CS 2200. Presentation 21 Networking. Questions?. Our Road Map. Processor. Memory Hierarchy. I/O Subsystem. Parallel Systems. Networking. Overview. Today A Brief History Basic Concepts Network Hardware Ethernet Network Protocols Distributed Systems Remote Procedure Calls (RPC).
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Use continues today
Initially batch oriented environment
Evolution to Timesharing
i.e. Data terminals connected to mainframes
Paved the way for computers to communicate using the telephone switching infrastructure.
Stanford Research Institute, UCLA, UC Santa Barbara, and the University of Utah
Used 130 IC's with a 256 byte memory and 8-bit words, processed 1000 instructions per second, and cost $750.
The Alto consists of four major parts: the graphics display, the keyboard, the graphics mouse, and the disk storage/processor box. Each Alto is housed in a beautifully formed, textured beige metal cabinet that hints at its $32,000 price tag (1979US money). With the exception of the disk storage/processor box, everything is designed to sit on a desk or tabletop
Each machine has the ability to send a message to the other
a.) Please send me the contents of address x
b.) Here is the contents of address x
Thus, messages must contain an extra bit.
Header (1 bit)
Payload (32 bits)
There is an old network saying: Bandwidth problems can be cured with money. Latency problems are harder because the speed of light is fixed--you can’t bribe God.
David Clark, MIT
So far how many computers have we connected?
CSMA/CD allows any node to talk at any time unless two talk at the same time
Efficient at low loads
As the number of hosts increases performance degrades
Token being passed around ring only allows node holding token to talk
Less efficient than Ethernet at low loads
As number of nodes increases performance slows but performance is predictableComparison
A drawing of the first Ethernet system by Bob Metcalfe.
MAU-Medium Access Unit
*Bayonet Neil-Concelman, or
sometimes British Naval Connector