2026 QUESTIONS WITH SOLUTIONS GRADED
A+
⫸ Protocol. Answer: - controls sending and receiving of messages
- set of invisible computer rules that govern how an internet document
gets transmitted to your screen
⫸ Access Network. Answer: - network that physically connects an
end system to the first router on a path form the end system to any
other distant end system
Examples:
- Home Access - DSL, Cable, Dial-Up, Satellite
- Access in Enterprise and Home - Wi-Fi and Ethernet
- Wide-area Wireless Access - 3G or LTE
⫸ DSL. Answer: - Digital Subscriber Line
- use existing telephone line to central office DSLAM
⫸ Cable Network. Answer: - Frequency division multiplexing:
different channels transmitted in different frequency bands
,⫸ Enterprise Access Networks (Ethernet). Answer: - typically used
in companies, universities, etc.
⫸ Wireless Access Networks. Answer: - shared wireless access
network connects end system to router via base station aka "access
point"
- wireless LANs: within building
- wide-area wireless access: provided by cellular operator
⫸ Physical Link. Answer: - what lies between transmitter and
receiver
- Guided Media: twisted-pair copper wire, coaxial cable, fiber optics
- Unguided Media (signal carried in electromagnetic spectrum; no
physical wires): terrestrial radio channels, satellite radio channels
⫸ The Network Core. Answer: - packet switching, circuit switching,
a network of networks
⫸ Packet Switching. Answer: - break long messages into packets
- store-and-forward transmission
- queuing delays and packet loss
- forwarding tables and routing protocols
⫸ Formula Needed for Packet Switching. Answer: R (bit/sec) = full
transmission rate of the link
L (bits) = packet size
, Transmission Time (sec) = L/R
⫸ Circuit Switching. Answer: - the resources must be reserved
- multiplexing in circuit-switching networks: FDM and TDM
⫸ Store-and-Forward Transmission. Answer: - packet switch must
receive the entire packet
⫸ 3 packets and 2 links. What is the time to receive all 3 packets?.
Answer: 4L/R
⫸ If L = 7.5 Mbits and R = 1.5 Mbps. What is the transmission
time?. Answer: 5 sec
⫸ Key Network-core Functions. Answer: routing and forwarding
⫸ Routing. Answer: - determines source-destination route taken by
packets (routing algorithms)
⫸ Forwarding. Answer: - move packets from router input to
appropriate router output
⫸ Queuing and Packet Loss. Answer: - if arrival rate (in bits) to link
exceeds transmission rate of line for a period of time:
- packets will queue, wait to be transmitted