3.1. Networking Concepts

💡 First Principle: To configure, secure, and troubleshoot any network, you must understand the fundamental protocols (TCP/UDP), addressing schemes (IP), and name resolution systems (DNS) that govern data transmission.

Scenario: A user reports they can access internal company websites by IP address but not by name. You immediately form a theory that there is a DNS issue. Another user cannot send email (SMTP port 25) but can receive it (POP3 port 110), pointing to a potential outbound firewall block.

Networking is built on a foundation of protocols and standards that define how data is formatted, addressed, and transported. A technician must be fluent in this language to diagnose issues effectively.

⚠️ Common Pitfall: Memorizing port numbers without understanding the purpose of the associated protocol. The exam will test your ability to apply this knowledge to solve a problem, not just recite facts.

Key Trade-Offs:

• Reliability (TCP) vs. Speed (UDP): TCP ensures every packet arrives in order, but this adds overhead. UDP is faster and has less overhead but doesn't guarantee delivery, making it suitable for services like streaming or DNS lookups.

Reflection Question: If a user can't access a website by name (e.g., www.comptia.org) but can by its IP address, what fundamental network service has likely failed, and why?