OSI Model Layer 5, 6, and 7 -- Session, Presentation, & Application Layers -- what they actually do

Plenty of attention is given to L1-L4 of the OSI model... but very little attention is given to the Session Layer, the Presentation Layer, and the Application layer (Layers 5, Layer 6, and Layer 7). That's led to a lot of bad information existing about these three errors. So I decided to create a video that explained how these three layers work, and how they contribute towards the goal of Networking: sending data between two computers.
This video can be considered a follow up to my first two videos on the OSI model:
OSI Model - Layer 1, Layer 2, Layer 3
• OSI Model: A Practical...
OSI Model - Layer 4, Layer 5/6/7, Encapsulation De-Encapsulation
• OSI Model: A Practical...
In addition, I highly recommend watching my last video before or after watching the OSI model Layer 5, 6, and 7 video:
• HTTP vs HTML: Unveilin...
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00:00 - Intro
00:42 - OSI Model, TCP IP Model, Four / Five / Seven layer models
02:00 - Layer 5 - Session Layer
04:06 - Session Layer Modern Example: HTTP Cookies
06:04 - Layer 6 - Presentation Layer
07:38 - Presentation Layer Modern Example: ASCII encoding
08:19 - Layer 7 - Application Layer
09:34 - HTTP vs FTP - protocols implement L5, L6, L7 independently
10:43 - Why L5-L7 are often combined?
11:14 - Networking Models - Layers of Abstraction
12:30 - pracnet.net/networking
----
If you want a full training series unpacking Networking Fundamentals and how Data moves through the Internet, check out Module 1 of the course which is available for free on KZbin:
• Networking Fundamentals
And if you enjoyed that series, consider the expanded course based on this series covering the full depth of Networking:
pracnet.net/networking

[@PracticalNetworking]

*The truth about the OSI Model* : In this above video describing Layers 5/6/7, and my previous videos describing Layers 1-4, I teach through various _responsibilities_ associated with each layer of the OSI model. The truth is, that is a bit of a simplification I use to explain how Networking works. *In reality, the OSI model has never been widely used in mainstream networking.* To understand my _real_ thoughts on the OSI model, check out this post: www.practicalnetworking.net/stand-alone/the-truth-about-the-osi-model/

[@sarthak-salunke]

❤

[@Guwapo77]

Broooo...I got a degree in Computer Networking and Cybersecurity and this video and the other videos explaining the OSI model were the best I have ever seen. I understand it better now than when I graduated.

[@PracticalNetworking]

Glad this take on it helped =). Thanks for the kind words.

[@scottspa74]

Hahaha, ed says, "before i let you go...", as if anyone ever wants him to stop teaching and illustrating. This guy does it like no one else.

[@mobinmollei1629]

I just finished this playlist man what a journey he deserves all the support in the world hope you continue this series

[@santoshkumar-dr4qg]

After 15 years of IT experience, I clearly understood layers 5 , 6 & 7 of OSI. Thank you so much for explaining it in such great detail. ❤

[@Kyngte1]

You are literally changing lives man. I’m more into cybersecurity but ik I have to know networking basics to understand my field. I had a vague understanding until coming across you. Now I’m questioning whether I want to do cyber or start in networking

[@identit2559]

Networking++ ;)

[@theintjengineer]

Same here, Dante😂

[@PracticalNetworking]

Join us! Come to the Dark side! ;) All jokes, aside, thanks for the kind comment. I'm thrilled you're enjoying this content and it's giving you an interest in Networking =)

[@nouhatamba9976]

you' re the best

[@VKGSD312]

I think you may be the reason I pass my cert exam. No one has ever explained networking so succinctly and practically. Ever. It’s like magic. Thank you.

[@guidowakker1551]

I have been struggling with 5 6 and 7. This finally made a picture in my head that makes sense. I don't understand why books make it so difficult. Thanks alot.

[@bbqconstruct9641]

Sensible, clear, and concise. Outstanding!

[@theintjengineer]

This Guy's so good I even get mind-blown by the Graphics themselves haha. Thanks, Ed. Greetings from Germany.

[@PracticalNetworking]

AI graphics are a game changer =)

[@4ycool337]

This is the clearest explanation I have ever heard on the topic. Thanks very much

[@ricksewick]

This is the best presentation of layers 5,6 and 7 that I've seen in all my years of being involved in networking. Great job Ed! Please continue your work. You are an outstanding educator.

[@PracticalNetworking]

Thanks Rick, glad you enjoyed it =)

[@alpadangy]

Why do I only know now, an explanation that is to the point and very clear and concise about something that is very complicated if learned by reading books?

[@Cyber.Panda.]

You sir are doing the lords work! Havent found a video yet that explains these three layers as you did.

[@PracticalNetworking]

[@sarvasaravanan8487]

Great lesson. You are a wonderful educator. Thrilled by your sessions, feeding my passion for Networking

[@kemomaynard5417]

Thanks for the networking lessons. You explain everything with such clarity that everyone can understand you. A true MASTER of your craft. I especially liked the subnetting and OSPF series.

[@adnaneafifi1450]

You always have a knack for connecting the dots and linking existing information with new ones. Thank you Ed ✨ -By the way I really liked your music intro and outro 👌🏻

[@PracticalNetworking]

[@scottspa74]

As always, great content, and excellent use of visuals to really drive the content home and make it seem almost tangible. There is so little material out there that attempts to define/clarify the session and presentation layer functionally and conceptually. Still really forward to the release of the full networking course, too 😊

[@meisme9566]

Thank you so much that I literally understood every single thing, keep making such quality contents!

[@jeytis72]

Awesome! I've never met anyone who can explain computer networking better than you. I now have a better understanding of what layer 5/6/7 and are really about. Keep up the good work. Thank you.

[@vliqhtekk]

finished the whole playlist and i can say thank u for making this, i recommend everyone who want to learn networking to watch the whole playlist like literally its super helpful

[@nitishkumar-sw3om]

Just amazing playlist. I learned a lot from this playlist of 15 videos.

[@user-tl6md8qo2i]

You are the Best! no one is explaining this as good as you, not even close. I have never truly understood the OSI model until I saw your explanation (and this is true not only for the OSI model)! thanks a lot!!!!

[@darryldsouza2220]

One more excellent presentation. I love the examples that you give and the simplicity of your explanation. That's what makes a topic easier to understand. Keep going ...!!!!

[@skwidfingaz]

Another video by you that is such a simple yet effective explination of Network theory. Thank you.

[@tjabon86]

I recently started a 2 years education in Cloud and IT-infrastructure, our first course which we soon will finish is "Networking Fundamentals". The teacher is not a teacher, he have been in the industry for a long time though so he sits on a lot of knowledge, but he is not educational. So looking at your lessons makes it much more easier to get the hold of everything, since there is so much information to process in my brain. Thank you!

[@PracticalNetworking]

Thanks for the kind words ;). Glad this series is helping you understand a clearer picture of Networking.

[@aafif5607]

hey man wake up! PracNet uploaded a new video !

[@PracticalNetworking]

[@Username-hb1qi]

Thank you for this one and all your awesome videos that explain the content like this one for the OSI model so well!

[@clobbleglobble7501]

Great lesson. I went through every minutes of the video. I will repeat three times myself.

[@davidwood6792]

I just wanted to thank you for all this free content on your channel. You are awesome

[@yusso3762]

this whole series was actually so easy to understand thank you so much, i like have no prior knowledge of this and kind of understood this perfectly. the only thing im really curios that i cant understand is how a modem or my isp works and how they fit into all of this

[@mblackonline1059]

Very helpful info! Definitely had trouble finding good info on these layers as I studied for the Network+. Thanks giving these layers some attention!

[@PracticalNetworking]

Glad this helped bring clarity to these layers =) Cheers!

[@BekoIQ]

You focus on things that not everyone focus on it , great video

[@PracticalNetworking]

Thank you =)

[@DeRizzlo]

Clearest explanation on these layers, directly stating the main functionality and purpose instead of beating around the bush. If you are not super into networking as a profession, but someone from tech, this video is all you need to understand application layer of OSI model very well. Thanks for this lesson!

[@claudiomezza8162]

Thank you very much! I can't wait to watch your next videos and the full course. Your work is invaluable.

[@aireddy]

Ed you made it super easy to understand basics of networking fundamentals.

[@PracticalNetworking]

[@kaaiff]

How beautifully you taught all of the networking processes ❤ its just simply amazing. Just keeps uploading such videos to help us get there…thanks alot❤

[@mrnobody-oh1px]

you're the best. KZbin should make it possible to like each part of your videos separately.

[@PracticalNetworking]

Ha, I love it. I wish =)

[@DarVilZ]

Awesome, I am software engineer, I studied OSI model in university but your videos make much more sense. Thank you!

[@PracticalNetworking]

Glad to help!

[@aduragbemiodubela]

Thank you for this detailed explanation. Currently learning cybersecurity on Coursera, your videos have been very helpful to butress the lessons on Networking.

[@katout75]

Your video's are excellent, they're the best at conveying the details of networking in a easy to understand way. I recommend them to anyone wanting to learn/understand networking protocols from simple to complex

[@PracticalNetworking]

Thank you for the kind words and for your support =)

[@KRICHAN_Technologies]

Hi Ed... How much hardwork you did to understand this level of detailed information and we are echoing your hardwork. Wonderful explanation and i will make sure watch all your upcoming videos. Thank you very much ❤

[@18mellow]

Another excellent series. Thank you very much. I have one small request, please do dns deep dive series.

[@kelpkelp5252]

Thanks. Those layers have always been a bit of a mystery to me. Excellent explanation.

[@PracticalNetworking]

Glad you enjoyed this take =)

[@dustcore]

Great video and explanation once again.

[@holywhitebeard987]

Hey ED! Thanks for turning on the lightbulb my man!👨‍🎓

[@alfredoneto4381]

Amazing as always!🎉

[@justsomebody14]

Just watched your tcp/udp, networking fundamentals and nat courses and now this! Thank you so much!❤

[@PracticalNetworking]

You're so welcome!

[@justcurious1940]

Great video as always 🙂.

[@RsGenjil]

Amazing content and channel, thanks!

[@mugishadavid5938]

Thanks for these great lessons.

[@mohammedanwarsayeed]

You heard my voice Tadaaaa......revelation of the hidden part, thanks a lot man

[@CEBMANURBHAVARYA]

the best video for understanding networking, You are really good .

[@engr.nafisfuad]

I am grateful beyond words.

[@sayedazizullahsadaat]

Great content, Thank you so much.

[@khurramaziz2430]

Awesome videos as always 🎉 Please make a video series on IPv6 subnetting, like your IPv4 ones.

[@PracticalNetworking]

Thank you! Yes! IPv6 Subnetting is on my list =). Would love to show people the trick I use for IPv6 subnetting =)

[@shujauttali2608]

You are always with different content, watching your videos should be made mandatory for all network engineers 😅

[@rochuolmos]

By far the best for explaining Networking. You should make videos of BGP or Quality of Service! It would be greatly appreciated it. THANKS a lot for your content

[@cpthermes3703]

very nice series. Loved it :D

[@Altezza124]

Great video. I love the content.

[@IliyaDamyanov]

No one else explained it like you.

[@qrrrrrp]

Thank your so much everything changed in my mined!

[@user-le7ve4rb9b]

Hey, when will you release the entire networking course in your platform?

[@kilermatch5121]

Thank you so so much..... It's something in core.....

[@Sudqi55]

Thank you, great Video

[@26floydlobo26]

Just awesome ❤

[@Sageibmk]

Great teaching

[@FragileEgo]

Love this channel!

[@PracticalNetworking]

Thank you kindly =)

[@akpanedidiongemmanuel7224]

Thank you a lot, PracNet.

[@leetanizer]

Thanks for this video 🎉

[@PracticalNetworking]

You're very welcome!

[@castle4757]

Great video ❤...Can u tell us what are the topics you are going to cover or content of your upcoming course 'Networking The Internet The Cloud and everything in between ' ? I am interested.

[@PracticalNetworking]

Thank you! I'm aggregating people's responses and requests for the perfect networking course. Now that I'm done with this video, I am going to sort through all the data and put together a curriculum lesson plan. Expect more information in the next few weeks.

[@njaneardude]

I've always been, layers 5,6 and 7? Kinda like IT's MNOP, just lump them together and forget about it. You can ping the host?! You're halfway there 😂 This was very interesting and enlightening 👍👍👍

[@user-tl6md8qo2i]

What subjects are you teaching in your course? what the difference from the free version on KZbin?

[@MakeItWork256]

Great video! I've written together a small text about the OSI model. Layer 1: Physical Layer (Transporting bits) The physical layer includes everything on a physical level for networking. Wires, hubs. When you send data, the physical layer is the one actually responsible for it. Layer 2: Data Link (hop to hop) The data link layer is responsible for adding a MAC adress onto the data. It also includes ARP. MAC adress is important to find out which host exactly was meant, inside of a local network. Switches are also in layer 2 since they use MAC adresses to transfer data within a local network. If we don't know the MAC adress, we use the ARC protocol to find it out. MAC adresses (sender, destination) are updated with each hop based on what the router thinks should be the next router (using the IP adress / layer 3) Layer 3: Network (end to end) The Network layer introduces the IP protocol. IP is used to gurantee end to end delivery meaning that we go from start (your pc) to end (goal). As stated in layer 2, while MAC adresses change with each hop, IP adresses stay the same. MAC uses IP to determine the next hop onto the next router. Once you reach the last router, IP is used to find the exact computer you want to send data to. Layer 3 includes Router's since they work directly with IP. Layer 3 also inlcudes IPv4/v6. Layer 4: Transport (service to service) Layer 4 add's it's own header that uses a dynamically generated port number (source port) to receive the data. TCP or UDP can be used as a way to transport that data. The server we spoke to will only send data to that source port with either tcp or UDP. A little bit like port forwarding but directly on your computer. You forward data to a specific application depending on the port. If an application on my computer reserves the port 2343 then it cannot be used by any other application on my computer, but can still be used by any other host on my network. In the most basic sense, port's are there so we can redirect data to the correct application (or host with port forwarding). Layer 5 (5, 6, 7): Application Layer 5 is made up of three "layers" (at this point it's one big layer). The session layer, the Presentation layer and the application layer. The session layer was used in old mainframe computer's to differentiate 2 users (not important anymore) but is used today with HTTP. When you change your IP adress, you should loose access to everything, right? Nope. HTTP saves cookies on your device (it's like local storage for servers). As you know, all the data is displayed in 0 and 1. Problem is, how do we group them together? 1111 1111 1111 1111 like this (4 bits together) or 11111111 11111111 like this (8 bits together)? Even though they are the same numbers, depending on how they are displayed things change. The presentation layer has to take care of that. These days HTTP makes it so that they are read per byte as a different ASCII character. It does depend on the application itself, how they manage it. The application layer determines what the interpreted characters do (application commands like GET PUSH and so on). We also use HTTP for this. HTTP has it's own set of application commands that the application (our browsers) use. As you can see, all three of these use HTTP to do their bidding. This is the reason why newer models just group the three last layers into one big layer. The "application" layer. Would appreciate it a lot if you could tell me if anything I said is wrong. Either way, great tutorials!

[@EdemRobin]

Nice job.

[@seantellsit1431]

Doing the work of superman!

[@PracticalNetworking]

[@mikgruff]

Thank you!!

[@hiwotassefa3143]

Thank You !

[@somebody3014]

btw if you guys don't know this guy has a course on networking link is in the description

[@salimzenzouni]

You're a genius!

[@DrawMeAParadox]

Hello Ed! First of all, thank you very much for the videos you make, they really help me to understand the concepts of networking. I would like to ask you about the complete course: will it be available soon? I can't wait to buy it and continue learning the following networking topics :) Thanks a lot!

[@PracticalNetworking]

I've had a few set backs in life, but definitely plan to complete the course.

[@DrawMeAParadox]

🙏@@PracticalNetworking

[@logicwonder]

Nice way of explaining. Just one feedback. HTTP cookies are meant for web sessions. But it will be interpreted only in layer 7. It's better to stick with the mainframe example.

[@Fardeen.]

Keep making more

[@GoUpv13]

i love you man

[@mastersaha]

Thanks!

[@PracticalNetworking]

You're welcome! Thank you for supporting the channel =)

[@khelouiazzeddine3113]

Thanks

[@niksatan]

Liked, commented, subscribed - great stuff!

[@PracticalNetworking]

[@willgreat8384]

Now that I’m done I will hop on ACL then subnetting mastery after . I think you should make LABs if you have not already

[@PracticalNetworking]

In my full course, I 100% plan to make labs. It's harder to do on KZbin, however. But yes, great thought =)

[@user-hm5gx9wj7h]

i just watched this whole series in one sitting lmao.

[@alittax]

Great video! Can you please help me understand something related? Do cookies make socket pairs useless? If cookies uniquely identify user sessions, doesn't this mean that there is no use for the socket pairs (since the user session remains intact if the socket pairs change)? In other words, once the connection is established, neither sender, nor receiver would need to specify the protocol and ports, because the cookies replace the function they (protocol and ports) fulfill in combination with the source and destination IPs? Thank you.

[@PracticalNetworking]

I wouldn't say "useless", no. Remember, outside of HTTP the socket helps deliver the packets to the HTTP service. Consider a computer that is connected to multiple websites at a time, or maybe streaming audio or playing online games while also browsing the internet, etc. The socket helps distinguish between each of those applications at the Operating System level. There is more detail about this in my Layer 4 video on the OSI model (link in description).

[@elbarnaouimohamed]

merci

[@nutmoose]

Sir, is the use of Extended ASCII hard coded into HTTP protocol or are we allowed to use other character encodings (like UTF-8) ?

[@Pang-nn4eq]

Can you make a video on networking history and protocol wars? TCP/IP vs OSI, packet switching vs circuit switching etc.

[@albert-ow]

Hello, do you have a playlist on IP addresses and how it works?

[@josec4916]

Question if anyone can answer I would greatly appreciate it. Are protocols like HTTP, FTP, etc. in layer 5 or layer 7 because when I google search it informs me that it is a Layer 7 protocol.

[@Faisal-qd1jc]

is your course still under construction? I checked the website and it looked not ready.

[@juanmondragon]

So if im understanding this correctly, the port request that you submit has predefined rules? In other words, the port request you are using, such ftp, https, smb, etc., actually make up its own "layer 5, 6 and 7"? Just to clarify, my question is for example on how does port 443 know to encrypt data since port 80 is sent in the clear. Will port 443 have it's own rule set that you are required to meet such as implementing certificates before you host your website on port 443 or will your website automatically be encrypted if it's just hosted on port 443 and not port 80.

[@minhluudinh5522]

When will the fundamental networking course finish?

[@Braeden.F]

So will cookies be unnecessary with IPv6 addresses? Since I believe those are not supposed to change from network to network?

[@wwolfram33]

Hello Ed, could you please explain why the 2 x blue or 2 x green users would have the same IP & MAC address?

[@PracticalNetworking]

In the early illustration, since they are both merely users on the same mainframe, they are using the IP & Mac of the mainframe, that is why they have the identical IP/MACs. hth