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Questions tagged [osi]

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

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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
49 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
37 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
59 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
40 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
220 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
32 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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3answers
62 views

What is the physical representation of the OSI model?

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
114 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
34 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
1k 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
50 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
173 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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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
898 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 ...
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1answer
59 views

What requirements must general firewall/routing software meet, to make OSI 2 port mirroring work correctly?

The basics are obvious, but there are technical points of networking implication which I don't understand. Some of these are general to networking, others general to all routing/firewall softwares ...
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2answers
1k views

What is the difference between TCP/IP protocol and TCP model?

We know that there are two models OSI and TCP model. But TCP/IP protocol is different from TCP model as this protocol used in both OSI as well as TCP model. So why the two are named the same is ...
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3answers
614 views

Does the OSI model support connectionless communication in the transport layer? [closed]

In section 7.4.4.1.2 of ISO/IEC 7498-1:1994(E) it begins with: In connectionless-mode, the Transport Layer provides the following functions to support connectionless-mode transmission: But many ...
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1answer
303 views

OSI model peer communication

"In OSI model, each layer provides a protocol to communicate with its peer. When a packet is transmitted by a layer, a header consisting of Protocol Control Information (PCI) is added to the data to ...
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2answers
164 views

Why Ethernet was chosen to be the primary protocol + why carrier ethernet was created?

I'm currently trying to investigate the extra benefit that Ethernet has to offer for the internet today. As far as i investigated & know, Ethernet gives us a new hardware, cables and functionality ...
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1answer
1k views

Does the physical layer is OSI ISO model add any header?

According to OSI model, does the physical layer add any header to the date it receives from layer 2? Or is it simply sending the data frames it gets from layer2 as shown in the figure below? Are the ...
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1answer
49 views

What are connectivity associations in LAN? - IEEE Std 802.1X-2010

In IEEE Std 802.1X-2010, Appendix D, Section D.8, there is the following phrase However simple or complex, the establishment of a connectivity association for connectionless data transfer ...
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2answers
331 views

OSI and TCP/IP: which is the relation? [duplicate]

In the "network" literature there are always explanations of this two reference models: OSI and TCP/IP. The TCP/IP conceptual model is indeed a "fact" in terms of implementation. Anyone can find the ...
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2answers
912 views

Packet filtering firewall

I read that packet filtering firewall operates at level 3 (network layer). In the description I read that it filters packets based on IP addresses and ports. If it's operating at level 3, how can it ...
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1answer
41 views

How will these frames be delivered to respective destination nodes? [closed]

I have the following 3 devices on my network(a bus topology): A,B,C Let MAC(i) - denote the MAC address of the device i. IP(i) - denote the IP address of the device i. The devices B and C happen ...
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1answer
45 views

In the MAC acronym what do the words Media, Access and Control refer to independently?

I am not a native English speaker and I know what MAC addresses are and how are they used in networks. However what I do not understand is where this words came from independently. What does Media ...
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1answer
43 views

Placing a “protocol” field in the IP header breaks the conceptual separation of interests that the OSI aimed for [closed]

I saw that while reading an answer about .. and now I'm confused.
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1answer
295 views

How does a NIC know where the start of a frame is?

A question popped into my head today and after a quick few searches on google, I have no idea. When a device is sent a frame there is a layer 1 header/preamble saying the length and layer 2 protocol (...
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3answers
169 views

TCP/IP protocol suite

I read that "TCP/IP protocol suite contains relatively independent protocols which can be mixed and matched which is not possible in OSI". What is the meaning of mix and match over here ? Can we mix ...
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1answer
190 views

OSI layer for promiscous / monitor mode

On what OSI layer do network cards operate when the use promiscuous mode monitor mode ?
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2answers
558 views

What is the difference between “Network Model” and “Network Architecture”?

I have a great confusion about the terms "Model" and "Architecture". Is the TCP/IP is a model or architecture?. If it is model then what is architecture? What does the both terms refers to.
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1answer
250 views

IP/TCP - most common use cases [closed]

What are the most common use cases for IP and TCP? I am trying to find out what might be the best use cases for IP and TCP connections but unfortunately I wasn't very succesful so far.
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3answers
498 views

How nodes/switches communicate between each other?

fWe know that they only care about the first 3 layers of OSI-Model so when a node receive the data from a PC/Server, it goes up to layer 2 (Here is MAC address) and then it goes up to Network layer (3)...
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0answers
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Question about the 7 layers of OSI Model [duplicate]

I just saw level 1-2-3-4 (from Physical to Transport) We have the following : The thing is: We know that at layer 3 there is the IP protocol that uses DNS Server to get the IP Address of the ...
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1answer
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Why is local network communication handled differently to inter-network communication in the OSI model?

Looking at a Stack Overflow question - https://stackoverflow.com/questions/13006949/what-is-the-difference-between-the-data-link-layer-and-link-layer - one of the answers says that the data link layer,...
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1answer
195 views

Regarding clns mtu

I understand the below points,please confirm if my understanding is correct. MTU > MSS E.g if my MSS is 1460 bytes, then MTU should be at least 1500 bytes(20 bytes for IP header and 20 bytes for TCP ...
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2answers
1k views

Is ping in the application layer?

Ping works in the internet layer, but when I ping an IP address in my terminal, is ping in the application layer? If it is, how does the application pass transport layer? If it is not, can I say ...
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1answer
283 views

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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2answers
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What is Data Offset and its uses in TCP Header?

I was learning about TCP and came across Data offset. This was the answer I found. " Data offset specifies the size of the TCP header in 32 bit words. The min. size header is 5 words and the max. is ...
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1answer
179 views

What does “Telnet runs over IP” means?

Just curious on learning about protocols. I know that TELNET is connection oriented protocol and IP is connectionless protocol. What does it imply when the networking blogs and resources say that "...
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3answers
3k views

Does a switch understand packets? If yes, what is the frame terminology for?

I was a little confused between packet and frame. The confusion was based on, if a switch is a layer 2 device, how does it reads a packet from a layer 3 device, and where is the 'frame' thing which is ...
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1answer
439 views

How are duplicate packets handled at the Data Link Layer?

Reading up about the data link layer I found that the logical link control sublayer uses sequence numbers to find duplicate packet frame transmissions. I understood the sequence number game with ...
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2answers
2k views

Does every packet contain headers from each layer of the OSI model?

Pretty straight-forward question. Read through Section One of the 802.3 standard, and I found a nice model of a MAC frame that gives me extra insight, but I see that this question is not asked ...
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2answers
146 views

Regarding Encapsulation in OSI layer

The term encapsulation generally signifies the below in terms of OSI model as described clearly here "Each “function” (broadly speaking) encapsulates the layer(s) above it. The network layer ...
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1answer
858 views

PPP, VPN, Tunneling and OSI model

I am really confused about tunneling protocol family and all related protocols. I read a bunch of articles, rfc but still cannot get the idea. I will put my questions between my explanation. A ...
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1answer
28 views

How to distinguish a traffic that belongs to specific service

Suppose I have a server running different services, say Email exchange, storage space, web server, and SQL database. Assuming this server is bounded with one IP address and one NIC card, how can I ...
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1answer
39 views

Already session between two computers before going through layers?

How can a computer have a session with another computer without going through the transport, network, data link and physical layers? I took this information from this video.
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2answers
1k views

Encapsulation and decapsulation basics for OSI layer

I have read that encapsulation takes place down the layers while decapsulation takes place up the layers. In essence, the encapsulation starts at Application layer all the way upto Physical layer. ...
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2answers
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What are the most common technologies that the IPv4 or IPv6 run on top of BESIDES the ethernet protocol?

I recently found out that lots of different types of devices have a MAC address not just ethernet devices. I was thinking that it is possible for Internet protocol to run over many other types of ...
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2answers
9k views

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, ...