1) What are the three main types of LAN architecture? What are their primary characteristics?
Ans:- The three network architectures are bus, ring, and hub. There are others, but these three describe the vast majority of all LANs.
A bus network is a length of cable that has a connector for each device directly attached to it. Both ends of the network cable are terminated. A ring network has a central control unit called a Media Access Unit to which all devices are attached by cables. A hub network has a backplane with connectors leading through another cable to the devices.
2) What are the seven OSI layers and their responsibilities?
Ans:- The OSI layers (from the bottom up) are as follows:
Physical: Transmits data
Data Link: Corrects transmission errors
Network: Provides the physical routing information
Transport: Verifies that data is correctly transmitted
Session: Synchronizes data exchange between upper and lower layers
Presentation: Converts network data to application-specific formats
Application: End-user interface
3) What is the difference between segmentation and reassembly, and concatenation and separation?
Ans:- Segmentation is the breaking apart of a large N-service data unit (N-SDU) into several smaller N-protocol data units (N-PDUs), whereas reassembly is the reverse.
Concatenation is the combination of several N-PDUs from the next higher layer into one SDU. Separation is the reverse.
Define multiplexing and demultiplexing. How are they useful?
Multiplexing is when several connections are supported by a single connection. According to the formal definition, this applies to layers (so that three presentation service connections could be multiplexed into a single session connection). However, it is a term generally used for all kinds of connections, such as putting four modem calls down a single modem line. Demultiplexing is the reverse of multiplexing, in which one connection is split into several connections.
Multiplexing is a key to supporting many connections at once with limited resources. A typical example is a remote office with twenty terminals, each of which is connected to the main office by a telephone line. Instead of requiring twenty lines, they can all be multiplexed into three or four. The amount of multiplexing possible depends on the maximum capacity of each physical line.
4) How many protocol headers are added by the time an OSI-based e-mail application (in the application layer) has sent a message to the physical layer for transmission?
Ans:- Seven, one for each OSI layer. More protocol headers can be added by the actual physical network system. As a general rule, each layer adds its own protocol information
Ans:- The three network architectures are bus, ring, and hub. There are others, but these three describe the vast majority of all LANs.
A bus network is a length of cable that has a connector for each device directly attached to it. Both ends of the network cable are terminated. A ring network has a central control unit called a Media Access Unit to which all devices are attached by cables. A hub network has a backplane with connectors leading through another cable to the devices.
2) What are the seven OSI layers and their responsibilities?
Ans:- The OSI layers (from the bottom up) are as follows:
Physical: Transmits data
Data Link: Corrects transmission errors
Network: Provides the physical routing information
Transport: Verifies that data is correctly transmitted
Session: Synchronizes data exchange between upper and lower layers
Presentation: Converts network data to application-specific formats
Application: End-user interface
3) What is the difference between segmentation and reassembly, and concatenation and separation?
Ans:- Segmentation is the breaking apart of a large N-service data unit (N-SDU) into several smaller N-protocol data units (N-PDUs), whereas reassembly is the reverse.
Concatenation is the combination of several N-PDUs from the next higher layer into one SDU. Separation is the reverse.
Define multiplexing and demultiplexing. How are they useful?
Multiplexing is when several connections are supported by a single connection. According to the formal definition, this applies to layers (so that three presentation service connections could be multiplexed into a single session connection). However, it is a term generally used for all kinds of connections, such as putting four modem calls down a single modem line. Demultiplexing is the reverse of multiplexing, in which one connection is split into several connections.
Multiplexing is a key to supporting many connections at once with limited resources. A typical example is a remote office with twenty terminals, each of which is connected to the main office by a telephone line. Instead of requiring twenty lines, they can all be multiplexed into three or four. The amount of multiplexing possible depends on the maximum capacity of each physical line.
4) How many protocol headers are added by the time an OSI-based e-mail application (in the application layer) has sent a message to the physical layer for transmission?
Ans:- Seven, one for each OSI layer. More protocol headers can be added by the actual physical network system. As a general rule, each layer adds its own protocol information
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