OpenVoIP: An Open Peer-to-Peer VoIP and IM System Salman A. Baset, Gaurav Gupta, and Henning Schulzrinne Computer Science Department, Columbia University http://www1.cs.columbia.edu/~salman/peer/

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OpenVoIP An Open Peer-to-Peer VoIP and IM
System Salman A. Baset, Gaurav Gupta, and
Henning Schulzrinne Computer Science Department,
Columbia Universityhttp//www1.cs.columbia.edu/s
alman/peer/

• Goals
• Build an open peer-to-peer VoIP and IM
  system
• Systematically explore issues in building
  such a system
• Work behind NAT and firewalls
• Relay media sessions through peers, if
  necessary

System Description

• Features
• Scale
• 1000 node Kademlia network
• 300 PlanetLab machines
• DHT-independent protocol
• Google map interface
• Establish calls and IM sessions between peers
  behind network address translators (NATs)
• OpenWengo-P2PP phone

Bootstrap server

• Peer-to-Peer Protocol (P2PP)
• A binary request / response protocol
• Independent of any DHT
• NAT traversal integral design part
• using STUN / TURN / ICE
• Supports
• recursive and iterative queries
• multiple hash functions
• well-known DHTs
• TLS / DTLS
• Interoperable

Peer (super-node) with a public IP address
Client (ordinary node) behind NAT

• Kademlia features
• bucket size5
• consistency
• iterative and recursive routing

• NAT Traversal for VoIP using P2P
• STUN / TURN / ICE

• Why not Skype?
• median network latency between two nodes with a
  ping lt 1 ms
• NAT 95 ms
• blocked 13 ms
• call success rate
• NAT 98
• blocked 73.6
• user annoyance
• closed protocol
• Why not OpenDHT?
• Does not work behind NAT and firewalls
• Tied to one DHT

• Ongoing work
• Relay selection algorithm
• Presence
• Nodes behind less restrictive NAT as super-
  nodes
• Security