INTERNET ROUTING COMMUNICATION LAYERS SFTP WEB SERVERS INTRODUCTION TO HTML CS100 PROFESSOR SULTANA GMU CS Dept Slides Adapted from Dr Zaman Understanding TCP IP and Networking Client server applications Two computers and two applications involved Communication occurs three levels Hardware operating system application Dependent on one computer addressing the other Figure A web browser client software requests a web page from a web server server software the web server returns the requested data to the client Understanding TCP IP and Networking 1 One computer must find the other computer 2 Both computers agree to rules of communication Protocols 3 One computer is making request one is answering the request Figure A web browser client software requests a web page from a web server server software the web server returns the requested data to the client Layers of Network Communication When two devices communicate they must use the same protocols language Almost all networks today use a group or suite of protocols known as TCP IP Transmission Control Protocol Internet Protocol Communication between two computers happens in layers Application passes a request to the OS which passes the request to the network card and then onto the network Layers of Network Communication Layers of Network Communication Level 1 Hardware level Root level of communication Wireless or network cables Phone lines or TV cable lines Includes the network adapter NIC and MAC address MAC media access control address is a unique 48 bit number in Hexadecimal representation hard coded on the card by the manufacturer Also known as hardware address physical address adapter address or Ethernet address Used to locate a computer on a local area network Layers of Network Communication Figure This is Gigabit Ethernet adapter by Intel Layers of Network Communication Level 2 Operating system level Manages communication between itself and another computer using TCP IP Uses IP addressing Figure Computers on the same LAN use MAC addresses to communicate but computers on different LANs use IP addresses to communicate over the Internet Layer of Network Communication Layer 2 Operating system level cont d IP address 32 bit or 128 bit number that is assigned to a network connection Used to find computers on networks and subnetworks including the Internet Example 136 60 30 5 Layers of Network Communication Level 3 Application level Client communicates with server applications Such as a web server or email server Port number port or port address Uniquely identifies a computer application Port number is added to IP address IP address followed by a colon and port number E mail server example 136 60 30 5 25 Web server example 136 60 30 5 80 Layers of Network Communication Figure Each server running on a computer is addressed by a unique port number Layers of Network Communication How IP Addresses Get Assigned Internet Protocol version 4 IPv4 uses a 32 bit address to identify An IP address has 32 or 128 bits a network connection Currently a shortage of IPv4 IP addresses Internet Protocol version 6 IPv6 was created partly due to the shortage of IPv4 addresses Uses a 128 bit IP address Internet Assigned Numbers Authority IANA is responsible for keeping track of assigned IP addresses How IP Addresses Get Assigned A MAC address is embedded on a network adapter at a factory IP addresses are assigned manually or by software Static IP address manually and permanently assigned to a computer or device Dynamic IP address assigned by a server each time the device connects to the network A DHCP dynamic host configuration protocol server assigns addresses to a DHCP client that is requesting an address DHCPv6 server serves up IPV6 addresses How IPv4 IP Addresses Are Used Figure A host router in this case can always determine if an IP address is on its network How IPv4 IP Addresses Are Used NAT Network Address Translation is a technique designed to conserve the number of public IP addresses needed by a network A router or other gateway device stands between a private network and the Internet and substitutes the private IP addresses used by computers on the private network with its own public IP address Another advantage of NAT is security the gateway hides the entire private network behind this one address Google what is my IP address Character based Names Identify Computers and Networks Remembering an IP address is not always easy so character based names are used to substitute for IP addresses Character based Names Identify Computers and Networks Character based names substitute for IP addresses Host name computer name name of a computer Domain name identifies a network Fully qualified domain name FQDN identifies computer and network to which it belongs Character based Names Identify Computers and Networks Character based names substitute for IP addresses Host Name computer name name of a computer Can be used in place of its IP address The name can have up to 63 characters including letters numbers and special characters Examples of computer names are www ftp Jean s Computer TestBox3 and RedLaptop Recall you can assign a computer name while installing OS In addition you can change the computer name at any time using the system settings preferences Character based Names Identify Computers and Networks Character based names substitute for IP addresses Domain Name Identifies a network Examples of domain names are the names that appear before the period in microsoft com course com and mycompany com The letters after the period are called the top level domain and tell you something about the domain Examples are com commercial org nonprofit gov government and info general use Character based Names Identify Computers and Networks Character based names substitute for IP addresses Fully qualified domain name FQDN identifies computer and network to which it belongs An example of an FQDN is www cengage com The host name is www a web server cengage is the domain name and com is the top level domain name of the Cengage network Another FQDN is joesmith mycompany com On the Internet a fully qualified domain name must be associated with an IP address before this computer can be found This process of associating a character based name with an IP address is called name resolution The DNS Domain Name System or Domain Name Service protocol is used by a DNS server to find an IP address for a computer when the fully qualified domain name is known When you enter a FQDN in