These are my notes on physical topologies in Networking.
Intro
Networking is a popular topic. Microsoft has extensive needs in their systems. Cisco certifications are always highly sought after. It only helps your career if you have knowledge of networking basics. It is how we play our lan games and how our phones communicate also. Being a very popular subject because of Cisco jobs and equipment especially, I wanted to start a series to address it. At the most fundamental level you have the different topologies. Networking topology, at its core, describes in a high level view how a network is set up. There are many different kinds of topologies such as Ethernet, bus, ring, star and some other obscure ones. In actuality though, Ethernet is the only one worth talking about these days as most of the others have fallen out of use.
Networking Basics
Before I go any farther I need to cover a few basics. This will be at a real high level but I will expand this as time goes on. To make a network you need a few pieces of correct and compatible hardware.
Computer
Network Card
Cabling
Wireless Networking
Router/Switch
Computer
The computer can be just about anything from a small netbook to a powerful workstation. Having them roughly the same type will help though. They will all need network cards. These cards are usually PCI based and do the communications with the network. Computers and workstations can have more than one network card in them now too. Cabling also has several options. The most common is category-5 cable but category-6 is making headway and superior. The cables will connect to the router or switch, depending on where it is in the chain of devices.
It will not matter if the computer is a Mac, Windows, and Linux machine. They will all have a network card these days where you can plug an ethernet cable into.
Network Card
Network cards do the communicating with the network. Your cabling plugs into them. There are many standards today which govern their usage. There are so many because they describe the types of cable used, distances involved and other such things that do not matter to most people. The most important thing is the speed which is usually of the gigabit variety. There are many reliable vendors today that make network cards. Many kinds of devices these days can be networked. They include computers, printers, scanners, thermostats, cameras, doorbells, and even sound systems. Network cards often have indicator lights on them so it is easy to see the status of that particular connection.
Cabling
Ethernet technology is by far the most prevalent type of cabling in the networking world today. You will actually have a hard time finding anything else. The main reason for this is cost as equipment and cabling are key factors and the speeds reachable by it. It is a protocol. That means it has the rules that the devices try to follow.
Category 5 cable is the most used cabling because there is so much of it out there. It is good and works with anything. Category 6 cable is what you should buy if you have newer equipment as it is superior to older cable types.
RJ11 - this is the old telephone connector but is also used for broadband connections.
RJ45 - this is the connector for Ethernet cabling.
RJ48 - connector used for T1 and ISDN connections.
DB-9 - used for RS232 serial connections which is used for management
DB-25 - older parallel printer type connection.
BNC - good connector used in both IT and AV industries.
Twisted Pair Cabling
The ISO/IEC 11801 standard governs how twisted pair cabling is used. One type is of course Catergory 5 cabling which can be either 100 mbit Ethernet or 1000mbit Ethernet. You would have to have a compatible network card that used one or both of those speeds. The current version is category 6 cabling and it is even faster at theoretical speeds of 10 gbit. Twisted pair cabling is then divided up into UTP (unshielded twisted pair) and STP ( shielded twisted pair).
Unshielded Twisted Pair - made of insulated copper wires that have been twisted around each other to form wire pairs.
Shielded Twisted Pair - shielded twisted pair cable is used where there is a lot of inteference such as around power wires.
Wireless Networking
Wireless networking is the other technology used today and it is used by everyone. It exists along and works with Ethernet networks greatly and is a core component of all networks today. It has standards associated with it also which mostly designate speed differences but also how it works. Examples of standards are a,b, g,n, and the current one today, the AC standard. AC is currently the fastest of the ones in major use today but there are more improvements and thus more standards out there but they are not in common use yet.
Router/Switch/Access Point
Most people are aware of the common router you can buy at consumer electronics stores. These are actually access points equipped with routing functionality. They use radio waves to communicate with the network card in your laptop or another access point when you want to extend the distance of your wireless network.
Wireless networks are governed by the IEEE 802.11 standards. Access points are used to provide a hot spot for wireless clients in the vicinity. Wireless networks operate as a hub and spoke topology. They also are shared and use CSMA/CA.
Routers will often have a small built in firewall to help with security. There are numerous types of functionality that can be built into these pieces of equipment. I cover many of these in other articles. One important thing to remember is that routers are usually at the edge of your network.
Switches are usually connected to the router at some point and help segment your network. You will want this if you have multiple buildings or areas with computing equipment in them. These can be small 4 port devices to larger 48 port devices. Switches can also be un-managed or managed network devices.
Routers and Access Points
Access points have a limited number of users it can handle. More users connected to an access point means lower performance per user. Access points will do better if they do not have too many channels overlapping. A characteristic of access points is they use roaming to give a user the best signal possible.
This means as a user moves around then then their device will connect to the closest access point in order that they get the strongest signal possible. To do this effectively the access points must have the same SSID (Service Set Identifier) and authentication information.
If you have a lot of access points in a general area then you will want to use a wireless controller. This controller device can manage multiple access points and make it easier for the admin to know what is happening with the network. The controller does this by the LWAPP ( Lightweight Access Point Protocol).
A wireless network is often on its own VLAN (Virtual Local Area Network). This helps segment the traffic and keep it from bothering other parts of your network that may be more vital.
Topologies
A network topology is the physical layout of your network. It is the cables, routers, switches, workstations, and hardware like that. Cables, for example, are something like category-5 or category-6. Routers are what accepts the signal from your ISP usually. Switches help distribute your network.
They also segment it as well when needed. Workstations are usually your PC's or laptops that you do the work from. There are many different kinds of topologies. Network engineers have been designing layouts as long as networks have been around. The following is a partial list of the most popular:
Bus
Star
Ring
Mesh
Networking Basics: Bus Topology
This is one main trunk that splits off to each device point. Each device connects to the main trunk. They used to be really popular but not anymore. The trunk was a single point of failure so not good these days. While it was easy to set up, it became very slow in higher traffic networks. It is a topology where a straight line of cable connects all of your devices. This is how the original Ethernet networks were done in businesses.
Networking Basics: Star Topology
The star topology is most often used today. It is also quite simple. Get a router, lots of cable, and any more switches that you might need and just connect all of your devices. This is a very flexible set up. It is more expensive with the cost of cabling and extra switches.
One of the great things about this set up is that you can add or remove devices without disrupting your whole network. For example, if a workstation goes down and you have to work on it you can just disconnect and fix it. This will not affect anything else.
Ethernet hub and switch networks all use a Star topology.
Networking Basics: Ring Topology
This is very simple. A ring network just forms a loop. Each workstation is connected to 2 others. The last one is connected to the first in this set up. It is easy to figure out where a workstation is messing up at. The worst thing about this set up is that if one computer goes down then the rest start having problems passing information along the network.
The Ring topology is similar to a bus topology in that there is a single point of failure. This type of network operated by passing a token around the network and only the device with the token can transmit data.
Networking Basics: Mesh Topology
Mesh networking is still used a lot in wireless applications. This set up is going to be more complicated and more expensive. It is more complicated because all of the devices are interconnected. Settings have to be adjusted on the switch because of this. The switch has to allow for traffic to come from everywhere at once. It is more expensive because of the cabling mostly. You also have to have a switch capable of this too which may add some cost as well.
Mesh networks are common in WAN's (wide area network). In this topology every device talks to every other device. This is very expensive to implement as the number of connections grow substantially with every new workstation. This is why partial meshes are used a lot and the full mesh.
Point To Point Networks
You would use this type of network to connect different locations to make them the same network. Since each location would have its own router you would just connect these two routers together most likely in a serial connection.
Client Server Networks
This is the most common type and what we often associate with a network traditionally. In this type of network the network services are provided by a server or multiple servers. Network services could be:
printing
email
active directory
web page
The server would decide what device or uses gets to access resources.
Peer To Peer Network
There are not really any servers in this kind of network. All the workstations are independent and equal. To get this kind of scenario to work you would have to have an account made for every computer that wanted to access your resources. Peer to Peer networks are usually small. The reason why they are small is that network resources become very slow in a large network.
Conclusion
As you can see there are several types of topologies and ways to design networks. Each one will have their advantages and the best situation to use them in.
Networking is not terribly hard to learn. It does take some diligence though. You also have to practice the concepts often. I have just introduced the basics in this guide. In future articles we will talk about more complicated practices but I will still be referencing these basic concepts occasionally. They all build on each other. Networking is very fun though. So later when it gets harder just remember how cool it is to understand how routing and the internet really works!
