CS Systems & Networking 3 — Questions and Answers
Question 1: A network admin notices a host can ping IP addresses but cannot load websites by name. Which service is most likely failing?
- DNS resolution (Correct answer)
- DHCP lease assignment
- ARP resolution
- NAT translation
Correct answer: DNS resolution
Working IP connectivity with failing name-based access points to a DNS problem.
Question 2: What condition must hold, among others, for a deadlock to occur in a system?
- Circular wait among processes holding resources (Correct answer)
- All processes running at the same priority
- More threads than CPU cores
- Use of virtual memory
Correct answer: Circular wait among processes holding resources
Deadlock requires mutual exclusion, hold-and-wait, no preemption, and circular wait.
Question 3: Why does UDP offer lower latency than TCP for real-time video streaming?
- It skips connection setup, acknowledgments, and retransmissions (Correct answer)
- It uses smaller IP headers
- It always takes shorter network routes
- It compresses payloads automatically
Correct answer: It skips connection setup, acknowledgments, and retransmissions
UDP avoids TCP's handshake, ordering, and retransmission overhead, trading reliability for speed.
Question 4: What does a Translation Lookaside Buffer (TLB) cache?
- Recent virtual-to-physical address translations (Correct answer)
- Recently executed instructions
- Disk blocks awaiting write-back
- Network routing table entries
Correct answer: Recent virtual-to-physical address translations
The TLB stores recent page table lookups to speed up virtual address translation.
Question 5: A subnet uses the mask 255.255.255.192. How many usable host addresses does it provide?
- 62 (Correct answer)
- 64
- 30
- 126
Correct answer: 62
A /26 subnet has 64 addresses, minus the network and broadcast addresses, leaving 62 usable hosts.
Question 6: Which system call replaces a process's current memory image with a new program?
- exec() (Correct answer)
- fork()
- wait()
- kill()
Correct answer: exec()
exec() loads a new program into the calling process, replacing its code and data.
Question 7: In the context of network switches, what does a MAC address table map?
- MAC addresses to switch ports (Correct answer)
- IP addresses to hostnames
- Ports to VLAN passwords
- MAC addresses to IP addresses
Correct answer: MAC addresses to switch ports
A switch learns which MAC addresses are reachable through which physical ports to forward frames efficiently.
CS Systems & Networking 3
A network admin notices a host can ping IP addresses but cannot load websites by name.
Which service is most likely failing?