SIP capabilities:

• Base:
  • INVITE, CANCEL, BYE, REGISTER, OPTIONS, INFO
  • SDP

Transport: UDP, TCP, TLS DNS SRV resolution (RFC 3263) IPv6 (UDP only) Call: hold, unhold transfer/REFER (attended and unattended) (RFC 3515, 3891, 3892) norefersub (RFC 4480) UPDATE (RFC 3311) 100rel/PRACK (RFC 3262) tel: URI (RFC 3966) Session Timer (RFC 4028) SDP: RTCP attribute (RFC 3605) Presence and IM: SUBSCRIBE, NOTIFY PUBLISH (RFC 3903) MESSAGE (RFC 3428) typing indication (RFC 3994) pidf+xml (RFC 3856, 3863) xpidf+xml RPID (subset) (RFC 4480) Other extensions: rport (RFC 3581) AKA, AKA-v2 authentication (RFC 3319, 4169) Service-Route header (RFC 3608) Media capabilities (audio only) (see PJMEDIA):

Base: RTP, RTCP event (RFC 2833) client conferencing, tone generation, file playback/record, etc. Codecs: AMR-NB, AMR-WB, L16, G.711A/U, G.722, G.722.1 16KHz/32KHz (Siren7/Siren14), G.723.1, G.726, G.728, G.729A, iLBC, GSM, Speex 8KHz, 16Khz, 32KHz RTCP XR (RFC 3611) Transports: UDP, STUN, ICE IPv6 (UDP only) SRTP (RFC 3711) and SRTP SDES (RFC 4568)

STUN, TURN, ICE (see PJNATH):

STUN: latest RFC (RFC 5389) DNS SRV resolution short/long term authentication fingerprint TURN: latest draft (RFC-to-be 5766) DNS SRV resolution UDP and TCP client connection ICE: latest draft (RFC-to-be 5245) host, srflx, and relayed candidates aggressive nomination