The OSI model is a useful tool in troubleshooting a network

The OSI model is a useful tool in troubleshooting a network because it enables you to isolate a problem to a particular software module or piece of hardware. In this project, after reading the description of a problem, identify the OSI model layer or layers that are most likely involved.

1) One of your servers has been exhibiting sluggish network performance. you use a network-monitoring program to try to evaluate the problem.You find considerable TCP retries occuring because the servrt is being overhelmed by data,and packets are been discarded.

2) You check some statistics generated by a network-onitoring program and discovers that an abnormally high number of CRC errors were detected. (Hint think of the cause of CRC errors).

3) A user is trying to connect to another computer,but the logon attempt is continually rejected.

4) you try to access a linux server to share files by using NFS. You can communicate with the server but the shared files dont appear to be available.

Solution

1) One of your servers has been exhibiting sluggish network performance. you use a network-monitoring program to try to evaluate the problem.You find considerable TCP retries occuring because the server is being overhelmed by data,and packets are been discarded.

---->> Here in the above case among 7 layers of Open System Interconncetion(OSI) mostly TRANSPORT LAYER (4th layer of OSI) involved.

      (i) Transport Layer is responsible for delivering messages between hosts.

      (ii) In Transport layer, data travels in the form of segments. Transport layer is responsible for creating an end to end connection between source IP and the destination IP.

      (iii) For establishing this end to end connection, Transport layer is using two major protocols TCP and UDP. TCP is connection oriented protocol where UDP is connection less protocol. So by using TCP we can create an end to end reliable connection between source and destination hosts.

2) You check some statistics generated by a network-onitoring program and discovers that an abnormally high number of CRC errors were detected.

---->> Here in this case abnormally high number of Cyclic Redundancy Check(CRC) errors were deteced so, here among 7 layers of Open System Interconncetion(OSI) DATA LINK LAYER (2nd layer of OSI) involved.

=> Data Link Layer is responsible for error checks like CRC.

=> Errors in the received frames are detected by means of Parity Check and CRC. In both cases, few extra bits are sent along with actual data to confirm that bits received at other end are same as they were sent. If the counter-check at receiver end fails, the bits are considered corrupted.

3) A user is trying to connect to another computer,but the logon attempt is continually rejected.

--->> Here in this case user is trying to connect to another computer but continually rejected. So here in this situation SESSION LAYER(5th layer of OSI) is involved.

4) you try to access a linux server to share files by using NFS. You can communicate with the server but the shared files dont appear to be available.

--->> Here in this case among 7 layers of OSI APPLICATION LAYER(7th layer of OSI) is involved.

=> The application layer provides services for an application program to ensure that effective communication with another application program in a network is possible.