Original subtitles

0 In the section we're going to talk about Ethernet. 1

as we discussed in our previous section. 2

Ethernet is the most widely installed local area network (LAN) technology. Ethernet is a protocol in the describing 3

how networked devices can format data for transmission to other network devices on the same network network 4

segment and how to put data on our network connection. 5

Again as we talked before, data Link layer has 2 sublayers and they are L.L.C. logical link control and 6

MAC: Media Access Control . Organizes communication with upper / lower laysers and Provides common 7

interface, reliability and flow control and MAC Appends physical address to frame and Provides data encapsulation 8

and error detection 9

A collision domain is a network segment connected by a shared 10

medium or through repeaters where data packets may collide with one another while being sent. 11

A network collision occurs when more than one device attempts to send a packet on a network segment 12

at the same time. Members of a collision domain may be involved in collisions with one another. 13

Guys Only one device in the collision domain may transmit at any one time, 14

and the other devices in the domain listen to the network and refrain from transmitting while others are 15

already transmitting in order to avoid collisions. Because only one device may be transmitting at any one 16

time. 17

total network bandwidth is shared among all devices on the collision domain. 18

Collisions also decrease network efficiency on a collision domain as collisions require devices 19

to abort transmission and retransmit at a later time. 20

Collisions are often in a hub environment, because each port on a hub is in the same collision domain. 21

By contrast, each port on a bridge, a switch or a router is in a separate collision domain. 22

here we have a switch and this switch has four ports , four different ports. each port of the switch is a 23

separate collision domain. 24

As you can see in here this is collusion. 25

Domain one. 26

This is collision domain 3. 27

This is collision domain t2o and this is collision domain four. 28

But as you can see in a here separate ports of the hub is not as seperate collision domain. all parts of 29

the hub are in the same collision domain which is collision domain 30

In a shared media , Devices may want to send data at the same time 31

CSMA 32

method is used for sharing the media, but collisions may ocur 33

if two devices try to send data at the same time. on the screen as you can see that all workstations are 34

saying that I send my data when I want. 35

And they don't want to share the media. 36

So we have a method named CSMA/CD collision detection used for detecting collisions 37

for ethernet networks . Logic behind this is : Check media, 38

If it is free send. 39

If not wait for idle and send them later. 40

For example in here if workstation a wants to communicate with the server it sends a message saying 41

that I need to send something. 42

Is there anything currently on the wire or 43

Not 44

CSMA CA Used for detecting collisions for 802.11 wireless networks. . Logic behind 45

This is check media if it is free. 46

Send the notification to use it and then send your data and here how it is going on 47

For example if the tablet want to send data to a wireless medium it's checking the data checking the 48

medium I'm sorry first then it's sending a notification to the medium saying hey guys I'm going to send 49

that data then it's sending whatever it's going to send and let's take a look to Ethernet Frame. 50

in the first fields of Ethernet, we have preamble and SFD 51

between source and destination devices. 52

Secondly we have destination and source address fields. 53

And they are the source and destination MAC address. and the other field is the VLAN Tag which 54

is used for quality of services and carries the VLAN information that is an optional field. 55

And the other field is length and type which keeps the length of data and the type of the protocol we 56

are using. 57

And the other field is the data field which gives the encapsulated data information from Layer 3 and 58

the last field is fcs, frame check sequence and frame check sequence bits must match for source and 59

destination. 60

If no error occured and this field is used for the error detection. Lets take a look to the MAC addr. 61

now. 62

A media access control address (MAC address) of a device is a 48 bit unique identifier assigned to network 63

interfaces for communications at the data link layer of a network segment. MAC addresses are used as a 64

network address for most network technologies, including Ethernet and Wi-Fi. 65

MAC Address is Shown in hexadecimal format , hexadecimal is a positional numeral system 66

with a radix, or base, of 16. 67

It uses 16 68

distinct symbols, most often the symbols 0–9 to 69

As you can see in here 70

A, B, C, D, E, F to represent values ten to fifteen. 71

MAC addresses are assigned to network devices such as PCs, printers, servers etc. And consists 72

of two portions as you can see in here the first portion is all you OUI.. 73

And the second UAA. 74

... 75

The first portion is OUI. An organizationally unique identifier (OUI) is a 24-bit number that 76

uniquely identifies a vendor, manufacturer, or other organization. 77

The second portion is 78

UAA or Extended / Device Identifier. 79

This is a number unique to the vendor. for example lets say that this first portion is unique for 80

for example maybe Intel maybe Qualcomm 81

then the MAC addresses that Intel manufactures or Qualcomm manufacturers are finishing with the 82

arbitrary numbers that the Intel or Qualcomm says 83

MAC Addresses can be represented in three ways mostly. In the first, dots are used between each four charachters. 84

as you can see here. 85

And the second dashes are used between each two charachters 86

Correct. 87

like here you can see as well and in the third double columns are used between each two charachters. 88

There are also three different types of ethernet addresses and they are unicast multicast and broadcast 89

a unicast frame contains the unique MAC address of the destination receiver and unicast 90

address frame is all the send of the specific port leading to the receiver. 91

For example if this computer, computer one wants to communicate with the tree or the switch. 92

And if this is a unicast, frame is going to here but not here and forwarded to here . 93

A multicast frame contains the unique multicast MAC address of an application, protocol, or data stream. A multicast 94

addressed frame is either flooded out all ports (if no multicast optimization is configured) or sent out 95

only the ports interested in receiving the traffic. 96

. If you want to send a multicast layer-2 traffic, your destination MAC should start with 0100.5e 97

... 98

... 99

Let's talk about the broadcast mac address. A broadcast frame is flooded 100

A broadcast frame contains all binary 1’s as the destination address (FFFF.FFFF.FFFF) 101

.. 102

For example if this guy wants to communicate with all these other guys, the source adress of the Ethernet frame is this guy's MAC address and the destination can be here. 103

let's go with ARP. 104

ARP (Address resolution protocol) is Used for resolution of IP address into MAC Address. 105

ARP request is made via broadcast to FFFF.FFFF.FFFF 106

and ARP reply is made by related device as unicast. 107

For example if PC one sends and arp request, the message this message is broadcast, comes to here 108

And let's say the PC one is researching the physical address of the station that has the IP address 21.3 which is PC 3 109

PC 3 takes this request and replies back with its MAC address 110

and this packet is just sent to PC one as unicast. 111

Let's take a look to the ARP table. On networking devices A table, usually called the ARP cache or ARP 112

Table is used to maintain a correlation between each MAC address and its corresponding IP address 113

. ARP provides the protocol rules for making this correlation and providing address conversion in both directions. 114

In here you are seeing an arp table of a router and in here. 115

You're seeing an ARP table of a PC. the command that we are using is show IP arp command to display 116

the ARP cache of a router. 117

And as you can see in here we are seeing the IP addresses and the MAC addresses of the same device on 118

the table. 119

Let's go ahead with LAN switches. A LAN switch is a networking device that connects devices together on 120

a computer network by using packet switching to receive, process, and forward data to the destination device. 121

... 122

Switches mostly operate at Layer-2 of the OSI Model and Provides switching according to MAC addresses 123

Layer-2 of the OSI Model and Provides switching according to MAC addresses 124

using MAC address table. On the LAN switches, there is a table called MACaddress table and 125

... 126

what L2 switch is making is just switching between different ports by using MAC address information 127

located in the MAC address table. 128

Let's see how MAC address table is established on a switch right now. 129

Firstly MAC address table is empty. 130

This is the switch guys and MAC address table is empty. 131

As you can see 132

in the first step if PC one wants to forward the packet to PC 2, switch floods it out off all ports and 133

adds PC ones MAC address to its MAC address table. 134

Well what is going on in here is PC one wants to communicate with PC two, switch checks the frame and 135

then checks the MAC address and immediately adds the PC1's MAC address to the MAC address table 136

and saying that hey on my first port have a MAC address of this 137

Wants to communicate with this MAC address but I don't have this MAC address on this table so I'm flooding the 138

requests out from all my ports. 139

Then let's say the PC two sends unicast reply to PC 1 and switch adds the PC2's MAC address to MAC address 140

stable to then after this process if PC one wants to send the data to PC two frame is forwarded directly 141

in the end. 142

In the end of the day switch learns all of MAC address connected to all of its ports and establishes a 143

full MAC address as you can see in here. and saying that on my first port I have this MAC address on 144

my third port. 145

I have this MAC address on my forth this 7th this, and 8 this.from now on. 146

If this PC 5 wants to communicate with PC one frame is directly forwarded to PC one. 147

Let's go ahead with the duplex options. 148

We have two duplex options : 149

Half duplex and full duplex. Half-duplex is used to describe communication where only... one side can 150

send data at at time. 151

Once one side has finished transmitting its data, the other side can respond. Only one node can send 152

data at a time in half duplex. 153

If both try to send data at the same time, a collision will occur on the network. 154

On the other hand, full-duplex is used to describe communication where both sides are able to 155

send and receive data at the same time. 156

In these cases, there is no danger of a collision and therefore the transfer of data is completed much 157

faster. 158

Let's go ahead with the auto MDX feature. in today's networks using the appropriate cable type is way 159

important guys and certain devices has a great feature to help us preventing wrong 160

Cabling. 161

. Auto MDI-X ports on newer network interfaces detect 162

if the connection would require a crossover, and automatically chooses the MDI or MDI-X configuration to properly match the other end of the link. 163

and let's take a look to the frame forwarding types. 164

We have 3 frame forwarding types.When we are forwarding a frame in our switches ; and they are store and forward, cut through and cut through 165

and cut through fragment free. In store and forward method 166

The frame is forwarded after that whole frame received and there is no CRC. in cut through fast forward 167

the Frame is forwarded after the destination MAC is checked. In cut through fragment free 168

frame is forwarded after 6 to 4 bytes of the frame is checked. 169

Let's go ahead with POE 170

Power over Ethernet or PoE describes any of systems which pass electric power along with data on twisted pair Ethernet 171

cabling. 172

This allows a single cable to provide both data connection and electric power to devices such 173

access points, IP cameras, and VoIP phones. To provide electric over data cables to end devices, End devices 174

also must be supporting POE technology too 175

in here we are seeing a poe switch and we have an access point. 176

IP camera, industrial sensor and voip phone connected to our poe switch. 177

If this switch is supporting poe and also this VOIP phone sensor IP camera and access point are 178

the poe feature.too we don't need that extra power cable we don't need an extra power adapter we don't need anything 179

else. 180

We can provide the power of these devices by using the twisted pair of copper cables. 181

... 182

Let's take a look to the fixed and modular switches. 183

These are the types of the switches guys. fixed configurations switches are fixed in their configuration 184

what that means is that you cannot add features or options to the switch beyond those that orginally 185

came with the switch. 186

The particular model you purchase determines the features and options available 187

For example, if you purchase a 24-port gigabit fixed switch, you cannot add additional ports when 188

you need them. 189

There are typically different configuration choices that vary in how many and what types of ports 190

And let's take a look to modular switches. Modular switches: offer more flexibility in their configuration. Modular 191

Modular switches: offer more flexibility in their configuration. modular switches typically come with different 192

sized 193

chassis that allow for the installation of different numbers of modular line cards the line cards actually 194

contain the ports. 195

The line card fits into the switch chassis 196

like expansion cards fit into a PC. 197

The larger the chassis, the more modules it can support. 198

And mostly this modular switches can carry high traffic and let's take a look a great feature which is 199

A stackable switch is a network switch that is fully functional operating standalone 200

but which can also be set up to operate together with one or more other network switches, with this group 201

of switches showing the characteristics of a single switch 202

but having the port capacity of the sum of the combined 203

switches. The term “stack” refers to the group of switches that have been set up in this way. 204

The common characteristic of a stack acting as a single switch is that there is a single IP address for 205

remote administration of the stack as a whole, not an IP address for the administration of each unit in the 206

stack. 207

And then lastly we to talk about SFP small for Factor pluggable. this small form factor pluggable is a 208

a compact, hot-pluggable optical module transceiver used for both telecommunication and data communications 209

applications and SFP interface. 210

on networking hardware provides the device with a modular interface that the user can easily 211

adapt to various fiber optic and copper networking standards. 212

This is the fiber optic SFP and there are also types of these SFP which supports the copper cables 213

as well.