How to troubleshoot networking using the OSI model architecture.

**TEIDDWEN** · 09-05-2011

I am working on corporate world as network engineer. Many time users called to solve their query related to internet. I solve their query but this task is very difficult. I heard about OSI model, by using the OSI model I can solve my query very easily. Unfortunately I have no idea regarding the OSI model architecture. I request to all of you if anyone have any information on OSI model then please it send to me.

**teenQ** · 09-05-2011

First you have to understand the function of all seven layers in the OSI model. You have a very valuable troubleshooting tool. If you can visualize the different pieces that complete the path of the data, you will have much less trouble resolving issue. You can think OSI model as map for the path that your data takes. if your data is not completing the path ,. Then you can check the each “way point” on the map until you find the area that is causing the problem.

**Visala28** · 09-05-2011

Whenever I got problem regarding the internet issue, that time I would immediately visualize the OSI model. Suppose if the problem can’t bring up a graphic error in downloading form the internets. That graphic is bought u in an application (layer 7). I could either start at the top or the bottom, depending on what I suspected was the problem. I would usually start at the bottom and try to find main cause by checking one by one layer until to solve.

**Sabastiaan** · 09-05-2011

When we troubleshooting a network it is always sensible to approach the problems from the perspective of the OSI model. The OSI model or open system interconnection, model defines a networking frame work for implementing protocols in seven layers. In the OSI model you can individually trouble shoot every layer using the simple methods. If all of the other layers are working properly tested then this is usually just a matter of applying patches to software or reinstalling.

**Candace** · 09-05-2011

Troubleshooting from layer 1 to layer 7 of the model is what makes you master the technology, rather than someone who has spent weeks or even month studying to pass an eight hour configuration exercise. Before using the OSI model architecture you should have to know the function of seven layer after that you start the checking the layer from bottom to top until to problem is not solves.

**Raja Ram** · 13-05-2011

While troubleshooting networking it is all the time sane to approach the trouble from the perspective of the OSI model. The OSI, or unlock System Interconnection, model classifies a networking framework for implementing protocols in 7 layers. The loveliness of this model is the truth that you can alone troubleshoot each layer using easy methods. I suggest functioning from layer 1 upwards until you discover the trouble.

Physical, Layer 1: This layer expresses the bit stream- electrical desire, light or radio signal-- through the network at the electrical and perfunctory level. It offers the hardware means of sending and receiving facts on a carrier, counting defining cables, cards and corporal aspects. Speedy Ethernet, RS232, and ATM are protocols with physical layer apparatus.

Data Link, Layer 2: At this layer, data packets are prearranged and cracked into bits. It provides transmission protocol facts and management and holds errors in the physical layer, flow control and frame organization. The data link layer is alienated into two sub layers: The Media Access Control (MAC) layer and the Logical Link Control (LLC) layer. The MAC sub layer manages how a PC on the network increases access to the data and consent to transmit it. The LLC layer controls frame synchronization, flow control and fault checking.

Network, Layer 3: This layer offers switching and routing skills, making logical paths, identified as virtual circuits, for conveying data from node to node. Routing and forwarding are functions of this layer, in addition to addressing, error handling, overcrowding control and packet sequencing. This is a huge part to wrap in a short tutorial. It wraps the routing protocols plus the routed protocols. You can troubleshoot IP with ICMP packets. Services like ping and tracert utilize ICMP packets to acquire replies back from networked hosts. Packet sniffers can be setup to seem at IP packets travelling across your hubs / switches in the similar way as you would seem at frame headers.

Transport, Layer 4: This layer gives transparent transfer of data between end systems, or hosts, and is accountable for end-to-end fault recovery and flow control. It makes sure whole data transfer. The majority of the troubleshooting here would be made with a packet sniffer. TCP is utilized with IP as a means to make sure that the data within the packets is sent and received lacking any defeat. If there is a fault, packets are re-sent (it would be appeal googling TCP packet header formation) with the right series number so that no data is mislaid (it make sure total data transfer).

Session, Layer 5: This layer institutes, manages and ends connections between applications. The session layer sets up, coordinates, and ends conversations, exchanges, and discourses between the applications at every end. It deals with session and connection organization. The most probable thing you would be troubleshooting at this layer would be NetBIOS over TCP/IP. Windows has a few very helpful utilities like netstat and the group of 'net' controls that will assist you.

Presentation, Layer 6: This layer gives autonomy from dissimilarities in data representation (e.g., encryption) by interpreting from application to network format, and vice versa. The presentation layer works to change data into the form which the application layer can admit. This layer formats and encrypts data to be sent over a network, providing liberty from compatibility troubles. It is occasionally called the syntax layer.

Application, Layer 7: This layer sustains application and end-user procedures. Communication partners are recognized, quality of service is recognized, user verification and privacy are measured, and any constraints on data syntax are recognized. The whole thing at this layer is application-precise. This layer offers application services for file relocates, e-mail, and added network software services. Telnet and FTP are applications which exist completely in the application level.

**Visala28** · 13-05-2011

I concur that the term virtual path denotes the logical path that the data in fact takes while travelling from 1 Router to the next. Obviously in the Network Layer (Where the Routers role), the data travels in the shape of packet enclosing source and destination IP address. The data travelling all through the network initial from 1st layer of OSI model to the last layer is constantly logical (not seen from naked eyes). But the logical addressing which you are talking about is in fact the IP addressing that just arises at the Network Layer (3rd Layer) of OSI Reference model.

**Candace** · 13-05-2011

The OSI layers are most significant thing in networking:

Application layers: Deals with network services which interrelate with the user for example http, ftp, email, DNS etc. Troubles allied to browsers, ftp programs, email and network / internet programs can begin here.
Presentation: Deals with data depiction (data formatting) and encryption. Instances of technologies at this layer are ASCII, EBCDIC.
Session: Deals with inter-host statement and is dependable for unlocking, closing and organizing a session.
Transport: Deals with end to end connections, delivery of data and dependability. Instances of technologies at this layer are TCP / UDP and port numbers.
Network: Deals with rational address and routing (path fortitude) that comprises IP addressing.
Data link: Deals with substantial addressing (MAC / LLC) and is dependable for getting data to other locations (LAN/WAN).
Physical: Media, signal and binary diffusion. Placing the data on to the physical medium.