The OSI Model Demystified 

1.Please (Physical Layer) 2.Do (Data Link Layer) 3.Not (Network Layer) 4.Throw (Transport Layer) 5.Sausage (Session Layer) 6.Pizza (Presentation Layer) 7.Away (Application Layer)

10 years old and still a great video. Greatness really does stand the test of time.

I think most errors occur on layer 8. The user.

For anyone trying not to read the book I think it's important to point this out. The top, or seventh, layer of the OSI model is the Application layer. Contrary to what its name implies, the Application layer does not include software programs, such as Microsoft Word or Firefox. Instead, the Application layer facilitates communication between such programs and lower-layer network services. A better example would be the HTTP protocol which sends your request from the client's browser to the server. The presentation layer being explained as " The OS " is not satisfactory in any way. The presentation layer is better thought of as an interpretation between computers for sending images or video. Video compression like divx fall into this layer. The presentation layer interprets content transmitted within the HTTP response from the application layer.

I understood more in 18 minutes than watching two 1 hour videos and reading network fundamentals! Thanks!!

Please (Physical Layer) Do (Data Link Layer) Not (Network Layer) Tell (Transport Layer) secret (Session Layer) Password (Presentation Layer) Anyone ( Application Layer )

I’m studying for my CISSP cert and listening to this 18min video, really helped tie together the 200+ pages of information I had to read. Thanks for breaking this down.

Eli, thank you is not even close, you're rocking and I still comeback to your videos to refresh my information and learn, thank you so much again and again.

a - application priest - presentation saw - session two = transport nuns = network doing = data link layer pushups = physical layer

Loving how you enunciate EVERY word you say to make sure it's spoken and heard clear, thank you for making it easier for us to understand!!!

I took three courses talking about ISO layers and never understood them, but today because of you I understood them and i will never forget them. you gave me something for life . . Thank you sooooooo much

"As one senior network administrator told me, 95% of all networking problems are Layer 1 problems. Basically, somebody unplugged the damn cable." I lost the next minute laughing.

I remember by the phrase "Please Do Not Tell Sales People Anything", which is a fact that any tech will know and stick to :)

I like how you go over it like...3 times. I needed that.

12 years later, still relevant.. the best explanation ever

Man I am not a native english speaker, but you speak as good that I understood at first time, rather than I was wasting my time reading on internet, thank you very much

That Computer Guy is best of the best, i love his video and how he is able to describe and explain all around in so simple way.

Actually the Transport Layer (layer 4) is where TCP and UDP protocols live. It's very important and involves whether connections even need to be established/terminated and whether data arrives in sequence or is error checked (CRC checksums). Also, from a more pure communications perspective, encryption/decryption happens at the Presentation Layer (Layer 6). So layer 6 is a much broader concept than an OS on a corporate laptop.

Eli is the kind of bloke who can explain quantum mechanics 3 times in 18 minutes, and everything becomes clear. Some people can be geniuses, but very few have the skills needed to transmit their knowledge. Your video made me stop my fear that I'll never be able to understand and learn a new profession that will change my life for the best. I realised that I could do it. Thank you very much.

You just explained this better in

I like these videos. Easy to understand, no music in the background and Eli isn't a d-bag so I can sit through the whole thing

Physical Data Link Network(s) Transport Session Presentation(s) (to) Application(s) thank you Eli for your amazing classes, This is exactly the information I was looking for

Software and Network Engineer here! The Application Layer is (to use a development term) an abstraction layer. An abstraction layer hides the intricacies of the lower layers from "applications". It provides a set of rules (Application Program Interface) for accessing services from the lower layers.

I wasn't sold on this model's usefulness until Eli said "very, very, very, very, very, very useful".

This is the only explanation of the 7 layer model I have ever heard that actually makes sense. Thanks!

Wow... I wish this quality education was available to me 10 Years back. Hats off to you Sir. heartfelt regards...

You are more a specialist in any of the topic or field of IT you choose to teach... we love you sir and more GRACE.

when my networking teacher asks the class a question and no one answers, she looks at us and reacts like we've been studying this for years. We're only going on week 6! thanks for you're videos, very helpful!

In the Network+ Guide to Networks Sixth Edition it is explicitly stated that the application layer does not include software programs such as Microsoft Word or Firefox (pg. 44 Ch. 2). Rather it contains protocols that interact with such programs. For example HTTP.

Please Do Not Teach Students Pointless Acronyms

Very well done. I've been doing IT for over 20 years and have found that not many can easily and logically help you understand the OSI model, and how to use it to troubleshoot. Troubleshooting isn't an art, its a skill based on a logical approach.

Thank you so so much!!!! I understood nothing after sitting in class for 5 hours for this stuff and fighting hard to stay awake and focused. I came home feeling dumb and defeated. You made it so much clearer than my teacher!!!! Thank you, Sir.

@14:45 "Some 12 year old can't get onto the Pokemon website" Nobody saw the Pokemon invasion coming...

This video really helped! I need to learn this to get my CompTIA certification and now I've pretty much got the basics down in 20 minutes!

this is why older videos actually try to teach us stuff, instead of just clout, pretty colors and graphs. thank you for this

ELI !!! you are the reason i graduated !! Thx so much for all the info you gave !!!!

Hi Eli, I totally agree with your view that: "... understanding the way modern networks are implemented based on a layered approach that follows the OSI model is very helpful." and "....understanding the key functions and services at each layer helps design, manage and trouble shoot issues" is a solid approach to diagnosing problems/trouble shooting network issues. But I do take issue with how you represented some of the functions and services and also disagree with your statement that an IT - networking persons do not deal with the functions of layers 4 through 6 in operating, designing and diagnosing networks. Some of my observations below and please take my comments as additional information not criticism. Steve Arnold Fellow network architect, engineer and educator ------------------------------------------------------------------------------------------------------------------------- Application Layer is not where application programs are - this layer expose protocols (rule sets) as a set of APIs and services that are used by applications and operating system to interaction across a network. For example your web browser may be working perfectly - but not able to find servers on the internet by name. No amount of exiting/starting Firefox is going to fix it, because the DNS service or host name table is corrupt - which IS a layer 7 exposed service and may require stopping and starting the DNS service. Presentation Layer in general normalizes data (symbols, syntax, semantics) representation between programs/devices that are not the same. Such as a computer with an ASCII symbol set interacting with a computer with an EBCDIC symbols. For example you are doing file transfers between computers and the data is being corrupted because the presentation layer which has an ASCII symbol table does not have the proper extension symbols loaded. Session Layer deals with application oriented event sequences and synchronization. For example think about a program opening a file and reading data needs to synchronize these events with a file server that is actually controlling the file system across a network. It is also where single/multi-threading of program to program sessions is managed and you did cover one of the key issues which is the number of allowable sessions for a server, though there are other key network issues such as database locks that do not clear or remote procedures that hang which manifest at this layer. These days the above 3 layers are typically implemented as Application Protocols as vetted and published by the IETF (Internet Standards Group) and are melded into a single "uber-layer". Examples such as HTTP, SMTP, NNTP, and so on. BUT they are not application programs. They are services invoked by application programs such as Firefox, Outlook, News Readers and so on. Yes layer 4 - transport deals with size and flow (windowing), but I believe you missed covering some major elements of transport around QOS quality of service, MTU - maximum transmission unit size, ports - especially well known port numbers used for firewall, security and some tunneling activities. All of which are key networking items. And layer 4 will continue to grow in network operation/design/trouble shooting as more voice and video traffic moves to using the OSI/IETF model for communications. I have not watched your ARP video yet - but hope it makes the connection - no pun intended between resolving the layer 2 addresses with the layer 3 addresses and I typically see this as a layer 3 networking issue not a layer 2 issue as you state. Given I can run a layer 2 physical network without the need for ARP (i.e. NETBIOS networks) but the inverse is not true for a layer 3 - IPv4 network. Last heartburn is on the statement that the physical layer is the "wiring". I get where you are coming from in that the physical environment is many times manifested as problems/symptoms in layer 1. The physical layer is the attachment point for the device/appliance to encode/decode information into/from the media. And that media can be wire as you state but is also very much wireless these days. BUT the physical layer along with the link layer is much more than that. It deals with things like sharing the media - which has major performance implications. Connection management which is key to things like pairing, access point issues and mobility such as with smartphones. And baseband/broadband/multiplexing and compression functions which again are in the physical layer not the wire and do need to be addressed as an IT/networking person. additional references; en.wikipedia.org/wiki/OSI_model www.escotal.com/osilayer.html www.texbuddy.com/OSI.htm (note they use generic terms for protocols in layer 7 - not to be confused as application programs them self)

CHARLIE..........YOU'RE INDEED A GENIUS. THIS IS THE TYPE OF TUTOR I'M LOOKING FOR. STRAIGHT TO THE POINT. GOD BLESS YOU

Eli, you really are an excellent teacher. I learned this stuff in the 80's by reading books, but would have had an infinitely easier time with it if you explained it. In those days we used 'All People Seem To Need Data Processing' to help remember the layer names. Again, kudos for such a quality lesson on the OSI Reference Model, and thank you.

Perfect. It has everything I was looking for. Brief explanation without getting too much into the details, examples of what each layer is, and simple pics. I can finally breathe easy.

In all his thumbnails he looks like a jail escapee

u bald headed beauty i love you! thank you so much for the help! :)

Thanks Eli...I am a big fan. My favourite statement for remembering the layers is this one: 1.Please (Physical Layer) 2.Do (Data Link Layer) 3.Not (Network Layer) 4.Throw (Transport Layer) 5.Sausage (Session Layer) 6.Pizza (Presentation Layer) 7.Away (Application Layer)

Hey Eli, I'm writing because I just want to thank you. You have seriously helped me with understanding so much! You cover tons of topics that I basically can't find any good tutorial or 'how to' topics that just aren't out there. I struggle with reading and learning this type of material. You provide me with visuals and explanations that really help me out and continue to help. Thank you very much

from up down: All People Seem To Need Data Processing from down up: Please Do Not Throw Susage Pizza Away

Skip to 2:35 for the actual start

I study for CCNA and watching Eli videos after reading each related chapter really locks that knowledge for me what no book can do! Thank you

understanding how to actually use the OSI provides a way to conceptualize nad logically troubleshoot mentally in scenarious, which i love, its a road map for us to use like a template

Tomorrow I'm taking a test on TCP/IP and OSI. If I pass, I'm subing.

thank God I have learned english, and thank You for this amaazing classes.. You're the best! Great work.

Appreciate you keeping this video available 11 years later :)

Hello ELI, you just killed it. In my past so many years of experience in the IT field, the OSI model has remained a terrified topic. But that is history. Now, after watching and learning from your informational video, i can confidently talk about OSI model to people. I like to thank you for putting so much effort in making this mammoth topic look like an ant...You rock!

You're awesome!!! I came here because Prof. Messer confused me. :)

Please (Physical Layer) Do (Data link Layer) Not (Network Layer) Throw (Transport Layer) Sweet (Session Layer) Pizza (Presentationl Layer) Away (Application Layer) nice tutorial @Eli

they taught us what the osi layer was , but never how to use it. finally someone with knowledge, thx pc guy

Great help buddy, the problem with IT Lecturers nowadays is they try to explain sooo much information in one class, a bit too much for the mind to consume so students forget. Thanks for making things straight to the point :)

I read this online and im a little bit confused.. it refers to the layer 7.. can someone help me? This is the closest layer to the end user. It provides the interface between the applications we use and the underlying layers. But notice that the programs you are using (like a web browser - IE, Firefox or Opera…) do not belong to Application layer. Telnet, FTP, email client (SMTP), HyperText Transfer Protocol (HTTP) are examples of Application layer.

this is the best explanation I have listened to so far. thanks a lot :)

I'm a non native english speaker and I can say your pronunciation is perfect. Zero effort understanding what you say :D Thank you!

Probably the best explenation out there about the ISO/OSI model since he gives you examples taken out from real life problems that could occur once in your career. Most explenation I viewed so far don't explain the model with so many easy to understand examples as this one. Nevertheless, when he wanted to keep this video as easy to understand as possible, I would like to add, which protocols are used on which layer: - Layer 7: HTTP, HTTPS, FTP - Layer 6: HTTP (...), SSL, TLS - Layer 5: HTTP, NetBIOS (...) and Sockets (for example a RDP session) - Layer 4: TCP, UDP, SPX - Layer 3: IP, IPsec, ICMP, RIP - Layer 2: PPP, ARP, MAC - Layer 1: Ethernet, FDDI, Token Ring

This one was very helpful.. I like the way you present the things.. Thank you Eli, The Computer guy.

simple yet very effective.

Oh..i can't thank you enough. i have exam tomorrow and the OSI model was really giving me a tough time. i understand it so much now and i am certain i'll be smiling if i see questions on OSI model tomorrow (i hope the prof. doesn't disappoint me by not adding questions on OSI) . Thanks Eli

Came here for my HCTM 420 System Integration and interoperability class recommended by my professor. Thanks, this was such a informative video.

There's only one level he forgot to mention. Level 8: The Matrix Layer.

OSI - All People Seem To Need Data Processing TCP-IP model - All This Is New Class dismissed :D

All (Application Layer) People (Presentation Layer) Seem (Session Layer) To (Transport Layer) Need (Network Layer) Data (Data-Link Layer) Processing (Physical Layer) This one helped me remember it.

Thanks Eli for your grate and helpfull videos. I'm 32 and I've been in IT jobs for 2-3 years and I watch your videos which are very informative and helpful. I really like your teaching approach. It is simple put complete. I can's see how some people can Dislike you videos! Keep up the good work.

Best Intro to OSI model ever!!

Can you release an intermediate video explaining the OSI model in more detail ?

I know this video is old, but man if your're not famous by now you should be, because of how well you present this model. I appreciate the time and commitment you took to make this video :)

Thank you for this video. I recently graduated from an EE program and this was such a better presentation to make a correlation between the technical vernacular the ACTUAL way things work. Your videos are invaluable and I can’t thank you enough for taking the time to make these videos as I’d imagine they are very time consuming.

I have a networking exam in a few days. I think I just found my futur husband.

very good video, he explains is very well.

You are seriously the best though Eli. I have watched hours long MVA networking courses and couldn't understand the OSI model, where you in the first 10 minutes made it extremely clear.

Starting New Technician job next month. This is great and never gets old! Eli is my bible right now in preparation.

brutal explanation

AKA the Seven Circles of Hell

I hope you teach somewhere the world needs talented teachers like yourself

After 11 years, your video still helps me to better understand the goddamn OSI-laysers than any other book stuff oder videos, big thanks!

Eli, You are the best tech instructor I've encountered. PLEASE continue making videos, and consider asking for donations. I would make one.

A person standing, typically never drinks pepsi. ;p

been procrastinating the Net+ for far too long. For the sake of knowing all the intricacies that is. This cleared up a lot. thank you!

I had to go back to this video to make this comment. about 10 months Ago, I was prepping up for an interview and I watched your videos related to networking. I got the job and was able to deliver the explanations well during the interview because of your vids. . Please make more of this on 2022.

Top down: A Priest Saw Two Nuns Doing Pushups

thank you very much.. i understand now.. 😀😀😀

A true gem to RU-vid and computer science are your videos. Your videos and teaching is just worth every minute and second of my time. I cant thank you enough for creating this channel. Amazing!

Am in 2024.....still loving the content that doesn't lose value 😊

Oh My God im so high right now ,but for some reason instead of watching trippy or funny videos i always watch networking videos......is there something wrong with me?

Please (Physical Layer) Do (Data Link Layer) Not (Network Layer) Teach (Transport Layer) sex (Session Layer) Predators (Presentation Layer)

Wow! this really helped. Been a web developer for years and was trying to grasp what these layers really are and this is 12 years old video. Thank you mr eli!!

I don't know what I would do without you, Eli.

:( why couldn't u be my teacher lol

All= Application People= Presentation Seem= Session To= Transport Need= Network Data= Data-link Processing= Physical

i respect this RED T SHIRT guy for his honest effort to trying aware me about OSI

I find that hearing examples of what can go wrong at each layer seems to be the best way to remember/learn this. I'd love to fins some troubleshooting videos where network admins actually go out finding and fixing 'layer' problems in a real environment. All the network videos on RU-vid seem to be just people talking about networks and showing graphic representations. That said, this is the best I've found so far! Thanks.. :-)

As a cable installer, I definitely did some layer 4 troubleshooting! But yeah, mostly physical, and occasionally network layer issues. Definitely a useful model, and a great explanation of it!

Great presentation and explanation. I am not a pro by any means, but I just want to clearify one little thing. The fuctionality of the session layer and the transport layer is similar to the extent that both set up some type of session or virtual connection for communication to take place. The difference is that protocols that work at the session layer set up connections between APPLICATIONS, whereas protocols that work at the transport layer set up connnection beween COMPUTER SYSTEMS. Great video!

Thanks! After two weeks of a classroom environment , this broke it down simply.

Eli, I would like to thank you so much for the many presentations put together free for our learning, "Incredible". It inspired me to start getting IT classes. This is what i term professionalism. The tone of voice is truly a mastery of the art of public speaking.The type of voice one will not get tired of listening to. Well Done