Duties, Protocols of Each Layer
Layer-2
  hub router switch bridge, Ping from Host-1 to Host-2
Layer-2.5
  MPLS
Layer-3
  Protocols
   IP
  Security:
   HMAC, MAC, Signing, Integrity
   Build Libraries(Botan, Openssl)
  iptables
Layer-7
  HTTP, REST API, SSL_TLS, WebServer, Kerberos, OAuth, RBI(Remote Browser Isolation)