2Data Networks Developed because companies wanted to exchange info over long distances. At first they used sneakernet, but sharing data using floppy disks was not efficient.The solution was to network the resources (printers,servers) to increase productivity and save money.Companies in the 80s created a variety of network software and hardware, with their own standards. As a result they were incompatible with each other.
3Internetworking History One solution was to create LAN (Local Area Network) standards which provided guidelines for creating hardware and software..
4ENIAC – the first large scale electronic digital computer, weighed 30 Tons.
51947 – Transistors (tiny ON/OFF switches) were invented at Bell labs.
8Network ProtocolsProtocol suites are collections of protocols that enable network communication between hosts. A protocol is a formal description of a set of rules and conventions that govern how devices on a network communicate.Protocols determine the format, timing, sequencing, and error control of data communication. Without protocols the computer cannot create or rebuild the stream of incoming bits from another computer into the original data.These network rules are created and maintained by many different organizations, such as IEEE, ANSI, TIA.
9WANs (Wide Area Networks) LANs – Operate in a limited geographical area. Allow many users to access high-bandwidth media Provide full-time connectivity to local services. Connect physically adjacent devicesEx: Ethernet, Token Ring, FDDIWANs (Wide Area Networks)WANs interconnect LANs. They make it possible for businesses to communicate across great distances. WANs create a new class of workers called Telecommuters – never leave home to go to work.Operate over large geographically separate areas. Allow users to engage in real-time communication with other users. Provide full-time remote resources connected to local services. Provide , WWW, file transfer and e-commerce services.Ex: Modems, ISDN, DSL, Frame Relay, T or E carrier.
10MANs (Metropolitan-Area Networks) Spans a city and connects LANs, for example a bank with several branches might use a MAN. Rowville SC is a MAN using a wireless link.The MAN interconnects users is a geographic area lager than the LAN.MANs interconnect several LANs by bridging them with backbone lines.
11Specialized Networks Located within the LAN Storage-Area Networks (SANs)- is a high performance link between server-to-storage, storage-to-storage, or server-to-server.SANs offer Performance- allow access to disk or tape arrays by two or more servers at high speed. Availability- disaster tolerant using mirrored disks. Scalability- uses a variety of technologies and allows easy relocation.
12DATA CENTER – is a globally coordinated network of devices designed to accelerate the delivery of information over the Internet infrastructure. Service providers can use these services and avoid congestion by distributing the load. The Data Center can deliver the download of a movie over the Internet much quicker.
13The Internet Business Exchange™ Center – Critical Hubs in the Core Infrastructure of the Internet. Our Internet Business Exchange™ (IBX®) centers serve as core hubs for critical IP networks and Internet operations worldwide. With direct access to more than 200 networks, network and Internet operations through direct interconnection to the largest aggregation of networks for unmatched service diversity, flexibility and reliability. At Equinix, customers can directly access the providers that serve over 90% of the world's Internet networks and users.
14Intranets- Intranet server are different than public web servers, in that the public does not have access to the organizations intranet.Extranets- is and intranet that is partially accessible to authorized outsiders with a password and username.Virtual Private Networks (VPN) – is a private network constructed within a public network infrastructure like the Internet.The the telecommuter can access the company headquarters’ network through the Internet by building a secure tunnel between and PC and a VPN router in the headquarter.Access VPNs- provide access to remote user using dial-up, ISDN, DSL.Intranet VPNs- allow access to employees only. Extranet VPNs- allow access to users outside the organization. Advantaged: Allow privacy and security, encryption for clients(Bank) and allow employees access to the corporate network securely.
19Digital Bandwidthis the measure of how much information can flow from one place to another in a given amount of timeBandwidth is finite- there are limitation set by the laws of physics, DSL uses the same copper wires for voice but use a frequency range that is wider and therefore DSL ca send more bits per second than modems.Bandwidth is not free- a service provider charges and you need to make the right decisions about services and equipment.Bandwidth is key to analyze network performance and designing networks-Demand for bandwidth is ever-increasing- new applications are always created, voice over IP, so we need to anticipate the need for more bandwidth.
22Bandwidth is measured in bit per second. Bandwidth varies depending on the type of medium as well as the LAN and WAN technologies used. The physics of the medium, be it twisted pair copper, coaxial cable or fibre optic cable influences the limitations of the capacity to carry data.Ex; UTP limit is 1 Gbps.Bandwidth determined also by the equipment, the number of users, the amount of broadcasts and so on.Digital Bandwidth Versus Analog bandwidth Until recently, radio and television were sent through the air using analog electromagnetic waves which are measured in Kilohertz and Megahertz. Digital bit streams can carry video, voice and data unlimited amounts of data can be sent over the smallest (lower-bandwidth) digital channel. When digital info arrives at its destination it can be reassembled, viewed and listened to in its original form.
24WAN Services and Bandwidths Type of ServiceTypical UserBandwidthModemIndividuals56 KbpsDSLInd.,Telecommuter, small business12Kbps-6 MbpsISDNTelecommuters and small businesses128 Kbps to2 MbpsFrame RelaySmall institutions and reliable WANs56 Kbps to 44 MbpsT1Larger entities1.544 MbpsT3MbpsSTS-1 (OC-1)Phone companies/BackbonesMbpsSTS-3 (OC-3)MbpsSTS-48 (OC-48)Gbps
25Data Transfer Calculations Data ThroughputBandwidth is the measure of the amount of info that can move through the network at any given time.Throughput refers to the actual, measured bandwidth at a specific time of day using specific Internet routes while downloading a specific fileThroughput is often less than the maximum possible bandwidth.a major factor in analyzing a network’s performanceData Transfer CalculationsDivide the file size by the network bandwidth yields an estimate of the fastest time. The result is only an estimate, because the file size does not include any overhead added by the encapsulation process.File: 100 Mbytes * 8 = 800 Mbits / 100 MBitsps = 8 sec.
26Learning a concept of layers helps us understand how data flows (how data flows, how traffic flows and the rules of flow) and how computers communicate with each other. An example of flow is the Electrical or water networks. Each layer has a specific tasks and uses specific protocols.This layered communication process each layer performs a specific task.We will see how the network communication process is broken into a layered model.We will see how data is sent out over the network to reach its destination and the steps involved. This is helpful when troubleshooting.
27For computers to send information through a network, communication originates from a source to a destination. Before data can be sent across a network it must first be broken into smaller chunks.(Data Packets, data segments or data frames) before data can be sent in the form of electrical impulses, it must first be broken into manageable chunks. This includes a source and destination address (like a letter) to make communication possible.
28Computer ProtocolsFor data packets to travel from source to destination, all devices on the network must speak the same language.Network protocol: A set of rules that make communication on a network possible and efficient.Eg: While driving a car, other cars (should!) signal when they wish to make a turn; if they did not, then the roads would be chaos
29Networking Standards IOS International Organization for Standards. Proprietary systems were created that were privately developed, owned and controlled. This did not work well with other systems.Open means that free usage of the technology is available to the public.To address the problem of different networks systems being incompatible with each other, the International Organization for Standardisation (IOS) researched network schemes to find a set of rules. As a result the IOS created the OSI Model Open System Interconnection Reference Model, this allowed network vendors to create networks that would be compatible with other networks. The IEEE sets standards for networking technologies at Data Link and Physical Layers.
30The Purpose of the OSI Reference Model The primary objective of he OSI model is to accelerate the development of future networking products.The OSI reference model allows you to view the network functions and how information travels through a network and what occur at each layer.
31Why A Layered Model?Reduces complexity- Breaks network communication into smaller parts, making it easier to develop.Standardizes interfaces- facilitates standardization of network componentsFacilitates modular engineering- (development can be made in a modular fashion- Changes in one does not effect another Lay).Ensures interoperable technology- allows different network hardware and software to communicate with each other.Accelerates evolutionSimplifies teaching & learning- by breaking it up into smaller partsEasy troubleshooting
33The OSI Reference Model Each layer has a unique function.User interfaceData presentation and encryptionKeeping different applications’ data separateEnd-to-end connectionsAddresses and best pathAccess to mediaBinary transmissionApplicationPresentationSessionTransportNetworkData LinkPhysical7654321
34Application Layer Application Closest to the user and does not provide services to any other layer.Provides network communication services to applications which allow for the transfer of files(word), Bank transactions. Network redirectors allow applications like Word and Excel to “see” the network.Responsible for identifying and establishing the availability of communication partners and if there are sufficient resources for communication. Makes sure that appropriate resources are available to initiate a connection with destination host.Synchronizes and establishes an agreement on procedures for error recovery.Ex: , HTTP, telnet, FTP, SNMP.PresentationSessionTransportNetworkData-LinkPhysical
35Presentation LayerProvides data representation and code formatting. Translates between multiple data formats.Basically, the presentation layer is responsible for representing data so that the source and destination can communicate at the application layer.Compression and encryptionEx: Ascii, Jpeg, Tiff, sound and movie files.ApplicationPresentationSessionTransportNetworkData-LinkPhysical
36Session LayerProvides inter-host communication by establishing, maintaining, and terminating sessions between applications.Synchronizes dialogue between 2 hosts presentation layers and manages their data exchange. Session uses dialog control and dialog separation to manage the session parameters and login.Some Session protocols:NFS (Network File System) Sun/UnixSQL (Structured Query Language) define database info requestsRCP (Remote Call Procedure)ASP (AppleTalk Session Protocol)SCP (Session Control Protocol)X-window- UnixApplicationPresentationSessionTransportNetworkData-LinkPhysicalControls sessions, by determining which flows are part of the same sessions and which must be completed before it is considered complete.
37Transport Layer- boundary between application protocols and data-flow protocols Connection Oriented -Controls communication between end-to-end hosts using pre-established pathing.Sets up session establishment and tears down VCs.TCP provides the ability of multiple applications to use a single transport (Multiplexing)Reliability and Error Recovery- TCP segments and reassembles the data, adding a header with control information for sequencing and acknowledging packets received.The segment header also includes source and destination ports for upper-layer applicationsFlow control using- windowing, buffering and source quench messages (sent by the recipient when the buffers (memory) are nearing capacity)TCP uses 3 way handshake- synchronizes sequence number between hosts.PresentationSessionTransportNetworkData-LinkPhysical
38Transport LayerUDP is connectionless. UDP does not acknowledge the receipt of packets, no sequencing, no virtual circuit creation, no guarantee delivery but less overhead. Provides error detection but not recovery.TCP uses 3 way handshake- synchronizes sequence number between hosts, provides reliability by establishing a communication session before sending data (Virtual Circuit) Provides error detection and recovery.The transport layer attempts to provide a data transport service that shields the upper layers from transport implementation details.
39Network Layer Application Presentation Session Transport Network Provides connectivity and path selection(path determination and switching).Connectionless, and Responsible for logically addressing the packetAddressing is done through routed protocols such as IP, IPX, AppleTalkPath Selection is done by using routing protocols such as (RIP, IGRP are classfull routing prot. Do not include subnet mask in routing update), EIGRP, OSPF, and BGP.Routers operate at the Network Layer, ICMP(traceroute and ping), ARP(DHCP), RARP (diskless workstations) operate at this layer.Fragments data into smaller packets to accommodate smaller MTU size (Maximum Transmission Units)ApplicationPresentationSessionTransportNetworkData-LinkPhysical
40Data-Link Layer Application Handles error notification, network topology issues, and physically addressing the frame.Media Access Control -Provides the transit of data across a physical link. Access to the media using a physical address called a MAC address (48 bits) two part address- 3 bytes OUI, 3 for serial number.Flow control and error detection.through either...Deterministic—token passingNon-deterministic—broadcast topology (collision domains)Important concept: CSMA/CDLLC provides SAPs (service access points) for upper layers, flow controlPresentationSessionTransportNetworkData-LinkPhysical
41DATA-LINKPrepares data from upper layers to be transmitted over a particular physical medium, the final encapsulation.Convert data into bits, so it can be transmitted by physical layer.Error detection: CRC Cyclical Redundancy Check or FCS Frame check sequence, if an error is detected the frame is discarded.Frame Relay, HDLC, PPP encapsultions.Ethernet , Token Ring 802.5
42Physical LayerProvides electrical, mechanical, procedural and functional means for activating and maintaining links between systems. Like voltage levels, timing, physical data rates (100 Mbps), maximum transmission distances (100 meters).Standards for sending data over the physical medium through which bits flow. Media types:IEEEConnectors-Ethernet CAT 5 cable, RJ45 jacks.Coaxial cableFiber Optics cable FDDI Fiber Distributed Data InterfaceThe atmosphereApplicationPresentationSessionTransportNetworkData-LinkPhysical
43The OSI Reference Model ApplicationPresentationSession7654321The top 3 layers are known as the appli-cation layers because they deal with the user interface, data formatting, and the application access.
44The OSI Reference Model ApplicationPresentationSessionTransportNetworkData LinkPhysical7654321Data TransportLayers 1-4 are known as the data flow layers because they control the physical delivery of messages over the network and how data is transferred.
53For data to travel from source to destination, each layer at the source must communicate with its peer layer at the destination, this is called Peer-To-Peer communication. During this process, the protocols at each layer exchange information, called Protocol data Units (PDU) between each layer.each layer depends on the services of the one below it. If a computer wants to send data to another it must package the data for delivery, this is encapsulation. Encapsulation wraps data with the necessary protocol information before network transit.
54Encapsulation wraps data with necessary protocol information before transit.
55How Data is Encapsulated Build the data.Package the data for end-to-end transport.Append (add) the network address to the headerAppend (add) the Physical address to the data link header.Convert to bits for transmission.
56De-Encapsulation Headers are looked at at each layer and removed. 1-Read the physical address MAC, strip it off the header and the trailer, creating a packet and passed on to upper-layers. 2- If there are errors, discard the data or ask for retransmission.Each layer depends on the services of the other below it. To provide this service, the lower layers uses encapsulation to put the PDU from the upper layer into its data field; then adds whatever header and trailer is needed.
57The Importance of TCP/IP The U.S. Department of Defense (DoD) created the TCP/IP reference model. The open standard for the Internet is TCP/IP. Makes communication possible between any computers on earth. The DOD wanted packets to get through every time, under any conditions.
60Common TCP/IP Protocols FTP - File Transfer ProtocolHTTP - Hypertext Transfer ProtocolSMTP - Simple Mail Transfer protocolDNS - Domain Name SystemTFTP - Trivial File Transfer Protocol
61Common TCP/IP Protocols The transport layer involves two protocols - transmission control protocol (TCP) and user datagram protocol (UDP).
62Similarities:both have layersboth have application layers, though they include very different servicesboth have comparable transport and network layerspacket-switched (not circuit-switched) technology is assumednetworking professionals need to know both
63Networking DevicesEnd User Devices(Hosts) – Include computers, scanners, printers.Network Devices – Include all devices that allow end user devices to communicate. Hosts devices are physically connected to the network media using a Network Interface Card (NIC)Install a NIC card in the motherboard expansion slot. On a laptop, the NIC is usually the size of a PCMCIA card
64NIC SpecificsNICs provide hosts with access to media by using a unique code called a MAC address. This address is used to control data communication on the network.The NIC controls the hosts access to the media.MAC stands for Media Access ControlNICs operate at Layer 2 !!It translates the parallel signal of the PC into a serial format sent over the network cable.I converts 0s and 1s into an electrical signal, pulses of light or radio waves.
65LAYER 1—RepeaterCleans up (regenerates) and retimes the signal at the bit level.Used when a network’s cabling extends beyond its capability. UTP is 100 meters.
66What’s the maximum distance for Cat 5 cable? NICs, Repeaters, & HubsRepeaters can be used to increase the distanceNICNICSo what can we use if this distance is greater than 100 meters?What’s the maximum distance for Cat 5 cable?100 metersWhen the signals leave the host they are strong. The longer the cable length, the weaker and more deteriorated the signal becomes. Repeaters amplify and retime signals at the bit level to allow them to travel longer distances on the media.
67LAYER 1—Hub (multi-port repeater) The CloudSimply a multi-port repeater. Active and passive hubs.Used to connect multiple devices, the hub acts as the centre of the physical star, yet same contention as a bus.Token Ring Hub-is called a MAU (Media Attachment Unit) FDDI is a concentrator.
68Same Broadcast Domain and same Collision Domain In this picture, all hubs forward all traffic to all devices.
69To lessen the amount of LAN traffic, businesses began to uses bridges to filter frames based on MAC addresses = Look at the Local Addresses like the post office.Bridge
70LAYER 2—Bridge Connects two LAN segments and pass frames. Build tables of all Mac addresses on the network.Keeps traffic local by filtering traffic based on MAC Addresses contained in the layer 2 Frame. Creates more usable bandwidth.the bridge keeps track of MACs on each side of the bridge and filters traffic based on MAC addresses only.SEGMENTATION = Creates separate or more collision domains.
71Switch= Micro segmentation A switch (also know as a multi-port bridge), can effectively replace these four bridges.Switch= Micro segmentation
72Another benefit of a switch is that each LAN segment gets dedicated bandwidth. Combines the connectivity of a hub and the traffic regulation of a bridge They switch frames out only the port connected to the host.Switch10 MbpsThe Cloud10 Mbps
73Router Layer 3Routers filter traffic based on IP addresses. The IP address tells the router which LAN segment the ping belongs to.1116
74LAYER 3—RouterThe CloudCan be used to connect different Layer 2 technologies such as Ethernet, Token Ring and FDDI.Makes decisions based on network addresses (IP Addresses).What are the routers two main functions?
75Router’s Two Main Functions Path DeterminationPacket SwitchingOperate at Layers 1, 2 AND 3
76Other DevicesGateways – Is an Access Server combining routing, remote access, voice gateway, firewall and a digital modem.DSLAM ( Digital Subscriber Line Access Multiplexer) – Is a DSL box giving you access to the carrier netwok.CMTS ( Cable Modem Termination System) used by cable operators as a concentration point or hub in the cable network to provide high-speed Internet access. This would be used in a hotel or apartment building.Optical Platforms – Used as backbone and WANs for fibber backbone.Firewalls – Is either a firewall running on a router or server or a standalone hardware device on a network.AAA server – is a program that handles user requests for access to network resources. They provide authentication, authorization and accounting (who is doing what)
77VPN concentrators – offer remote access and site-to-site VPN capabilities. Wireless NICs - Have built in antennas.Wireless Access Points – is a wireless transceiver that acts as a hub.Wireless Bridge – provides high-speed ( 11 Mbps) and long range line of sight wireless connectivity (up to 25 Miles)
82Network Topologies – are defined how computers, printers and other network devices are connected. It defines the physical layout of wires as well as the paths used for data transmission.Network have both Physical and Logical topologies. The physical refers the the layout of devices and the media (cables). Logical defines how the media is accessed by the hosts fro sending data.BusRingStarMesh
83Bus Topology Single backbone All devices are directly connected to a central cable.Each end of the bus must be properly terminated to absorb electrical signals, so they don’t bounce around.Bus Topology
84Star Topology All nodes connected to a central device Center of star is usually a hub or a switchUsed for Ethernet technologies.Each device is connected to a central device with its own cable, so if one device has a problem with a bad cable, only that device will be affected. But if the centre of the star fails the whole network will fail.
85Extended Star Topology Connects individual star topologies together.At the center of the star is a hub or a switch.Extends the length and size of the network.
86Ring Topology No backbone A host is directly connected to each of its neighborsUsed for token passing logical topologies. Two types of rings exist: Single and Dual ring. In a dual ring the 2 rings allow data to be sent in both directions, this type of setup creates redundancy (fault tolerance).
87Hierarchical Topology Like the extended star except a computer controls traffic—not a hub or a switch.Server
88Mesh Topology like the Internet Each host has its own connection to every other host for redundancy.Used in situations where communication must not be interrupted. Usually to connect routers in a WAN.
89Logical Topologies Broadcast Topology Token Passing Topology Each host on the LAN sends its data (or broadcasts its data) to every other host.Access to media is based of “first-come, first-serve.” (Ethernet works this way)Token Passing TopologyAccess to media is controlled by an electronic token.Possession of the token gives the host the right to pass data to its destination.