Protocol Numbers 

TCP/IP Ports and Protocols | TCP/IP Ports and Protocols | Pearson IT Certification 

An overview of HTTP - HTTP | MDN 

Firewall 

• Package filtering (IP/TCP layer)

• Session layer Connection tracking 

• Application layer 7

  Deep packet inspection - Wikipedia 

  • Web filtering 
  • Intrusion prevention systems 
  • User identity management 
  • Web application firewall 

Well-known ports