The Elements Of A Voice Over Internet Phone

Physical Hardware

• DNS client
• STUN client
• DHCP client (not commonly used)
• Signalling stack (SIP, H.323, Skinny, Skype, or others)
• RTP stack
• Codecs
• Audio
• G.711
• GSM
• iLBC
• Speex
• G.729
• G.722
• G.722.2 (AMR-WB)
• other audio codecs
• Video
• H.263
• H.263+
• H.264
• User interface