Sign in with
Sign up | Sign in

Wired Network Topologies

LAN 102: Network Hardware And Assembly
By

Each computer on the network is connected to the other computers with cable (or some other medium, such as wireless using radio frequency signals). The physical arrangement of the cables connecting computers on a network is called the network topology.

The three basic topologies used in computer networks have been as follows:

  • BusConnects each computer on a network directly to the next computer in a linear fashion. The network connection starts at the server and ends at the last computer in the network. (Obsolete.)
  • StarConnects each computer on the network to a central access point.
  • RingConnects each computer to the others in a loop or ring. (Obsolete.)


The following table summarizes the relationships between network types and topologies.

Network Cable Types and Topologies
Network Type
StandardThin (RG-58) coaxialTopology
Ethernet
10BASE-2Thin (RG-58) coaxialBus
10BASE-5Thick coaxialBus
10BASE-TCat 3 UTP or betterStar
Fast Ethernet 
100BASE-TX Cat 5 UTP or betterStar
Gigabit Ethernet1000BASE-TX Cat 5 UTP or betterStar
1000BASE-TXCat 6a UTP or better
Star
Token-Ring
(All)
UTP or STPLogical ring


The bus, star, and ring topologies are discussed in the following sections. Wireless networking, which technically doesn’t have a physical topology as described here, does still employ two logical (virtual) topologies, which I discuss as well.

Bus Topology

The earliest type of network topology was the bus topology, which uses a single cable to connect all the computers in the network to each other, as shown in the image below. This network topology was adopted initially because running a single cable past all the computers in the network is easier and uses less wiring than other topologies. Because early bus topology networks used bulky coaxial cables, these factors were important advantages. Both 10BASE-5 (thick) and 10BASE-2 (thin) Ethernet networks are based on the bus topology.

A 10BASE-2 network is an example of a linear bus topology, attaching all network devices to a common cable.A 10BASE-2 network is an example of a linear bus topology, attaching all network devices to a common cable.

However, the advent of cheaper and more compact unshielded twisted-pair cabling, which also supports faster networks, has made the disadvantages of a bus topology apparent. If one computer or cable connection malfunctions, it can cause all the stations beyond it on the bus to lose their network connections. Thick Ethernet (10BASE-5) networks often failed because the vampire tap connecting the AUI device to the coaxial cable came loose. In addition, the T-adapters and terminating resistors on a 10BASE-2 Thin Ethernet network could come loose or be removed by the user, causing all or part of the network to fail. Another drawback of Thin Ethernet (10BASE-2) networks was that adding a new computer to the network between existing computers might require replacement of the existing network cable between the computers with shorter segments to connect to the new computer’s network card and T-adapter, thus creating downtime for users on that segment of the network.

Ring Topology

Another topology often listed in discussions of this type is a ring, in which each workstation is connected to the next and the last workstation is connected to the first again (essentially a bus topology with the two ends connected). Two major network types use the ring topology:

  • Fiber Distributed Data Interface (FDDI)—A network topology used for large, high-speed networks using fiber-optic cables in a physical ring topology
  • Token-Ring—Uses a logical ring topology


A Token-Ring network resembles a 10BASE-T or 10/100 Ethernet network at first glance because both networks use a central connecting device and a physical star topology. Where is the “ring” in Token-Ring?

The ring exists only within the device that connects the computers, which is called a multistation access unit (MSAU) on a Token-Ring network (see the following image).

A Token-Ring network during the sending of data from one computer to another.A Token-Ring network during the sending of data from one computer to another.

Signals generated from one computer travel to the MSAU, are sent out to the next computer, and then go back to the MSAU again. The data is then passed to each system in turn until it arrives back at the computer that originated it, where it is removed from the network. Therefore, although the physical wiring topology is a star, the data path is theoretically a ring. This is called a logical ring.

A logical ring that Token-Ring networks use is preferable to a physical ring network topology because it affords a greater degree of fault tolerance. As on a bus network, a cable break anywhere in a physical ring network topology, such as FDDI, affects the entire network. FDDI networks use two physical rings to provide a backup in case one ring fails. By contrast, on a Token-Ring network, the MSAU can effectively remove a malfunctioning computer from the logical ring, enabling the rest of the network to function normally.

Star Topology

By far the most popular type of topology in use today has separate cables to connect each computer to a central wiring nexus, often called a switch or hub. The following figure shows this arrangement, which is called a star topology.

The star topology, linking the LAN’s computers and devices to one or more central hubs, or access units.The star topology, linking the LAN’s computers and devices to one or more central hubs, or access units.

Because each computer uses a separate cable, the failure of a network connection affects only the single machine involved. The other computers can continue to function normally. Bus cabling schemes use less cable than the star but are harder to diagnose or bypass when problems occur. At this time, Fast Ethernet and gigabit Ethernet in a star topology are the most commonly implemented types of wired LAN.

Display all 20 comments.
This thread is closed for comments
  • 5 Hide
    JasonAkkerman , November 2, 2011 4:37 AM
    Lots of good information there. Lots of history too.
  • 0 Hide
    KelvinTy , November 2, 2011 7:45 AM
    O... I thought all CAT5 are able to transmit 1000Mbps signals BEFORE reading this article... It's kind of weird ~_~" that I can get 5.X MB/s download speed = ="
  • 4 Hide
    Reynod , November 2, 2011 10:28 AM
    Don could you talk to Chris A and Joe and see if we could give a few hard copies of this book away as prizes for some of our users here in the forums who work hard to help others?

    How about a copy for each of the users who make the top ranks for the month of November ... under the Hardware sections of the forums?


    :) 
  • 0 Hide
    Anonymous , November 2, 2011 1:12 PM
    mixer device
  • 2 Hide
    JasonAkkerman , November 2, 2011 1:18 PM
    They make it look like making a cable it so easy, and it is, after the first few tries. Also, making one or two cables isn't too bad, but don't let yourself get talked into making 50 two foot patch cables. Your finger tips will never forgive you.
  • 0 Hide
    thrasher32 , November 2, 2011 1:45 PM
    Great information.
  • 0 Hide
    xx_pemdas_xx , November 2, 2011 1:57 PM
    JasonAkkermanThey make it look like making a cable it so easy, and it is, after the first few tries. Also, making one or two cables isn't too bad, but don't let yourself get talked into making 50 two foot patch cables. Your finger tips will never forgive you.

    I got talked into making 10...
  • 1 Hide
    spookyman , November 2, 2011 2:11 PM
    JasonAkkermanThey make it look like making a cable it so easy, and it is, after the first few tries. Also, making one or two cables isn't too bad, but don't let yourself get talked into making 50 two foot patch cables. Your finger tips will never forgive you.


    Oh I don't know. I have made several thousand patch cord over the past 18 years.

    All you need is a high quality crimper, good cutters and small screw driver. You are set.
  • 2 Hide
    silveralien81 , November 3, 2011 2:56 AM
    This was a great article. In fact it inspired me to buy the book. I'm happy to report that the rest of the book is just as well written. Very educational. A top notch reference.
  • 2 Hide
    neiroatopelcc , November 3, 2011 10:27 AM
    Read the first page. Seems like well written stuff, but not exactly written for my type of user. Also it seems to be igoring a lot of stuff. For instance it sais the network runs at the speed of the slowest component and will figure it out on its own. This isn't true. If you run a pair of 1000TX capable nics on old cat 5 cable (without the e), it'll still attempt to run at that speed, despite the massive crc errors it might generate. Also, if you're running on 'old gigabit hardware' it won't nessecarily have support for 10Base-T speeds. Also, not all firmware has autonegotiate or automdix support, thus you sometimes have to specificly set the speed between links. This is mainly for fiber links though, which seem to have been ignored entirely.

    Anyway. As I said, I think it's well written and probably quite suitable for people who don't know anything about networks (except it seems to assume people know the osi model). I'll go see if the other chapters are equaly basic.
  • 0 Hide
    fixxxer07 , November 4, 2011 1:28 AM
    kelvintyO... I thought all CAT5 are able to transmit 1000Mbps signals BEFORE reading this article... It's kind of weird ~_~" that I can get 5.X MB/s download speed = ="


    5 MBps = 40 Mbps... so it's not that weird. xD
  • 0 Hide
    dthurber , November 4, 2011 2:00 PM
    Great article with lots of information. The crossover cable mentioned would work for 10/100, but for gigabit ethernet you must also crossover the blue and brown pairs. Unlike 10/100 ethernet, gigabit ethernet uses all eight conductors.
  • 1 Hide
    cangelini , November 4, 2011 7:59 PM
    reynodDon could you talk to Chris A and Joe and see if we could give a few hard copies of this book away as prizes for some of our users here in the forums who work hard to help others?How about a copy for each of the users who make the top ranks for the month of November ... under the Hardware sections of the forums?


    Heya Reynod,

    We had access to 10 copies of it for a contest that ran with the first few pieces of the book, but those were given away already.

    I agree that it's a great idea to reward the most active forum users, though. I'll get together with Joe and see if there's anything we can do there!

    Have a great weekend,
    Chris
  • 0 Hide
    Reynod , November 6, 2011 11:28 AM
    Thanks Chris.

    I feel a bit stupid now I missed it.

    It would be great if you could do something again though.

    I did PM Don Saturday to ask him.

    Cheers

  • 0 Hide
    neiroatopelcc , November 21, 2011 6:06 AM
    patch cables of those small lengths you just buy readymade - they're more sturdy anyway, and you can get them as any cable type (cat5e, 6a etc) .. and long's you don't add old cat5 or mix shielded with unshielded, cables really are the least difficult part of network building - although cisco want you to believe otherwise.
  • 0 Hide
    juanc , November 25, 2011 2:18 PM
    completely amazed at how many errors are in page 2
  • 0 Hide
    juanc , November 25, 2011 2:33 PM
    Either I'm missing to read something or the article on page 3 does not note, that to make Patch Cables you must use a different type, multi-filament copper cable instead of the standard in-wall one-wire solid copper conductors that get cut when you crimp. Huge mistake
  • 0 Hide
    juanc , November 25, 2011 2:44 PM
    Shielded twisted pair (STP) refers to the amount of insulation around the cluster of wires

    There is no "amount" it does have a shield.

    it was first thought that shielding the cable from external interference was the best way to reduce interference and provide for greater transmission speeds. However, it was discovered that twisting the pairs of wires is a more effective way to prevent interference

    No. Shielding is better. But the trick on twisting is that we are talking about "differential" signals. If not, twisting would be useless. Twisting to cables cancel each others emissions and emissions from other places to the cable are canceled too.

    10GBE pros say you should not wire UTP but only STP.

    Need cable lengths longer than the lengths you can buy preassembled

    Never buy preassembled cables. Can't assemble cable as I said before on mono-filament cable.
    One filament wires can't be twisted or take turns or >90 degrees. There's a big chance they can break. Can't wire thru a pipes with the RJ45 plug on it.

    Use Jacks. Buy machine assembled/tested multi-filament patch cords from the jack to the computer/router/printer/switch, whatever.
  • 0 Hide
    Slothy , January 13, 2012 11:57 PM
    I read this article as it was linked in the power supply guide posting, which I thought (on perusing it quickly) seemed rather well done. However, this article is so attrocious (both in inaccuracies and it's horribly outdated information) that it draws into doubt the quality of the original article that brought me here. I'm not just some Joe going off on a rant without knowing a thing, and my apologies as I am sure that this was likely intended for average Joe who doesn't have a strong base in networking, but even for that, it could have been written immensely better. I don't know if the author is to blame or the technical editor.

    First off, as a disclaimer, I didn't bother reading the wireless section. Stuff has been changing too rapidly the past few years to even bother, and it is ultimately so simple nowadays that you shouldn't even have to bother with the wireles options. What I did see of wireless information (such as range) was horribly inaccurate. In my experience with most indoor environments, you'll be lucky if you get a *reliable* signal at a fraction of the 150 feet he mentions.

    Simple advice for wireless: Buy a dual-radio N-capable wireless router and then decide if you're going to use N-capable internal wireless cards or USB dongles for any devices you have that do not include integrated wireless. Be warned that in my experience, many wireless routers designed for home use work fine for wireless devices accessing the internet, but when attempting to transfer data between a wired and wireless device, the router will act as a bottleneck, often running at speeds lower than what standard (10 Mbps) ethernet will provide. If you plan on hooking up a device such as a home server or NAS device to your home wireless router, be careful what you pick and either fork out the money for a higher-end SOHO/SMB device or read your reviews thoroughly and ensure that you're getting exactly that device (down to the revision number even, sometimes).

    This article clutters the users mind with unnecessary information and technical details which to knowledgeable persons will already be apparent, and recognized as often incorrect; and for the unknowegeable reader - incorrect and irrelevant but taken as true. To rattle off a few
    -switches and hubs, while sharing some features (they're small, blockish and have multiple ports) are also different at an operational level - switches are OSI layer 2 devices, while hubs are electrical devices operating at OSI layer 1.
    -Packets do not get where they need to go because of MAC addresses; frames get where they need to go thanks to MAC addresses while packets are at OSI layer 3 and utilize IP addresses for routing.
    -If you want to see your MAC address via ipconfig, use ipconfig/all. ipconfig on its own will not provide you with this information.

    If I wanted to take a closer read or go through it again, I'm sure I could pull out atleast as many errors as I listed above, but I've gotten enough of my steam out about someone publishing yet more outdated and erroneous technical info or advice in the realm of networking and IT. Please, if you're going to write a tech article, do it with a purpose, stay true to it, make sure you have your stuff down pat, and damn well update it if you're going to re-publish it.

    No one cares about coaxial ethernet anymore, unless you're over the hill or working in some industrial environment with networked machinery, in which case I hope you're not getting your expertise from this article.

    PS. I'd still like to say thanks to Tom's Hardware and that they're an invaluable resource - not just for their reviews and articles, but for the user community they have generated as well. But with that said - is it just me, or is Tom's IT site just one big stream of advertisements in the guise of articles, news stories, and white papers?
  • 0 Hide
    Anonymous , August 8, 2012 4:38 AM
    why are you using blue and brown wires even though they are of no use?