CSMA/CD Protokoll

CSMA/CD

Flow Control

• CSMA/CD stands for Carrier Sense Multiple Access with Collision Detection
• Flow control: a mechanism to prevent network congestion by regulating the amount of data sent by a device
• In CSMA/CD, flow control is achieved through the use of acknowledgments (ACKs) and retransmissions
  • Sender waits for ACK before sending next packet
  • If no ACK received, sender retransmits packet

Access Method

• CSMA/CD is a contention-based access method
• Multiple Access: multiple devices share the same channel
• Carrier Sense: devices sense the channel before transmitting to detect if it's busy
• Collision Detection: devices detect collisions (when two devices transmit at the same time) and take corrective action
  • When a collision is detected, devices stop transmitting and wait for a random period before retrying

Message Encoding

• Manchester Encoding is commonly used in CSMA/CD networks
• Manchester Encoding: a method of encoding data bits into a signal
  • Each data bit is represented by a transition in the signal (high-to-low or low-to-high)
  • Provides a self-clocking signal, allowing the receiver to extract the original data bits

Message Encapsulation

• Frame: the basic unit of data transmission in CSMA/CD
• Frame structure: typically consists of:
  1. Preamble: a sequence of bits used to synchronize the receiver
  2. Destination Address: the address of the intended recipient
  3. Source Address: the address of the sender
  4. Data: the actual data being transmitted
  5. CRC (Cyclic Redundancy Check): a error-checking mechanism
  6. Frame Check Sequence (FCS): a 4-byte field used to detect errors
• Frame length: typically limited to a maximum of 1518 bytes (IEEE 802.3 standard)