VOIP Dropped packets, voice disruption?

Recently instaled VOIP System.  Using Allworx server and phones, Cisco switches.  Experiencing problems with voice calls breaking up.  A few other annoying problems.   PINGed phones to detect the lost packets.  REBOOT the phones eliminates the lost packets for an unknown period.  The problem returns for those phones.
jbriley3Asked:
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John MeggersNetwork ArchitectCommented:
What QoS configuration are you running on the switches?  I don't know if Cisco switches will automatically recognize the devices, but if the devices are properly marking packets, the switch can be set to trust those markings.
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jbriley3Author Commented:
Not running QOS on most switches.
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jbriley3Author Commented:
Using  separate VLANs  for data & phone.
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BWaringCommented:
Just because you have separate VLANs set for voice, it doesn't mean that VLAN traffic will get priority. You need to setup QoS to eliminate (minimize) the issues you are experiencing by prioritizing the voice traffic through the switches...
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jbriley3Author Commented:
Testing for lost packets, PING, was done after hours.  No data should have interfered.  Any more ideas?
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BWaringCommented:
OK, I think maybe I didn't understand your original post... when you said "PINGed phones to detect the lost packets", are you actually loosing packets or was that just diagnostic? Your last post didn't specifically say you were loosing packets. If you actually have packet loss, that's most likely not a QoS issue, escpecially if it after hours, no traffic....
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jbriley3Author Commented:
Yes, we discovered toruble with some phones by PINGing.  Booting the phone seems to resolve the PING problem temporarily.  The user experience is voice calls periodically "breaking up" among other lesser issues..
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BWaringCommented:
Is this is separate network for the voice systems? Are there any other devices in the network that your loosing packets to? Test other devices (data devices too if it's a combinded network)....

Is it only certain phones? If it is only certain phones, swap those phones with others that 'work' and see if the problem follows the phone...
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koudryCommented:
Hello,

Having a separate network for VoIP phones and a separate network for data, is a good start. But as pointed above, that is not enough.

Depending on which VoIP phone you are using, you need to be aware of the bandwidth requirement for each phone. This is often dictated by the voice codec of your device. For example, if you have 10 VoIP phones each requiring 32kb of bandwidth for a voice transaction / conversation, you can work out, based on your bandwidth, how many calls can be safely managed at one given time.  This is without bringing data traffic in the equation.

Ok, coming down to QoS ... When QoS is configured to monitor both voice and data together on a platform, it needs to be done properly.

(1) On the CPE end, you need two QoS policies:

Outbound QoS policy: this controls the traffic (voice and data) leaving the customer LAN to the remote end. Here you have full control, i.e. you can allocate bandwidth priority to your voice traffic as you see fit.

Inbound QoS policy: this is the other policy that sits on the CPE device but controls the traffic coming from the core network, i.e. the downstream voice and data traffic. In reality, this policy does not do much apart from collecting stats (I will explain later).

(2) On the core network: in addition to the QoS configuration on the CPE device, you also need another QoS policy on the core network so that your downstream voice and data traffic can be prioritised correctly. Without this QoS policy, the quality of your voice traffic, will suffer.

So I can see two problems:

Bandwidth management in relation to the number of VoIP phone being hosted
QoS, if configured, is not properly implemented - need to check with core network owner that downstream traffic has QoS applied.

Good luck
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