Questions tagged [osi]

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

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37
votes
7answers
15k views

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 ...
9
votes
2answers
6k views

OSI model and physical location of the layers

Hi Cisco student/newbie here! I understand that data passes down through the OSI model and then at the physical layer is transported as bits across the networkcables. But I'm confused at exactly ...
9
votes
3answers
6k views

How are MAC/IP addresses used in routing

I have to teach my sixth form about MAC Addresses and IP Addresses in a few weeks time and there are some areas I am unclear on which I am hoping some of you will be able to clarify for me. I have ...
8
votes
3answers
5k 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 ...
17
votes
2answers
12k views

In which OSI/TCP-IP model layers do BGP, RIP protocols belong?

We know that in the OSI or TCP-IP model, the higher layer utilizes the services offered by the lower layer. For example, the data link layer uses services offered by the physical layer, network layer ...
10
votes
3answers
1k views

What is a "Layer 3 Switch"?

What is a "Layer 3 Switch"? I essentially understand the OSI model, well maybe I don't and maybe that is why I don't understand. Its just that I don't see how/when/if a "managed switch" becomes a "...
8
votes
5answers
3k views

Why is the ICMP protocol considered to run at layer 3 on the Wikipedia page?

Why is the ICMP protocol considered to run at layer 3 on the Wikipedia page (same layer as IP) when the ICMP protocol data is a payload of the IP packet? This is the article on Wikipedia that states ...
7
votes
2answers
13k views

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 ...
5
votes
3answers
65k views

How to know at what OSI Layer(s) does a firewall operate

I understand that Firewalls may operate on different OSI layers depends on the firewall itself. but how can I know if I install specific firewall at what OSI Layer(s) it does operate ?
5
votes
5answers
1k views

How we can assume which network protocol is working in which OSI Layer?

For a long time, I have this kind of silly question: How we can say some network protocols are working in X layer of the OSI model? For example, HTTP working in L7 of OSI, OSPF is L3, ICMP is L4, TCP ...
3
votes
1answer
2k views

What is the need for transport Layer?

In 5-layer model. Why we need additional transport layer? I read these two points Users who interact with software have no control over the sub-net; Transport Service can provide a more reliable ...
10
votes
3answers
2k views

Why does PPP need an underlying protocol?

The Point-to-Point Protocol is (at least according to Wikipedia) a Datalink Layer Protocol. I know that different use cases exist for it but on examining the image below from Wikipedia one can see ...
2
votes
3answers
272 views

What are the minimum requirements to be on the internet?

People often define the internet as a network of networks but this is wrong. If I connected two LANs together that wouldn't nesecarilly be on or part of the internet. In class we learned about ATM, ...
2
votes
2answers
882 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 - ...
2
votes
2answers
1k views

Which layers of the protocol stack does a border router access for which purpose?

Dataflows on the internet are often depicted as going from one host via at least two border routers to another host. In these illustrations, the hosts are equipped with and make use of the full ...
0
votes
1answer
106 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?