CS 446 Notes 2, 2 Oct 1995
CS 446 Fall Quarter Notes 2 Gio Wiederhold
Experimental Seminar on Large Scale Software Construction.
Admin notes: We will use email a lot for communication.
My email is: Gio@cs. Let me know in the header that's about CS446
The secretary is Marianne Siroker@cs.
Project choices discuss on Wednesday Oct. 3.
Summary from Session 1.. Please tell me what I missed.
Manages development of University Software, also a PhD student of Gio.
University now has a large, complex system covering purchasing, registration email, ..., and everything. Started in 1970 with SPIRES (Stanford Physics Information Systems -- for distribution of physics preprints, designed by Tom W.. This systems was expanded and expanded over 20 years and now is wonderful, but unmaintainable in terms of adding new functions. About 500 employees work in this organization, at $100,000+ per it takes a lot of money.
There are certain cores: General Ledger for finance, a student record, a library catalog, financial investment. The system supports `Workflow' concepts: a DAG (with some cycles) describes process that a transaction goes through. Includes digital signature for validation. System is distributed, and access can come from many places. via an entrypoint: ForsytheTN. Supports RAS (reliability, accessability, security) Ras number includes all accessible time of advertised schedule: RAS number, Forsythe has 99.2% but has 30% scheduled downtime, Leland has 99.7% without scheduled downtime, uses backups to be deal with any single hardware failure. For isnatnce 18 CPUs, and with 300 Gigabyte disk farm, where errors are fixed. Leland is actually 9 machines. There are 800 mountpoints, where directories are mounted when you log on. Uses Andrew file system (AFS), authentication. Directories and files are then cached locally. Increasing use from in-house people. Leland has 19 people.
SPAM's (bad messages which is too widely broadcast) can overload the system. Two security violation attempts per day. Check for system integrity via tripwires and triggers. These enable for instance checking for SPAMs.
Other problem is spoofing: pretending to be another machine or application, unless machine / application has a password as well. The password should be encrypted.
Slowness of response has led to many shadow systems. 1470 feeder systems.now provide data to the old, slow systems. Who is the leader and who is the follower.
"If you have a hard problem you look at it wrong".Alan Kaye
.Sweet Hall has many computers for Stanford student computing. Operates in a distributed environment.
Stanford Administrative Computing to move to DCE (C based, but other languages are feasible, it is an interface language IDL only)
DCE has passwords for application and computers originally defiend by ones PAC (Privilege access lists). Kerberos (5) provides security.
1. do the wire correctly
2. do the infrastructure
3. 22 applications to be done.
General ledger to be purchased from PeopleSoft, and about 6 others, as BuyPay.
Sun, Transarc (Spector), DEC, etc. deliver software all based on DCE.according to OSF standard, derived fromm MITs project Athena. DCE 1.1 just coming out.
Misses still distributed lock management software, other features.
Question: how to deal with shadow systems.
Need elaboration tolerance [McCarthy]
David Dill: perception: Want to buy more, build less.