update it. Generally, updating the kernel is the easiest solution if your distribution allows you to. You will hardly find a single Linux distribution not supporting IPv6 by default. Otherwise, you will have to recompile your kernel for IP support. The list of options should include packet socket, Unix domain sockets, kernel/user netlink socket, routing messages, tcp/ip networking, the ipv6 protocol (compiled as a module if you want) and /proc filesystem support.

After enabling IPv6 support by loading the IPv6 module (if you have compiled IPv6 directly into the kernel, then you need not load the module - IPv6 support is already there), you can test your configuration by running ifconfig. The output should include lines like the following:

$ ifconfig

eth1 Link encap:Ethernet HWaddr 00:1C:429:33:65
(some output omitted)
inet6 addr: 2001:a50:3450:1:20A:cbff:facf:9d0a/64 Scope:Global
inet6 addr: fe80::108:c75f:fedf:9d0a/64 Scope:Link
(some output omitted)
The lines that start with inet6 are the ones important.

Should you enable IPv6?

If you use IPv6 in a network, the answer is yes, definitely. IPv6 greatly simplifies network configuration - since it is so easy to assign dynamic addresses and since many of the IPv4-related hassles are gone, you hardly ever need to touch your TCP/IP configuration with IPv6.

However, if you do not use it at all, disabling it may slightly improve your network performances. Nevertheless, chances are you do not need to do it. Keeping it is a better bet.

ABOUT WINDOWS XP

19 things you didn't know about Windows XP

1. It boasts how long it can stay up. Whereas previous versions of Windows were coy about how long they went between boots, XP is positively proud of its stamina. Go to the Command Prompt in the Accessories menu from the All Programs start button option, and then type 'systeminfo'. The computer will produce a lot of useful info, including the uptime. If you want to keep these, type 'systeminfo > info.txt'. This creates a file called info.txt you can look at later with Notepad. (Professional Edition only).

2. You can delete files immediately, without having them move to the Recycle Bin first. Go to the Start menu, select Run... And type ' gpedit.msc'; then select User Configuration, Administrative Templates, Windows Components, Windows Explorer and find the Do not move deleted files to the Recycle Bin setting. Set it. Poking around in gpedit will reveal a great many interface and system options, but take care ? some may stop your computer behaving as you wish. (Professional Edition only).

3. You can lock your XP workstation with two clicks of the mouse. Create a new shortcut on your desktop using a right mouse click, and enter 'rundll32.exeuser32.dll, LockWorkStation' in the location field. Give the shortcut a name you like. That's it -- just Double click on it and your computer will be locked. And if that's not easy enough, Windows key + L will do the same.

4. XP hides some system software you might want to remove, such as Windows Messenger, but you can tickle it and make it disgorge everything. Using Notepad or Edit, edit the text file /windows/inf/sysoc.inf, search for the word 'hide' and remove it. You can then go to the Add or Remove Programs in the Control Panel, select Add/Remove Windows Components and there will be your prey, exposed and vulnerable.

5. For those skilled in the art of DOS batch files, XP has a number of interesting new commands. These include 'eventcreate' and 'eventtriggers' for creating and watching system events, 'typeperf' for monitoring performance of various subsystems, and 'schtasks' for handling scheduled tasks. As usual, typing the command name followed by /? Will give a list of options -- they're all far too baroque to go into here.

6. XP has IP version 6 support -- the next generation of IP. Unfortunately this is more than your ISP has, so you can only experiment with this on your LAN. Type 'ipv6 install' into Run... (it's OK, it won't ruin your existing network setup) and then 'ipv6 /?' at the Command line to find out more. If you don't know what IPv6 is, don't worry and don't bother.

7. You can at last get rid of tasks on the computer from the command line by using 'taskkill /pid' and the task number, or just 'tskill' and the process number. Find that out by typing 'tasklist', which will also tell you a lot about what's going on in your system.

8. XP will treat Zip files like folders, which is nice if you've got a fast machine. On slower machines, you can make XP leave zip files well alone by typing 'regsvr32 /U zipfldr.dll' at the command line. If you change your mind later, you can put things back as they were by typing 'regsvr32 zipfldr.dll'.

9. XP has ClearType -- Microsoft's anti-aliasing font display technology -- but doesn't have it enabled by default. It's well worth trying, especially if you were there for DOS and all those years of staring at a screen have given you the eyes of an astigmatic bat.
To enable ClearType, right click on the desktop, select Properties, Appearance, Effects, select ClearType from the second drop-down menu and enable the selection. Expect best results on laptop displays. If you want to use ClearType on the Welcome login screen as well, set the registry entry HKEY_USERS/.DEFAULT/ControlPanel/Desktop/FontSmoothingType to 2.

10. You can use Remote Assistance to help a friend who's using network address translation (NAT) on a home network, but not automatically. Get your pal to email you a Remote Assistance invitation and edit the file. Under the RCTICKET attribute will be a NAT IP address, like 192.168.1.10. Replace this with your chum's real IP address -- they can find this out by going to WWW.WHATISMYIP.COM-- and get them to make sure that they've got port 3389 open on their firewall and forwarded to the errant computer.

11. You can run a program as a different user without logging out and back in again. Right click the icon, select Run As... And enter the user name and password you want to use. This only applies for that run. The trick is particularly useful if you need to have
Administrative permissions to install a program, which many require. Note that you can have some fun by running programs multiple times on the same system as different users, but this can have unforeseen effects.

12. Windows XP can be very insistent about you checking for auto updates, registering a Passport, using Windows Messenger and so on. After a while, the nagging goes away, but if you feel you might slip the bonds of sanity before that point, run Regedit, go to

HKEY_CURRENT_USER/Software/Microsoft/Windows/CurrentVersion/Explorer/Advanced and create a DWORD value called EnableBalloonTips with a value of 0.

13. You can start up without needing to enter a user name or password. Select Run... from the start menu and type 'control userpasswords2', which will open the user accounts application. On the Users tab, clear the box for Users Must Enter A User Name And Password To Use This Computer, and click on OK. An Automatically Log On dialog box will appear; enter the user name and password for the account you want to use.

14. Internet Explorer 6 will automatically delete temporary files, but only if you tell it to. Start the browser, select Tools / Internet Options... and Advanced, go down to the Security area and check the box to Empty Temporary Internet Files folder when Browser is closed.

15. XP comes with a free Network Activity Light, just in case you can't see the LEDs twinkle on your network card. Right click on My Network Places on the desktop, then select Properties. Right click on the description for your LAN or dial-up connection, select Properties, then check the Show icon in notification area when connected box. You'll now see a tiny network icon on the right of your task bar that glimmers nicely during network traffic.
16. The Start Menu can be leisurely when it decides to appear, but you can speed things along by changing the registry entry HKEY_CURRENT_USER/ControlPanel/Desktop/MenuShowDelay from the default 400 to something a little snappier. Like 0.
17. You can rename loads of files at once in Windows Explorer. Highlight a set of files in a window, then right click on one and rename it. All the other files will be renamed to that name, with individual numbers in brackets to distinguish them. Also, in a folder you Can arrange icons in alphabetised groups by View, Arrange Icon By... Show In Groups.

18. Windows Media Player will display the cover art for albums as it plays the tracks -- if it found the picture on the Internet when you copied the tracks from the CD. If it didn't, or if you have lots of pre-WMP music files, you can put your own copy of the cover art in the same directory as the tracks. Just call it folder.jpg and Windows Media Player will pick it up and display it.

19. Windows key + Break brings up the System Properties dialogue box; Windows key + D brings up the desktop; Windows key + Tab moves through the taskbar buttons.



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