Network Addresses-Alamat Rangkaian
For routers to be able to determine the correct route between two computers, each computer needs to have an address so that the routers know where to send the data. In networking terms, an address is a unique identifier for a given device. Even routers themselves have addresses – in fact, for any destination address (like a Web server), routers only need to know the address of the next nearest router to the destination, and they simply hand over responsibility for delivering the data to that router. Eventually the last router in the chain knows the Web server itself and can deliver the data to it.
On the Internet, an Internet Protocol (IP) address is a four-byte number, usually written in ‘dotted decimal’ notation; for example 10.43.172.77. Every device in the world that connects directly to the Internet has a unique four-byte IP address. This means that there are over four billion possible IP addresses (although around 20 million addresses are reserved for special uses). This may seem like a big number, but there are increasing numbers of computers connected to the Internet.
Even using dotted decimal notation, IP addresses are not very memorable. People tend to find it easier to remember names than numbers. For this reason, the Internet has a system that makes it possible for a Web site to have a ‘friendly’ name as well as a less memorable IP address. This is the Domain Name System (DNS), which works by translating domain names into IP addresses. There are many DNS servers connected to the internet, and their job is to act like a telephone directory for the Internet – they look up the IP address for a given domain name in a big list of all the domain names. For example, when you type a Web address into your browser’s address bar, the following steps occur, as shown in the diagram:
The browser determines the target server name (host name) from the Web address.
Your computer uses DNS to retrieve the IP address of the target computer. It contacts the DNS server and passes the host name.
The DNS server searches its list of domain names for a matching record, and sends the IP address back to your computer.
Your computer then uses the IP address to establish communication with the Web server.
On the Internet, an Internet Protocol (IP) address is a four-byte number, usually written in ‘dotted decimal’ notation; for example 10.43.172.77. Every device in the world that connects directly to the Internet has a unique four-byte IP address. This means that there are over four billion possible IP addresses (although around 20 million addresses are reserved for special uses). This may seem like a big number, but there are increasing numbers of computers connected to the Internet.
Even using dotted decimal notation, IP addresses are not very memorable. People tend to find it easier to remember names than numbers. For this reason, the Internet has a system that makes it possible for a Web site to have a ‘friendly’ name as well as a less memorable IP address. This is the Domain Name System (DNS), which works by translating domain names into IP addresses. There are many DNS servers connected to the internet, and their job is to act like a telephone directory for the Internet – they look up the IP address for a given domain name in a big list of all the domain names. For example, when you type a Web address into your browser’s address bar, the following steps occur, as shown in the diagram:
The browser determines the target server name (host name) from the Web address.
Your computer uses DNS to retrieve the IP address of the target computer. It contacts the DNS server and passes the host name.
The DNS server searches its list of domain names for a matching record, and sends the IP address back to your computer.
Your computer then uses the IP address to establish communication with the Web server.
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