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:
  Integrity
   Hashing (SHA256, MD5, Argon2), MAC, HMAC
   Signing / Digital Signatures: RSA, DSA, ECDSA
  Encryption
   Introduction Symmetric vs Asymetric Key. How safe is 256 bit Key wrt 128, ECC vs Symmetric vs Asymmetric
   Symmetric Key Algos: AES, DES
   Asymmetric Key Algos: DH, RSA, EC(ECDH, secp256k1)
  Build Libraries: Botan, Openssl(build on x86, Cross Compile on ARM)
  iptables
  VPN:
  What
  VPN Tunnel Establishment: IKE(IKEv1, IKEv2), IPSec(Modes(tunnel, transport), Headers(AH, ESP))
  Terms: DPD(Dead Peer Detection), Nonce, PFS(Perfact Forward Secrecy), SA(Security Association), SA, SAD, SPI
  Packet Flow: Inbound, Outbound
  NAT Traversal
Layer-6(Presentation)
  SSL_TLS: TLS, SSL, TLS vs SSL, NSS(TLS Implementation) vs Openssl
  mkcert(Local Self Signed CA(for dev testing))
  Terms: SNI
  Let's Encrypt Get cert signed by Let's Encrypt Root CA
Layer-7(Application)
  Protocols:
  DNS: Introduction(Name resolution, Forward, Reverse lookup, Terms), DNS Records(A, AAAA, Alias, CAA, CNAME, MX, PTR, RR, SOA, SPF, TXT)
  gRPC: Introduction(gRPC, gRPC vs REST), Code(golang gRPC server & client)
  HTTP:
  Introduction: Features, Adv, Disadv, Methods(GET,POST,PUT,DELETE), Headers, Cookies(Session, Domain, Stolen Cookie, Cookie Surrogate)
   HTTP Authentication: How browser gets Session Cookie
   HTTP Connect
  Authentication Procotols: Kerberos, OAuth, OIDC(OpenID Connect), SAML(Authentication procotol using Markup Language)
  MCP(Model Context Protocol)
  REST API
  WebServers: Apache, Ngnix
  Load testing Tools
  RBI(Remote Browser Isolation)