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NETWORK ELEMENTS
In the computer world, the term network means two or more connected computers that can share resources such as data and applications, office machines, an Internet connection, or some combination of these, as shown in Figure
Figure above shows a really basic network made up of only two host computers connected; they share resources such as files and even a printer hooked up to one of the hosts. These two hosts “talk” to each other using a computer language called binary code, which consists of lots of 1s and 0s in a specific order that describes exactly what they want to “say.”
LOCAL AREA NETWORK
Just as the name implies, a local area network (LAN) is usually restricted to spanning a particular geographic location such as an office building, a single department within a corporate office, or even a home office. It’s still best to split a big LAN into smaller logical zones known as workgroups to make administration easier In a typical business environment, it’s a good idea to arrange your LAN’s workgroups along department divisions; for instance, you would create a workgroup for Accounting, another one for Sales, and maybe another for Marketing. Figure below shows two separate LANs, each as its own workgroup.
NB: The devices labeled hub and switch are just connectivity devices that allow hosts to physically connect to resources on a LAN.
Notice that there’s a Marketing workgroup and a Sales workgroup. These are LANs in their most basic form. Any device that connects to the Marketing LAN can access the resources of the Marketing LAN—in this case, the servers and printer.
There are two problems with this: ■You must be physically connected to a workgroup’s LAN to get the resources from it. ■You can’t get from one LAN to the other LAN and use its server data and printing resources remotely.
This is a typical network issue that’s easily resolved by using a device called a router to connect the two LANs, as shown in Figure below
You can use routers for more than just connecting LANs, the router shown in Figure above is a great solution because the host computers from the Sales LAN can get to the resources (server data and printers) of the Marketing LAN, and vice versa. Connecting the two workgroups with a type of cable instead of the route would result in having only one big, cumbersome workgroup instead of separate workgroups for Marketing and Sales, and that kind of arrangement isn’t practical for today’s networks. This is because with smaller, individual-yet-connected groups, the users on each LAN enjoy much faster response times when accessing resources, and administrative tasks are easier, too. Larger workgroups run more slowly because there are many hosts within them that are all trying to get to the same resources simultaneously. So the router shown in Figure which separates the workgroups while still allowing access between them.
Servers are usually dedicated to doing one specific important thing within the Network, but not always, sometimes they have more than one job. But whether servers are designated for one job or are network multitaskers, they can maintain the network’s data integrity by backing up the network’s software and providing redundant hardware (for fault tolerance). And no matter what, they all serve a number of client machines. Servers must have considerably superior CPUs, harddrive space, and memory—a lot more than a simple client’s capacity—because they serve many client machines and provide any resources they require. Because they’re so important, you should always put your servers in a very secure area. My company’s servers are in a locked server room because not only are they really pricey workhorses, they also store huge amounts of important and sensitive company data, so they need to be kept safe from any unauthorized access. In the following figure you can see a network populated with both workstations and servers. Also notice that the hosts can access the servers across the network, which is much the general idea of having a network in the first place! Note that there are more workstations here than servers because one server can provide resources to what can sometimes be a huge number of individual users at the same time but workstations don’t.
Hosts
This can be kind of confusing because when people refer to hosts, they really can be referring to almost any type of networking devices—including workstations and servers. But if you dig a bit deeper, you’ll find that usually this term comes up when people are talking about resources and jobs that have to do with Transmission Control Protocol/Internet Protocol (TCP/IP). The scope of possible machines and devices is so broad because, in TCP/IP-speak, host means any network device with an IP address. Yes, as an IT professional stick to the definition being network devices, including workstations and servers, with IP addresses.
Wide Area Network
There are many people who, if asked to define a wide area network (WAN), just couldn’t do it. Yet most of them use the the Internet—every day! With that in mind, you can imagine that WAN networks are what we use to span large geographic areas and truly go the distance. Like the Internet, WANs usually employ both routers and public links, so that’s generally the criteria used to define them.
Here’s a list of some of the important ways that WANs are different from LANs:
■ WANs usually need a router port or ports. ■ WANs span larger geographic areas and/or can link disparate locations. ■ WANs are usually slower. ■ We can choose when and how long we connect to a WAN. A LAN is all or nothing, our workstation is connected to it either permanently or not at all, although most of us have dedicated WAN links now. ■ WANs can utilize either private or public data transport media such as phone lines.
We get the word Internet from the term internetwork. An internetwork is a type of LAN and/or WAN that connects a bunch of networks, or intranets. In an internetwork, hosts still use hardware addresses to communicate with other hosts on the LAN. However, they use logical addresses (IP addresses) to communicate with hosts on a different LAN (other side of the router). And routers are the devices that make this possible. Each connection into a router is a different logical network. Figure below demonstrates how routers are employed to create an internetwork and how they enable our LANs to access WAN resources.
Network Architecture: Peer-to-Peer or Client-Server?
We’ve developed networking as a way to share resources and information, and how that’s achieved directly maps to the particular architecture of the network operating system software. There are two main network types you need to know about: peer-to-peer and client-server. And by the way, it’s really tough to tell the difference just by looking at a diagram or even by checking out live video of the network in operation. But the differences between peer-to-peer and client-server architectures are major. They’re not just physical; they’re logical differences.
Peer-to-Peer Networks
Computers connected together in peer-to-peer networks do not have any central, or special, authority—they’re all peers, meaning that when it comes to authority, they’re all equals. The authority to perform a security check for proper access rights lies with the computer that has the desired resource being requested from it. It also means that the computers coexisting in a peer-to- peer network can be client machines that access resources and server machines and provide those resources to other computers. This actually works pretty well as long as there isn’t a huge number of users on the network, if each user backs things up locally, and if your network doesn’t require much security. If your network is running Windows, MacOS, or Linux in a local LAN workgroup, you have a peer-to-peer network. Figure below gives you a snapshot of a typical peer-to-peer network. Keep in mind that peer-to-peer networks definitely present security- oriented challenges; for instance, just backing up company data can get tedious.
Since it should be clear by now that peer-to-peer networks aren’t all sunshine, backing up all your critical data may be tough, but it’s vital because security is not centrally governed, each and every user has to remember and maintain a list of users and passwords on each and every machine. Worse, some of those all-important passwords for the same users change on different machines—even for accessing different resources.
Client-Server Networks
Client-server networks are the polar opposite of peer-to-peer networks because in them, a single server uses a network operating system for managing the whole network. Here’s how it works: A client machine’s request for a resource goes to the main server, which responds by handling security and directing the client to the desired resource.
This happens instead of the request going directly to the machine with the desired resource, and it has some serious advantages. First, because the network is much better organized and doesn’t depend on users remembering where needed resources are, it’s a whole lot easier to find the files you need because everything is stored in one spot—on that special server. Your security also gets a lot tighter because all usernames and passwords are on that specific server, which is never ever used as a workstation. You even gain scalability—client server networks can have many workstations on them. And surprisingly, with all those demands, the network’s performance is actually optimized. The figure shows a client-server network with a server that has a database of access rights, user accounts, and passwords.
Many of today’s networks are hopefully a healthy blend of peer-to-peer and client server architectures, with carefully specified servers that permit the simultaneous sharing of resources from devices running workstation operating systems. Even though the supporting machines can’t handle as many inbound connections at a time, they still run the server service reasonably well. And if this type of mixed environment is designed well, most networks benefit greatly by having the capacity to take advantage of the positive aspects of both worlds.
