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Hubs operate at ISO layer 1 - physical layer, Switches operates at ISO layer 2 - data link layer, and Routers operate at ISO layer 3 - network layer.

HUB When Ethernet was originally designed it used a single fat coax called a backbone. Individual hosts were physically connected to the backbone. This created a party line. Each host has to listen for the backbone to be idle before it started talking. It is possible more then one host will start talking at the same time, in that case the messages collide making them unintelligible. This condition is detected each transmitter stops talking and waits a variable interval before attempting to talk again. The Ethernet network is called a collision domain, since all devices must wait until the line is clear, and may inadvertently interfere with one another.

When Ethernet was modified to run over Unshielded Twisted Pair (UTP) Category rated wiring the original coax backbone was shrunk within the hub, called a collapsed backbone. Functionally a hub operates exactly as the old coax backbone. The ports on the hub provide a point-to-point connection to the Ethernet interface in each computer. With a hub each node must wait for the network to be idle and detect collisions between multiple nodes.

SWITCH As Ethernet networks grew in speed and size the party line nature was recognized as a performance limitation. Switches eliminate the collision domain and work much like the telephone switching system.

When an Ethernet packet arrives at the switch the destination MAC address is examined and the packet is switched to the proper physical port. Each Ethernet interface has a Media Access Controller (MAC) 48-bit address assigned by the hardware vendor. The switch remembers which MAC addresses are connected to each physical port. If the Switch does not know which physical port to use it floods the packet to all connected devices. When it gets a response it updates its internal MAC address table.

This means Port A can talk to C at the same time F is taking to B. This greatly increases overall performance even though it does not change the speed of individual connections. Because the collision domain is eliminated connections are able to use full duplex, hosts can transmit and receive at the same time improving performance even more.

ROUTER A router is used to interconnect multiple networks. The Internet is literally Internetwork -- a network of networks. Internet routers work on IP addresses to determine how best to interconnect the sender to the destination. Because routers work at the IP layer different physical networks can be interconnected, Ethernet, Token Ring, Sonet, even RS232 serial used for dialup can carry IP packets.

Routers intended for home use include Network Address Translation (NAT). This allows a single address assigned by the ISP to be shared by multiple hosts connected to the local network.



Feedback received on this FAQ entry:
  • good but there is no graphs

    2014-11-12 03:01:34

  • "which MAC addresses are connected to each port" huh? previous sentence says each ethernet interface has a MAC. I've read that each eth. int. has a 0-65535 wide port range. Over 65000 addressable ports is alot but, it's the exact same number range for each interface. You've done excellent distilling things down, but I find the topic of what the switch remembers confusing. Perhaps you could expand a wee bit on that?

    2014-09-26 05:43:29

  • dear editor, we are expecting more on ur explanation, somehow, it ended up with disappointment answer... kindly response.

    2014-08-27 08:08:41

  • Router doesn't have all the information I neeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeed

    2014-03-03 06:47:20

  • is router has any layers like data link layer, network layer and physical layer?? if it has , how they are working..?? how packet flows through those?

    2014-01-23 05:55:37

  • i think it should be more clear about router and switch.

    2013-09-26 01:28:45

  • cant explain anything in clear way

    2013-08-27 12:49:03

  • please explain how switch works with an example

    2013-08-26 07:26:11

  • router explanation is not enough.

    2013-05-27 23:23:06

  • nice one....thank you

    2013-05-27 08:22:53

  • plzzzz explain router......

    2013-04-21 00:16:36

  • router is not clear

    2013-04-12 02:50:23

  • good work but not much more explain router.

    2013-01-16 10:53:29

  • As a refresher explanation, I think this explanation is great. However, I have a lot of general computing experience and have read a little about how networks work in the past. As a brand new learner to networks the above explanation may not be explicit enough.

    2012-11-21 02:43:22

  • i did like the switch explanation but i request for more on the router. It's wide as i do believe. Regards, SERAH a.k.a TT

    2012-07-19 03:02:44

  • good job this hub Switch & Router

    2012-07-07 03:34:39

  • plz explain more information about router.

    2012-07-04 00:53:10

  • Router is not properly understand.

    2012-05-16 05:48:49

  • plz explain router in detail

    2012-03-15 06:52:23

  • good one man..but it would be great if u explaint more about router.

    2011-05-23 21:11:06

  • As a refresher explanation, I think this explanation is great. However, I have a lot of general computing experience and have read a little about how networks work in the past. As a brand new learner to networks the above explanation may not be explicit enough.

    2010-11-14 10:22:55

  • good definitions:p

    2010-07-06 04:26:25

  • This has been the best explanation that I had read so far, keep up your excelent work

    2010-02-22 23:52:45

  • not much more explian router

    2009-12-01 03:12:35

  • Router explanation is not clear.

    2008-08-21 17:23:26



Expand got feedback?

by tschmidt See Profile edited by SYNACK See Profile
last modified: 2014-09-26 10:37:11