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ITN02 - Protocols and Models — Transcript

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0:01Hi, hello there.
0:02Welcome to Protocols and Models.
0:05You know the basic components of a
0:07simple network,
0:08as well as the initial configuration.
0:11But after you configured and connected
0:13these components,
0:15how do you know they will work together?
0:18Protocols.
0:19Protocols are set of agreed-upon rules
0:22that have been created by standards
0:24organizations.
0:26But because you cannot pick up a rule
0:28and look at it closely,
0:30how do you truly understand why there is
0:32such a rule
0:34and what it is supposed to do?
0:37Models.
0:38Models gives you a way to visualize the
0:41rules
0:42and their place in your network.
0:45This module
0:46gives you an overview of network
0:48protocols and models.
0:50You are about to have a much deeper
0:52understanding
0:54of how networks actually work.
1:01So, for the module objective, so at the
1:03end of this video lecture, you should be
1:05able to explain how network protocols
1:08enable devices to access local and
1:10remote network resources.
1:12Also listed here
1:14are the topic objectives with their
1:17corresponding topic title.
1:19So, let's get started.
1:23So, let's start with the rules.
1:30Okay.
1:31So, networks vary in size, shape, and
1:36function.
1:38They can be as complex as devices
1:40connected across the internet or as
1:42simple as two computers
1:45directly connected to one another with a
1:47single cable and anything in between.
1:50However,
1:52simply having a wired or wireless
1:54physical connection between devices is
1:56not enough to enable communication.
1:59So, for communication to occur, devices
2:02must know how to communicate.
2:06So, people exchange ideas using many
2:09different communication methods.
2:11However, all communication methods have
2:14the following three components in
2:15common.
2:17So, these are the sender,
2:19the receiver,
2:21and
2:22the channel or the media.
2:25So, the message source is the sender.
2:29Message sources are people or electronic
2:32devices that need to send message
2:35to other individuals or devices.
2:38So, when you say receiver,
2:40the message destination,
2:43the destination receives the message and
2:46interprets it.
2:48And the third one is the channel or the
2:50media.
2:51This consists of the media that provides
2:54the pathway
2:55over which the message travels from the
2:58source
2:59to destination.
3:01So, this basically is a wired or
3:04wireless.
3:06All right?
3:10So, let's talk about communication
3:11protocols. So, sending a message whether
3:14by face-to-face communication or over
3:16the network is governed by rules called
3:20protocols.
3:21So, these protocols are specific to the
3:24type of communication method being used.
3:28So, in our day-to-day personal
3:29communication,
3:31the rules we use to communicate over one
3:33medium,
3:34like a telephone call, are not
3:36necessarily the same as the rules for
3:39using another medium, such as sending a
3:42letter.
3:44The process of sending a letter is
3:46similar to communication that occurs in
3:49computer networks.
3:56So, let's take the rule of
3:58establishment.
4:00So, individuals must use established
4:03rules or agreements to govern the
4:06conversation.
4:07So, the first message is difficult to
4:09read because it is not formatted
4:11properly.
4:13The second shows the message properly
4:15formatted.
4:17Okay?
4:18So, before communicating with one
4:20another, individuals must establish
4:23rules or agreement to govern the
4:25conversation as mentioned earlier.
4:28So, notice how it is difficult to read
4:30the message because it is not formatted
4:32properly.
4:34It should be written using rules,
4:36example protocols, that are necessary
4:39for effective communication.
4:41The example shows the message which is
4:44now formatted for language and grammar.
4:47So, if you will observe on the first
4:49message here,
4:50so, it is not properly formatted because
4:52if you will observe the word difficult
4:54is a single word here.
4:56Okay?
4:57So, to understand is a single word.
5:00So, if it is properly formatted, then we
5:03will be able to understand it.
5:05Okay? So, that is the rule of
5:07establishment. We have to specify the
5:09rule before we converse or before we
5:12initiate a communication.
5:18Okay?
5:19So, protocols must account for the
5:22following requirements: an identified
5:24sender and receiver,
5:26common language and grammar, speed and
5:29timing of delivery,
5:31and confirmation or acknowledgement
5:33requirements.
5:38So, next is network protocol
5:40requirements.
5:42The protocols that are used in the
5:44network communications share many of
5:46these fundamental traits.
5:49In addition to identifying the source
5:51and destination
5:53computer and network protocols define
5:55the details of how a message is
5:57transmitted across the network.
6:00Common computer protocols include the
6:02following requirements.
6:04You've got message encoding
6:06message formatting and encapsulation
6:09message size timing and delivery
6:13options.
6:14Okay? So, let us discuss these
6:17components or requirements in detail.
6:22First is message encoding.
6:25So, one of the first steps to sending a
6:28message is encoding.
6:30Encoding is the process of converting
6:32information
6:33into another acceptable form
6:36for transmission.
6:38Decoding reverses this process to
6:40interpret the information.
6:43So, let's have the analogy.
6:45Okay?
6:46So, the analogy is to communicate the
6:49message.
6:51Okay?
6:52So, maybe we have a a people
6:55communicating here.
6:57Okay? So, maybe it's a male and a
6:59female.
7:00Okay? So, to communicate the message,
7:03she converts her thoughts into an
7:05agreed-upon language.
7:07She then speaks the words using the
7:09sounds
7:10and inflection of spoken language that
7:13convey the message.
7:14Her friend listened to the description
7:17and decodes the sounds to understand the
7:20message he received.
7:22Okay? So, in the network
7:26in the network, we also have the same.
7:29Encoding between hosts
7:32must be in appropriate format for the
7:34medium.
7:36So, messages sent across the network are
7:38first converted into bits by sending
7:41host.
7:43Each bit is encoded into a pattern of
7:46voltages on copper wires,
7:48infrared light in optical fibers, or
7:52microwaves for wireless systems.
7:55So, the destination host receives and
7:57decodes the signal to interpret the
7:59message.
8:06Next is message formatting and
8:08encapsulation.
8:10Okay? So, let's have an analogy here.
8:13Okay, so you've got the letter.
8:16And of course, this is the
8:19uh packet type.
8:21Okay?
8:22So, a common example for requiring the
8:24correct format in human communication is
8:26when sending a letter.
8:28So, an envelope has the address of the
8:30sender and the receiver.
8:32Okay? So, of course, this one here on
8:34the upper left person is the sender, and
8:37the receiver is of course at the center
8:38of the envelope.
8:41Okay? So, um an envelope has the address
8:44of the sender and the receiver, each
8:46located at the proper place of the
8:49envelope.
8:50So, if the destination address and
8:52formatting are not correct, the letter
8:54is not delivered.
8:56The process of placing one message
8:58format, the letter, inside another
9:01message format, the envelope, is called
9:03encapsulation.
9:05Okay? De-encapsulation occurs
9:08when the process is reversed by the
9:10recipient, and the letter is removed
9:13from the envelope.
9:16Now, talking about the network,
9:20okay? So, similar to sending a letter, a
9:22message that is sent over a computer
9:25network follows specific format rules
9:28for it to be delivered and processed.
9:30So, the Internet Protocol, or IP,
9:33is a protocol with similar function to
9:35the envelope example.
9:37Okay?
9:38So, on this figure
9:40the fields of the internet protocol
9:42version six.
9:45Okay, so for instance, this is an IPV6.
9:48All right?
9:50And the packet identity or the the
9:52packet is identified
9:54by the source of the packet and its
9:56destination. So, IP is responsible for
9:58sending a message
10:00from the message source to destination
10:02over one or more networks.
10:06So, you've got the source IP address
10:07here and the destination IP. So, same
10:10thing with a letter,
10:11you've got the source or the sender and
10:13you've got the recipient or
10:16the destination.
10:17Okay?
10:20Next is let's talk about the message
10:23size.
10:24Okay? So, another rule for communicating
10:28is the message size.
10:30Okay? So, let's have an analogy here.
10:33Okay? So, when people communicate with
10:35each other,
10:36the messages that they send are usually
10:39broken into smaller parts or sentences.
10:42So, these sentences are limited in size
10:44to what is receiving a person can
10:46process at one time.
10:48Okay?
10:49So, it also makes it easier for the
10:51receiver to read and comprehend.
10:56All right? Now, in the network like what
10:58you can see here,
11:01so when a long message is sent from the
11:04host
11:05to a destination on the network, it is
11:08necessary to break the language
11:10or to break the message into smaller
11:12pieces as shown on this diagram here.
11:15Okay? So, we will not be forwarding the
11:17entire message as it is, but basically
11:21it is broken down into pieces
11:23and forwarded it to from the source to
11:25destination.
11:27Okay? So, they can also be different
11:29depending on the channel used.
11:31Frames that are too long or too short
11:34are not delivered.
11:36So, the size restriction of the frames
11:38require the source
11:40host to break a long message into
11:42individual pieces
11:43that meet both the minimum and the
11:45maximum size requirements.
11:48So, the long message will be sent in the
11:50separate frames with each frame
11:52containing a piece of the original
11:54message.
11:56Each frame will also have its own
11:59addressing information.
12:01At the receiving host,
12:03the individual pieces of the message are
12:05reconstructed into an original message.
12:09So, that's how it works for the message
12:10size.
12:13Next is message timing.
12:16Okay? So, message timing is also very
12:19important in network communications.
12:21Message timing includes the following.
12:24So, you've got flow control,
12:26response timeout, and access method.
12:30So, for flow control,
12:33this is the process of managing the rate
12:35of data transmission.
12:38Flow control defines how much
12:39information can be sent
12:42and the speed at which it can be
12:44delivered. For example,
12:47if one person is speaks too quickly,
12:50it may be difficult for the receiver to
12:52hear and understand the message.
12:55In network communications,
12:57there are also network protocols used by
12:59the source and destination devices to
13:02negotiate and manage the flow of
13:04information.
13:06Okay?
13:07So, next is response timeout.
13:11So, if a person asks a question and does
13:14not hear a response within an accept
13:17acceptable amount of time,
13:19so the person assumes that no answer is
13:22coming and reacts accordingly.
13:26Okay? So, the person may repeat the
13:28question or instead may go on with the
13:31conversation.
13:33Hosts on the network use network
13:35protocols
13:37that specify how long to wait for
13:40responses and what action to take if a
13:43response time out occurs.
13:46So, that's response time out.
13:50So, the third one is access method.
13:52So, this determines when someone can
13:55send a message.
13:57Okay?
13:59So, likewise
14:01when a device wants to transmit on a
14:02wireless LAN, it is necessary for the
14:05wireless LAN network interface card or
14:07NIC to determine whether the wireless
14:10medium is available or not.
14:13Okay?
14:14So,
14:16that is access method. So, we will be
14:18dealing with the access method
14:20okay, later in the course.
14:24Now, let's move on to the next slide.
14:28So, the next one is the message delivery
14:30options.
14:31Okay? So, a message can be delivered in
14:34different ways. So, it could be unicast,
14:37multicast, or broadcast.
14:40Okay? So, let's go back to our analogy.
14:43So, sometimes a person wants to
14:45communicate information to a single
14:47individual.
14:49At other times, the person may need to
14:51send information to a group of people
14:54at the same time or
14:56even to all the people in the same area.
14:59Okay?
15:00So,
15:01in the network
15:03network communications has similar
15:05delivery options to communicate.
15:07Okay? So, as shown here in the figure
15:11so, you've got unicast,
15:13multicast, and broadcast.
15:16So, when you say unicast, information is
15:19being transmitted to a single end
15:21device.
15:23Okay? So, it's coming from the source
15:24going to a specific destination. This is
15:27a one-to-one communication. We call it
15:29unicast.
15:31Okay?
15:32So, the next one is multicast.
15:34Information is being transmitted to one
15:36or more end devices.
15:39Okay? Now, in this diagram here,
15:42the source is communicating with the two
15:44computers on the network.
15:47Okay?
15:48So, and then the third one is a
15:50broadcast. Okay? Broadcast information
15:53is being transmitted to all the devices
15:55on the network.
15:57Okay? Like on this video lecture,
16:00okay? So, this video lecture is a
16:02multicast if it is not shared publicly.
16:06Okay? So, it it is becoming a multicast
16:10when there are intended people or
16:12audiences only who is authorized to view
16:15this video.
16:17Okay?
16:17And unicast if I am talking directly to
16:21you.
16:23All right? If I am talking to directly
16:25to a certain person, we call it unicast.
16:31Okay?
16:32So, how about the rules and note about
16:37the node icon.
16:39So, what do we mean by this? Okay?
16:41Networking documents and topologies
16:44often represent networking and the end
16:46devices using a node icon.
16:49So, nodes are typically represented as a
16:51circle.
16:52So, the figure here
16:54shows a comparison of the three
16:55different delivery options using a node
16:58instead of computer icons. So, if you
17:01will observe here,
17:03on this first diagram here, this is from
17:05orange to green. So, we could say that
17:07this is a unicast communication.
17:10All right? So, from orange to green,
17:13Okay? So, but then in that group,
17:16there are yellow and green.
17:19But the message is intended for the
17:21green one. So therefore, we call it
17:23multicast.
17:24Okay?
17:26So if you are going to broadcast it to
17:28all the green
17:30or to all the yellow, we call it
17:32broadcast.
17:34All right?
17:37Okay. So let's talk about protocols now.
17:40So protocols are defined earlier as the
17:43rules that governs in data
17:45communications.
17:47You know that for the end devices to be
17:48able to communicate over the network,
17:51each device must abide by the same set
17:54of rules.
17:55These rules are called protocols.
17:58And they have
18:00many functions in the network.
18:02So this topic gives you an overview
18:05about network protocols. So we have a
18:08thousands of protocols being used on a
18:10network.
18:13Okay. All right.
18:15So network protocols define a common
18:17format and set of rules for exchanging
18:20messages between devices.
18:23So protocols are important
18:25or implemented by the end devices and
18:28intermediary devices
18:31in software, hardware, or both.
18:34So each network protocol has its own
18:36function, format, and rules for
18:40communications.
18:41So the table here
18:43lists various types of protocols that
18:46are needed to enable communications
18:48across one or more networks.
18:52Okay? So protocols are divided into
18:55network communications, network
18:57security, routing, and service
19:00discovery.
19:02When you say network communications,
19:04it enables two or more devices to
19:06communicate over one or more networks.
19:09Okay? They are also called network
19:12security protocol.
19:14So, secure data to provide
19:15authentication, data integrity, and data
19:18encryption.
19:20We also have protocols for routing.
19:22It enables routers to exchange route
19:25information,
19:27compare path information, and select the
19:29best path to get into the destination.
19:33Also, we have what's called service
19:35discovery. Used for the automatic
19:38detection of devices or services.
19:46Okay. So, next is the network protocol
19:48functions.
19:49So, network communication protocols are
19:51responsible for a variety of functions
19:54necessary for network communications
19:57between end devices. For example,
20:00in the figure here,
20:03okay? So, how does the computer send a
20:05message across several network devices
20:08to the server?
20:10So, first, there is a need for
20:13addressing.
20:14Addressing,
20:16it is used to identify the sender and
20:19the receiver.
20:21Okay? So, addressing identifies the
20:23sender and the intended receiver of the
20:26message using a defined addressing
20:29scheme.
20:31Example of protocols that provide
20:32addressing includes
20:34Ethernet. Ethernet is the protocol of
20:37the local area network.
20:38And we have different varieties for it.
20:41Okay?
20:42So, Ethernet is running at 10 Mbps. Fast
20:46Ethernet is running at 100.
20:49You also have gig Ethernet at 1,000. You
20:51have 10G at 10,000, and you have 100G at
20:54100,000.
20:56Okay? So, Ethernet, you also have IPv4
21:00and IPv6. These are examples of
21:04addressing
21:05um function.
21:08Okay? So, next is reliability.
21:12This function provides guaranteed
21:14delivery mechanism in case messages are
21:17lost or corrupted in transit.
21:20So, TCP provides a guaranteed delivery.
21:25Okay?
21:26So, the next one is flow control.
21:29This function ensures that the data at
21:33an efficient rate between two
21:35communicating devices.
21:36TCP provides flow control services. So,
21:40we will be talking about and using these
21:43protocols on the succeeding videos that
21:45we will have.
21:48Okay?
21:48So, next is sequencing.
21:53So, this function uniquely labels each
21:56transmitted segment of data.
21:58The receiving device uses the sequencing
22:01information to reassemble the
22:03information correctly.
22:06This is useful if the data segments are
22:09lost,
22:11okay?
22:12Delayed or received out of order.
22:15So, the TCP provides a sequencing
22:17services.
22:19Okay?
22:20Next, error detection.
22:23This function is used to determine if
22:26data become corrupted during
22:29transmission.
22:30Various protocols that provide error
22:33detection include Ethernet,
22:36IPv4,
22:37IPv6,
22:39and TCP.
22:42Okay? And the last one
22:45is application interface.
22:47This function contains information used
22:50for process-to-process communications
22:54between network applications. So, for
22:56example,
22:57when accessing a web page, HTTP or HTTPS
23:01protocols are used to communicate
23:03between the client and the server web
23:05processes.
23:07Okay?
23:11Next, how about the protocol
23:12interaction?
23:14Okay? A message sent from one computer
23:17network typically requires the use of
23:20several protocol.
23:22So, each one of its own function and
23:25format.
23:26So, the figure here
23:29shows some common network protocols that
23:32are used when a device sends request to
23:34a web server
23:35for its web page.
23:38So, basically, it started with an
23:40Ethernet,
23:41which I defined earlier as the protocol
23:43of the LAN or the local area network.
23:45Okay?
23:46And then it goes to the IP,
23:48delivers messages globally from the
23:50sender to the receiver.
23:53And then next is
23:56a TCP or the transmission control
23:58protocol,
23:59which provides guaranteed delivery,
24:02manages flow control, and manages the
24:05individual conversations.
24:07Okay? And then on top is the HTTP
24:11or the hypertext protocols,
24:15which governs the way a web server and
24:17web client interact. It defines the
24:20content and format. So, basically, this
24:23protocol here
24:25is operating on a different layer.
24:27And we will be talking about the
24:28different layers used
24:31in data communications. Okay? So, these
24:34are the OSI layers, and you've got the
24:37TCP IP model.
24:40All right?
24:44Okay. So, let's talk about the protocol
24:46switch now.
24:50So, in many cases, protocols must be
24:53able to work with other protocols
24:56so that your online experience gives you
24:59everything you need for network
25:01communications. So the protocol suites
25:04are designed to work with each other
25:07seamlessly.
25:08So a protocol suite is a group of
25:10interrelated protocols necessary to
25:12perform a communication function.
25:15One of the best ways to visualize how
25:18the protocols within the suite interact
25:21is to view the indirect interaction as a
25:24stack.
25:25Okay? A protocol stack shows how the
25:29individual protocols within a suite are
25:32implemented.
25:34The protocols are viewed in terms of
25:36layers.
25:38With each higher level service depending
25:40on the functionality defined by the
25:42protocols shown on the lower levels.
25:47Okay? So the lower layers of the stack
25:50are concerned with moving data
25:53from the network and providing services
25:55to the upper layers,
25:57which are focused on the content of the
25:59message being sent.
26:02Okay? So as illustrated on this figure,
26:07we can use layers to describe the
26:09activity occurring face-to-face
26:11communication.
26:13Okay? So at the bottom is the physical
26:16layer.
26:18Where we have two people with voices
26:21saying words.
26:23Okay?
26:24And then in the middle is what you call
26:26the rules layer.
26:28Okay? So that stipulates
26:30the requirements of communications
26:33including a common language.
26:35Okay?
26:37Um
26:38the wait for your turn
26:40and signal when finished.
26:43Okay? At the top is what you call the
26:46content layer.
26:47And this is where the content of the
26:49communication is actually spoken.
26:53All right?
26:57Okay. So, a protocol suite is a set of
27:00protocols that work together to provide
27:03a comprehensive network communication
27:05services.
27:07Since the 1970s, there have been several
27:10different protocol suites. Some
27:12developed by standards organization and
27:15others developed by various vendors.
27:18Okay? So, during the evolution of the
27:20network communications and the internet,
27:24there were several competing protocol
27:26suite as shown in the figure here.
27:28Okay? So, we have the TCP
27:32IP,
27:34the ISO, AppleTalk, and Novell NetWare.
27:37Okay? In the industry nowadays,
27:40we are using the TCP IP model having the
27:43four layers and the ISO model or the OSI
27:46layers having the seven layers.
27:50Okay?
27:54Okay. So, TCP IP protocols are available
27:58for the application, transport, and
28:00internet layers. So, there are no TCP IP
28:04protocols in the network access layers.
28:07The most common network access layer LAN
28:09protocols are the internet
28:12and the WLAN or the wireless LAN.
28:15Okay? So, network access layer protocols
28:19are responsible for delivering the IP
28:21packet
28:22over the physical medium.
28:26Okay?
28:27Now, the figure here
28:29shows the example of the three TCP IP
28:31protocols used to send packets between
28:34the web server or the web browser
28:37of the host and the web server.
28:39So, you've got the HTTP
28:43or the Hypertext Transfer Protocol,
28:45which operates on the application layer.
28:49Okay? So, HTTP, TCP, and IP are TCP/IP
28:53protocols used.
28:57So, at the end of the network access
28:58layer, Ethernet is used
29:01in the example. However,
29:04this could also be a wireless standard
29:06such as WLAN or cellular service.
29:10Okay? So, for now, if you will observe
29:12on this diagram,
29:14each of the protocol here operates on a
29:16different layer.
29:18The Ethernet is operating on the network
29:20access.
29:21The The IP is operating on the internet
29:24layer.
29:25The TCP is operating on the transport
29:27layer, and the HTTP is operating on the
29:29application layer.
29:32So, if you will observe on this diagram,
29:34there are only four layers used.
29:37Okay? And this is a TCP/IP protocol
29:40suite.
29:41All right?
29:45Okay.
29:46So, today, the TCP/IP protocol suite
29:49includes many protocols and continues to
29:52evolve
29:53to support new services. So, some of
29:56more popular ones are shown on the
29:59diagram here.
30:00Okay?
30:02So, these are the protocols used and
30:05supported on the TCP/IP layers.
30:08Okay? So,
30:11on the application layer, we have what
30:13you call
30:15the name system or the DNS.
30:18Okay? So, the DNS or the domain name
30:20system translates domain name such as,
30:24say, cisco.com into an IP address
30:28or facebook.com into a corresponding IP
30:30address.
30:32All right?
30:34So, you also have the host config,
30:37which includes the DHCP version 4,
30:39version 6, and SLAAC.
30:43So, these are the protocols used to
30:45assign an IP addresses on the
30:47workstations.
30:49On email,
30:51you have SMTP, POP, and IMAP.
30:55Okay? SMTP is a single simple mail
30:58transfer protocol.
31:00It enables clients to send email
31:04to email server and enable servers to
31:06send email to other servers.
31:11You also have POP3 or POP3, the post
31:14office protocol version 3.
31:16It enables clients to retrieve email
31:19from a mail server and download the
31:22email to the client's local mail
31:23application.
31:26Next is IMAP.
31:28IMAP is an internet message access
31:31protocol. So, it enables clients to
31:32access email
31:34stored on a mail server as well as
31:36maintaining email on the server.
31:39Okay. So, the next one is a file
31:42transfer.
31:44For file transfer, we are using
31:46protocols like FTP,
31:48SFTP or the SSH file transfer protocol,
31:52and the TFTP or the trivial file
31:54transfer protocol.
31:57Okay?
31:58So, for the FTP, these are set of rules
32:01that enable the user on one host to
32:04access and transfer file to and from
32:07another host over the network.
32:09So, the FTP is reliable,
32:11connection-oriented, and acknowledged
32:13file delivery protocol.
32:16So, the next one is the SFTP.
32:20This is an SSH file transfer protocol,
32:24an extension of the secure shell
32:27protocol.
32:28Okay? So, the SFTP can be used to
32:31establish a secure file transfer session
32:34in which the file transfer is encrypted.
32:38So, SSH is a method for a secure remote
32:41login
32:42that is typically used for accessing the
32:44command line of a device.
32:49Next is TFTP or the Trivial File
32:52Transfer Protocol. So, a simple
32:54connectionless file transfer protocol
32:57with best effort unacknowledged file
33:00delivery. It uses less overhead than
33:03FTP.
33:05All right?
33:06So, next is on the transport layer.
33:10Okay? So, transport layer is basically
33:12divided into two.
33:14You've got connection-oriented and
33:16connectionless.
33:18Okay? So, when you say
33:19connection-oriented,
33:22we're talking about TCP protocols.
33:24Transmission Control Protocol enables
33:27reliable communication
33:29between the process running on a
33:30separate hosts and provides reliable
33:34acknowledge transmission that confirm
33:36successful delivery.
33:39Okay?
33:40So, when you say connectionless or UDP
33:43or the User Datagram Protocol,
33:46this enables a process running on one
33:48host to send packets to a process
33:51running on another host.
33:53Okay? However,
33:55UDP does not confirm successful datagram
33:59transmission.
34:00Okay? So, the only difference is this
34:02one is reliable
34:04Okay? So, for TCP and
34:07not reliable or unreliable for UDP.
34:12Okay?
34:13So, next is the internet layer.
34:17So, for the internet layer,
34:19this is divided into three. You've got
34:20internet protocols,
34:22um messaging and routing protocols.
34:26Okay?
34:27So, for the internet protocol, we have
34:29the
34:31IPv4
34:33which receives message segments from the
34:35transport layer,
34:37packages messages into packets, and
34:40address packets for an end-to-end
34:42delivery
34:43over a network. So, IP before uses a
34:4732-bit IP addresses.
34:50Okay?
34:51So, for IP V6, this is similar to IP
34:54before, it's just that it uses 128-bit
34:58address.
35:00All right?
35:01So, next is the network address
35:03translation. So, NAT or network address
35:06translation translates an IP before
35:08address
35:09from a private network into a globally
35:12unique public IP before addresses.
35:16Okay?
35:17So, you also have messaging, which
35:19includes the ICMP version 4, ICMP
35:22version 6,
35:24and the ICMP V6ND.
35:27Okay?
35:28So, ICMP is the Internet Control Message
35:31Protocol for IP before.
35:34And you also have for IP V6,
35:36and ND is an ICMP version 6 neighbor
35:40discovery,
35:41which includes the four protocol
35:42messages that are used for address
35:45resolution and duplicate address
35:47detection.
35:49Okay?
35:50So, next is routing protocol.
35:55So, for the routing protocols, we have a
35:57popular OSPF, EIGRP, and BGP.
36:02OSPF is an open shortest path first
36:07link state routing protocol that uses a
36:09hierarchical design
36:11based on areas. So, OSPF is an open
36:14standard interior routing protocol.
36:20Okay. So, next is EIGRP.
36:23EIGRP is enhanced interior gateway
36:27routing protocol.
36:29So, this one is an open standard routing
36:32protocol developed by Cisco that uses a
36:35composite metric on bandwidth, delay,
36:37load, and reliability.
36:39Okay?
36:40And the last one is BGP or the border
36:43gateway protocol, an open standard
36:46exterior gateway routing protocol
36:49used between internet service providers
36:51or ISPs.
36:52BGP is also commonly used between ISPs
36:55and their large private clients
36:58to exchange routing information.
37:01All right?
37:03Now, let's talk about the protocols on
37:05the network access layers.
37:07Okay? So, these are divided into the
37:09address resolution and the data link
37:12protocols.
37:13So, under address resolution,
37:16you've got the ARP
37:18or
37:18the address resolution protocol. So,
37:20this provides dynamic address mapping
37:24between an IPv4 and the hardware address
37:26or the MAC address.
37:29Okay?
37:30Now, next is a data link layer protocol.
37:33So, you I guess you are very familiar
37:35now with Ethernet. As what I'm saying
37:37and defining earlier,
37:38Ethernet is a protocol of the local area
37:40network.
37:42Okay? It defines the rules for wiring
37:44and signaling standards on the network
37:46access layer.
37:48And the last one is the wireless LAN
37:51or the wireless local area network.
37:53It defines the rules for wireless
37:55signaling across a 2.4 and 5 GHz radio
37:58frequencies.
38:01Okay?
38:02So,
38:03this is for TCP/IP. This is an open
38:06standard protocol suite that is freely
38:09available to public and can be used by
38:11any vendor.
38:16Okay. So, how about the TCP
38:18communication process?
38:21So, for instance, we have a web server
38:23here and you've got a web client.
38:26So, a web server encapsulating and
38:29sending a web page to a client.
38:32Okay?
38:33And a client de-encapsulate the web page
38:37for the web browser. So, basically this
38:41is our PDU here.
38:43Okay?
38:44So, PDU uh
38:46PDU pertains to the data format on a
38:49specific layer.
38:50Okay?
38:51On an Ethernet or layer two, we call it
38:54frame or Ethernet frame.
38:56Okay?
38:57On layer three,
38:59we call it IP or IP packet.
39:02Okay?
39:03On layer four,
39:05you you you call it TCP segment.
39:08Okay?
39:09And on layer seven,
39:11Okay, so you've got a user data.
39:14Okay? So, basically if we're talking
39:16about the TCP/IP communication process,
39:18this is uh layer one, Ethernet, network
39:22access.
39:23IP is the internet layer.
39:27Okay?
39:28TCP is
39:31uh the transport layer.
39:34And data is the application layer.
39:40All right.
39:41Now, let's talk about standards
39:44organization.
39:47Okay? So, when buying uh new tires for a
39:51car, there are many manufacturers you
39:53might choose. So, each of them will have
39:55at least one type of tire that fits to
39:58your car.
39:59Okay? That is because the automotive
40:01industry uses standards when they make
40:04cars.
40:06It is the same with protocols. So,
40:07because there are many different
40:09manufacturers of network components,
40:12they must all use the same standards. In
40:15networking, standards are developed by
40:18international standard organizations.
40:21Okay? So, open standards encourage
40:24interoperability, competition, and
40:27innovation.
40:28They also guarantee that the product of
40:32no single company can monopolize the
40:34market
40:35and have an unfair advantage over its
40:37competition.
40:39So, a good example is this: When
40:41purchasing a wireless router or router
40:44for the home,
40:46there are many different choices
40:47available. Okay? So, from a variety of
40:50vendors, all of which incorporate
40:52standard protocols such as IPV4,
40:54IPV6, DHCP, Slack, Ethernet, and
40:58wireless.
40:59Okay? So, this open standard allow a
41:02client running the Apple OS X operating
41:06system to download a webpage
41:08from a web server running the Linux
41:10operating systems.
41:12Okay? So, this is because both operating
41:16systems implemented
41:18the open standard protocols such as
41:20those of the TCP/IP protocol suite.
41:25Okay?
41:26So, standards organizations are usually
41:28vendor neutral.
41:30Nonprofit organizations established to
41:32develop and promote the concept of open
41:36standards.
41:37Okay? So, these organizations are
41:40important in maintaining an open
41:42internet with freely accessible
41:44specifications
41:45and protocols that can be implemented by
41:48any vendor.
41:50Okay? So, a standards organization may
41:54draft a set of rules entirely on its
41:56own.
41:57In other cases,
41:59may select a proprietary protocol on the
42:02basis of the standard.
42:04If a proprietary protocol is used,
42:07it usually involves the vendor who
42:09created the protocol.
42:11Okay? So, these are the open standards.
42:15If you can name them,
42:17okay? This is IEEE.
42:21The Institute of Electrical and
42:23Electronics Engineers.
42:25You've got the IANA or the Internet
42:27Assigned Numbers Authority. So, if you
42:30want to have a registered IP address,
42:32then you go to IANA.
42:34Okay? You also have the IETF or the
42:36Internet Engineering Task Force.
42:39Okay? ICANN, the Internet Corporation
42:43for Assigned Names and Numbers.
42:46The ITU or the International Trade Union
42:49and the TIA or the Telecommunication
42:52Industry Alliances. So, these are
42:55organizations
42:56that is responsible for having a
42:59standards.
43:01Okay?
43:04Okay, so various organizations have
43:06different responsibilities for promoting
43:08and creating standards for the Internet
43:10and TCP/IP protocol.
43:13So, the figure displays standard
43:16organizations involved with the
43:17development
43:19and support for the Internet.
43:22So,
43:23ISOC or the Internet Society, this is an
43:26organization with free membership. Okay?
43:28So, if I were you, I would register with
43:31ISOC. So, this is an open
43:35uh organization. Okay? So, with free
43:39membership. Okay? ISOC or the Internet
43:41Society.
43:42Now, under this ISOC, you've got the IAB
43:45or the Internet Architecture Board.
43:47And then in there, you've got the IETF,
43:50the Engineering Task Force.
43:53And you've got the IRTF, which is
43:55responsible for the researches.
43:58Okay?
44:03So, for the Internet standards, so
44:06you've got IANA, so registered IP
44:08addresses.
44:10IP addresses use is regulated by IANA.
44:13So, together with the domain names
44:15and the use of this port numbers, TCP
44:18and UDP port numbers.
44:21Okay? So, ICANN coordinates IP address
44:25allocation, the management of domain
44:27names, and assignment
44:29of other information. While IANA
44:31oversees and manages IP addresses
44:33allocation, domain name management, and
44:36protocol identifiers for ICANN. So, they
44:38work hand in hand to all to have an
44:41internet standards.
44:44Okay.
44:46So, you also have this IEEE, which I
44:49defined earlier. Okay? So,
44:53let's move on to the next one.
44:57Okay, so let's talk about the reference
44:59models now.
45:06Okay. So, you cannot actually watch a
45:09real packets across a real network.
45:12So, the way you can watch the components
45:14of a car being put together
45:17on an assembly line.
45:19So,
45:21it helps to have a way of thinking
45:24about a network so that you can imagine
45:26what is happening.
45:28So, a model is useful in this situation.
45:32Okay? So, complex concepts such as
45:36how a network operates can be difficult
45:38to explain and understand. So, for this
45:41reason, a layered model is used to
45:44modularize the operations of a network
45:47into a manageable layers.
45:50So, there are benefits of using a
45:52layered model to describe network
45:54protocols and operations.
45:56So, assisting in protocol design because
45:59operations or protocols that operate at
46:02a specific layer have defined
46:04information that they can act upon
46:07and define interface
46:09to that layers above and below.
46:13So, fostering competition because
46:15products from different vendors can work
46:17together.
46:18Preventing technology or capability
46:20changes in one layer from affecting
46:23other layers above and below.
46:26Providing a common language to describe
46:28networking function and capabilities.
46:31Now, as shown here in the figure, there
46:34are two layered models that are used to
46:36describe network operations.
46:38So, you've got the Open System
46:40Interconnection Model or Reference Model
46:42and you've got a TCP/IP Reference Model.
46:46Okay? So, OSI is from the ISO and TCP/IP
46:51is from the IEEE.
46:55So, at the top of the image, there are
46:59two LANs connected via
47:01wide area network.
47:03Okay? So, a networking model is used
47:07only to represent the network operation.
47:10So, the model is not the actual network.
47:13Underneath are the TCP/IP layers and
47:17protocols.
47:18Now, there are seven layers of the OSI
47:21model from top to bottom and their
47:23associated protocols.
47:25So, you've got application,
47:27presentation, session, transport,
47:31network, data link, and physical layer.
47:34Okay?
47:35Now, for the TCP/IP model, so there are
47:38four layers.
47:40Okay? So, from the top, you've got the
47:42applications,
47:44you've got the transport, the internet,
47:46and
47:47the network access.
47:50Okay?
47:50So,
47:52basically,
47:54the OSI model is a detailed
47:58um model
48:00for
48:01uh computer science, IT.
48:04Okay? So, they use OSI model. But, for
48:07engineers,
48:09we use the TCP/IP model. So, but then
48:11they are the same.
48:13Okay? So, TCP/IP model is more generic,
48:18whereas the OSI model is more specific.
48:22Okay?
48:27Next,
48:29let's get into the detail of the OSI
48:32reference model.
48:33Okay? So, the OSI reference model
48:36provides an extensive list of functions
48:39and services that can occur at each
48:41layer.
48:42So, this type of model provides
48:44consistency
48:46within all types of network protocols
48:48and services by describing what must be
48:51done at a particular layer.
48:54So, but not prescribing
48:56how it should be accomplished.
48:59Okay?
48:59So, it also describes the interaction of
49:01each layer with the layers directly
49:03above and below.
49:05So, the TCP/IP protocol discusses
49:09or discussed in this video lecture
49:11are structured around both the OSI and
49:14the TCP/IP models.
49:16So, the table shows the detail about
49:19each layer of the OSI model, the
49:21functionality of each layer, and the
49:23relationship between layers will become
49:25more evident throughout the course as
49:28the protocols are discussed in more
49:30detail.
49:31Okay?
49:32So, basically, you've got the
49:34application contains protocols
49:38used for process-to-process
49:39communications.
49:41You also have the presentation, which
49:42provides a common representation of data
49:45transferred between application layer
49:47services.
49:48The session layer provides services
49:51to the presentation layer and to manage
49:54data exchange.
49:56The transport layer defines services to
49:58segment, transfer, and reassemble the
50:01data for individual communications.
50:04The network layer provides services to
50:06exchange the individual pieces of data
50:09over the network
50:10and prescribes a method for exchanging
50:13data frames over a common media for the
50:15data link layer.
50:17So, basically, your physical layer
50:19describes the means to activate,
50:21maintain, and deactivate physical
50:23connections.
50:24Okay? Now, talking about the protocol
50:27data unit, okay? On the physical layer,
50:30the data is represented in terms of
50:32bits.
50:34All right? On the data link layer, your
50:37data is represented in terms of frames.
50:39On the network layer, we call it
50:41packets.
50:42On the transport layer, we call it
50:45segment or datagram.
50:47And then on the on the application
50:49layer, basically,
50:50your data is
50:53in a form of applications that is
50:56readable and visible to the users.
50:59All right?
51:03Now, on the TCP/IP reference model,
51:06the TCP/IP protocol model for the
51:08internetwork communication was created
51:11in the early 1970s
51:13and is sometimes referred to as the
51:14internet model.
51:16Okay? So, this type of model closely
51:19matches the structure of a particular
51:21protocol suite.
51:23So, the TCP/IP model is a protocol model
51:26because it describes the function that
51:29occur at each layer of the protocols
51:32within the TCP/IP suite.
51:34So, the TCP/IP is also used as a
51:37reference model.
51:39Okay? Now,
51:42the distinct
51:44um Mhm, components of the TCP/IP and
51:49the OSI model is basically
51:53having seven and four respectively.
51:57Okay?
51:59So, on the TCP/IP reference model, so it
52:02has been
52:04four layers where the OSI layer is using
52:07the seven layers. Okay? So, combining
52:10the physical and the data link layer
52:12into network access,
52:14there is no network layer on the TCP/IP
52:17reference model. We call it internet
52:19layer.
52:21Okay? So, transport has the same name
52:24and application basically is a split
52:26into
52:27application layer, presentation layer,
52:29and session layer.
52:33Okay?
52:34So, here's the comparison of the two
52:37models.
52:38So, the protocols that make up the
52:39TCP/IP protocol suite can also be
52:41described in terms of the OSI reference
52:44model.
52:46So, in the OSI reference model, the
52:49network access and the application layer
52:52of the TCP/IP model are further divided
52:54to describe discrete functions that must
52:57occur at these layers.
53:00So, at the network access layer, the
53:03TCP/IP protocol suite does not specify
53:06which protocol to use when transmitting
53:10over the physical medium.
53:12It only describes the half of
53:15from the internet layer to the physical
53:17network protocols.
53:19Whereas the OSI layers one and two
53:22discusses necessary procedures to access
53:25the media
53:26and the physical means to send data over
53:29the network.
53:31Okay?
53:34Next,
53:35let's talk about data encapsulation now.
53:40Okay. So, knowing the reference model
53:45and the TCP/IP protocol model will come
53:48in handy when you learn about how data
53:51is encapsulated as it moves across a
53:54network.
53:55So, it is not as simple as the physical
53:58letter being sent through the mail
54:00system.
54:01Okay? So, in theory
54:04a single communication such as a video
54:06or an email message with many large
54:09attachments could be sent the network
54:11from the source to destination as one
54:14massive uninterrupted stream of bits.
54:19However
54:20this would create problems for other
54:23devices needing to use the same
54:25communication channels or links.
54:27This large streams of data would result
54:30in a significant delays. So, further
54:33if any link in the interconnected
54:36network infrastructure failed during the
54:38transmission
54:40the complete message would be lost and
54:43would have to be retransmitted in full.
54:46So, a better approach is to divide the
54:48data into smaller pieces. We call it
54:50segments.
54:51Okay? So, segmentation is the process of
54:54dividing streams of data into smaller
54:56units for transmission over the network.
55:01So, segmentation is necessary because
55:04data networks use TCP/IP protocol suite
55:07send data in individual IP packets.
55:11So, each packet is sent separately.
55:14Similar to sending a long letter as
55:17series of individual postcards.
55:20Okay? Or packets containing segments for
55:23the same destination can be sent over
55:26different paths.
55:28So, this leads to segmenting message
55:30having the two primary benefits.
55:33Okay? What are these?
55:35Increased speed and increases
55:38efficiency.
55:39Okay? So, because a large data stream is
55:42segmented into packets, large amounts of
55:45data can be sent over the network
55:47without trying a communications link.
55:51Okay? So, this allows many different
55:54conversations to be interleaved on the
55:57network called multiplexing.
56:01Next is increased efficiency.
56:04If a simple segment or single segment is
56:07fails to reach its destination due to
56:10failure in the network or network
56:12congestion,
56:13only that segment needs to be
56:15retransmitted instead of resending the
56:17entire data stream.
56:18Okay, so this is the reason why we need
56:21to segment the messages.
56:24Okay?
56:25Now, the challenge here
56:28is
56:30using segmentation and multiplexing to
56:32transmit messages across the network
56:35is the level of complexity that is added
56:38to the process. Now, imagine if you had
56:41to send 100-page letter,
56:44but each envelope could only hold one
56:47page.
56:48Okay? So, therefore, 100 envelopes would
56:51be required and each envelope would need
56:54to be addressed individually.
56:57Okay?
56:59Now,
57:01having said that, it is possible that
57:04the 100-page letter in 100 different
57:07envelopes arrives out of order,
57:09right?
57:10So, consequently,
57:12the information in the envelope would
57:15need to include a sequence number to
57:16ensure that the receiver could
57:19reassemble the pages
57:21in the proper order.
57:23So, in network communications, each
57:25segment of the message must go through a
57:29similar process to ensure that it gets
57:31the correct destination. And
57:34it can be reassembled into a content of
57:37the original messages.
57:40Okay? So, TCP is responsible for
57:42sequencing and individual or sequencing
57:45the individual
57:47segments.
57:48Okay? So, remember this. TCP is
57:51responsible for sequencing the
57:53individual segments because TCP is said
57:56to be reliable.
57:58All right?
58:01Next,
58:02let's talk about protocol data units.
58:04You
58:05you hear me saying PDUs.
58:08Okay? So, PDUs is basically the data
58:11representation on each of the layer.
58:14And protocol data units,
58:17okay? On the application layer, we
58:19simply call it data.
58:21And the concept is the data needs to be
58:24segmented
58:25before forwarding it to the destination.
58:28Okay?
58:29Now, each segment of the data is having
58:32their transport header.
58:34Now, what is the content of the
58:35transport header?
58:36Well, basically the the one of the
58:38important component of the transport
58:40header is the port address.
58:43So, port address pertains to the
58:45application's address.
58:47Okay? And when encapsulated, we call it
58:50segment.
58:52Okay?
58:53Now, that segment moving further
58:55downward,
58:57once it reaches
58:59the network layer, okay? So, apart from
59:02the transport layer of the front
59:04transport header appended on the
59:06transport layer,
59:07the network layer will append another
59:10network header having the source and
59:12destination IP address.
59:14And when encapsulated, we call it
59:16packets.
59:18Okay?
59:19Now, reaching on the second layer,
59:23so, this is now what you call frame.
59:26And the frame has the frame header
59:30having the source and destination MAC
59:32address. And of course, it is it has a
59:34trailer.
59:37Okay?
59:38So, you have to remember this protocol
59:40data unit
59:41on each of the layers.
59:47Okay. So, when messages are being sent
59:50on a network, then capsulation process
59:52works from top to bottom.
59:55Okay?
59:56And at each layer, the upper layer
59:59information is considered data within
1:00:01the encapsulated protocol. So, for
1:00:03example,
1:00:04the TCP segment is considered within the
1:00:07IP packet.
1:00:09Okay?
1:00:11Now, in here,
1:00:13if you'll observe here,
1:00:14your data is there.
1:00:16Okay? And it has this header, TCP, IP,
1:00:19and the Ethernet. So, basically,
1:00:22this is now your data transmitted from
1:00:24the web server to the web client and
1:00:26vice versa.
1:00:28Okay?
1:00:32Now, this process is reversed at the
1:00:34receiving host and is known as
1:00:37de-encapsulation.
1:00:39Okay? So, de-encapsulation
1:00:42is the process used by receiving device
1:00:45to remove one
1:00:48or more of the protocol headers.
1:00:50The data is de-encapsulated as it moves
1:00:53up stack towards the
1:00:56user or the end user's application.
1:00:59Okay?
1:01:00So, the each of this header will be
1:01:02removed until it reaches the application
1:01:05layer for presentation to the end users.
1:01:09Okay?
1:01:12Next,
1:01:13data access.
1:01:15Okay?
1:01:19As you learned,
1:01:20okay, it is necessary to segment
1:01:22messages in a network, but those
1:01:24segmented messages will not go anywhere
1:01:27if they are not addressed properly.
1:01:30Okay? So, this topic gives you an
1:01:33overview of network addresses. So, you
1:01:36will also get a chance to use
1:01:39other tools, now. If you are using
1:01:41Wireshark, okay? Which will help you
1:01:44view the network traffic.
1:01:47Now, the network and data link layers
1:01:49are responsible for delivering the data
1:01:52from the source device to a destination
1:01:54device.
1:01:55Okay?
1:01:56So, in here
1:01:59you've got the
1:02:02network layer source and destination
1:02:04address. You've got the data link data
1:02:07link layer source and destination
1:02:08addresses.
1:02:10Okay?
1:02:11So, basically
1:02:14on the physical layer your data is dealt
1:02:18with timing and synchronization of bits.
1:02:21On the data link layer, you've got the
1:02:23destination
1:02:25and source physical address. When you
1:02:27say physical address, this pertains to
1:02:29the MAC address of your computer.
1:02:32Okay?
1:02:34Your network
1:02:36is having the source and
1:02:39destination logical network address. So,
1:02:42when you say logical network address,
1:02:43this pertains to the IP address of your
1:02:46computer.
1:02:47Okay? Your transport
1:02:50has this destination and source
1:02:52process number or port addresses. This
1:02:55pertains to the addresses of the
1:02:57applications residing within your
1:03:00computer.
1:03:01So, basically, your PDU comprises of
1:03:04several addresses once it traverses from
1:03:07the source to destination or while in
1:03:08transit.
1:03:10Okay?
1:03:15Okay, so, layer three logical address.
1:03:19An IP address is the network layer or
1:03:22layer three logical address used to
1:03:25deliver the IP packet from the original
1:03:28source to the final destination.
1:03:31Okay, as shown on this diagram here.
1:03:33Okay? So, your IP packet traverses over
1:03:36the network. Okay, so from one router to
1:03:39another and so on. And that is in a form
1:03:41of a PDU called packet.
1:03:45Okay? So, the source IP address,
1:03:48the IP address of the sending device,
1:03:51original source of the packet. The
1:03:54destination IP address is the IP address
1:03:56of the receiving device, the final
1:03:58destination of the IP packet.
1:04:01Okay? So, the IP address doesn't change
1:04:05while your data moves from the source to
1:04:08destination.
1:04:09Okay? It is fixed.
1:04:12Okay?
1:04:13Next.
1:04:16Now, your layer three logical address
1:04:18comprises of the network portion and the
1:04:22host portion.
1:04:23Okay? So, basically,
1:04:26when you say network portion, the
1:04:29leftmost part of the address that
1:04:32indicates the network in which the
1:04:34address or the IP address is a member.
1:04:36So, all devices on the same network will
1:04:39have the same network portion of the
1:04:42address. So, we will be dealing with
1:04:44this on IP addressing. So, for now, you
1:04:48just have to know that your IP address
1:04:49are divided into two. You've got the
1:04:51network portion and the host portion.
1:04:54Okay? So, the host portion is the
1:04:57remaining part of the address that
1:04:59identifies the specific device on the
1:05:01network. So, this portion is unique for
1:05:04each of the device or interface on the
1:05:07network.
1:05:09Okay? So, we will be talking about this
1:05:11once we get onto the IP addressing. But,
1:05:14to give you an overview,
1:05:16okay? So,
1:05:19the network portion for the source IP
1:05:22address is 192.168.1.
1:05:26This is what you call a network portion.
1:05:29The host portion is 110.
1:05:32Okay?
1:05:33Now, if we're talking about 172.16,
1:05:36okay? So, this will depend or vary on
1:05:39the subnet mask. So, if we are using
1:05:42the classful addressing,
1:05:46this is class C and this one here is
1:05:48class B. So, therefore, the destination
1:05:50IP address 172.16
1:05:53pertains to the network portion and 1.99
1:05:57is the host portion. So, as what I'm
1:05:59saying, we will be dealing about this
1:06:02more on the IP addressing on the
1:06:04succeeding
1:06:05video lecture.
1:06:07Okay?
1:06:08So, for now, let's move on to the next
1:06:10slide.
1:06:12Okay.
1:06:13So, devices on the same network.
1:06:16In this example, we have a computer
1:06:18client
1:06:20Okay? PC1
1:06:22communicating with an FTP server on the
1:06:25same IP network.
1:06:27Okay?
1:06:28So, the source IPV4 address
1:06:32of the sending device client is
1:06:34192.168.1.110.
1:06:37So, this is the IP address of this
1:06:39computer sending and the destination IP
1:06:42address
1:06:44is of course the IP address of the FTP
1:06:46server
1:06:47and that is on 192.168.1.9.
1:06:50So, they are on the same network, so
1:06:52that means 192.168.1
1:06:55is the network portion.
1:06:57Same thing with this.
1:06:59.110 and .9 are the host portion.
1:07:05Okay? So, when we say that they are on
1:07:07the same network,
1:07:09okay, so the first three octets in this
1:07:13case are the same.
1:07:14They only differ on the fourth octet. We
1:07:16call this octet.
1:07:18Okay?
1:07:19So, 110 and 9, so they are different
1:07:23components or different computers, but
1:07:26they belong to the same network,
1:07:28192.168.1.0.
1:07:31Okay?
1:07:35Next.
1:07:38Data access rule in the data link layer
1:07:41address, same IP network. Okay? So,
1:07:43earlier on, we used an IP address. Now,
1:07:47in here, we use MAC addresses now.
1:07:50Okay? When the sender and the receiver
1:07:53of the IP packet are on the same
1:07:54network, the data link frame is sent
1:07:57directly to the receiving device.
1:08:00On an Ethernet network, the data link
1:08:02addresses are known as the Ethernet
1:08:05media access control or MAC address, or
1:08:10also known as the physical address. So,
1:08:13this A A A A A here and this C here, a
1:08:17series of C, are what you call MAC
1:08:19address.
1:08:21Okay? So, MAC addresses are physically
1:08:23embedded onto the Ethernet NIC.
1:08:27So, the source MAC address,
1:08:30this is the data link address or the
1:08:32Ethernet MAC address
1:08:34of the device that sends the data
1:08:37with an encapsulated IP packet. So, the
1:08:40MAC address of the Ethernet for PC1 is a
1:08:44series of A here.
1:08:46Okay? So, this uses a hexadecimal
1:08:49notation. And the destination MAC
1:08:51address of the FTP server are all C
1:08:55here, again, in hexadecimal notation.
1:08:58Okay? So, the frame with encapsulated IP
1:09:02packet can be transmitted from PC1
1:09:05directly to the FTP server.
1:09:08Okay? That's the communication
1:09:11on the data link layer.
1:09:13Okay? On the data link layer, your
1:09:15devices uses MAC address. On the network
1:09:18layer, your devices uses an IP address.
1:09:25Okay. So, how about devices on a remote
1:09:27network?
1:09:29Okay?
1:09:30So,
1:09:32for instance,
1:09:33okay? We have here
1:09:35a source
1:09:37which is located on 192.168.1.10.
1:09:40And our destination, for instance, is a
1:09:42web server at 172.16.1.199.
1:09:46Okay? So, the consideration here is a
1:09:49/24.
1:09:51Okay? So, having a /24, that means the
1:09:55subnet mask is 255.255.255.0.
1:09:59That means the first three octet
1:10:03corresponds to the network ID.
1:10:06And
1:10:08the last octet corresponds to the host.
1:10:10So, you've got the network the network
1:10:12portion, and you've got the host portion
1:10:14here.
1:10:15Okay?
1:10:19So, what happens when the actual
1:10:21ultimate destination is not on the same
1:10:23LAN and it is remote? So, basically, if
1:10:27your computer is communicating on a
1:10:29remote
1:10:31device,
1:10:32okay? So, your switch will basically
1:10:36examine
1:10:38the packet,
1:10:40and if it is not on the same network, it
1:10:42will be forwarded onto the default
1:10:44gateway.
1:10:46Okay? That's the sense of the default
1:10:48gateway. Whenever we communicate with
1:10:50the other devices or other computers on
1:10:52the other network,
1:10:54your default gateway is being used.
1:10:57Okay?
1:10:58Now, what happens when PC1 tries to
1:11:00reach the web server? So, it's what I'm
1:11:02saying, if the destination is not on the
1:11:04same network, okay, so therefore it will
1:11:06be forwarded onto the default gateway.
1:11:10Okay?
1:11:11And therefore,
1:11:13your data will communicate on the
1:11:16network layer, okay? And then once it
1:11:19reaches on the destination, it will go
1:11:22back to layer two and then forwarding it
1:11:25to the web server using the
1:11:28MAC address.
1:11:30Okay? So, IP addresses are being used by
1:11:34routers.
1:11:36Okay? Whereas,
1:11:38MAC addresses are being used by
1:11:39switches. So, how come the switch can
1:11:42communicate with the router? So,
1:11:44remember that we have the protocol
1:11:46called ARP. Okay? The ARP is a protocol
1:11:50responsible for mapping the MAC address
1:11:53into its corresponding IP address.
1:11:55Okay? So, that makes sense here, but
1:11:58we'll get into the details of moving
1:12:01data from the source to destination as
1:12:03we progress as we the course.
1:12:05So, for now,
1:12:06let's put it that way.
1:12:08MAC address is on the layer two and it
1:12:11is usually used by the switch
1:12:13and your IP address or layer two
1:12:15addresses are usually being used by the
1:12:17routers.
1:12:19All right?
1:12:22Okay, so what is the role of the network
1:12:24layer addresses? So, when the sender of
1:12:26the packet is on a different network
1:12:29from the receiver, the source and
1:12:31destination IP address will represent
1:12:33hosts on a different network.
1:12:36So, this will indicate or this will be
1:12:38indicated by the network portion of the
1:12:41address.
1:12:43Okay? And the destination host.
1:12:46So, in this example, the source IP
1:12:49address is to
1:12:52Okay?
1:12:53This is the source. And the destination,
1:12:55take a look at it. It's 172.16.1.
1:12:5899, which is located on the other
1:13:01network.
1:13:03Okay?
1:13:04So, notice that in the figure, that the
1:13:06network portion of the source IPV4
1:13:09address and the destination address are
1:13:12on different networks. Okay? So, in here
1:13:17you've got 192.168.1.10.
1:13:20And in there, you've got 172.16.1.99.
1:13:23So, they are on a different network.
1:13:26All right?
1:13:28Next, the role of the data link layer
1:13:32Okay? And our data link layer addresses
1:13:34in a different IP network.
1:13:36So, when the receiver or when the sender
1:13:39and the receiver
1:13:40of the IP packet are on different
1:13:42network, the Ethernet data link frame
1:13:44cannot be sent directly to the
1:13:46destination because the host is not
1:13:49directly reachable.
1:13:51Okay?
1:13:51So, the Ethernet frame must be sent to
1:13:55another device known as the router or
1:13:58the default gateway, which I mentioned
1:14:00earlier.
1:14:01Okay? So, in our example, the default
1:14:03gateway of
1:14:06PC1 is the interface of R1, which is
1:14:09192.168.1.1.
1:14:11So, again, the switch should know that
1:14:14the destination is not on the same
1:14:16network.
1:14:17Okay? So, therefore, it will be
1:14:19forwarded on to the R1's default gateway
1:14:22so that it can be forwarded by R1 to
1:14:25another directly connected routers to it
1:14:27until it reaches the destination.
1:14:31All right?
1:14:35Okay.
1:14:36So, the MAC address
1:14:39in this case,
1:14:40the source MAC address is AAA, and then
1:14:43the destination's MAC address is
1:14:4511 11 11 11. Now,
1:14:49as your data moves from the source to
1:14:51destination,
1:14:52the IP address is fixed. The source IP
1:14:56address is fixed, the destination IP
1:14:58address is fixed.
1:14:59Okay? But, it is different in the case
1:15:02of the data link layer or the MAC MAC
1:15:05addresses.
1:15:07Okay? So, basically, every hops,
1:15:10your MAC address changes. Okay? So, for
1:15:13instance, on this hop,
1:15:15from PC1 going to the default gateway,
1:15:18okay? The source MAC address is the MAC
1:15:21address of PC1, and the destination MAC
1:15:24address is the MAC address of the R1's
1:15:28uh interface. This interface
1:15:30specifically.
1:15:32Okay?
1:15:33So, once it moves the data from the
1:15:35source to another hop,
1:15:38your MAC address source and destination
1:15:40changes. So, basically, if we already
1:15:43have reached this area here from R2
1:15:45going to the web server,
1:15:47the source MAC address is
1:15:50the MAC address of this router here,
1:15:53which in this case is 22 22 22 22 22 22,
1:15:57okay? And the destination MAC address is
1:15:59the ABCDEF 1234 and 56. So, that's how
1:16:04it works.
1:16:05Okay?
1:16:09Next, data link layer addresses. So, the
1:16:12data link layer two physical address has
1:16:15a different role. The purpose of the
1:16:17data link layer address is to deliver
1:16:19the data
1:16:21from one network interface to another
1:16:23network interface on the same network.
1:16:27Okay? That's the use of the MAC address.
1:16:30If the source and destination are on the
1:16:32same network, then we just have to use
1:16:35the MAC address.
1:16:36All right?
1:16:39So, bef- before an IP packet can be sent
1:16:43over a wired or wireless network, it
1:16:45must be encapsulated in a data link
1:16:47frame, so it can be transmitted over the
1:16:49physical
1:16:51medium.
1:16:53Okay?
1:16:54So,
1:16:57next.
1:17:00Okay, so as the packet travels from host
1:17:03to router,
1:17:04router to router, and finally router to
1:17:06host,
1:17:07at each point along the way, the IP
1:17:10packet is encapsulated in a new data
1:17:12link frame.
1:17:13So, each data link frame contains the
1:17:16source data link address of the NIC card
1:17:21sending the frame and the destination
1:17:23data link address of the NIC card of the
1:17:26receiving frame.
1:17:28Okay? So, that's what I explained
1:17:30earlier.
1:17:31What every hops, your MAC address
1:17:35changes.
1:17:37All right?
1:17:41Okay. So, take a look at here,
1:17:44okay? So, on this area here from the
1:17:48source
1:17:49going to the first router,
1:17:51okay? Your source MAC address is
1:17:54basically the MAC address of the
1:17:56computer,
1:17:57and the destination MAC address is the
1:17:59MAC address of this router's interface
1:18:01connected to
1:18:03uh PC1.
1:18:05This is the first stop. Now, on the next
1:18:06hop,
1:18:07the source MAC address is in here,
1:18:11and the destination MAC address is in
1:18:13there.
1:18:14And on the last hop, source MAC address
1:18:17is on the router, and the destination
1:18:19MAC address is on
1:18:21the server.
1:18:23Okay?
1:18:24So, basically your data has this layer
1:18:28two and layer three
1:18:30headers.
1:18:32So, your layer two header contains the
1:18:34source and destination MAC addresses,
1:18:36and then your layer 3 header contains
1:18:38the source IP address and the
1:18:40destination IP address.
1:18:44Okay?
1:18:46So, as mentioned earlier,
1:18:50notice that the packet is not modified,
1:18:53but the frame is changed. Therefore, the
1:18:56layer 3 IP addressing does not change
1:18:59from segment to segment like the layer 2
1:19:01MAC addressing.
1:19:03So, the layer 2 addressing remains the
1:19:04same since it is global and the ultimate
1:19:08destination is still the web server.
1:19:11Okay? Now, to sum up this um
1:19:14presentation,
1:19:16on this video lecture, we talked about
1:19:19the different
1:19:21uh layers of the OSI model and the
1:19:23TCP/IP model.
1:19:25And we also talked about the PDUs, the
1:19:29protocol data units.
1:19:31Okay? So, for each of the layer,
1:19:33and
1:19:34the difference between MAC address and
1:19:36IP address.
1:19:38Okay? And the transmission of data on
1:19:40the same network and going to a
1:19:42different network.

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