Ethernet Transmitter Algorithm
Summary
TLDRThis 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
- đ The Ethernet transmitter algorithm is a method used by network adapters to manage data transmission over Ethernet cables.
- đ Outcomes of the session include understanding the Ethernet transmitter algorithm, recognizing runt frames, and knowing about exponential back-off.
- đĄ 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.
- đ 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.
- đ¶ Manchester encoding is the technique used by Ethernet to convert data bits into electrical signals for transmission over copper cables.
- đ The Ethernet transmitter algorithm transmits a frame immediately if the adapter has a frame to send and the channel is idle.
- đ« If the line is busy, the algorithm waits until it becomes idle before transmitting, reflecting the CSMA/CD protocol's behavior.
- đ„ 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.
- đ Exponential back-off is a technique used to reduce collision probability by doubling the waiting time after each failed transmission attempt.
- â±ïž 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
đ 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.
đ 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.
đ 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.
Mindmap
Keywords
đĄEthernet Transmitter Algorithm
đĄRunt Frames
đĄExponential Back-off
đĄCSMA/CD
đĄManchester Encoding
đĄCollision
đĄJamming Sequence
đĄPayload
đĄNetwork Interface Card (NIC)
đĄEthernet Media Access Control (MAC) Algorithm
đĄDuplex Mismatch
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]
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