Computer Networks & Network Architecture in Operating & Distributed Systems Lecture Notes , Study notes of Operating Systems

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CSCI 3753

Operating Systems

Distributed Systems

Lecture Notes ByShivakant Mishra

Computer Science, CU-Boulder

Last Update: 05/01/

Computer Networks

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Interconnect different computing componentsusing a communication medium.

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A computer network that can support–

widely different applications

: distributed computer

games, air traffic control system, teleconferencing,video-on-demand, medical applications, accounting,banking, and so on.

Widely different components

: PCs, Workstations,

Supercomputers, Laptops, Palmtops, home appliances,and so on.

Widely different software

: Operating systems: Unix,

LINUX, Windows, …

Connecting Computers

Using the Telephone Network

SerialPort

Memory

CPU

SerialPort

Memory

CPU

Switched Telephone Network

Modem

Modem

Local Computer

Remote Computer

Data Networks

NetworkDevice

Memory

CPU

NetworkDevice

Memory

CPU

Specialized Data Network

• Direct connection between every pair of

nodes will make a network very expensive.

Indirect Connectivity

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Nodes forward data received from one link toanother- Forwarding nodes form a

switched network

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Two types of switched networks1.Packet switched network2.Circuit switched network

Indirect Networks

S

R

R

S

Circuit Based

Telephone

R

S

S

R

Packet Based

Data

Cloud

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Distinguishes between nodes that implement anetwork and the nodes that use it.

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Any type of network– single point-to-point link– multiple access link– a switched network

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Router or Gateway: Forwards messages from onenetwork to another.

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Address: Byte string that identifies a node or a setof nodes.-

Typically unique for each node.

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Routing: Process of determining how to forwardmessages towards the destination node based onits address.-

Unicast

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Multicast

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Broadcast

Network Architecture

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Networks must evolve to accommodate changesin both the underlying technologies upon whichthey are based, as well as changes in the demandsplaced on them by applications program.

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Network architecture: Guides the design &implementation of networks.

• Abstraction leads to layering of the system

Application Logical Channels

Host-to-Host Connectivity

Hardware

• Abstract objects that make up the layers of a

network are called

protocols.

• A protocol provides a communication

service that higher level objects can use toexchange messages.

• Protocol
  • Protocol specification- Protocol implementation
    • A protocol may be implemented in many

different ways.

• For peer-to-peer communication to work

correctly, protocol implementations mustimplement the same specification.

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Two or more protocol modules that do accuratelyimplement a protocol specification, are said to interoperate

with each other.

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Protocol stacks must be same at different hosts forapplications to communicate.

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Standardization bodies:-

Establish policies for a particular protocol graph.

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ISO: International Standards Organization

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IETF: Internet Engineering Task Force