Network Question

silvsrfr
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My question is about network latency.

I have an 8 port switch at 1 GB speed connected to 3 workstations with 1 GB Nic cards. This switch is connected to another switch in a 1 GB port on a Netgear GS524 switch. Then the switch is connected out tot he world via a sonnicwall connection.

Please let me know if this is correct.... If all 3 users on the workstations were useing max bandwidth. Each of the 3 workstations would be getting 1/3 of the GB connection and that alone would be the bottle neck?

8 other switches are connected to the GS524  are connected to the main GS524 wich connects everything to the outside world. would this daisy chain slow down the network?

How could I trouble shoot a slow network if is only happens once in a while?
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Are you experiencing slow intranet speeds, or internet speeds? unless you are moving large files or streaming audio/video on your intranet (LAN) then you will probably not be reaching full bandwidth on any one PC for very long.

Once switches learn the routes, they should not bottle neck very much. It is usually recommended to limit it to 3 or 4 layers deep without some special switches or real planning.

If you are getting slow speeds moving files internally etc, then use a network product like SolarWinds (paid) or wireshark (free) to track what is going on and who is taking up the bandwidth. If you are experiencing slow internet/WAN speeds, that may be an ISP problem. You could also have someone on streaming audio/video like Pandora or Netflix.

Author

Commented:
The Slowness is both intranet and internet connections depending on what is going on. My thought is that they are really only getting 1/3 of a GB speed and on the 8 port switch. The uplink is a 1 GB port to another switch. All switches are at max 3 segments to the router.

I have ruled out the streaming of video and films by blocking this at the sonicwall with a rule.

I have also opened a ticket with our ISP.

Could you explain trouble shooting with wireshark a bit more?
I’m assuming that the slowdowns occur on the LAN...

If the 8-port switch delivers a total of 1Gbit then it will be the bottleneck for the three workstations. If the 8-port switch can deliver 1Gbit per port, then the bottleneck moves up the line to the Netgear switch, as its maximum throughput per port is 2Gbit.

The other eight switches will also hit the same port throughput limit, though the GS524 theoretically should be able to handle all nine running at full belt, as Netgear state its switching fabric capacity to be 20Gbit/sec; this doesn't leave much spare capacity though.

However, if every switch has a device connected and generating traffic, slowdowns will occur if the individual ports on the Netgear become swamped with requests, resulting in a lot of packet retransmissions.

Your network must be extremely busy...

Troubleshooting would entail monitoring the network to correlate slowdown with user activity, time of day, and so on.
If the slowdowns become a real problem, a beefier switch with more direct device connections to it, as opposed to cascading traffic through smaller switches, would work better as traffic would be more evenly distributed across the switch and individual ports wouldn't be overloaded.

washburnma makes a good point - if a user is hogging bandwidth with streaming media then internet access would suffer quite noticeably.
Khandakar Ashfaqur RahmanExpert/Consultant

Commented:
You need to ensure throughput of your LAN at first.
A good tool is "Xjperf":
http://code.google.com/p/xjperf/

1. Test between 2 computers  connected to your end switch
2. Test between 2 computers connected to Netgear
3. Test between 2 computers between end switch and Netgear switch

Be sure that throughput is ok.Then if your switch is a managable switch then you can install Cacti/MRTG.You could check per switchport usage and easily it would become understandable which computer is using more bandwitdh.Even if your switch doesn't support SNMP you could enable each computers SNMP service and check per computer NIC usage graph.
http://www.cacti.net/downloads/packages/Windows/Cacti-0.8.7i.exe

To analyze PKT/traffic you could go for Wireshark or Microsoft Network Monitor.

Author

Commented:
It hel;ped me get to the answer and resolve my question.

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