I recently switched phone service to xnet and using SPA122 ATA. I am having all sorts of issues getting reliable phone service and xnet tech support have starting pointing the finger at the Motorola cable modem (model SB5101i).  This is quite an old modem now, it was issued to me several years ago. Maybe it is getting long in the tooth and not so good for voice data? Do Telstra supply any alternative modem (or later model) that may provide a better QOS?

The issues I am having are:
1) Lost packets in the upstream data.  eg. a lost syllables every 10 seconds or so.
2) Lost audio in the downstream data eg. blocks of 15 seconds or so of no downstream audio.
3) 'disconnect tone' on some outbound and inbound calls.

I have tried lots of things like DMZ and port forwarding in the Router (D-Link DIR600) and also connecting the ATA direct to modem rather than via the Router. Seems better with direct connection but then internet service really suffered. My router is fairly busy but mostly with internal routing not to internet.

Any advice appreciated.