Multicomputers Chapter 8 Multiple Processors, A Network, - PDF document

Multicomputers Chapter 8 Multiple Processors, A Network, • Definition: Tightly-coupled CPUs that do not share An OS, and Middleware memory 8.1 Multiprocessors 8.2 Multicomputers • Also known as 8.3 Distributed systems – cluster computers – clusters of workstations (COWs) 1 2 CS 1550, cs.pitt.edu (originaly modified from MOS2 slides by A. Tanenbaum) Multicomputer Hardware (1) Remote Procedure Call (1) • Interconnection topologies • Steps in making a remote procedure call (a) single switch (d) double torus (b) ring – the stubs are shaded gray (e) cube (c) grid (f) hypercube 3 4 CS 1550, cs.pitt.edu (originaly modified from MOS2 slides by A. Tanenbaum) CS 1550, cs.pitt.edu (originaly modified from MOS2 slides by A. Tanenbaum) Remote Procedure Call (2) Distributed Systems (1) Implementation Issues • Cannot pass pointers – call by reference becomes copy-restore (but might fail) • Weakly typed languages – client stub cannot determine size • Not always possible to determine parameter types • Cannot use global variables – may get moved to remote machine Comparison of three kinds of multiple CPU systems CS 1550, cs.pitt.edu (originaly modified from MOS2 slides by A. Tanenbaum) 5 CS 1550, cs.pitt.edu (originaly modified from MOS2 slides by A. Tanenbaum) 6 1

Distributed Systems (2) Network Hardware (1) �✂✁✂✄✆☎✞✝✞✟ ✠✞✡ (a) (b) • Ethernet (a) classic Ethernet Achieving uniformity with middleware (b) switched Ethernet 7 8 CS 1550, cs.pitt.edu (originaly modified from MOS2 slides by A. Tanenbaum) CS 1550, cs.pitt.edu (originaly modified from MOS2 slides by A. Tanenbaum) Network Hardware (2) Network Services and Protocols (1) Network Services The Internet 9 10 CS 1550, cs.pitt.edu (originaly modified from MOS2 slides by A. Tanenbaum) CS 1550, cs.pitt.edu (originaly modified from MOS2 slides by A. Tanenbaum) Network Services and Protocols (2) Document-Based Middleware (1) • Internet Protocol • The Web • Transmission Control Protocol – a big directed graph of documents • Interaction of protocols CS 1550, cs.pitt.edu (originaly modified from MOS2 slides by A. Tanenbaum) 11 CS 1550, cs.pitt.edu (originaly modified from MOS2 slides by A. Tanenbaum) 12 2

Document-Based Middleware (2) File System-Based Middleware (1) How the browser gets a page 1. Asks DNS for IP address 2. DNS replies with IP address 3. Browser makes connection 4. Sends request for specified page 5. Server sends file (b) (a) 6. TCP connection released • Transfer Models 7. Browser displays text (a) upload/download model 8. Browser fetches, displays images (b) remote access model 13 14 CS 1550, cs.pitt.edu (originaly modified from MOS2 slides by A. Tanenbaum) CS 1550, cs.pitt.edu (originaly modified from MOS2 slides by A. Tanenbaum) File System-Based Middleware (2) File System-Based Middleware (3) Location Transparency vs. Location Independence? Naming Transparency • Semantics of File sharing (b) Clients have same view of file system – (a) single processor gives sequential consistency – (b) distributed system may return obsolete value (c) Alternatively, clients with different view 15 16 CS 1550, cs.pitt.edu (originaly modified from MOS2 slides by A. Tanenbaum) CS 1550, cs.pitt.edu (originaly modified from MOS2 slides by A. Tanenbaum) File System-Based Middleware (4) Client's view • AFS – Andrew File System – workstations grouped into cells – note position of venus and vice CS 1550, cs.pitt.edu (originaly modified from MOS2 slides by A. Tanenbaum) 17 3