Why TCP/IP Works Like a Set of Standard Parts – A Deep Dive into Network Protocols

01. High Barrier, Stay Away

Cisco platforms provide a useful Traceback log that records the current module and function when code runs, allowing engineers to pinpoint the exact location of a crash and assign bugs to the responsible team, thus avoiding inter‑departmental blame.

02. Standard Components of Computer Networks

TCP/IP is the "standard part" of computer networking, similar to how cars use standard tires and ESP systems. By reusing these standardized protocols—DNS, TCP, UDP, IP, ICMP, IGMP, ARP, DHCP—developers can build networked applications in minutes instead of months.

03. A Small Example

When a user types zhihu.com into a browser, the first TCP/IP component involved is not TCP as many assume, but DNS, which resolves the domain name to an IP address.

04. Standard Component – DNS

DNS translates the human‑readable domain into an IP address. The query travels through the network stack: Ethernet → ARP (to obtain the destination MAC) → IP → UDP → DNS. Only DNS directly interacts with the browser; all other components are invoked indirectly by DNS.

05. Standard Component – IP

The resolved IP address is written into the packet header and is intended for routers on the Internet, not just the local host. The IP layer also selects the appropriate outbound interface by consulting the routing table, especially on hosts with multiple network adapters.

06. Standard Component – TCP

Before sending an HTTP request, the browser must Create() a TCP control block, which allocates a unique file descriptor (FD). Then it must Connect() using the destination IP and port (80 for HTTP, 443 for HTTPS). This initiates the three‑way handshake (three packets: SYN, SYN‑ACK, ACK). After a successful connection, the browser calls Send() with the FD to transmit the HTTP request. If the target port is 443, TLS must be established first.

07. Standard Component – TLS

TLS operates on top of TCP. Using the same FD, the browser performs a TLS handshake, exchanging certificates and negotiating encryption keys. Once the TLS layer reports success, the encrypted HTTP request is handed down to TCP, then IP, and finally the Ethernet driver for transmission.

08. Standard Component – UDP

Unlike TCP, UDP is connectionless and incurs no handshake overhead, making it ideal for real‑time voice and video where sub‑50 ms latency is required. Data is sent directly through UDP → IP → Ethernet without the reliability mechanisms of TCP.