13.3 Helpdesk: Understanding IP Addresses, Domain Names, and Protocols

Domain Name

A domain name is simply a name that takes the place of an IP address, making it easier for people to remember it. Yahoo.com and AOL.com are domain names. Domains are organized by level: 1. The portion of the domain name farthest to the right (after the dot) is the top-level domain (TLD). Examples of TLDs include .com, .edu, and .org. 2. Within the top-level domains are many second-level domains. For example, in the .com top-level domain, there are many second-level domains such as Amazon.com, Google.com, and Microsoft.com.

TCP/IP

Although many protocols are available on the Internet, the main suite of protocols used is TCP/IP. The suite is named after the original two protocols that were developed for the Internet: the Transmission Control Protocol (TCP) and the Internet Protocol (IP). Although most people think that the TCP/IP suite consists of only two protocols, it actually comprises many interrelated protocols, the most important of which are shown here.

What is an IP address and where I can find the IP address for my computer?

An IP address is a unique number identification assigned to each computer, server, or device connected to the Internet. To find your IP address, go to Google and type "what is my IP".

Packet Components

At a minimum, all packets must contain: 1. An address to where the packet is being sent, 2. Reassembling instructions if the original data was split between packets, and 3. The data that is being transmitted.

When my friend connects to my computer, how is data transferred?

Computers communicate efficiently using the communication methodology called packet switching.

But how do computers get the IP address from a domain name?

Computers consult the domain name system (DNS) server. The DNS server contains a mapping of domain names with their corresponding IP addresses.

Dynamic Host Configuration Protocol (DHCP)

Dynamic addressing is normally handled by the dynamic host configuration protocol (DHCP). When a user logs on to an ISP's server, the DHCP server assigns that user an IP address for the duration of the session. These temporary IP addresses may or may not be the same from session to session. Because dynamic IP addresses are always changing, your computer is less vulnerable to hacker attacks than with a static IP address.

IP Address Basics

Each device connected to the Internet is required to have a unique number identifying it, called an IP address. A typical IP address is expressed as a series of numbers separated by decimal points as follows: 197.169.73.63 Expressing an IP address like this is called a dotted decimal number (or dotted quad). Computers work with binary numbers internally. The same IP address in binary form would be: 11000000.10101000.00101000.00111111 The four parts in this notation are each referred to as an octet because each section has eight numbers.

Domain Name Servers

How does your computer know the IP address of another computer? It uses a database maintained on a domain name system (DNS), which functions like a phone book for the Internet.

Static and Dynamic addressing

IP addresses are either assigned statically or dynamically. When a computer has a static addressing, it means that the IP address never changes. Static IP addresses are most likely assigned manually by a network administrator. When a computer has a dynamic addressing, it means that your ISP assigns your computer a temporary IP address from an available pool of IP addresses each time you log on to the Internet.

Finding Your IP Address

One way to find out your IP address is to go to Google and type "what's my IP". Google will show your IP address at the top of the search results.

Packet switching and Circuit Switching

Packet switching is the communications methodology that computers use to transfer data. It replaced circuit switching, the communications methodology used on devices like the telephone. In circuit switching, a dedicated connection is formed between two points (for example, between two people on telephones) and the connection remains active for the duration of the transmission. This method of communication is extremely important when communications must be received in the order in which they were sent (such as in telephone conversations). Packet switching does not require a dedicated communications circuit to be maintained. With packet switching, data is broken into smaller chunks (called packets or data packets) and sent over various routes at the same time. When the packets reach their destination, they are reassembled by the receiving computer.

How do packets travel through the Internet?

Packets are routed using Transmission Control Protocol/Internet Protocol (TCP/IP). TCP/IP is a suite of protocols used to route packets over the Internet.

Packet Transmission

Sending a packet is like sending a letter. Say you are sending a very long letter to your aunt. The letter is too big to fit in one envelope, so you mail three envelopes. Each one includes your aunt's address, a return address, and different pages of the letter. Each envelope may not find its way to San Diego by the same route, but they will all eventually arrive in your aunt's mailbox. Your aunt will then put the pages of the letters in order and read it. The process of sending a message through the Internet works in much the same way, as we see here.

Does the IP address remain the same or can it change automatically?

The IP address changes automatically if your computer has a dynamic IP address. A dynamic IP address is a temporary IP address and is assigned by your ISP when your computer connects to the Internet.

Internet Protocol

The Internet Protocol (IP) is the protocol that is actually responsible for sending the information from one computer to another. The IP is like a postal worker who takes a letter (a packet of information) that was mailed (created by the sending computer) and sends it on to another post office, which in turn routes it to the addressee (receiving computer).

What if the ISP's web server cannot locate the IP information on the default DNS server?

The default DNS server contacts one of the DNS servers. A root DNS server knows the location of all the DNS servers that contain the master listings for an entire top-level domain.

If data is broken into chunks and sent over various routes at the same time, how do these packets reach their destination?

The packets contain destination information and are reassembled when they all reach the destination.

Is there an alternative to remembering IP addresses?

Yes, you can use a domain name. A domain name is simply a name that takes the place of an IP address, making it easier to remember.