Ethernet and LAN Protocols Quiz

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Questions and Answers

What is the primary advantage of using 1-persistent CSMA protocol in Ethernet networks?

It reduces the time wasted due to collisions since transmissions attempt to send immediately upon detecting the channel is clear.

What characterizes the 10Base5 Ethernet standard?

10Base5 uses a bus topology with a thick coaxial cable and an external transceiver connected via a tap.

How does 10Base-T differ from 10Base-F in Ethernet technology?

10Base-T utilizes twisted pairs of cable for communication, while 10Base-F employs fiber optic cables.

What is the maximum data rate of Fast Ethernet as specified by IEEE 802.3ae?

The maximum data rate of Fast Ethernet is 10 Gbps, or 10,000 Mbps. Signup and view all the answers

Describe the dual ring structure of FDDI and its purpose.

FDDI implements a dual ring where data transmission primarily occurs on the primary ring, while the secondary ring serves as a backup in case of failure. Signup and view all the answers

What are some key advantages of using FDDI in LAN environments?

FDDI offers high bandwidth up to 250 Gbps, resistance to electromagnetic interference, and support for up to 1000 terminals over 200 km. Signup and view all the answers

What are the challenges associated with the installation and maintenance of FDDI systems?

FDDI systems are costly and require substantial expertise for installation and maintenance. Signup and view all the answers

Why is p-persistent CSMA considered more stable compared to 1-persistent CSMA?

P-persistent CSMA reduces the likelihood of collisions by allowing stations to wait a calculated probability before transmitting. Signup and view all the answers

What is the main difference between contention and controlled access LAN standards?

Contention standards allow multiple stations to compete for access (e.g., Ethernet), while controlled access standards regulate access to the medium to avoid collisions (e.g., Token Ring). Signup and view all the answers

Describe the basic operation of Nonpersistent CSMA.

In Nonpersistent CSMA, if the medium is idle, a station transmits; if it is busy, the station waits a random amount of time before retrying. This reduces the probability of collisions. Signup and view all the answers

What are the characteristics of 1-persistent CSMA and how does it differ from Nonpersistent CSMA?

1-persistent CSMA allows stations to transmit immediately when the channel is idle and listen until it becomes idle if busy, resulting in higher chances of collisions. This differs from Nonpersistent CSMA, where stations wait randomly if the medium is busy. Signup and view all the answers

What is the purpose of using a probability 'p' in P-persistent CSMA?

The purpose of using probability 'p' in P-persistent CSMA is to reduce the chance of collisions while still minimizing idle time on the network by controlling the likelihood of transmission. Signup and view all the answers

Explain the implications of a high load on the effectiveness of P-persistent CSMA.

Under high load, the effectiveness of P-persistent CSMA can decrease due to increased collisions and delays as the probability value 'p' may not be effectively chosen for such conditions. Signup and view all the answers

Identify the IEEE LAN standard that corresponds to Token Ring and describe its access method.

Token Ring corresponds to the IEEE 802.5 standard and uses a controlled access method where a token circulates on the network, granting the right to transmit. Signup and view all the answers

What are the primary differences in managing collisions between contention-based and controlled access networks?

Contention-based networks, like Ethernet, allow collisions to occur and require retransmission, whereas controlled access networks, like Token Ring, prevent collisions by managing access through a token system. Signup and view all the answers

List the four IEEE LAN standards mentioned in the lecture and categorize them into contention and controlled access.

The four IEEE LAN standards are Ethernet (802.3) and Token Bus (802.4) as contention-based; Token Ring (802.5) and DQDB (802.6) as controlled access. Signup and view all the answers

What function does a Network Interface Card (NIC) serve in a computer network?

A NIC connects a computer to a network and handles packet processing. Signup and view all the answers

Explain the role of Carrier Sense Multiple Access (CSMA) in Local Area Networks (LANs).

CSMA allows devices to detect if a channel is free before transmitting, minimizing the chances of collisions. Signup and view all the answers

Why does CSMA/CD implement a random delay in its protocol?

CSMA/CD uses a random delay to prevent repeated collisions when multiple devices attempt to transmit at the same time. Signup and view all the answers

Briefly describe the contents of an Ethernet Frame.

An Ethernet Frame typically contains a preamble, source and destination MAC addresses, EtherType, payload data, and a Frame Check Sequence. Signup and view all the answers

Describe the operation of non-persistent CSMA/CD protocols.

In non-persistent CSMA/CD, a device waiting to transmit will sense the channel and only send data if it detects the channel is idle, otherwise, it waits a random amount of time to check again. Signup and view all the answers

What is 'binary exponential backoff' in networking protocols?

Binary exponential backoff is a collision handling strategy in which the wait time after a collision doubles with each subsequent attempt to transmit. Signup and view all the answers

What precautions should be taken to ensure reliable operation of a token ring network?

Precautions include ensuring proper installation of the token ring hardware, monitoring link integrity, and managing network traffic effectively. Signup and view all the answers

State Shannon's theorem regarding maximum data rates over noisy communication channels.

Shannon's theorem states that the maximum data rate (C) can be calculated with the formula $C = B \log_2(1 + S/N)$, where B is the bandwidth and $S/N$ is the signal-to-noise ratio. Signup and view all the answers

Study Notes

LAN Technologies

LAN technologies encompass various standards for local area networks.
LAN operations are categorized into contention and controlled access methods.
IEEE 802 standards define various LAN technologies.
Examples of IEEE standards include Ethernet (802.3), Token Bus (802.4), Token Ring (802.5), and DQDB (802.6).
FDDI is another controlled access method, an ANSI/ITU-T standard.
Network Interface Cards (NICs) are essential components for connecting devices to the network.

Lecture Objective

Understand LAN operations.
Learn IEEE LAN standards.
Explore Token Ring and FDDI operations.
Understand Network Interface Cards (NICs).

LAN Standards

Ethernet (IEEE 802.3) is a contention-based standard.
Token Bus (IEEE 802.4) is a controlled access standard.
Token Ring (IEEE 802.5) is another controlled access standard.
DQDB (IEEE 802.6) is a distributed queue dual bus standard.
Standards specify categories: contention (e.g., Ethernet) or controlled access (e.g., Token Ring).
FDDI is an ANSI/ITU-T controlled access standard.

Persistence Algorithms

Non-persistent CSMA uses random delays to minimize collisions.
If medium is idle, transmit the packet. If busy, wait for a random amount of time from the probability distribution, then retry.
1-persistent CSMA transmits immediately if the medium is idle. Otherwise, it waits until idle and transmits immediately.
P-persistent CSMA is a compromise between non-persistent and 1-persistent. The decision to transmit or wait a period is probabilistic.

Non-persistent CSMA

Rules for non-persistent CSMA include transmitting if medium is idle and waiting a random amount of time if medium is busy, then retrying.
Random delays in this protocol reduce the probability of collisions.
Some capacity is wasted because the medium may remain idle after a transmission ends.
Non-persistent stations are deferential, giving preference to others.

1-persistent CSMA

1-persistent CSMA avoids idle channel time, transmitting immediately if the medium is idle.
Wait until the medium is idle if busy, then transmit immediately.
This protocol is considered "selfish" because it transmits at every opportunity..
Multiple stations waiting to transmit may cause collision.

P-persistent CSMA

This algorithm is a balance between collisions and idle time.
If idle, transmit with a certain probability (p).
Wait for a time unit, otherwise.
If busy, listen until idle, and repeat step 1
Managing the probability 'p' effectively is crucial to minimizing collisions.

Which Persistence Algorithm?

IEEE 802.3 (Ethernet) uses the 1-persistent algorithm.
Both non-persistent and p-persistent CSMA have their performance problems.
1-persistent is unstable due to high collision rate because stations are greedy..
P-persistent is better as wasted time due to collisions is shorter, and stations are less likely to collide on the next attempt given random backoff.

Categories of Standard Ethernet

10Base5 (thick Ethernet), a bus topology, with thick coaxial cable & external transceiver.
10Base2 (thin Ethernet), a bus topology, with thinner, flexible coaxial cable.
10Base-T (twisted-pair Ethernet), a star topology, uses twisted-pair cable.
10Base-F (fiber Ethernet), a star topology, uses fiber optic cable.

10 Base 5: Thick Ethernet

Used a thick coaxial cable that formed a bus topology.
Required an external transceiver which connected via a tap to the cable.
A maximum length of 500 meters and ran at 10 Mbps.

10 Base 2: Thin Ethernet

Cheapernet- is a more flexible thin coaxial cable.
It also used a bus topology.
A maximum length of 185 meters and 10 Mbps, but is lower in cost compared to 10Base5.

10Base-T and 10Base-F

10Base-T uses twisted-pair cabling,
10Base-F uses Fiber optic cabling,
Both use a star topology, with a central hub or switch.

Fast Ethernet

IEEE defined Fast Ethernet under the name 802.3ae.
This is a higher speed protocol (100Mbps).
Various implementations exist (100Base-TX - category 5 UTP cable, 100Base-FX - Fiber).

Fiber Distributed Data Interface -FDDI (802.6)

A token-ring-like network standard using optical fiber.
It runs at a 100Mbps data rate.
Implemented as a dual ring.
The primary ring carries data; the secondary acts as a backup in case the primary fails.

Fibre Channel Applications

Used for linking high-performance workstations, connecting mainframes, linking LANs and WANs to the backbone, and clustering disk farms.

Advantages and disadvantages of FDDI

Advantages: high bandwidth (250Gbps), supports a large number of terminals (up to 1000 for 200km). high resistance to EMI.
Disadvantages: costly, requires significant expertise for installation and maintenance.

LAN Wiring and Physical Topology

This subject matter covers physical wiring configurations for local area networks (LANs).

Network Interface Card

Internal NICs plug into the computer's motherboard expansion slot..
PCI (Peripheral Component Interconnect) is one type of motherboard slot used for internal NICs.

Network Interface Hardware

NICs are special purpose hardware which receive and send data over a network.
Most NICs use DMA to process data without CPU intervention.

NIC support all three kinds of connections

Review Questions

Questions about tokens, CSMA, CSMA/CD, Ethernet frames, different CSMA/CD protocols, binary exponential backoff, token ring networks, and Shannon's theorem.

Reference

Lists the textbooks used for the study materials.

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Description

Test your knowledge on Ethernet networks and LAN protocols with this quiz. Explore critical concepts such as CSMA protocols, Ethernet standards, and the structure of FDDI. Perfect for students and professionals looking to reinforce their understanding of networking technology.