CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that...
Transcript of CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that...
![Page 1: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/1.jpg)
CCM 4300 Lecture 4Computer Networks, Wireless and Mobile Communication
1
and Mobile Communication Systems
Dr Shahedur Rahman
School of Science and Technology
![Page 2: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/2.jpg)
Recap of Last Session
�defined a computer network and identified some of
the basic components.
� explored the history of computers and computer
networks and how they have evolved.
2
networks and how they have evolved.
� identified some of the advantages and disadvantages
of using computer networks.
� introduced the various network standards, how they
are created and by whom
![Page 3: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/3.jpg)
Session Content� Lesson Objectives
� Physical layer
� Analogue or Digital?
� bandwidth and throughput
3
� bandwidth and throughput
� Twisted pair, Coaxial cabling and optical fiber
� Data link layer and access control
�MAC – CSMA/CD, Token Passing
![Page 4: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/4.jpg)
Lesson objectives� At the completion of this lesson you should be able to
- understand the difference between analogue and digital communication
- understand the ISO Reference Model Physical Layer specification
4
- understand the ISO Reference Model Data Link Layer specification
- understand the concept of contention protocol
![Page 5: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/5.jpg)
Physical Layer
� It defines everything that is required to support the
transmission and reception of signals (i.e. 1s and 0s)
� The Physical layer has four functional areas:
1. Electrical – signal type, amplitude, etc
5
2. Mechanical – connectors, cabling, etc
3. Procedural – control and timing
4. Functional - requirements for activating, maintaining, and
deactivating a physical link between end systems.
![Page 6: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/6.jpg)
� The physical layer is usually a combination of software
and hardware programming and may include
electromechanical devices.
Physical Layer - cont
6
� All wiring, power, cabling and connections are part of the
physical layer. Without the physical layer functioning
properly none of the upper layers will respond correctly.
� It has no mechanism for determining the significance of
the bits it transmits or receives. The onus for this is
passed on to higher layer protocols
![Page 7: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/7.jpg)
If you were given one word to describe the
physical layer what would it be?
Hint: Think like an electrical engineer!
Question?
7
![Page 8: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/8.jpg)
Physical Layer FunctionFor transmission, the physical layer generally:
� convert framed data from Data Link Layer to a
binary stream
� transmit framed data serially (that is, one bit at
a time) as a binary system
8
a time) as a binary system
For reception, the physical layer generally:
� listens for inbound transmission that are
addressed to its host device
� accept appropriately addressed streams
� pass the binary stream up to the Data Link
Layer for reassembly into frames
![Page 9: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/9.jpg)
Analogue or Digital?
9
� The term analogue refers to any physical device or signal
that can continuously vary in strength or quantity, for
example, voltage in a circuit
![Page 10: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/10.jpg)
Analogue or Digital? - cont
10
Source :
Data Communications,
Computer Networks and
Open Systems
1992
� The term digital refers to any physical device
or signal that is coded in a binary form (i.e. 1s
and 0s)
![Page 11: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/11.jpg)
What is “speed” or capacity?
� In analogue communication bandwidth is the total capacity (or theoretical capacity) of a communication
channel.
bandwidth = highest frequency – lowest frequency
The greater the bandwidth, the more signals
11
The greater the bandwidth, the more signals that can be carried
� Example:
Typical ordinary telephone lines (often called a voice-
grade line) transmit frequencies from 300Hz to
3300Hz.
bandwidth = 3300Hz – 300Hz => 3000Hz, or 3kHz
![Page 12: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/12.jpg)
What is “speed” or capacity? - cont
� In digital communication, bandwidth is referred to as
data rate
� Data rate – amount of data that can be transmitted over
a communications medium in a given period.
12
a communications medium in a given period.
� Data rates measured in bits per second (bps) an can
vary considerably from one type of channel to another.
� For example, the bandwidth of dialup connections using
a modem ranges from 300bps to 33,600bps (33.6kbps) or
56kbps.
![Page 13: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/13.jpg)
What is “speed” or capacity? - cont
� If we measure data rates in bits per second, then what is
baud rate?
� The speed in baud is equal to the number of times the line
condition (i.e. frequency, amplitude, voltage, or phase) changes
per second. i.e., the number of distinctive events per sec.
13
� Named after French engineer Jean Maurice Emile Baudot
(1845 – 1903)
� For example a communication channel transmitting at 2400
baud. If each signal is used to represent one bit, then the baud
rate is equal to the data rate - 2400bps.
� If each signal represents four bits, then the baud rate – 2400,
but the data rate is 4x2400bps = 9600bps.
![Page 14: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/14.jpg)
What is “speed” or capacity? - cont
� Is there any difference between bandwidth and throughput?
� Bandwidth represents a theoretical capacity of a
communications channel.
The “reality rate” is known as throughput.
14
� The “reality rate” is known as throughput.
� Just because a medium or LAN architecture is specified to
operate at a certain data rate, it is not a valid assumption to
assume that this rate will be the actual throughput achieved.
![Page 15: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/15.jpg)
Transmission medium
� Transmission medium can be:
� Simplex
- transmission in one direction only
15
- transmission in one direction only
� Half-duplex
- transmission in both direction; but not at the same
time
� Full-duplex (duplex)
- simultaneous transmission in both directions.
![Page 16: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/16.jpg)
Twisted Pair
� Twisted pair cabling comes in two varieties: shielded and unshielded. Unshielded twisted pair (UTP) is the most popular
� Two insulated wires are twisted around each other, and
combined with others into cable
� Each pair is twisted with a different number of twists per inch -
16
� Each pair is twisted with a different number of twists per inch -
eliminates interference from adjacent pairs and other electrical
devices.
Unshielded twisted pair RJ-45 Connector
![Page 17: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/17.jpg)
Twisted Pair......cont.....
17
![Page 18: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/18.jpg)
Twisted Pair - cont
� Several techniques can be used to improve throughput:
� Increase the thickness of the conductor
� Increase the twist of rate
� Use several different twist rates in bundle of multiple pairs
� Shield the pairs with a metallic barrier
18
� Shield the pairs with a metallic barrier
Type Use
Category 1 Voice Only (Telephone Wire)
Category 2 Data to 4 Mbps (LocalTalk)
Category 3 Data to 10 Mbps (Ethernet)
Category 4 Data to 20 Mbps (16 Mbps Token Ring)
Category 5 Data to 100 Mbps (Fast Ethernet)
![Page 19: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/19.jpg)
Coaxial Cable
� Coaxial cabling has a single copper conductor at its center
� A plastic layer provides insulation between the center
conductor and a braided metal shield.
� The metal shield helps to block any outside interference
from fluorescent lights, motors, and other computers
19
from fluorescent lights, motors, and other computers
Bayone-Neill-Concelman (BNC) Coaxial cable
![Page 20: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/20.jpg)
Coaxial Cable
� The two types of coaxial cabling are thick coaxial and thin
coaxial (refers to diameter - 0.25inch and 0.5inch).
- Thin coaxial cable is also referred to as thinnet. 10Base2
refers to the specifications for thin coaxial cable carrying
20
Ethernet signals. The 2 refers to the approximate maximum
segment length being 200 meters.
- Thick coaxial cable is also referred to as thicknet. 10Base5
refers to the specifications for thick coaxial cable carrying
Ethernet signals.
![Page 21: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/21.jpg)
Optical Fibre
� Optical fiber is a thin, flexible medium capable of conducting
an optical ray
� It transmits light rather than electronic signals eliminating the
problem of electrical interference
� Very high bandwidth (currently up to 10Gbps)
Used for long-distance trunks, local area networks, high-
21
� Used for long-distance trunks, local area networks, high-
speed transmissions
Fibre Optic CableSC Connector
ST Connector
![Page 22: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/22.jpg)
Optical Fibre Connector
22
SC (SubscriberConnector) Connector
SC Duplex Connector
ST (Straight Tip) Connector
![Page 23: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/23.jpg)
Question?
� Which of the following is not defined at the physical layer of
the OSI reference model?
A. hardware addresses
23
B. bitstream transmission
C. voltage levels
D. physical interface
![Page 24: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/24.jpg)
Data Link Layer � Regulates and format transmission of data from software on
a node to the network cabling facilities.
� It acts like a “Glue” between the wire and the software on a
node.
� Some of the services the data link layer provides to the
network layer include:
24
network layer include:
� framing – involves partitioning data into frames with
recognized frame boundaries and exchange these
frames over the link
� frame sequencing – involves maintaining the correct
ordering of frames as they are being exchanged
� establishing and maintaining an acceptable level of flow
control as frames are being exchanged across a link
![Page 25: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/25.jpg)
Data Link Layer - cont
� detecting (and possibly correcting) errors in the
physical layer, which includes error notification when errors
are detected but not corrected
� selecting quality of services (QoS) parameters
associated – ensuring sufficient bandwidth is available and
25
that transmission delays (i.e latency) are predictable and
guaranteed.
the data link layer enables data frames to be transmitted error-free between two end nodes over the physical layer
![Page 26: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/26.jpg)
Data Link Layer - cont
� How is the data link layer implemented within a network?
� Typically implemented on a node as device drive (i.e.
firmware layer of the network interface card), which is a
26
firmware layer of the network interface card), which is a
software component that is specified to both a piece of
hardware (e.g. network interface card), and the
operating system of the computer in which it is installed.
![Page 27: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/27.jpg)
OSI Reference Model vs IEEE 802 Model
� IEEE initiated its development of the LAN standards
with an architectural model, defined in IEEE 802.1
� The architectural model corresponds to the two
lowest layers of the OSI Model with the following
differences:
27
differences:
� The IEEE divides OSI’s data link layer into two parts –
the logical link control (LLC) and the medium access
control (MAC) sublayers
Note:
The MAC sublayer has nothing to do with Apple
Computer’s Machintosh
![Page 28: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/28.jpg)
OSI Reference Model vs IEEE 802 Modle - cont
Network Layer
Data Link Layer
Network Layer
Logical Link Control
28
Data Link Layer
Physical Layer
Physical Layer
Media Access Control
OSI Model
IEEE 802 Model
![Page 29: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/29.jpg)
LLC and MAC
� The LLC sublayer (i.e. upper half of data link layer)
encompass several functions – framing, flow control and error
control
� The MAC sublayer (i.e. lower half of data link layer) provides
29
� The MAC sublayer (i.e. lower half of data link layer) provides
media access management protocols for accessing a shared
medium.
![Page 30: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/30.jpg)
Logical Link Layer - Framing � Framing enables synchronize the transmission and reception
of data since frames have detectable boundaries.
� Integrity of frames - detection and correction
Data set to be transmitted: 1101110011011011
30
Thus, the frame to be transmitted is:
01111110 1101110011011011 01111110
Start of frame User Data End of Frame
![Page 31: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/31.jpg)
Logical Link Layer – Error Control� The term error control refers to the process of guaranteeing
reliable data delivery
� Two basic strategies:
� error control through retransmission (also known as error-
detecting codes) – provides enough information in the data
31
stream to detect errors during transmission (e.g. parity,
cyclic redundancy check (CRC))
� autonomous error correction (also known as error-
correcting codes) – provides redundant information in the
data stream to detect and correct any errors autonomously
(e.g. hamming distance)
![Page 32: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/32.jpg)
Media Access Control� The MAC sublayer provides the protocol that define the
manner in which nodes share the single physical transmission
medium.
� The IEEE 802 specifications recognizes three different forms
of media access:
32
� Contention
� Demand priority (not so common anymore)
� Token passing
![Page 33: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/33.jpg)
Media Access Control - Contention
� Contention based media access is embodied in the Carrier
Sense, Multiple Access with Collision Detection (CSMA/CD)
scheme 802.3
� As its name implies:
- requires station to check the wire to determine whether
33
- requires station to check the wire to determine whether
any other station is already sending data
- If the station can sense an available carrier signal on a
wire, it is free to transmit
� The sensing of carrier signal does not necessarily guarantee
a free transmission media – collide with previously transmitted
signal on what appeared to be an idle medium.
![Page 34: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/34.jpg)
Media Access Control – Token Passing
� Project 802’s specifications include three different token-
based protocols – 802.4 Token Bus, 802.5 Token Ring, and
Fiber Distributed Data Interface (FDDI); generally pronounced
as a word; fiddy.
A token is a special frame that is passed from device to
34
� A token is a special frame that is passed from device to
device, in sequence along the ring.
� It can circulate only when the ring is idle
� A device must have this token to place data frames on the
network.
![Page 35: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/35.jpg)
MAC Protocols: a taxonomy
Access Method
Random Access Taking-turnProtocols /
Channel
35
Random Access Protocols / Contention Protocols /
Round Robin
CDMAFDMATDMA
TokenBus
TokenRing
SlottedRing
Channel Partitioning / Reservation
CSMA/CDAlohaSlotted
Aloha
Goal: efficient, fair, simple, decentralised
![Page 36: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/36.jpg)
Desirable MAC characteristic
||| When only one node tx – throughput R bps
||| When M nodes tx – each node throughput
R/M bps (average tx rate over suitable
defined interval of time)
36
||| Decentralised protocol – no master to bring
system down
||| Simple protocol – inexpensive to implement
![Page 37: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/37.jpg)
Random Access protocols||| When node has packet to send
- transmit at full channel data rate R.
- no a priori coordination among nodes
||| two or more transmitting nodes -> “collision”,
||| random access MAC protocol specifies:
- how to detect collisions
37
- how to detect collisions
- how to recover from collisions (e.g., via delayed retransmissions)
||| Examples of random access MAC protocols:
- pure ALOHA
- slotted ALOHA
- CSMA and CSMA/CD
We will be looking at these issues in the next lecture.
![Page 38: CCM 4300 Lecture 4 - JSinti · CCM 4300 Lecture 4 Computer Networks, ... the more signals 11 that can be carried Example: Typical ordinary telephone lines (often called a voice-](https://reader038.fdocuments.net/reader038/viewer/2022110223/5acbc4587f8b9a27628bb280/html5/thumbnails/38.jpg)
�Physical layer and its function
� Analogue or Digital?
�Speed, data and baud rate, bandwidth and throughput
�Transmission media - Twisted pair, Coaxial cabling and
Summary!
38
�Transmission media - Twisted pair, Coaxial cabling and
optical fiber
� Data link layer, OSI reference model, LLC and MAC,
Token Passing, and access control methods.
Are there any questions?