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P2P-SIP Peer to peer Internet telephony using SIP

P2P-SIP Peer to peer Internet telephony using SIP. Kundan Singh and Henning Schulzrinne Columbia University, New York June 2005 http://www.cs.columbia.edu/IRT/p2p-sip. Introduction What is P2P? and SIP? Why P2P-SIP? Architecture SIP using P2P vs P2P over SIP; Components that can be P2P

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P2P-SIP Peer to peer Internet telephony using SIP

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  1. P2P-SIPPeer to peer Internet telephony using SIP Kundan Singh and Henning Schulzrinne Columbia University, New York June 2005 http://www.cs.columbia.edu/IRT/p2p-sip

  2. Introduction What is P2P? and SIP? Why P2P-SIP? Architecture SIP using P2P vs P2P over SIP; Components that can be P2P Implementation Choice of P2P (DHT); Node join, leave; message routing Conclusions and future work Overview Total 33 slides

  3. Communication and collaboration Computer systems Magi Groove Skype Centralized Distributed mainframes workstations Peer-to-peer Client-server Napster Gnutella Kazaa Freenet Overnet C C P P Flat Hierarchical Pure Hybrid RPC HTTP DNS mount Gnutella Chord S Napster Groove File sharing Kazaa C C P P SETI@Home folding@Home C P Distributed computing What is P2P? • Share the resources of individual peers • CPU, disk, bandwidth, information, …

  4. Resource aggregation - CPU, disk, … Cost sharing/reduction Improved scalability/reliability Interoperability - heterogeneous peers Increased autonomy at the network edge Anonymity/privacy Dynamic (join, leave), self organizing Ad hoc communication and collaboration Definition fuzzy both client and server? true for proxy no need for central server true for SIP-based media SIP can be e2e proxy functions distributed among end systems P2P goals

  5. Distributed Hash Table (DHT) • Types of search • Central index (Napster) • Distributed index with flooding (Gnutella) • Distributed index with hashing (Chord) • Basic operations find(key), insert(key, value), delete(key), but no search(*)

  6. REGISTER INVITE alice P2P overlay Alice 128.59.19.194 128.59.19.194 No central server, search latency Why P2P-SIP? REGISTER alice@columbia.edu =>128.59.19.194 INVITE alice@columbia.edu Contact: 128.59.19.194 Alice’s host 128.59.19.194 Bob’s host columbia.edu Client-server=> maintenance, configuration, controlled infrastructure

  7. SIP-using-P2P Replace SIP location service by a P2P protocol P2P-over-SIP Additionally, implement P2P using SIP messaging How to combine SIP + P2P? P2P network REGISTER INVITE alice FIND INSERT P2P-SIP overlay Alice 128.59.19.194 INVITE sip:alice@128.59.19.194 Alice 128.59.19.194

  8. SIP-using-P2P • Reuse optimized and well-defined external P2P network • Define P2P location service interface to be used in SIP • Extends to other signaling protocols

  9. P2P-over-SIP • P2P algorithm over SIP without change in semantics • No dependence on external P2P network • Reuse and interoperate with existing components, e.g., voicemail • Built-in NAT/media relays • Message overhead

  10. What else can be P2P? • Rendezvous/signaling • Configuration storage • Media storage • Identity assertion (?) • Gateway (?) • NAT/media relay (find best one)

  11. Our P2P-SIP approach • Unlike server-based SIP architecture • Unlike proprietary Skype architecture • Robust and efficient lookup using DHT • Interoperability • DHT algorithm uses SIP communication • Hybrid architecture • Lookup in SIP+P2P • Unlike file-sharing applications • Data storage, caching, delay, reliability • Disadvantages • Lookup delay and security

  12. 0 1 2 3 4 5 6 7 8 Background: DHT (Chord) • Identifier circle • Keys assigned to successor • Evenly distributed keys and nodes • Finger table: logN • ith finger points to first node that succeeds n by at least 2i-1 • Stabilization for join/leave 1 54 8 58 10 14 47 21 42 38 32 38 24 30

  13. d471f1 1 d467c4 d46a1c 8 d462ba 58 54 d4213f 14 10 47 21 Route(d46a1c) d13da3 42 38 32 65a1fc 38 24 30 Design alternatives servers 1 54 10 38 24 30 clients Use DHT in server farm Use DHT for all clients - but some are resource limited Use DHT among super-nodes Hierarchy Dynamically adapt

  14. Discover DHT (Chord) User location Audio devices User interface (buddy list, etc.) ICE RTP/RTCP Codecs SIP Architecture of prototype Signup, Find buddies IM, call On reset Signout, transfer On startup Leave Find Join REGISTER, INVITE, MESSAGE Peer found/ Detect NAT Multicast REGISTER REGISTER SIP-over-P2P P2P-using-SIP

  15. Naming and authentication • SIP URI as node and user identifiers • Known node: sip:15@192.2.1.3 • Unknown node: sip:17@example.com • User: sip:alice@columbia.edu • User name is chosen randomly by the system, by the user, or as user’s email • Email the randomly generated password • TTL, security

  16. SIP messages 1 • DHT (Chord) maintenance • Query the node at distance 2k with node id 11 REGISTER To: <sip:11@example.invalid> From: <sip:7@128.59.15.56> SIP/2.0 200 OK To: <sip:11@example.invalid> Contact: <sip:15@128.59.15.48>; predecessor=sip:10@128.59.15.55 • Update my neighbor about me REGISTER To: <sip:1@128.59.15.60> Contact: <sip:7@128.59.15.56>; predecessor=sip:1@128.59.15.60 10 22 7 15 Find(11) gives 15

  17. SIP messages • User registration REGISTER To: sip:alice@columbia.edu Contact: sip:alice@128.59.19.194:8094 • Call setup and instant messaging INVITE sip:bob@example.com To: sip:bob@example.com From: sip:alice@columbia.edu

  18. sipd DB Node startup columbia.edu • SIP • REGISTER with SIP registrar • DHT • Discover peers: multicast REGISTER • SLP, bootstrap, host cache • Join DHT using node-key=Hash(ip) • Query its position in DHT • Update its neighbors • Stabilization: repeat periodically • User registers using user-key=Hash(alice@columbia.edu) REGISTER alice@columbia.edu Detect peers REGISTER alice=42 58 42 12 14 REGISTER bob=12 32

  19. Node leaves • Chord reliability • Log(N) successors, replicate keys • Graceful leave • Un-REGISTER • Transfer registrations • Failure • Attached nodes detect and re-REGISTER • New REGISTER goes to new super-nodes • Super-nodes adjust DHT accordingly REGISTER key=42 REGISTER OPTIONS DHT 42 42

  20. 1 30 26 9 19 11 Implementation 31 • sippeer: C++, Unix (Linux), Chord • Node join and form the DHT • Node failure is detected and DHT updated • Registrations transferred on node shutdown 29 31 25 26 15

  21. Adaptor for existing phones • Use P2P-SIP node as an outbound proxy • ICE for NAT/firewall traversal • STUN/TURN server in the node

  22. Hybrid (federated) architecture • Cross register, or • Locate during call setup • DNS, or • P2P-SIP hierarchy

  23. Evaluationscalability • #messages depends on • Keep-alive and finger table refresh rate • Call arrival distribution • User registration refresh interval • Node join, leave, failure rates M={rs+ rf(log(N))2} + c.log(N) + (k/t)log(N) + (log(N))2/N • #nodes = f(capacity,rates) • CPU, memory, bandwidth • Verify by measurement and profiling

  24. Evaluationreliability and call setup latency • User availability depends on • Super-node failure distribution • Node keep-alive and finger refresh rate • User registration refresh rate • Replicate user registration • Measure effect of each • Call setup latency • Same as DHT lookup latency: O(log(N)) • Calls to known locations (“buddies”) is direct • DHT optimization can further reduce latency • User availability and retransmission timers • Measure effect of each

  25. P2P vs. server-based SIP • Prediction: • P2P for smaller & quick setup scenarios • Server-based for corporate and carrier • Need federated system • multiple p2p systems, identified by DNS domain name • with gateway nodes 2000 requests/second ≈7 million registered users

  26. Explosive growth (further study) • Cache replacement at super-nodes • Last seen many days ago • Cap on local disk usage (automatic) • Forcing a node to become super node • Graceful denial of service if overloaded • Switching between flooding, CAN, Chord, … • . . .

  27. More open issues (further study) • Security • Anonymity, encryption • Attack/DOS-resistant, SPAM-resistant • Malicious node • Protecting voicemails from storage nodes • Optimization • Locality, proximity, media routing • Deployment • SIP-P2P vs P2P-SIP, Intra-net, ISP servers • Motivation • Why should I run as super-node?

  28. Comparison of P2P and server-based systems

  29. Catastrophic failure • Server redundancy is well-understood  can handle single-server failures • Catastrophic (system-wide) failure occurs when common element fails • Both server-based and P2P: • all servers crash based on client stimulus (e.g., common parser bug) • Traditional server-based system: • servers share same facility, power, OS, … • P2P system • less likely • share same OS?

  30. d471f1 d467c4 d46a1c d462ba d4213f 763 427 C C P P S 364 123 Route(d46a1c) d13da3 324 C C P P 365 135 564 65a1fc C P Conclusions • P2P useful for VoIP • Scalable, reliable • No configuration • Not as fast as client/server • P2P-SIP • Basic operations easy • Implementation • sippeer: C++, Linux • Interoperates • Some potential issues • Security • Performance http://www.p2psip.org/ http://www.cs.columbia.edu/IRT/p2p-sip

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