FYI,
The Grandstream phones work great with SER provided the numeric aliases can be used to reach endpoints. The Grandstream can only dial numeric numbers and not generic sip URI/URLs. It would be great if there was a lookup available underneath the http://www.iptel.org/user/index.php (MyAccount link)->(phone book tab)->(find user link) to find numeric aliases to reach iptel.org users, provided you got the correct non numeric SIP URIs of iptel.org users.
Also, the peering prefix for an iptel.org user to reach and fwd.pulver.com user apears to be in error at http://www.fwd.pulver.com/index.php?section_id=78&PHPSESSID=06a451f4079f..., a prefix of 21111 works great and **393 does not work.
Bye,
Scott Holben
sip iptel.org URIs: skaht AT iptel.org or 90931 AT iptel.org