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:  How communication will be started  How communication will be ended  How much data can be sent at one time  How will data errors be discovered  How will data errors be corrected  How will communication with the Internet will take place

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

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

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

Network Software 3. Default Gateway  The IP address of the Router  A router is used to connect a network to the Internet  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  The address would be different for other ISP’s

Network Software 4. DNS Servers  Websites are given user friendly names called URL’s  This stands for Uniform Resource Locator  Examples include etc.  Computers can’t use URL’s to find websites  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 ( to it’s IP address ( ) etc.

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

Network Software ISP DNS servers Below is a table with the DNS servers most commonly used in Ireland: ISPDNS Servers Eircom Digiweb Net BT Ireland Heanet

Network Software DNS server entries Below is a number of sample entries from a typical DNS server: URLIP Address

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

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