Switch question

[MadMike]

Awhile back, we got into a discussion about switches vs. routers. Not sure I understood everything, but the help is always appreciated.

My project is pretty much up and running. It works great, but once in a great, great while, I would hit a bit of a lag.

I'm thinking about wiring just the server, at least to start with. Of course, this will probably annoy Pedersen slightly, since we spend about 3 hours trying to get it to work wirelessly.

I figure that having one less device using the wireless would help, and if not, then I can think about ripping up the wall again and wiring the rest of the devices. And copying stuff to the server would probably go a lot quicker too, since my main computer is wired to the network.

If I'm understanding our previous discussion correctly, I could buy a switch, connect it to the router, and connect the switch to the server. Is this correct, or am I way off base?

I'm looking at this switch. Would this one be OK, or should I get something different?

[Pedersen]

I'm thinking about wiring just the server, at least to start with. Of course, this will probably annoy Pedersen slightly, since we spend about 3 hours trying to get it to work wirelessly.

Don't worry, it doesn't annoy me in the slightest. I was worried that that would happen to you, even still. I'm sorry it is/does, but at least you have the option to wire it up (even if it does take some extra work for you).

If I'm understanding our previous discussion correctly, I could buy a switch, connect it to the router, and connect the switch to the server. Is this correct, or am I way off base?

Nope, you're right on the money.

I'm looking at this switch. Would this one be OK, or should I get something different?

That's one of the ones I've got and use, and like. As I recall, you've got a LinkSys router, too, so that should work very nicely together.

[Brightglaive]

I would strongly suggest a switch for anything you deem a "server" (e.g web server, file server, domain server, print server, archive server.... etc.) Wireless access to a server eats up the wireless bandwidth especially if the server is a file server or web server or FTP server. While the server is serving up the requested content none of the other devices on the wireless network can transmit. This can be a HUGE problem if you have large file transfers. Case in point, I had a medical office wanting to transmit 4GB graphic files (MRI scans) from the MRI machine (wired connection) to an archive server (with a wireless card). Needless to say BAD IDEA. I told them they should use a wired connection for the server. I also had a graphic printing company trying to transmit 125 MB files from a scanning station with a wireless card over an 11 Mbps wireless link to the wireless print server. They wondered why they were having such problems with print jobs backing up. (Well DUH!!!!)

(Tech explanation: Wireless uses something called time division duplexing. This means it's basically listening half the time and transmitting half the time. 54Mbps is only the half duplex speed meaning you are actually transmitting 27Mbps and listening for up to 27Mbps. Basically you are getting the same speed as a 27 Mbps full duplex link. Wireless overhead eats up 3-7 Mbps of the bandwidth. This leaves about 20Mbps. divide by 8 [8bits=1 byte] to get about 2.5 Million Bytes per second. Now a gigabyte is 1,073,741,824 Bytes or about 1074 Million Bytes. This would take about 7 minutes to transmit over a 54 Mbps connection assuming that no one else is trying to transmit and you are getting 100% efficiency and you are going from a wired connection to a wireless server. If you are transmitting to another wireless device you would have to double the time because the wireless access point/router would then have to retransmit the data it just recieved to the other wireless device. So now you're up to 14 mins for a 1 GB file or 1.4 minutes for a 107 MB file. If you have any other devices on the network this will slow this wireless transfer down considerably if they are also transmitting and receiving files. Interference from other wireless APs/routers on adjacent channels will also lower your throughput. This is also assuming that everyone is at the same datarate. If someone is transmitting to the AP at a lower datarate like 11 Mbps then your total throughput will drop as well. Hidden nodes, 802.11b detection, long slot times and other wireless issues can make your ap/router grind to a slow crawl for LONG LONG LOOOOOONNNNNGGG time. Conceiveably extending your transfer times to 125 MB per 15min. or longer )

A switch would be ideal because of how fast the transfer speeds are. Most routers have additional processing tasks (routing, DHCP & DNS relay, access lists, authentication etc.)that slow down the transfers to low levels and high latencies. A switch doesn't run these processes and uses a specialized high-speed processor called an ASIC. This usually translates to wirespeed transfers (up to 200Mbps on a full-duplex fast ethernet link or up to 2000Mbps on a full-duplex gigabit link) here's the obligatory weblink for more explanation:

http://www.circuitcellar.com/library...0502/index.htm

<shameless plug> Anytime when you can use a Cisco or Cisco/Linksys device, do it. They are quality devices. </shameless plug>

(P.s. I work for Cisco Systems )

[Pedersen]

Thank you! I've always been peripherally aware that wireless wasn't perfect, but could never explain the why very well. Now I have an actual quality answer that I can give. It works great for web surfing and the like, but I always hook up to wired for big file transfers, and now I know why

[MadMike]

Thanks you everyone for your help. I picked up a switch the day after I posted this, and if nothing else, copying files to the server goes a helluva lot faster. I can also wire the media PC if I really need to, but I'm going to see how it goes now that I have the server wired, and my new antenna has arrived.

[Der Cute]

Mike:

I'm an advocate of wiring. Personally, I don't know much about wireless, BUT at the same time I know there is 50% overhead along with the payload, and THAT in itself makes me leery.

Along with the ability to crack and hack and listen and snoop so easily on wireless. I'm just ....paranoid, I guess...

Mike:
A switch is different from a router in that a switch reads MAC addresses and uses them instead of IP's.

the 7 layer OSI :
APPLICATION (7) Like ...Netscape or FF
PRESENTATION (6) transparent to users but getting it to the screen
SESSION (5) how the puter/nic knows the difference between packets for a redhead and a blonde
TRANSPORT (4) how the stuff gets from Point A to Point B (tcp)
NETWORKING (3) the Internet Protocol - Routers work on layer 3
DATA LAYER (2) the Mac addresses, - Switches work on layer 2
PHYSICAL (1) the actual physical stuff ..copper or fiber or radio waves the info flys out on.

Now.
ARP: address resolution protocol ....LIKE internal DNS.

What happens inside a switch is that .....you plug in 15 units to the switch.
The switch's firmware hears that mac address 00 1A 1B 2C 2D FA FF is on Port 1.
Records this in Arp table.
You need to send file from Puter A to Puter B (Port 1 to Port 5)
Packet of TCP/IP has headers (IP addy) and also other little bits and bobs of info.
Packet leaves Puter A and enters switch.
How does switch know that that specific packet goes to Port 1?

Because the packet also includes a MAC address with the header, from Puter A - Source, and a name or IP address for the Destination.

So when the switch sees packet coming in, it compares Destination to ARP table, and says OH yeah, you go to Port 5, nobody else on this switch needs to hear you.

A Hub would just hear packet and fling packet to all ports, not caring. Whomever needed the packet got it, whomever didn't, ignored it (lotsa traffic).

Hub: Stupid broadcasting unit.
Switch: Intelligent unit to connect single pc's to make it look like they're almost one to one. Cuts traffic
Router: uses IP addressing instead of MAC to filter needed /un needed packets for the clients it has. Directs traffic by IP. Can also be changed to use QoS (quality of service aka Voice over IP or Video more important that .txt files)

this is stuff I like. Can you tell?

Cutenoob

[Brightglaive]

The beauty of a switch is the hardware and the speeds at which they transmit. Where a router has a multi-purpose processor running a lot of different processes, a switch has an ASIC (Application Specific Integrated Circuit). When a router is running a process it does so "in software". Basically it depends on the software it's running to specify what actions are taken on a given input. In a switch the action has been coded into the hardware. In comparison to computers it's like the difference between (for those oldsters out there) having a math coprocessor or not having a math co-processor or having 3d hardware acceleration or not having it and emulating it in software or having a hardware modem as opposed to a "Winmodem" or (my favorite) having a hardware VPN accelerator vs. using your computer's processor for 3DES/AES encryption. there's always a huge difference between hardware acceleration and software emualtion. An ASIC is hardware acceleration for layer 2 (L2) switching or for layer2/layer3 switching.