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we have 2 offices in separate buildings. there is an ethernet link between the two. The link is provided by the company that manages one of the buildings, and they provide us with 100Mbps bandwidth over ethernet cable (actually it passes as a vlan in their infrastructure, but to us it's completely transparent).

we have SERVER A in building A, and SERVER B in building B. The problem is that SERVER A is slow to be accessed from building B and SERVER B is slow to be accessed from building A. Also, our VOIP telephones in building A send their data to building B, where we have the central PBX.. the problem is that often there are cuts of 1-2 seconds and noises in the calls...

at the beginning I thought 100Mbps wasn't enough bandwidth, but the company that manages the link provided us with graphs that show that we use very little of it, just about 6-7Mbps in average. They suggested that our problem might be related to too many packets per second... basically you can have too many packets that flood the network (even if you are using only 7Mbps of the 100Mbps available) and our switches aren't able to handle it and drop packets..

is this true??

[EDIT] more info:

we are talking about 20 users in each office, the traffic that travels through the link includes:

  • internet from office A (the internet modem is in office B)

  • VOIP (the main PBX is in office B)

  • server-based office programs used by both offices (the server for one type of programs is in office B, the server for another type of programs is in office A)

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    You need to get someone in who knows about networking, this needs to be much more complex that it is to properly support the VOIP - and, not meaning to sound rude, I'm not sure you're the person for the job simply by the tone of this question - it's not easy stuff. – Chopper3 Aug 01 '13 at 13:00
  • I mean, 10/100 Nic cards are designed to handle, well, 100 Mbs. The number of packets hitting the network is limmited by that number by the sum of the size of all the packets in 1 second... Faulty equipment maybe? – Chad Harrison Aug 01 '13 at 13:02
  • 1. Those guys are jerks. If the issue is too many packets per second then it's with THEIR link (assuming that the traffic within each site doesn't exhibit this behavior). They ought to look at the specs of THEIR equipment and determine if your site to site traffic is exceeding the specs of THEIR equipment. 2. Take a look at latency and packet loss between the sites. The quality of any network connection is determined by three factors: A. Bandwidth - B. Latency - C. Packet Loss. You or they need to look at all three of these factors. – joeqwerty Aug 01 '13 at 15:06
  • so there is no such a thing as "too many packets per second" ? I mean, if we were flooding the link between the buildings with an insane amount of packets, the bandwidth usage should be close to the maximum (100Mbps) right? while now our bandwidth usage on that link as reported by the building manager is only 6Mbps.. –  Aug 02 '13 at 12:35

1 Answers1

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This sounds like the classic signs of either poor cabling or a duplex mismatch. Replace all the cables end-to-end, and work with your building manager to hard-code all of your ports and your devices connected to those ports as full duplex. Also see if you can get them to check/replace cabling in their infrastructure and check for duplex mismatches between their equipment.

Another thing to suspect is the building manager's switch gear. While your ports may only be using 6-7 mbps, it may be that another user (possibly the building manager) is using a lot of bandwidth on the link between the two buildings and starving your connection.

It could also be that you or your building manager have crap gear.

longneck
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  • what is the best way to check if a cable has any problem, without replacing it? –  Aug 08 '13 at 19:40
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    Get a wiring contractor to come out and analyze or certify the cable. Note I'm not talking about checking the pair order but doing an actual certification using a test like this: http://www.flukenetworks.com/datacom-cabling/copper-testing/dtx-cableanalyzer-series – longneck Aug 08 '13 at 20:10
  • regarding duplex mismatch, if I have two devices in "auto-negotiation" mode, and they both report to be working in full duplex, is there any reason to manually put them in "full-duplex" mode? –  Aug 10 '13 at 09:03
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    Usually no, if both ends are quality devices. However, it is worth it to test both ways. – longneck Aug 10 '13 at 15:48