SDF Voice over Internet Protocol Telephony is a service feature available to the [[http://sdf.org/?join|ARPA]], [[http://sdf.org/?join|META]] and Validated [[http://sdf.org/?join|USERS]] membership levels. It allows an SDF user to make voice and video calls to other SDF users and to linked Telephony services via a SIP client on a 3G or WIFI cellphone, WIFI enabled mobile device, or an Internetworked computer.
Below is a list of known-to-work [[#sip_clients|sip clients]], and [[#general_instructions|general instructions]] on configuring and setting up a SIP client. There may also be [[/?tutorials/sdf_voip_client|client-specific instructions]] as well.
Wikipedia also has a list of notable [[http://en.wikipedia.org/wiki/List_of_SIP_software#SIP_clients|SIP clients]].
All SIP clients must have at least 3 bits of information:
extensionThe "username" used for authentication. Currently, the **extension is a series of numbers** such as "6000". A [[http://sdf.org/?tutorials/sdf_voip_ext|directory]] of users is also available. The assigned extension will be given in an email. Do not use your SDF username.domainThis may also be known as the server to connect with. Use **sip.sdf.org** as the server; use the default port of **5060/udp**. Please note: some clients infer the domain from the extension. In this case, the extension will be in the form of "extension@domain", or "sip:extension@domain"; eg, "6000@sip.sdf.org" would be a valid username that includes the domain.passwordThis is the password used to authenticate to the SIP server. This will be provided in the email as well, but may change very soon in the future. The password can be reset via the maint command.