Network introduction

Basic definitions

  • Protocol: rules to send and receive, define the format, and order.
  • Network edge/end system: networks used in the house, school, … and devices edge are laptops, smartphones, smart tv, etc.
  • Internet: the network of networks, including many connected computers all over the world.
  • Router: a device used for forwarding packets in the network. The router is used by LAN as well as MAN.
  • Switch: a device is used for gathering many devices locally and connecting the end devices. The switch is used by only LAN.
  • bps: bits per second, a popular unit for measuring network speed.

Store & Forward

Store & Forward is all packets that should be delivered to the router before those are transmitted to next part.

It takes L/R seconds per hop for transmitting an L-bit packet with R bps. So if the latency when a send packet from source to destination with 2 hops takes 2L/R seconds.

End-end delay = 2L/R + D1/c + D2/d caused by spread delay. D1, D2 is the length of the link; c, d is the spread speed.

Alternative core

Equally divided resource for connecting between source and destination:

  • FDM: all connections are parallel and have no queue. Using a channel per connection.

  • TDM: all connection in the queue and no parallel. Resource usage per connection in limit time.

Circuit switching: data is transmitted followed by a router until the end connection

  • Pros: stable, with little latency or loss
  • Cons: more time-consuming connect initialization, performance not high.
  • The maximum number of connections at any one time is the total of connections. In this case, this is 65 circuit.
  • When the connection is full, it will block another connection that wants to join in.

Packet Switching: divide data into the packets application layer:

  • Pros: high performance.
  • Cons: more packets more time-consume, high loss rate.

Reasons cause the delay in network

The delay time is equal to the total of reasons below:

  • Process at node.
  • Queue.
  • Transmit, length.
  • Spread in the environment (~2x10^8 m/s).

Throughput & Bandwidth

Bandwidth: the maximum amount of data transmitted over an internet connection in a given amount of time.

Throughput: transmiting speed (bits/time unit) between source and destination.

OSI Model

Using for simplifying network, easy to understand the relation and maintain, update network.

There are 7 layers in OSI:

  • Layer 7: Application has HTTP, FTP, Telnet, SMTP, DNS.
  • Layer 6: Presentation.
  • Layer 5: Session.
  • Layer 4: Transport has TCP, UDP.
  • Layer 3: Network has IP.
  • Layer 2: Link.
  • Layer 1: Physics.

Application

  • Website.
  • Mobile application.

Presentation

  • Apple Filing Protocol (AFP): Apple Filing Protocol.
  • Lightweight Presentation Protocol (LPP): Lightweight Presentation Protocol.
  • NetWare Core Protocol (NCP): NetWare Core Protocol.
  • Network Data Representation (NDR): Network Data Representation.
  • External Data Representation (XDR): External Data Representation (XDR).
  • Secure Socket Layer (SSL): The Secure Socket Layer (TLS is safer than SSL).

Session

  • AppleTalk Data Stream Protocol (ADSP).
  • Real-time Transport Control Protocol (RTCP).
  • Point-to-Point Tunneling Protocol (PPTP).
  • Password Authentication Protocol (PAP).
  • Remote Procedure Call Protocol (RPCP).
  • Sockets Direct Protocol (SDP): Sockets Direct Protocol (SDP).

Transport

  • TCP/IP is the Transmission Control Protocol (TCP).
  • User Datagram Protocol (UDP).
  • Datagram Congestion Control Protocol (DCCP).
  • Stream Control Transmission Protocol (SCTP).

Network

  • Forwarding.
  • Routing.
  • Virtual circuit network.
  • Datagram network.
  • LLC (logical link control) và MAC (Media Access Control).
  • Switch.

Physics

  • NIC (Network interface card).

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