Bandwidth Management help needed

Discussion in '3CX Phone System - General' started by instantexpert, Dec 22, 2008.

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  1. instantexpert

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    OK, I've been testing a setup with 3CX V7, Polycom 560 phones, a 3COM Baseline 2924-PWR Plus 24 port POE switch, two 24 port Netgear GB ethernet switches and a LinkSys RV082 router connected to a 2Mb full duplex wireless link (sparkplug.net) and using a Cogent sip trunk.

    I have been dealing with bandwidth issues for a few days. Our internet connection was dropping pings and having issues so I diagnosed the problem with our ISP and they made things better there. However, as I expected to happen, we have call quality problems when bandwidth is saturated by a speed test. So, I'm looking for solutions. The simple solution (already suggested on this board for someone else) would be to have the phones all go into a high priority port and the rest of the network traffic have lower priority. Unfortunately, this isn't an option as the reason we chose the Polycom 560 phones was so that we could have GB to all desktops and plug our computers in the port on the phone. The original installers used a single Cat 5e to each office and split the pairs with 2 pair for 100Mb ethernet and 2 pair for analog phone. We can repunch the exisiting cabling and give GB networking to all offices but only by sharing the same swtich port for pone and PC so just separating things by ports won't work.

    My router has a limited ability to prioritize certain types of traffic but, if I understand it correctly, the voice ports are dynamically assigned so I can't just prioritize certain ports. My router also has limited VLAN capability and my 3COM switch has VLAN capability. I'm exploring that path but it seems needlessly complicated.

    So, the questions I have are:

    -Is there anything I haven't thought of yet?
    -Is there a cost-effective router (<$1,000 US) that might prioritize SIP traffic to my external sip trunk provider?
    -Do I need to just purchase a couple more 3COM GB switches and bite the bullet on the VLAN?
     
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  2. William400

    William400 Well-Known Member

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    HI

    Since you are using a VOIP provider, and assuming you are using default settings for the provider, being 'PBX delivers audio' enabled and STATIC NAT then all SIP will be taking place over 5060 UDP and all RTP over the 9000 port range specific in the 3CX config. YOu shoudl allocate QOS to these ports.

    Your only other solution would be to get a separate internet link for VOIP and hence split the bandwidth over 2 connections.
     
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  3. instantexpert

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    OK, that makes sense. I was under the mistaken impression that the 3CX box only arbitrated the connection. That is the case for internal calls but external calls pass through the PBX. I was able to set a minimum bandwidth availability for the 3CX box and call quality is much improved with the network under load.

    Thank you!
     
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  4. Discovery Technology

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    It looks as though there is an "auto voice VLAN" feature on the 3Com switch that you have, so it might at least be a smart move to try locating as many of your phohes as you can onto this switch. The VLAN setup should then "tag" any voice packets with a higher DSCP marking and prioritise it over any data passing through the phone on the same port on the switch.

    Not sure about your Netgear switches though and what their capabilities are.

    It looks as though the Linksys router that you are using has some reasonable low-end QoS features however if you wanted to take full advantage of the VLAN scenario and DSCP markings you might want to consider a Cyberguard SG565 firewall instead - works very well with 3CX.
     
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