Reading Response Discussion

Mother of All Demos:

Team: Jason, Kirill, Sravan, Agustin, Hassan Ambalica, Apoorv, Khaled

1968, lead by Doug Inglebard
Initial public display of many modern technologies
One computer with multiple remote terminals
Video conferencing
Computer mouse (and coined the term)
Word processing, rudimentary copy and paste
Dynamic file linking (hypertext)
Revision control/version control/source control
Collaborative real-time editor
- User privilege control in that user can provide read-only access, read-write privilege to file
Corded keyboard
- Marco keyboard that allows messages quickly, while using mouse at same time
Not really a distributed operating system, but great start because multiple users at different terminals could share same resources

Early Internet

Alto

Team: Tory, Veena, Sameer, Mert, Deep, Nameet, Moe

Initially developed around 1973 by Xerox, upgraded over next few years
High speed network connectivity (3 Mbps @ 1km distance)
Connected up to 256 machines
Protocol similar to cross between UDP/TCP, before TCP invented
Allowed sharing of printers
Also allowed distribution of files across computers (redundancy/reliability)
Sort of early cloud
Allowed for remote debugging, store error logs
Allowed machines to use processing power of others
Much of the time it would be idling, which is amazing at a time when computers cost a fortune

Professor lead discussion 1

A true distributed operating system does not actually exist, its more of a dream.

You'll find in the history of trying to achieve this dream of a distributed operating system there has always been a road block as a result of a technical issue. People would come up with a solution to this technical issue but then they would find that some other technical issue would crop up. For example 'The Mother of All Demos' tried to build a distributed operating system but they had no networking. They had to point a television camera at the computer monitor to be able to demo their concept. The early internet came along and dealt with the issue of no networking. However the early internet itself had other technical issues.

A common buzz word during the early days of development was time sharing, which is an old term for multiple processes running simultaneously. However, at the time it referred to multiple users sharing the CPU cycles on a single computer. Today, a single user's many processes using a single CPU is much more common.

Discussion: Easy on one computer, hard on multiple computers

**Instant Messaging**
Why is it easy?	Why is it hard?
Can't be out sync	Synchronization issues Server-client modal If two or more servers they get requests same time, they have to figure out how to synchronize the data Peer-to-Peer Each peer has to figure out how to sync each message
Only one data store/source

**Mortal Kombat/Twitch Gaming**
Why is it easy?	Full control of all software All possible users are physically co-located Latency minimized	Why is it hard?	Games are fundamentally low-latency. Networking is fundamental high-latency. Input prediction doesn't work well on twitchy games. Have to handle lying or faulty clients. Have to handle users finding each other.

**Photo Album**
Why is it easy?	Why is it hard?

Commonalities

Synchronization
Bandwidth
Reliability/Fault Tolerance
Interoperability
Discovery
Routing
- In modern system this issue has been mostly abstracted away
- Classic example would be Wireless Ad-hoc networking

The above list is not hard on a single system because all the cores have equal access to all the resources. Also as a result of excellent engineering modern single systems can very effective deal with any errors that may result.