YOUR BUSINESS AND ITS NETWORK

Tutorial Class 3: Networking Devices

In this post, you’ll get to understand the basics of internetworking by focusing on how to connect networks together using Cisco routers and switches. Since you  know exactly what an internetwork is.

You create an internetwork when you connect two or more LANs or WANs via a router and configure a logical network addressing scheme with a protocol such as IP (you’ll get to know more of that later).

I’ll be covering these the following topics in this post:

• ·        Network segmentation

• ·        How bridges, switches, and routers are used to physically segment a network

• ·        How routers are employed to create an internetwork

Networks cannot just stay as a simple computer to computer connection, it grows larger everyday. This means that at some point you’ll have to break up one large

network into a bunch of smaller ones because good communication would have reduced to a slow crawl as the network grew and grew. And with all that growth, your LAN’s traffic congestion has reached  epic proportions. The answer to this is breaking up a really big network into a number of smaller ones—something called  network segmentation . You do this by using devices like routers, switches,

and bridges . Before I go on, there are two terms which I’ll be using in the remaining part of this class that you need to understand; a collision domain and a broadcast domain.

A collision domain is an Ethernet term used to describe a network scenario wherein one particular device sends a packet on a network segment, forcing every other device on that same segment to pay attention to it. At the same time, a different device tries to transmit, leading to a collision, after which both devices must retransmit, one at a time. Not very efficient!

A broadcast domain is a set of all devices on a network segment that hear all the broadcasts sent on that segment.

Now let’s look at the different types of networking devices;

Hubs: hubs don’t segment a network; they just connect network segments together. So basically, it’s an inexpensive way to connect a couple of PCs together, which is great for home use and troubleshooting, but that’s about it!

 Taking a look at the figure above, you get a picture of a basic LAN network that’s connected together using a hub. This network is actually one collision domain and one broadcast domain.

Switches: switches aren’t used to create internetworks (they do not break up broadcast domains by default); they’re employed to add functionality to a network LAN. The main purpose of a switch is to make a LAN work better—to optimize its performance—providing more bandwidth for the LAN’s users. Also, they only “switch” frames from one port to another within the switched network. You’ll get to know more about frames later.

By default, switches break up collision domains . Switches create separate collision domains but a single broadcast domain. 

 

The hub used in the figure above just extended the one collision domain from the

switch port, while all the switch ports have different collision domains (meaning one host doesn’t have to wait for another to transmit before it can transmit) but are on the same broadcast domain (they are all on the same network, thus, they can communicate).

Here’s a list of some of the things that commonly cause LAN traffic congestion:

• ·        Too many hosts in a broadcast domain

• ·        Broadcast storms

• ·        Multicasting

• ·        Low bandwidth

• ·        Adding hubs for connectivity to the network

Bridges: The term bridging was introduced before routers and hubs were implemented, so it’s pretty common to hear people referring to bridges as switches. That’s because bridges and switches basically do the same thing—break up collision domains on a LAN, so switches can still be called multiport bridges, still there are differences. Switches do provide this function, but they do so with greatly enhanced management ability and features. Plus, most of the time, bridges only had 2 or 4 ports. This is nothing compared to the hundreds available on some switches!

Routers: routers are used to connect networks together and route packets of data from one network to another. Routers, by default, break up a broadcast domain. The figure below shows a router that creates an internetwork and breaks up broadcast domains.

The network in the figure above is a pretty cool. Each host is connected to its own collision domain, and the router has created two broadcast domains. And don’t forget that the router provides connections to WAN services as well! The router uses something called a serial interface for WAN connections, specifically, a V.35 physical interface on a Cisco router.

Breaking up a broadcast domain is important because when a host or server sends a network broadcast, every device on the network must read and process that broadcast—unless you’ve got a router. When the router’s interface receives this broadcast, it can respond by basically saying, “Thanks, but no thanks,” and discard the broadcast without forwarding it on to other networks. Even though routers are known for breaking up broadcast domains by default, it’s important to remember that they break up collision domains as well.

There are two advantages of using routers in your network:

• ·        They don’t forward broadcasts by default.

• ·        They can filter the network based on layer 3 (Network layer) information (e.g., IP address).

Four router functions in your network can be listed as follows:

• ·        Packet switching

• ·        Packet filtering

• ·        Internetwork communication

• ·        Path selection

Remember that routers are really switches; they’re actually what we call layer 3 switches (we’ll talk about layers later in this tutorial).

 

When you look at the figure above, you’ll notice that the router is found at center stage and that it connects each physical network together? We have to use this layout because of the older technologies involved–—bridges and hubs.

On the top internetwork in the figure, you’ll notice that a bridge was used to connect the hubs to a router. The bridge breaks up collision domains, but all the hosts connected to both hubs are still crammed into the same broadcast domain. Also, the bridge only created two collision domains, so each device connected to a hub is in the same collision domain as every other device connected to that same hub.

Notice something else: The three hubs at the bottom that are connected also connect to the router, creating one collision domain and one broadcast domain. This makes the bridged network look much better indeed!

SELF TESTS:

1. We’ve taken a look at the various RJ45 cables. Keeping this in mind, what cable is used between the switches in the figure below.

 2.   In the figure below, what cable is used between;

·        the switches and the hosts,

·        the switches and the router and

·        the router and the console?

Check the next tutorial class for the answers. More examples and figures will be given in the next class for more clarification on the topic.

YOUR BUSINESS AND ITS NETWORK

In this post, I'll be introducing you to networking your business according to its structure.

As a  start-up owner, by now you must have considered the location and the kind of business you want to go into. The kind of business will determine how you'll set up the IT structures within. You also should have considered your budget, the kind of people you are working with and the kind of person you are. If you have employees that forget to turn of the lights after a work day then you know you'll have problems with your power management. If they are the kind that are addicted to the internet, you'll definitely have problems with productivity and work ethics, especially if your business is the type that has little to do with the internet. If this is the case, then I guess you might want to enroll such employees into a training course on, "The Internet-phobic Personnel and How To Become One." 

Whatever the business, you'll need to consider the business structure with respect to its departments and how you want your "intradepartmental" and "interdepartmental" communication to be via the networked computers.

Of course, employees within a department should be able to share files with each other without having  to move from their seats. It now depends on whether you want different departments to be on the same network. For example, you might want the sales department to be connected to the marketing department and not to the research department or the transport department to be connected to the sales department and not the human resources department.

Another thing to put into consideration is the number of employees you have and wish to have in the next few months. This is necessary because it will determine the number of computer systems, the kind and number of networking devices you need to get. Learn more about departmental networking in the upcoming network devices and subnetting tutorials.

Coming in my next free services: Basic network design for a small office. You don't just mount computer systems in an office and connect them, you have to take cost into consideration. See the different ways computers can be arranged in an office to reduce cost and increase performance.

Tutorial 1: A brief intro.

Before we really go into networking proper, you’ve got to understand the big picture and then
the answer to the key question, Why is it so important to learn networking, Cisco internetworking to be precise?

Networks and networking have grown exponentially over the past few years. They’ve had to evolve at light speed just to keep up with huge increases in user needs such as sharing data and printers as well as more advanced demands such as videoconferencing. Unless everyone who needs to share network resources is located in the same office area (an increasingly uncommon situation), the challenge is to connect the sometimes many relevant networks together so all users can share the networks’ wealth.

A basic LAN (Local Area Network) network can be connected together using a hub. This network is actually one collision domain and one broadcast domain. I’m sure you have no idea what this means. Not to worry, more light will be shed on this as the turorial goes on.

In the next tutorial, I’ll be introducing you to basic internetworking. I mean Ethernet cabling and how to use it.  For clarity on issues, just leave a comment.