Need Help: How is computer formated data converted into network packets?

For months now Ive been studying the process of the Open Systems Interconnection (OSI) model / layers. As well as reading Dr. Comers book on "Internet working with TCP / IP; principles,protocols, and architecture." But with all of my readings I spawned another topic of interest. The packet. Not so much how it travels, I get that. But Ive been trying to learn how the computer actualy constructs the packet. From a url in a browser to a packet on the wire.

Ive found articles that explain how a packet is processed in memory.

http://www.patentstorm.us/patents/7185153/description.html

But Im failing to come up with the correct keywords. To pull up an article on how a computer literaly takes a url request and turns the data into a packet.

Ive tried keyword searches in google like:

-Begining+packet+assembly -how computers convert data into packets -how computers create data packets -how browser related data is converted into packets

Hundreds more to follow those in different variations as well as new.

Im looking to learn this topic at the machine level step by step. What am I doing wrong with my search phrases?

Neqtan

The term that will help you more than "packet" would be "datagram", which is considered synonymous to packet but refers specifically to encapsulated network traffic. When a datagram is constructed, it steps down through the OSI model (from the Application layer) and each layer wraps the original information in specifics that will help it to reach its destination properly. When it reaches the destination network, it works its way back up from the Physical layer to the Application layer, stripping off the wrappings from each layer as the information is used to route the traffic to the proper destination. Also, it's important to note that network traffic is often segmented into multiple transmissions due to the size of the transmission. These segments are kept in order via a series of sequence IDs that enable the destination to piece together the original transmission (hence, the usefulness of connection-oriented TCP connections).

Anyways, that should be a good start. Let me know if you have any more questions.

Zephyr_Pure wrote: The term that will help you more than "packet" would be "datagram", which is considered synonymous to packet but refers specifically to encapsulated network traffic.

This is true. I knew that much as well. I have read that about datagrams. I also found that packets can be known as TCP Segments / Fragments, and ATM Cells. Theres so many different writers that use these terms loosely in different refferences. Ive seen datagram encapsulation reffered towards network traffic as well as packet encapsulation. Thanks for the clarification on this.

When a datagram is constructed, it steps down through the OSI model (from the Application layer) and each layer wraps the original information in specifics that will help it to reach its destination properly. When it reaches the destination network, it works its way back up from the Physical layer to the Application layer, stripping off the wrappings from each layer as the information is used to route the traffic to the proper destination. Also, it's important to note that network traffic is often segmented into multiple transmissions due to the size of the transmission. These segments are kept in order via a series of sequence IDs that enable the destination to piece together the original transmission (hence, the usefulness of connection-oriented TCP connections).

As to your nice breif description of how OSI works thank you. But again i have read that information already. I have even read through the description of how a url is processed through the OSI layers down the stack and out onto the wire. One article gos into great detail about how the get request is first sent to the root dns server back to the browser back to a level 1 dns server according to its type. Then back to the browser with the specific dns server that hosts the url out again to this specific server to obtain the IP address to begin the web page download.

Resources (Ive read every detail at each of these links): (The first one below is what i was quoting above) http://computer.howstuffworks.com/internet-infrastructure8.htm http://janeataylor.wordpress.com/2006/01/13/the-osi-model/ http://www.geocities.com/SiliconValley/Monitor/3131/ne/osimodel.html http://computer.howstuffworks.com/osi.htm

Anyways, that should be a good start. Let me know if you have any more questions.

I was actualy looking to find out exactly what the machine does with the url get request to turn it into a packet and send it to the first hop. Even if this took understanding machine language or what ever else i needed to know to fully get it.

I appreciate your feedback. If theres anything anyone can add to this im all ears.

Neqtan

Neqtan wrote: I was actualy looking to find out exactly what the machine does with the url get request to turn it into a packet and send it to the first hop.

Well, if none of that helped, then I'm not sure you'll find more specific detail into the particular situation you're inquiring about in articles or anything of that sort. You may just have to do your own research with crafted GET requests and Wireshark. We'll see what others come up with, though, I guess.

Well i wouldnt say none of it helped. Your clarification on datagrams could be crucial to better key word searches.

I just need to figure out how to find articles that explain how the computer / machine physicaly converts the formating / language of the application language into datagram formating / language.

Ill keep digging until something pops up. Thanks again for your help.

Neqtan