The document discusses data link layer protocols:
1. It describes the main functions of the data link layer including data link control, framing, error control, flow control, and media access control.
2. It introduces the Stop-and-Wait ARQ, Go-Back-N ARQ, and Selective Repeat ARQ protocols which combine framing, flow control, and error control to deliver data from one node to another over noisy channels.
3. It explains how these protocols use sequence numbers, sliding windows, and acknowledgments to provide flow and error control.
Data Link Layer
The main goal of this layer is providing reliability to the layers above it.
3.1 DLL Design Issues
What are the services provided by DLL?
3.2 Error Detection and Correction
Adding redundancy in order to find and correct errors.
3.3 DLL Protocols
xxx
3.4 Sliding Window Protocols
xxx
3.5 Protocol Specification and Verification
xxx.
3.6 Examples
Data Link Layer
The main goal of this layer is providing reliability to the layers above it.
3.1 DLL Design Issues
What are the services provided by DLL?
3.2 Error Detection and Correction
Adding redundancy in order to find and correct errors.
3.3 DLL Protocols
xxx
3.4 Sliding Window Protocols
xxx
3.5 Protocol Specification and Verification
xxx.
3.6 Examples
Introduction to the Network Layer: Network layer services, packet switching, network layer performance, IPv4 addressing, forwarding of IP packets, Internet Protocol, ICMPv4, Mobile IP Unicast Routing: Introduction, routing algorithms, unicast routing protocols. Next generation IP: IPv6 addressing, IPv6 protocol, ICMPv6 protocol, transition from IPv4 to IPv6. Introduction to the Transport Layer: Introduction, Transport layer protocols (Simple protocol, Stop-and-wait protocol, Go-Back-n protocol, Selective repeat protocol, Bidirectional protocols), Transport layer services, User datagram protocol, Transmission control protocol
The TCP/IP protocol suite does not define any protocol in the data-link layer or
physical layer. These two layers are territories of networks that when connected
make up the Internet. These networks, wired or wireless, provide services to the upper
three layers of the TCP/IP suite. This may give us a clue that there are several standard
protocols in the market today. For this reason, we discuss the data-link layer in several
chapters. This chapter is an introduction that gives the general idea and common issues
in the data-link layer that relate to all networks.
❑ The first section introduces the data-link layer. It starts with defining the concept
of links and nodes. The section then lists and briefly describes the services provided
by the data-link layer. It next defines two categories of links: point-to-point
and broadcast links. The section finally defines two sublayers at the data-link layer
that will be elaborated on in the next few chapters.
❑ The second section discusses link-layer addressing. It first explains the rationale
behind the existence of an addressing mechanism at the data-link layer. It then
describes three types of link-layer addresses to be found in some link-layer protocols.
The section discusses the Address Resolution Protocol (ARP), which maps
the addresses at the network layer to addresses at the data-link layer. This protocol
helps a packet at the network layer find the link-layer address of the next node for
delivery of the frame that encapsulates the packet. To show how the network layer
helps us to find the data-link-layer addresses, a long example is included in this
section that shows what happens at each node when a packet is travelling through
the Internet.
The sender initializes the checksum to 0 and adds all data items and the checksum. However, 36 cannot be expressed in 4 bits. The extra two bits are wrapped and added with the sum to create the wrapped sum value 6. The sum is then complemented, resulting in the checksum value 9 (15 − 6 = 9).
Introduction to the Network Layer: Network layer services, packet switching, network layer performance, IPv4 addressing, forwarding of IP packets, Internet Protocol, ICMPv4, Mobile IP Unicast Routing: Introduction, routing algorithms, unicast routing protocols. Next generation IP: IPv6 addressing, IPv6 protocol, ICMPv6 protocol, transition from IPv4 to IPv6. Introduction to the Transport Layer: Introduction, Transport layer protocols (Simple protocol, Stop-and-wait protocol, Go-Back-n protocol, Selective repeat protocol, Bidirectional protocols), Transport layer services, User datagram protocol, Transmission control protocol
The TCP/IP protocol suite does not define any protocol in the data-link layer or
physical layer. These two layers are territories of networks that when connected
make up the Internet. These networks, wired or wireless, provide services to the upper
three layers of the TCP/IP suite. This may give us a clue that there are several standard
protocols in the market today. For this reason, we discuss the data-link layer in several
chapters. This chapter is an introduction that gives the general idea and common issues
in the data-link layer that relate to all networks.
❑ The first section introduces the data-link layer. It starts with defining the concept
of links and nodes. The section then lists and briefly describes the services provided
by the data-link layer. It next defines two categories of links: point-to-point
and broadcast links. The section finally defines two sublayers at the data-link layer
that will be elaborated on in the next few chapters.
❑ The second section discusses link-layer addressing. It first explains the rationale
behind the existence of an addressing mechanism at the data-link layer. It then
describes three types of link-layer addresses to be found in some link-layer protocols.
The section discusses the Address Resolution Protocol (ARP), which maps
the addresses at the network layer to addresses at the data-link layer. This protocol
helps a packet at the network layer find the link-layer address of the next node for
delivery of the frame that encapsulates the packet. To show how the network layer
helps us to find the data-link-layer addresses, a long example is included in this
section that shows what happens at each node when a packet is travelling through
the Internet.
The sender initializes the checksum to 0 and adds all data items and the checksum. However, 36 cannot be expressed in 4 bits. The extra two bits are wrapped and added with the sum to create the wrapped sum value 6. The sum is then complemented, resulting in the checksum value 9 (15 − 6 = 9).
Data Link Control
FRAMING
The data link layer needs to pack bits into frames, so that each frame is distinguishable from another. Our postal system practices a type of framing. The simple act of inserting a letter into an envelope separates one piece of information from another; the envelope serves as the delimiter.
Thinking of getting a dog? Be aware that breeds like Pit Bulls, Rottweilers, and German Shepherds can be loyal and dangerous. Proper training and socialization are crucial to preventing aggressive behaviors. Ensure safety by understanding their needs and always supervising interactions. Stay safe, and enjoy your furry friends!
it describes the bony anatomy including the femoral head , acetabulum, labrum . also discusses the capsule , ligaments . muscle that act on the hip joint and the range of motion are outlined. factors affecting hip joint stability and weight transmission through the joint are summarized.
Acetabularia Information For Class 9 .docxvaibhavrinwa19
Acetabularia acetabulum is a single-celled green alga that in its vegetative state is morphologically differentiated into a basal rhizoid and an axially elongated stalk, which bears whorls of branching hairs. The single diploid nucleus resides in the rhizoid.
This presentation includes basic of PCOS their pathology and treatment and also Ayurveda correlation of PCOS and Ayurvedic line of treatment mentioned in classics.
This slide is special for master students (MIBS & MIFB) in UUM. Also useful for readers who are interested in the topic of contemporary Islamic banking.
Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
This slides describes the basic concepts of ICT, basics of Email, Emerging Technology and Digital Initiatives in Education. This presentations aligns with the UGC Paper I syllabus.
Exploiting Artificial Intelligence for Empowering Researchers and Faculty, In...Dr. Vinod Kumar Kanvaria
Exploiting Artificial Intelligence for Empowering Researchers and Faculty,
International FDP on Fundamentals of Research in Social Sciences
at Integral University, Lucknow, 06.06.2024
By Dr. Vinod Kumar Kanvaria
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
2. Data Link Layer – Main Functions
• Data Link Control – procedures for node to
node communications
• Framing
• Error Control
• Flow Control
• Media Access Control – procedures to share
the link
3. 11.3
FRAMINGFRAMING
The data link layer needs to pack bits intoThe data link layer needs to pack bits into framesframes, so, so
that each frame is distinguishable from another. Ourthat each frame is distinguishable from another. Our
postal system practices a type of framing. The simplepostal system practices a type of framing. The simple
act of inserting a letter into an envelope separates oneact of inserting a letter into an envelope separates one
piece of information from another; the envelope servespiece of information from another; the envelope serves
as the delimiter.as the delimiter.
6. 11.6
Bit stuffing is the process of adding one
extra 0 whenever five consecutive 1s
follow a 0 in the data, so that the
receiver does not mistake
the pattern 01111110 for a flag.
Note
8. 11.8
FLOW AND ERROR CONTROLFLOW AND ERROR CONTROL
• Two important responsibilities of the data link layerTwo important responsibilities of the data link layer
areare flow controlflow control andand error controlerror control..
• Flow control refers to a set of procedures used to
restrict the amount of data that the sender can
send before getting an acknowledgment.
• Error control in the data link layer are procedures
based on automatic repeat request (ARQ), which is
the retransmission of data.
9. 11.9
PROTOCOLSPROTOCOLS
Now let us see how the data link layer can combineNow let us see how the data link layer can combine
framing, flow control and error control to achieve theframing, flow control and error control to achieve the
delivery of data from one node to another. Thedelivery of data from one node to another. The
protocols are normally implemented in software byprotocols are normally implemented in software by
using one of the common programming languages. Tousing one of the common programming languages. To
make our discussions language-free, we have writtenmake our discussions language-free, we have written
in pseudocode a version of each protocol thatin pseudocode a version of each protocol that
concentrates mostly on the procedure instead ofconcentrates mostly on the procedure instead of
delving into the details of language rules.delving into the details of language rules.
11. 11.11
NOISELESS CHANNELSNOISELESS CHANNELS
Let us first assume we have an ideal channel in whichLet us first assume we have an ideal channel in which
no frames are lost, duplicated, or corrupted. Weno frames are lost, duplicated, or corrupted. We
introduce two protocols for this type of channel.introduce two protocols for this type of channel.
15. 11.15
Figure shows an example of communication using this
protocol. It is very simple. The sender sends a sequence of
frames without even thinking about the receiver. To send
three frames, three events occur at the sender site and
three events at the receiver site. Note that the data frames
are shown by tilted boxes; the height of the box defines
the transmission time difference between the first bit and
the last bit in the frame.
Example
16. 11.16
Flow diagram for Example
Assumption in simplest protocol ?
Besides the ideal channel, receiver also ideal, ie., can
immediately process all transmitted frames.
20. 11.20
Figure shows an example of communication using this
protocol. It is still very simple. The sender sends one
frame and waits for feedback from the receiver. When the
ACK arrives, the sender sends the next frame. Note that
sending two frames in the protocol involves the sender in
four events and the receiver in two events.
Example
22. 11.22
NOISY CHANNELSNOISY CHANNELS
Although the Stop-and-Wait Protocol gives us an ideaAlthough the Stop-and-Wait Protocol gives us an idea
of how to add flow control to its predecessor, noiselessof how to add flow control to its predecessor, noiseless
channels are nonexistent. We discuss three protocolschannels are nonexistent. We discuss three protocols
for noiseless channels that use flow and error control.for noiseless channels that use flow and error control.
• Stop-and-Wait Automatic Repeat Request
• Go-Back-N Automatic Repeat Request
• Selective Repeat Automatic Repeat Request
23. 11.23
Error correction in Stop-and-Wait ARQ
is done by keeping a copy of the sent
frame and retransmission of the frame
when the timer expires.
Note
25. 11.25
In Stop-and-Wait ARQ, we use sequence
numbers to number the frames.
The sequence numbers are based on
modulo-2 arithmetic, ie. The sequence is
0, 1, 0, 1, 0, 1 … .
Note
26. 11.26
In Stop-and-Wait ARQ, the
acknowledgment number always
announces in modulo-2 arithmetic the
sequence number of the next frame
expected.
Note
31. 11.31
Figure shows an example of Stop-and-Wait ARQ.
Frame 0 is sent and acknowledged. Frame 1 is lost and
resent after the time-out. The resent frame 1 is
acknowledged and the timer stops. Frame 0 is sent and
acknowledged, but the acknowledgment is lost. The
sender has no idea if the frame or the acknowledgment
is lost, so after the time-out, it resends frame 0, which is
acknowledged.
Example
33. 11.33
Assume that, in a Stop-and-Wait ARQ system, the
bandwidth of the line is 1 Mbps, and 1 bit takes 20 ms to
make a round trip. What is the bandwidth-delay product?
If the system data frames are 1000 bits in length, what is
the utilization percentage of the link?
Solution
The bandwidth-delay product is
Example
The bandwidth-delay product defines
the number of bits that can fill the link.
34. 11.34
The system can send 20,000 bits during the time it takes
for the data to go from the sender to the receiver and then
back again. However, the system sends only 1000 bits. We
can say that the link utilization is only 1000/20,000, or 5
percent. For this reason, for a link with a high bandwidth
or long delay, the use of Stop-and-Wait ARQ wastes the
capacity of the link.
Example (continued)
35. 11.35
What is the utilization percentage of the link in
previous Example if we have a protocol that can send
up to 15 frames before stopping and worrying about
the acknowledgments?
Solution
The bandwidth-delay product is still 20,000 bits. The
system can send up to 15 frames or 15,000 bits during a
round trip. This means the utilization is 15,000/20,000, or
75 percent. Of course, if there are damaged frames, the
utilization percentage is much less because frames have
to be resent.
Example
37. 11.37
In the Go-Back-N Protocol, the sequence
numbers are modulo 2m
, where m is the size of
the sequence number field in bits, ie. for a 4
bit field, the sequence numbers can be 0 to 15
inclusive. The sequence can then be repeated.
Note
38. 11.38
The send window is an abstract concept
defining an imaginary box of size 2m
− 1
with three variables: Sf, Sn, and Ssize.
Note
40. 11.40
The send window can slide one
or more slots when a valid
acknowledgment arrives.
Note
41. 11.41
The receive window is an abstract
concept defining an imaginary box
of size 1 with one single variable Rn.
The window slides
when a correct frame has arrived;
sliding occurs one slot at a time.
Note
50. 11.50
Example
Figure shows an example of Go-Back-N. This is an
example of a case where the forward channel is reliable,
but the reverse is not. No data frames are lost, but some
ACKs are delayed and one is lost. The example also
shows how cumulative acknowledgments can help if
acknowledgments are delayed or lost. After initialization,
there are seven sender events. Request events are
triggered by data from the network layer; arrival events
are triggered by acknowledgments from the physical
layer. There is no time-out event here because all
outstanding frames are acknowledged before the timer
expires. Note that although ACK 2 is lost, ACK 3 serves
as both ACK 2 and ACK 3. There are four receiver events.
52. 11.52
Figure shows what happens when a frame is lost. Frames
0, 1, 2, and 3 are sent. However, frame 1 is lost. The
receiver receives frames 2 and 3, but they are discarded
because they are received out of order. The sender
receives no acknowledgment about frames 1, 2, or 3. Its
timer finally expires. The sender sends all outstanding
frames (1, 2, and 3) because it does not know what is
wrong. Note that the resending of frames 1, 2, and 3 is the
response to one single event. When the sender is
responding to this event, it cannot accept the triggering of
other events. This means that when ACK 2 arrives, the
sender is still busy with sending frame 3.
Example
53. 11.53
The physical layer must wait until this event is completed
and the data link layer goes back to its sleeping state. We
have shown a vertical line to indicate the delay. It is the
same story with ACK 3; but when ACK 3 arrives, the
sender is busy responding to ACK 2. It happens again
when ACK 4 arrives. Note that before the second timer
expires, all outstanding frames have been sent and the
timer is stopped.
Example (continued)