1. P2P SIP Tutorial Part 2: P2P overlay networks Henry Sinnreich Alan Johnston March 17, 2008

3. Part 1: Overview of SIP and P2P Little time to discuss high complexity

7. Overall carrier wire & wireless IMS architecture - Other IP Networks IP Transport (Access and Core) T - MGF I - BGF UPSF P - CSCF I/S - CSCF BGCF SLF Charging Functions IWF PSTN Emulation (R2) Mw Mw/Mk/Mm Mr Mg Mj Mi Mp Mn Gm Gq ' ISC Cx Dx Dh Sh Ic Rf /Ro Rf /Ro Ib Iw Gq ' PSTN/ISDN MRFC MGCF MRFP e4 Ie Mw IBCF Mk Mk Application Servers Rf /Ro AGCF e2 P1 P2 P3 UE CNG MG IMS / PSTN Simulation Gq ' SPDF A-RACF Resource & Admission Control Resource & Admission Control SPDF Network Attachment Subsystem Re Ia RCEF BGF Ut Ut SGF

8. The complexity of SIP The impact of cable & wireless industries, telephony DB, SBC

9. Solution: Application level overlay network Application Transport Network Data link Physical Application Transport Network Data link Physical Application Transport Network Data link Physical Application layer IP Routing Nothing in the middle Back to the Internet as it was designed: e2e

10. Major P2P Projects Planet Lab infrastructure http://www.planet-lab.org/ 645 nodes over 310 sites. Academic, industrial, and government institutions Open DHT OpenDHT is a publicly accessible distributed hash table (DHT) service . Clients of OpenDHT do not need to run a DHT node in order to use the service. http://www.opendht.org/index.html P2P SIP New IETF WG formed: P2PSIP Several P2P SIP projects and Internet Drafts (P2P IP PBX: Avaya and Peerio, prestandard) http://p2psip.org

16. P2P SIP Protocol Layers Overlay Network Internet SIP applications L4 Transport (UDP, TCP) L3 IP Network Legend DHT: Distributed Hash Table IM: Instant Messaging DHT Layer TCP/IP VoIP, Video Presence IM File Transfer Applications L5

18. CS (a) and P2P (b) SIP Location Discovery Legend SRV: DNS Server Resource Locator (RFC 2782) NAPTR: Network Authority Pointer (RFC 3403) ENUM: E164 Telephone Number Mapping Service (RFC 3764) SIP UA Outbound Proxy SIP UA Inbound Proxy DNS DNS SRV & A queries ENUM: NAPTR, SRV & A queries DB query INVITE INVITE INVITE Caller Called a. Location DB b. Location INVITE 1 2 3 4 5 6 Caller Called API SIP SIP SIP SIP DHT DHT DHT DHT

19. P2P SIP System Legend CN: Client node PN: Peer (various functions) Proxy: SIP proxy server, is another PN Concepts and Terminology for Peer to Peer SIP, < draft-ietf-p2psip-concepts > P2P SIP Peer protocol Client protocol PN PN PN CN CN CN CN CN CN CN CN CN Proxy DNS CS SIP Enrollment Server Bootstrap Server(s) other PSTN PN

23. Part 2: P2P Overlay Networks and Distributed Hash Tables (DHT)

24. Secure Hash Algorithm SHA-1 “it is computationally infeasible 1) to find a message that corresponds to a given message digest, or 2) to find two different messages that produce the same message digest. Any change to a message will, with a very high probability, result in a different message digest.” When a message of any length < 2^64 bits is input, the output is a message digest of 160 bits. Ref: RFC 3174 and http://en.wikipedia.org/wiki/SHA-1 A word equals a 32-bit string which may be represented as a sequence of 8 hex digits. To convert a word to 8 hex digits each 4-bit string is converted to its hex equivalent. Example: 1010 0001 0000 0011 1111 1110 0010 0011 = A103FE23 The SHA1 hash function exhibits good avalanche effect. When a single bit is changed the hash sum becomes totally different

33. Example Deployment Scenarios for P2P SIP There is a large deployment area service providers and IT for stable peers to support big data sets Low Short High Mobile phone, PDA None Client Battery WiFi Phone & GWY Desktop PBX phone BEHAVE compliant Enterprise IAD Residential GWY Phone adapter High Long Low Stable PC Low Short Medium Any Peer Moving Laptop IP Quality Session time Churn Rate NAT Scenario DHT Protocol Critical Operation Deployment Scenario hard easy

34. Performance measurements on the openDHT http://www.arl.wustl.edu/~jst/cse/570/files/10-2-2006a-Andrew_Wan.pdf a. Long running performance and availability of the openDHT for about one year on about 210 nodes b. Latency of ReDirR lookups and openDHT gets

35. Pastry routing from peer 37A0F1 with key B57B2D Live peers B581F1 Route to: B57B2D 1. Match prefix 2. Closest match for same prefix “ A Survey and Comparison or Peer-to-Peer Overlay Network Schemes” by E. K. Lua at al., IEEE Communications Survey, March 2004. B 24EA3 B5 324F B57 3AB 37A0F1 Where is B57B2D ? B57B2D B57 3D6

36. Lookup performance for Pastry “ Pastry: Scalable, decentralized object location and routing” by A. Rowstron and P. Druschel. ACM, Heidelberg, Nov. 2001 b=4, L=16, M=32 for 200,000 lookups (close to log 2 b (N) steps) L=16, 100k random queries, 100k nodes

38. Routing table of Pastry peer with nodeID 37A0x … 37AFx 37AEx 37ADx 37ACx 37ABx … 37A2x 37A1x 37A0x … 37Fx 37Ex … 37Bx 37Ax … 372x 371x 370x … 3Fx 3Ex … 38x 37x … 32x 31x 30x … Fx Ex Dx … 4x 3x 2x 1x 0x IP addresses are not shown “ A Survey and Comparison or Peer-to-Peer Overlay Network Schemes” by E. K. Lua at al., IEEE Communications Survey, March 2004.

39. Routing state of a Pastry peer b=4, L=16, M=32 (IP addresses are not shown) “ A Survey and Comparison or Peer-to-Peer Overlay Network Schemes” by E. K. Lua at al., IEEE Communications Survey, March 2004. 199ABC 28989C 267221 221145 19902D 16228A 122167 11345B 5213EA 510A0C 290A0B 279DE0 490CDE 4881AB 477810 46710A 3912CD 390AF0 37890 3612AB 2670AB 245AD0 1B3467 1A223B Neighborhood set M 37A0FE 37A0FC 37A0FB 37A0FA 37A0F8 37A0F6 37A0F4 37A0F2 Leaf set (larger) 37A077 37A066 37A055 37A044 37A033 37A022 37A011 37A001 Leaf set (smaller) nodeID 37A0F1

40. Pastry: Node addition d46a1c Route(d46a1c)? d46 2ba d4 213f d 13da3 65a1fc d46 7c4 d4 71f1 New node : d46a1c

41. Part 3: High Performance P2P

45. Routing Styles in DHT Routing control at source Is slower Can check routing integrity: better security Higher message traffic at Source Hop by hop routing* Is faster Cannot check routing integrity higher vulnerability Lower message traffic at Source *Routing control is possible through the data interface in ReDiR Source A Root B Iterative routing A B Source Root Recursive routing

50. Performance with smart timeouts Estimating when it is time to route around a failed node “ Handling Churn in a DHT”: http://srhea.net/papers/bamboo-usenix-talk.ppt The best results were obtained with TCP-style timers, by keeping a history of past timeouts and use this to compute timeouts for new requests. This approach works best for recursive lookups where peers are talking only to their neighbors and as a consequence there is only a small and current history to deal with.

51. Smart recovery of neighbor list Reactive recovery is expensive under churn Excessive bandwidth consumption leads to overload and long latencies “ Handling Churn in a DHT”: http://srhea.net/papers/bamboo-usenix-talk.ppt Bandwidth consumption Latency Two 20 minute churn periods of 47 and 23 minute median session times separated by 5 minutes without churn

53. Routing security Model and simulation results for the probability of reaching all correct replica roots using redundant routing. The probability of success is greater than 0.999 for the fraction of faulty nodes <0.3 Ref: “Secure routing for structured peer-to-peer overlay networks” by M. Castro et al. http://www.cs.rice.edu/~dwallach/pub/osdi2002.pdf

59. Questions and discussion