Knowledge of OSI Reference Model

(3) Describe Data Link addresses and Network Address, and identify the key differences.

Data Link addresses are the source address and the destination address of the 48 bit BIA of the hardware NIC card. At each interface these addresses change because, on route to the destination a frame has to pass may INC cards. Address Resolution Protocol (ARP) finds the MAC address when it moves to a different segment. Network layer address has a source and a destination address, which are end points of the transmitting and receiving systems. It provides routing and relaying functions to achieve it goal. It provides a transparent path to the transport layer for a best end to end packet delivery service.

(4) Identify at least three reasons why industry uses a layered model

Layered model avoids interfering with the innovation of design and implementation of computer systems
Facilitates communication between dissimilar systems
Allow changes to one layer with out changing other layers
Facilitate systematic network trouble shooting
Reduce the complexity of networking into more manageable layers and sub layers

(5) Define and explain the five conversion steps of data encapculation

• · User information is converted to data
• · Data is converted to segments
• · Segments are converted to packets or datagrams
• · Packets or datagrams are converted to frames
• . Frames are converted to bits (1s and 0s)
  

(6) Define Flow Control and describe the three basic methods used in networkig

Flow control stops a sending station from flooding the receiver station buffers, if it has no resources to match the speed of data arriving from the receiving station. Once the buffers are emptied at the receiver, it sends a message to the transmitter to start sending again. It is called windowing and controls how much data is transmitted from one end to the other. Has a fixed window say 7, the transmitting station sends seven packets before waiting for an acknowledgement packet. Once the acknowledgement is received at the receiver, it sends another seven packets.

Window size of one. Every packet sent to the receiver has to be acknowledged before the transmitter can send the next packet.
Variable window, if the receiving station for some reason finds difficult to catch up with buffer emptying, it then tells receiver to reduce the window size and the sender does so.