Questions tagged [osi]
For questions about the Open Systems Interconnect (OSI) model defined by the International Organization for Standardization (ISO).
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point-to-point or broadcast network : concrete case
What concrete rule or layer of the OSI model should be used to decide whether a network is a point-to-point network or a broadcast network?
A general definition (*) seems clear, but in practice it ...
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Clarification of relation between IPv6 and TCP [duplicate]
I thought IPv6 and TCP could be used independently, but IP does not need TCP at all, whereas TCP usually needs IP to function. Is my understanding correct? Does IPv6 need TCP to function? Looking at ...
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What happens when the sender sends more data then the advertised window by the receiver?
I am relatively new to networking. I am doubting what happens when the sender sends more data than the advertised window by the receiver. I mean that the receiver advertises the window size based of ...
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What are different encoding schemes used in gigabit ethernet?
I was reading about digital transmission, there are many steps namely:
Analog to Digital conversion
Source coding
Channel coding
Line coding
Pulse shaping
Modulation
Multiple access techniques
...
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Logical Link Control (LLC) vs Medium Access Control (MAC)
What differs the LLC sublayer from the MAC sublayer?
From what I've understood
- The MAC sublayer does what the PHY layer should be doing: detection (error, collision), channel listening, analog-to-...
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OSI layer of Neighbor Discovery Protocol
NDP operates using ICMPv6 and, even though ICMPv6 messages are encapsulated in payload field of IPv6 datagram, ICMPv6 and ICMP are usually considered as network layer protocols. At least, on Wikipedia ...
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Alternative to the Internet for a local network
Suppose we are designing a network and we want to isolate it from the Internet. Are there any alternatives to the Internet for a local network?
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IP and Ethernet endianness
I'm completely new to the topic, I've read that Ethernet sends Bytes in a Big-Endian way, but that bits are sent with Little-Endian. I've also read that IPv4 uses Big_endian order. So my question is, ...
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Why are connected switches not a good substitute for the network layer? [duplicate]
Unless I am missing something, because switches can be chained together, I am not sure why the network layer is needed. Theoretically, one can dedicate a frame to any MAC address, and assuming there ...
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Responsibility of the physical sublayers of Ethernet
I'm learning about Ethernet and the sources I've found seem to be controversial regarding the role of the physical sublayers of Ethernet displayed on the following image.
Just to mention an example ...
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Why is MPLS label added between layer 2 header and layer 3 header of OSI model and not between headers of layer 3 and 4 of OSI model?
Is there a possibility to use any other two OSI model layers' middle positions? What is the basic concept of switching of packets with MPLS on layer 2.5 of OSI Reference model?
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How Network layer routing actually works in the physical world
This is my first question here, It might be a vague or off topic, I apologise in advance, but I am happy to improve it
Basically I have a somewhat decent theoretical understanding of the OSI model. ...
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Maximum packet size Ethernet Frame and IP packet
I am a little bit confused about one fact. According to the specification, the ethernet frame maximum size is 1518 bytes, and the IPv4 packet size Length field in an IPv4 header can be up to 65535 ...
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session layer in OSI model
I'm wondering to know how session layer works. In my understanding session layer is to establish active communication sessions between two devices. Based on the OSI layer model, it works layer by ...
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Is there a term for application layer protocols that are responsibilities of network engineers?
In studying network engineering, it is usually taught that network engineers are responsible from physical layer up to transport layer, that is, layer 1-4 only.
Obviously, HTTP or HTTPS are off-topic ...
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What does it mean for a device to be layer n?
I've always read, the router is a layer 3 device, the switch is a layer 2 device, the hub and repeater are layer 1 devices and so on with other devices.
But what does this mean? When I started ...
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Is it possible to have a local area network with only layer 1 and not layer 2 of the OSI model?
I know the OSI model has seven layers. Can you consider a LAN to exist without layer 2 and just layer 1? The answers that I saw on Quora were not clear. Some of the answers on Quora came close to ...
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Difference between routing, forwarding, and switching
I feel like the three terms are often used as synonyms but actually all mean something different. I did look at Wikipedia sites but I'm still unsure about the definitions of the three.
From my ...
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What does the network layer do at the receiver
My book (Andrew S. Tanenbaum, “Computer Networks”, Fifth Edition.) mentions while explaining the network layer that the key issue with a network layer is
determining how packets are routed from ...
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How is Network Access Layer/Link Layer of TCP/IP model different from Layer 1 and Layer 2 of OSI?
I was reading CCNA R&S book by Todd Lammle, I saw this in the chapter TCP/IP Basics under Network Access/Link Layer
Advantage of this layer over Layer 1 and Layer 2 of OSI model is that there ...
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How collisions are handled in the daisy-chained switches?
I understand the principle of collision domains and how they are issues in hubs. I also get how switches are actually creating its own collision domain on each port.
Therefore Port to Port ...
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How can a router port forward and read the destination port if it's a L3 device
My understanding of port forwarding is that on the router, you configure a setting that allows you to forward all packets from external traffic with a specific destination port towards a device within ...
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Is the header of any other layer (other than the Data Link layer) is also removed and re-added when reaching a router?
Based on my understanding, when a packet reaches a router, the Data Link layer header (and trailer if there is a trailer) will be removed from the packet and a new header (and a new trailer if there ...
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Why need Ack flag if we already have ack number in TCP
If we have ack number so from there we can trace that how many bytes are received and which byte is need next so then what is the use of Ack flag there?
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What is the difference between a private IP and a MAC address? [duplicate]
I am taking a course preparing me for the Network+ certification. I wanted to know what the purpose of a private IP is when a MAC address exists. From what I understand, the MAC address is used to ...
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OSI Model and Networking Protocols Relationship
When most networking students first learn about the OSI model, they spend a great deal of time trying to figure out which layer of the model a particular protocol fits into. We get a lot of questions ...
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How to benchmark time a packet spend in each OSI layer?
I'm benchmarking latency of sending a TCP packet from a client to a server. The payload of the packet is the nanosecond timestamp (using clock_gettime() on Linux) right before the send() socket ...
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Can refer a detailed low level explaination of the OSI model at operating system level? [duplicate]
I understand the function of each layer in OSI model but I can not comprehend the inner working at the operating system level. I can't mentally picture the life cycle of data from application layer to ...
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HTTP and TCP relationship
I always wondered how HTTP knows when it has enough TCP segments in order to process a request or response.
Can someone give me more information about the process?
Thanks.
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Why in the TCP/IP model the link & physical are one?
I'm currently learning about the OSI model and the TCP/IP models, and I was wondering: Why in the TCP/IP model the physical layer and the data link layer are combined?
I'll state how I understand the ...
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Why PPTP, L2TP, PPPOE are in OSI Layer2?
PPTP, L2TP, PPPOE - these are tunneling protocols. And they are Data link Layer protocols. Why?
As I understood, Layer2 protocols work only in same subnet. They don't use IP addresses and cannot be ...
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EtherType multiplexing used by LLC layer
What's the type of multiplexing used by Ethernet (LLC layer)?
It says in Wikipedia "The LLC sublayer provides multiplexing mechanisms that make it possible for several network protocols (e.g. IP, ...
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How n level come to know the n+1 level contents?
Suppose in application layer is running some application. And application has respective source port number and destination port number. And know that n layer has no authentication to know about n+1 ...
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Do Bluetooth Devices have MAC address with the same specification as the MAC addresses of the Ethernet and Wi-Fi Network cards?
I recently found out that ZigBee devices have MAC addresses.
ZigBee is more related to Bluetooth from what I know rather than Ethernet or Wi-Fi. Do Bluetooth devices such as phones, headphones, ...
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What is responsibility of different layers of OSI model and intermediate devices between sender and receiver when data packets are lost/corrupted?
Suppose sender sending some data to receiver and there are 3 routers between them. R1, R2, R3 are routers.
Now sender starts sending data packet D through it's AL, TL, N/W L, DLL,PL to router R1 ...
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Why is cable classfied in layer 1 in OSI model
I am learning about the OSI model and TCP/IP Protocol.
In my understanding, they classify cables to layer 1 (Physical Layer).
But, when you connect two different devices you have to use cables no ...
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Ethernet compatibility
I am improving my knowledge about the Ethernet protocol. During my study, I noticed that they are multiple versions of the protocol. Example: 2.5GBASE-T and 5GBASE-T and 100BASE-TX.
I wonder depending ...
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OSI model transition between layers (data chunking across layers)
There is something I don't understand regarding the OSI model.
From what I learned, sometimes information will need to broken down into smaller pieces of information.
My question is - let's say that ...
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Why router can't be used for converting different model of network but gateway can do this?
We know that Router can't be used for converting different model (e.g OSI model to TCP/IP or TCP/IP model to OSI) of network. It isn't a multiprotocol converter. But gateway is a highly sophisticated ...
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Understanding the definition of layer 2
The Wikipedia (and other sources) page about the OSI model explains layer 2 as such:
The data link layer provides node-to-node data transfer—a link between two directly connected nodes. ...
Let's ...
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Does the OSI model apply anywhere else other than computer networking? [duplicate]
I try to understand the OSI model, more about why it was created and what exactly it tries to achieve.
The Wikipedia page says:
The Open Systems Interconnection model (OSI model) is a conceptual ...
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What is the goal of the OSI model? [duplicate]
I'm currently learning about the OSI model, trying to understand exactly what it is and what is the purpose behind it.
The Wikipedia page says:
The Open Systems Interconnection model (OSI model) is a ...
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OSI Model vs Network Model: Does It Matter Which One You Use?
The OSI (Open Systems Interconnection) model is comprised of the following layers:
7. Application Layer
6. Presentation Layer
5. Session Layer
4. Transport Layer
3. Network Layer
2. Data Link ...
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Where do the layers of the OSI Model operate in the operating system?
The OSI model describes them as layers. But where do these layers actually operate in the operating system? For example, where and what actually does TCP? All these layers are described as using ...
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OSI model: the session initializes the communication?
A simplified example of how the OSI model works, from this page:
For example: Mr. Cooper wants to send Ms. Palmer an email. Mr. Cooper composes his message in an email application on his laptop and ...
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data link layer and encapsulation method used for specific types of media?
I was reading about the OSI model then found this question in the review questions :
Which layer of the OSI model is responsible for specifying the
encapsulation method used for specific types of ...
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In the ISO model how does the Network Layer and Application Layer knwo when frames and segments respectively are complete
I understand the general sense of the ISO model but it's my understanding that the Data from the Application layer which is usually large would get split into many TCP packets. The same thing would ...
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Do layer 2 protocols allow hosts to communicate without being on a network?
Please go easy on me as I'm just a noob in the networking space.
As far as I have learnt, layer 2 protocols use MAC addresses for communication, which doesn't really depend on what network you're in ...
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Is OSI model merely used for troubleshooting purpose? [duplicate]
I'm a student and recently started understanding OSI model, from what I understand is that OSI model is just theoretical and not really used in real world. It's mainly for troubleshooting purpose.
I'...
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Why does one say IP fragmentation is bad and to be avoided when in reality data always needs to be fragmented for MTU compatibility?
Why does one say fragmentation is bad and must be avoided due to performance issues when in reality fragmentation intrinsically occurs within the communication ?
Example:
User1 wants to send 100 000 ...
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