Transmission Modes in Computer Networks

Study Notes

Transmission modes describe how data travels between devices.
Modes differ in data transfer direction, sender-receiver synchronization, and the number of bits sent.

Simplex: Data flows in one direction only.
- One device sends, the other receives.
- Limited use in applications where responses aren't necessary.
- Examples include a radio station and a keyboard's input to a display.
- Advantage: Efficient use of the communication channel's full capacity, minimal data traffic concerns.
- Disadvantage: No way to return information, no acknowledgement mechanism.
Half-duplex: Data transmission in either direction, but not simultaneously.
- One device sends, the other receives, then the roles reverse.
- Example: Walkie-talkie.
- Advantage: Both devices can utilize the full bandwidth of the channel when transmitting in either direction.
- Disadvantage: Data transmission is delayed because one device must wait while the other transmits.
Full-duplex: Data transmission in both directions simultaneously.
- Two-way communication at the same time.
- Example: Telephone conversations, two-way communication in a modern network connection.
- Advantage: Fastest communication method, uses the entire bandwidth for both sending and receiving.
- Disadvantage: Inefficient channel bandwidth usage as there are two routes requiring maintenance, and separate physical paths.

Synchronous Transmission: Bits are sent continuously without start or stop bits.
- Data transfer is rapid, as there are no pauses (gaps).
- Disadvantage: Costly due to the needed intricate synchronization mechanism.
Asynchronous Transmission: Data transmission with start and stop bits.
- These bits signal the beginning and end of each data section.
- Allows data to be transferred at different timings.
- Advantage: Low cost and high accuracy.
- Disadvantage: Slower than synchronous transmission due to the start and stop bits.

Serial Transmission: Data bits are sent one after the other, using a single transmission line.
- This method is suitable for long-distance communication and where the amount of data transferred is minimal.
- Advantage: Reliable form of transmission. Less expensive and easier to implement.
- Disadvantage: Slow
Parallel Transmission: Bits are sent simultaneously across multiple transmission lines.
- Suitable for short-distance communication for high volumes of data.
- Advantage: Fast and convenient for short distance and large data.
- Disadvantage: More expensive, more complex setup, the wires must be closer to each other without interference.

Network devices use addresses to locate each other.
Addresses at different layers are used for communication: MAC (Media Access Control) addresses, IP (Internet Protocol) addresses, and port numbers.
The process involves identifying sender and receiver, adding the information (headers) to the data (encapsulation), and delivering it.
Packets are used for segmentation.

IP addresses are used for communication over networks like the internet.
Address types exist (Public, Private, Static, and Dynamic).
- Public IP addresses are publicly available across the internet, essential for communication over the internet.
- Private IP addresses are used within a local network and are never publicly exposed.
- Static IP addresses do not change.
- Dynamic IP addresses change over time.
IP addresses are classified into classes (A, B, C, D, E).
Each class has a specific range of addresses and a designated number of bits.

MAC addresses (Media Access Control) are hardware-assigned unique identifiers for network interfaces.
They are used for local network communication.
MAC addresses are usually unique to each device or adapter.

Port numbers are used with IP addresses to locate a specific application (program/service) on a device on a network.
They range from 0 to 65,535. Each port is assigned to a specific protocol.
Well-known port numbers are assigned to common applications (HTTP, FTP, SMTP).