Questions and Answers
What is added to the original data at the data link layer to create a frame?
Error detection or correction codes and MAC addresses
What is responsible for transmitting raw bits over the physical medium?
Physical layer
What type of addresses are typically included in the header at the data link layer?
MAC addresses
What is the purpose of the error detection or correction codes in the trailer?
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What type of information is not added to the data at the physical layer?
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What does the term 'PDU' stand for in networking and telecommunications?
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At which layer of the networking protocol stack are sequence numbers, acknowledgment numbers, and error detection codes added to the data?
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What is the name of the PDU at the Data Link Layer?
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What is added to the data at the Network Layer?
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At which layer of the networking protocol stack do protocols define their own data structures, headers, and formatting specific to their requirements?
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Study Notes
PDU (Protocol Data Unit)
- Smallest unit of data exchanged over a particular protocol or network layer
- Different PDUs at each layer of the networking protocol stack
PDUs at Each Layer
- Physical Layer: Bit
- Data Link Layer: Frame
- Network Layer: Packet
- Transport Layer: Segment (TCP) or Datagram (UDP)
- Application Layer: Message, Data
Information Added to Data at Each Layer
Application Layer
- No standardized way of adding information
- Protocols define their own data structures, headers, and formatting
- Examples: HTTP headers (request type, content type, cookies), FTP, SMTP
Transport Layer
- Original data divided into smaller segments or datagrams
- Header includes source and destination port numbers for correct delivery
- Additional information: sequence numbers, acknowledgment numbers, error detection codes (e.g., checksums)
Network Layer
- Original data encapsulated into a packet with a header and sometimes a trailer
- Header includes source and destination IP addresses for routing
- Additional information: protocol-specific details, Time-to-Live (TTL) values, fragmentation flags, Quality of Service (QoS) parameters
Data Link Layer
- Header and trailer added to create a frame
- Header includes source and destination MAC addresses for unique identification
- Trailer often contains error detection or correction codes (e.g., cyclic redundancy check (CRC)) for data integrity
Physical Layer
- Responsible for transmitting raw bits over the physical medium
- No specific information added to the data
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