A Little frustrated with TCP/IP Protocols and Their Functions

fyrehawg

I'm a little frustrated. It seems everywhere I look they are named differently or grouped differently. Example...I've seen Layer 1 referred to as the Network Access Layer...Network Interface Layer.. Physical Layer...Hardware Layer...and Link and Physical Layer..etc. Same at level 2.. Data Link Layer... Internet Layer...IP Layer....and so on for each layer. I understand I need to understand the layers and what functions happen at each layer but it's kind of throwing me. It seems like there are several excepted ways to refer to it. What I need to know is what is the Network+ test gonna call for? Anyone else having this problem. I mean...I understand it and whats happening..but it seems like the correct answer is gonna depend on who's asking??

instant000

PDNTSPA

Please
Do
Not
Take
Sausage
Pizza
Away

^^ Stole this one from my wife.

Physical
Data-Link
Network
Transport
Session
Presentation
Application

There you go!

Here's a handy reference: The TCP/IP Guide - OSI Reference Model Layer Summary

fyrehawg

Thanks instant000....I understand the OSI Model...I remembered it the same way. LOL...Where Im having trouble is how the TCP/IP Layers relate to the OSI model. For example.. One source I see relates the Application Layer of TCP/IP to the Application, Presentation and Session Layer of OSI.. Next Transport to Transport...Next Internet to Network.. Next Network Access to Data Link and Physical.. some references relate these different layers differently.... On the TCP/IP I see some teaching it as having 4 layers ..some as having 5 layers and the way they correspond it to the OSI Model is different from place to place and they use different terminology. Example....I just googled it and very quickly I see three different places refer to Layer one of TCP/IP referred to as the Physical Layer, Hardware Layer and Network Access Layer. Some call layer 3 the Network Layer...some the Internet Layer. Which is correct for testing purposes?

FloOz

The are two different models. The OSI and the TCP/IP. 4 Layers of the TCP/IP Model

fyrehawg

Yes..I understand that. But I'm seeing many different TCP/IP Models. Some look like the one you just posted. Some have 5 layers versus 4. Some calling the same layers different things. The OSI is always the same...but the TCP/IP seems to vary depending on where you are looking. Here its explained in 5 layers. Computer and Communication Networks > Foundation of Networking Protocols > 5-Layer TCP/IP Model - Pg. : Safari Books Online

fyrehawg

This is what's throwing me...the TCP/IP protocol suite and which level things like ARP,RARP,PPP,SLIP etc. operate on differs according to whether or not your looking at a 5 layer or 4 layer TCP/IP model and what that particular model calls Level 2 etc. ( I hope Im making sense) Im trying to figure out which model to memorize and learn for the exam being there are a couple different ways its explained out there.

TechGuru80

fyrehawg wrote: »

This is what's throwing me...the TCP/IP protocol suite and which level things like ARP,RARP,PPP,SLIP etc. operate on differs according to whether or not your looking at a 5 layer or 4 layer TCP/IP model and what that particular model calls Level 2 etc. ( I hope Im making sense) Im trying to figure out which model to memorize and learn for the exam being there are a couple different ways its explained out there.

So here is a comparison...

=====
OSI

---

Application (ports so SMTP, POP3 etc.)
Presentation (SSL...things like encryption/decryption etc.)
Session (protocols)
Transport (TCP/UDP)
Network (IP routing)
Data Link (Switching ... MAC addresses)
Physical (cords, cards, transmitting bits)

======
TCP/IP (old)

---

Application (Application & Presentation & Session -- 7/6/5)
Transport (Transport - 4)
Internet (Network - 3)
Network Interface (Data Link & Physical -- 2 & 1)

The only difference between the old TCP/IP (4 layer) and the new (5 layer) is that instead of internet and network interface, you have network, data link, and physical just like in the OSI model.

fyrehawg

OK!!!! Thank you sooo much. That explains it. I wasn't aware there was an old and new model. I was just seeing two different models and it was throwing me off. I was seeing it two different ways and assuming it would throw a lot of things off when being asked what layer different protocols operate at. So is it safe to say that the new N10-005 test will expect me to know it as it relates to the 5 layer model? Thanks so much for the help.

YFZblu

TechGuru80 wrote: »

======
TCP/IP (old)

---

The only difference between the old TCP/IP (4 layer) and the new (5 layer)

I don't think it's necessary to refer to one model as 'old' and one as 'new'. IMO a more accurate way of separating the two would be like this:

OSI = Theory
TCP/IP = Implementation

For example it is generally accepted that you refer to the OSI model when talking about "layers" - ex: HTTP would be referred to as a layer 7 protocol in conversation.

Slowhand

There are lots and lots of diagrams out there to help you remember not only how the two models relate, but also what they do. These two are examples of results from a Google search of "OSI vs TCP IP models". Just remember that the TCP/IP model is also known as the DoD model, and you're on the right track.

TechGuru80

YFZblu wrote: »

I don't think it's necessary to refer to one model as 'old' and one as 'new'. IMO a more accurate way of separating the two would be like this:

OSI = Theory
TCP/IP = Implementation

For example it is generally accepted that you refer to the OSI model when talking about "layers" - ex: HTTP would be referred to as a layer 7 protocol in conversation.

I did not mean old as in old compared to OSI, I meant old as in the five layer TCP/IP is really the newer way to use. I do agree with theory vs implementation.

fyrehawg

Thanks for clearing it up for me! I def have a better understanding.

SteveFT

Glad you got the help needed. From the book I'm reading (Meyers), the OSI model is concrete. We all learn it the same way. This is not the case with TCP/IP model. There are no set in stone rules of what each layer is called, or even how many layers there are. If you're studying for Network+, make sure you learn what CompTIA thinks by checking the objectives. Beyond that, I really don't think it matters out in the field as long as it helps you understand how everything works together.

Darril

Lots of great information here and the graphics from SlowHand are perfect. SteveFT has good advice here too about "checking the objectives."

If you look at the N10-005 objectives, they list it as a four layer model and also list different names for layer 1:

Network Interface (Or Link Layer)
Internet layer
Transport layer
Application layer

If you learn the OSI model and can draw the first diagram SlowHand posted, you'll have all you need to know for the Network+ exam.

Good luck.