Ethernet Transmitter Algorithm

Summary

This tutorial covers the Ethernet transmitter algorithm, explaining how it functions with CSMA/CD to manage data transmission on Ethernet networks. It introduces the concept of Manchester encoding for signal conversion and addresses runt frames, which occur due to collisions or network issues. The video also highlights the importance of collision detection and the use of exponential back-off to minimize collision probability, providing a comprehensive understanding of Ethernet communication protocols.

Takeaways

• 😀 The Ethernet transmitter algorithm is a method used by network adapters to manage data transmission over Ethernet cables.
• 🔍 Outcomes of the session include understanding the Ethernet transmitter algorithm, recognizing runt frames, and knowing about exponential back-off.
• 💡 The Ethernet adapter, also known as the Network Interface Card (NIC), is a crucial component that connects a host computer to an Ethernet cable via an RJ45 socket.
• 🌐 The Ethernet Media Access Control (MAC) algorithm is implemented in the hardware of the network adapter and uses CSMA/CD (Carrier Sense Multiple Access with Collision Detection) as its access method.
• 📶 Manchester encoding is the technique used by Ethernet to convert data bits into electrical signals for transmission over copper cables.
• 🚀 The Ethernet transmitter algorithm transmits a frame immediately if the adapter has a frame to send and the channel is idle.
• 🚫 If the line is busy, the algorithm waits until it becomes idle before transmitting, reflecting the CSMA/CD protocol's behavior.
• 💥 Collisions occur when two or more hosts transmit at the same time, leading to a runt frame, which is an Ethernet frame less than 64 bytes.
• 🔁 Exponential back-off is a technique used to reduce collision probability by doubling the waiting time after each failed transmission attempt.
• ⏱️ A runt frame is created when a collision occurs, or due to issues like malfunctioning network cards, buffer under-runs, or duplex mismatches.

Q & A

What are the three outcomes of the session on the Ethernet transmitter algorithm?

The three outcomes of the session are: 1) Understanding the Ethernet transmitter algorithm, 2) Understanding runt frames, and 3) Knowing about exponential back-off.

What is the function of an Ethernet adapter in a host computer?

An Ethernet adapter in a host computer is used to connect an Ethernet cable, allowing the computer to communicate over a network.

What is the access protocol for Ethernet?

The access protocol for Ethernet is Ethernet Media Access Control (MAC) algorithm, which is implemented in the hardware of the network adapter.

What access method does Ethernet use?

Ethernet uses the CSMA/CD (Carrier Sense Multiple Access with Collision Detection) access method.

Why is Manchester encoding technique used by Ethernet?

Ethernet uses the Manchester encoding technique to convert data bits into electrical signals that can be transmitted over copper cables, such as Ethernet cables.

How does the Ethernet transmitter algorithm handle a frame transmission when the channel is idle?

When the adapter has a frame to send and the channel is idle, it transmits the frame immediately.

What is the maximum payload size of an Ethernet frame?

The maximum payload size of an Ethernet frame is 1500 bytes.

Why is Ethernet referred to as a CSMA/CD protocol?

Ethernet is referred to as a CSMA/CD protocol because it uses Carrier Sense Multiple Access with Collision Detection, allowing hosts to detect collisions when they occur during transmission.

What is a runt frame in Ethernet?

A runt frame is an Ethernet frame that is less than 64 bytes in length, typically caused by collisions, malfunctioning network cards, buffer under-runs, or duplex mismatches.

What is the purpose of transmitting a 32-bit jamming sequence in case of a collision?

A 32-bit jamming sequence is transmitted to indicate a collision has occurred, allowing all involved host computers to recognize the collision and stop their transmission.

What is the role of exponential back-off in the Ethernet transmitter algorithm?

Exponential back-off is a technique used by the Ethernet algorithm to reduce the probability of collisions by doubling the waiting time between retransmission attempts after a collision is detected.

Outlines

00:00

🌐 Introduction to Ethernet Transmitter Algorithm

The video begins with an introduction to the Ethernet transmitter algorithm, outlining the session's objectives. The learner is expected to understand the Ethernet transmitter algorithm, recognize runt frames, and learn about exponential back-off upon completion. The Ethernet adapter, also known as the Network Interface Card (NIC), is explained as the component that connects the host computer to the Ethernet cable via an RJ45 socket. The video then delves into the Ethernet media access control (MAC) algorithm, which is implemented in the hardware of the NIC and uses Carrier Sense Multiple Access with Collision Detection (CSMA/CD). The Manchester encoding technique is introduced as the method used to convert data bits into electrical signals for transmission over copper cables.

05:01

🚀 Ethernet Transmitter Operation and Collision Handling

The script explains how the Ethernet transmitter algorithm works, detailing the process of frame transmission when the channel is idle. It emphasizes the maximum payload size of 1500 bytes for Ethernet frames and the conditions under which frames are transmitted. The video discusses the persistent nature of CSMA, where an adapter with a frame to send will transmit with a probability of one when the line becomes idle. Collisions are a key aspect of Ethernet operation, and the video describes how hosts detect collisions using the CSMA/CD protocol. It explains the transmission of a 32-bit jamming sequence upon collision detection and the minimum transmission of 96 bits, which includes a 64-bit preamble and the jamming sequence. The concept of runt frames, which are frames less than 64 bytes caused by collisions or other issues, is introduced, and the video explores worst-case scenarios involving frame collisions and the resulting runt frames.

10:05

🔁 Exponential Back-Off Strategy in Ethernet

The final paragraph discusses the exponential back-off technique used by Ethernet to reduce collision probabilities. After a collision is detected and transmission is halted, the adapter waits for a random period before attempting to resend the frame. If the channel remains busy, the waiting period doubles with each subsequent attempt. This strategy, where the delay interval between retransmission attempts is exponentially increased, is known as exponential back-off. The video concludes with a summary of the Ethernet transmitter algorithm, runt frames, and the importance of the exponential back-off strategy in managing network traffic and minimizing collisions.

Keywords

💡Ethernet Transmitter Algorithm

The Ethernet Transmitter Algorithm is a protocol that governs how data is sent over an Ethernet network. It is a fundamental part of the video's theme, as it dictates how frames are transmitted when the channel is idle. The script mentions that when the adapter (host computer) has a frame to send and the line is idle, it transmits the frame immediately, exemplifying the algorithm in action.

💡Runt Frames

Runt frames are Ethernet frames that are less than the minimum length of 64 bytes. These are significant in the video's discussion on Ethernet transmission errors, often resulting from collisions. The script explains that runt frames are usually a consequence of two frames colliding, but they can also be caused by malfunctioning network cards or duplex mismatches.

💡Exponential Back-off

Exponential Back-off is a collision resolution technique used in Ethernet networks. It is crucial for understanding the video's discussion on managing network congestion. The script describes how, after a collision, a device waits for a random time period before retransmitting, doubling the wait time after each failed attempt, thereby reducing the likelihood of repeated collisions.

💡CSMA/CD

CSMA/CD stands for Carrier Sense Multiple Access with Collision Detection, which is the access method used by Ethernet. It is central to the video's explanation of how Ethernet networks manage multiple devices trying to transmit simultaneously. The script mentions that Ethernet is a CSMA/CD network, where devices sense the channel, and if it's busy, they wait until it's idle before transmitting.

💡Manchester Encoding

Manchester Encoding is a line encoding technique used to represent binary data as electrical signals. It is relevant to the video's discussion on how data is converted into a form suitable for transmission over Ethernet cables. The script explains that Ethernet uses Manchester encoding to convert data bits into electrical signals that can be transmitted over copper cables.

💡Collision

A collision in networking occurs when two or more devices send data simultaneously over the same communication channel. It is a key concept in the video's explanation of Ethernet's operation. The script describes how collisions can occur in Ethernet networks when multiple hosts transmit at the same time, leading to data corruption and the need for retransmission.

💡Jamming Sequence

A Jamming Sequence is a 32-bit pattern transmitted by a device to indicate a collision has occurred. It is highlighted in the video's discussion on how devices detect and respond to collisions. The script mentions that when a device detects a collision, it transmits a jamming sequence to alert other devices and then stops transmitting.

💡Payload

Payload in the context of Ethernet frames refers to the actual data being transmitted. It is an important aspect of the video's discussion on Ethernet frame structure. The script specifies that the maximum payload size in an Ethernet frame is 1500 bytes, which sets an upper limit on the amount of data that can be sent in a single frame.

💡Network Interface Card (NIC)

A Network Interface Card (NIC), also known as a network adapter, is a hardware component that connects a computer to a network. It is integral to the video's explanation of how Ethernet connections are established. The script describes the NIC as the part of the host computer where the Ethernet cable is connected.

💡Ethernet Media Access Control (MAC) Algorithm

The Ethernet MAC Algorithm is implemented in the hardware of network adapters and governs how devices share the communication channel. It is a core part of the video's discussion on Ethernet's operation. The script explains that this algorithm is responsible for managing access to the Ethernet medium, using techniques like CSMA/CD.

💡Duplex Mismatch

Duplex Mismatch occurs when two devices connected via Ethernet operate in different modes of full- or half-duplex. It is mentioned in the video's discussion on potential sources of runt frames. The script explains that if one device is in half-duplex mode (transmits and receives on the same signal pair) and the other is in full-duplex mode (transmits and receives on separate pairs), it can lead to runt frames.

Highlights

Introduction to the Ethernet transmitter algorithm and session outcomes.

Understanding of the Ethernet adapter and its role in connecting the host computer.

Explanation of the Ethernet media access control (MAC) algorithm.

Description of the CSMA/CD access method used by Ethernet.

Importance of Manchester encoding technique in Ethernet.

Process of the Ethernet transmitter algorithm when the channel is idle.

Details on the maximum payload size of an Ethernet frame.

Behavior of the Ethernet transmitter when the line is busy.

Definition and characteristics of the CSMA/CD protocol.

Lack of centralized control in Ethernet and its implications.

How Ethernet detects and handles collisions between frames.

Explanation of the 32-bit jamming sequence during collisions.

Requirement for a transmitter to send at least 96 bits in case of collision.

Definition and causes of runt frames in Ethernet.

Worst-case scenario of the Ethernet transmitter algorithm.

Introduction to the concept of exponential back-off.

Mechanism of exponential back-off to reduce collision probability.

Conclusion summarizing the Ethernet transmitter algorithm, runt frames, and exponential back-off.

Transcripts

hello everyone welcome back today we

will see the Ethernet transmitter

algorithm as usual let's start the

session with the outcomes in today's

session we have three outcomes let's see

what are they upon the completion of the

session the learner will be able to

outcome number one we will understand

that Ethernet transmitter algorithm

outcome number two we will understand

runt frames and last outcome we will

know about exponential back-off before

we step into the ethernet transmitter

algorithm we will see the Ethernet

adapter if we have a host computer and

this host computer will be having an

adapter where this Ethernet cable will

be connected to this or after only I

will show you the Ethernet adapter or

the Ethernet NAC car this is actually

the Ethernet adapter or we will call it

as the NAC card that is the network

interface card this NAC card will be the

part of the host computer so that we can

just plug in our Ethernet cable to this

port in order to connect the ethernet

cable and this port we need rj45 socket

now let's see the access protocol for

Ethernet the algorithm is commonly

called Ethernet media access control

that is Mac algorithm which is

implemented in Hardware of the network

adapter that is already we have seen the

network adapter and this algorithm that

is this Ethernet media access control

algorithm which is implemented in the

hardware of this network adapter and

what's the access method used by

Ethernet it is csma/cd that is carrier

sense multiple access with collision

detection already we have seen about

this carrier sense multiple access with

collision detection technique in one of

the previous lectures if you want to

know more about it I request you to

watch my previous lecture title carrier

sense multiple access and then what is

the encoding scheme that is used by

Ethernet the encoding method is the

Manchester encoding technique why do we

need this Manchester encoding technique

I already told you that the ethernet

cable will be connected through this

port so application layer data is then

given to transport layer then comes to

the network layer then comes to the data

link layer where the same AC card is

actually so the frames that are created

by the host computer have to be

placed on the cables that is this

channel so when it wants to place the

data on the channel we need to do some

encoding technique encoding means the

actual data or the frame that is created

by this host computer have to be

converted into signals because the

Ethernet cable will carry only signals

Ethernet cable is an example of copper

cable so it carries the data in the form

of electrical signals Ethernet uses

Manchester encoding technique for

converting data bits in to signals

let's now dive into the ethernet

transmitter algorithm when the adapter

has a frame to send we know then the

adapter means the host computer has the

frame to send and the channel or the

line is idle and it transmits the frame

immediately because the line is idle so

whenever the her doctor has a frame to

send it sends the frame immediately and

what is the payload size of the frame we

know the upper bound or the maximum size

of the data or the payload in the

Ethernet frame will be of thousand five

hundred bytes so the upper bound of

thousand five hundred bytes in the

message means that the adapter can

occupy the line for a fixed length of

time in the first point we have seen

they adapted as a frame to say in and

the line is idle what is the adapter

ASSA frame on the line is not idle that

is the line is busy the Third Point

answers this situation when the adapter

has a frame to send and the line is busy

it waits for the line to go idle and

then transmits immediately so whenever

it finds that the line is idle it places

the frame

whenever the line is busy this algorithm

waits for a certain period of time and

when it finds the line is idle it places

the frame or it transmits the frame

Ethernet is said to be here CSMA one

persistent protocol why Ethernet is

called as CSMA one persistent protocol

because an adapter with a frame to send

transmits with the probability one

whenever a busy line goes idle so

whenever a busy line goes idle this

adaptive places the frames in order to

send that with the probability of one

and that is why the ethernet is said to

be a CSMA one persistent protocol to

know more about this I request you to

watch my previous lecture title see SME

is there any centralized control in the

ethernet we will see that since there is

no centralized control it is possible

for two or more adapters to begin

transmitting at the same time either

because both found the line to be idle

or both had been waiting for a busy line

to become idle let's assume there are

two host computers when both the host

computers finds the line to be idle

so they place their frames at the same

time and this leads to collision

Ethernet has no centralized control when

the frames collide with each other this

algorithm will intimate the host at the

collision has happened that is why

Ethernet access method is named as

csma/cd csma/cd means carrier sense

multiple access with collision detection

hosts will be able to know whether the

collision has happened or not when two

or more host computer finds the line to

be idle and they places their frames at

the same time when this situation

happens then two or more frames are said

to be collide on the network what

happens when coalition of up and since

Ethernet supports collision detection

each sender is able to determine that

the collision is in progress how host

computers come to know whether collision

has happened or not at the moment an

adapter detects that its frame is

colliding with another frame it first

made sure to transmit a 32 bit jamming

sequence so whenever any node since a 32

bit jamming sequence

it means the frame has collided with

each other then what the host computer

will do it then stops transmission see

please make a note of this point it's a

very important point when the adapter

detects its frame is colliding with

another frame it first makes sure's to

transmit a 32 bit jamming sequence so

that other host will come to note that

collision has happened and this host

computer will stop its transmission

immediately thus a transmitter will

minimally send 96 bits in case of

collision why the host computer has to

send 96 bits because it has to send a 32

bit jamming sequence just to indicate a

collision as happen

just 32 bits are not sufficient it needs

to append a 64-bit preamble so the

transmitter will minimally send 96 bits

in case of collision now let's see what

our run friends our rant frame is an

Ethernet frame that is less than I

Triple E 8 not 2.3 smin among length of

64 bytes when we find a frame which is

less than 64 bytes then these frames are

runt friends you may have a question in

your mind

Ethernet will never create a frame that

is less than the minimum length of 64

bytes then how a run frame is created

because run frames are frames that are

less than 64 bytes these run frames are

most commonly caused by collisions

suppose if two frames are colliding with

each other the result of that collision

will be a run frame normally these run

frames are caused because of collisions

is there any other reasons for creating

runt friends yes we have other reasons

to not only collision there are other

possible causes for creating runt

friends they may be a malfunctioning

network card or the NAC card the buffer

under-run or the duplex mismatch duplex

mismatch means one side of the line it

will be running in half duplex mode and

the other side will be running in full

duplex mode this will also cause run

frames because of software issues in the

host side it can create run friends

let's see the worst case scenarios of

Ethernet transmitter algorithm now let's

see the worst case scenario yay where

air sends a frame at time T that is yeah

is sending its frame at time T let's

come to point number B the frame that

was sent by host computer J will be

received by the destination computer B

at what time years frame will be

received by B so as frame arrives at B

at T plus D why because a time T only

has transmitted the frame so it takes

real time where D is the delay the delay

it involves the transmission delay as

well as the propagation delay so so at T

plus D time

yes frame arrives at B now let's move on

to point number C so B begins

transmitting at T plus D

and collides with yes frame what is

mentioned here is let's assume there are

200 bits in this frame and all bits are

transmitted and received by B except the

last bit that time and the last bit is

received by B at that time B begins its

transmission so what happens and because

of this single bit collision happens so

B begins transmitting at T plus D at T

plus D only year's frame and I should be

at the merge of s frame B begins

transmitting at t plus D and collides

with es frame so what happens both the

frames becomes unusable because of this

collision what happens to this frame it

will be a runt frame we knows this

collision and befriends the runt frame

at what time it will be received this

frame is started at D plus D and it will

take D delay in order to reach a so B's

front frame arrives at yay at what time

T plus 2 D why coalition has happened at

t plus D and this front frame will take

a delay of D in order to reach here the

time it has started his T plus D and it

takes D delay in order to reach so T

plus D plus B is T plus 2 D so B's front

frame arrives at ei at T plus dou T and

before we conclude we will see what is

exponential back-off exponential

back-off is the technique that is used

by Ethernet in order to reduce the

probability of collision let's see how

once an adapter has detected a collision

and stopped its transmission it waits

for a certain amount of time and tries

again after waiting for a certain period

of time the Ethernet algorithm finds the

channel is still busy what it will do

each time the adapter tries to transmit

but fails so it doubles the amount of

time it waits before trying again for

example if the node has waited for one

second previously for the next attempt

it will wait for two seconds after the

expiry of two seconds it will try to

place the frame on the channel again if

it is busy it waits for 4 seconds and it

waits for 8 seconds and it goes on for

every try it doubles the amount of the

it waits before trying again so this

strategy of doubling the delay interval

between each retransmission attempt is

known as the exponential back-off

exponential back-off is the strategy

that is followed by the Ethernet

algorithm in order to reduce the

probability of collision and that's it

guys I hope now you know the Ethernet

transmitter algorithm we understood the

runt frames and we know about the

exponential back-off strategy I hope you

liked the video and thank you for

watching

[Applause]

[Music]