INTRODUCTORY INFORMATION TECHNOLOGY COMMUNICATING OVER NETWORKS Faramarz Hendessi
INTRODUCTORY INFORMATION TECHNOLOGY Lecture 6 Fall 2010 Isfahan University of technology Dr. Faramarz Hendessi
Overview Understand network communication. Decipher computer addressing. Network communication protocols. Network designing.
Understand Network Communication A sender, a receiver, a message, and a medium are required for network communication. In order to communicate effectively, it is essential that the systems on a network use the same language.
Understand Network Communication Computer signals Messages
Computer Signals Digital signal and analog signal are the two forms in which computer signals are transmitted. When two computers communicate on a network, they exchange digital signals. Each signal or digit is represented by a distinct state.
Computer Signals An analog signal
Computer Signals The presence of an electrical signal is considered as on, and is represented by the digit one. The absence of an electrical signal is considered as off, and is represented by a zero. A system that uses zeros and ones is called a binary system.
Computer Signals A modem is required to convert a digital signal into an analog signal, and vice versa. The process of converting digital signals into analog signals is called modulation. The process of converting analog signals back into digital signals is called demodulation.
Computer Signals Bits: The term bit is used to represent a single instance of a digital signal. These can also be represented by other medium states, such as the relative signal strengths of light pulses or radio waves. A bit becomes important when it is combined with other bits to create different characters.
Computer Signals Bytes: Eight bits make a byte. A byte can be used to represent up to 256 characters, digits, or symbols on a computer.
Messages When a computer communicates with itself or with other computers, it assembles the characters into meaningful data. The data can then be easily received and interpreted by the receiving computer.
Decipher Computer Addressing Unique address. Physical address. Hexadecimal notation. Node address. Network addresses and their implementation.
Unique Address A unique address with an exact name and storage path is required for storing and retrieving data accurately over a network. Network addressing is handled by ensuring that each address is unique.
Physical Address The physical address is the first element of a computer s network address. It is a special serial number assigned to a component installed inside the computer. The numbers are controlled by the networking industry s regulating organization, the Institute of Electrical and Electronics Engineers (IEEE).
Physical Address The equipment manufacturer requests a block of unique 48-bit binary numbers and assigns a separate number to each network interface card (NIC) that they create. The first 24 bits of the MAC address assigned to a NIC are set by the IEEE to identify the manufacturer.
Physical Address The physical address, also know as the Media Access Control (MAC) address, is a means by which the computer gains access to the networking medium. The physical (or MAC) address is also sometimes referred to as the hardware address.
Hexadecimal Notation Hexadecimal notation (hex) is a numbering system that uses 16 alphanumeric characters instead of the usual ten numeric digits. Hex is a shorthand for writing binary numbers. A single hex digit is used to represent four digits of a binary number.
Node Address A unique node address is required for every computer on a network. Adding node numbers to the MAC helps locate the randomly generated node numbers. Each node address is useful within the specific network to which it is attached.
Network Addresses and Their Implementation The network address is a combination of the node address and the MAC address. The source address and the destination address are required to transmit data effectively. The source address specifies where the transmitted information originates.
Network Addresses and Their Implementation The destination address specifies the information s destination. Both the source and destination addresses are then added to the data being transmitted to make sure that the message is routed properly.
Network Addresses and Their Implementation Directing messages to the specific computer
Network Communication Protocols Network communication decisions. Layered communication. Internet communication. Intranet/Extranet communication.
Network Communication Decisions Language: A set of language rules developed to effectively communicate over a network is called a protocol. NetBIOS (Network Basic Input/Output System) and NetBEUI (NetBIOS Extended User Interface) were two networking languages used earlier.
Network Communication Decisions Broadcasting versus routing: Broadcasting involves passing digital messages over the network medium. Routing involves deciding the recipient of the message and sending it to them directly.
Network Communication Decisions Message format - Formatting refers to combining mutually acceptable characters in such a way that messages can be exchanged.
Layered Communication The International Standards Organization (ISO) suggested the use of the Open Systems Interconnection (ISO) model to explain network communication. The OSI model s standards are open and made available to everyone to enable interconnectivity of different systems. The model simplifies complex networking activities by grouping the steps into seven layers.
Layered Communication Layers in the OSI Model
Layered Communication Layers in the OSI Model
Internet Communication Transmission Control Protocol/Internet Protocol (TCP/IP). User Datagram Protocol (UDP). Domain Name Service (DNS). File Transfer Protocol (FTP). Simple Mail Transfer Protocol (SMTP).
Transmission Control Protocol/Internet Protocol (TCP/IP) TCP/IP is the most widely used protocol, and acts as the Transport/Network layer protocol. The TCP makes sure that the data is correctly sized, properly put in packets, and sequenced back in the right order upon receipt. The TCP, also known as a connection-oriented protocol, links the Application layer to the Network layer.
Transmission Control Protocol/Internet Protocol (TCP/IP) The IP is a set of rules that is concerned with sending a message to the correct address and is, therefore, called a connectionless protocol. The IP is also responsible for the creation and maintenance of an addressing scheme, known as the IP address. IP operates at the Network layer.
Transmission Control Protocol/Internet Protocol (TCP/IP) Each IP address is a unique 4-byte (or 32-bit) number, and each byte is separated by a decimal point. IP addresses can be used as static assignments to individual computers, or can be assigned dynamically.
Every machine needs an address Address identifies one network interface on a host Every interface needs a unique address An IP address is a 32 bit number Written as four fields (octets), 8 bits each, separated by dots Called dotted decimal notation Example: 147.134.2.20
Classes of IP addresses Class A Theoretically only 127 class A s 16.7 million hosts Class B 16,384 class B s 65,000 hosts Class C 2.09 million class C s 256 hosts
Class A First octets with a decimal number between 1 and 127 Uses the first octet to represent the network address and the other three octets for host addresses Cannot use 127.x.y.z as it is reserved for loopback testing 127.0.0.1 is localhost
Class B First octets with a decimal number between 128 and 191 Uses the first two octets to represent the network address and the last two octets for the host addresses
Class C First octets with a decimal number between 192 and 223 Uses the first three octets to represent the network address and the last octet to develop host addresses
Class D Decimal values between 224 and 239 in the first octet Class D addresses are multicast addresses Allows several hosts to listen in on the same address at the same time
Class E Decimal range of 240-255 Reserved addresses and and invalid host addresses that are used for experimental purposes
Private Addresses These are nonroutable addresses Class A 10.0.0.0 through 10.255.255.255 Class B 172.16.0.0 through 172.31.255.255 Class C 192.168.0.0 through 192.168.255.255
Private addresses. Use for Network Address Translation (NAT) or Routing and Remote Access (RRAS) to connect an inside network with one routable IP address That s what we are doing in class!
Classless Inter-Domain Routing (CIDR) Developed to increase the efficiency of address allocation and to alleviate overloaded Internet routers Represents addresses in traditional notation, but highlights the network portion with a slash followed by a number 192.168.0.1/24 The number after the is the number of bits that represent the network portion of the IP address
Subnet Mask A 32-bit address that looks like an IP address but actually points out to IP which part of the IP address is the network portion Every IP address must have a subnet mask Determines whether the packet is on the same local network or on a remote network
Standard subnet masks Class A 255.0.0.0 Class B 255.255.0.0 Class C 255.255.255.0
Custom subnet masks Use to divide your network into several smaller networks for easier management Handout at a later time on how to do this
Address assignment Static Manually entered Dynamic A DHCP server is configured with a pool of addresses to lease out to hosts Discover Offer Request acknowledgment
DHCP You can reserve an IP address based on it s MAC address To ensure a machine always gets the same address To save an address in a pool for a particular machine
DHCP lease time Long leases mean less network traffic, but those addresses are not available for use during the lease time Up to the network administrator to set, depending on the devices on the network, their portability, network traffic, etc. ** The DHCP is a set of rules that allow a group of computers to effectively lease IP numbers to network members when required.
User Datagram Protocol (UDP) UDP is a connectionless protocol that operates at the Transport layer. This protocol does not have to open a connection with the receiver and it does not have to carry out any error correction. UDP does not perform any checks to ensure the receipt of data, so it never carries out automatic retransmissions.
Domain Name Service (DNS) The DNS is used for locating resources on the Internet. It operates at the Application layer. The DNS server uses the IP address to link to the Uniform Resource Locator (URL) concerned. Examples of domain names include com, net, org, edu, gov, and mil.
File Transfer Protocol (FTP) The FTP is used for transferring files over the Internet. It operates using a client at the Application layer and a server at the opposite end.
File Transfer Protocol (FTP) It is also possible to send files to an FTP site, making the process of exchanging large pieces of information fast and simple. Some FTP servers allow anonymous logins, while others require passwords and proper authentication.
Simple Mail Transfer Protocol (SMTP) SMTP is a set of rules that regulates the transfer of e-mail over the Internet. The Post Office Protocol (POP) or the Internet Message Access Protocol (IMAP) is required to read e-mail.
Simple Mail Transfer Protocol (SMTP) Graphic or document attachments are handled by an SMTP extension called Multipurpose Internet Mail Extensions (MIME). The MIME converts each attachment into a coded form, similar to text, for transfer over SMTP.
Intranet/Extranet Communication Intranet communication refers to using Internet communication techniques without using an Internet connection. When two or more Intranets are networked without being connected to the Internet, it is called an Extranet.
Network Designing Network needs. Network choices. Network layout.
Network Needs Administering a network involves: Ensuring that the systems are up and running at any given point in time, while making them easy for a user to operate. Maintaining the system s operation with the minimum amount of downtime.
Network Choices Network budget The total cost of the network must be less than the projected earnings to impose an economic limit for installing and maintaining a network. Network security The required security must be essentially added to the network to avoid any kind of security issues.
Network Choices The following aspects must be considered while choosing a network s users: The network s users should be trained and be capable of handling the system. The number of users who would be accessing the system should be defined at a given point in time.
Network Choices The following aspects must be considered while choosing a network s users (continued): It must be ensured that when the network access is at its peak, the users are able to obtain the services immediately after logging in. The maximum capacity of the network should be designed to handle a user s request.
Network Choices Network application: It is essential to know how and why the network would be used. These facts help determine the means for producing the network s output and the tools that go into producing it.
Network Choices Network growth: Any system should allow for future growth, and should include added capacity for incorporating new resources into the network. Allowances should also be provided for technological advances.
Network Layout The physical layout or the geometric pattern formed by the arrangement of interconnected computers is referred to as topology. Bus, ring, and star are the three most common types of physical topologies.
Network Layout Bus topology
Network Layout Ring topology
Network Layout Star topology
Summary Communication involves a sender, a receiver, a message, and a medium. A bit is a single digit and a byte is made up of eight bits. A system that uses only zeros and ones is called a binary system.
Summary The ISO recommends the use of the OSI model to connect dissimilar networking components. The needs of all the networked resources should be adequately considered while panning the network. Topology refers to the physical layout or arrangement of computers in a network.