1. 1 Group Communication based on Standard Interfaces Matthias Wiesmann ✶, Xavier Défago ✧, André Schiper ✶ ✶ Swiss Federal Institute of Technology at Lausanne Switzerland ✧ Japan Advanced Institute of Science and Technology Japan

2. Group Communication based on Standard Interfaces 2 Group Communication Why standard interfaces? Standardisation goals What interfaces? What standards? Example Overview

3. Group Communication based on Standard Interfaces 3 Transis Handles group as one entity Used for ❑ Replication ❑ Fault-tolerance Strong primitives ❑ Reliable broadcast ❑ Total order broadcast ❑ View synchronous broadcast PhœnixSpread Group communication Horus Ensemble TotemApia Cactus Isis Amœba Java Groups

4. Group Communication based on Standard Interfaces 4 Total Order Broadcast ❑ Delivers a message in the same order everywhere Group communication example

5. Group Communication based on Standard Interfaces 5 Not used much ❑ Isis was commercial product ➫ not success… Many academic prototypes Related system: Message queues ❑ Widely used ❑ Weak properties (not really specified) Group communication current state

6. Group Communication based on Standard Interfaces 6 Complex: ❑ Many different models ❑ Application issues not considered ❑ No standardised interface Group communication problems ➠ need standards

7. Group Communication based on Standard Interfaces 7 Group Communications Why standard interfaces? Standardisation goals What interfaces? What standards? Example Overview

8. Group Communication based on Standard Interfaces 8 From the application's point of view: ❑ Different toolkits ❑ Different interfaces ❑ Different services From the group communicaton point of view: ❑ Each toolkit re-invents the wheel ❑ Cannot use standard low level services ❑ Cannot interoperate with the world Why standard interfaces?

9. Group Communication based on Standard Interfaces 9 Middleware The big picture Route r Administrative Server System Administror Network Administror Infrastructure Server We need interoperability…

10. Group Communication based on Standard Interfaces 10 Group Communications Why standard interfaces? Standardisation goals What interfaces? What standards? Example Overview

11. Group Communication based on Standard Interfaces 11 Things to avoid: ❑ Defining a new standard ❑ Defining a new toolkit ❑ Monolithic system Goals: ❑ Inter-operable system ❑ Reusable services (internally & externally) ❑ Existing & open standards Standardisation goals

12. Group Communication based on Standard Interfaces 12 Want modular system ❑ What granularity? Service approach ❑ Medium granularity ❑ Corresponds to proposals in litterature Failure detection, group membership ❑ Larger than micro-protocols Make it possible to integrate existing systems ❑ Infrastructure (message queues) Modularity

13. Group Communication based on Standard Interfaces 13 Group Communications Why standard interfaces? Standardisation goals What interfaces? What standards? Example Overview

14. Group Communication based on Standard Interfaces 14 Failure detection service Messaging service Multicast service Group Membership service View Synchronous Broadcast Total Order Broadcast What Interfaces? } low level services } high level services

15. Group Communication based on Standard Interfaces 15 Interface overview

16. Group Communication based on Standard Interfaces 16 Group Communications Why standard interfaces? Standardisation goals What interfaces? What standards? Example Overview

17. Group Communication based on Standard Interfaces 17 Desirable standards ❑ Open ❑ Accepted ❑ Appropriate Standard domains: ❑ Messaging ❑ Network management ❑ Directory access What standards to use? Unicast, multicast, total order broadcast Failure detection Group membership Used by existing applications Can be used for group communication

18. Group Communication based on Standard Interfaces 18 Unicast, Multicast ❑ APEX (IETF) ➠ BEEP (IETF) Failure detection ❑ SNMP (IETF) Group Membership ❑ LDAP (IETF) Total order, view synchronous broadcast ❑ APEX (IETF) Applicable standards Simple Network Management Protocol Lightweight Directory Access Protocol Application Exchange Protocol

19. Group Communication based on Standard Interfaces 19 Interfaces – standard overview

20. Group Communication based on Standard Interfaces 20 The big picture Administrative Server System Administror Network Administror Infrastructure Server

21. Group Communication based on Standard Interfaces 21 Group Communications Why standard interfaces? Standardisation goals What interfaces? What standards? Example Overview

22. Group Communication based on Standard Interfaces 22 Service to identify member of a group Exists in one form or another in group communication Set of groups Processes are part of one or more groups Exemple – group membership

23. Group Communication based on Standard Interfaces 23 Groups are name-spaces Processes are leafs Process informations are attributes Group membership – LDAP structure

24. Group Communication based on Standard Interfaces 24 Group membership operations ❑ LDAP queries Find if p1 is member of group a: ❑ search(group=a,pid=1) Find all processes in group b: ❑ search(group=b,pid=*) Add process p3 in group c: ❑ add(group=c,pid=3) Group membership – operations

25. Group Communication based on Standard Interfaces 25 Standards help: ❑ Structure group communication ❑ Reuse existing infrastructure ❑ Permit interaction with existing services & tools Future work: ❑ Show how different services can be implemented ❑ Propose implementations Conclusion

26. Group Communication based on Standard Interfaces 26 Questions? Thank you very much!