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Protocols and Ports

Application layer protocols#

They have a link to the transport layer through ports

HTTP#

  • Transfer HTTP documents from a server to a client
  • HTTP can be accessed through port 80, HTTPs through port 443

FTP#

  • Transfer files from a client to a server or vice versa
  • sFTP - Secure
  • TFTP - Trivial
  • FTP, sFTP require authentication, TFTP doesn’t
  • Ports:
    • FTP - 20, 21
    • sFTP - 22, same as SSH
    • TFTP - 69
  • SMB(Server Message Block) - 445, network drive/file share

Email#

  • POP3: Post Office Protocol v3, 110/995
  • IMAP: Internet Message Access Protocol, 143/993
  • POP3 and IMAP both can be used by the client to retrieve the emails from a server/inbox
  • SMTP: Simple Mail Transfer Protocol, 25/465
  • SMTP is used by the client to send an email to an SMTP server which then forwards it to the inbox of the recipient 

LDAP#

  • LightWeight Directory Access Protocol
  • Used for authenticating windows desktop clients in an enterprise network with the Active Directory
  • LDAP: 389, LDAPs: 636

Network Management Protocols#

  • Telnet clear text, 23
  • SSH encrypted, 22
  • SNMP: Simple Network Management Protocol

Audio Visual Protocols#

  • H.323
  • SIP

Network Services#

DHCP#

  • Dynamic Host Configuration Protocol
  • DHCP servers in home networks is usually in the wifi router
  • Whenever any device wants to join the internet, they request the DHCP server to provide them with an IP address, subnet mask, default gateway, DNS server details, etc. and the DHCP server provide these details to the device
  • This helps devices from being statically configured and allows the flexibility to automatically configure these details when moving from one network to another
  • Uses UDP
  • ipconfig

DNS#

  • Domain Name System
  • Uses UDP
  • nslookup