1. Peer-to-peer systems for autonomic VoIP and web hotspot handling Kundan Singh, Weibin Zhao and Henning Schulzrinne Internet Real Time Laboratory Computer Science Dept., Columbia University, New York http://www.cs.columbia.edu/IRT/p2p-sip

2. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 2 P2P for autonomic computing Autonomic at the application layer: –Robust against partial network faults –Resources grow as user population grows –Self-configuring Traditional p2p systems –file storage motivation is often legal, not technical, efficiency –usually unstructured, optimized for Zipf-like popularity Other p2p applications: –Skype demonstrates usefulness for VoIP  identifier lookup NAT traversal: media traversal –OpenDHT (and similar) as emerging common infrastructure? –Non-DHT systems with smaller scope  web hotspot rescue –Network management (see our IRTF slides)

3. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 3 Aside: autonomic characteristics Autonomic characteristics (self-*) determine success for consumer applications: –web-based email programs –consumer IM –Skype –Apple Rendezvous, DHCP IETF and IEEE slowly starting to take note: –old techniques (ICMP) no longer working –netconf: XML-based network configuration instead of CLI and (rarely) SNMP –XCAP: generic XML configuration manipulation –SIP auto-configuration work –IEEE 802.1 network discovery (LLDP, …) –concerns about network complexity

4. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 4 What is SIP? Why P2P-SIP? Bob’s host Alice’s host 128.59.19.194 (1) REGISTER alice@columbia.edu =>128.59.19.194 (2) INVITE alice@columbia.edu (3) Contact: 128.59.19.194 columbia.edu Problem in client-server: maintenance, configuration, controlled infrastructure Peer-to-peer network Alice 128.59.19.194 (1) REGISTER (2) INVITE alice (3) 128.59.19.194 No central server, but more lookup latency

5. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 5 How to combine SIP + P2P? SIP-using-P2P –Replace SIP location service by a P2P protocol P2P-over-SIP –Additionally, implement P2P using SIP messaging P2P network Alice 128.59.19.194 INSERT INVITE sip:alice@128.59.19.194 P2P-SIP overlay Alice 128.59.19.194 REGISTER INVITE alice FIND SIP-using-P2PP2P SIP proxiesP2P-over-SIP MaintenanceP2P SIP LookupP2PSIP

6. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 6 Deployment scenarios P P P P P P2P proxies P P P P P P2P database P P P P P P2P clients Plug and play; May use adaptors; Untrusted peers Zero-conf server farm; Trusted servers and user identities Global, e.g., OpenDHT; Clients or proxies can use; Trusted deployed peers (?) Interoperate among these!

7. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 7 Hybrid architecture Cross register, or Locate during call setup –DNS, or –P2P-SIP hierarchy

8. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 8 What else can be P2P? Rendezvous/signaling (SIP) Configuration storage Media storage (e.g., voice mail) Identity assertion (?) PSTN gateway (?) NAT/media relay (find best one) Trust models are different for different components!

9. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 9 What is our P2P-SIP? 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

10. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 10 Implementation: SIPpeer Platform: Unix (Linux), C++ Modes: –Chord: using SIP for P2P maintenance –OpenDHT: using external P2P data storage Scenarios: –P2P client, P2P proxies –Adaptor for existing phones Cisco, X-lite, Windows Messenger, SIPc –Server farm

11. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 11 Implementation: SIPpeer User interface (buddy list, etc.)SIPICERTP/RTCPCodecsAudio devicesDHT (Chord) On startup DiscoverUser location Multicast REGISTERPeer found/ Detect NAT REGISTER REGISTER, INVITE, MESSAGE Signup, Find buddies Join Find Leave On reset Signout, transfer IM, call SIP-over-P2P P2P-using-SIP

12. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 12 SIP p2p summary and open issues Advantages –Out-of-box experience –Robust catastrophic failure- unlikely –Inherently scalable more with more nodes Status –IETF involvement –Columbia SIPpeer Security issues –Trust, reputation –malicious node, sybil attack –SPAM, DDoS –Privacy, anonymity (?) Other issues –Lookup latency,proximity –P2P-SIP vs SIP-using-P2P –Why should I run as super- node? http://www.cs.columbia.edu/IRT/p2p-sip http://www.p2psip.orghttp://www.p2psip.org and

13. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 13 DotSlash: An Automated Web Hotspot Rescue System Weibin Zhao Henning Schulzrinne Department of Computer Science Columbia University

14. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 14 The Problem Web hotspots –Also known as flash crowds or the Slashdot effect –Short-term dramatic load spikes at web servers Existing mechanisms are not sufficient –Over-provisioning Inefficient for rare events Difficult because the peak load is hard to predict –CDNs Expensive for small web sites that experience the Slashdot effect

15. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 15 The Challenges Automate hotspot handling –Eliminate human intervention to react quickly –Improve availability during critical periods (“15 minutes of fame”) Allocate resources dynamically –Static configuration is insufficient for unexpected dramatic load spikes Address different bottlenecks –Access network, web server, application server, and database server

16. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 16 Our Approach DotSlash –An automated web hotspot rescue system by building an adaptive distributed web server system on the fly Advantages –Self-configuring Service discovery, adaptive control, dynamic virtual hosting –Scalable, easy to use, and transparent to clients

17. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 17 DotSlash Overview Rescue model –Mutual aid community using spare capacity –Potential usage by web hosting companies DotSlash components –Workload monitoring –Rescue server discovery –Load migration (request redirection) –Dynamic virtual hosting –Adaptive rescue and overload control

18. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 18 Handling Load Spikes Request redirection –DNS-RR: reduce arrival rate –HTTP redirect: increase service rate Handle different bottlenecks TechniqueBottleneck Addressed Cache static contentNetwork, web server Replicate scripts dynamicallyApplication server Cache query results on demandDatabase server

19. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 19 Rescue Example Cache static content origin serverrescue server DNS server (1) (2) HTTP redirect (3) reverse proxy (4) (3) (2) DNS round robin client1 client2

20. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 20 Rescue Example (2) Replicate scripts dynamically origin server rescue server PHP MySQL Apache (5) PHP (6) PHP (1) (2) (3) (7) (4) (8) client database server

21. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 21 Rescue Example (3) Cache query results on demand query result cache data driver origin server database server query result cache data driver rescue server database server client

22. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 22 Server States Normal state Rescue state SOS state Allocate rescue serverRelease all rescues Accept SOS requestShutdown all rescues Origin server Get help from others Rescue server Provide help to others

23. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 23 Adaptive Overload Control Objective –CPU/network in desired load region Origin server –Allocate/release rescue servers –Adjust redirect probability Rescue server –Accept SOS requests –Shutdown rescues –Adjust allowed redirect rate

24. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 24 Implementation Based on LAMP (Linux, Apache, MySQL, PHP) Apache module (mod_dots), DotSlash daemon (dotsd), DotSlash rescue protocol (DSRP) Dynamic DNS using BIND with dot-slash.net Service discovery using enhanced SLP BINDmSLP HTTP SHM SLP DNS DSRP other dotsd client Apache dotsd mod_dots

25. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 25 Caching TTL and Hit Ratio (Read-Only)

26. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 26 CPU Utilization (Read-Only)

27. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 27 Evaluation Workload generation –httperf for static content –RUBBoS (bulletin board) for dynamic content Testbed –LAN cluster and WAN (PlanetLab) nodes –Linux Redhat 9.0, Apache 2.0.49, MySQL 4.0.18, PHP 4.3.6 Metrics –Max request rate and max data rate supported

28. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 28 Performance Static content (httperf) –10-fold improvement –Relieve network and web server bottlenecks Dynamic content (RUBBoS) –Completely remove web/application server bottleneck –Relieve database server bottleneck –Overall improvement: 10 times for read-only mix, 5 times for submission mix

29. Dagstuhl Seminar on Autonomic Systems (Jan. 2006) 29 Conclusion DotSlash prototype –Applicable to both static and dynamic content –Promising performance improvement On-going work –Address security issues in deployment –Release DotSlash as open source software For further information –http://www.cs.columbia.edu/IRT/dotslashhttp://www.cs.columbia.edu/IRT/dotslash –DotSlash framework: WCW 2004 –Dynamic script replication: Global Internet 2005 –On-demand query result cache: TR CUCS-035-05 (under submission)