Computer Network

Updated: 2021-11-19

TCP/IP Model(4 Layers)


  • Application Layer: HTTP, FTP, telnet
  • Transport Layer: TCP, UDP
  • Internet Layer: IP, ICMP
  • Link Layer: device driver

OSI Model(7 Layers)


  • Layer 7: Application Layer: HTTP, FTP
  • Layer 6: Presentation Layer
  • Layer 5: Session Layer: controls the dialogues (connections) between computers.
  • Layer 4: Transport Layer: TCP, UDP
  • Layer 3: Network Layer
  • Layer 2: Data Link Layer
    • Media Access Control (MAC) layer
    • Logical Link Control (LLC) layer
    • Point-to-Point Protocol (PPP)
  • Layer 1: Physical Layer


  • In TCP/IP model, Internet Layer is a subset of OSI model's network layer. It describes only one type of network architecture: the internet.
  • OSI's top 3 layers (application, presentation and session) are not distinguished separately in TCP/IP model.

Important Protocols

A few protocols that a software engineer may care or interact with:

  • L3: IP. IS is connectionless, i.e. a data packet can travel from a sender to a recipient without the recipient having to send an acknowledgement.
  • L4: TCP/UDP
  • L7: HTTP


Anycast addressing uses a one-to-nearest association; datagrams are routed to a single member of a group of potential receivers that are all identified by the same destination address.

what happens: type in browser, use Anycast to find the nameserver(google/godaddy), nameserver lookup your ip in their records, the request is redirected to that ip, your server receives the request, parse the http request, retrieve static html or data from databse, return response, user’s browser receive response, render HTML


Multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource.

Domain Names

FQDN: Fully Qualified Domain Name: sometimes also referred as an absolute domain name is a domain name that specifies its exact location in the tree hierarchy of the Domain Name System(DNS)

TLD: Top Level Domains


iSCSI stands for Internet Small Computer Systems Interface.

An Internet Protocol (IP)-based storage networking standard for linking data storage facilities. The protocol allows admins to better utilize shared storage by allowing hosts to store data to remote networked storage, and virtualizes remote storage for applications that require direct attached storage.