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Questions and Answers
What is a key characteristic of token ring networks compared to Ethernet?
What is a key characteristic of token ring networks compared to Ethernet?
Which of the following statements about data transfer rates of token ring networks is true?
Which of the following statements about data transfer rates of token ring networks is true?
What is a disadvantage of token ring networks compared to Ethernet?
What is a disadvantage of token ring networks compared to Ethernet?
How do token ring networks prevent data collisions?
How do token ring networks prevent data collisions?
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Which statement is true regarding the current use of token ring networks?
Which statement is true regarding the current use of token ring networks?
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What happens when a node wants to transmit data in a token ring network?
What happens when a node wants to transmit data in a token ring network?
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What is the main consequence of a node failure in a token ring network?
What is the main consequence of a node failure in a token ring network?
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Which token indicates that it is busy in a token ring network?
Which token indicates that it is busy in a token ring network?
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What mechanism is used for collision resolution in a token ring network?
What mechanism is used for collision resolution in a token ring network?
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What is a characteristic of Traditional Ethernet (IEEE 802.3)?
What is a characteristic of Traditional Ethernet (IEEE 802.3)?
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What type of address is a source address in a network?
What type of address is a source address in a network?
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Which Ethernet cabling type supports a maximum segment length of 100 meters?
Which Ethernet cabling type supports a maximum segment length of 100 meters?
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What is the consequence of having more stations in a network segment?
What is the consequence of having more stations in a network segment?
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What topology is used in both 10Base-T and 10Base-F Ethernet?
What topology is used in both 10Base-T and 10Base-F Ethernet?
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How many possible LAN addresses can be provided by NICs?
How many possible LAN addresses can be provided by NICs?
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What is the primary function of segmentation in a network?
What is the primary function of segmentation in a network?
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What is the main characteristic of a NIC's address?
What is the main characteristic of a NIC's address?
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When does a router transfer data from one network segment to another?
When does a router transfer data from one network segment to another?
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What is the primary characteristic of Pure ALOHA?
What is the primary characteristic of Pure ALOHA?
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What is the maximum utilization rate of the channel in Pure ALOHA?
What is the maximum utilization rate of the channel in Pure ALOHA?
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Which method organizes time into uniform slots for transmission?
Which method organizes time into uniform slots for transmission?
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In CSMA, what is the initial step a station must take before transmitting?
In CSMA, what is the initial step a station must take before transmitting?
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What happens if a station in Pure ALOHA fails to receive an acknowledgment after repeated transmissions?
What happens if a station in Pure ALOHA fails to receive an acknowledgment after repeated transmissions?
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What does the CSMA method aim to minimize?
What does the CSMA method aim to minimize?
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What technique is needed to prevent unwanted collisions in Slotted ALOHA?
What technique is needed to prevent unwanted collisions in Slotted ALOHA?
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Which of the following statements is true regarding collisions in CSMA?
Which of the following statements is true regarding collisions in CSMA?
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What is the primary function of a Local Area Network (LAN)?
What is the primary function of a Local Area Network (LAN)?
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Which layers of the OSI model do LAN protocols primarily address?
Which layers of the OSI model do LAN protocols primarily address?
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What is the role of the MAC sub-layer in a LAN?
What is the role of the MAC sub-layer in a LAN?
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What are broadcast channels commonly referred to as in LAN communications?
What are broadcast channels commonly referred to as in LAN communications?
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During data transmission, what initial action must be performed to prepare data for sending over a LAN?
During data transmission, what initial action must be performed to prepare data for sending over a LAN?
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What is a consequence of computers sharing a LAN?
What is a consequence of computers sharing a LAN?
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Which of the following is NOT a function at the physical layer of the IEEE 802 reference model?
Which of the following is NOT a function at the physical layer of the IEEE 802 reference model?
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How do higher layer protocols relate to LAN networks within the OSI model?
How do higher layer protocols relate to LAN networks within the OSI model?
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What is a characteristic of non-persistent collision detection?
What is a characteristic of non-persistent collision detection?
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In a p-persistent strategy, what happens if the line is idle?
In a p-persistent strategy, what happens if the line is idle?
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In CSMA/CD, what happens after a collision is detected?
In CSMA/CD, what happens after a collision is detected?
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What is the purpose of the exponential backoff method in CSMA/CD?
What is the purpose of the exponential backoff method in CSMA/CD?
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How does CSMA/CA handle data transmission?
How does CSMA/CA handle data transmission?
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What is the role of a 'jam' signal in collision detection?
What is the role of a 'jam' signal in collision detection?
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What is the primary function of token passing in networking?
What is the primary function of token passing in networking?
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What mechanism is specifically associated with wireless LANs to avoid collisions?
What mechanism is specifically associated with wireless LANs to avoid collisions?
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Study Notes
Local Area Networking Technology
- A local area network (LAN) is a data communication network that serves users in a confined geographic area. It uses high transmission speeds, typically from 10 Mbps to several Gbps.
- LANs are designed for communication and resource sharing in local work environments like rooms, campuses, or buildings.
- A LAN often uses a single shared medium (usually a cable) that computers can connect to. This sharing of resources leads to lower costs.
- LANs operate at the physical and data link layers of the OSI model.
- Higher-layer protocols (layers 3 and 4 or above) are independent of the network architecture; they can be used in LANs, MANs (Metropolitan Area Networks), and WANs (Wide Area Networks).
- LAN protocols primarily focus on the lower layers (1 and 2) of the OSI model.
- The lowest layer of the IEEE 802 reference model correlates with the physical layer, which includes encoding/decoding of signals, preamble generation/removal for synchronization, and bit transmission/reception.
Access Methods
- Broadcast channels, also known as multi-access or random access channels, are used in some LANs.
- Access methods decide how shared media is utilized in a multi-access channel. Protocols determine which device goes next.
- Media Access Control (MAC) acts as a sub-layer within the data link layer and plays a vital role in LANs. It's a key mechanism for multi-access channels.
- WANs (Wide Area Networks), in contrast, often use point-to-point links.
Pure ALOHA
- The earliest access method, often used in packet radio networks.
- It's considered a "true free-for-all" system.
- Stations wait for a time equal to the maximum round-trip propagation delay plus a small fixed increment.
- Stations only send if there's no acknowledgement after repeated transmissions; otherwise, it gives up.
- Collisions are frequent. The channel utilization is low, maxing out at about 18%.
Slotted ALOHA
- The channel is slotted, with each slot having a duration equivalent to the frame transmission time.
- A central clock is needed for synchronization (to maintain timing).
- Collisions are still possible, and retransmission occurs after a random delay.
CSMA (Carrier Sense Multiple Access)
- Stations "listen before talk," sensing the medium's status before transmitting.
- If the channel is busy, the station waits; otherwise, it transmits.
- Collisions still occur due to propagation delay. Stations do not know if another transmission is starting at the same moment.
CSMA/CD (Carrier Sense Multiple Access with Collision Detection)
- The system adds a collision detection to CSMA.
- If a collision is detected, the sender waits a random amount of time before trying to transmit again. Backoff time increases with consecutive collisions.
- The backoff times are calculated exponentially. The waiting time between 0 and 2N x maximum propagation time, where N is the number of attempted transmissions.
- A jamming signal alerts other stations to the collision and discards the affected frame.
CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance)
- Collision avoidance is preferred over collision detection.
- Uses one of the persistent strategies
- After the line is idle, it waits for an interframe gap (IFG).
- Then it waits for another random amount of time.
- Sends the frame, sets a timer. If an acknowledgment (ACK) is received before the timer expires, the transmission is successful. (Otherwise, there's a frame/ACK issue, so retry).
- Used for wireless LANs.
Token Passing
- A station is authorized to send data after it receives a token (a special frame).
- Stations are arranged in a ring.
- A token circulates around the ring when no data is being transmitted.
- Tokens are bit sequences. A "free token" is 01111110 and a "busy token" is 01111111.
- When a node needs to transmit, it waits for the free token.
- When done transmitting, it releases the busy token back into the ring and replaces it with a free token.
Token Bus
- Stations on the bus form a logical ring.
- The physical ordering of stations on the bus is irrelevant.
- Token passing medium access control protocol is used.
Token Ring
- Introduced by IBM in the early 1980s.
- Logical topology is a ring (or sometimes a star).
- Token-passing media access control is used.
- Only a station with the token can send data, and the token is released only when the data's receipt is confirmed.
Ethernet
- The most popular LAN physical architecture.
- Originally created in 1976 at Xerox's Palo Alto Research Center.
- Operates at 10 Mbps, with later iterations increasing to 100 Mbps, 1000 Mbps, and higher rates.
- Uses CSMA/CD or CSMA/CA (in newer versions).
- Ethernet frames are defined as 7 fields that include preamble, start field delimiter, destination address, source address, length/type, data and padding, and the cyclic redundancy check (CRC),
- Provides minimum and maximum frame lengths. Padding is used for packets smaller than the minimum size.
- Uses MAC (Media Access Control) addressing. Addresses are permanently burned into Network Interface Cards (NICs).
Fast Ethernet
- Enhanced Ethernet to provide higher data rates at 100 Mbps using similar architectures. A significant feature is Auto-negotiation, which allows incompatible devices to communicate.
Gigabit Ethernet
- Further advancement to 1000 Mbps.
- Uses protocols and interfaces that remain compatible with previous Ethernet standards.
Ethernet vs. Token Ring
- Ethernet's access is non-deterministic (contention-based); Token Ring is deterministic.
- Ethernet supports direct cable connections between NICs, while Token Ring does not.
- Ethernet uses CSMA/CD or CSMA/CA, and Token ring uses tokens to regulate access to the network media.
- Ethernet is generally less expensive than Token Ring.
Segmentation
- Used to split a large Ethernet network into smaller segments connected by routers.
- Reduces collisions and improves network performance by limiting the number of stations contending for access.
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Description
Test your knowledge on Local Area Networking (LAN) technologies and protocols. This quiz covers key concepts such as transmission speeds, OSI model layers, and the role of LAN in resource sharing. Perfect for students and professionals looking to enhance their understanding of networking fundamentals.
