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Network protocol

#网络协议37
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This post is translated from Chinese into English through AI.View Original
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This article provides a brief summary of network protocols and their layers, including physical, data link, network, transport, and application layers. It also explains the workflow of HTTPS, including symmetric and asymmetric encryption, the risk of man-in-the-middle attacks, and the use of certificates to ensure security. The article concludes that understanding this process is important for interviews and that SSL/TLS is used in many other areas besides HTTPS.

Preface#

A simple summary of network protocols.

Division of Layers#

Physical Layer: Ethernet, Modems, Power Line Communication (PLC), SONET/SDH, G.709, Optical Fiber, Coaxial Cable, Twisted Pair, etc.
Data Link Layer: Wi-Fi (IEEE 802.11), WiMAX (IEEE 802.16), ATM, DTM, Token Ring, Ethernet, FDDI, Frame Relay, GPRS, EVDO, HSPA, HDLC, PPP, L2TP, PPTP, ISDN, STP, CSMA/CD, etc.
Network Layer Protocols: IP (IPv4, IPv6), ICMP, ICMPv6, IGMP, IS-IS, IPsec, ARP, RARP, RIP, etc.
Transport Layer Protocols: TCP, UDP, TLS, DCCP, SCTP, RSVP, OSPF, etc.
Application Layer Protocols: DHCP, DNS, FTP, Gopher, HTTP, IMAP4, IRC, NNTP, XMPP, POP3, SIP, SMTP, SNMP, SSH, TELNET, RPC, RTCP, RTP, RTSP, SDP, SOAP, GTP, STUN, NTP, SSDP, BGP, etc.

HTTPS Workflow#

  1. Symmetric encryption: Encrypts the data (request, response) for transmission using a symmetric key. The key is generated by the client and needs to be shared with the server.
  2. Asymmetric encryption: The server provides a public key (with a corresponding private key held by the server). The client uses the public key to encrypt the symmetric key, and the ciphertext is transmitted to the server.
  3. Man-in-the-middle attack: Hackers may intercept the public key provided by the server to the client and replace it with their own generated public key, leading to the leakage of the symmetric key.
  4. To address the man-in-the-middle attack, a certificate mechanism is introduced. A third-party certification authority issues a certificate to the website, which includes the public key. The client requests the certificate from the server and verifies it with the certification authority to check its legitimacy.

Conclusion#

The most frequently asked question in interviews about HTTPS is the 4-step process mentioned above. More accurately, this process is a flow of SSL/TLS, which is not only used in HTTPS but also in many other places.

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