Technology ICT Communications Computer Networks Resource Notes Network

Technology ICT Communications & Computer Networks Resource Notes - Network Software

Network Software For networked computers to communicate with each other, network software is needed. This software is called a network protocol and is a set of rules to control the communication between the computers Rules cover items such as: Ø How communication will be started Ø How communication will be ended Ø How much data can be sent at one time Ø How will data errors be discovered Ø How will data errors be corrected Ø How will communication with the Internet will take place

Network Software Transmission Control Protocol/Internet Protocol (TCP/IP) Ø The protocol used in modern networks Ø A number of settings must be set on each computer

Network Software 1. IP Address Small networks use Class C addresses (e. g. 192. 168. 1. 1) Ø The first three numbers are the address of the network Ø The fourth number is the address of the actual computer Ø The computer below is computer 1 on network 192. 168. 1 IP Address 192. 168. 1. 1 E. g. In a four computer network, the IP addresses could be: Ø 192. 168. 1. 1 - 192. 168. 1. 2 - 192. 168. 1. 3 - 192. 168. 1. 4 Ø The last possible IP address is - 192. 168. 1. 254

Network Software 2. Subnet Mask The subnet mask shows what class the IP address belongs to Ø 255. 0. 0. 0 - Class A network Ø 255. 0. 0 - Class B network Ø 255. 0 - Class C network. IP Address Subnet Mask 192. 168. 1. 1 255. 0 Ø Three 255’s fix the Network address Ø One 0 fixes the Computer address

Network Software 3. Default Gateway Ø The IP address of the Router Ø A router is used to connect a network to the Internet Ø The gateway address is the address used to leave the network The example below is the gateway address for a router connected to Eircom Broadband: Default Gateway Ø 192. 168. 1. 254 The address would be different for other ISP’s

Network Software 4. DNS Servers Ø Websites are given user friendly names called URL’s Ø This stands for Uniform Resource Locator Ø Examples include - www. google. ie, www. t 4. ie etc. Ø Computers can’t use URL’s to find websites Ø Computers need the IP addresses of the computers holding the websites to locate them A DNS (Domain Name Service) server is a Database used to link the Domain name (www. t 4. ie) to it’s IP address (82. 195. 130. 32 ) etc.

Network Software Ø Each ISP has it’s own DNS servers Ø ISP’s use 2 DNS servers Ø If one goes offline, the other can take over (redundancy) Ø You can use any ISP’s DNS servers Ø DNS servers communicate with each other on a global scale Ø If a website can’t be found, a DNS error is given The DNS servers shown below are for Eircom broadband: Preferred DNS server: 159. 134. 237. 6 Alternate DNS server: 159. 134. 248. 17

Network Software ISP DNS servers Below is a table with the DNS servers most commonly used in Ireland: ISP DNS Servers Eircom 159. 134. 237. 6 - 159. 134. 248. 17 Digiweb 83. 147. 160. 2 - 83. 147. 160. 3 Net 1 80. 249 - 80. 249. 250 BT Ireland 194. 125. 2. 240 - 194. 125. 2. 241 Heanet 87. 32. 4. 16 - 87. 32. 4. 24

Network Software DNS server entries Below is a number of sample entries from a typical DNS server: URL IP Address www. google. ie 216. 239. 59. 103 www. microsoft. com 65. 55. 21. 250 www. mozilla. com 63. 245. 213. 11

Network Software 5. DHCP server Ø Stands for - Dynamic Host Configuration Protocol Ø Used to automatically give IP information to network devices Ø Dynamic - the IP information is leased and can change Ø The Lease length is given with the IP information Ø IP information set manually is called Static addressing Ø Dynamic addressing simplifies network administration Ø Software keeps track of the allocation of addresses and leases Ø Addresses given from a Scope - a set pool of addresses Ø New PC’s are easily added as the IP information necessary to join the network is automatically given

Network Software Ø In Workgroups, the Router usually supplies the IP information, if dynamic addressing is being used Ø In Domains, the Server usually provides the IP information Typical DHCH supplied IP information is shown below: