1. Distributed Computing Systems
CSCI 4780/6780

2. Threads in Distributed Systems
Attractive as it can support multiple communication channels
Multithreaded Clients
HTML Browser
Threading between display and data transfer
Multiple clients
Multithreaded servers
Two type of threads
Dispatcher and Worker

3. Multithreaded Servers
A multithreaded server organized in a dispatcher/worker model.

4. Design Issues in Servers
Organization
Concurrent – Passing requests to threads/processes
Iterative – Handles the request by itself
Binding
Fixed end point
Client-to-server binding using daemon
Super server
Interrupting the process
Stateless Vs. stateful server

5. Design Issues in Servers
Organization
Concurrent – Passing requests to threads/processes
Iterative – Handles the request by itself
Binding
Fixed end point
Client-to-server binding using daemon
Super server
Interrupting the process
Stateless Vs. stateful server

6. Servers: General Design Issues
3.7
Client-to-server binding using a daemon as in DCE
Client-to-server binding using a superserver as in UNIX

7. General organization of a three-tiered server cluster.
Server Clusters
General organization of a three-tiered server cluster.

8. Switch-based Server Clusters
TCP handoff.

9. Switch and TCP-Handoff
Client TCP connection requests end-up with the switch
Switch determines the best server to handle the request and forwards the request packet to that server
Server sends acknowledgement to the client
Inserts switch’s IP address in the source field of the IP packet header
Requires OS-level modifications
Possible to implement advanced switching mechanisms