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[communication fundament), Communication fundamental - Coggle Diagram

- - - - doesn't attempt to compensate for various error conditions
    - - transport layer
        
        UDP protocol
        
        simple protocol
        
        connectionless
        
        no guarantee of delivery
        
        TCP protocol
        
        features
        
        connection oriented
        
        establishes connection before any message is exchanged
        
        connection remains open until the TCP client calls close()
        
        once the connection is open the client sends sequence of request as data stream
        
        a data stream is broken into multiple packets
        
        maximum packet size is 65, 535 bytes
        
        stream oriented
        
        TCP has dynamic flow control feature
        
        to ensure a sender doesn't overwhelm a slow receiver
        
        reliable
        
        to ensure reliability tcp uses cumulative acknowledgement mechanism
        
        if sender doesn't receive an acknowledgement with timeout, it re-sends the packet
        
        TCP has checksum feature
        
        emphasis reliability over efficiency
        
        it is more heavyweight protocol
        
        most request on internet uses this
    - - one abstraction is HTTP
  - - - reply client with a referral to a authoritative DNS server
        
        There is an authoritative name server for each top level internet domain e.g .com, .org, .net etc
    - - highly replicated
    - - first point in IP address resolution
      - call authoritative DNS
      - managed by organization or ISPs
      - contact root DNS
      - receive referral to authoritative DNS from root DNS
  - - - port allows a node to support communications for multiple application running on the node
      - each IP supports 65,535 TCP port and 65,535 UDP port
      - on a server the combination {IP , PORT} is associated with an application
      - this combination forms a unique endpoint that transport layer uses to deliver data to desired server
    - - identified by {client ip, client port, server ip, server port}
    - - abstraction over transport layer API
      - support TCP protocol with SOCK_STREAM option
      - supports UDP protocol with SOCK_DGRAM option
  - - - different ways to do
        
        Distributed Computing Environment (DCE)
        
        Common Object Request Broker Architecture (CORBA)
        
        Java Remote Method Invocation (RMI)
        
        XML web services
        
        gRPC
        
        uses HTTP/2 and Protobuf
      - cumbersome to use
      - creates problem when client and server are written in different language
      - application level protocol
    - - most modern systems are build around this
      - uses JSON for parameter representation
      - uses HTTP verb instead of operation name
- - - - 4G
      - 5G
- - - - Nodes can choose to send data to another node any any time
      - The network is half-duplex
        
        meaning one node sends request and must waite for response
        
        these are two separate communication
      - time for data to be communicated between nodes are variable
        
        due to
        
        network congestion
        
        dynamic packet routing
        
        transient network connection failures
      - the receiving node may not be available due to software or machine crash
      - data can be lost, packets can be corrupted.
        
        in wireless network, packet can be dropped due to weak signal
        
        internet routers can drop packets during congestion
      - nodes don't have identical clocks. hence they are not synchronized
  - - - in the rquest add an unique id
      - before processing request, server checks if that id exists in some DB
      - if it doesn't exist, then process request
      - the stored idempotance key can be removed periodically
  - - - fast and unrealiable
        
        UDP
    - - duplicates are inevitable
        
        TCP/IP
    - - no duplicate
        
        slow