BITS 2513 – INTERNET TECHNOLOGY LECTURE 3: INTERNET INFRASTRUCTURE
TOPICS1. To connect to Internet:• Using a Telephone Line to Connect to Internet• Using a Cable Modem, ISDN, DSL or Satellite to Connect to the Internet• Connecting a PC on a LAN to the Internet2. Physically and Logically Dividing a Large Network3. Routing on the Internet
Using a Telephone Line to Connect to Internet
Using a Telephone Line to Connectto the Internet• To establish a successful connection, you need: – Modem to transmit data over the telephone line and software that allows the operating system to interact with the modem – Operating system utility that allows you to configure the modem to connect to a specific ISP – TCP/IP protocol stack – ISP user information: Telephone number, user ID, password, and other information needed to connect to an ISP
Using a Cable Modem, ISDN, DSL or Satellite to Connect to the Internet
Modems: An Introduction• The word modem comes from modulator/demodulator, which means to convert from analog to digital and digital to analog.• A telephone line connects to a modem or telephone using either an RJ-11 or an older RJ-12 connector.• A modem is responsible for managing communication between devices and can also be referred to as a Data Communications Equipment (DCE) device.
Modems: An Introduction (Continued) • The computer or terminal that is using the DCE to communicate with another device is called the Data Terminal Equipment (DTE).
Installing a Modem and Its Drivers• To connect to the Internet using a telephone line, you first must install and configure a modem, and then install the software that drives the modem.• Modem divided into 2: - External Modem - Internal modem
Installing a Modem and Its Drivers –External Modem (Continued)• If the modem is an external (modem) device, insert the modem to a serial port on the back of the computer using a serial cable.• The port either can have 9 pins or 25 pins and is designed according to the serial port standard called the RS-232 standard or, more recently, the EIA/TIA-232 standard.
Installing a Modem and Its DriversInternal Modem (Continued)• If the modem is an internal modem, the modem card is inserted in an expansion slot, typically a PCI slot, inside the computer and communicates with the CPU through lines connecting the slot to the CPU that are embedded on the motherboard.
Testing a Modem (Exercise)• Do a research on how to test a modem, Find: - 1st; algorithms of modem test using Windows XP. - 2nd; algorithms of modem test using Windows 2000.• What will happen if the operating system cannot communicate with the modem?
Creating a Dial-Up Connection• Dial-Up Networking (DUN) is a process that enables a computer to use a modem and a telephone line to connect to a network, just as if that computer had a network card and network cables.• The modem behaves just like a network card, providing the physical connection to the network and the firmware at the lowest level of communication in the OSI model.
Creating a Dial-Up Connectionin Windows 98• When Windows 98 installs Dial-Up Networking, it also “installs” a dial-up adapter.• In terms of function, think of a dial- up adapter as a virtual network card.• It is a modem playing the role of a network card for Dial-Up Networking.• To verify that Dial-Up Networking is installed under Windows 98, double- click My Computer on the Windows desktop.
Configuring TCP/IP• In Windows 2000 and Windows XP, TCP/IP is automatically installed when a network card or modem is added to a computer.• In Windows 98, you must install TCP/IP and bind it to the modem.
The Role of TCP/IPin a Dial-Up Connection• The following list summarizes some of the most important information about TCP/IP: – Every computer using the Internet must be assigned a unique IP address. – A gateway is a computer or other device that allows a computer on one network to communicate with a computer on another network. – A subnet mask is to tell the TCP/IP whether the remote computer is on the same or different network – A domain name server is a computer to translate the domain name into IP address. – A computer might have permanent IP address (static IP addressing) or be assigned a different IP address each time it log on into the network (dynamic IP addressing)
Multilink PPP Connections• Protocol to see other computer in the network.• When a computer communicates with another computer using only a single connection, the connection is said to be point-to-point.• The dial-up connection you just created is a point-to-point connection.• Windows 98/2000/XP also support Multilink PPP, which allows you to use two or more physical connections for a single, virtual, dial-up link called a multipoint connection.• The protocol that makes a multipoint connection possible is PPP Multilink (MP), sometimes known as Point-to-Point Multilink, Multilink PPP, Multilink, or just MP.
Connection to the Internet via Cable,ISDN, DSL, or Satellite• Connecting a single computer to an ISP via cable, ISDN, DSL, or satellite requires the same TCP/IP settings as a dial-up connection on a regular phone line.• Cable modems, DSL, and LANs all use a network card in the computer for the physical connection.• The network card provides a network port for a network cable.• For cable modem service to the Internet, the other end of the network cable connects to a cable modem.
Connection Using - Cable Modems• The cable modem connects to a regular TV coaxial cord, which then connects to a TV cable wall outlet.• The cable modem also has an electrical connection to provide power to the box, as well as a connection to a network card in your computer.
Configuring TCP/IP to Connectto the Cable Modem• By default, Windows 2000 and Windows XP should configure TCP/IP correctly.• It obtains the necessary information automatically from your ISP.
Connection Using - Integrated ServicesDigital Network (ISDN) and DSL• ISDN requires a device, called an NT1 (Network Terminator 1), that connects the ISDN and DSL systems; this device is located inside or outside your house where the telephone company’s responsibility ends.• You also need another device called a TA (terminal adapter).• A DSL connection uses a DSL converter box that is sometimes combined with a router as a single device so more than one computer can use the DSL line.• Ex: Streamyx
Connecting to the Internet bySatellite• The first thing the technician does is to find the best place for the satellite dish.• For North America, the best position is one that faces the south and does not have any objects (such as trees or other buildings) blocking transmission.• After the satellite disk is mounted to the house, cables are wired through the house to the room containing the computer.• Then, modems are connected to the computer, usually through a USB port.
Connecting a PC ona LAN to the Internet
Connecting a LAN to the Internet
Connecting the Gateway to the Internet
Connecting the Gateway to theInternet (Continued)• The connection to the LAN always uses a network card, but the connection to the ISP could be a (i) network card, (ii) modem, or (iii) ISDN card.• If the connection to the ISP is by way of a network card, the computer has two network cards installed.• One card is bound to the protocol used by the LAN and the other card is bound to the protocol used by the ISP’s network, which is always TCP/IP.
Configuring a Computer on a LANto Connect to the Internet• To configure TCP/IP correctly for a computer on a LAN, you must know the answers to these questions: – Does the network use a proxy server? – If it does, what is the IP address of the server? If no proxy server is used, what is the IP address of the default gateway? – Is static IP addressing or dynamic IP addressing used? If static IP addresses are used, what is the IP address and subnet mask?
Physically and Logically Dividing a Large Network
Physically and Logically Dividing aLarge Network• You can divide a network using two approaches: 1. You can physically divide the network using hardware devices 2. You can logically divide the network using software settings• The first approach is called segmenting the network; the second approach is called subnetting.
Bridges and Switches• Bridges and Switches are more intelligent than hubs and make decisions involving whether to allow traffic to pass or where to route that traffic, reducing traffic on each segment and improving network performance.• A routing table is a database stored within a router that is used to find the best network path on which to forward information.• A network bridge keeps routing tables for each network to which it connects.
Bridges and Switches (Continued)• The tables start out empty and all data packets that reach the bridge from one segment are passed on to the other segment connected to the bridge.• Just like bridges, switches keep tables of the MAC addresses of all the devices connected to the switch.• Switches use these tables to determine which path to use when sending packets.• However, unlike a bridge, a switch passes a packet only to its destination segment instead of to all segments other than the one it came from.
Bridges and Switches (Continued)• Bridges and switches use MAC addresses to subdivide a network into physical segments.• However, all the segments are still logically a single network because each host is communicating with other hosts on other segments using the MAC address rather than the IP address.• As far as a host is concerned, it is not aware that a bridge or a switch exists in the network.
Subnetting• A large network can be logically divided into two or more networks based on IP addresses rather than MAC addresses to reduce congestion.• Each division (of a network) is called a subnet and the process is called subnetting.
Subnet Masks• How does the host know if a remote host is on the same network?• An IP address is made up of the network ID and the host ID.• The host is told what portion of the IP address identifies the network by an entry in the TCP/IP configuration settings.• This entry is called the network mask, or subnet mask, and is used to define which portion of an IP address identifies the network and which portion identifies the host.
Subnet Masks (Continued)• The network mask is a group of four 8-bit numbers separated by periods.
Subnet Masks (Continued)• If the network IDs had been different, the host would not have attempted to resolve the IP address to the MAC address, but would have sent the data to the gateway to its network.• A gateway is any device, typically a router, that provides access to another network.• Subnet masks usually are not displayed as 32 bits separated by periods as they are in Table 6-1.
Selecting a Subnet Mask• A network engineer carefully selects a subnet mask based on the number of subnets he needs and the number of hosts planned for each subnet.• Table 6-3 shows several examples of subnet masks and explains the number of hosts and subnets that can use each subnet mask.• Subnetting is necessary when a large company is using a Class A, B, or C license for its entire network and wants to use that one license over several networks to prevent network congestion.
Routing on the Internet
How Data Travels AcrossInterconnected Networks• Figure 6-12 shows a simplified view of how networks work together to send data over the maze of many networks called the Internet.• A router is a stateless device, meaning that it is unconcerned about the data that it is routing, but it is concerned about the destination address of that data.• Networks are connected by routers, which belong to more than one network.
How Data Travels AcrossInterconnected Networks (Continued)
Routers• Routers are responsible for helping data travel across interconnected networks.• A router can forward data to the correct network in a way that is similar to a switch’s method.• A router uses the most efficient path available to forward packets to their destination, which may be located across a great geographical distance.
Routers (Continued)• A router, short for bridge and router, functions as both a bridge and a router.• The device can forward routable protocols, including TCP/IP and IPX/SPX packets, and in these cases, is working as a router.
Routers (Continued)• Like switches, routers use tables to determine the best route by which to send the data to its destination.• When routers communicate with other routers to build routing tables and determine availability of routes, one of several protocols is used: RIP, OSPF, BGP, DVMRP, NLSP, or IGRP.
TCP/IP Routing• Suppose a host computer wants to send data to another host.• Remember that the host uses its subnet mask to decide if the destination host is on its own or another network.• If the first host knows that the remote host is on its same network, it must discover the MAC address of the remote host.
TCP/IP Routing (Continued)• If the sending host determines that the remote host is on a different network, it sends the data to the router, which is serving as the gateway to remote networks.• When a packet arrives at a router, the router decides if the packet belongs to a host within its own local network or needs to be routed to a different network.
Routing Across Many Networks• For routing across interconnected networks, each time a packet encounters a router, its TTL is reduced by one.• If the router must send the packet over a network that cannot handle large packets, the router divides the packet into smaller packets.
Default Gateways• Sometimes, a large network has more than one router, as shown in Figure 6-21and so the network has more than one gateway to other networks.• The network in the upper-left of the figure is 250.1.2 and has two routers (D and E), each of which also belongs to other networks.
Default Gateways (Continued)
Default Gateways (Continued)• Host E is designated as the default gateway, meaning that hosts on the 250.1.2 network send packets addressed to other networks to this gateway first.• The other router Host D, is called the alternate gateway and is used if communication to the default gateway fails.
BITS 2513 – Internet TechnologyLecture 4: Internet Infrastructure
Topics• Domain Names on the Internet• Servers that Help with Communication• Bandwidth Technologies 50
Internet InfrastructureDomain Names on the Internet
Domain Names on the InternetWhy Domain Names Assigned?• because IP address numbers are difficult to remember• because companies might want to change their IP addresses without also changing the Internet name by which the outside world knows them.Example of Domain Names:• http://www.ftmk.utem.edu.my/erman/index.html• The last segment, or suffix, of a domain name is called the top-level domain and tells you something about the function of the host.• The first word in a domain name is used to identify a subcategory within the domain and is called a canonical name, or CNAME. 52
DNS Name Space 53
Assigning and Tracking DomainNames and IP Addresses• Organization responsible : IANA (Internet Assigned Numbers Authority).• Beginning 1999, the responsibility for assigning and tracking domain names and IP addresses was transitioned from IANA to a nonprofit, private sector organization regulated by the U.S. Department of Commerce called ICANN (Internet Corporation for Assigned Names and Numbers).• A company that can register these names and numbers must be approved by ICANN and is called a 54 registrar.
Domain Name Resolution• Domain names and IP addresses do not have to be permanently related.• Two name resolution services track relationships between domain names and IP addresses: DNS (Domain Name System, also called Domain Name Service) and Microsoft WINS (Windows Internet Naming Service).• DNS is the more popular of the two because it works on all platforms. 55
How DNS Works • DNS has three logical components: – COMPUTERS searching for the IP address for a domain name, called resolvers. – SERVERS that contain the information relating domain names to IP addresses, called name servers. – The DATABASES of information needed to resolve domain names and IP addresses, Name nameCOMPUTERS gives the Domaincalledand ask for an IP from SERVERS; spaces. SERVERS look inside the DATABASES to resolves the problem 56
How DNS Works (Cont’d) Address Resolution/Mapping? • Process of discovering an IP address for a given domain name. Address Reverse Resolution/Mapping? • Process to find the domain name for a given IP address.COMPUTERS gives the Domain Name and ask for an IP from SERVERS; SERVERS look inside the DATABASES to resolves the problem 57
Address Resolution Root Server Primary Server Secondary Server 58
DNS Resolver & Local Cache What is actually happening? 59
DNS Records• Each name server holds a piece of the namespace, which is the database containing information needed to resolve domain names and IP addresses.• A name server keeps the entries for each domain name that it knows about in a resource record, or DNS record.DNS Records?• Piece of the namespace, which is the database containing information needed to resolve domain names and IP addresses. 60
Exercise : DNS Record Types• Define the common resource record types in the DNS database: ? ? ? ? ? 61
Host Table – The EarlyImplementation• Before 1983, when DNS began evolving into an Internet standard, one huge file called the hosts table contained the name and IP address of every named host on the Internet. – Host tables can still be used to give a node a nickname, enhance performance on your local network, or on an isolated internal network. 62
Host Table (Cont’d)• To view the hosts table on your computer, traverse to c:windowssystem32driversetc or c:winntsystem32driversetc and view the hosts file in Notepad. 63
Internet InfrastructureServers that Help with Communication
Directory Server• A Directory Server stores information about people, hosts, and other resources on the network in directories and provides this information to computers on the network.• The information in a directory is read more often than it is written. 65
How Directories Work• Directories follow an upside-down tree structure with the root at the top and branches underneath the root in a hierarchical structure. 66
Using Directories• Directories and directory servers can serve various functions on networks and on the Internet.• Directories on the Web are similar to search engines in the way they operate and provide information. 67
Cache Servers• Microsoft Internet Explorer supports browser caching, which allows the user to indicate how much hard drive space should be allocated to Web caching.• A cache server improves performance by caching data so that the number of requests to the Internet is reduced.• Cache servers save Web pages and other files that users have requested so that when a page is requested again, it can be retrieved without 68
Using a Mirrored Server to Handle SiteTraffic• Mirrored servers have two main purposes: – They reduce download time for users by handling some of the traffic for a frequently accessed Web site (provides redundancy). – They serve as backups for the main server in case it goes down (provides fault-tolerance). 69
Mirrored Servers?• A mirrored server carries the same data and services as another server. These servers are exact replicas of the main servers that they mirror and are updated often to ensure that they contain the same data.• Web sites that get a lot of traffic often need more than one server.• If the traffic comes from different parts of the world, it might be necessary to have servers in different locations to provide the best service for international customers. 70
Print Servers• Print servers make printers available for shared use across a network or even across the Internet.• Each print server can have several printers attached to it, and you can have more than one print server on a network, depending on the size of the network and the needs and locations of the users on it. 71
LPD Servers• LPD (Line Printer Daemon) server is print server software that initially was developed on UNIX servers to handle print jobs, but is now supported by Windows Server 2003, Windows 2000 Professional, and Windows NT Server.• A client communicating with an LPD server can use two protocols, LPR and LPQ, which are part of the TCP/IP protocol suite. 72
LPD Servers (Cont’d)• The client uses the LPR (Line Printer Remote) protocol to send print jobs over a TCP/IP network to the server.• Clients that use LPR are sometimes referred to as LPR clients.• A second protocol, LPQ (Line Printer Queue), is required for users to be able to check on the status of print jobs they have sent. 73
Internet Printing Protocol (IPP)• Another useful and more recently developed printing protocol is IPP (Internet Printing Protocol).• IPP, which also enables printing across LANs and the Internet, is generally more versatile than LPD and its associated services, and is more easily compatible with various operating systems.• The greatest benefit of IPP is being able to find a printer by using the printer’s IP address or URL.• With IPP, you can find any Internet- connected printer, print to it, and check the status of your print job. 74
Internet InfrastructureBandwidth Technologies
Bandwidth Technologies?• Much attention is given to the amount of data that can travel over a given communication system in a given amount of time.• This measure of data capacity is called bandwidth, also called data throughput or line speed.• The greater the bandwidth, the faster the communication. 76
Bandwidth Technologies Used toConnect to an ISP 77
Common Bandwidth Technologies Technology Maximum Description Throughput SpeedsGSM mobile 9.6 to 14.4 Kbps Provides access fortelephone (wireless personal & businesstechnology) mobile phonesRegular telephone Up to 56 Kbps Provides home & small(PSTN: Public Switched businesses access to anTelephone Network) ISP via a modemX.25 (WAN bandwidth 56 Kbps Providestechnology) communication between mainframes & terminals 78
Common Bandwidth Technologies(Cont’d) Technology Maximum Description Throughput SpeedsISDN (Integrated 64 to 128 Kbps Provides access to anServices Digital ISP for small toNetwork) medium size businessesIDSL (ISDN DSL: ISDN 128 Kbps Provides access to anDigital Subscriber Line) ISP for home & small businessesCable modem 512 Kbps to 5 Mbps Provides access to homes or small businesses; strong competitor to DSL 79
Common Bandwidth Technologies(Cont’d) Technology Maximum Description Throughput Speeds802.11b wireless Up to 11 Mbps Connects wireless devices to network, most popular form of wireless technology802.11a wireless Up to 54 Mbps Features a shorter range than 802.11a, but faster802.11g wireless Up to 54 Mbps Compatible with 802.11b, but faster 80
Common Bandwidth Technologies(Cont’d) Technology Maximum Description Throughput SpeedsFrame relay (WAN 56 Kbps to 45 Mbps Connects business thatbandwidth technology) need to communicate internationally or across the countryATM: Asynchronous 25, 45, 155, or 622 Supports large businessTransfer Mode (WAN Mbps networks & LAN back-bandwidth technology) bonesGigabit Ethernet 1 Gbps Provides fast network connections for devices on a LAN; latest Ethernet standard 81