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.
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.
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.
because china has no freedom ,only relationship. if you are better ,china will banned you . you will not get a better job in china. just like google. baidu is loser ,but china banned google, baidu can be lived in china . China is not fair and no justice . life like a game ,but china has no fair . who win the game ,it is not important for china . -------------------- the chinese knew china have no fair ,no justice ,they went to the US ,for what ? if there is not the US country , where they can learn technology from ？ no freedom ,no fair , what is technology ?
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
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
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.
"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.
+Genevieve JochetzGenevieveJ Cisco goes over the same thing over and over throughout the entire course, I like it because it burns into your head through repetition alone
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
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.
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.
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.
xSpArTiChRiSx I'm literally still learning all this but my teacher explained the application as only containing applications that are network aware. So for example an application that works as normal once you've unplugged your ethernet cable (or disabled wifi) is not in this layer. I'm still learning it all though...
MrLFXproductions The explanation your teacher gave you is brutally basic and very subjective. This explanation would suffice if you where going for a programing degree and he just needed to touch on the OSI model for a brief understanding. However if you are going to be in the IT field (net admin etc) then I would be a little upset with your instructor. As stated before, the Application Layer should not be confused with the "apps" that a user may interact with but rather the protocols that interact with the"apps". For example, BitTorrent is a program that shares the same name as the protocol it uses to facilitate peer to peer file sharing. The protocol BitTorrent would go in the Application Layer. However the program BitTorrent would not be on the OSI table at all. A good way to understand this is to think of the OSI model as an onion. You (the user) may pick up the onion and look at it and smell it. This part of the onion is the GUI of the OS and the programs. You peel away that part of the onion and you will see the protocols. So on and so forth.
xSpArTiChRiSx Yeah any program that is network aware (can store, send, and retrieve data over a network) is described as a Layer 7 application (differentiating them from non-network aware apps). These programs are not to be confused as residing in the respective layer. Layer 7 apps utilise (tap into/connect with) the protocols that are associated with this layer, e.g, FTP, SMTP, POP3, NTP, SNMP and TFTP. Thanks for the clarification.
Sky King This just makes sense as the OSI is specific to networking. In saying that I would have stopped at Apps that have access to the network and not looked at the protocols as xspArTiChRisx has described, so thanks to him for that clarification. I wish I could study full time instead of working full time and having to learn my modules within days of my assignment due dates.
korisx I was in the same boat you are in man. I work at a full time seasonal factory that operates 7 days a week to keep up with customer demands. I work 6 days a week with Friday being my only day off and I was taking two networking classes that where held Mon-Thurs. Towards the end of the semester we had a big test on subnetting and I just couldn't do it. I didn't know the material at all because I didn't have the time to understand it. The OSI model, RAID, and converting IP to Binary and Hexadecimal where all things I learned like 30mins before class. I tried to do that with subnetting and failed miserably and had to drop the class.
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.
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.
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
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!
I don't understand your question. People randomly watched some old vids and a few hit subscribe. They were all for Super Stardust for PS3 which I don't think anyone plays anymore.
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.
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)
A true gem to TH-cam 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!
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)
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.
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!!
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 :)
Couldn't get it easier than this. I needed this explained plain and simple as need to study for a job related technical test. Thanks a lot Eli for this presentation.
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!
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 :)
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
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.
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.
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
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?
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 TH-cam seem to be just people talking about networks and showing graphic representations. That said, this is the best I've found so far! Thanks.. :-)
You rock dude! I use to skip your videos so many times when I wanted to learn this stuff lol, but the more that I kept hearing you speak and talking about networking, it started to make more and more sense. Thanks!
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.
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
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
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.
I subsribed to you in the first 53 seconds. Just finished a Wikipedia article about OSI and found you. Very charismatic and on the niche. A lot of your content "speaks" to my language....don't mind me, just a happy viewer! :)
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.
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.
Thank you Eli, just started to study about cisco csn routing and switching. this helped me ALOT !!! im gonna watch all your videos since you are a much better teacher then most :)
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.
its a joke bruh
PEBCAK error---Problem Exists Between Chair And Keyboard
That's true!)
HAHA
en.wikipedia.org/wiki/Layer_8
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)
+Aziz Rehman You're the man! Thanks!
+iSeabeck Thanks
thnx a lot man....
Salami Pizza - there you go ! :D
Programmers Dare Not Throw Salty Pretzels Away - I use this one if it helps someone
I understood more in 18 minutes than watching two 1 hour videos and reading network fundamentals!
Thanks!!
I totally agree!
reading in 2017 LUL
Yes same here
Strongly agreed
Most recent agree lol.
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’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.
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.
Start ur channel
I was going through the comments to see if someone pointed this out.
You are exactly right. When I heard this I said. Oh know he didn't... :)
Thanks for clarifying. I wasnt understanding why the firefox was in the application layer
Thank you
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.
because china has no freedom ,only relationship.
if you are better ,china will banned you . you will not get a better job in china.
just like google. baidu is loser ,but china banned google, baidu can be lived in china .
China is not fair and no justice .
life like a game ,but china has no fair . who win the game ,it is not important for china .
--------------------
the chinese knew china have no fair ,no justice ,they went to the US ,for what ?
if there is not the US country , where they can learn technology from ？
no freedom ,no fair , what is technology ?
Thanks Eli!!
Please (Physical Layer)
Do (Data Link Layer)
Not (Network Layer)
Tell (Transport Layer)
secret (Session Layer)
Password (Presentation Layer)
Anyone ( Application Layer )
+Ahmed hamdy This is asome thxs!
+Jason Felt this one is also cool
Good job
+ Senait Tigstu you're welcome and i think u should thank Eli too he did such a good explanation
O
+Ahmed hamdy
I use
All
People
Seem
To
Need
Data
Processing
I remember it by "people" for presentation and "data" for data link :)
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
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.
You just explained this better in
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
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.
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
12 years later, still relevant.. the best explanation ever
"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.
It's was hilarious lol
Well, cabling is the most underestimasted factor although it is important too.
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.
a - application
priest - presentation
saw - session
two = transport
nuns = network
doing = data link layer
pushups = physical layer
This is what the world needs.
Savage
and what happened next was terrifying. Well, tell all.
I like how you go over it like...3 times. I needed that.
Stop drinking vodka
What!? It's not like I have a problem or anything. *drinks more vodka*
Genevieve JochetzGenevieveJ lol
The art of teaching is repeating and giving different viewpoints of the same thing.
+Genevieve JochetzGenevieveJ Cisco goes over the same thing over and over throughout the entire course, I like it because it burns into your head through repetition alone
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
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.
This is the only explanation of the 7 layer model I have ever heard that actually makes sense. Thanks!
But it's completely wrong though.
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.
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.
xSpArTiChRiSx I'm literally still learning all this but my teacher explained the application as only containing applications that are network aware. So for example an application that works as normal once you've unplugged your ethernet cable (or disabled wifi) is not in this layer. I'm still learning it all though...
MrLFXproductions The explanation your teacher gave you is brutally basic and very subjective. This explanation would suffice if you where going for a programing degree and he just needed to touch on the OSI model for a brief understanding. However if you are going to be in the IT field (net admin etc) then I would be a little upset with your instructor. As stated before, the Application Layer should not be confused with the "apps" that a user may interact with but rather the protocols that interact with the"apps". For example, BitTorrent is a program that shares the same name as the protocol it uses to facilitate peer to peer file sharing. The protocol BitTorrent would go in the Application Layer. However the program BitTorrent would not be on the OSI table at all. A good way to understand this is to think of the OSI model as an onion. You (the user) may pick up the onion and look at it and smell it. This part of the onion is the GUI of the OS and the programs. You peel away that part of the onion and you will see the protocols. So on and so forth.
xSpArTiChRiSx Yeah any program that is network aware (can store, send, and retrieve data over a network) is described as a Layer 7 application (differentiating them from non-network aware apps). These programs are not to be confused as residing in the respective layer. Layer 7 apps utilise (tap into/connect with) the protocols that are associated with this layer, e.g, FTP, SMTP, POP3, NTP, SNMP and TFTP.
Thanks for the clarification.
Sky King This just makes sense as the OSI is specific to networking. In saying that I would have stopped at Apps that have access to the network and not looked at the protocols as xspArTiChRisx has described, so thanks to him for that clarification. I wish I could study full time instead of working full time and having to learn my modules within days of my assignment due dates.
korisx I was in the same boat you are in man. I work at a full time seasonal factory that operates 7 days a week to keep up with customer demands. I work 6 days a week with Friday being my only day off and I was taking two networking classes that where held Mon-Thurs. Towards the end of the semester we had a big test on subnetting and I just couldn't do it. I didn't know the material at all because I didn't have the time to understand it. The OSI model, RAID, and converting IP to Binary and Hexadecimal where all things I learned like 30mins before class. I tried to do that with subnetting and failed miserably and had to drop the class.
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.
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 !!! you are the reason i graduated !! Thx so much for all the info you gave !!!!
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!
I hope you got your CompTIA after all this years :)
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
Please
Do
Not
Teach
Students
Pointless
Acronyms
lol best one
I need this for my certifications...
thanks
this one is just one brilliant!
Best comment on the Internet.
I'm a non native english speaker and I can say your pronunciation is perfect. Zero effort understanding what you say :D Thank you!
CHARLIE..........YOU'RE INDEED A GENIUS.
THIS IS THE TYPE OF TUTOR I'M LOOKING FOR.
STRAIGHT TO THE POINT. GOD BLESS YOU
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!
@14:45 "Some 12 year old can't get onto the Pokemon website" Nobody saw the Pokemon invasion coming...
he's on point
how do you have a verified channel with only five subscribers??
I haven't made a video in 8 years. Wasn't really promoting it or anything.
so?
I don't understand your question. People randomly watched some old vids and a few hit subscribe. They were all for Super Stardust for PS3 which I don't think anyone plays anymore.
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.
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 :)
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)
This seems to me, a newbie, to be a set of topics that warrant a LOT more explanation and exploration. Each layer could perhaps be a video by itself.
Nice elaboration..
YEAH
A true gem to TH-cam 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!
I remember by the phrase "Please Do Not Tell Sales People Anything", which is a fact that any tech will know and stick to :)
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)
Tomorrow I'm taking a test on TCP/IP and OSI. If I pass, I'm subing.
great. good luck
Did you pass ? :P
@@puffolino1 He didn't
Starting New Technician job next month. This is great and never gets old! Eli is my bible right now in preparation.
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.
+Davd Salazr you're right
+Davd Salazr thanks god you saw this too i couldn't end the video since he said firefox is on application layer xD
+aziz laaziz hahaha me too man
Yeah the Application layer isn't the applications themselves but the code built into all operating systems that enables network aware applications.
Yep, completely misleading information disguised as fact.
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!!
this is the best explanation I have listened to so far. thanks a lot :)
they taught us what the osi layer was , but never how to use it. finally someone with knowledge, thx pc guy
In all his thumbnails he looks like a jail escapee
That's so rude he seems like a nice person
It's funny though
@stranger 31 hacker :)
@stranger 31 wtf HAHAHA
Bruv he looks like an MMA fighter.
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 :)
Skip to 2:35 for the actual start
If you are too impatient to sit through the introduction, networking might not be a thing for you.
6:58 and you can skip the definition of the layers which is reiterated as he goes backup the layers anyway.
Couldn't get it easier than this. I needed this explained plain and simple as need to study for a job related technical test. Thanks a lot Eli for this presentation.
You're awesome!!! I came here because Prof. Messer confused me. :)
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
u bald headed beauty i love you! thank you so much for the help! :)
AOSRoyal hahahahaahah this really made me laugh! 😂😂😂
Thats just made my day hahhahahha
🤣🤣
Fr lol. This was everything!!
🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣
this is why older videos actually try to teach us stuff, instead of just clout, pretty colors and graphs. thank you for this
from up down: All People Seem To Need Data Processing
from down up: Please Do Not Throw Susage Pizza Away
thanks shekh ;)
Saad Shifa All People Say They Never Download Porn. -Jason Perno
Jon Bayuga this one right here!
Saad Shifa Please do not teach stupid people acronims :) hehe
Nemanja Jovic *acronyms
Best class in utube about osi modell no doubt
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
+EDMOND BENICKS Salami*
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!
simple yet very effective.
Eli thank you so much for your lessons. The way you explain is way much better than the way my teachers ever did. Again, thank you so much
Best Intro to OSI model ever!!
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 :)
There's only one level he forgot to mention. Level 8: The Matrix Layer.
Bdmptsssss
There's also the 9th layer (The Political layer)...
Layer 8 is User layer.I have heard technicians speaking about "Problem on 8th layer of OSI model" when they mean user error.
I just love the way you simplify your ideas and how you impact knowledge. Bigups Eli!!
OSI - All People Seem To Need Data Processing
TCP-IP model - All This Is New
Class dismissed :D
Came here for my HCTM 420 System Integration and interoperability class recommended by my professor.
Thanks, this was such a informative video.
very good video, he explains is very well.
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
I have a networking exam in a few days. I think I just found my futur husband.
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.
brutal explanation
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.
thank you very much.. i understand now.. 😀😀😀
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
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?
HaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHa.. You are doing the right thing buddy
yus
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 TH-cam seem to be just people talking about networks and showing graphic representations. That said, this is the best I've found so far! Thanks.. :-)
Top down: A Priest Saw Two Nuns Doing Pushups
You rock dude! I use to skip your videos so many times when I wanted to learn this stuff lol, but the more that I kept hearing you speak and talking about networking, it started to make more and more sense. Thanks!
A person standing, typically never drinks pepsi. ;p
After 11 years, your video still helps me to better understand the goddamn OSI-laysers than any other book stuff oder videos, big thanks!
AKA the Seven Circles of Hell
This is easily the best tutorial on networking I've seen yet. Thank you!
Please (Physical Layer)
Do (Data Link Layer)
Not (Network Layer)
Teach (Transport Layer)
sex (Session Layer)
Predators (Presentation Layer)
***** assholes !
+GodPole algebra
+Bodyskillz2011 anal (Application)
+ged duffy
please=physical
do =datalink
not=networking
take =transport
some =session
people =presentation
advice= application
+Bodyskillz2011 All Pornstars Seem To Need Double Penetration
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.
:( why couldn't u be my teacher lol
Mahadonation1 He is already your teacher :) But you have to loose hours with another teacher :D
ha lol, they are so boring, you see people falling asleep in the lecture
even though they have knowledge
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
most intuitive explanation of the OSI layer ive ever seen. thanks. everyone else overcomplicates it
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
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.
I hope you teach somewhere the world needs talented teachers like yourself
I subsribed to you in the first 53 seconds. Just finished a Wikipedia article about OSI and found you. Very charismatic and on the niche. A lot of your content "speaks" to my language....don't mind me, just a happy viewer! :)
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!
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.
WOW!!! This was like a cup of water. Every other explanation on OSI has been painfully hard to grasp. Thank you Eli! 🙏🔥
This is so helpful!
I've lost a few Networking classes and this makes it so easy to catch up!
i almost failed subnet math
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.
Nice presentation. I like the way you broke down each layer and explained what it does. Thanks.
Thank you Eli, just started to study about cisco csn routing and switching. this helped me ALOT !!! im gonna watch all your videos since you are a much better teacher then most :)