1. Caching

2. Andrew Security Andrew Scale and Performance Sprite Performance

3. Andrew File System

4. Sprite

5. Network File System

6. Andrew File System AFS, AFS2, Coda 1983 to present, Satya its champion Ideas spread to other systems, NT

7. Security Terms Release, Modification, Denial of Service Mutual suspicion, Modification, Conservation, Confinement, Initialization Identification, Authentication, Privacy, Nonrepudiation

8. System Components Vice Secure Servers Virtue Protected Workstations Venus Virtual File System Authentication Server

9. Andrew Encryption DES - Private Keys E[msg,key], D[msg,key] Local copy of secret key Exchange of keys doesn’t scale –Web of trust extends to lots of servers –Pair wise keys unwieldy

10. Andrew Authentication Username sent in the clear Random number exchange –E[X,key] sent to server (Vice) –D[E[X,key],key] = X –E[X+1,key] to client (Venus) BIND exchanges session keys

11. Authentication Tokens Description of the user ID, timestamp valid/invalid Used to coordinate what should be available from Vice (server) to Virtue (client)

12. Access Control Hierarchical groups –Project/shared accounts discouraged Positive/Negative Rights U(+) — U(-) VMS linear list & rights IDs Prolog engine in NT Netware has better admin feedback

13. Resource Usage Network not an issue –Distributed DOS ‘hard’ Server High Water Mark –Violations by SU programs tolerated –Daemon processes given ‘stem’ accnt Workstations not an issue –User files in Vice

14. Other Security Issues XOR for session encryption PC support via special server Diskless workstations avoided

15. Enhancements Cells (NT Domains) Kerberos Protection Server for user administration

16. Sprite Components Client Server Local Disk Server Disk Client CacheServer Cache

17. Sprite Design Cache in client and server RAM Kernel file system modification –Affects system/paging and user files Cache size negotiated with VM Delayed 30s write-back –Called ‘laissez-faire’ by Andrew

18. NFS Comparison Presumed optimized RPC access semantics –NFS uses UDP, others TCP Sprite targeting 100+ nodes Andrew targeting 5,000+ nodes

19. Andrew Scale and Performance Dedicated server process per client Directory redirection for content Whole file copy in cache

20. Problems already… Context switching in server TCP connection overhead –Session done by kernel Painful to move parts of VFS to other servers –Volume abstraction fixed this later

21. Cache Management Write on close No concurrent write Versioning User level Delayed write Cache disabled Versioning Kernel level

22. Function Distribution TestAuth - validate cache GetFileStat - file status Fetch - server to client Store - client to server 61.7% 26.8% 4.0% 2.1%

23. Performance Improvements Virtue caches directory Local copy assumed correct File id’s, not names, exchanged Lightweight Processes (LWP) –Context data record on server

24. Andrew Benchmarks

25. Sprite Throughput

26. Sprite Benchmarks

28. Cache Impact - Client

29. Cache Impact - Server

30. Cache Impact - Net

31. Comparison

32. General Considerations 17-20% slower than local Server bottleneck Scan for files and read almost all local 6-8x faster vs no cache Server cache extends local cache Remote paging fast as local disk! 5x users/server

33. Fini