COMPUTER NETWORKING AND TOPOLOGY

 

COMPUTER NETWORKING

Networking:-            A computer network is a group of computer systems and other computing hardware devices that are linked together through communication channels to facilitate communication and resource-sharing among a wide range of users. When a group of computers connected to each other share or exchange information and resources is called networking.

History of computer networking:-         Computers were only used as stand-alone machines.  Computer networks were created to establish a communication link between different users within an organization. The advanced research projects agency (ARPA) designed advanced research projects agency network (ARPANET) for United States department of defense. It was the first network in the world.In 1969, the first ARPANET link was established between the imp nodes at the University of California at los Angeles (UCLA).

What is communication:-             To convey a message, idea, a picture or speech that is record and understood clearly and correctly by the person for whom it is intended.

Means of communication:-

Close by

ü  Speak loudly

Not Very far off

ü  Write on a piece of paper & send it through messenger.

Large distance

ü  Send it by post

Large distance/small message

ü  Through telephone

Large distance/large and mixed message

ü  ?

Data communication:-

Telecommunication

ü  Communication at a distance.

Data

ü  Information presented in whatever form is agreed upon by the parties creating and using the data.

Data Communication

ü  Exchange of data between two devices via some form of transmission medium such as a wire cable.

Communication System:-            Combination of hardware, software and data transfer links. That make up a communication facility. For transferring data. In cost effective manner.

 

Data communication:-

Four Basic Factors of Data Communication.

ü   Reliability

ü   Timeliness

ü   Security

ü   Cost

 

Communication Model :-

Source

ü   Generates data to be transmitted

 Transmitter

ü   Converts data into transmittable signals

 Transmission System

ü   Carries data

 Receiver

ü   Converts received signal into data

 Destination

ü   Takes incoming data

Communication 

Data communication components:-

Message         The message is the information (data) to be communicated. Popular forms of information include text, numbers, pictures, audio, and video.

Sender            The sender is the device that sends the data message. It can be a computer. Workstation, telephone handset, video camera, and so no.

Receiver         The receiver is the device that receives the message, it can be a computer, Workstation, telephone handset, video camera, and so no.

Transmission medium.        The transmission medium is the physical path by which a message travels from sender to receiver. Some example of transmission media include twisted-pair wire, coaxial cable, fiber-optic cable, and radio waves.

Protocol.        A protocol is a set of rules that govern data communications. It represents an agreement between the communicating devices. Without a protocol, two devices may be connected but not communicating, just as a person speaking French cannot be understood by a person who speaks only Japanese.

 

Data Representation:-

Text

ü   Sequence of bits (0s &1s)

ü   Different bit patterns represent text symbols.

ü   Each set is called code.

ü   Unicode used in present systems; uses 32 bits.

ü   ASCII use 7 bits and represent first 127 characters in Unicode.

ü   ASCII characters are also known as Basic Latin

Numbers

ü   Also represented by bit patterns.

ü   ASCII is not used to represent numbers.

ü   Numbers are directly converted into binary.

 Images

ü   Represented in terms of pixel values.

ü   For black & white one bit pattern is enough.

ü   For showing four levels: two bits.

ü   Color by value of RGB.

Audio

ü   Different from text, numbers or images.

ü   It is continuous and not discrete.

ü   For encoding it is changed to digital signal.

 

 Video

ü   Can be continuous or discrete.

ü   Changed to digital signal for encoding

 

Transmission Modes

 

 

Simplex mode:        The communication is unidirectional.Only one of the two devices on a link can transmit; the other can only receive.Examples Radio transmission and TV.The simplex mode can use the entire capacity of the channel to send data in one direction.

 

Half duplex mode:- Each station can both receive and transmit but not at the same time. When one device is sending, the other can only receive.Walkie-Talkies/VPS Set.Half duplex mode is used in cases where there is no need for communication in both directions at the same time.

Full duplex mode:-             Both stations can receive and transmit at the same time.   Signals going in one direction share the capacity of the link with signals going in other direction.One method to utilize full capacity is to have two separate physical paths.Telephone/Mobile Communication. Full duplex mode is used in cases where there is need for communication in both directions at the same time.

 

 

Network Terminology

Computer Network:-          Computer Network is a collection of autonomous computers interconnected by a single technology. eg Ethernet LAN. Is Internet a computer network? It is not a single network, but a network of networks i.e an Inter-network

Uses of Computer Networks:

 

Network Terminology:-

Bit - Binary digit, either 0 or 1

Bit rate – Data transmission speed – bits per second

Mbps – millions of bits per second

8 bits = 1 byte

Mb – million bits (quantity of data)

MB – million bytes (quantity of data)

GBPS – Billion bits per second (data speed)

Teraflops – trillion operations per secondNode: Any device connected to the network, usually a computer, but it could be a printer or a scanner.

Segment       Any portion of a network that is separated by a switch, bridge or a router from another part of a network.

Backbone:   The main cabling of a network to which all segments are connected. Usually, the backbone is capable of carrying more information than the individual segments.

Topology: The way each node is physically connected to the network in a chain.

Bandwidth: The internet consists of tens of millions of computers throughout the world, all connected by cables. If you've ever wondered why it takes so long to download certain web pages or other files to your computer. It's all determined by the bandwidth of the connection between your computer and your internet service provider (rate of data transfer per second).

  

Broadband: Narrowband is usually referred to dial up internet connection and it usually varies from speeds of about 50 characters per second to about 60 kbps. Broadband is usually regarded as any internet connection that can deliver speeds faster than 60 kbps.

 

Domain name: The unique name that identifies an Internet site. Domain Names always have 2 or more parts, separated by dots.Internet is based on IP addresses, not domain names, web servers depend on a Domain Name System (DNS) to translate domain names into IP addresses. Simply stated, domain names allow people to find your web site by name rather than by its numerical (IP) address.

 

Domain name system (DNS)       The network service used in TCP/IP networks that translates host names to IP address.

 

Protocol        Set of rules or standards. Enables computers to connect with one another. Enables exchange of information without error. Example: protocol can define the way in which two programs transfer a file across the internet. Set of rules or standards. Enables computers to connect with one another. Enables exchange of information without error. Example: protocol can define the way in which two programs transfer a file across the internet.  Protocol generally accepted for standardizing communication is seven layer OSI model.

 

DHCP (dynamic host configuration protocol)            It is a communication protocol that lets administrator centrally manage and automate the assignment of IP addresses in an org network. Without DHCP, IP addresses must be entered manually at each time a computer moves to new loc. DHCP automatically releases IP for all computers connected to a network. The IP addresses releases by DHCP is valid on basis of the lease duration

 

DHCP SERVER:  A computer running the DHCP Server service that holds information about available IP addresses and related configuration information as defined by the DHCP administrator and responds to requests from DHCP clients.

 

DHCP CLIENT:  A computer that gets its IP configuration information by using DHCP.

 

SCOPE:  A range of IP addresses that are available to be leased to DHCP clients by the DHCP Server service.

 

SUBNETTING: The process of partitioning a single TCP/IP network into a number of separate network segments called subnets.

 

DHCP OPTION:   Configuration parameters that a DHCP server assigns to clients. Most DHCP options are predefined, based on optional parameters defined in Request for Comments (RFC) 2132, although extended options can be added by vendors or users.

 

OPTION CLASS:     An additional set of options that can be provided to a DHCP client based on its computer class membership. The administrator can use option classes to sub manage option values provided to DHCP clients. There are two types of options classes supported by a DHCP server running Windows Server 2003: vendor classes and user classes.

 

RESERVATION:     A specific IP address within a scope permanently set aside for leased use by a specific DHCP client. Client reservations are made in the DHCP database using the DHCP snap-in and are based on a unique client device identifier for each reserved entry.

 

EXCLUSION/EXCLUSION RANGE:       One or more IP addresses within a DHCP scope that are not allocated by the DHCP Server service. Exclusions ensure that the specified IP addresses will not be offered to clients by the DHCP server as part of the general address pool.

 

MULTICAST IP ADDRESSES: Multicast IP addresses allow multiple clients to receive data that is sent to a single IP address, enabling point-to-multipoint communication. This type of transmission is often used for streaming media transmissions, such as video conferencing.

 

MULTICAST SCOPE:          A range of multicast IP addresses that can be assigned to DHCP clients. A multicast scope allows dynamic allocation of multicast IP addresses for use on the network by using the multicast address dynamic client allocation protocol (MADCAP) protocol, as defined in RFC 2730.

 

IP Address:              A unique number used to specify hosts and networks. Internet Protocol (IP) numbers are used for identifying machines that are connected to the Internet.They are sometimes called a dotted quad and are unique numbers consisting of 4 parts separated by dots.

Eg 216.119.81.205

Every machine has a unique IP number - if not, it is not really on the Internet

.

Fiber Optic:  A type of network cable that uses a central glass or plastic core surrounded by a plastic coating.

Alias.  A name that points to another name. Aliases are used to make the original name easier to remember or to protect the site's identity.

 

PING (PACKET INTERNET GOPHER):             A TCP/IP utility used to test whether another host is reachable.  A request is sent to the host, who responds with a reply if it is reachable.  The request timed out if the host is not reachable.

 

POP3:  The post office protocol version 3 pop3 is intended to permit a workstation to dynamically access a mail drop on a server host. It is usually used to allow a workstation to retrieve mail that the server is holding for it. Pop3 uses port.

 

SUBNET MASK:     A subnet mask is a 32 bit number that is used to partition IP addresses into a network ID and a host ID. Subnet masks are used by TCP/IP services and application to determine whether a given IP address on an interwork is a local network address or a remote network address.

 

SERVER:  Server is a high configuration computer which provides services to all clients. A computer that provides resources to the clients on the network.

 

CLIENT:  Client is a normal configuration computer which has taken services from server.

 

ADDS:  Active Directory Domain Service (ADDS) stores information about users, computers and other devices on the network. It helps administrators securely manage these info and facilitates resource sharing and collaboration between users. It is also required for Microsoft Exchange server tech. ADDS requires DNS server to be installed.

 

Web Server:  Web servers are computers that lets you to share info over the internet, through internets and intranets. Web server include internet information services (IIS) 8.0 with enhanced security, diagnostic and administration. It is a unified platform that integrates IIS 8.0, ASP.net and windows common foundation.

 

 

TYPE OF CONNECTION

Point to Point, Multipoint

 

 

 

 

Point to Point connection            Provides dedicated link between two devices. Entire capacity is reserved for two devices. Many connections between Include pairs of computers. Packets visit one or more intermediate machines. Multiple routes. Routing algorithm – To determine the best route. Also called as unicasting. Larger networks – Point to Point eg. WAN.

 

 

Multipoint connection Spatially shared or time shared. Also known as multi drop connection More than two devices are connected through a shared media. Capacity is shared by more than two devices.

 

Topology:-   Network topology is the interconnected pattern of network element. There are five common types of topology.

1.    Mesh Topology         4.         Ring Topology

2.    Star Topology           5.         Hybrid Topology

3.    Bus Topology

Mesh Topology:     All PCs connected to each other through point to point link A fully connected mesh network requires n (n-1)/2 physical channels to link all devices. All devices must have (n-1) I/O ports. Provides Redundancy. Dedicated media between nodes to carry traffic More secured. Rarely used. Internet example of partial mesh topology.

 

Star topology:-        All PCs connected to a central device. Central device (hub/switch) either sends the message to all the computers (Broadcast NW) or only to the destination (switched NW).Hub/Switch in a broadcast NW can be active or passive. Ethernet 10 Base T is a popular NW based on this technology. Star NW can be expanded by placing another hub/switch and thus connecting many more nodes (Hybrid star NW).

 

Bus topology:         Uses a linear single cable (Backbone) for all PCs attached (Multipoint).PCs attached through drop cables to main cable. All traffic travels the full cable and can be seen by all PCs. NOS keeps track of the address of the PCs and manages the flow of data based on address scheme. Each Node is connected to two other nodes except nodes at the end. Often found in client server systems doing file server type of job. Not usually used for info processing. Ethernet 10 Base2 (also known as thin net) is based on bus topology. Computer who wants to send the message to another computer will first send an addressing message to it. Sending computer waits for the response. After receiving the response the link will be established and the message will be sent.

 

Ring Topology:-     Nodes are connected in a circle using cable segments. Each node is physically connected to two other nodes. Each node passes info to the next node unless info arrives at the destination. Ring is an active network as each PC transmits what it receives. There is no termination as there is no end. Found in peer to peer networks where each machine manages both info processing and the distribution of data files. FDDI (Fiber Distributed Data Interface) is a fast fiber optic network based on the ring topology.

 

 

Hybrid Topology:-             Combines the bus and the star. Links several star hubs together with bus trunks. If one computer fails, the hub can detect the fault and isolate the computer. If hub fails, computers connected to it will not be able to communicate and bus network will be broken into two segments that cannot communicate with each other.

 

 

Thanks………