My setup: IPStar satellite connection using ICONZ as the ISP, right now on their 1Mbps/256Kbps plan. The satellite modem connects to the WAN (Internet) port of a Linksys SPA2102 ATA box. The LAN (Ethernet) port of the SPA2102 connects to a LAN port of a WRT54GL that is in bridge mode and provides a wireless connection for my computers. ICONZ provide me with a /30 subnet so that the satellite modem can have NAT disabled and the SPA2102 WAN port has my public static IP address. The SPA2102 provides NAT and DHCP service out the LAN port.
WXC/VFX unlocked Line 2 of the SPA2102 at my request, allowing me to experiment with settings with another voip provider. I have been using 0064.co.nz for that. I also have been experimenting with an XLite 3.0 softphone on both Windows ans Mac using 0064.co.nz as the provider. VFX is currently not available for use with any softphone and their configuration on the SPA2102 is kept locked, making it impossible for me to experiment with settings for them. I try to see what works well with 0064.co.nz on Line 2 and when I am satisfied that something works better I place a support call to VFX so that the first level tech can pass on my request to an ops person who eventually makes the change and then so far has ignored all my pleas to send me an email so I can know for sure when it has been done :-(
Adding to the challenges is the fact that I have not yet found how to configure Line 2 of the SPA2102 so that it successfully re-registers to 0064 after the first registration after a power cycle expires. That means that every time I want to test making an outgoing call on the box using 0064 I have to reboot it. Many many emails to 0064 support asking for advice on how to configure the SPA2102 have never ever received any reply, not even an automated acknowledgment of receipt the way most support email addresses work. Their website has no phone numbers. Strange how their automated system for sending an email when the pay-as-you-go account balance gets low does work, as does their automated system for accepting a paypal payment into the account. Other than all that 0064 does work well as a way to experiment with configurations of softphones and the SPA2102 for outgoing voip calls using servers in New Zealand, and requires no financial commitment from me other than throwing $10 in the account from time to time.
[update Wed 14-Feb afternoon: I want to put this here right after my criticism to be fair in case Google points people to it. I just got email from 0064.co.nz apologising for a meltdown of their support email server as a result of extreme spam levels and saying that they now have filters and a support ticket system in place. Indeed an email to them resulted in an automated response from a ticketing system with a ticket number and a URL where I can check the status of it.]
My results so far have been strange. On the SPA2102, outgoing voice quality is perfect, but incoming voice is close to unusable because of dropouts and jitter. To get it to be at all usable I found that I had to set the Network Jitter level to Extremely High, which according to documentation causes the jitter buffer to start at 130 msec. I also set the Jitter Buffer Adjust to Up Only. Again according to documentation that should allow the jitter buffer to expand to up to 960 msec if neccessary. I did not find anything that explains when the SPA2102 resets the jitter buffer back to 130msec. I think I get better results using the G729a codec over using G711a or G711u.
Now here is the strange part: Using a softphone like XLite 3.0, which only allows me to use G711a or G711u, gets much better results than the SPA2102, in that there is not the jitter and dropout effects on the incoming voice. I don't know what in the XLite is causing it to work so much better or what can be adjusted in the SPA2102 to get as good results. Suggestions would be welcome.