Data Transmission on LAN Chapter
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Questions and Answers

What role does a buffer play in data transmission?

A buffer temporarily stores incoming data until it can be processed by the receiving device.

What is the purpose of flow control in data communication?

Flow control restricts the amount of data sent before acknowledgment is received from the receiving device.

Differentiate between a single-bit error and a burst error.

A single-bit error occurs when only one bit changes, while a burst error involves two or more bits being altered.

What happens if a receiver's buffer fills up during data transmission?

<p>The receiver must inform the sender to halt transmission until there is available space in the buffer.</p> Signup and view all the answers

Name two methods used for flow control in data transmission.

<p>The two methods are Stop-and-Wait and Sliding Window.</p> Signup and view all the answers

Why is it important to acknowledge received frames?

<p>Acknowledgment confirms successful receipt of frames and helps manage further transmission accordingly.</p> Signup and view all the answers

What are some common methods of error detection mentioned?

<p>Common methods include Parity checking, Block coding, CRC, and Checksum.</p> Signup and view all the answers

What is the impact of round-trip delay time and bandwidth delay on data transmission?

<p>Round-trip delay time affects how quickly acknowledgments are received, while bandwidth delay refers to the time taken for data to travel across the medium.</p> Signup and view all the answers

What is the significance of the position and value of each bit in bit-oriented protocols?

<p>In bit-oriented protocols, the position and value of each bit determine its function and meaning, allowing a single character to represent multiple meanings.</p> Signup and view all the answers

How do frames facilitate data transmission across a network?

<p>Frames package the data into headers, bodies, and tails, allowing for organized transportation of data between stations until it reaches the destination.</p> Signup and view all the answers

What actions does a station take upon receiving a frame?

<p>A station temporarily stores the frame in a buffer, checks it for errors, and acknowledges its receipt or requests a resend if errors are detected.</p> Signup and view all the answers

What happens when a station's buffer space runs out?

<p>When buffer space runs out, the station signals to other stations that it cannot accept any more frames.</p> Signup and view all the answers

Give examples of protocols that utilize bit-oriented methods.

<p>Examples of bit-oriented protocols include X.25, HDLC, and SDLC.</p> Signup and view all the answers

What are the key components of a frame?

<p>The key components of a frame are the header (routing and control information), body (actual data), and tail (checksum data).</p> Signup and view all the answers

Explain the concept of half duplex and full duplex in communication.

<p>Half duplex allows communication in both directions but not simultaneously, while full duplex enables simultaneous communication in both directions.</p> Signup and view all the answers

Describe the function of the checksum in a frame.

<p>The checksum in a frame is used to verify the integrity of the data by checking for errors during transmission.</p> Signup and view all the answers

What is the purpose of adding redundant bits in block coding?

<p>Redundant bits are added to enable error detection and correction during data transmission.</p> Signup and view all the answers

In 4b/5b coding, what do the variables k and n represent?

<p>In 4b/5b coding, k represents the number of bits in the data word, and n represents the total number of bits in the code word.</p> Signup and view all the answers

Why are some code words unused in block coding schemes like 4b/5b coding?

<p>Some code words are unused to ensure that valid data words can be transmitted without confusion or errors, providing additional space for error detection.</p> Signup and view all the answers

What happens when the receiver gets a codeword that is not valid?

<p>The receiver discards the invalid codeword because it indicates that an error has occurred during transmission.</p> Signup and view all the answers

In the example provided, what was the codeword created for the data word 01 with added redundancy?

<p>The codeword created for the data word 01 was 01011 after adding redundancy.</p> Signup and view all the answers

What determines the ability of an error-detecting code to identify errors?

<p>An error-detecting code can only detect the types of errors for which it is specifically designed.</p> Signup and view all the answers

How does the receiver guess the correct data word upon receiving a corrupted codeword?

<p>The receiver compares the corrupted codeword with valid codewords and determines the most likely correct one by checking the number of different bits.</p> Signup and view all the answers

Why is it important to consider the types of errors that an error-detecting code is designed for?

<p>It's important because knowing the error types helps in selecting the appropriate coding scheme for reliable data transmission.</p> Signup and view all the answers

What is the primary purpose of the Preamble in the Ethernet frame format?

<p>To synchronize the receiving station's clock.</p> Signup and view all the answers

How does the Start Frame Delimiter (SFD) differ from the Preamble?

<p>The SFD indicates the start of the frame and consists of 1 byte of 10101011, differing from the preamble's 7 bytes of 10101010.</p> Signup and view all the answers

What does the Individual/Group (I/G) bit signify in the Destination Address field?

<p>It indicates whether the frame is directed to an individual station (0) or a group multicast (1).</p> Signup and view all the answers

Explain the role of the Universal/Local (U/L) bit in Ethernet addressing.

<p>The U/L bit indicates if the address is globally unique (0) or locally administered (1).</p> Signup and view all the answers

What is the maximum size of the Information Field in an Ethernet frame?

<p>The maximum size is 1500 octets.</p> Signup and view all the answers

What happens if the Information Field size is less than the minimum required size?

<p>A Pad field is used to fill the frame up to the minimum size of 46 octets.</p> Signup and view all the answers

What does the Source Address (SA) signify in an Ethernet frame?

<p>The Source Address indicates the transmitting station of the frame.</p> Signup and view all the answers

In what format are Ethernet addresses typically expressed?

<p>Ethernet addresses are usually expressed in hexadecimal notation.</p> Signup and view all the answers

What does Power over Ethernet (PoE) allow in terms of network products?

<p>PoE allows data and power supply to be transmitted simultaneously over the same Ethernet cable.</p> Signup and view all the answers

What are the two active components involved in a Power over Ethernet setup?

<p>The two active components are the injector and the splitter.</p> Signup and view all the answers

How many wires in an Ethernet cable are used for data transmission according to the PoE standards?

<p>Four wires are used for data transmission.</p> Signup and view all the answers

What are the three types of hubs mentioned in the text?

<p>The three types of hubs are passive, active, and switching hubs.</p> Signup and view all the answers

What is a key limitation of passive hubs regarding signal processing?

<p>Passive hubs do not process the data signal and can only combine signals from network segments.</p> Signup and view all the answers

What are the two PoE standards mentioned, and their respective power capacities?

<p>The two standards are IEEE 802.3af with 15.4 W and IEEE 802.3at with 25.5 W.</p> Signup and view all the answers

Why is the distance limitation important when connecting computers to passive hubs?

<p>The distance must be no more than half the maximum permissible distance due to signal degradation.</p> Signup and view all the answers

What are the primary functions of routers and gateways in network communication?

<p>Routers direct data packets between networks, while gateways act as entry points for different network protocols.</p> Signup and view all the answers

What does CSMA/CD stand for, and what is its main purpose?

<p>CSMA/CD stands for Carrier Sense Multiple Access with Collision Detection, and its main purpose is to manage access to a shared communication medium while detecting collisions between data transmissions.</p> Signup and view all the answers

How does a station determine if it can transmit in a CSMA/CD environment?

<p>A station determines if it can transmit by sensing the presence or absence of a carrier signal on the channel.</p> Signup and view all the answers

What happens when two stations transmit simultaneously in a CSMA/CD network?

<p>When two stations transmit simultaneously, a collision is detected, and both stations back off for a random amount of time before attempting to retransmit.</p> Signup and view all the answers

What is the difference between CSMA/CD and CSMA/CA?

<p>CSMA/CD uses collision detection to manage data transmission, while CSMA/CA uses collision avoidance techniques to prevent collisions before they happen.</p> Signup and view all the answers

In what situations is CSMA/CA preferred over CSMA/CD?

<p>CSMA/CA is preferred in environments like 802.11 based wireless LANs where it is not possible to listen while transmitting.</p> Signup and view all the answers

Explain the significance of the first number in Ethernet standards like 10Base5.

<p>The first number in Ethernet standards, such as 10Base5, indicates the data transmission rate in megabits per second (MBPS).</p> Signup and view all the answers

What are the different Ethernet standards mentioned in the content?

<p>The different Ethernet standards mentioned are 10Base5, 10Base2, 10Base-T, and 10Base-F.</p> Signup and view all the answers

Why is collision avoidance important in CSMA/CA?

<p>Collision avoidance is important in CSMA/CA as it reduces the likelihood of collisions on a busy channel, thereby improving the performance of data transmission.</p> Signup and view all the answers

What function does a primary station serve in a data link communication system?

<p>A primary station controls the data link, initiates error recovery procedures, and manages the flow of data transmissions.</p> Signup and view all the answers

In what scenario would a secondary station send a 'Receiver Not Ready' (RNR) signal?

<p>A secondary station sends an RNR signal when it runs out of buffer space to store incoming frames.</p> Signup and view all the answers

How does a secondary station acknowledge multiple received frames without responding to each frame individually?

<p>The secondary can send a supervisory frame with a sequence number bit set to acknowledge a group of received frames.</p> Signup and view all the answers

What is meant by the 'sliding window value' in a communication system?

<p>The sliding window value indicates the number of unacknowledged frames a secondary station can handle at one time.</p> Signup and view all the answers

What happens when a secondary station receives a supervisory frame after sending an RNR indication?

<p>Upon receiving a supervisory frame indicating that buffer space is cleared, the secondary station can inform the primary it is ready to receive frames again.</p> Signup and view all the answers

Why is it necessary for a primary station to retain its Information frames when a secondary station is not ready?

<p>The primary station retains Information frames to ensure that they can be transmitted again once the secondary station is able to process them.</p> Signup and view all the answers

During data transmission, what type of frames must a secondary station process even when its buffer is full?

<p>A secondary station must still process incoming supervisory and unnumbered frames despite its buffer being full.</p> Signup and view all the answers

How can the sliding window value be modified in a communication setup?

<p>The sliding window value can be negotiated during the initial establishment of the communication call.</p> Signup and view all the answers

What mechanism does CSMA/CA use to signal other stations before transmission?

<p>CSMA/CA sends a signal to inform other stations not to transmit before sending its packet.</p> Signup and view all the answers

How does the channel sensing process in CSMA/CA differ from that in CSMA/CD?

<p>In CSMA/CA, the channel is checked for activity prior to transmission, while CSMA/CD can detect collisions after they occur.</p> Signup and view all the answers

Describe the role of collision avoidance in CSMA/CA networks.

<p>Collision avoidance reduces the likelihood of transmission collisions by requiring stations to defer their transmissions when the channel is busy.</p> Signup and view all the answers

What limitations does CSMA/CA address that CSMA/CD cannot?

<p>CSMA/CA is designed for wireless LANs where collision detection is not feasible due to the inability to listen while sending.</p> Signup and view all the answers

What does the evolution from 10Base5 to 10Base-F signify in Ethernet standards?

<p>The evolution signifies advancements in data transmission rates and the different physical media used in Ethernet technology.</p> Signup and view all the answers

What is the significance of the number in Ethernet standards like '10Base5'?

<p>The number indicates the data rate in megabits per second (MBPS), defining the speed of the Ethernet standard.</p> Signup and view all the answers

What function does the line discipline serve in data transmission protocols?

<p>Line discipline ensures that a device does not transmit until the receiver is ready, preventing unnecessary data transmission and signal interference.</p> Signup and view all the answers

How does the presence of a carrier affect cable communication in CSMA/CD?

<p>When a carrier is sensed, the segment of cable is considered occupied, and stations must wait to transmit.</p> Signup and view all the answers

What happens when two stations attempt to transmit simultaneously in a CSMA/CD network?

<p>A collision is detected, prompting both stations to back off for a random time before retrying transmission.</p> Signup and view all the answers

Why is flow control critical in data link control systems?

<p>Flow control prevents overwhelming the receiver with too much data by regulating the amount of data sent before awaiting acknowledgment.</p> Signup and view all the answers

How do enquiry/acknowledgment and poll/select methods differ in line discipline?

<p>Enquiry/acknowledgment is used in peer-to-peer communication, whereas poll/select is employed in primary-secondary communication.</p> Signup and view all the answers

What are the two main concerns addressed by flow control mechanisms?

<p>The primary concerns are preventing data overflow to the receiver and managing the rate at which data is transmitted.</p> Signup and view all the answers

Identify two characteristics of a character-oriented protocol frame.

<p>Character-oriented protocol frames consist of a sequence of characters and use a fixed-length format for delineation.</p> Signup and view all the answers

What role does the data link layer play in the process of framing?

<p>The data link layer packs bits into frames, making each one distinguishable from another for effective data transmission.</p> Signup and view all the answers

What is the significance of error control in data transmission?

<p>Error control is vital for detecting and correcting errors that occur during data transmission, ensuring data integrity.</p> Signup and view all the answers

How does Power over Ethernet (PoE) enhance network connectivity?

<p>Power over Ethernet allows network cables to carry electrical power along with data, simplifying installation and reducing clutter.</p> Signup and view all the answers

How is the one’s complement representation of 21 in four bits determined from its binary form?

<p>The binary form of 21 is 10101, which requires five bits. In four bits, we wrap the leftmost bit and add it to the remaining bits, resulting in 0110, representing the number 6.</p> Signup and view all the answers

What method is used to find the negative representation of a number in one’s complement arithmetic?

<p>The negative representation is found by inverting all bits of the positive number. For example, the negative of 6 (0110) is 1001.</p> Signup and view all the answers

Describe the process the sender site follows to create a checksum according to one’s complement addition.

<p>The sender divides the message into 16-bit words, sets the checksum to 0, adds all words using one’s complement addition, and then complements the sum to produce the checksum.</p> Signup and view all the answers

How does the receiver determine if there has been an error in the received message?

<p>The receiver sums all the 16-bit words, including the checksum, using one’s complement addition, and checks if the result is 0. If the sum is 0, the message is accepted; otherwise, it's rejected.</p> Signup and view all the answers

What distinguishes character-oriented protocols from bit-oriented protocols in data transmission?

<p>Character-oriented protocols use 8-bit characters and additional flags for frame separation, while bit-oriented protocols do not use fixed-size character frames.</p> Signup and view all the answers

Explain the importance of using complementary checksums in data communication.

<p>Using complementary checksums helps detect errors in data transmission by verifying the sum of transmitted words. If the summed result is not zero, it indicates an error occurred.</p> Signup and view all the answers

What are the primary steps for creating a checksum on the receiver side?

<p>The receiver divides the message into 16-bit words, adds them using one’s complement addition, and then complements the sum to generate a new checksum.</p> Signup and view all the answers

What are the implications of using a multicast broadcast for a specific group in Ethernet frames?

<p>Multicast broadcasts require unique addresses assigned by the Network Administrator, ensuring targeted delivery to the specific group rather than to all stations.</p> Signup and view all the answers

How is the leftmost bit handled when representing numbers in one’s complement with a limited number of bits?

<p>The leftmost bit is wrapped around and added to the remaining bits to ensure the result fits within the specified number of bits.</p> Signup and view all the answers

How does the Source Address (SA) field's I/G bit setting differ from that of the Destination Address (DA)?

<p>The SA field always has the I/G bit set to 0, indicating it is an Individual address, while the DA can be set to either Individual (0) or Group (1).</p> Signup and view all the answers

What comprises the entire format of an Ethernet frame, and what is its purpose?

<p>An Ethernet frame is composed of the Preamble, SFD, DA, SA, Length, and the Information Field, serving to encapsulate data for reliable communication across the network.</p> Signup and view all the answers

Explain the significance of the Length field in Ethernet frames and its impact on data transmission.

<p>The Length field indicates the size of the Information Field, allowing variable length frames and ensuring that the receiving station can correctly process the incoming data.</p> Signup and view all the answers

Discuss the roles of the Universal/Local (U/L) bit within the context of Ethernet addressing.

<p>The U/L bit determines whether the address is universally administered (using a manufacturer's unique address) or locally administered by the Network Administrator.</p> Signup and view all the answers

Identify the differences in the structure of DA and SA fields in Ethernet frames.

<p>Both DA and SA are 6 octets long and formatted similarly, but the DA can have its I/G bit set for group addresses while the SA's I/G bit is always 0.</p> Signup and view all the answers

What are the operational implications if the Information Field size is less than the minimum octet requirement?

<p>If the Information Field is below 46 octets, a Pad field is added to meet the minimum requirement, ensuring that the Ethernet frame maintains its integrity.</p> Signup and view all the answers

How does the Preamble aid in the synchronization of the receiving station’s clock?

<p>The Preamble consists of a specific bit pattern that allows the receiving station to establish synchronization before the actual data begins.</p> Signup and view all the answers

What is the primary difference between UTP and STP cables?

<p>UTP (Unshielded Twisted Pair) is generally used indoors, while STP (Shielded Twisted Pair) is designed for outdoor use and special environments.</p> Signup and view all the answers

Describe the significance of the IEEE 802.3z standard.

<p>IEEE 802.3z, or 1000BaseT, is significant because it introduced Gigabit Ethernet, allowing high-speed connections up to 1 Gbit/s over Cat5e cabling.</p> Signup and view all the answers

What was the main transmission technology employed by 10Broad36, and why is it rarely used?

<p>10Broad36 combined analog and digital signals but is rarely used due to its outdated technology and the availability of better alternatives.</p> Signup and view all the answers

Explain the role of auto-negotiation in Gigabit Ethernet.

<p>Auto-negotiation allows devices to automatically determine the maximum supported speed (10, 100, or 1000 Mbit/s) between connected devices.</p> Signup and view all the answers

Why were 10Base5 and 10Base2 phased out in favor of newer Ethernet standards?

<p>Both 10Base5 (Thick Coax) and 10Base2 (Thin Coax) were phased out due to limitations in speed, size, and flexibility compared to standards like 10BaseT.</p> Signup and view all the answers

Identify and explain the importance of the Category ratings in UTP cable.

<p>Category ratings in UTP cable indicate the cable's performance specifications, such as bandwidth and maximum data transmission rate, which impact network quality.</p> Signup and view all the answers

What distinguishes the PAM-5 amplitude modulation scheme used in Gigabit Ethernet?

<p>PAM-5 utilizes five different amplitude levels to encode data, allowing higher data rates over the same network medium.</p> Signup and view all the answers

Discuss the transition from 10Base2 to 10BaseT in networking practices.

<p>The transition from 10Base2 to 10BaseT was driven by the latter's use of twisted pair cabling, which allowed for easier installation and better performance.</p> Signup and view all the answers

Flashcards

Flow Control

Procedures to regulate data transmission rate from sender to receiver

Buffer

Memory block for storing incoming data until processed

Stop-and-Wait

Flow control method where sender waits for acknowledgment before sending next frame

Sliding Window

Flow control method allowing sending multiple frames before acknowledgment

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Error Detection

Identifying corrupted data during transmission

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Single-bit error

Data corruption affecting only one bit

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Burst error

Data corruption affecting multiple bits

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Redundant bits

Extra bits added to data for error detection/correction

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Block Coding

Dividing a message into blocks of bits (data words) and adding redundant bits to each block to form code words, increasing the block's length from k bits to n bits (k+r).

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Data Word

A block of bits representing the actual message information, before adding redundant bits.

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Code Word

The resulting block of bits after adding redundant bits to the data word; used for message transmission.

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4b/5b Coding

A specific block coding example where k=4 bits form the data word and n=5 bits form the code word. Uses 16 data words and 32 possible codewords.

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Error Detection

A method to check if data was corrupted during transmission.

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Error Correction

A method for finding the error bit and correcting the received bit.

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Redundant Bits

Extra bits added to the data word to improve reliability during transmission, by making certain errors detectable and correctable.

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Valid Codeword

A received codeword that matches one of the valid combinations of codewords generated for the given data.

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Bit-oriented protocols

Protocols where each bit in a data stream has a specific function, determined by position and value.

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Character-based protocol

Protocols where characters (sequences of bits) are used to convey meaning.

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Frame

An envelope for data transmission, containing header, body, and tail for routing, data, and checksum.

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Data Transmission (Intermediate Stations)

Process of sending data through multiple stations by repackaging the data into frames at each station.

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Full Duplex

Two-way communication where both sender and receiver can transmit data simultaneously

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Half Duplex

Two-way communication where only one party can transmit data at a time.

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Error Checking

Receiving stations verify data for errors and request re-transmission if errors are detected.

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Buffer Space

Limited storage space on a receiving station used to hold incoming frames.

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Preamble

7 bytes of 10101010 used to synchronize the receiver's clock.

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Start Frame Delimiter (SFD)

1 byte (10101011) signaling the start of a frame.

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Destination Address (DA)

6 octets indicating the receiver of the frame.

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Individual/Group (I/G) bit

Indicates whether the destination is for a single device or multiple.

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Universal/Local (U/L) bit

Specifies if device addresses are unique, administrator-assigned or burnt-in ROM.

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Source Address (SA)

Same format as DA, but always indicates the sender.

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Length field

Indicates the size of data (information field).

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Information Field

Actual data being transmitted, variable length (46-1500 octets).

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CSMA/CD

Carrier Sense Multiple Access with Collision Detection. A method for accessing a shared network cable. Stations listen before transmitting and if a collision occurs, they back off and try again.

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Carrier Sense

Checking for ongoing communication on a shared network cable before transmitting.

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Multiple Access

Multiple devices share a single network cable or channel.

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Collision Detection

Identifying when two devices try to transmit on the shared cable simultaneously.

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CSMA/CA

Carrier Sense Multiple Access with Collision Avoidance. A method for accessing a shared network (e.g., wireless). It attempts to avoid collisions.

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Ethernet

A popular LAN technology standard supporting different implementations for data transmission.

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10Base5/2

Ethernet standards with different physical layer implementations and data rates, 10 megabits per second, 5/2 refers to cable types.

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Wireless LAN

A local area network using radio waves to connect devices.

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Power over Ethernet (PoE)

A technology that transmits both data and power through a single Ethernet cable

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IEEE 802.3af/at

Standards for Power over Ethernet, defining power levels (15.4W and 25.5W)

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PoE Injector/Splitter

The devices that inject or distribute PoE power to network products.

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Passive Hub

A hub that doesn't amplify or process signals, only combines them.

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Active Hub

A hub that amplifies and cleans up signals to maintain quality.

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Switching Hub

A type of hub that directs data only to the receiving device.

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Connecting Device

Network devices like hubs, switches, and routers, each operating at a different layer in networks.

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Ethernet Cable Wires

Ethernet cables typically have 8 wires; 4 for data transmission, 4 for powering specific devices.

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Data Link Control

The layer responsible for reliable transmission of data frames over a physical link, encompassing framing, line discipline, flow control, and error control.

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Line Discipline

Set of rules governing who transmits when to prevent signal collisions and ensure communication etiquette on a network.

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Flow Control

Methods to manage the rate of data transmission to prevent overwhelming the receiver.

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Framing (Data Link Layer)

Organizing data into discrete units (frames) with headers and trailers for identification and error detection, by bit- or character-oriented protocols.

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Ethernet Categories

Standards specifying various physical implementation for Ethernet, such as 10Base5/2 or Gigabit Ethernet, defined for different speeds and cable types.

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Ethernet Wiring

Set of standards that detail the connection methods and cable arrangements for implementing Ethernet.

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Power over Ethernet (PoE)

A technology enabling the transmission of both data and power over a single Ethernet cable.

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Connecting Devices (LAN)

Network devices like hubs, switches, and routers that facilitate communication between devices on a local area network.

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Checksum Error Detection

A method used to detect errors in data transmission by adding a checksum value to the data and checking for errors at the receiver end.

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One's Complement Arithmetic

A method of representing signed numbers using bit inversions for negative values.

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Checksum

A short piece of data designed to detect errors in a message or block of data, calculated by the sender and verified by the receiver.

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Stop-and-Wait Protocol

A simple flow control protocol where the sender sends one frame and waits for an acknowledgment before sending the next.

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LAN Protocols

Rules and standards used for data transmission within a Local Area Network.

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Character-Oriented Protocol

A data transmission protocol that structures data in sequences of 8-bit characters, with flags or delimiters between frames.

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Bit-Oriented Protocol

A data transmission protocol where individual bits are transmitted and used to structure data and signal, used to prevent confusion in data framing.

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Frame

A structured block of data transmitted over a network, containing header and trailer for data information and control.

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Primary Station

The station that controls the data link, initiates error recovery, and manages data transmission.

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Secondary Station

The station that responds to commands from the primary station and might initiate transmissions on its own, like when its buffer is full.

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Sliding Window

The number of data frames a secondary station can receive unacknowledged; typically 2.

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Frame

An envelope for transmitting data, containing control information and the actual data.

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Buffer Space

Temporary storage on a secondary station for incoming frames before they're processed.

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RNR (Receiver Not Ready)

A signal a secondary station sends to a primary station to indicate its buffer is full.

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RR (Receiver Ready)

A signal from the secondary station to the primary station to indicate it is ready to accept more frames.

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Supervisory Frame

A frame used by the secondary station to acknowledge a group of received frames.

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Preamble

7 bytes of 10101010 used to synchronize the receiver's clock.

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SFD

1 byte (10101011) signaling the start of a frame.

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Destination Address (DA)

6 octets identifying the receiver of the frame.

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I/G bit

Indicates whether destination is individual or group.

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U/L bit

Specifies whether address is local or universal/administrator assigned.

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Length field

Indicates size of the data within the frame (variable: 46-1500 octets).

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Source Address (SA)

6 octets indicating the sender of the frame.

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Information Field

Actual data being transmitted (46-1500 octets).

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CSMA/CD

Carrier Sense Multiple Access with Collision Detection. A method for sharing a network cable. Stations listen, and if a collision occurs, stations back off and try again.

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Carrier Sense

Checking the network for ongoing communication before sending your data.

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Multiple Access

Many devices sharing the same network cable.

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Collision Detection

Recognizing when two devices try to send data at once on the shared cable.

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CSMA/CA

Carrier Sense Multiple Access with Collision Avoidance. A method for accessing a shared network to avoid collisions, primarily used in wireless networks.

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Ethernet

A common LAN technology standard, supporting different implementations for data transmission.

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10Base5/2

Ethernet standards with specific cable and data rate specs (10Mbps).

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Wireless LAN

A local area network using radio waves for communication.

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Television Channel Broadcasting

A single television channel is transmitted from a television station's transmitter.

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Broadband Transmission

Broadband transmits multiple streams of data or intelligence over a single medium, like a cable system.

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10Base5 Ethernet

The original Ethernet configuration using Thick Coaxial cable, rarely used now.

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10Base2 Ethernet

Thin Coaxial cable Ethernet, commonly used in the 1990s.

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10BaseT Ethernet

Commonly used to connect workstations to network hubs.

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100BaseT Ethernet

High-speed Ethernet using Cat5 cabling (Twisted Pair), a popular standard.

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Gigabit Ethernet (1000BaseT)

High-speed Ethernet connecting servers to high-speed backbone networks using Cat5e cabling.

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UTP (Unshielded Twisted Pair)

Predominantly used indoor Ethernet cabling.

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Study Notes

Data Transmission on LAN

  • This chapter discusses functions related to data transmission on Local Area Networks (LANs).
  • Topics covered include: Data Link Control (framing, line discipline, flow control, error control), Media Access Control, and connecting devices (e.g., hubs, switches).
  • Framing: The data link layer packages bits into frames for identification.
  • Character-oriented protocols frame data as shown in Fig 3.1(a) which uses a flag, header, data from upper layer, variable number of characters and trailer, and flag.
  • Bit-oriented protocols frame data as shown in Fig 3.1(b) which uses a flag, header, data from upper layer, variable number of bits, and trailer, and flag.
  • Line Discipline: Prevents devices from transmitting until the receiver is ready to accept; avoids transmission conflicts. Line discipline establishes link establishment and transmission rights. This is accomplished through enquiry/acknowledgment and polling/selection methods.
  • Flow Control: Manages the flow of data to prevent overwhelming the receiver. Receivers have limited processing speeds and memory capacity. The receiver signals the sender to halt transmission if limits are exceeded. Acknowledgment messages are also used for frame-by-frame or multiple frame confirmation.
  • Error Control: Detects and corrects errors in data transmission. Single-bit errors change a single bit, and burst errors affect multiple bits. Methods for error detection and correction include parity checking, block coding, CRC, and checksums.

Flow Control

  • Flow Control manages the amount of data a sender transmits before waiting for acknowledgment from the receiver.
  • There are several issues that must be taken into account: prevent overwhelming the receiver, and the receiver having sufficient memory capacity,
  • Stop-and-Wait and Sliding Window are used as methods to control the flow of data.

Error Detection and Correction

  • Errors in data transmission result from various causes.
  • Single-bit errors occur when precisely one bit in a data unit changes. Burst errors occur when two or more bits in a data unit change. Burst errors are more frequent.
  • Some protocols require checking for corrupted data and correcting it.

Block Coding

  • Block coding involves dividing the message into blocks of k bits called data words to enhance reliability by adding redundant bits to make n bits equal to k bit + r bits
  • 4b/5b coding is an illustration of block coding (k = 4, n = 5).

Cyclic Redundancy Check (CRC)

  • CRC is a popular error detection technique that uses generator polynomials (refer Table 3.3)
  • It adds redundancy to data to help identify errors during transmission.
  • Remainders are used to identify and correct errors.

Checksum

  • A form of error detection that involves calculating the sum of data words and then sending the complement of that sum (as illustrated in Fig 3.8).
  • The receiver calculates the sum of received data and the checksum to detect errors.

Ethernet Protocols

  • Character-oriented Protocols: Use 8-bit character codes such as ASCII, incorporating header and trailer elements for frame demarcation.
  • Bit-oriented Protocols: Each bit has significance; increase meaning efficiency. This includes X.25, HDLC and SDLC.

LAN Protocols

  • Classification of multiple-access protocols (Fig 3.9). Types include random access (e.g., ALOHA, CSMA/CD, CSMA/CA) and controlled access (e.g., reservation, polling, token passing).
  • MAC Address: Unique hardware address used for devices on a LAN.
  • Ethernet frame format: Includes preamble, SFD, destination address (DA), source address (SA), length/type field, data field, and frame check sequence (FCS).

Media Access Control (MAC)

  • IEEE 802.3 defines Ethernet standards (Fig 3.10 and other diagrams).
  • Typical Ethernet implementations include 10Base5, 10Base2, 10Base-T, and 10Base-F.

Cables for Ethernet

  • UTP (Unshielded Twisted Pair) and STP (Shielded Twisted Pair) cables are used.
  • They are categorized (e.g., CAT3, CAT5).

Power over Ethernet (PoE)

  • Technology to transmit power and data on the same Ethernet cable reducing the number of wires needed.

Connecting Devices

  • Hubs: Central connection points for network cables (passive, active, intelligent)
  • Switches: Improve network performance by directing data to specific devices (Layer 2, Layer 3).
  • A switch also uses STP to avoid network loops.

Virtual LANs (VLANs)

  • Group of devices on a network that communicate as if they were on the same physical LAN.
  • VLANs use VLAN tags to categorize data, improve security and efficiency for deployments on a LAN.

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Related Documents

Data Transmission on LAN PDF

Description

Explore the fundamentals of data transmission on Local Area Networks (LANs) in this chapter. Topics include Data Link Control, Media Access Control, and the functionality of connected devices like hubs and switches, ensuring efficient data communication.

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