1. Introduction to Distributed Systems
Joel crichlow
Distributed Systems: computing over networks, phi learning

2. What is a Distributed System?
A Distributed System is a set of interconnected, autonomous computers that cooperatively solve large, single problems or facilitate parallel execution of separate but possibly related tasks.

3. Distributed System Three key attributes: A network of computers
Computer network
(hidden) network
User’s computer
Three key attributes:
A network of computers
The network is hidden from the user
The system looks the same logically wherever the user is working

4. Cloud Computing
In general Cloud Computing provides access to a pool of computing resources
Distributed System technologies support Cloud Computing
Expect new buzz words in the near future

5. Cloud Computing Recall the progressions
Uniprogramming to multiprogramming
Real memory to virtual memory
Real devices to virtual devices
Real machines to virtual machines
More efficient and cost-effective use of resources
Cloud computing driven largely by the same principles

6. Cloud computing
Sharing Software, Platform, Infrastructure

7. Cloud computing Pay-per-use service alias Pay-as-you-go model
Uses a multi-tenant architecture to deliver several categories of service
Software as a Service (SaaS)
Delivers a single application
Platform as a Service (PaaS)
Delivers development environments
Infrastructure as a Service (Iaas)
Delivers storage, virtual machines, etc

8. Cloud computing Quick development Good scalability Public cloud
Many end-user organizations use services from a common service provider
Private cloud
Services are for a single organization
Hybrid cloud

9. The Computer Network Hosts and Communications Subnet WAN, LAN
IMPs, PSNs
switches, hubs, bridges, gateways, routers
Protocols
Arpanet, Internet
ISO/OSI, TCP/IP

10. Protocols

11. Services Email and Messaging WWW File Transfer Social Networking
DNS, SMTP, TCP/IP
WWW
HTML, HTTP, XML
File Transfer
Telnet, SSH, FTP
Social Networking

12. services
Social networking

13. Services Social Networking
Facebook, Twitter, LinkedIn
Short Message Service (SMS)
Open source software
LAMP web application software stack
Linux, Apache, MySQL and PHP
In-house development
HipHop, Thrift and Cassandra
Memcached: a distributed memory caching system

14. Services
Multimedia Transfer
MPEG, MP3, RTSP
Distributed Computation

15. Services Distributed Transaction Processing network Transaction trans
manager
Replica
network
trans
Data
database

16. Services E-Commerce Request 1 2 3 4 5 payer payee Acquiring
institution
Issuing
Flow of money
network
authorization
Payment order
notification
Request 1 2 3 4 5

17. Services Distributed Real-Time Processing Sensor Dev ice Comp Actuator
Network

18. Issues Naming Sharing Availability and reliability Replication
Globally unique, Domains, Location
Sharing
Authentication, Access rights
Scheduling, Coordinating, Synchronizing
Resolving conflicts
Availability and reliability
Up-time, Responsive, Correct
Replication
Copies made and stored at separate sites
Load sharing, Improved throughput, Improved availability

19. Issues Privacy and Security Communication
Passwords, Access Control Lists, Capabilities
Encryption, Memory Protection
Intrusion blockers
Communication
Protocols aplenty
Concurrency and Synchronization
Race Conditions
Critical Regions
Locks

20. Issues Time and Coordination Fault Tolerance and Recovery
What is the time?
Ordering of events
Fault Tolerance and Recovery
Redundant elements
Logging schemes
Back-ups
Time-outs
Retransmissions

21. Issues Scalability Cannot assume a static configuration
Plan for growth
How about reduction?

22. User-System Interface
The Consumer
Look and Feel
logically similar at all the host computers or front-end machines