Information Technology Computer Networking Dr John P Abraham

Information Technology Computer Networking Dr. John P. Abraham, University of Texas Pan American

Computer network architectures – the client server • all communication happens between the server and the client only. • A client does not communicate directly with another client. – If a client wishes to share a file with another client, it must place the file in a commonly shared area at the server. • In case of an application, the client makes the request and the server processes the request and returns the result to the client. – the peer-to-peer • any node can act as a server as well as a client. • Only very limited security is available on a peer-to-peer network. Dr. John P. Abraham, University of Texas Pan American

Components used in a Computer Network – Computers – Communication ports – Cables – Hubs or switches – Routers – The network software. Dr. John P. Abraham, University of Texas Pan American

Computers in a Client/Server architecture – Must be be robust • must be able to run for months or years without being shut down. – Must be fast enough to handle many requests from all the requests from the clients. – Must have large fast hard drives to store information for all use – Must have enough memory to cache all the directory informati as well as most used pages. – The computers must be reliable in case of power failures and hardware failures: • sufficient redundancy must exist. Dr. John P. Abraham, University of Texas Pan American

Example of Types of Servers • • Fileserver print server database server domain name server communication server DHCP server Name Server Dr. John P. Abraham, University of Texas Pan American

Communication ports • Network may be done through any communication ports such as serial, parallel, network cards, etc. • Most common Network Cards used today are Ethernet and Token Ring. Dr. John P. Abraham, University of Texas Pan American

Network Interface Card • Plug and play (PNP). – Open the computer, install the card, and insert the driver disk. • Legacy cards: • the interrupt request line (IRQ), base memory address, and the base I/O port must be manually set up on the card by setting the jumpers or DIP switches, or through the use of the manufacturer provided setup software. • Speed: 10 Megabits per second (Mbps), 100 Mbps (Fast Ethernet) or 1000 Mbps (Gigabit Ethernet) depending on the card. Dr. John P. Abraham, University of Texas Pan American

Connectors on NIC • The connector on most Ethernet cards today is the RJ-45 having 8 pins. • Older Ethernet cards may have a Bayonet Nut Connector (BNC), an Attachment Unit Interface (AUI), and/or a RJ-45 connector. A jumper or switch will specify the type of connector used. Dr. John P. Abraham, University of Texas Pan American

Network Addresses • Every computer connected to a network should have two unique identifying numbers, a physical address and an Internet Protocol (IP) address. – The physical address • a 6 Byte number, is encoded on a ROM chip on the Ethernet card at the time of manufacturing – the IP address • A 4 byte address • is used to send messages to the outside world. The physical address. • configured on each machine. Dr. John P. Abraham, University of Texas Pan American

Hub/Switch • A Hub or switch connects cables from different nodes together. When purchasing them the number of ports required and the speed of transmission must be specified. • An active hub amplifies all signals received and sends the amplified signals on all its ports. • Passive hubs are signal splitters and are used only in wiring panels. • Even though a little more expensive, a switch will provide faster communication and great deal of diagnostic features. • Switches provide link management through physical address identification. Dr. John P. Abraham, University of Texas Pan American

Hubs/Switches • As the network grows, multiple switches or hubs can be connected with each other using an uplink port or a direct connect cable. • Most modern switches have the auto-sensing feature, which will allow any port to work as an uplink. • The best location for a switch or hub is a centrally located closet to which cables from all computers are brought. Dr. John P. Abraham, University of Texas Pan American

Network Cabling • Cabling is the most time consuming part of networking, particularly when cables need to be hidden inside the walls. • For that reason it is advisable to have the cables installed or conduits placed at the time of the building construction. • To hide wires inside existing buildings, a tape fish will be needed. • It may be well worth the time to investigate the wireless technology, particularly when a small area is being networked. Dr. John P. Abraham, University of Texas Pan American

Network cabling 2 • Three types of cables are used today: coaxial, twisted pair, and fiber-optic. • Twisted pair cables either can be unshielded or shielded with a foil. • Unshielded twisted pair (UTP) cable can transmit 10 Megabits per second and the shielded can transmit more than 100 Mbps, perhaps all the way up to 1000 Mbps. • Wires in each pair are twisted to reduce cross-talk and minimize the effect of external electromagnetic interference. • Twisted pair cables are categorized into five categories, from Cat 1 to Cat 5, based on the bandwidth capabilities. • The maximum length of a segment is 100 meters. Dr. John P. Abraham, University of Texas Pan American

Network Cabling 3 • The UTP cable has 4 pairs of color-coded (orange, green, blue and brown) wires. • The color of one of the wires in a pair will be solid and the other will be striped with white. • Pins in the RJ-45 jack are numbered from 1 to 8. • When two computers are connected directly without the use of a hub or a switch some wires need to be crossed (Transmit to Receive). Such a cable is called a crossover cable. Crossover cables need to be used when two hubs or switches that lack uplink ports are connected together. Dr. John P. Abraham, University of Texas Pan American

T-568 A Straight-Through Ethernet Cable Dr. John P. Abraham, University of Texas Pan American

T-568 B Straight-Through Ethernet Cable Dr. John P. Abraham, University of Texas Pan American

RJ-45 Crossover Ethernet Cable Dr. John P. Abraham, University of Texas Pan American

Crossover cable Dr. John P. Abraham, University of Texas Pan American

Network Protocols • 7 layer OSI model • 5 layer TCP/IP suite • There exists three TCP/IP network environment today, Novell Networking, Microsoft Windows Networking, and the UNIX/LINUX networking. Dr. John P. Abraham, University of Texas Pan American

Network Operating Systems • The Novell Networking incorporates its original IPX/SPX protocol suite as well as the TCP/IP protocol suite. • Windows and Unix operating systems include TCP/IP networking as part of their operating system. • All versions of Windows provide the peer-to-peer networking capabilities, while the NT, 2000 professional, and the XP professional provide for Client/Server architecture. • The UNIX/LINUX has consistently adhered to the Client/Server architecture. Dr. John P. Abraham, University of Texas Pan American

Windows peer-to-peer networking • may use the TCP/IP protocol suite or some other simpler protocols such as the Net. BIOS and the Net. BEUI. • The Net. BIOS, an application program interface (API) extends the BIOS to include the support for I/O calls over a network. • The Net. BIOS Extnded User Interface (Net. BEUI), developed by IBM and Microsoft, is the protocol used by Windows Workgroup networking. Dr. John P. Abraham, University of Texas Pan American

Windows peer-to-peer networking • Net. Bios is non-routable, therefore could not reach beyond the local physical network. • It does not require an IP address, rather works with the name registration within a workgroup. • In the newer Windows operating systems, the Net. BEUI is encapsulated inside the TCP/IP, referred to as Net. BIOS over TCP/IP (NBT), and uses the IP address. Dr. John P. Abraham, University of Texas Pan American

Configuring the windows network • From the control panel’s, local area network, add a NIC if it does not show up already. Insert the appropriate driver software. • Next Choose the protocols to be bound to the network card, Net. Bios, TCP/IP, IPX/SPX, Appletalk, etc. • Set up the properties for the protocol you chose. For example, for the TCP/IP, you will asked to either obtain the addresses automatically or type in the IP Address, mask, default gateway, and DNS. The default gateway is the address of the host through which internetworks can be reached (a router or a computer that shares Internet). DNS is the server that provides the IP address given a domain name. • Install the client services and give your computer a name and a group. • Finally, you may want to share your resources. Dr. John P. Abraham, University of Texas Pan American

Printing on a network • Network ready printers come already installed with a NIC. Configure an IP address for the printer either using the printer console buttons or using software provided by the manufacturer. • Under Windows check the list of printer ports for the TCP/IP port. If it is not there add it giving the appropriate IP address of the network printer. • Install the printer driver to complete the printer installation. • Alternatively, print queues can be setup on a print server. A client can then print to a print queue. Dr. John P. Abraham, University of Texas Pan American

Linux Network • The Linux will automatically detect the network card during installation and the device name “eth 0” will be assigned to it. • Using the ifconfig, assign the IP address and subnet mask to the interface. • Next edit the /etc/hosts file and add the IP addresses and the corresponding symbolic name such as cs. panam. edu. • To convert a symbolic name to the IP address try running the nslookup (example nslookup panam. edu). • The nslookup command uses the /etc/resolv. conf file to find the host runs the name server software. The resolv. conf file needs to be edited to include the domain name server (DNS). For example, the file should include these lines: • domain cs. panam. edu • nameserver 129. 113. 132. 237 • search cs. panam. edu Dr. John P. Abraham, University of Texas Pan American

Subnet Masks • Introduction – Explosive growth of the Internet – Two problems • Exhaustion of IP addresses • Routing Table growth Dr. John P. Abraham, University of Texas Pan American

Exhaustion of IP addresses • Hierarchical assignment – example - telephone numbers • Random assignment – example - IP addresses Dr. John P. Abraham, University of Texas Pan American

Growth of routing tables • • routing table defined reason for growth 1990 - 5000 routes 1995 - 35000 routes Dr. John P. Abraham, University of Texas Pan American

IP address defined • • 32 bit number octets network portion host portion Dr. John P. Abraham, University of Texas Pan American

Classes of IP addresses Dr. John P. Abraham, University of Texas Pan American

Usable net and host addresses • all zeros – this network – this computer • all ones – every host – broadcast • 2 n-bits-2 Dr. John P. Abraham, University of Texas Pan American

# of usable networks and hosts Available Number Class bits in network Number of networks Available bits in host of hosts A 7 128 24 16, 777, 214 B 14 16, 384 16 65, 534 C 21 2, 097, 152 8 254 Dr. John P. Abraham, University of Texas Pan American

Subnet masks • purpose • Advantages • Disadvantages Dr. John P. Abraham, University of Texas Pan American

Anding with subnet masks • • • host 129. 113. 200. 111 sends a packet to destination 129. 113. 200. 120. AND 10000001. 01110001. 11001000. 01111000 destination address 11111111. 0000 subnet mask 10000001. 01110001. 11001000. 0000 destination on the same subnet 129. 113. 200. 0 – same as the source subnet address. This destination address is on the same physical subnet as the source address. Now let us change the destination address to 129. 113. 191. 121 and perform the same calculation: AND 10000001. 01110001. 10111111. 01101111 destination address 11111111. 0000 subnet mask 10000001. 01110001. 10111111. 0000 destination not on the same subnet 129. 113. 191. 0 – not same as the source subnet address. Dr. John P. Abraham, University of Texas Pan American

Case study • • • a small business firm with five departments each having twenty-five employees will need 125 nodes for computers and five for printers Choose the best fit from the following table: • • • Number of bits 2 3 4 5 6 Number of subnets or hosts 2 6 14 30 62 Dr. John P. Abraham, University of Texas Pan American

Subnet using 3 bits (mask=255. 224) • • Subnets in binary 201. 225. 5. 00100000 201. 225. 5. 01000000 201. 225. 5. 01100000 201. 225. 5. 10000000 201. 225. 5. 10100000 201. 225. 5. 11000000 Subnets in decimal 201. 225. 5. 32 201. 225. 5. 64 201. 225. 5. 96 201. 225. 5. 128 201. 225. 5. 160 201. 225. 5. 192 Dr. John P. Abraham, University of Texas Pan American

HOST ADDRESS FOR SUBNET 201. 225. 5. 64 • • Host addresses in binary for subnet 201. 225. 5. 64 • • 201. 225. 5. 01000001 201. 225. 5. 01000010 201. 225. 5. 01000011 201. 225. 5. 01000101 201. 225. 5. 01000110 201. 225. 5. 01000111 Host addresses in decimal 201. 225. 5. 65 201. 225. 5. 66 201. 225. 5. 67 201. 225. 5. 68 201. 225. 5. 69 201. 225. 5. 70 201. 225. 5. 71 • • 201. 225. 5. 01011110 … 201. 225. 5. 94 Dr. John P. Abraham, University of Texas Pan American

Subnet calculation given IP and Mask • Following our example let us take the IP address and subnet mask combination of 201. 255. 5. 67 and 255. 224. We need to use ANDing as given below to derive the subnet. • • 201. 225. 5. 01000011 201. 225. 5. 67 • AND 11100000 255. 224 • ------- • 01000000 201. 225. 5. 64 Dr. John P. Abraham, University of Texas Pan American

Following Slides from your textbook Dr. John P. Abraham, University of Texas Pan American

Chapter Goals • Compare and contrast various technologies for home Internet connections • Explain packet switching • Describe the basic roles of various network protocols • Explain the role of a firewall • Compare and contrast network hostnames and IP addresses 40 Dr. John P. Abraham, University of Texas Pan American

Networking Computer network A collection of computing devices connected in order to communicate and share resources Connections between computing devices can be physical using wires or cables or wireless using radio waves or infrared signals Can you name some of the devices in a computer network? 41 Dr. John P. Abraham, University of Texas Pan American

Networking Node (host) Any device on a network Data transfer rate (bandwidth) The speed with which data is moved from one place to another on a network 42 Dr. John P. Abraham, University of Texas Pan American

Networking Computer networks have opened up an entire frontier in the world of computing called the client/server model 43 Figure. Dr. John P. Abraham, University of Texas Pan American 15. 1 Client/Server interaction

Networking Protocol A set of rules that defines how data is formatted and processed on a network; i. e. , rules that allow client/server interaction File server A computer that stores and manages files for multiple users on a network Web server A computer dedicated to responding to requests (from the browser client) for web pages 44 Dr. John P. Abraham, University of Texas Pan American

Types of Networks Local-area network (LAN) A network that connects a relatively small number of machines in a relatively close geographical area Ring topology connects all nodes in a closed loop on which messages travel in one direction Star topology centers around one node to which all others are connected and through which all messages are sent 45 Bus topology nodes are connected to a single communication line that carries messages in both directions. Dr. John P. Abraham, University of Texas Pan American

Types of Networks Figure 15. 2 Various network topologies Ethernet The industry standard bus technology for localarea networks Dr. John P. Abraham, University of Texas Pan American

Types of Networks Wide-area network (WAN) A network that connects local-area networks over a potentially large geographic distance Metropolitan-area network (MAN) The communication infrastructures that have been developed in and around large cities Gateway One particular set up to handle all communication going between that LAN and other networks 47 Dr. John P. Abraham, University of Texas Pan American

Types of Networks 48 Figure 15. 1 Local-area networks connected across a distance to. Dr. John P. Abraham, University of Texas Pan American create a wide-area network

Internet Connections Internet backbone A set of high-speed networks that carry Internet traffic, provided by companies such as AT&T, Verizon, GTE, British Telecom, and IBM Internet service provider (ISP) A company that provides other companies or individuals with access to the Internet 49 Dr. John P. Abraham, University of Texas Pan American

Internet Connections Various technologies available to connect a home computer to the Internet Phone modem converts computer data into an analog audio signal for transfer over a telephone line, and then a modem at the destination converts it back again into data Digital subscriber line (DSL) uses regular copper phone lines to transfer digital data to and from the phone company’s central office Cable modem uses the same line that your cable TV signals come in on to transfer the data back and forth 50 Dr. John P. Abraham, University of Texas Pan American

Internet Connections Broadband A connection in which transfer speeds are faster than 768 kilobits per second – DSL connections and cable modems are broadband connections – The speed for downloads (getting data from the Internet to your home computer) may not be the same as uploads (sending data from your home computer to the Internet) 51 Dr. John P. Abraham, University of Texas Pan American

Packet Switching Packet A unit of data sent across a network Router A network device that directs a packet between networks toward its final destination Packet switching Messages are divided into fixed-sized, numbered packets; packets are individually routed to their destination, then reassembled Dr. John P. Abraham, University of Texas Pan American

Packet Switching Figure 15. 4 Messages sent by packet switching Take a message, break it into three packets, and simulate this process 53 Dr. John P. Abraham, University of Texas Pan American

Open Systems A logical progression. . . 54 Proprietary system A system that uses technologies kept private by a particular commercial vendor Interoperability The ability of software and hardware on multiple machines and from multiple commercial vendors to communicate Open systems Systems based on a common model of network architecture and a suite of protocols used in its implementation Dr. John P. Abraham, University of Texas Pan American

Open Systems Interconnection Reference Model A seven-layer logical break down of network interaction to facilitate communication standards Each layer deals with a particular aspect of network communication Figure 15. 5 The layers of the OSI Reference Model 55 Dr. John P. Abraham, University of Texas Pan American

Network Protocols • Network protocols are layered such that each one relies on the protocols that underlie it • Sometimes referred to as a protocol stack Figure 15. 6 Layering of key network protocols Dr. John P. Abraham, University of Texas Pan American 56

TCP/IP Transmission Control Protocol (TCP) Software that breaks messages into packets, hands them off to the IP software for delivery, and then orders and reassembles the packets at their destination Internet Protocol (IP) Software that deals with the routing of packets through the maze of interconnected networks to their final destination 57 Dr. John P. Abraham, University of Texas Pan American

TCP/IP User Datagram Protocol (UDP) An alternative to TCP that is faster but less reliable Ping A program used to test whether a particular network computer is active and reachable Traceroute A program that shows the route a packet takes across the Internet 58 Dr. John P. Abraham, University of Texas Pan American

High-Level Protocols Other protocols build on TCP/IP protocol suite Simple Mail Transfer Protocol (SMTP) used to specify transfer of electronic mail File Transfer Protocol (FTP) allows a user to transfer files to and from another computer Telnet used to log onto one computer from another Hyper Text Transfer Protocol (http) allows exchange of Web documents Which of these have you used? 59 Dr. John P. Abraham, University of Texas Pan American

High-Level Protocols Port A numeric designation that corresponds to a particular high-level protocol Figure 15. 7 Some protocols and the ports they use 60 Dr. John P. Abraham, University of Texas Pan American

MIME Types MIME type A standard for defining the format of files that are included as email attachments or on websites What does MIME stand for? Multipurpose Internet Mail Extension 61 Dr. John P. Abraham, University of Texas Pan American

Firewalls Firewall A gateway machine and its software that protects a network by filtering the traffic it allows Access control policy A set of rules established by an organization that specify what types of network communication are permitted and denied Have your messages ever been returned undelivered, blocked by a firewall? 62 Dr. John P. Abraham, University of Texas Pan American

Firewalls Figure 15. 8 A firewall protecting a LAN Dr. John P. Abraham, University of Texas Pan American 63

Network Addresses Hostname A name made up of words separated by dots that uniquely identifies a computer on the Internet IP address An address made up of four one-byte numeric values separated by dots that uniquely identifies a computer on the Internet Is there a correspondence between the parts of a hostname and an IP address? 64 Dr. John P. Abraham, University of Texas Pan American

Network Addresses Figure 15. 9 An IP address is stored in four bytes Class A: first byte for network address and three remaining bytes for host number Class B: first two bytes for network address and the last two bytes for host number Class C: first three bytes for network address and the last byte for host number Where does the host number come from? 65 Dr. John P. Abraham, University of Texas Pan American

Domain Name System Host number The part of the IP address that specifies a particular host (machine) on the network Yes, but what is it? Domain name The part of a hostname that specifies a specific organization or group Top-level domain (TLD) The last section of a domain name that specifies the type of organization or its country of origin 66 Dr. John P. Abraham, University of Texas Pan American

Domain Name System matisse. csc. villanova. edu Computer name Domain name 67 TLD Dr. John P. Abraham, University of Texas Pan American

Domain Name System Figure 15. 10 Top-level domains, including some relatively new ones Dr. John P. Abraham, University of Texas Pan American 68

Domain Name System Organizations based in countries other than the United States use a top-level domain that corresponds to their two-letter country codes Do you email someone in another country? Figure 15. 11 Some of the top-level domain names based on country codes 69 Dr. John P. Abraham, University of Texas Pan American

Domain Name System Domain name system (DNS) A distributed system for managing hostname resolution Domain name server A computer that attempts to translate a hostname into an IP address Should the tables containing hostname/IP mappings be sorted or unsorted? Why? 70 Dr. John P. Abraham, University of Texas Pan American

Social Networks Social networks are a model (simulation) of how objects-individuals and organizations--interact – Internal: Participants are within a closed or private community – External: No restrictions on membership Functionality Participants can – – – 71 describe themselves set privacy settings block unwanted members have personal pages of pictures/bloggs form or be a member of a community within the larger community Dr. John P. Abraham, University of Texas Pan American