Computer Network Operating Systems

Richard Evans BSEE, MS

Networks

Definition: Computers and other devices connected together for the purpose of data exchange.

Purpose is to share

Data

Devices

Resources (Software & Email)

Why Networks

• Sharing Information– Internet, Corporate Networks, Dept. Nets– Older systems connected as terminals

• Sharing Hardware– Printers, disk space, applications

• Sharing Resources– Email, configuration control, security

Network Communications

• Source

• Message

• Channel

• Receiver

• Noise

• Feedback

• Context

Network Communications

Local Area Network Types

Peer to peer

AppleTalk/internet sharing

Server – based

Novell/ Windows NT

Client server

Commonly used in databases

Types of Networks

Local Area Network

Wide Area Network

                              

1951 MIT's Whirlwind debuted on Edward R. Murrow's "See It Now" television series. Project director Jay Forrester described the computer as a "reliable operating system," running 35 hours a week at 90-percent utility using an electrostatic tube memory.Start of project: 1945 Completed: 1951

Add time: 50 microseconds

Input/output:

cathode ray tube, paper tape, magnetic tape

Memory size: 2048 16-digit words

Memory type: cathode ray tube, magnetic drum, tape (1953 - core memory)

Technology: 4,500 vacuum tubes, 14,800 diodes

Floor space: 3,100 square feet

(Source: "The Computer Museum History Center." "http://www.computerhistory.org." )

“This Internet Timeline begins in 1962, before the word ‘Internet’ is invented. The world’s 10,000 computers are primitive, although they cost hundreds of thousands of dollars. They have only a few thousand words of magnetic core memory, and programming them is far from easy.”

(Source: "The Computer Museum History Center." "http://www.computerhistory.org." )

In 1965 the ARPA-funded JOSS (Johnniac Open Shop System) at the RAND Corporation goes on line. The JOSS system permits online computational problem solving at a number of remote electric typewriter consoles. The standard IBM Model 868 electric typewriters are modified with a small box with indicator lights and activating switches. The user input appears in green, and JOSS responds with the output in black.

                        

(Source: "The Computer Museum History Center." "http://www.computerhistory.org." )

In 1968 the ILLIAC IV, the largest supercomputer of its time, is being built at Burroughs under a NASA contract. More than 1,000 transistors are squeezed onto its RAM chip, manufactured by the Fairchild Semiconductor Corporation, yielding 10 times the speed at one-hundredth the size of equivalent core memory. ILLIAC-IV will be hooked to the ARPANET so that remote scientists can have access to its unique capabilities.

In 1968 Roberts and the ARPA team refine the overall structure and specifications for the ARPANET. They issue an RFQ for the development of the IMPs.

‘Interface Message Processors’ in front of the major computers. Called IMPs, evolve into today’s routers.

After installation in September, handwritten logs from UCLA show the first host-to-host connection, from UCLA to SRI(Stanford Research Institute), is made on October 25, 1969. The first ‘Log-In’ crashes the IMPs, but the next one works!

(Source: "The Computer Museum History Center." "http://www.computerhistory.org." )

In 1971 the ARPANET begins the year with 14 nodes in operation.

Bolt, Beranek and Newman (BBN) modifies and streamlines the IMP design so it can be moved to a less cumbersome platform than the DDP-516. BBN also develops a new platform, called a Terminal Interface Processor (TIP) which is capable of supporting input from multiple hosts or terminals.

(Source: "The Computer Museum History Center." "http://www.computerhistory.org." )

By the beginning of 1981, more than 200 computers in dozens of institutions have been connected in CSNET. BITNET, another startup network, is based on protocols that include file transfer via e-mail rather than by the FTP procedure of the ARPA protocols.

The Internet Working Group of DARPA publishes a plan for the transition of the entire network from the Network Control Protocol to the TCP/IP protocols developed since 1974 and already in wide use (RFC 801).

At Berkeley, Bill Joy incorporates the new TCP/IP suite into the next release of the Unix operating system. The first ‘portable’ computer is launched in the form of the Osborne, a 24-pound suitcase-sized device.

(Source: "The Computer Museum History Center." "http://www.computerhistory.org." )

In 1989 the number of hosts increases from 80,000 in January to 130,000 in July to over

160,000 in November!

Between the beginning of 1986 and the end of 1987 the number of networks grows from 2,000 to nearly 30,000.

By the end of 1985, the number of hosts on the Internet (all TCP/IP interconnected networks) has reached 2,000.

(Source: "The Computer Museum History Center." "http://www.computerhistory.org." )

In 1993 the NSFNET backbone upgrades to T3, or 44 Mbps. Total traffic exceeds 1 trillion bytes, or 10 billion packets per month! Over 100 countries are now connected with over 600,000 hosts and nearly 5,000 separate networks.In 1994 the number of networks exceeds 7,500 and the number of computers connected passes 1,000,000.

(Source: "The Computer Museum History Center." "http://www.computerhistory.org." )

Two years ago when over 1500 Chief Information Officers at US and Canadian companies were asked what information technology skills will be most demanded at the start of last year, here is what they said.

Job Title/Task Demand

Networking 35%

Internet Development 21%

Application development

18%

Help desk 8%

Operations 6%

Project management 6%

Systems Analysis 5%

Other 1%

Internet Growth through 2002

Internet Web Site Growth through 2002

Server-Based Network

Components

File server ( other than peer to peer)

Network operating system

Workstations

Local operating system

Network interface card

Cables / Transmission media

Network Structure

• Datagram structure

• Network topology

• Network access

Datagram

Network / Operating System Dependent

Typical Packet

Sender Address

Destination Address

Packet Length

Data Checksum

Header Data Trailer

Topologies

• Point to Point– Each computer is connected directly to another

location– Configuration difficulties– Very Secure– Very Expensive

Topologies

• Multipoint– Easier to implement– Cheaper– Could be secure if used among similar sites– Most common found today

Types of Multipoint Networks

• Bus• Early Apple Talk

• Must be terminated 50ohm resistor– Without termination reflective inpedence

– No repeator involved

– Connected computer to computer

– Easy to setup / manage

– Number of devices limited

– Troubleshooting dificult

– Slower performance as equipment is added

Topologies

• Ring– IBM / Token ring

• Easier to manage

• Holds more devices wihtout performance issues

• Vendor specific

• Expensive

• Special hardware

Topologies

• Star– Most common

• All computers forward information into a hub

• Hub distributes packets– Hubs can be switching

• Easy to manages / repair

• Single point of failure is hub, not a workstation

• Uses cable, and requires patching

                      

Accessing Network

• How does a computer get information into the pipe?– All computers must follow protocol– Sharing the network pipe is called channel

access method– Method used determines performance of

network

Accessing the Network

• Four methods– Contention

• Fight for priority of network space

• Simultneous access results in errors

• Need rules established– Carrier Sense Multiple Access

» Listen then transmit

– Carrier Sense Multiple Access / Collision Detection

» Listen then transmit / retransmit after allotted time

Accessing the Network

– Polling• Wait until you are asked

• Every computer has equak access

• No monopoly on time

• Unnecessary time delays, waiting for the ok.

• If polling device fails, so does the network

Accessing the Network

– Token Passing• No machine can transmit until it gets the token

• Elliminates collisions

• Equal access

• Expensive

• Slower

Accessing the Network

– Demand Priority• Signal you need the network

• Can establish priorities for certain computers

• Efficient

• Single point of failure

• Expensive

IEEE Standards

– Institute of Electrical and Electronic Engineers• 802.3 CSMA/CD

• 802.5 Token Ring

Preamble(Synchronization)

Destitution Address

Source Address

Type of data format

Novell, Apple, IBM

Data Frame Check Sequence

Standard 802.3 Ethernet frame format

IEEE Standards

• 802.4 Token Bus

• No data collisions

Preamble

(Synchronization)

Start Frame

Frame Control

Destination Address

Source Address

Data Frame Check Sequence

End-Frame Delimiter

IEEE Standards

– IEEE 802.3 10BASE5• Thick Coax, 10 Mbs, 500 Meters

– IEEE 802.3 10BASE2• Thin Coax, 10 Mbs, 200 Meters

– IEEE 802.3 Starlan• Two strands unshielded cable• 1 Mbs, 500 Meters

– IEEE 802.3 10BASET• Twisted pair, 10Mbs, 100Meters