Exam weight Low
- Data communication → networks (connections, topologies) → LAN / MAN / WAN → the Internet and ISPs → standards.
- Tutorial 1 covers this whole deck: scenarios, MCQs, true/false, fill-in and link counts.
Exam weight Low
- Three sections: 1.1 data communications, 1.2 networks, 1.3 network types (plus the Internet and standards at the end).
Exam weight Low
- Data communication = exchanging data between TWO devices over some transmission medium (wire, fiber, air).
★ Tutorial
Exam weight High
- The 5 components: message, sender, receiver, transmission medium, protocol.
- The protocol sits on BOTH sides: sender and receiver must follow the same rules.
Memory trick“My Sister Reads The Paper”: Message, Sender, Receiver, Transmission medium, Protocol.
Exam trapThe medium is the physical path. The protocol is the set of rules. Don’t swap them.
Asked in a course tutorial
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MCQ
The __________ is the physical path over which a message travels.
Tutorial 1, MCQ 1. The medium is the path; the protocol is the rules.
MCQ
Which is NOT one of the five components of a data communication system?
Correct: Router.
Written
List the five components of a data communication system.
Message, sender, receiver, transmission medium and protocol.
Exam weight Medium
- Everything becomes bits: text (Unicode), numbers (binary), images (bit patterns), audio and video (continuous or a series of images).
🎯 How this can come up · 1 question
MCQ
Text is represented in data communication as:
Correct: A bit pattern using Unicode.
Exam weight High
- Node = any device (host or router/switch). Link = the pathway between nodes.
- Point-to-point = a dedicated link for two devices; multipoint = one link shared by more than two.
- The 3 criteria: performance (throughput + delay), reliability (failure frequency + recovery time) and security.
Exam trapMore throughput and less delay pull against each other: pushing more data in raises the delay.
Memory trickCriteria = “PRS”: Performance, Reliability, Security.
Asked in a course tutorial
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MCQ
Frequency of failure and recovery time after a failure measure a network’s:
Tutorial 1, MCQ 5.
MCQ
Network performance is evaluated by:
Correct: Throughput and delay.
True / False
Increasing throughput usually also increases delay.
True. More data in the network means more queuing, so delay grows.
Written
List and explain the three criteria of an effective network.
Performance: throughput (data a user can send) and delay (transit and response time). Reliability: how often it fails and how long a link takes to recover. Security: protecting data from unauthorized access and damage, with policies for recovering from breaches.
Exam weight Medium
- Point-to-point: a DEDICATED link between exactly two devices. Wired or wireless both count.
🎯 How this can come up · 1 question
True / False
A point-to-point connection can be wireless.
True. The figure shows a microwave/satellite link as point-to-point.
★ Tutorial
Exam weight High
- Multipoint = the link’s capacity is SHARED, in space (all at once) or in time (taking turns).
Asked in a course tutorial
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MCQ
In a __________ connection, more than two devices can share a single link.
Tutorial 1, MCQ 2.
★ Tutorial
Exam weight High
- Simplex: one direction only, always (keyboard → computer, TV, radio).
- Half-duplex: both directions, but one at a time; each side gets the whole channel while sending (walkie-talkie).
- Full-duplex: both directions at the same time; the channel capacity is shared by the two directions (telephone).
Memory trickHalf-duplex = “over” on a walkie-talkie. Full-duplex = talking over each other on the phone.
Asked in a course tutorial
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True / False
In full-duplex transmission, both stations can transmit and receive simultaneously.
True. Tutorial 1, T/F 1.
MCQ
A walkie-talkie is an example of:
Correct: Half-duplex.
MCQ
In which mode is the channel capacity shared by both directions at all times?
Tutorial 1, fill-in 2.
Written
Explain the difference between half-duplex and full-duplex, with a real example of each.
Half-duplex: both sides can send but not at the same time, so they take turns and the sender uses the whole channel (walkie-talkie). Full-duplex: both send and receive at the same time and the capacity is split between the two directions (telephone call).
Exam weight Low
- Topology = how the network is physically laid out / how devices interconnect.
- Four basic ones: mesh, star, bus, ring (plus hybrids).
Memory trickFour topologies: “My Star Bus Rings” (Mesh, Star, Bus, Ring).
★ Tutorial
Exam weight High
- Every device has a dedicated link to every other one. Links = N(N-1)/2; each device needs N-1 ports (NICs).
- Expensive because of all the cabling and ports: that is the answer to “why?”.
Memory trickN = 8 → 8 × 7 / 2 = 28 links, 7 ports per device.
Exam trapPorts per device is N-1, not N(N-1)/2.
Asked in a course tutorial
🎯 How this can come up · 4 questions
MCQ
How many links are needed for a fully connected mesh of 6 devices?
6 × 5 / 2 = 15.
MCQ
In a mesh of 10 devices, how many I/O ports does each device need?
N - 1 = 9.
True / False
A mesh topology has no traffic (congestion) problems because each link is dedicated.
True.
Written
A network has 8 devices. How many cable links does a mesh, ring, bus and star need?
Mesh: 8 × 7 / 2 = 28. Ring: 8. Bus: 1 main cable + 8 drop lines. Star: 8 (one per device to the hub).
★ Tutorial
Exam weight High
- Each device links only to the central hub/switch, so devices never talk directly.
- Single point of failure: the hub. One cable failing only cuts off one device.
Exam trapRobust ≠ fault-proof: one bad link only takes out its device, but the hub failing takes out everything.
Asked in a course tutorial
🎯 How this can come up · 2 questions
MCQ
Which topology requires a central controller or hub?
Tutorial 1, MCQ 3.
Scenario
A 20-employee office wants every computer connected to one central device, easy to manage and to grow. Which topology, and why?
Star. Every PC has its own link to a central switch, so adding or removing a PC is easy, a broken cable only affects one PC, faults are easy to find, and it needs less cabling than a mesh. The switch is the single point of failure.
★ Tutorial
Exam weight High
- One long backbone cable; each device hangs off it on a drop line through a tap.
- A break in the backbone stops ALL transmission, and faults are hard to isolate.
TipFormulas for N devices: mesh N(N-1)/2 links and N-1 ports each · star N links · ring N links · bus 1 main cable + N drop lines.
Asked in a course tutorial
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True / False
In a bus topology, one break in the cable can stop all transmissions on the segment.
True. Tutorial 1, T/F 4.
MCQ
A main cable plus N drop lines describes:
Correct: Bus.
Exam weight Medium
- Each device links to its two neighbours; the signal goes round the ring through each device’s repeater.
- Not robust: one broken link or device can break the ring (unless it is a dual ring).
🎯 How this can come up · 2 questions
MCQ
A ring of 12 devices needs how many links?
Ring: N links.
True / False
Fault isolation is easy in a ring topology.
True. Listed as an advantage on the slide.
Exam weight Medium
- Hybrid = a mix, e.g. a star backbone with buses or rings hanging off it.
Related tutorial questions
★ Tutorial
Exam weight High
- Classified by size: LAN (room → campus, ~1 km), MAN (a city, ~10 km), WAN (country / continent).
- A LAN does NOT cover more than about 2 miles: that is the Tutorial 1 trap.
Asked in a course tutorial
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True / False
A LAN typically covers an area larger than 2 miles in diameter.
False. Tutorial 1, T/F 2. LANs cover a room, building or campus.
MCQ
A network spanning a city is a:
Correct: MAN.
Exam weight Low
- Past LANs: all hosts on a shared cable (bus). Today: every host has its own link to a switch (star).
Exam weight Low
- MAN: covers a town or city, often run by a telecom company (the slide’s example: STC).
Exam weight Low
- LANs are built in layers: switches per building, a faster backbone switch, one router out to the Internet.
★ Tutorial
Exam weight High
- Internetwork (an internet, small i) = two or more networks joined by routers.
- The Internet (capital I) is one specific, worldwide internet.
Asked in a course tutorial
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True / False
An internet (lowercase i) is the same as the Internet (uppercase I).
False. Tutorial 1, T/F 5. Any two connected networks form an internet; the Internet is the global one.
Exam weight Low
- Real networks mix LANs and point-to-point WANs; routers sit at every boundary.
★ Tutorial
Exam weight Medium
- WAN: countries and continents. Usually a mesh or hybrid of point-to-point links.
Asked in a course tutorial
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Scenario
A company links its New York headquarters with offices in London, Tokyo and Sydney, needing high-speed, reliable and secure links. What kind of network and topology fit?
A WAN. A mesh (or hybrid mesh) of dedicated point-to-point links between the sites gives redundancy if one link fails, dedicated capacity, and better security for the financial data.
Exam weight High
- The Internet = many networks that all run TCP/IP.
- To be “on the Internet” a host must run TCP/IP, have an Internet (IP) address, and send IP packets.
Asked in a course tutorial
🎯 How this can come up · 1 question
MCQ
__________ is the protocol suite of the current Internet.
Tutorial 1, MCQ 4.
Exam weight High
- Tier 1 = backbones: international, few of them, own their links, connect directly to each other.
- Tier 2 = national/regional providers (STC, Mobily); connect to at least one tier-1.
- Tier 3 = local ISPs that buy service from the national providers.
Memory trickTier number goes UP as you get closer to the customer: 1 = global, 2 = national, 3 = local.
🎯 How this can come up · 2 questions
MCQ
STC and Mobily are examples of:
Correct: Tier-2 (provider network) ISPs.
True / False
Tier-1 ISPs connect directly to other tier-1 ISPs.
True.
Exam weight Low
- A tier-1 network owns links on every continent.
Exam weight Low
- Local and tier-3 ISPs are customers of the higher tiers; the “last hop” to end systems is the access network.
Exam weight Low
- Backbones in the middle, joined at peering points; provider networks hang off them; customers at the edge.
Exam weight High
- Private peering: ISPs connect directly; the points are owned and run by the ISPs themselves.
- IXP (public peering): a third party runs a high-speed switching network where any ISP can connect.
- Today: international ISPs use private peering; national ISPs meet at IXPs.
Exam trapPrivate peering points are run by the ISPs; an IXP is run by a THIRD party.
🎯 How this can come up · 2 questions
MCQ
An Internet Exchange Point (IXP) is managed by:
Correct: A third party.
True / False
National ISPs usually interconnect using IXPs.
True.
Exam weight Low
- Customers of each ISP reach each other through the IXP instead of going abroad. Example: the Saudi Arabian Internet Exchange.
Exam weight High
- Early vendor networks could not talk to each other without translation software, which is why we need standards.
- Protocol = a set of rules controlling data exchange between two entities in a system.
Exam trap“A protocol is the structure or format of the data” ✗. That is only syntax, one element of a protocol.
Asked in a course tutorial
🎯 How this can come up · 2 questions
True / False
A protocol is defined as the structure or format of data.
False. Tutorial 1, T/F 3. That is syntax; a protocol is the whole set of rules.
MCQ
A protocol is best defined as:
Correct: A set of rules controlling data exchange.
Exam weight Medium
- Standards = interoperability: gear from different vendors can work together.
- Agreements are needed at many levels: voltages for 0/1, message boundaries, lost messages, addressing, routing, applications. Each turns into a layer later.
Asked in a course tutorial
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Written
Why are standards important in data communications? Give examples.
They guarantee interoperability between equipment from different vendors, create a large market for hardware and software, and guide manufacturers and agencies. Examples: Ethernet (IEEE 802.3) lets any NIC talk to any switch; TCP/IP lets any computer join the Internet.
Exam weight Medium
- ISO (international), ITU-T (UN telecom agency), ANSI (US), IEEE (LAN/MAN, e.g. 802.3 Ethernet), W3C (the web).
Seen again
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MCQ
Which organization specializes in LAN/MAN standards?
Correct: IEEE.
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