VoIP, P2P and SIP

1. VoIP, P2P and SIP A review of the current VoIP systems Helsinki University of Technology TKK Octavi Miró

2. Summary • Introduction • VoIP • P2P Systems • Skype • SIP • Skype - SIP Similarities and Differences • Conclusion

3. Introduction

4. VoIP • Voice over Internet Protocol. • Two or more people can speak with each other over internet using their computers. • Skype is the first peer-to-peer based IP telephony. • Normally there are three basic functions: • Resource location • Session establishment and management • Presence status

5. P2P Systems • P2P are dynamic, reliable and scalable networks. • Resources are shared between the peers (file-sharing). • Resources can be accessed directly from other peers. • There are different kinds of P2P networks: • Structured • Unstructured • Centralized • Pure • Hybrid

6. P2P Systems - Hybrid P2P • Pro’s • No single point of failure • Can provide anonymity • Reduces the signaling load without reducing the reliability • Con’s • Still signaling traffic • Overlay topology not optimal • Super nodes have to bear a significantly higher load

7. Skype (I) • Most VoIP system used. • Privative. • Architecture: • Host nodes • Super nodes • Login node • Skype uses a central authentication server to authenticate users.

8. Skype (II) LOGIN • A skype client authenticates its username and password with login server. • Advertises its presence to other peers and buddies. • Determines the type of NAT and firewall it is behind. NAT TRANSVERSAL AND FIREWALL • A variation of the STUN and TURN protocols to determine the type of NAT and firewall it is behind.

9. Skype (III) SECURITY • Username and password for authentication. • Uses the Advanced Encryption Standard (AES) for the calls.

10. SIP (I) • The Session Initiation Protocol is a signaling protocol, used for setting up and tearing down multimedia communication sessions. • One of its applications is in VoIP (P2PSIP). • SIP entities • User Agents (Uas) • SIP Proxy • SIP Registar • SIP Redirect Server

11. SIP (II) LOGGING IN • By registration Server. The SIP registration server also stores the IP address and port used to connect to each SIP client. NAT TRANSVERSAL AND FIREWALL • Uses STUN to translate Information inside IP packets for NAT and firewall traversal

12. SIP (III) SECURITY • SIP authenticates by Digest Authentication. • Communication by extension (TLS). Example:

13. SIP - Skype Main Similarities • No differences in the main architecture. • Hybrid P2P. • Supernode in Skype, SIP Proxy and Redirect server in SIP. • Login process is the same in SIP and Skype • Register before direct transmission. • Login Server in Skype and Registar Server in SIP. • Similar NAT and firewall transversal protocol (STUN).

14. SIP-Skype Main Differences • SIP is open and Skype uses a proprietary protocol. • Skype encrypts communications. SIP don’t (just by extension). • SIP just a little part of the whole protocol (more flexible). • SIP is a standard (compatibility and reuse). Skype just an application.

15. Conclusion • SIP and Skype are two different approaches to VoIP communication. • SIP has the strength of flexibility, Skype is easy to install, use and has transparent network access; both offer excellent sound quality. • Nobody knows, whether Skype is a backdoor and really secure. • Skype uses the own “clients” –supernodes- of servers. Less cost more escalability. • SIP-P2P has still work to do for VoIP communications (security, performance…).

16. Questions? Thank you!