Internet communication The internet A redundant, decentralized - - PowerPoint PPT Presentation

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Internet communication The internet A redundant, decentralized - - PowerPoint PPT Presentation

May 31, 2023 380 likes •466 views

Internet communication The internet A redundant, decentralized communication network connecting computers all over the world Data is sent in packets between machines Communication between computers is routed using the Internet

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SLIDE 1

Internet communication

  • The internet

– A redundant, decentralized communication network connecting computers all over the world – Data is sent in packets between machines – Communication between computers is routed using the Internet Protocol (IP)

  • Every machine gets a unique IP address (e.g. 129.113.132.182)
  • The Domain Name System (DNS) maps readable names to IP

addresses

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SLIDE 2

Internet communication

  • Connections

– The transmission control protocol (TCP) abstracts from packets to connections – A connection between two machines allows back-and- forth communication – Connections are given a port number, so that a single machine can have multiple connections

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SLIDE 3

Client/Server

  • Clients and servers

– Most internet communication is based on a client/server model – The server waits for connections on a certain port – The client initiates a connection to that port

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SLIDE 4

Protocols

  • Protocol

– A set of rules for communication

  • I hold out my hand towards you, vertically
  • You grasp my hand
  • We shake our hands up and down
  • Etc...
  • Secure SHell (SSH)

– Protocol for terminal based communication – Lots of exchanges of cryptographic information – Packets contain encrypted characters

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SLIDE 5

HTTP and URL

  • HyperText Transfer Protocol (HTTP)

– The dominant protocol for internet applications – Used by clients to retrieve resources from servers – Entirely text-based (simple, easy to read) – Stateless

  • Each request/response pair is independent from all others
  • Uniform Resource Locator (URL)

– Format for global specification of resources

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SLIDE 6

HTTP request/response

Server Client

HTTP request http://mirin.cs.panam.edu/~etomai/test.txt

  • Hostname is resolved to IP address (e.g.

129.113.132.218)

  • Request type is GET or POST
  • Request headers give information about the agent
  • (Additional data may be sent)
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SLIDE 7

HTTP request/response

Server Client

HTTP request http://mirin.cs.panam.edu/~etomai/test.txt

  • If the request specifies a static file
  • HTML, image, video, text, etc…
  • The file is retrieved from the server filesystem
  • Response headers specify type of data
  • Using MIME types (e.g. text/html)
  • The file contents are streamed (printed) back to the

client

HTTP response