Introduction To Networking

Overview of LAN,MAN,WAN

LAN A local-area network (LAN) is a computer network that spans a relatively small area(100mtr). Most LANs are confined to a single building or group of buildings, however, one LAN can be connected to other LANs over any distance via telephone lines and radio waves. A system of LANs connected in this way is called wide area network(WAN)

Types of LANs The three most popular types of LANs are: Token ring network FDDI (Fiber Distributed Data Interface) network Ethernet

Token Ring Network Originally developed by IBM in 1970’s Still IBM’s primary LAN technology In cases of heavy traffic, the token ring network has higher throughput than Ethernet due to the deterministic (non- random) nature of the medium access Is used in applications in which delay when sending data must be predictable Is a robust network i.e. it is fault tolerant through fault management mechanisms Can support data rates of around 16 Mbps Typically uses twisted pair

FDDI (Fiber Distributed Data Interface) FDDI is a standard developed by the American National Standards Institute (ANSI) for transmitting data on optical fibers Supports transmission rates of up to 200 Mbps Uses a dual ring First ring used to carry data at 100 Mbps Second ring used for primary backup in case first ring fails If no backup is needed, second ring can also carry data, increasing the data rate up to 200 Mbps Supports up to 1000 nodes Has a range of up to 200 km Source:http://burks.brighton.ac.uk/burks/pcinfo/hardware/ethernet/fddi.htm

Ethernet First network to provide CSMA/CD Developed in 1976 by Xerox PARC (Palo Alto Research Center) in cooperation with DEC and Intel Is a fast and reliable network solution One of the most widely implemented LAN standards Can support data rates in the range of 10Mbps- 10 Gbps Used with a bus or star topology

Metropolitan area network A Metropolitan Area Network (MAN) is a network that is utilized across multiple buildings Commonly used in school campuses or large companies with multiple buildings Is larger than a LAN, but smaller than a WAN Is also used to mean the interconnection of several LANs by bridging them together. This sort of network is also referred to as a campus network

Wide area network A Wide Area Network is a network spanning a large geographical area of around several hundred miles to across the globe May be privately owned or leased Also called “enterprise networks” if they are privately owned by a large company It can be leased through one or several carriers (ISPs-Internet Service Providers) such as AT&T, Sprint, Cable and Wireless Can be connected through cable, fiber or satellite Is typically slower and less reliable than a LAN Services include internet, frame relay, ATM (Asynchronous Transfer Mode)

Example of WAN application Sprint Network LA Runs a 100 Mbps LAN Sprint provisions a connection between the two networks DC Runs a 1Gbps LAN

Network Interconnection Components Networks can be connected to each other through several components Repeater Bridge Router Gateway Before explaining the above components, we need to understand the OSI model

Overview of Network Topologies

Network Topologies Network Topology – Maps of how the physical or logical paths of network devices connect. The three major topologies are star, ring, and bus. Star Topology – Most common Ethernet network topology where each device connects to a central hub or switch. Hub – A device used with the Universal Serial Bus or in a star network topology that allows multiple device connections. Switch – In star networks, a Layer 2 central controlling device. A switch looks at each data frame as it comes through each port. Ring Topology – Network that is physically wired like a star network but, logically in a ring; passes control from one device to the next in a continuous fashion using a special data packet called a token. Used in Token Ring networks. Bus Topology – Network wherein all devices connect to a single cable. If the cable fails, the network is down. Mesh Topology – Network where all devices connect to each other by cabling to provide link redundancy for maximum fault tolerance. Most likely in WANs.

Network Topologies Hub/Switch Network – Figure # 3

Network Topologies Star Topology Network – Figure # 4

Network Topologies Logical Ring Topology Network – Figure # 5

Network Topologies Bus Topology Network – Figure # 6

Network Topologies Network Topologies Network – Table # 1

Overview of OSI and TCP/IP Layers

Basic of TCP/IP Transmission Control Protocol (TCP) – uses a set of rules to exchange messages with other Internet points at the information packet level Internet Protocol (IP) – uses a set of rules to send and receive messages at the Internet address level Is the predominate network protocol in use today (Other includes OSI Model) for interoperable architecture and the internet. TCP/IP is a result of protocol research and development conducted on experimental packet switched network by ARPANET funded by the defense advanced research projects agency (DARPA). TCP/IP used as internet standards by the internet architecture board (IAB).

ISO-OSI Reference Model (1) Open Systems Interconnection No one really uses this in the real world. A reference model so others can develop detailed interfaces. Value: The reference model defines 7 layers of functions that take place at each end of communication and with each layer adding its own set of special related functions. Flow of data through each layer at one It is use to guide product implementors so that their products will consistently work with other products. 21

ISO-OSI Reference Model (2) File Transfer, Email, Remote Login  ASCII Text, Sound (syntax layer)  Establish/manage connection  End-to-end control & error checking (ensure complete data transfer): TCP  Routing and Forwarding Address: IP  OSI divides telecommunication into seven layers. The layers are in two groups. The upper four layers are used whenever a message passes from or to a user. The lowest three layers (Up to network layer) are used when any message passes through the host computer. Message intended for this computer pass to the upper layers. Message destined for some other host are not passed up to the upper layers but are forwarded to another host. Physical layer: Bit stream through network at electrical/mechanical level Two party communication: Ethernet  How to transmit signal; coding Hardware means of sending and  receiving data on a carrier 22

Network support Layers ISO/OSI Reference Model Explained Application User support Layers or Software Layers Layer - 7 Layer - 6 Layer - 5 Layer - 4 Layer - 3 Layer - 2 Layer - 1 Presentation Session Transport Core layer of the OSI Network Network support Layers or Hardware Layers Data Link Physical

Data Flow From Application layer Presentation Session Transport Network Data Link Physical Application Application Layer is responsible for providing an interface for the users to interact with application services or Networking Services . Ex: Web browser etc. Identification of Services is done using Port Numbers (Service Point Addresses). Port is a logical communication Channel Port number is a 16 bit identifier. Total No. Ports 0 – 65535 Server Ports 1 - 1023 Client Ports 1024 – 65535 24

ISO/OSI Layer 7 Service Port No. HTTP 80 FTP 21 SMTP 25 TELNET 23 TFTP 69 25

Data Flow From Application Layer 21 80 25 67 53 69 Presentation Session Transport Network Data Link Physical 26

Data flow from Presentation Layer Application Presentation Session Transport Network Data Link Physical Presentation Layer It is responsible for defining a standard format to the data. It deals with data presentation. The major functions described at this layer are.. Encoding – Decoding Ex: ASCII, EBCDIC (Text) JPEG,GIF,TIFF (Graphics) MIDI,WAV (Voice) MPEG,DAT,AVI (Video) Encryption – Decryption Compression – Decompression Presentation 27

Data Flow from Presentation Layer Application Presentation Session Transport Network Data Link Physical Data Data Data 28

Data Flow from Session layer Application Presentation Session Transport Network Data Link Physical Session Layer It is responsible for establishing, maintaining and terminating the sessions. Session ID is used to identify a session or interaction. Examples : RPC  Remote Procedural Call Session 29

Data Flow from Transport layer Application Presentation Session Transport Network Data Link Physical Transport Layer It provides data delivery mechanism between the applications in the network. The major functions described at the Transport Layer are.. Identifying Service Multiplexing & De-multiplexing Segmentation Sequencing & Reassembling Error Correction Flow Control Transport Transport Layer provides data delivery mechanism between the applications in the network 30 30

Services are identified at this layer with Identifying a Service Services are identified at this layer with the help of Port No’s. The major protocols which takes care of Data Transportation at Transport layer are…TCP,UDP Transmission Control Protocol Connection Oriented Supports Ack’s Reliable communication Slower data Transportation Protocol No is 6 Eg: HTTP, FTP, SMTP User Datagram Protocol Connection Less No support for Ack’s Unreliable communication Faster data Transportation Protocol No is 17 Eg: DNS, DHCP, TFTP TCP UDP 31

Data flow from Transport Layer Application Presentation Session Transport Network Data Link Physical Data Data Data TH Segment Data 32

Network Layer Network Layer It provides Logical addressing & Path determination (Routing) in this layer. The protocols that work in this layer are: Routed Protocols: IP, IPX, AppleTalk.. Etc Routed protocols used to carry user data between hosts. Routing Protocols: RIP, OSPF.. Etc Routing protocols performs Path determination (Routing). Application Presentation Session Transport Network Data Link Physical Network 33

Devices that work at Network Layer are Router, Multilayer switch etc.. Data flow from Network Layer Application Presentation Session Transport Network Data Link Physical Data Data Data Devices that work at Network Layer are Router, Multilayer switch etc.. Segment NH Packet Segment 34

Data link Layer Datalink Layer It has 2 sub layers MAC (Media Access Control) It provides reliable transit of data across a physical link. It also provides ERROR DETECTION using CRC (Cyclic Redundancy Check) and ordered delivery of Frames. Ex: Ethernet, Token ring…etc LLC (Logical Link Control) It provides communication with Network layer. Negotiates with Network Layer using SAP & SNAP protocols Application Presentation Session Transport Network Data Link Physical Data Link 35

Devices that work at Data link layer are Switch, Bridge etc.. Data flow from Data Link Layer Application Presentation Session Transport Network Data Link Physical Data Data Data Segment Devices that work at Data link layer are Switch, Bridge etc.. Packet DH DT Frame Packet Packet 36

Physical Layer Physical Layer It defines the electrical, Mechanical & functional specifications for communication between the Network devices. The functions described at this layer are.. Encoding/decoding: It is the process of converting the binary data into signals based on the type of the media. Copper media : Electrical signals of different voltages Fiber media : Light pulses of different wavelengths Wireless media: Radio frequency waves Mode of transmision of signals: Signal Communication happens in three different modes Simplex, Half-duplex, Full-duplex Protocols works at physical layer: 10BaseT, 100BaseT, V.35, RS-232..etc Application Presentation Session Transport Network Data Link Physical Physical 37

Data flow from Physical Layer Application Presentation Session Transport Network Data Link Physical Data Data Data Segment Packet Devices that work at physical layer are .. Hub, Repeater.. Etc Frame Bits 38

Data Encapsulation & De-capsulation B Application Presentation Session Transport Network Data Link Physical Data Data Data Data Data Data TH Segment Data TH Data Segment TH NH Packet Segment NH Segment Packet NH DT DH Frame Packet Packet Packet DT Packet DH Frame DT DH Bits Bits 39

OSI Vs TCP/IP & De-capsulation OSI Layers TCP/IP Layers Application Presentation Session Transport Network Data Link Physical Application Host-to-Host Internet Network Access 40

Associated TCP/IP Protocols & Services HTTP This protocol, the core of the World Wide Web, facilitates retrieval and transfer of hypertext (mixed media) documents. Stands for the HyperText Transfer protocol Telnet A remote terminal emulation protocol that enables clients to log on to remote hosts on the network. SNMP Used to remotely manage network devices. Stands for the Simple Network Management Protocol. DNS Provides meaningful names like achilles.mycorp.com for computers to replace numerical addresses like 123.45.67.89. Stands for the Domain Name System. SLIP/ PPP SLIP (Serial Line Internet Protocol) and PPP (Point to Point Protocol) encapsulate the IP packets so that they can be sent over a dial up phone connection to an access provider’s modem.

Overview of Networking Devices

Hubs Intelligent hubs have console ports, to allow monitoring of the hubs status and port activity. Passive hubs just repeat any incoming signals to every port available, therefore does not act as a line repeater. Passive hubs just split signals to multiple ports but do not regenerate the signals, which means that they do not extend a cable’s length. They only allow two or more hosts to connect to the same cable segment. Active hubs regenerate signals. Hubs utilise star topology.

Advantages Disadvantages Hub Pros & Cons As an active hubs regenerate signals, it increases the distance that can be spanned by the LAN (up to 100 meters per segment). Hubs can also be connected locally to a maximum of two other hubs, thereby increasing the number of devices that can be attached to the LAN. Active hubs are usually used against attenuation, which is a decrease in the strength of the signal over distance. Disadvantages Bandwidth is shared by all hosts i.e. 10Mbs shared by 25 ports/users. Can create bottlenecks when used with switches. Have no layer 3 switching capability. Most Hubs are unable to utilise VLANS.

Switches A switch is a multi-port bridge. It operates at OSI data link layer 2. It stores MAC addresses in an internal lookup table. Temporary switched paths are created between the frame’s source destination. Some Switches have limited layer 3 IP routing capabilities. Switches can be configured to use VLANS. Switches support spanning tree protocol to create resilient networks.

Example Topology Switch Hub UTP 10Mbs Fibre 100Mbs 46

Transceiver Modules Connects to any Auxiliary Unit Interface port (AUI). Operates at OSI layer 1. Allows multiple media types to connect to an Ethernet device. i.e. fibre ST/SC,Co-ax cable, and UTP. UTP Co-axial

Routers Routers are OSI network layer 3 devices Using interface modules can connect different layer 2 technologies e.g. Ethernet, FDDI, token ring etc… Routers have the capability to interconnect network segments or entire networks (WANS/MANS). These devices examine incoming packets to determine the destination address of the data. It then examines its internal routing table to choose the best path for the packet through the network, and switches them to the proper outgoing port.

Example Router Topology

Summary and References Please go through below link for further Study: http://www.tcpipguide.com/free/t_IntroductiontoNetworking.htm http://openbookproject.net/courses/intro2ict/networking/intro.html

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