Design issues for the layers | Addressing | Direction of Transmission | Scalability | Routing | Reliability | Error Control | Flow Control | Multiplexing and De-multiplexing | Confidentiality and Integrity
The following are the design issues for the layers:
- There are multiple processes running on one machine.
- Every layer needs a mechanism to identify senders and receivers.
- Since there are multiple possible destinations, some form of addressing is needed in order to specify a specific destination.
II) Direction of Transmission:
Based on system communication, system are classified as:
- Simplex Systems.
- Half Duplex Systems.
- Full Duplex Systems.
- When network gets large, new problem arises.
- Thus scalability is important so that network can continue to work well when it gets large.
- When there are multiple paths between source and destination, only one route must be chosen.
- This decision is made on the basis of several routing algorithms, which chooses optimized route to the destination.
- It is a design issue of making a network that operates correctly even when it is made up of unreliable components.
VI) Error Control:
- It is an important issue because physical communication circuits are not perfect.
- Many error detecting and error correcting codes are available.
- Both sending and receiving ends must agree to use any one code.
VII) Flow Control:
- If there is a fast sender at one end sending data to a slow receiver, then there must be flow control mechanism to control the loss of data by slow receivers.
- There are several mechanisms used for flow control such as increasing buffer size at receivers, slow down the fast sender, and so on.
- Some process will not be in position to accept arbitrarily long messages.
- This property leads to mechanisms for disassembling, transmitting and the reassembling messages.
VIII) Multiplexing and De-multiplexing:
- If the data has to be transmitted on transmission media separately, it is inconvenient or expensive to setup separate connection for each pair of communicating processes.
- So, multiplexing is needed in the physical layer at sender end and de-multiplexing is need at the receiver end.
IX) Confidentiality and Integrity:
- Network security is the most important factor.
- Mechanisms that provide confidentiality defend against threats like eavesdropping.
- Mechanisms for integrity prevent faulty changes to messages.