DNS Overview
What is DNS? • Distributed Directory Service • Maps names to values – resource records • Major backbone of the internet • Makes networks human friendly
• Domain Name Server/System • Comes from your service provider amongst other places • The DNS translate the domain name to an IP address • An IP address in the IPV 4 standard has four numbers separated by three decimals, as in: 70. 74. 251. 42 •
• DNS gives us the name of a website • At the start of the internet you needed to type the IP address • Instead of remembering this number, DNS provides a name: Google. com (for example) • one of Googles many IP addresses is http: //74. 125. 224. 72/
Purpose of naming (review) • Addresses are used to locate objects • Names are easier to remember than numbers • You would like to get to the address or other objects using a name • DNS provides a mapping from names to resources of several types • IP address can be changed but Domain name can remain the same February 2003 slideset 1 -5
• IP addresses can be Dynamic or Static • Static IP addressing is for one customer on one IP address and Dynamic IP addressing assigns a different IP address each time the ISP customer logs on to their computer, but this is dependent upon the Internet Service Provider (ISP) because some ISP's only change the IP address as they deem it necessary
192. 168. 1. 1 Network Host Name
• IPV 4 vs IPV 6 • IPV 4 now running out of IP addresses – limited – Uses 32 bits – different IP Addresses that can exist. However, due to the allocation of IP ranges to different organisations and tasks, the number is lower.
• IPV 6 opens up the number of addresses • IPv 6 uses 128 bits for each address, meaning we have theoretically addresses available.
• • • http: //whatismyipaddress. com/ http: //www. whatismyip. com/ You can check your IP on the LAN Type CMD Then – ipconfig
Ping • Find if a website is “up” • Find a websites IP address
Subnet Mask • A subnet mask allows IP networks to be subdivided for security and performance purposes A subnet mask allows you to identify which part of an IP address is reserved for the network, and which part is available for host use
Default Gateway • In computer networking, a gateway is a node (a router) on a TCP/IP network that serves as an access point to another network
Questions ? ? ? • Give two reasons why a company might want to use a domain name instead of an IP Address for their website? • Describe what a Domain Name Server does • List the three parts that make up a domain name:
