All language subtitles for 3. Network Access

In this section network access and we are gonna define how we can access to a network
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briefly.
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...
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...
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...
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in this lecture
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In this lecture, firstly we are gonna focus on OSI-Layer 1 ; Physical layer. In the seven-layer OSI model of computer
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networking, the physical layer or layer 1 is the first and lowest layer. The physical layer consists
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of the electronic circuit transmission technologies of a network
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It is a fundamental layer underlying the higher level functions in a network.. The physical layer defines
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the means of transmitting raw bits rather than logical data packets over a physical data link connecting network
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nodes. The bit stream may be grouped into code words or symbols and converted to a physical signal
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that is transmitted over a transmission medium. The physical layer provides an electrical, mechanical, and
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procedural interface to the transmission medium
and here are the fundamentals of the physical layer
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We have three medias the first medium is copper cable the second media is fiber optic cable.
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And the third is the wireless media. in a corporate cable media the physical components are maybe a utility
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cable coaxial cable.
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We have some connectors, we have Network Interface Cards, ports, interfaces and etc, in a fiber optic
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cable media.
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We have single multimode fibers, connectors again, Network Interface Cards, interfaces lasers
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and LEDs and photoreceptors.
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And in a wireless media our physical components are maybe access points maybe.
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Again network interface cards which are the wireless network interface cards this time, maybe radios
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bandwidth is the bit-rate of available or consumed information capacity expressed typically
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in metric multiples of bits per second.
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For example An internet connection with a larger bandwidth can move a set amount of data much faster
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than an internet connection with a lower bandwidth.
here as you can see the abbrv. as well.
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If you want to talk about the kilobits per second we're using K.B..
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P.S. If you want to talk about the megabit per second we're using M.B.P.S. If you want to talk
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about gigabit per second we're using the GBPS. let's move forward with the network media. network media
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Network media refers to the communication channels used to interconnect nodes on a computer network
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Typical examples of network media include copper coaxial cable, copper twisted pair cables and optical fiber
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cables used in wired networks, and radio waves used in wireless data communications networks
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Let's go ahead with UTP cable.
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First Unshielded twisted pair (UTP)
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TIPPY is a type of copper cabling used in telephone wiring and the local area networks incited you to
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is a type of copper cabling used in telephone wiring and local area networks (LANs).Inside a
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UTP cable is up to four twisted pairs of copper wires, enclosed in a protective plastic cover,
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with the greater number of pairs corresponding to more bandwidth. The two individual wires in a single
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pair are twisted around each other, and then the pairs are twisted around each other, as well.
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This is done to reduce crosstalk and electromagnetic interference, each of which can degrade network
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performance. Each signal on a twisted pair requires both wires.
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here are the standards when we are using UTP cabling. UTP categories
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are starting with cat one and finishing with the cat 7.
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We have various rates for each categories as you can see for example if you are using cat 1 you can
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use up to one megabit per second.
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But if you're are using cat 7 cable you can use up to 10 gigabit per second.
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data rate
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The maximum lengths are almost the same as you can see it's almost 100 meters.
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And the applications that are using the different categories are for example Cat 1 is used in old telephone
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cables cat 2 is used in the token ring networks for for example Cat 6 is being used in gigabit
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and ten gigabit networks.
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Let's go ahead with UTP connectors. connector is the part of a cable that plugs into a port or
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interface to connect one device to another.
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Most connectors are either male (containing one or more exposed pins) or female (containing holes in which
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or female (containing holes in which the male connector can be inserted).
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The RJ-45 connector is an eight-wire connector that is commonly used to connect networking devices such
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as switches , routers or PCs to a local area network (LAN).
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This connector is used with Cat-5 or Cat-6 cables commonly and consists of 8 pins.
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Here is the male connector.
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And here as you can see this is a female connector.
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Let's go with UTPcable types. T568A and T568B
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are the two color codes used for wiring eight-position RJ45 modular plugs
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The only difference between the two color codes is that the orange and green pairs are interchanged.
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Straight-through cable is a type of CAT5 which the RJ-45 connectors at each end
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have the same pin out. (color code use on both ends are the same)Straight-Through cable is also referred to
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as a “patch cable.” Straight-through cable is used to connect computers and other end user devices to
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networking devices such as hubs & switches.
A Crossover cable is a type of CAT
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where one end is T568A configuration and the other as T568B configuration.
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Pin 1 is crossed with Pin 3 and Pin 2 is crossed with Pin 6.Crossover cable is used to connect two
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same devices (for example routers) together
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here as you can see the T 5 6 8 a pinout and as you can see
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we have 8 pins in here.
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If are using this pin out with the five six eight A in the first pin you're using white green cable.
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In the second you're using green third white orange blue white blue orange white brown and brown.
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If you're using five six eight b in the first pin ur using white orange cable this time.
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Then orange white green blue white blue green and white brown and they're brown.
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Let's go ahead with the Shielded twisted pair . Shielded twisted pair is a special kind
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of copper cable used in telephone or LAN systems.
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An outer covering or shield is added to the ordinary twisted pair wires prevent
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electromagnetic interference and the shield functions as a ground.
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Coaxial cable is a type of copper cable specially built with a metal shield and other components
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engineered to block signal interference.
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It is primarily used by cable TV companies to connect their satellite antenna facilities to customer
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homes and businesses. Some homes and offices use coaxial cable, too, but
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its widespread use as an Ethernet connectivity medium in enterprises and data centers has
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been supplanted by the deployment of twisted pair cabling.
A fiber optic cable is a network cable that contains
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strands of glass fibers inside an insulated casing.
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They're designed for long distance,
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very high performance data networking and telecommunications.Compared to wired cables, fiber optic cables
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provides higher bandwidth and can transmit data over longer distances.
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The two primary types of fiber cables are called single mode and multi mode fiber.
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Single mode fiber uses very thin glass strands and a laser to generate light
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while multi mode fibers use LEDs. Single mode fiber networks often use Wave Division Multiplexing (WDM) techniques techniques
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to increase the amount of data traffic that can be sent across the strand.
as I told you multimode fibers
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use LED as light source and provide multiple paths for light.
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If you compare with the single mode they provide lowe bw and higher attenuation.
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And here are the connection types that we can use in the fiber optic cables.
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...
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let's compare the fiber optic with the copper cable.
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As you can see in here the first let's take a look to the distance. optical fiber can provide communication
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up to 12 miles while copper provides communication up to 300 feeets
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The weight is almost 4 LBS is in here while the copper is thirty nine.
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The maximum bandwidth that optical fiber can provide 69 tbps per second which is much higher than
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the 10 gigabit per second.
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but optical fiber is hard to tap and easy to alarm but copper emits the EMI electromagnetic interface.
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Let's go ahead with the wireless communication .wireless communication is the transfer of information
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between two or more points that are not connected by a cable.
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The most common wireless technologies use radio waves. With radio waves speeds may be low as 3 mbps
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per seconds.
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for bluetooth, or may be really high up to 1 gbps for Wi-MAX
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and let's take a look to 802.11 wifi standards.
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Standards are Set of media access control (MAC) and physical layer (PHY) specifications for implementing wireless
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local area network communication. In the chart you
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can see the evolution of the standards. In the first standard 802.11, maximum data rate is
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2mbps,
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but in 802.11ac
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max data rate is 7gbps.
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...
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And here you can see the frequency bands , bandwidths modulation types and advanced antenna technologies
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for each standard as well. let's go with the datalink layer protocols and media access control.
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The data link layer or layer 2 is the second layer of the seven-layer OSI model of computer
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networking and provides access to media via mac addresses.
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Guys This layer is the protocol layer that transfers data between adjacent network nodes. The data link layer
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provides the functional and procedural means to transfer data between network entities and might provide the
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means to detect and possibly correct errors that may occur in the physical layer.
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Protocols like Ethernet, PPP and HDLC operate at this layer.
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The most important standards used in Layer-2 are, Ethernet
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bluetooth which are created by IEEE and ADSL and MPLS which are created
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by ITU-T and we have HDLC and MAC which are created by ISO and we have FDDI which is created by ANSI
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see these are the most important ones.
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The data link layer functionality is usually split it into 2 logical sub-layers as you can see we have logically
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control and media access control. the upper sub-layer, termed as LLC, that interacts
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with the network layer above and the lower sub-layer, termed as MAC media access control is the one that
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interacts with the physical layer below.
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While LLC is responsible for handling multiple Layer3 protocols (multiplexing/de-multiplexing) and link services
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like reliability and flow control, the MAC is responsible for framing
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and the media access control for broadcast media
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Ethernet is the most widely installed local area network (LAN) technology. Ethernet is a protocol in the describing
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how networked devices can format data for transmission to other network devices on the same network segment, and
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how to put that data out of network connection.
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Ethernet defines two units of transmission, packet and frame.
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The frame includes not just the "payload" of data being transmitted but also addressing information
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identifying the physical "Media Access Control" (MAC) addresses of both sender and receiver, VLAN tagging
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and quality of service information, and error-correction information to detect problems in
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transmission. Each frame is wrapped in a packet, which affixes several bytes of information used
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in establishing the connection and marking where the frame starts.
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Another protocol used in the data link layer player is the point to point protocol. Point-to-Point Protocol (PPP) is a data link layer (layer 2)
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communications protocol used to establish a direct connection between two nodes.
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For example these devices are routers
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It connects two routers directly without any host or any other networking device in between.
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It can provide connection authentication, transmission encryption and compression.
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we are going to focus on the topologies So what is a topology? A network topology is the arrangement
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of a network, including its nodes and connecting lines.
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There are two ways of defining network geometry: the physical topology and the logical topology
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Here we are seeing a physical topology.Physical topology is the placement of the various components
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of a network, including device location and cable installation.
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Here we can see a physical topology and what we are seeing is just the cable connections and name and
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symbols of the devices.
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As you can see. for example we have an Apple II Mac connected to gigabit switch we have an iPad which
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is connect to Apple Airport Extreme.
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We have an iPhone also connected to Apple Airport Extreme and we have Tivo premier which are connected
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to our gigabit switch.
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We have printer in here which is connected to gigabit switch and etc That's the physical view
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of the topology.
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We have three types of physical LAN topologies and they are Ring, Bus and Star.
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In the ring network topology, the workstations are connected in a closed loop configuration. as you can see in here
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. Adjacent pairs of workstations are directly connected. Other pairs of workstations are indirectly connected, the data passing through one or more intermediate nodes.
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...
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For example lets say that here is the PC one wants to communicate with the PC two: here the direction
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of the packets.
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Pc1 is going to this guy then this guy and this guy.
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But what if this guy fails? if this guys fails if there is an interruption on this guy, you can send the
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packet also from this way on the ring topology. in the bus network topology every workstation is connected
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to the main cable called the bus.
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Therefore, in effect, each workstation is directly connected to every other workstation in the network.
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as you can see. in the Star topology.
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There is a central computer server this guy to reach all the workstations are directly connected to
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Every workstation is indirectly connected to every other through the central computer.
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For example if this PC one wants to communicate with the PC two that should send the packet to this guy
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and this guy should forward the packet to the PC2.
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OK that seems like good but if theres a problem on the central device all the devices will fail as you
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can see and here are the physical WAN topologies. point to point
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Topology is the first one.
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That's the simplest topology with a dedicated link.
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between two endpoints. as you can see the second one is hub and spoke topology. hub and spoke here in
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a Hub-and-spoke Site-to-Site Wide Area Network (WAN) network topology, one physical
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site act as Hub while other physical sites act as spokes. Spoke sites are connected to each
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other via Hub as you can see in here and In Hub-and-spoke Wide Area Network (WAN) topology, the network communication
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between two spokes always travel through the hub.
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And here is the lastly we are going to focus on full mesh topology. full mesh topology connects each
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node to all other cluster nodes. This topology is highly reliable and fast, but it does not scale well.
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It is reliable because it provides many paths through the fabric in case of cable or node failure.
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It is fast with low latency because you can get to any node in the fabric in just one hop.
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It does not scale well because each additional node increases the number of fabric links and switch
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ports exponentially. as you can see in here we have r1 -2 -3
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4-5 and they're connected each other.
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And that provides really really big reliablity in this network.
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There's a really big redundancy for example if router one wants to communicate with router 2 to this path
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can be used.
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This path can be used or this path can be used because we are of various ways as you can see.
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So that means no matter if this link fails the traffic will go through from here from here from here
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or something like that.
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And lastly we're going to talk about logical topology.logical topology is the arrangement of devices
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computer network and how they communicate with one another.Logical topologies describe how signals act
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on the network. in a logical topology we can see IP addresses as you can see in here we can see
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Tunnell types we can see subnetmask and something like that.
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That's the logical view of the topology.