COMPUTER NETWORKS
Lecture Notes
Course Code -
BCS-308
Course Name
- INTERNET & WEB TECHNOLOGY-I (3-1-0) Cr.-
4
DEPARTMENT
OF
COMPUTER
SCIENCE
&
ENGINEERING, IT
Veer Surendra Sai University of Technology
Burla-768018
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Lecture Notes on Internet and Web Technology-I, Lecture notes of Network Technologies and TCP/IP
Lecture notes on Internet and Web Technology-I, covering topics such as Internet overview, network hardware and software, packet switching, IP addressing, TCP fundamentals, and computer networks. It also includes an introduction to data communication and the classification of computer networks based on transmission mode and time in transmission type.
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COMPUTER NETWORKS
Lecture Notes
Course Code - BCS-
Course Name - INTERNET & WEB TECHNOLOGY-I (3-1-0) Cr.- 4
DEPARTMENT OF COMPUTER SCIENCE & ENGINEERING, IT
Veer Surendra Sai University of Technology
Burla-
INTERNET & WEB TECHNOLOGY – I
Lecture 1 Internet Overview, Evolution of Internet
Lecture 2 Internet component – Types of network
Lecture 3 (^) Internet component- Network Hardware
Lecture 4 Internet component- Network Software
Lecture 5 Packet Switching Fundamentals and Circuit Switching, Efficiency
Lecture 6 Packet Switching : Datagram Switched Network
Lecture 7 Packet Switching : Virtual Circuit-switched Network
Lecture 8 Packet Switching : Virtual Circuit-switched Network, Efficiency
Lecture 9 Packet Switching ve rsus CircuitSwitching,Internet Standards
Lecture 10 (^) Internet Standards : IETF, ITU IEEE, ATM Forum
Lecture 11 Internet Protocol : IP format
Lecture 12 Internet Protocol: IP Addressing
Lecture 13 Subnet and Subnet Mask
Lecture 14 Class-less Address, Superneting
Lecture 15 IPv6 Datagram Format , IPv4 vs IPv
Lecture 16 TCP Fundamentals: TCP 3 way Hand shaking
Lecture 17 TCP/IP: routing.
Lecture 18 Networking protocols: Network Protocol Overview: Networking protocols in TCP/IP
Lecture 19 Networking protocols in TCP/IP –ARP,RARP,BGP,EGP
Lecture 20 NAT, DHCP
Module I (10 lecture)
Internet overview
The Internet is a giant network of networks.
- A network may include PCs, and other devices like servers or printers.
- A network is connected through a communication channel.
- Early research was performed by the US Department of Defense in 1962. This research group established ARPAnet (Advanced Research Project Agency) in order to connect the US Defense Department network.
What did the Internet come from?
- Original aim was to create a network that would allow users of a research computer at one university to be able to ‘talk to’ research computers at other universities.
- A side benefit of ARPAnet’s design was that, because messages could be routed or rerouted in more than one direction, the network could continue to function even if parts of it were destroyed in the event of a military attack or other disaster.
- The users of the Internet took a direction of their own.
History of the Internet
- The first long distance communication took place in 1965 between a computer in MIT and California.
- In 1969, four computers clients were connected together via ARPAnet.
How old is the Internet?
- Leonard Kleinrock is accredited with the idea of packet switching, which describes how data can be sent across a network. The Ethernet was developed by Xerox during this period. This was inspired by Robert Metcalfe’s PhD on ‘packet networks’.
- An Ethernet is a protocol for describing how computers can be connected in a LAN (Local Area network).
- Through the use of Ethernet and ARPAnet the US were able to develop a working network.
- In the late 1970s and early 1980s other networks were developed, e.g. CSNET, USNET and BITNET. In 1973 Vint Cerf and Bob Kahn created the TCP/IP communication protocols.
- TCP/IP: Transfer Control Protocol/Internet Protocol is a set of rules that describe how computers can communicate over a network.
- To send information over the Internet, a computer packs data into Internet Protocol (IP) packets and labels them with the correct address. They are then sent across a packet switched interconnected network.
Introduction to Data Communication
The term telecommunication means communication at a distance. The word data refers to information presented in whatever form is agreed upon by the parties creating and using the data. Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable.
Computer Network
A network is a set of devices (often referred to as nodes) connected by communication links. A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network.
Software modules in one system are used to communicate with one or more software modules in the distance System. Such interfaces across a distance are termed as “peer-to-peer” interfaces; and the local interfaces are termed as “service” interfaces. The modules on each end are organized as a sequence of functions called “layers”. The set of modules organized as layers is also commonly called a “protocol stack”.
Over the years, some layered models have been standardized. The ISO Open Systems Interconnection (ISO/OSI) layered model has seven layers and was developed by a set of committees under the auspices of International Standards Organization (ISO).
Classification of Computer Networks
- Server Based Connection Most networks have a dedicated server. A dedicated server is a computer on a network which functions as a server, and cannot be used as a client or a workstation. A dedicated server is optimized to service requests from network clients. A server can control the clients for its services.
4. Based on Geographical location
- Local Area Networks (LAN) LAN is a small high speed network. In LAN few numbers of systems are interconnected with networking device to create network. As the distance increases between the nodes or system it speed decreases. So it is limed to few meters only. Networks which cover close geographical area. LAN used to link the devices in a single office, building or campus. It provides high speeds over short distance. Systems are connecting directly to Network. The LAN is owned by private people.
- Wide Area Network (WAN) WAN is collection of network (or LAN). This network speed is less than the LAN network speed.WAN network connect systems indirectly. WAN spread over the world may be spread over more than one city country or continent. Systems in this network are connected indirectly. Generally WAN network are slower speed than LAN’s. The WAN network are owned or operated by network providers. If it is owned by a single owner then it is called Enterprise network. Often these types have combination of more than one topology.
- MAN (Metropolitan Area Network) Metropolitan area network is an extension of local area network to spread over the city. Itmay be a single network or a network in which more than one local area network canshare their resources.
5. Based on Reliability
Reliability is maintained by authentication.
- Connection-oriented
This type of communication establishes a session connection before data can be sent. This method is often called a "reliable" network service. It can guarantee that data will arrive in the same order.
- Connection less This type of communication does not require a session connection between sender and receiver for data transfer. The sender simply starts sending packets to the destination. A connectionless network provides minimal services.
Topology
Topology refers to physical layout including computers, cables, and other resources; it determines how components communicate with each other.
Today’s network designs are based on three topologies:
- Bus consists of series of computers connected along a single cable segment
- Star connects computers via central connection point or hub
- Ring connects computers to form a loop All computers, regardless of topology, communicate by addressing data to one or more computers and transmitting it across cable as electronic signals. Data is broken into packets and sent as electronic signals that travel on the cable. Only the computer to which the data is addressed accepts it.
Protocol
Protocols mean set of rules. It is a formal description of message formats and the rules two or more machines has follow to exchange messages. The key elements of a protocol are syntax, semantics and timing.
- Syntax Syntax refers to the structure or format of the data, meaning the order in which they arepresented.
- Semantics Semantics refers to the meaning of each section of bits.
- Timing Timing refers to when data should be sent and how fast it can be sent.
Access networks can be loosely divided into three categories:
- Residential access networks, connecting a home end system into the network.
- Institutional access networks, connecting an end system in a business or educational institution into the network.
- Mobile access networks, connecting a mobile end system into the network
Core Networks:
Core network connects all the routers to each other and ISP (Internet service provider). It is a main back bone for internet. Core network uses circuit switching and packet switching for data transmission.
ISPs:(Internet Service Provider)
In internet bottom-to-top the hierarchy consists of end systems (PCs, workstations, etc.)connected to local Internet Service Providers (ISPs). The local ISPs are in turn connected to regional ISPs, which are in turn connected to national and international ISPs. The national and international ISPs are connected together at the highest tier in the hierarchy.
Let's begin at the top of the hierarchy and work our way down. Residing at the very top of the hierarchy are the national ISPs, which are called National Backbone Provider (NBPs). The NBPs form independent backbone networks that span North America (and typically abroad as well). Just as there are multiple long-distance telephone companies in the USA, there are multiple NBPs that compete with each other for traffic and customers. The existing NBPs include internetMCI, SprintLink, PSINet, UUNet Technologies, and AGIS. The NBPs typically have high-bandwidth transmission links, with bandwidths ranging from 1.5 Mbps to 622 Mbps and higher. Each NBP also has numerous hubs which interconnect its links and at which regional ISPs can tap into the NBP.
The NBPs themselves must be interconnected to each other. To see this, suppose one regional ISP, say MidWestnet, is connected to the MCI NBP and another regional ISP, say EastCoastnet, is connected to Sprint's NBP. How can traffic be sent from MidWestnet to EastCoastnet? The solution is to introduce switching centers, called Network Access Points (NAPs), which interconnect the NBPs,
thereby allowing each regional ISP to pass traffic to any other regional ISP. To keep us all confused, some of the NAPs are not referred to as NAPs but instead as MAEs (Metropolitan Area Exchanges).
Component of Internet:
A network (or internet) is formed using Hardware (or network device) and network software or Application and protocols.
Hardware or Network device:
1. Hub: - It is uses to connect systems or nodes or networks. - It has direct connection to a node (point to point connection). - It suffers from high collision of data, results to data loss. - A hub takes data from input port and retransmits the input data on output port. 2. Repeater: - A repeater is a device which regenerates or amplifies the data or signal so that it can be travel to the other segment of cable. - It is use to connect two networks that uses same technology and protocol. - It does not filter or translate any data. - Work in physical layer. 3. Bridge: - It is used to connect two networks. - It divides the collision domain based on number of ports or interface present in a bridge. - It uses the packet switches that forward and filter the frames using LAN destination address. - Bridge examines the destination address of frame and forwards it to the interface or port which leads to the destination. - It uses the routing table for routing frame from one node to other using MAC address. - It works in Data Link Layer. 4. Switch : - It is similar to bridge. It has more number of interfaces as compared to bridge. - It allows direct communication between the nodes.
- World Wide Web - This is largest, fastest growing, part of the Internet, the part for which Internet browsers like Netscape’s Navigator and Microsoft’s Explorer were designed. Business is the leading factor fueling the rapid growth of the Web making information, advertising, and product ordering readily available to everyone with Web access.
- TCP/IP
- Browser
WAN Protocols
- Frame Relay Frame relay is used to connect large number of sites in the network because it is relatively inexpensive to do so. The service provider gives you a frame relay circuit and is charged for the amount of data and the bandwidth you use as oppose to T1 circuit that charges with a flat monthly rate whether you use partial bandwidth or the full bandwidth regardless. Frame relay is a high performance WAN protocol that operates at the Data Link layer and the Physical layer of the OSI model.
- Integrated Services Digital Network (ISDN) Integrated Services Digital Network (ISDN) is designed to run over existing telephone networks. It can deliver end to end digital service carrying voice and data. ISDN operates at OSI model, physical layer, data link layer and network layer. It can carry multimedia and graphics with all other voice, data services. ISDN supports all upper layer protocols and you can choose PPP, HDLC or LAPD as your encapsulation protocol. It has two offerings, Primary rate which is 23B+D channels. 23, 64 kbps and one 64kbps mainly used for signaling. The other is the Basic Rate which has 2B+D channels two 64kbps and one 16kbps. At data link layer ISDN supports two protocols; LAPB and LAPD. LAPB is used to mainly transfer data from upper layers and has three types of frames. I-Frames carry upper layer information and carries out sequencing, flow control, error detection and recovery. S- Frames carry control information for the I-frame. LAPD provides an additional multiplexing function to the upper layers enabling number of network entities to operate over a single physical access. Each individual link procedure acts independently of others. The multiplex procedure combines and distributes the data link channels according to the address information of the frame. Each link is associated with a specific Service Access Point (SAP), which is identified in the part of the address field.
- High Level Data Link Control (HDLC) High Level Data Link Control (HDLC) is a bit oriented data link layer frame protocol that has many versions similar to LAP, LAPB, and LAPD. CISCO routers default encapsulation is HDLC, but it is proprietary to CISCO.
OSI model
OSI (Open System Interconnection), developed by the International Organizationfor Standardization (ISO), was the solution designed to promote interoperabilitybetween vendors. It defines architecture for communications that support distributed processing. The OSI model describes the functions that allow systemsto communicate successfully over a network. Using what is called a layeredapproach, communications functions are broken down into seven distinct layers.
Figure 2 Interaction between layers in OSI model.
Layer 2: Data Link Layer
▪ It divides the data into number of frames.
▪ It uses the MAC address for sending frames from one node to other.
▪ It provides flow control, error control and access control.
Layer 3: Network Layer
▪ It divides data into number of packets.
▪ It uses IP address for routing packets to their destination.
▪ It provides end to end connection.
Layer 4: Transport Layer
▪ It divides message into segments and also reassemble the segments to create
original message.
▪ It can be either connection-oriented or connectionless.
▪ It uses service-point address or port address for process to process
communication.
▪ Flow control and error control also provided by transport layer.
Layer 5: Session Layer
▪ Session Layer establishes, maintains and synchronizes the interaction among
communicatingsystems.
Layer 6: Presentation Layer
▪ It is concerned with the syntax and semantics of the
informationexchangedbetweentwo systems.
▪ It translates information from text/numeric into bit stream.
▪ It also encrypts the information for security purpose and compress the
information to reduce the number of bits in the information.
Layer 7: Application Layer
▪ It provides the interface to the end user and supports for services such as Email,
file transfer and distributed information service.
OSI Model and Protocol stack
Layer Protocol
Application HTTP, FTP, SMTP,TELNET
Presentation JPG, GIF, MPEG,
Session TCP 3-way Handshaking
Transport TCP, UDP
Network IP, IPX
Data Link Ethernet, Token Ring, HDLC
Physical X.21, RS-232, DS, DS
TCP/IP model
- TCP/IP protocol suite was developed before the OSI model. - TCP/IP is a set of protocols developed to allow cooperating computers to share resources across a network. - In 1969 the Defense Advanced research projects Agency (DARPA) funded a research and development project to create an experimental packet switching network. This network is called ARPANET. - In 1975 the ARPANET was converted from an experimental network to an operational network, and the responsibility for administering the network was given to the Defense Communication Agency (DCA). - The TCP/IP protocols were adopted as Military Standards (MIL STD) in 1983, and all hosts connected to the network were required to convert to the new protocols. - DARPA funded to implement TCP/IP in BerkelyUnix. - In 1983, the old ARPANET was divided into MILNET and smaller ARPANET. The Internet was used to refer to the entire network; MILNET and ARPANET.
Advantages of TCP/IP
Open protocol standards, freely available and developed independently from any specific computer hardware or operating system. A common addressing scheme which is enable to connect the most widely used networks. It may use any protocols. It connects dissimilar systems. It provides client/server framework. It provides access to the Internet
Differences of the OSI and TCP/IP models
- Packet Switched Networks A. Datagram Networks B. Virtual- circuit Networks
- Message Switched Networks
1. Circuit Switched Network:
- In circuit-switched networks, a dedicated path is needed for communication between the end systems are reserved for the duration of the session.
- Each connection uses only one dedicated channel on each link.
- Each link is divided into n channels by using FDM (frequency division Multiplexing) or TDM (Time Division multiplexing).
In the above figure one link is divided into n channel (here n=3).A circuit switched network requires following three phase during the session.
- Setup Phase: First of all two system needs to create dedicated circuit or path for communication. For example in figure xxx when system A needs to connect to system M, it sends a setup request that includes the address of system M, to switch I. Switch I finds a channel between itself and switch II that can be dedicated for this purpose. Switch I then sends the request to switch II, which finds a dedicated channel between itself and switch III. Switch III informs system M of about system A.
Figure 5A trivial circuit-switched network
To establish a path system M must send an acknowledgement for the request of A. Only after system A receives this acknowledgement the connection is established. Only end to end addressing is required for establishing connection between two end systems.
- Data Transfer Phase After the establishment of the dedicated path (channels), the two systems can transfer data.
- Teardown Phase When one of the systems needs to disconnect, a signal is sent to each switch to release the resources.
Not efficient because the link is reserved and can’t be used by other system during the connection. Minimum delay in data transfer.
Example:L et us consider how long it takes to send a file of 640 Kbits from host A to host B over a
circuit-switched network. Suppose that all links in the network use TDM with 24 slots and have bit rate
1.536 Mbps. Also suppose that it takes 500 msec to establish an end-to-end circuit before A can begin
to transmit the file. How long does it take to send the file?
Each circuit has a transmission rate of (1.536 Mbps)/24 = 64 Kbps, so it takes (640 Kbits)/(
Kbps) = 10 seconds to transmit the file. To this 10 seconds we add the circuit establishment time,
giving 10.5 seconds to send the file. Note that the transmission time is independent of the number links:
the transmission time would be 10 seconds if the end-to-end circuit passes through one link or one-
hundred links.
2. Packet Switched Networks
2. A. Datagram Networks
- In packet switched network message is divided into number of packets. Each packet is of fixed size defined by network or protocol.
- Datagram switched network is also known as Connectionless packet switching
- There is no dedicated link between source and destination.