You love your pets. I know I sure do. My dog is a very important part of my family and I hate having to leave him alone all day while I’m at work. That is why I installed what I call the ‘PetCam’ – a web enabled IP camera that allows me to check in on my dog from any location via the world wide web. And guess what, it turns out that Fido is quite busy while I’m away – and he has an incredible internal clock – he gets very agitated about an hour before I return home from work – who knew!

Installation of a web enabled Pet Cam is actually quite easy to do. The first thing you need is high speed Internet. Sending video over the web requires both speed and a healthy bandwidth allocation from your internet service provider, so make sure to check with your ISP on any existing bandwidth caps. Both Cable and DSL Internet services are idea for this application.

Next, you will need a router to which you will connect your internet camera. If you want the freedom of a wireless IP camera (recommended), a wireless router will be required. Most IP cameras come with a CAT5 Ethernet connection, but who wants cables running all over the house! This article assumes that you already have a router installed and functioning with a high speed Internet service.

Now comes the fun part – selecting the right camera for the job. Because we are looking at transmitting video over the Internet, the best choice is an Internet IP camera. Do not mistake these cameras for a webcam. Although they might look similar, Internet cameras are a small computers with a built in web server. Unlike a webcam, they are independent entities that do not require a computer to function. They are the ultimate independent contractor!

Keep in mind that most Internet IP cameras work with CMOS video sensors, therefore even if night vision is offered, it probably won’t work very well – these cameras are meant for daytime applications.

I strongly recommend the Linksys WVC54GCA and DLINK DCS950G Internet Cameras – both are great entry level IP cameras that will get the job done and can be purchased at a reasonable cost (between $100 to $125 US dollars). More advanced (and expensive) models add features such as Pan and Zoom – nice to have features, but not must haves.

If you already have a DLINK or Linksys router, it may be a good idea to stick with the same manufacturer for your Internet Camera as the included documentation will provide more specific router configuration information.

So how do we get this remarkable little device to broadcast video to the Internet. The first thing we need to do is configure the new internet camera. This usually involves establishing a wired connection to the camera from your router. You then load the installation software onto your computer and proceed with the setup as specified by the documentation.

The first thing the software will do is detect the new camera and have you specify a unique IP address for the device – try to avoid using DHCP, as a static IP address is preferable. If you are using a wireless camera, you will need to configure the wireless settings for the camera, including any security passwords for WEP or WPA. Additionally, you will need to identify and document the port number used by the camera to communicate with the outside world (some cameras let you choose the port).

If your internet service does not provide a static IP address, you will need to open an account with a dynamic DNS service provider such as DynDNS.com. This service provides you with a free domain name which will automatically detect any changes to your home IP address. Most cameras will have a configuration page where you can enter your dynamic DNS settings.

All that is left is to do is open a port on your router, a process referred to as port forwarding. This will allow the camera to communicate with the outside world in a secure fashion.

This may all sound a bit complex, but it is actually quite easy to do if you are even mildly tech savvy. If you need assistance, a quick call to your local Nerds on Wheels service should have you up and running in no time at all.

WHAT IS ISDN 2 

Formerly known as OnRamp 2, ISDN 2 transforms your existing analogue telephone line into two digital connections. ISDN2 features are;

Two telephone numbers

Two digital channels capable of transferring both voice and data at bandwidth rates of 2 x 64kbps or 128kbps when 2 lines are combined Quick safe and clear transfer of data including graphics, studio-quality videos and large data files Only one service line is required for telephones, faxes or computers allowing you to use the other line to work remotely in the field or at home Video conferencing facilities with live, full-colour, two-way video, audio and data communication (additional equipment required) When used with an ISDN compatible Internet plan it provides faster-than-dial-up internet and email access An ISDN2 service must be connected to an ISDN compatible PABX system at the customers premises A Full explanation of ISDN 2 features is located at this link.

WHAT IS ISDN 2 ENHANCED

ISDN2 enhanced services are identical to standard ISDN2 services but are supplied with an integrated network termination device and router. Since this hardware is more expensive to supply, the monthly line rental is a few dollars higher than standard ISDN2.

The integrated unit supplied currently is the Open Networks NT1 plus II . This unit allows the customer to connect multiple computers on a small LAN to the ISDN service to leverage the ISDN investment. The NT1 plus II also allows customers to “bond” the two channels together for 128kbps internet access when no phone lines are in use. Although these units require mains power they have the ability to keep the main phone line active during a mains power failure.

WHY USE ISDN 2 PHONE LINES

ISDN 2 Phone lines are Digital phones lines delivering clearer and faster phone calls.

ISDN 2 are a scaleable service in that you can add an additional set of lines in increments of 2 lines at a time. eg start with 2 lines and add in 2/4/6/or 8 ISDN2 services as required.

ISDN 2 gives you the availability of a 100 Number Direct in Dial range. Even if you only have 1 or 2 ISDN 2 services you can have 100 phone numbers or more. ISDN 2 is ideally suited to small to medium business that require crisp clear digital communication lines in conjunction with a PABX phone system. ISDN 2 Business phone lines have access to all the great business phone line features you need including Line Hunt & Caller ID.

HOW DOES ISDN 2 WORK?

ISDN technology converts a standard analogue telephone line into 3 separate channels.

2 Bearer Channels

Each bearer channel has an available bandwidth of 64kbps which can be used for voice, video, data, or multimedia calls. These bearer channels can be aggregated together to give 128kbps bandwidth which is useful in areas where broadband internet access is not available.

1 Delta Channel

The Delta (“D”) channel has an available bandwidth of 16 kbps and cannot, therefore, be used for voice calls. It is used primarily for communications (or “signaling”) between switching equipment in the ISDN network and the ISDN equipment at your site.

Due to the above structure you may sometimes see an ISDN2 service referred to as ISDN (2B+D).

HOW DO I CONNECT TO ISDN 2 PHONE SERVICE

As ISDN is digital, there is no need for a modem. However, a customer will need a terminal adapter to receive the ISDN service. A terminal adaptor enables the communication from the user’s terminal to the network and serves as an interface between the ISDN BRI line and the customers equipment.

Terminal adaptors are sometimes referred to as Network Termination (NT) devices or ISDN modems/routers, although this latter term is slightly misleading.

The terminal adapter is provided by the ISDN service provider.

To connect the customer’s local area network (LAN) to an ISDN2 service the customer will require a separate ISDN router or (as is more common) a terminal adaptor with a modem / router built in.

Customer wishing to connect a LAN to an ISDN2 service should choose the ISDN2 enhanced service.

WHAT TYPE OF ISDN 2 SERVICES ARE THERE?

ISDN services come in two types known as Basic Rate Interfaces or Basic Rate Access(BRI/BRA) and Primary Rate Interfaces or Primary Rate Access (PRI/PRA).

ISDN services are only available in channel blocks of 2, 10, 20 and 30.

If a customer needs, say 6 channels they must implement 3 x ISDN2 connections. For customers wanting, say 14 channels they must implement an ISDN10 and 2 X ISDN2 channels. Customers cannot order an odd number of channels.

WHAT IS ISDN 2 USED FOR?

ISDN can be used for a range of voice, data, video and image transfer applications including – Telephony: ISDN provides clear telephone connections. In conjunction with digital telephones, small phone systems and PABX systems, ISDN can offer some additional call and messaging features compared to analogue services.

Prior to the increased availability of ADSL internet ISDN 2 was also used as the highest speed available Internet service.

WHAT IF I WANT MORE THAN 10 ISDN CHANNELS

ISDN primary rate services are only available in blocks of 10, 20 or 30. If a customer requires a number between two blocks they will need to combine a primary rate service with one or more basic rate services.

Since basic rate services only come in multiples of two it is impossible to have an odd number of ISDN channels.

As an example, to achieve, say 16 channels a customer would need

1 x ISDN 10

3 x ISDN2

This would require the customer to have a PABX with both a primary rate interface card and a basic rate interface card installed.

HOW DO I CONNECT TO ISDN 2 PHONE SERVICE

As ISDN is digital, there is no need for a modem. However, a customer will need a terminal adapter to receive the ISDN service. A terminal adaptor enables the communication from the user’s terminal to the network and serves as an interface between the ISDN BRI line and the customers equipment.

Terminal adaptors are sometimes referred to as Network Termination (NT) devices or ISDN modems/routers, although this latter term is slightly misleading.

The terminal adapter is provided by the ISDN service provider.

To connect the customer’s local area network (LAN) to an ISDN2 service the customer will require a separate ISDN router or (as is more common) a terminal adaptor with a modem / router built in.

Customer wishing to connect a LAN to an ISDN2 service should choose the ISDN2 enhanced service.

A Full explanation of ISDN 2 features is located at this link.

These days the wireless networks are turning  more and more popular. Wireless home networks are very attractive to internet users as the simplicity of installation and practicality of being able to surf the net anywhere in the house. Some basic things about the wireless networks are to be known before attempting to start the set up of  wireless home networks.  To help you get the better  understanding of wireless networking you can read up more about the wireless networking protocols.

DSL modem and a cable with a broadband internet connection is  needed to setup a wireless home network. The common  arrangement at home is usually that of the desk top computer being plugged directly into the modem. You have a laptop and you need to connect laptop to PC which is connected to internet wirelessly , you can find the  answers  in this tutorial. This can be made  achievable  with some hardware.First you need to have a wireless router.  You also need  to add a USB wireless network adapter to your desk top PC and a PC card-based network adapter for your laptop computer. For all the additional hardware you buy it is advised  to choose the same brand for obvious reasons. Refer  to the documentation that comes with your hardware for the installation process.

You can begin the set up when you already have all the necessary hardware installed. First you need to unplug or turn off the DSL modem then connect the wireless router to the modem. For assistance you can refer the documentation that came with your hardware. Your computer will wirelessly connect to your router when you have  configured. The next step is to  set up your wireless router. Your router’s configuration page can be accessed  using Internet Explorer.

There are some things you need to configure as the most of the default settings there are rather safe left alone. The name for your network must be chosen, choose a unique name or SSID.  Be sure that no one around that is near you is using the same name. The next step is, if your router requires it, to give a unique passphrase that it will use to generate some keys. Choosing administrative password is the last step and with this you are done.  Password must be chosen in such a way that it is not too short and not easy to guess.  Be sure to save every setting you’ve configured. The actual steps involved in configuring these settings  vary according to the kind of router you have.

The next step is to configure your laptop’s network adapter. It is simple to follow Window’s XP’s on-screen instructions for this one. Right-click the icon for wireless network in your task bar and select “View Available Wireless Networks” in the pop up menu that appears. The Wireless Network Connection window will show and there you will see the name you chose for your wireless network listed. If you don’t see your network click refresh list in upper left corner.  You will then be prompted to enter a key, this is the key that you wrote down in both the Network key and Confirm network key boxes. Click Connect.  As it connects to your network you can see the progress. When you’re already connected you can close the Wireless Network Connection window.   Wireless connection has been  configured by you.

Technology is evolving at a rapid pace. With new products, or better versions of older products being released every year, older products are rendered useless. Every household has an assortment of ‘outdated’ technology. Technology left unused for years, covered with layers of dust.

But often the usefulness of these ‘outdated’ products is only limited by our creativity and willingness to experiment.

I recently noticed an old Sony stereo system, and an old Dell Pentium III desktop lying around the house. At first I though about disposing of these, but then I thought better. I ended up with a setup that allows me to remotely play music on the stereo system using any device with wi-fi and a browser, whether it be a desktop, laptop, Palm Pilot, HP iPAQ, or a cell phone.

How it basically works:

The Dell computer, which is connected to the stereo system, acts as a server on the LAN. Other devices on the LAN can either stream songs to the server, or remotely access the server and launch locally stored songs on it.

The following explains how I accomplished this setup. It assumes that you already know how to setup a wireless router.

The following hardware was used:

- Sony Stereo System

- Old Dell CPU (500 MHZ Pentium III, 128 MB Ram, 6 GB Hard Drive)

- A Y cable (male stereo 1/8-inch plug to two male RCA plugs)

- An Ethernet cable

- Speedtouch wireless router

- Monitor

- Keyboard

- Mouse

Note: The monitor and mouse is only required when the computer is being set up. Once the software has been installed and correctly configured, the computer only needs a keyboard attached to it to boot up. If a laptop is being used as the server instead, the extra hardware is not needed.

The following software was used:

-Microsoft Windows XP Professional Edition

-VLC Media Player

-TightVNC server and viewer

Note: The same setup could be obtained using a different operating system, such as Linux or Mac OS, since the software required is available for these operating systems as well.

What I did, step by step

1) I hooked up the monitor, keyboard, and mouse to the Dell CPU

2) I powered it on, inserted the Windows XP CD, and booted off the CD

3) Following the onscreen steps, I formatted my 6 GB hard drive, and installed Windows XP on it

4) After the installation was complete, I plugged the computer into the router using the Ethernet cable

5) I launched up the browser, and downloaded VLC Media Player from http://www.videolan.org/

6) I installed VLC media player

7) I downloaded TightVNC from http://www.tightvnc.com/

I installed TightVNC

(During the installation, you will be asked to ‘Select Additional Tasks’. When asked, make sure to select both boxes. This will register TightVNC server as a system service, and start it whenever windows starts)

9) I set a password for the VNC server

10) I went to Control Panel -> Power Options, disabled hibernate and standby, and set ‘When I press the power button on my computer’ to shutdown

11) I went to the properties of the network connection, opened up TCP/IP, and set a static IP address. The IP I set was 10.0.0.5. The range for IP addresses differs from router to router. Consult your router’s manual, or the internet if you need to find out the IP range for your router. More instructions on how to set a static IP address can be found online.

12) Using the Y cable, I connected the computer to the stereo system. The male 1/8-inch plug goes into the audio out port on the sound card. The red RCA plug goes into the right “AUX in” port on the stereo, and the other RCA plug goes into the left “AUX in” port.

13) The stereo was set to AUX

After this, I unplugged the monitor and mouse from the CPU. I neatly stacked the CPU, with the keyboard, under the table on which the stereo was placed

If the power button is pressed, the computer boots, loads up Windows XP, and loads up the VNC server. Pressing the power button again shuts down Windows and turns off the computer.

This CPU is basically a server with a permanent IP on the network, which can receive streams from other devices on the network, and play them on the stereo.

HOW TO USE THE SERVER TO REMOTELY PLAY MUSIC

There are two ways to go about playing music

The first one

is streaming music. This means the music is located on some other device, but is played on the server over the network.

The following explains the steps I took to stream music from my laptop

1) I set my laptop’s static IP to 10.0.0.1

2) I installed the TightVNC viewer and VLC media player on my laptop

3) I launched the VNC viewer, typed in the server IP (10.0.0.5) and the password and remotely accessed the server

4) Using the VNC viewer on my laptop, I remotely launched VLC media player on the server. I then clicked on file-> open network stream, and set the address to udp://10.0.0.1 (Address of my laptop, where the files were located)

5) I launched VLC media player on my laptop, clicked on file -> open file

From the menu, I clicked on browse and selected a whole bunch of songs

I selected Stream/Save under Advanced Options, and in settings, selected UDP, and set address to 10.0.0.5 (Address of the server, where the files were to be played)

After this I pressed ok, and, the songs started playing on my stereo!

Using my laptop from anywhere in my house, I could remotely pause, play, forward, or change songs on the stereo.

Using VLC media player for Windows CE /Pocket PC, I can stream music from my HP iPAQ as well!

The second way

is to play songs locally stored on the server, by remotely accessing the server from another device.

The following are the steps I followed to accomplish this

1) I launched the VNC viewer on my laptop, and accessed the server as mentioned earlier

2) After launching VLC media player on the server, I clicked Settings -> Add Interface -> Web Interface

Enabling the web interface allows any device on the network to go to http://10.0.0.5:8080, and remotely control the music from there

Of course, I could have just used the VNC viewer to remotely control VLC media player, but enabling the web interface allows any device with wi-fi and a web browser to control the player. Therefore, even if a cell phone with wi-fi does not have a VNC viewer, it can use its browser to access the controls of VLC media player, and remotely control the music being played on the server.

Now you can use your handheld devices to control the music being played on your stereo system!

I hope this guide was helpful. If you run into any problems while setting this up, feel free to email me at hammadnaseem@gmail.com, with the subject “Wireless Stereo Help”.

NOTE: Anywhere in this guide, the word ‘server’ refers to the Dell computer

For more Free Information visit Universal Remote Codes

Technology is evolving at a rapid pace. With new products, or better versions of older products being released every year, older products are rendered useless. Every household has an assortment of ‘outdated’ technology. Technology left unused for years, covered with layers of dust.

But often the usefulness of these ‘outdated’ products is only limited by our creativity and willingness to experiment.

I recently noticed an old Sony stereo system, and an old Dell Pentium III desktop lying around the house. At first I though about disposing of these, but then I thought better. I ended up with a setup that allows me to remotely play music on the stereo system using any device with wi-fi and a browser, whether it be a desktop, laptop, Palm Pilot, HP iPAQ, or a cell phone.

How it basically works:

The Dell computer, which is connected to the stereo system, acts as a server on the LAN. Other devices on the LAN can either stream songs to the server, or remotely access the server and launch locally stored songs on it.

The following explains how I accomplished this setup. It assumes that you already know how to setup a wireless router.

The following hardware was used:

- Sony Stereo System

- Old Dell CPU (500 MHZ Pentium III, 128 MB Ram, 6 GB Hard Drive)

- A Y cable (male stereo 1/8-inch plug to two male RCA plugs)

- An Ethernet cable

- Speedtouch wireless router

- Monitor

- Keyboard

- Mouse

Note: The monitor and mouse is only required when the computer is being set up. Once the software has been installed and correctly configured, the computer only needs a keyboard attached to it to boot up. If a laptop is being used as the server instead, the extra hardware is not needed.

The following software was used:

-Microsoft Windows XP Professional Edition

-VLC Media Player

-TightVNC server and viewer

Note: The same setup could be obtained using a different operating system, such as Linux or Mac OS, since the software required is available for these operating systems as well.

What I did, step by step

1) I hooked up the monitor, keyboard, and mouse to the Dell CPU

2) I powered it on, inserted the Windows XP CD, and booted off the CD

3) Following the onscreen steps, I formatted my 6 GB hard drive, and installed Windows XP on it

4) After the installation was complete, I plugged the computer into the router using the Ethernet cable

5) I launched up the browser, and downloaded VLC Media Player from http://www.videolan.org/

6) I installed VLC media player

7) I downloaded TightVNC from http://www.tightvnc.com/

I installed TightVNC

(During the installation, you will be asked to ‘Select Additional Tasks’. When asked, make sure to select both boxes. This will register TightVNC server as a system service, and start it whenever windows starts)

9) I set a password for the VNC server

10) I went to Control Panel -> Power Options, disabled hibernate and standby, and set ‘When I press the power button on my computer’ to shutdown

11) I went to the properties of the network connection, opened up TCP/IP, and set a static IP address. The IP I set was 10.0.0.5. The range for IP addresses differs from router to router. Consult your router’s manual, or the internet if you need to find out the IP range for your router. More instructions on how to set a static IP address can be found online.

12) Using the Y cable, I connected the computer to the stereo system. The male 1/8-inch plug goes into the audio out port on the sound card. The red RCA plug goes into the right “AUX in” port on the stereo, and the other RCA plug goes into the left “AUX in” port.

13) The stereo was set to AUX

After this, I unplugged the monitor and mouse from the CPU. I neatly stacked the CPU, with the keyboard, under the table on which the stereo was placed

If the power button is pressed, the computer boots, loads up Windows XP, and loads up the VNC server. Pressing the power button again shuts down Windows and turns off the computer.

This CPU is basically a server with a permanent IP on the network, which can receive streams from other devices on the network, and play them on the stereo.

HOW TO USE THE SERVER TO REMOTELY PLAY MUSIC

There are two ways to go about playing music

The first one

is streaming music. This means the music is located on some other device, but is played on the server over the network.

The following explains the steps I took to stream music from my laptop

1) I set my laptop’s static IP to 10.0.0.1

2) I installed the TightVNC viewer and VLC media player on my laptop

3) I launched the VNC viewer, typed in the server IP (10.0.0.5) and the password and remotely accessed the server

4) Using the VNC viewer on my laptop, I remotely launched VLC media player on the server. I then clicked on file-> open network stream, and set the address to udp://10.0.0.1 (Address of my laptop, where the files were located)

5) I launched VLC media player on my laptop, clicked on file -> open file

From the menu, I clicked on browse and selected a whole bunch of songs

I selected Stream/Save under Advanced Options, and in settings, selected UDP, and set address to 10.0.0.5 (Address of the server, where the files were to be played)

After this I pressed ok, and, the songs started playing on my stereo!

Using my laptop from anywhere in my house, I could remotely pause, play, forward, or change songs on the stereo.

Using VLC media player for Windows CE /Pocket PC, I can stream music from my HP iPAQ as well!

The second way

is to play songs locally stored on the server, by remotely accessing the server from another device.

The following are the steps I followed to accomplish this

1) I launched the VNC viewer on my laptop, and accessed the server as mentioned earlier

2) After launching VLC media player on the server, I clicked Settings -> Add Interface -> Web Interface

Enabling the web interface allows any device on the network to go to http://10.0.0.5:8080, and remotely control the music from there

Of course, I could have just used the VNC viewer to remotely control VLC media player, but enabling the web interface allows any device with wi-fi and a web browser to control the player. Therefore, even if a cell phone with wi-fi does not have a VNC viewer, it can use its browser to access the controls of VLC media player, and remotely control the music being played on the server.

Now you can use your handheld devices to control the music being played on your stereo system!

I hope this guide was helpful. If you run into any problems while setting this up, feel free to email me at hammadnaseem@gmail.com, with the subject “Wireless Stereo Help”.

NOTE: Anywhere in this guide, the word ‘server’ refers to the Dell computer

For more Free Information visit Universal Remote Codes Rca

“192.168.2.1” as a Default Address

This is a common IP address that several home networks utilize to institute a default gateway. The attributes of private IP is that, they could be utilized over and over again as long as they’re on dissimilar networks. It must be noted that private Internet Protocol addresses are non-routable; only 1 device at a time on a network should utilize this Internet Protocol address to prevent from IP address conflicts.

The Function of the IP Address

All PCs have Internet Protocol addresses. These are utilized by servers or networks in order for identification. This particular address belong to IPv4 private line category. This line is recently being utilized by Belkin for broadband routers. If you check the homepage for its router, it is the installed default IP address.

How it Works for Networks and Routers

Since it is the default address in routers, it becomes standard by which data is processed. 192.168.2.1 address operates with networks and routers in multifaceted ways.

The simplest way to describe it would be, “it holds data”. For instance, info is requested from the Internet. When this request is sent, the IP address operates with the nodes to assist the action.

Changing the Settings

It is easy to change usernames or passwords. Simply log in to the homepage and do the alterations. Apart from user accounts, it is as well possible to alter many other functions. If you are on a network, you could also change the modem, DSL and any other settings  of communications.

Troubleshooting

There are some problems that you may run into. If you apply LinkSys application and forgot the password, you could reset your broadband router. If you encounter problems in your connections, proceed to “My Network Places”. Find properties in the TCP/IP or LAN. These are the things to check if you run into problems with your connections.

Other problems could be attributed with firewalls. The actions of the Address and the router or the network could be affected by firewalls.

Internet Protocol

TheInternet Protocol (IP) is the basis upon which all other Internet protocols operate. IP provides the basic mechanism for the forwarding of data between two computers on separate networks. IP can also fragment packets it they are too large for some older networks to forward, but this feature is largely obsolete because all routers built in the past decade are able t pass large IP packets.

IP pickets are simply handed from computer to computer until they reach their destination. The computer sending the packet and the computer receiving
the packet are called end systems because they are at the ends of the communication on session. The computers between the end systems are called intermediate systems. Intermediate system is a generic and more theoretical term for computers more commonly called routers, gateways, or multihomed hosts.

Router usually refers to specially designed computers optimized for routing packets.
Gateway refers to general-purpose computers that are simply used as routers and perform no other function.
Multihomed host refers to general-purpose computers that perform some other function in addition to routing packets such as file service or Internet site hosting.

The term host is commonly used in the UNIX and Internet communities to
mean any computer (client, server, or peer) that is directly attached to the Internet.

Services of IP
IP provides the functions of addressing and fragmentation only to support
packet forwarding; it does not presume or implement any other functionality.

• IP cannot guarantee that a packet will reach its destination.
• IP has no ability to perform flow control.
• IP performs no error correction.
• IP performs no error detection for the data payload.
• IP does not guarantee that packets will arrive in order and does not order them sequentially.

IP relies on the data link to transmit data in an error-free condition and
does not attempt to provide any guarantees of service. Other protocols, which are transported within IP packets, add information such as packet serial numbers and error-correction codes. The destination system can check to see if all the packets have arrived, arrange them in the correct order, and request that

any missing packets be sent again based on this additional information. TCP performs all these functions, as explained in the next section.
IP treats each packet as an independent entity, unrelated to any other packet being transmitted. IP does not have logical or virtual connections, circuits, sockets, or any other mechanism to provide associations between packets. These functions are all provided by higher (or occasionally lower) level protocols.
IP does not perform error correction. IP does, however, implement limited error checking to verify that the header information is correct; damaged header information could result in the packet being forwarded to the wrong address. If, at any time, a router on the path between the sending computer and the receiving computer detects that an IP packet’s address header has become damaged (by comparing the header with the header’s checksum), the router will simply discard the packet without notification of any kind. Again, higher- level protocols will determine what data is missing and generate a request for retransmission. This header checksum does not detect errors that may have crept into the data portion of the packet; that function also is the responsibility of higher-level protocols.
IP does include information about how long a packet should remain “alive” in a system. Every IP packet contains a time-to-live indicator and decreases this counter by one each time a router forwards the packet or whenever one second of real time elapses. The time-to-live counter usually starts at 64, 128, or 255. When a packet’s time-to-live counter reaches zero, the packet is discarded.
This event can occur in three (rare) cases:
• When the network is too busy to forward packets in a timely manner
• When a circular route exists and packets are simply being passed around it
• When the route between two computers is simply too long to he useful
In all three cases, the route is not usable so communications should not continue.