Questions tagged [osi]

For questions about the Open Systems Interconnect (OSI) model defined by the International Organization for Standardization (ISO).

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27 views

Networks theory: Layers, Services and Interfaces

I want to learn about computer networks from the bottom up. I don't really understand the nuances of networking layers, with books mentioning that layers provide services to layers above them, but the ...
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15 views

Switch vs. Router and sequence of OSI Model [duplicate]

As I understand it: A switch (layer 2) seems to define a LAN and a router (layer 3) enables communication between distant LANs. A device on a LAN will give it's MAC address to the switch upon ...
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33 views

Configuration of a Dell managed switch clashes with my network understanding

I got the opportunity to play around with a Dell managed switch from the 2000 series with OS10. I tried to configure a management IP adress 10.10.12.141 (/24) according to the manual but somehow ...
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1answer
21 views

Propogation delay vs time required to send out a complete frame on channel

I was reading Data Communications and Networking by Behrouz A. Forouzan in which for simple Aloha protocol the vulnerable time given was T(fr) (time required to send out a complete frame on the ...
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14 views

How to find which protocol is used by lower layers? [duplicate]

When we type https://stackoverflow.com/ all the data which is sent to this server would be using HTTPS protocol in transport level So is it possible for me to know which error detection, flow control ...
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1answer
19 views

Session layer role(with example) in OSI Model [duplicate]

Could someone provide some real world scenerios to understand the role played by session layer in OSI model. Example: Presentation Layer handles zip&unzip etc. Similarly what does session layer ...
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1answer
75 views

Network Protocol vs Framework?

I've been a network engineer for almost 4 years now. I thought I understand what a network protocol means. but now I'm having doubts. For me, Ethernet is a protocol used at layer 2. there would be ...
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1answer
39 views

Unicast and Multicast MAC address convention

I need help in understanding how Unicast and Multicast MAC address is differentiated as explained in wiki. According to what I understood, when the least significant bit is set as 0 in the first octet ...
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2answers
65 views

OSI Layer Model

I have been searching out for in depth knowledge of OSI layer model. I want to know that what information does a Application, Presentation and session layer header contains. Moreover where do these ...
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14 views

Understanding OSI communication model from Electronics Perspective [duplicate]

I have gone through the OSI communication model and the associated levels. But I do not understand on how is this implemented in the Hardware level. Or let me put it like this. Suppose we have a USB ...
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1answer
78 views

What steps must be accomplished in each layer of the TCP/IP model to connect a website?

What steps must be accomplished in each layer of the TCP/IP model to connect a website?
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1answer
63 views

How does a 802.11 (wifi) frame identify the payload's layer 3 protocol?

My understanding is that the 802.11 frame header is an equivalent of ether header. In the ether header, there is an EtherType field that identifies the payload protocol, such as IPv4/IPv6/ARP etc. ...
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1answer
135 views

Confusion about TCP/IP data flow in layers

I'm confused about how the data flows through the layers of the TCP/IP model, so I'll just tell what I think it happens (using an email example) and I'd appreciate if you can point my mistakes. ...
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17 views

Are PEPs (Performance Enhancing Proxies) strictly “below layer 4” devices?

I am a software bubba, not network, and PEPs are new to me. Ideally, if they're strictly "below layer 4", it'd be nice to leave them as "new stuff, but lives at layer 4" and ignore them. However... ...
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22 views

What Invariants/guarantees do various layers of the OSI model provide? [duplicate]

I saw it stated in an answer to this other question What transmission service gurantees does Ethernet give? that every layer of the OSI model provides both "hard" and "soft" guarantees to the layer ...
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1answer
90 views

Transport layer segmentation and Ip layer fragmentation [duplicate]

From the OSI Model's point of view: If we already have Ip fragmentation which happen due to the network limitation, why the transport layer provides the segmentation mechanism via TCP protocol? why ...
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32 views

Why TCP is not in layer 5? [duplicate]

I read that TCP is in layer 4. But i also read that to send data with TCP i have to establish a session (in the handshaking phase). Does this mean that if we work only up to layer 4 TCP is useless (...
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1answer
1k views

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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1answer
305 views

Understanding EUI-64

I was reading Forouzan's book. It says following: In IPv4 addressing, there is not a specific relation between the hostid (at the IP level) and link-layer address (at the data-link layer) because ...
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2answers
120 views

In IP, to what extent are the network addresses coordinates?

Routing of data relies on being able to reach the destination address. There are network addressing systems proposed where the addresses are coordinates, Vivaldi from MIT, for example. The routing in ...
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19 views

how OSI and TCP/IP layers work? [duplicate]

I am really confused by how the layers these model work. I'm not asking about what are their functions. I read that transport layer provides end-to-end of all packet delivery, and networking also ...
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3answers
712 views

Do routers understand transport protocol?

We are taught about the difference between hubs, switches, and routers. A hub is a layer 1 device, it only knows layer 1 and doesn't care about layer 2 and above. Similarly, a switch is a layer 2 ...
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2answers
361 views

Which physical layers are part of PROFINET?

I understand that Profinet builds on Ethernet, but I am not quite sure how. Ethernet has a lot of different standards for the physical layer, eg 10Base2 (coaxial, 10 Mbit/s), 100Base-TX (twisted ...
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2answers
5k views

VPNs are working in which layer of the OSI model? [closed]

As the following picture shows, it is possible to categorize VPNs in two general categories: Client-based VPNs Network-based VPNs When it is required to choose a VPN for implementation in a network, ...
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1answer
32 views

Whats the security difference between Policy Based IPSec VPN tunnel vs HTTPS + Basic auth

We have several customers with the same service installed within their DMZ. This service is a HTTPS server. The server does not have authentication, this is solved by configuring the NetScaler ...
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1answer
248 views

What's the meaning of `circuit level gateway`?

The proxy server is an important security function provided by the Internet "circuit level gateway". Its work is mainly at the session layer of the Open Systems Interconnection (OSI) model, which acts ...
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2answers
42 views

LLC connections

TCP establishes a logical connection before sending data,where LLC connections are physical and are being held just between two computers,not more. Is this correct? If so,why LLC=LOGICAL LINK ...
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1answer
47 views

why can't we use the sequence number to distinguish them since every packet has a different sequence number? [closed]

It is a question from Networking stanford course. A server typically listens for TCP connections on a particular port (e.g. 80 for HTTP or 22 for SSH). Which fields can the server use to ...
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2answers
852 views

At which OSI layer a user-generated data resides?

I am getting a bit confused about which OSI layer is being used to store user-generated data. As far as I understand the process of encapsulation, the higher layers (starting with layer 7 - ...
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3answers
1k views

How to explain the data flow of OSI model layers in a single picture [duplicate]

Take an example of searching www.example.com in a web browser. I have some confusions at each layer and they are We have opened a web browser and searched for www.example.com. Now, As far as I know, ...
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2answers
338 views

Do the concepts of IP address and network interface not belong to the same layer?

https://unix.stackexchange.com/a/508065/674 You are confusing the device driver layers and the IP layers of the stack. At the IP layer, 127.0.0.1 is just another IP address and treated the ...
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1answer
147 views

Message formatting and encapsulation

I've gotten confused when reading about encapsulation and the OSI and TCP/IP models. I first read about message formatting and encapsulation and the diagram I read showed: Destination | Source and ...
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1answer
161 views

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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8answers
2k views

Using sound waves in layer 1

Is it possible, in theory, to use sound waves as the physical medium to transmit data over a network? In other words, could you implement layer 1 of the OSI networking model using sound waves or am ...
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4answers
959 views

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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1answer
86 views

Abstract service primitive

In SNMP RFC documents, often the concept of abstract service primitive (ASP) is used. What is ASP in fact ? I think it is also used in ISO OSI.
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3answers
2k views

Session layer vs Transport layer

It seems both do the same thing (or establishing a session between two hosts differs from establishing a connection between two?) So what exactly is the difference here that make us consider them as ...
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2answers
114 views

Do protocols ever have standards that affect multiple layers of networking?

I'm reading about higher-level protocols such as HTTP and SOAP (concerning the application layer at the highest level) in addition to lower-level ones such as TCP. So far these protocols concern only ...
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1answer
285 views

Where does DNS resolution fit within the TCP/IP stack?

I know that it's possible to whitelist/blacklist IP addresses (for example, only allowing a few external IP addresses to be contacted from within a VPN). But since IP address destinations are the ...
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1answer
734 views

Dependency between IEEE 802 and OSI model [duplicate]

My question is focussed on IEEE 802.11x for (WLAN) and 802.15.1 (Bluetooth) Wikipedia and other sources underline, that the mentioned IEEE standards just define the PHY and MAC layer from the OSI ...
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1answer
2k views

Data link layer acknowledgement

I'm confused with some concepts please help me out, Data link layer manage flow control hop to hop. Flow control requires acknowledgement receiving but If we observe data link layer header, it does ...
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1answer
36 views

Are there any network devices that can be configured to add information from one layer to another?

If I have a corporate network, no WWW Internet outside of it, only different subnets. Can a Cisco router or switch be configured to take information from one layer and embed it in another layer? For ...
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4answers
165 views

What is the physical representation of the OSI model? [duplicate]

I read on the Internet that the NIC resides on the physical layer of the OSI model so what about the other 6 layers. I know what they actually do but i want to know how it's done. In other wards, what ...
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3answers
448 views

Do OSI and TCP/IP models use the same protocols?

OSI is known for using hundreds of protocols to do its job. Both OSI and TCP/IP have Transport and Network(Internet) layers where TCP and IP protocols work respectively. It is clear that TCP/IP model ...
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1answer
48 views

How to add new tasks to layers of OSI or TCP/IP?

Which software and hardware parts of a computer are responsible for adding or removing values to the initial payload of a data packet in every layer of OSI or TCP/IP model? In other words, which parts ...
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3answers
6k views

Is the addressing done at transport layer or network layer of OSI?

According to the OSI model, the transport layer divides the data into segments and then attaches the source IP and destination IP along with the port numbers. Also it is said that the network layer ...
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2answers
99 views

what are multiple formats of message when passed through all the TCP/IP layers

I was wondering how the message changes its form or structure while passing through multiple layers. Consider host 'A' sending "Hello" as message to host 'B'. So how it changes its form while ...
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1answer
353 views

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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6answers
2k views

Why do we need FTP when there are layers to transmit data?

In OSI, there are layers for routing, encapsulating and transmitting the data. Then why do we need FTP? I read the following definition of FTP in books: FTP is used for transferring files on ...
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3answers
2k views

Error Detection across OSI layers confusion

Confusion: How does the transmitter know that his information( bits in physical layer, frames in data link layer, packet in network layer ) was transmitted correctly to the receiver? I know that in ...