Networks Flashcards

In CSMA/CD, after the k-th collision, a station waits a random number of slot times chosen from [0, 2^k - 1]. This is called:

Answer: Binary exponential backoff

Binary exponential backoff doubles the contention window after each successive collision, reducing the probability of repeated collisions.

Which layer of the OSI model is responsible for end-to-end error detection and flow control between hosts?

Answer: Transport layer

The transport layer (Layer 4) provides end-to-end reliable delivery, error detection, and flow control between communicating hosts.

A network uses Go-Back-N ARQ with a window size of 4. If frame 3 is lost, which frames must be retransmitted?

Answer: Frames 3, 4, 5, and 6

In Go-Back-N, when frame 3 is lost, the receiver discards all subsequent frames; the sender must retransmit frame 3 and all frames sent after it within the window.

Which protocol resolves an IP address to the corresponding MAC address on a local network?

Answer: ARP

ARP (Address Resolution Protocol) broadcasts an IP address query and receives the corresponding MAC address from the owning host.

The OSPF routing protocol is based on which algorithm?

Answer: Link state

OSPF (Open Shortest Path First) is a link-state protocol where each router maintains a complete topology map and runs Dijkstra's algorithm locally.

In a slotted ALOHA system, the maximum throughput is approximately:

Answer: 36.8%

Slotted ALOHA achieves maximum throughput of 1/e ≈ 36.8% when each station transmits with probability 1/N where N is the number of active stations.

Which field in the TCP header identifies the application-layer protocol on the receiving end?

Answer: Destination port

The destination port number in the TCP header identifies which application (e.g., HTTP on port 80) should receive the segment.