Type ping www. The pinged computer will respond with a reply. The ping program will count the time expired until the reply comes back if it does.
Also, if you enter a domain name i. More on domain names and address resolution later. Protocol Stacks and Packets So your computer is connected to the Internet and has a unique address.
How does it 'talk' to other computers connected to the Internet? An example should serve here: Let's say your IP address is 1. The message you want to send is "Hello computer 5. Obviously, the message must be transmitted over whatever kind of wire connects your computer to the Internet. Let's say you've dialed into your ISP from home and the message must be transmitted over the phone line. Therefore the message must be translated from alphabetic text into electronic signals, transmitted over the Internet, then translated back into alphabetic text.
How is this accomplished? Through the use of a protocol stack. Every computer needs one to communicate on the Internet and it is usually built into the computer's operating system i. Windows, Unix, etc. Hardware Layer Converts binary packet data to network signals and back. If we were to follow the path that the message "Hello computer 5. If the message to be sent is long, each stack layer that the message passes through may break the message up into smaller chunks of data. This is because data sent over the Internet and most computer networks are sent in manageable chunks.
On the Internet, these chunks of data are known as packets. Each packet is assigned a port number. We need to know which program on the destination computer needs to receive the message because it will be listening on a specific port. This is where each packet receives it's destination address, 5. Now that our message packets have a port number and an IP address, they are ready to be sent over the Internet. The hardware layer takes care of turning our packets containing the alphabetic text of our message into electronic signals and transmitting them over the phone line.
On the other end of the phone line your ISP has a direct connection to the Internet. The ISPs router examines the destination address in each packet and determines where to send it. Often, the packet's next stop is another router. More on routers and Internet infrastructure later. Eventually, the packets reach computer 5. As the packets go upwards through the stack, all routing data that the sending computer's stack added such as IP address and port number is stripped from the packets.
When the data reaches the top of the stack, the packets have been re-assembled into their original form, "Hello computer 5. But what's in-between? What actually makes up the Internet? Let's look at another diagram: Diagram 3 Here we see Diagram 1 redrawn with more detail.
The physical connection through the phone network to the Internet Service Provider might have been easy to guess, but beyond that might bear some explanation. The ISP maintains a pool of modems for their dial-in customers. This is managed by some form of computer usually a dedicated one which controls data flow from the modem pool to a backbone or dedicated line router.
This setup may be refered to as a port server, as it 'serves' access to the network. Billing and usage information is usually collected here as well. From here the packets will usually journey through several routers and over several backbones, dedicated lines, and other networks until they find their destination, the computer with address 5.
But wouldn't it would be nice if we knew the exact route our packets were taking over the Internet? As it turns out, there is a way This one is called traceroute and it shows the path your packets are taking to a given Internet destination. Like ping, you must use traceroute from a command prompt. In Windows, use tracert www. From a Unix prompt, type traceroute www. Like ping, you may also enter IP addresses instead of domain names. Traceroute will print out a list of all the routers, computers, and any other Internet entities that your packets must travel through to get to their destination.
If you use traceroute, you'll notice that your packets must travel through many things to get to their destination. Most have long names such as sjc2-core1-h These are Internet routers that decide where to send your packets. Several routers are shown in Diagram 3, but only a few. These devices use intricate formulas to figure out exactly where to send a packet and how to get it there. Learn all about routing algorithms. By Roozbeh Razavi. Voice over Internet Protocol lets you make free long-distance phone calls using your computer.
It's essentially a phone network that uses the Internet infrastructure already connecting computers all over the world. As we move closer to intelligent computers, they may begin to follow us wherever we go. Learn how ubiquitous networking will allow our data and information to travel with us. If your computers are in different rooms, phone-line networking may be a good way to connect them. Learn all about the pros and cons of using a phone-line network.
No new wires! Power-line networking uses the wiring already in your house to connect your computers. Learn about the pros and cons of a power-line network and how to set one up. If you're thinking of networking the computers in your home, you have several options to explore. Will you go wired or wireless?
And what's the best way to ensure the safety of your network? By Tracy V. NAT helps reuse IP addresses and improve security -- find out how it works. Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. Computer Hardware. Computer Networking. What's another name for FireWire?
How do I update the drivers on my computer? Steve Jobs: Life in Pictures Are tablets changing the way we shop? Are tablets changing the way computers work? How the Kindle Paperwhite Works. Learn More. What are the three types of VPN? What do you need to build a private WiFi network? A Layer 3 router uniquely identifies a device's network connection with a network-assigned IP address. MAC and IP addresses uniquely define devices and network connections, respectively, in a network.
An IP address is a number assigned to a network connection. Modern-day networks deliver more than connectivity. Organizations are embarking on transforming themselves digitally. Their networks are critical to this transformation and to their success. The types of network architectures that are evolving to meet these needs are as follows:. Only Cisco offers a complete portfolio of modern network architectures for access, WANs, data centers, and cloud. While similar in their overall objectives, various types of networks fulfill different purposes.
Networks today are classified in the broad categories below. A LAN is a collection of connected devices in one physical location, such as a home or an office. A LAN can be small or large, ranging from a home network with one user to a large enterprise network with thousands of users and devices. A LAN may include both wired and wireless devices. Regardless of size, a LAN's particular characteristic is that it connects devices that are in a single, limited area.
The Internet can be considered a WAN. Large organizations use WANs to connect their various sites, remote employees, suppliers, and data centers so they can run applications and access necessary data. Physical connectivity in WANs can be achieved by leased lines, cellular connections, satellite links, and other means. A network built for a large organization, typically called an enterprise, needs to fulfill exacting requirements. Since networking is crucial for any modern enterprise to function, enterprise networks must be highly available, scalable, and robust.
These networks have tools that enable network engineers and operators to design, deploy, debug, and remediate them. Service providers operate WANs to provide connectivity to individual users or organizations.
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