1. Client/Server Computing: Clients, Severs, & Operating Systems The Martian C/S (Part 2) PCMag: 7/1/97 NOS PCMag: Beyond Unix

2. Peer-to-Peer Pros: –Simple to set up –Efficient for small groups –Allows resource sharing Cons: –Security is limited –no mechanism for large scale sharing –Inefficient for large groups –Bad for important applications

3. Anatomy of a Server program Role is to serve multiple clients Waits for client-initiated requests Multitasking: many requests at once Priority Queue Background task activities Mission-critical application Scaleable

4. Basic Server requirements of an OS Preemptive Multi-tasking Prioritization of tasks Synchronization (Semaphores) Local/Remote transparent Thread capable Resource protection (Sandbox1) High performance file system Memory managing (Sandbox2) Extendable

5. Extended OS services Ubiquitous communications Flexible access to shared resources Network Management Global dirs & Yellow Pages Authentication services Time, Database, TP monitoring Object Oriented Services Web, DNS, DHCP, etc.

6. Anatomy of a Client C/S systems are client centric Non-GUI clients –ATM, barcode readers, cellphones –daemon programs, testers, agents GUI clients –human interaction –occasional requests –Serial in nature OOUI clients –Non-serial tasks

7. OOUI GUI –application centric –WIMP interface OOUI –object centric –transparent access to applications –seamless OS extension –drag-and-drop interface –stated interface –user friendly

8. Client requirements of an OS RPC mechanism File transfer Task priorities Interprocess communication Threads & multitasking

9. Server Scalability Simple Multiprocessing –Asymmetric(hierarchy) –Symmetric (equality) Multiservers

10. OS comparisons: Clients Client centric DOS & Win 3.x limited potential Win95 ok only (OS/2) 32-bit system required

11. OS comparisons: Servers IntranetWare –Netware File&print server standard NT Server 4.0 –most new development –integration with BackOffice OS/2 Un*x –binary compatibility Microkernels