Data link control involves framing data, flow and error control, and common protocols like HDLC and PPP. Framing involves adding source/destination addresses to frames for transmission. Flow control restricts how much data the sender sends before waiting for acknowledgment. Error control uses techniques like automatic repeat request to retransmit lost data frames. HDLC and PPP are protocols that define frame formats and control procedures for point-to-point links.
Elementary data link protocols are designed to perform framing, error control, and flow control. Framing divides bitstreams into frames of a few hundred to a few thousand bytes. The unrestricted simplex protocol allows one-way transmission with infinite buffers and no faults or lost frames. Stop-and-wait protocols provide one-way transmission and flow control for error-free channels, acknowledging each frame before sending the next. Noisy channel protocols use techniques like error detection and retransmission to minimize errors over noisy channels.
This document summarizes key concepts about congestion control in TCP including:
- TCP uses additive increase multiplicative decrease (AIMD) to dynamically adjust the congestion window size and maintain efficiency and fairness.
- TCP has slow start and congestion avoidance states that govern how the congestion window is adjusted in response to acknowledgements.
- TCP responds to packet loss through fast retransmit, fast recovery, and halving the congestion window size to reduce congestion according to protocols like Tahoe, Reno, and New Reno.
This document discusses various data link layer protocols. It begins by describing the services provided by the data link layer, including framing, error control, and flow control. It then discusses different types of framing such as fixed-size and variable-size. The document also covers different protocols for handling flow control and error control, including stop-and-wait, go-back-N ARQ, and selective repeat ARQ. It analyzes the performance of these protocols on both noiseless and noisy channels.
This document summarizes circuit switching and packet switching techniques in communications networks. It discusses how circuit switching establishes a dedicated physical path between communicating nodes but is inefficient for bursty traffic. Packet switching breaks messages into packets that are transmitted over shared links, improving efficiency. Key aspects covered include virtual circuits, datagrams, packet switching advantages, X.25 standards, and how Frame Relay improved on X.25 by reducing overhead.
The document discusses different protocols used in the data link layer for reliable transmission of data over noisy channels. It describes the simplest protocol with no error control, as well as stop-and-wait, go-back-N, and selective repeat ARQ protocols. Stop-and-wait protocol ensures only one frame is transmitted at a time using acknowledgments. Go-back-N allows transmitting multiple frames before waiting for ACKs but retransmits all subsequent frames if one is lost. Selective repeat ARQ allows out-of-order frame delivery to avoid unnecessary retransmissions. Sliding windows and sequence numbers are used for flow control and ensuring frames are received in the correct order.
Data link control involves framing data, flow and error control, and common protocols like HDLC and PPP. Framing involves adding source/destination addresses to frames for transmission. Flow control restricts how much data the sender sends before waiting for acknowledgment. Error control uses techniques like automatic repeat request to retransmit lost data frames. HDLC and PPP are protocols that define frame formats and control procedures for point-to-point links.
Elementary data link protocols are designed to perform framing, error control, and flow control. Framing divides bitstreams into frames of a few hundred to a few thousand bytes. The unrestricted simplex protocol allows one-way transmission with infinite buffers and no faults or lost frames. Stop-and-wait protocols provide one-way transmission and flow control for error-free channels, acknowledging each frame before sending the next. Noisy channel protocols use techniques like error detection and retransmission to minimize errors over noisy channels.
This document summarizes key concepts about congestion control in TCP including:
- TCP uses additive increase multiplicative decrease (AIMD) to dynamically adjust the congestion window size and maintain efficiency and fairness.
- TCP has slow start and congestion avoidance states that govern how the congestion window is adjusted in response to acknowledgements.
- TCP responds to packet loss through fast retransmit, fast recovery, and halving the congestion window size to reduce congestion according to protocols like Tahoe, Reno, and New Reno.
This document discusses various data link layer protocols. It begins by describing the services provided by the data link layer, including framing, error control, and flow control. It then discusses different types of framing such as fixed-size and variable-size. The document also covers different protocols for handling flow control and error control, including stop-and-wait, go-back-N ARQ, and selective repeat ARQ. It analyzes the performance of these protocols on both noiseless and noisy channels.
This document summarizes circuit switching and packet switching techniques in communications networks. It discusses how circuit switching establishes a dedicated physical path between communicating nodes but is inefficient for bursty traffic. Packet switching breaks messages into packets that are transmitted over shared links, improving efficiency. Key aspects covered include virtual circuits, datagrams, packet switching advantages, X.25 standards, and how Frame Relay improved on X.25 by reducing overhead.
The document discusses different protocols used in the data link layer for reliable transmission of data over noisy channels. It describes the simplest protocol with no error control, as well as stop-and-wait, go-back-N, and selective repeat ARQ protocols. Stop-and-wait protocol ensures only one frame is transmitted at a time using acknowledgments. Go-back-N allows transmitting multiple frames before waiting for ACKs but retransmits all subsequent frames if one is lost. Selective repeat ARQ allows out-of-order frame delivery to avoid unnecessary retransmissions. Sliding windows and sequence numbers are used for flow control and ensuring frames are received in the correct order.
This document summarizes key topics related to data link control and protocols. It discusses framing methods like fixed-size and variable-size framing. It also covers flow control, error control, and protocols for both noiseless and noisy channels. Specific protocols described include the Simplest Protocol, Stop-and-Wait Protocol, Stop-and-Wait ARQ, Go-Back-N ARQ, and Selective Repeat ARQ. The document provides details on their design, algorithms, and flow diagrams to illustrate how each protocol handles framing, flow control, and error control.
Transmission control protocol ...............................SwatiHans10
The document discusses the Transmission Control Protocol (TCP) which operates at the transport layer of the OSI model. TCP provides reliable, connection-oriented data transmission through the use of sequence numbers, acknowledgments, and retransmissions to ensure packets are delivered correctly. It establishes connections using a 3-way handshake and closes connections through a 4-way handshake. TCP uses port numbers to identify applications at each end of the connection and implements flow and congestion control to regulate data transfer rates.
Transport protocols establish reliable communication between machines on a network. They provide services like error control, flow control, and multiplexing. The main transport protocols are TCP and UDP. TCP is connection-oriented and provides reliable, ordered delivery. UDP is connectionless and faster but unreliable. Both protocols use port numbers to identify sending and receiving processes and segment packet headers with fields like source/destination port and sequence numbers. DNS is an application layer protocol that maps domain names to IP addresses, enabling human-friendly web addresses. It uses a hierarchical system of root, TLD, and authoritative name servers to resolve names.
The document discusses the Transport Control Protocol (TCP) which provides reliable, ordered and error-checked delivery of data streams between applications running on hosts communicating via an IP network. It describes TCP's key functions including segmentation, error control using acknowledgements and retransmissions, flow control using sliding windows, and multiplexing/demultiplexing of data streams. The key aspects of TCP frames such as sequence numbers, acknowledgement numbers, windows and checksums are also summarized.
The document discusses data link control and framing in computer networks. It describes two main functions of the data link layer: defining frames and performing error detection on frames. It also discusses different types of framing such as fixed-size framing and variable-size framing using character-oriented and bit-oriented protocols. Specific protocols discussed include Stop-and-Wait ARQ which uses positive acknowledgments and retransmissions, and Go-Back-N ARQ which allows for pipelining of multiple frames before requiring an acknowledgment.
This document discusses TCP over wireless networks. It explains that TCP was designed for fixed networks with low delay and errors, but wireless networks have high delay, errors and variable bandwidth. This causes TCP to perform poorly over wireless. The document outlines various techniques to improve TCP performance over wireless like Fast Retransmit and Recovery, Slow Start proposals with larger initial windows, ACK counting and ACK-every-segment. It also discusses protocols like HTTP, RLP that operate between TCP and the wireless transmission layers.
This document provides information about MobileComm Technologies' drive test process for UMTS networks. It includes documentation on tools used for tuning and optimization, parameters measured, call flows, key performance indicators, examples of coverage and interference issues identified, and tips for network tuning. The document contains 47 slides covering topics like coverage verification using P-CPICH measurements, identifying interference and overshooting issues, analyzing call drops, tuning for voice and data calls, and comparing mechanical vs electrical antenna tilts.
This document describes the data acquisition process and network topology for a Sercel 428XL seismic data acquisition system. It discusses how seismic data is acquired by field units, digitized, transmitted through a network of LAU nodes, and finally received and processed by the recording truck. Key components include the field digitizer units, LAU nodes, LCI recorder, and 428XL server. The data passes through various processing stages including analog to digital conversion, multiplexing, filtering, compression and error checking before being received and analyzed by the control node.
The document provides information about various data link layer concepts including:
1. The data link layer provides framing, flow control, and error control between network layers on different machines. It uses devices like switches and bridges.
2. Error detection methods include parity checks, checksums, and CRC to detect errors in transmitted frames.
3. Data link protocols for flow control include stop-and-wait, sliding window protocols, and ARQ methods like go-back-N and selective repeat.
4. Framing encapsulates data with headers and trailers using fixed or variable size frames. Methods like byte stuffing and bit stuffing handle special characters in the data.
TCP provides reliable data transfer through several key features:
- It numbers data bytes and uses acknowledgments to ensure all bytes are received correctly. If bytes are lost, they are retransmitted.
- Congestion control algorithms like slow start and congestion avoidance allow TCP to gradually increase data transfer rates while avoiding overwhelming the network.
- Fast retransmit detects lost packets sooner by retransmitting on three duplicate ACKs, while fast recovery resumes data transfer using ACKs still in the pipe.
This document provides an overview of transport layer protocols TCP, UDP, and SCTP. It discusses the history and evolution of TCP, including key developments like congestion control algorithms. UDP is described as a connectionless and unreliable protocol. SCTP is introduced as a protocol developed to transport telephony signaling over IP networks. It addresses limitations of TCP like head-of-line blocking and provides features like multi-homing and message orientation. The document defines SCTP terminology and describes its chunks, states, congestion control approach, and similarities to TCP. In summary, it serves as a high-level introduction to transport protocols with a focus on motivations and capabilities of SCTP.
Multiplexing and demultiplexing techniques allow the simultaneous transmission of multiple signals across a single data link. When the bandwidth of a medium is greater than the needs of connected devices, multiplexing can be used to share the link and improve transmission efficiency. At the transmitter, multiplexing involves framing data, adding overhead information, and rate matching. At the receiver, demultiplexing requires data retiming, frame recovery, and parsing. Synchronization is important and is achieved through carrier recovery, clock recovery, and frame recovery. Multiplexing hierarchies like T1 and E1 are commonly used standards.
Here is a strategy the prisoners could employ:
1. On the first day, the prisoner who visits the switch room toggles one of the switches to the ON position.
2. On subsequent days, the prisoner toggles the other switch if it is in the OFF position, or says "all prisoners have visited" if both switches are in the ON position.
3. This strategy guarantees that after 31 days, both switches will be in the ON position, allowing the prisoner to correctly say "all prisoners have visited" and ensure all prisoners are set free.
The transport layer provides process-to-process communication and utilizes three main protocols: UDP, TCP, and SCTP. UDP is a connectionless protocol that does not guarantee delivery, while TCP provides reliable, ordered delivery through a connection-oriented approach. SCTP also provides reliable delivery with the added capability of multiple streams. Key aspects of these protocols include port numbers, packet/segment formatting, and connection establishment handshaking.
This document provides an agenda and overview of topics related to the transport layer and networking essentials. The agenda includes discussions of the transport layer, UDP overview, TCP communication process, the socket API, and tools and utilities. Specific topics that will be covered include the role and functions of the transport layer, UDP features and headers, TCP reliability mechanisms like connection establishment and termination, sequence numbers and acknowledgments, window sliding, and data loss/retransmission. The document also provides brief overviews and usage examples for common networking tools like ifconfig, nmcli, route, ping, traceroute, netstat, dig, ncat, nmap, tcpdump, and wireshark.
The document discusses data link control protocols and HDLC. It introduces the need for data link protocols to manage frame exchange over a link, including flow control, error control, and addressing. It describes various flow and error control mechanisms like stop-and-wait, sliding windows, go-back-N, and selective reject ARQ. It also provides details on the HDLC frame structure and operation, including address fields, control fields, information fields, and the exchange of different frame types during initialization, data transfer, and disconnection.
Data link protocols provide control over data exchange at the data link layer through mechanisms like frame synchronization, flow control using stop-and-wait or sliding windows, and error control using automatic repeat request (ARQ) protocols like stop-and-wait, go-back-N, and selective-reject to handle lost or damaged frames. HDLC is a commonly used data link protocol that uses synchronous transmission of frames with flag fields, address fields, control fields, information fields, and frame check sequences along with three phases of operation and different frame types.
This document summarizes multiple access protocols used in computer networks at the data link layer. It discusses random access protocols like CSMA/CD and CSMA/CA that allow nodes to transmit randomly. It also covers controlled access protocols like reservation, polling, and token passing that require nodes to get permission before transmitting. Finally, it describes channelization techniques for sharing bandwidth, including FDMA, TDMA, and CDMA that divide the channel by frequency, time, or code respectively.
This document summarizes key topics related to data link control and protocols. It discusses framing methods like fixed-size and variable-size framing. It also covers flow control, error control, and protocols for both noiseless and noisy channels. Specific protocols described include the Simplest Protocol, Stop-and-Wait Protocol, Stop-and-Wait ARQ, Go-Back-N ARQ, and Selective Repeat ARQ. The document provides details on their design, algorithms, and flow diagrams to illustrate how each protocol handles framing, flow control, and error control.
Transmission control protocol ...............................SwatiHans10
The document discusses the Transmission Control Protocol (TCP) which operates at the transport layer of the OSI model. TCP provides reliable, connection-oriented data transmission through the use of sequence numbers, acknowledgments, and retransmissions to ensure packets are delivered correctly. It establishes connections using a 3-way handshake and closes connections through a 4-way handshake. TCP uses port numbers to identify applications at each end of the connection and implements flow and congestion control to regulate data transfer rates.
Transport protocols establish reliable communication between machines on a network. They provide services like error control, flow control, and multiplexing. The main transport protocols are TCP and UDP. TCP is connection-oriented and provides reliable, ordered delivery. UDP is connectionless and faster but unreliable. Both protocols use port numbers to identify sending and receiving processes and segment packet headers with fields like source/destination port and sequence numbers. DNS is an application layer protocol that maps domain names to IP addresses, enabling human-friendly web addresses. It uses a hierarchical system of root, TLD, and authoritative name servers to resolve names.
The document discusses the Transport Control Protocol (TCP) which provides reliable, ordered and error-checked delivery of data streams between applications running on hosts communicating via an IP network. It describes TCP's key functions including segmentation, error control using acknowledgements and retransmissions, flow control using sliding windows, and multiplexing/demultiplexing of data streams. The key aspects of TCP frames such as sequence numbers, acknowledgement numbers, windows and checksums are also summarized.
The document discusses data link control and framing in computer networks. It describes two main functions of the data link layer: defining frames and performing error detection on frames. It also discusses different types of framing such as fixed-size framing and variable-size framing using character-oriented and bit-oriented protocols. Specific protocols discussed include Stop-and-Wait ARQ which uses positive acknowledgments and retransmissions, and Go-Back-N ARQ which allows for pipelining of multiple frames before requiring an acknowledgment.
This document discusses TCP over wireless networks. It explains that TCP was designed for fixed networks with low delay and errors, but wireless networks have high delay, errors and variable bandwidth. This causes TCP to perform poorly over wireless. The document outlines various techniques to improve TCP performance over wireless like Fast Retransmit and Recovery, Slow Start proposals with larger initial windows, ACK counting and ACK-every-segment. It also discusses protocols like HTTP, RLP that operate between TCP and the wireless transmission layers.
This document provides information about MobileComm Technologies' drive test process for UMTS networks. It includes documentation on tools used for tuning and optimization, parameters measured, call flows, key performance indicators, examples of coverage and interference issues identified, and tips for network tuning. The document contains 47 slides covering topics like coverage verification using P-CPICH measurements, identifying interference and overshooting issues, analyzing call drops, tuning for voice and data calls, and comparing mechanical vs electrical antenna tilts.
This document describes the data acquisition process and network topology for a Sercel 428XL seismic data acquisition system. It discusses how seismic data is acquired by field units, digitized, transmitted through a network of LAU nodes, and finally received and processed by the recording truck. Key components include the field digitizer units, LAU nodes, LCI recorder, and 428XL server. The data passes through various processing stages including analog to digital conversion, multiplexing, filtering, compression and error checking before being received and analyzed by the control node.
The document provides information about various data link layer concepts including:
1. The data link layer provides framing, flow control, and error control between network layers on different machines. It uses devices like switches and bridges.
2. Error detection methods include parity checks, checksums, and CRC to detect errors in transmitted frames.
3. Data link protocols for flow control include stop-and-wait, sliding window protocols, and ARQ methods like go-back-N and selective repeat.
4. Framing encapsulates data with headers and trailers using fixed or variable size frames. Methods like byte stuffing and bit stuffing handle special characters in the data.
TCP provides reliable data transfer through several key features:
- It numbers data bytes and uses acknowledgments to ensure all bytes are received correctly. If bytes are lost, they are retransmitted.
- Congestion control algorithms like slow start and congestion avoidance allow TCP to gradually increase data transfer rates while avoiding overwhelming the network.
- Fast retransmit detects lost packets sooner by retransmitting on three duplicate ACKs, while fast recovery resumes data transfer using ACKs still in the pipe.
This document provides an overview of transport layer protocols TCP, UDP, and SCTP. It discusses the history and evolution of TCP, including key developments like congestion control algorithms. UDP is described as a connectionless and unreliable protocol. SCTP is introduced as a protocol developed to transport telephony signaling over IP networks. It addresses limitations of TCP like head-of-line blocking and provides features like multi-homing and message orientation. The document defines SCTP terminology and describes its chunks, states, congestion control approach, and similarities to TCP. In summary, it serves as a high-level introduction to transport protocols with a focus on motivations and capabilities of SCTP.
Multiplexing and demultiplexing techniques allow the simultaneous transmission of multiple signals across a single data link. When the bandwidth of a medium is greater than the needs of connected devices, multiplexing can be used to share the link and improve transmission efficiency. At the transmitter, multiplexing involves framing data, adding overhead information, and rate matching. At the receiver, demultiplexing requires data retiming, frame recovery, and parsing. Synchronization is important and is achieved through carrier recovery, clock recovery, and frame recovery. Multiplexing hierarchies like T1 and E1 are commonly used standards.
Here is a strategy the prisoners could employ:
1. On the first day, the prisoner who visits the switch room toggles one of the switches to the ON position.
2. On subsequent days, the prisoner toggles the other switch if it is in the OFF position, or says "all prisoners have visited" if both switches are in the ON position.
3. This strategy guarantees that after 31 days, both switches will be in the ON position, allowing the prisoner to correctly say "all prisoners have visited" and ensure all prisoners are set free.
The transport layer provides process-to-process communication and utilizes three main protocols: UDP, TCP, and SCTP. UDP is a connectionless protocol that does not guarantee delivery, while TCP provides reliable, ordered delivery through a connection-oriented approach. SCTP also provides reliable delivery with the added capability of multiple streams. Key aspects of these protocols include port numbers, packet/segment formatting, and connection establishment handshaking.
This document provides an agenda and overview of topics related to the transport layer and networking essentials. The agenda includes discussions of the transport layer, UDP overview, TCP communication process, the socket API, and tools and utilities. Specific topics that will be covered include the role and functions of the transport layer, UDP features and headers, TCP reliability mechanisms like connection establishment and termination, sequence numbers and acknowledgments, window sliding, and data loss/retransmission. The document also provides brief overviews and usage examples for common networking tools like ifconfig, nmcli, route, ping, traceroute, netstat, dig, ncat, nmap, tcpdump, and wireshark.
The document discusses data link control protocols and HDLC. It introduces the need for data link protocols to manage frame exchange over a link, including flow control, error control, and addressing. It describes various flow and error control mechanisms like stop-and-wait, sliding windows, go-back-N, and selective reject ARQ. It also provides details on the HDLC frame structure and operation, including address fields, control fields, information fields, and the exchange of different frame types during initialization, data transfer, and disconnection.
Data link protocols provide control over data exchange at the data link layer through mechanisms like frame synchronization, flow control using stop-and-wait or sliding windows, and error control using automatic repeat request (ARQ) protocols like stop-and-wait, go-back-N, and selective-reject to handle lost or damaged frames. HDLC is a commonly used data link protocol that uses synchronous transmission of frames with flag fields, address fields, control fields, information fields, and frame check sequences along with three phases of operation and different frame types.
This document summarizes multiple access protocols used in computer networks at the data link layer. It discusses random access protocols like CSMA/CD and CSMA/CA that allow nodes to transmit randomly. It also covers controlled access protocols like reservation, polling, and token passing that require nodes to get permission before transmitting. Finally, it describes channelization techniques for sharing bandwidth, including FDMA, TDMA, and CDMA that divide the channel by frequency, time, or code respectively.
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An In-Depth Exploration of Natural Language Processing: Evolution, Applicatio...DharmaBanothu
Natural language processing (NLP) has
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and question answering. This paper first delineates
four phases by examining various levels of NLP and
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followed by a review of the history and progression of
NLP. Subsequently, we delve into the current state of
the art by presenting diverse NLP applications,
contemporary trends, and challenges. Finally, we
discuss some available datasets, models, and
evaluation metrics in NLP.
Cricket management system ptoject report.pdfKamal Acharya
The aim of this project is to provide the complete information of the National and
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31. The latency or delay defines how long it takes for an entire message to completely
arrive at the destination from the time the first bit is sent out from the source.
Latency or Delay
32. • Flow control is a technique for speed matching of transmitter and receiver.
• Flow control ensures that a transmitting station does not overflow a receiving
• station with data.
Flow control
35. Stop and Wait Protocol
Operations:
1. Sender: Transmit a
single frame
2. Receiver: Transmit
acknowledgment (ACK)
3. Goto 1.
The receiver indicates its
readiness to receive data
for each frame
40. Efficiency of the flow control protocol is defined as the ratio of useful
data transmission time to the total time taken to transmit a frame,
including acknowledgment (ACK) and any other overhead.
44. Problems of simple stop and wait
protocol Cont…
•Sender waits for an infinite amount of time
for an acknowledgment.
•Receiver waits for an infinite amount of time
for a data.
• Sender waits for an infinite amount of time
for an acknowledgment.
47. Stop and Wait ARQ
Error control in data link layer is based on ARQ- ie retransmission of data in 3 cases:
1. Lost frame
2. Lost acknowledgment
3. Damaged frame
56. Problem-02:
A channel has a bit rate of 4 Kbps and one way propagation delay
of 20 msec. The channel uses stop and wait protocol. The
transmission time of the acknowledgement frame is negligible.
What should be the minimum frame size to get a channel
efficiency of at least 50%.
57. Given-
Bandwidth = 4 Kbps
Propagation delay (Tp) = 20 msec
Efficiency >= 50%
Let the required frame size = L bits.
Calculating Transmission Delay-
Transmission delay (Tt)
= Packet size / Bandwidth
= L bits / 4 Kbps
Calculating Value Of ‘a’-
a = Tp / Tt
a = 20 msec / ( L bits / 4 Kbps)
a = (20 msec x 4 Kbps) / L bits
Condition For Efficiency To Be At least
50%-
For efficiency to be at least 50%, we must
have- 1 / 1+2a >= 1/2
a <= 1/2
Substituting the value of ‘a’, we get-
(20 msec x 4 Kbps) / L bits <= 1/2
L bits >= (20 msec x 4 Kbps) x 2
L bits >= (20 x 10-3 sec x 4 x 103 bits per
sec) x 2
L bits >= 20 x 4 bits x 2
L >= 160
From here, frame size must be at least
160 bits
Solution-
61. Problem-04:
If the packet size is 1 KB and propagation time is 15 msec, the channel capacity is
109 b/sec, then find the transmission time and utilization of sender in stop and wait
protocol.
62. Solution-
Given-
•Packet size = 1 KB
•Propagation time (Tp) = 15 msec
•Channel capacity = Bandwidth (here) = 109 b/sec
Calculating Transmission Delay-
Transmission delay (Tt)
= Packet size / Bandwidth
= 1 KB / 109 bits per sec
= 210 bits / 109 bits per sec
= 1.024 μsec
Calculating Value Of ‘a’-
a = Tp / Tt
a = 15 msec / 1.024 μsec
a = 15000 μsec / 1.024 μsec
a = 14648.46
Calculating Sender Utilization-
Sender Utilization or Efficiency (η)
= 1 / 1+2a
= 1 / (1 + 2 x 1468.46)
= 1 / 29297.92
92. Response Mode
• A mode basically describes who actually controls data link.
• HDLC communications session uses several modes of data transfer or
communications simply to determine or identify how primary and secondary
stations actually interact with each other.
99. HDLC Flag Field
bit-oriented protocol - it uses bit stuffing to achieve data transparency over
very point-to-point and multipoint links in Data Link Layer (DLL). Transparency
is basically separation of data from control signals.
103. The Frame in fig. is sent from a primary to a secondary.
Answer the following questions:
A) What is the address of the secondary?
B) What is the type of the frame?
C) What is the sender sequence no.(if present)?
D) What is the acknowledgment no.(if present)?
E) Does the frame carry user data? If yes, what is the
value of the data?
01111110 00000111 00101011 0010111001010011 FCS 01111110
01111110 00001111 10001011 FCS 01111110
108. U frame commands and responses can be divided into
five basic functional categories
• Mode setting- control an exchange, to establish the mode of
session.
– Ex. 00 001 Set normal response mode.
• Unnumbered exchange- specific pieces of information such as
a time/date for synchronization.
• Disconnection – DISC, RD, DM ( addressed station to the
initiator)
• Initialization mode- initialize its data link control functions.
• Miscellaneous- RSET, FRMR, XID
110. Data link layer divided into two functionality-
oriented sublayers
111.
112. Random access protocols assign uniform priority to all connected nodes.
Any node can send data if the transmission channel is idle.
No fixed time or fixed sequence is given for data transmission.
Random Access Protocols
Controlled access protocols allow only one node to send data at a
given time.
Before initiating transmission, a node seeks information from other
nodes to determine which station has the right to send. This avoids
collision of messages on the shared channel.
Controlled Access Protocols
Channelization Protocols
Channelization are a set of methods by which the available
bandwidth is divided among the different nodes for simultaneous
data transfer.
113. RANDOM ACCESS
In random access or contention methods, no station is superior to another
station and none is assigned the control over another. No station permits, or
does not permit, another station to send. At each instance, a station that has
data to send uses a procedure defined by the protocol to make a decision on
whether or not to send.
ALOHA
Carrier Sense Multiple Access
Carrier Sense Multiple Access with Collision Detection
Carrier Sense Multiple Access with Collision Avoidance
114. Aloha
• It allows the stations to transmit data at any time whenever they want
• After transmitting the data packet, station waits for some time.
123. The throughput for slotted ALOHA is
S = G × e−G .
The maximum throughput
Smax = 0.368 when G = 1.
The throughput for pure ALOHA is
S = G × e −2G .
The maximum throughput
Smax = 0.184 when G= (1/2).
Note
124.
125. Carrier sense multiple access (CSMA)
• To minimize the chance of collision, the CSMA method was developed.
• The chance of collision can be reduced if a station senses the medium before
trying to use it.
• CSMA requires that each station first listen to the medium (or check the state
of the medium) before sending.
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