CCP TCP/IP & OSI Model Layers 2 — Questions and Answers
Question 1: Which OSI layer is responsible for end-to-end error detection and flow control between two hosts?
- Network layer
- Data Link layer
- Transport layer (Correct answer)
- Session layer
Correct answer: Transport layer
The Transport layer (Layer 4) provides end-to-end error detection, flow control, and reliable data delivery between hosts.
Question 2: In the TCP three-way handshake, what is the correct sequence of messages?
- SYN, ACK, SYN-ACK
- SYN, SYN-ACK, ACK (Correct answer)
- ACK, SYN, SYN-ACK
- SYN-ACK, SYN, ACK
Correct answer: SYN, SYN-ACK, ACK
The TCP three-way handshake follows SYN → SYN-ACK → ACK to establish a reliable connection.
Question 3: What does the TTL field in an IP packet header primarily control?
- Packet encryption lifetime
- Maximum number of router hops before discard (Correct answer)
- Time the packet waits in a queue
- Duration of a TCP session
Correct answer: Maximum number of router hops before discard
TTL (Time To Live) is decremented by each router; when it reaches zero the packet is discarded, preventing infinite routing loops.
Question 4: Which TCP/IP layer corresponds to both the OSI Data Link and Physical layers?
- Internet layer
- Transport layer
- Network Access layer (Correct answer)
- Application layer
Correct answer: Network Access layer
The TCP/IP Network Access (Link) layer encompasses the functions of both the OSI Physical and Data Link layers.
Question 5: A router operates at which OSI layer to make forwarding decisions?
- Layer 1 – Physical
- Layer 2 – Data Link
- Layer 3 – Network (Correct answer)
- Layer 4 – Transport
Correct answer: Layer 3 – Network
Routers operate at Layer 3 (Network) and use IP addresses in packet headers to make forwarding decisions.
Question 6: What is the maximum segment size (MSS) negotiated during?
- IP fragmentation
- TCP connection establishment (Correct answer)
- UDP datagram assembly
- ARP resolution
Correct answer: TCP connection establishment
MSS is negotiated in the SYN and SYN-ACK segments during TCP connection establishment to avoid IP fragmentation.
Question 7: Which protocol at the Internet layer resolves a known IP address to a MAC address on a local network?
- RARP
- ICMP
- ARP (Correct answer)
- DHCP
Correct answer: ARP
ARP (Address Resolution Protocol) broadcasts a request on the local segment to discover the MAC address corresponding to an IP address.
CCP TCP/IP & OSI Model Layers 2
Which OSI layer is responsible for end-to-end error detection and flow control between two hosts?