This is my telephone: https://www.gigaset.com/it_it/gigaset-c570-system-it/
 
 
 
I have Fastweb as ISP and these are its voip settings:
 
 
 
3. Requirements and settings related to VoIP service
 
 
 
SIP support (RFC 3261)
 
DNS query support for address resolution of Fastweb SIP network access proxy
 
SIP proxy: voip.fastwebnet.it
 
Proxy SIP Port: 5060
 
SIP Transport Protocol: UDP
 
Support for the PRACK method (RFC 3262)
 
Support OPTIONS method
 
REGISTER expires time: 3600 s
 
INVITE Expires: set to a value greater than 430 s
 
Supported codecs: G.729 G.729A (including version A, versions B and AB NOT supported), G.711 A-law
 
VAD (Voice Activity Detection): disabled
 
Packetization time: 20ms
 
DTMF tone support: in-band telephone-event (RFC 2833)
 
Fax protocol: only T.38
 
 
 
IP traffic QoS marking:
 
      SIP and RTP: DSCP CS5
 
      Data: DSCP 0