References

• http://en.wikipedia.org/wiki/Voice_over_IP
• http://en.wikipedia.org/wiki/Public_switched_telephone_network
• http://en.wikipedia.org/wiki/Plain_old_telephone_service
• http://en.wikipedia.org/wiki/Cellular_network
• http://www.packetizer.com/ipmc/h323_vs_sip/
• http://en.wikipedia.org/wiki/Peer-to-peer_SIP
• http://www.img.lx.it.pt/~fp/cav/Additional_material/H261_Recommendation.pdf
• http://www.img.lx.it.pt/~fp/cav/Additional_material/H263_overview_1.pdf
• http://www.img.lx.it.pt/~fp/cav/ano2011_2012/Slides%202012/CAV_6_Videotelephony_2012_Web.pdf