Packet data breakdown

[Orangeb]

Hi,
I have been going back to basics.
IF a packet header contains all the protocols - IP, TCP, UDP, HTTP, and I have been told it only needs one of these, then what happens if HTTP is selected? Because thats only application data, really? Web browser etc. Or can it work with 2, or is that the whole point of the stack idea? I have been trying to find a visual breakdown of a packet header thats not too complicated.
Maybe I just overthink stuff too much,
Thanks for reading,
Matthew.

 

[Orangeb]

I think what I mean is, the 2 models OSI and TCP/IP, show what gets sent etc, but I wanna look inside a packet. I know a packet goes in layer 3 of the OSI - but I need to know more about the packets protocols, how it is divided up, when it comes to the TCP UDP HTTP etc. What is selected with regards to that part. The explanations on the net are confusing a lot of the time.

 

[VersionMonkey]

Keep in mind that the OSI 7-layer model is largely theoretical (there have been implementations, but they never took off and none are in use any more). You should use it only as a very rough guide as to where you are in a network stack, how any given part of the stack might behave and how different aspects of the stack might interact with each other.

The family of Internet Protocols don't cleanly map onto the OSI model because they have been developed independently, often without any reference to the OSI model.

I think what I mean is, the 2 models OSI and TCP/IP

NO. The OSI 7-layer model, is an academic model - it doesn't exist as an implementation. TCP/IP is a pair of related protocols.



Even though you will often see reference to one protocol running "on top" of another (and images of the OSI "layer" model reinforces that), a packet is actually just a string of bytes.

The lower "layer" protocol headers come first in the string and will be unpacked by that layer, the rest of the packet is just "data" to that layer and that part will be passed on to the next "layer" to be interpreted appropriately.

IP, TCP, UDP, HTTP, and I have been told it only needs one of these

An "http packet" will have an IP header, a TCP header and then an HTTP header; one after the other in the packet. All will always be present in the packet.

I have been trying to find a visual breakdown of a packet header thats not too complicated.

This page https://en.wikipedia.org/wiki/Encapsulation_(networking) has a simple diagram showing how each header is encapsulated to make up a packet.

There's a whole bunch here: https://duckduckgo.com/?q=tcp+packet+encapsulation&t=h_&iar=images&start=1&iax=images&ia=images of varying complexity.

 

[Worthy]

Last warning, please stop creating new threads for this and use one of your existing ones.