As Martin is busy with other matters for the time being, I have asked Nokia service to send me some changes to the Nokia VoIP client to enable the CRLF keep-alive packets as described in Chapter 6, ‘NAT/FW traversal settings’, in Nokia S60 VoIP Implementation Configuration Tutorial [2]
Resource information: Nokia S60 VoIP Implementation Configuration Tutorial v1.1 as that appears to be the solution to the problem of calls not getting through to me, as described in point 2.5.1 of the Nokia S60 VoIP Implementation Troubleshooting Guide
http://sw.nokia.com/id/bcbcc0ac-6230...de_v1_0_en.pdf
I have also asked them to send me the changes required to disable all codecs except G.729, in order to save on bandwidth.
Lets see if Nokia can deliver ..........