Packet Loss


I am running a stock Freepbx 2.11 64-bit Asterisk 11 set up and have absolutely no call quality issues with our suite of Polycom IP501 handsets

I am however pulling my hair out with my Sangoma Vega 50 and 5000 50port analog gateways.

I moved 4 users to the 50-port a few weeks ago and they keep complaining of poor quality, I even witnessed one and it sounded like being on a mobile phone with 1 bar signal.

I investigated the Vega and looked at the QoS reports. I was stunned to find that particular call which only lasted 22 seconds had an 84% packet loss (network side)

Out of 50 calls to these users the majority have 0% loss with a few having less than 1% but there is the odd one here and there that’s above 50% loss

The network is not congested and I basically have the Asterisk PBX on Port 1 on and 8-port switch and Vega in Port 2 of same switch. That’s it. There’s also a fibre off to the Polycom’s but packet loss is still occurring with the fibre briefly disconnected.

I replaced the switch this afternoon and still the same

I see nothing wrong in Asterisk but get this against most calls from the Vega

Peer             Call ID      Duration Recv: Pack  Lost       (     %) Jitter Send: Pack  Lost       (     %) Jitter       0078-04DD-B  00:01:30 0000003013  0000000000 ( 0.00%) 0.0000 0000004509  0000000005 ( 0.11%) 0.0004

So Asterisk is seeing loss on the send packet and looking at the Qos reports on the Vega the errors are on the receive.

Can someone explain what might be going on here?

This is a sample QoS Report

Network side

Codec name                                           G711Alaw
    Packet size                                                30 [ms]
        Silence suppression                                   OFF
        Threshold                                           65466 [dBm]
        Voice playout nominal delay                            60 [ms]
        Voice playout max delay                               120 [ms]
        Echo canceller tail                                    32 [ms]

    No. rx voice packets                                      185 [pkts]
        Dropped/Lost packet rate                            81.47 %
            Bad Packets/Jitter Corrections (Voice Quality)   0.00 %
            Lost due to Network (Network Quality)           81.46 %

Average jitter                                              7 [ms]

    No. tx voice packets                                      735 [pkts]
        Dropped packet rate                                  0.00 %

I’ve just noticed that the packet size is 30ms, should it not be 20ms?


81% packet loss. First clean the floor and get a bigger bit bucket. Once that is done you need to start troubleshooting a few layers down.

I would start with eth-tool and make sure the port is in full duplex, same on the vega. This smells of a duplex mismatch.


That’s the floor sweeped up and I’ve since done a bit of troubleshooting but still none the wiser.

I have taken the managed switch out of the equation and put in a standard non-managed 4 port 100mb switch. The Vega is running 100mb full duplex as is asterisk. I have changed & tested all physical patch leads

As mentioned previously, I have no quality issues what so ever with the polycoms (I have 45 registered at the moment) which is pointing me more towards the Vega rather than asterisk

The freepbx server has 2 NIC’s. em1 is the main link with all IP phones and em2 is for external VPN. The only difference between the two via ethtool that I can see is

em1:     Link partner advertised pause frame use: Symmetric Receive-only
em2:    Link partner advertised pause frame use: No

I’ve searched about but can’t see an explanation as to what this means?

Both NIC’s are 100mb Full duplex

ethtool -S on both NIC’s show no errors

ifconfig on both NIC’s show no errors, overruns, collisions etc

Watching a call on the system to the Vega just now is showing this:

Peer             Call ID      Duration Recv: Pack  Lost       (     %) Jitter Send: Pack  Lost       (     %) Jitter       0078-1BDE-4  00:03:08 0000006265  0000000000 ( 0.00%) 0.0000 0000009391  0000000008 ( 0.09%) 0.0001

0.09% loss on Send.

Any further advice would be greatly appreciated


The jitter is horrific too.

You could have a bad port on the vega.

Can you set the vega to 100 full instead of auto?

Try moving the Vega to the VPN LAN.

You need to isolate until you find the cause. As long as you are dropping packets and they are arriving out of order it’s going to sound awful.