Protocols
Core protocol concepts for Network+ N10-009
TCP vs UDP
| Feature | TCP | UDP |
|---|---|---|
| Connection | Connection-oriented | Connectionless |
| Reliability | Guaranteed delivery | Best-effort |
| Speed | Slower (handshake) | Faster (no handshake) |
| Order | Ordered packets | No ordering |
| Use cases | HTTP, FTP, SSH, email | DNS, DHCP, VoIP, streaming |
Network+ exam tipTCP uses a 3-way handshake: SYN → SYN-ACK → ACK. Know this for exam questions about connection establishment.
DHCP — DORA Process
- Discover — Client broadcasts to find DHCP server
- Offer — Server offers an IP address
- Request — Client requests the offered IP
- Acknowledge — Server confirms the lease
Ports: 67 (server), 68 (client)
Network+ exam tipDHCP uses UDP, not TCP — it's connectionless because the client has no IP address yet to establish a TCP connection.
DNS — Record Types
| Record | Description |
|---|---|
| A | IPv4 address |
| AAAA | IPv6 address |
| MX | Mail exchange server (with priority) |
| CNAME | Canonical name (alias) |
| PTR | Pointer for reverse DNS (IP → name) |
| TXT | Text records (SPF, DKIM, verification) |
| NS | Name server (delegation) |
| SOA | Start of authority (zone metadata) |
Port: 53 (UDP for queries, TCP for zone transfers)
Network+ exam tipDNS uses UDP for standard queries and TCP for zone transfers (responses > 512 bytes). Know the difference for exam scenarios.
NTP — Stratum Levels
- Stratum 0 — Reference clocks (atomic, GPS) — not directly networked
- Stratum 1 — Servers directly connected to stratum 0 (highest accuracy)
- Stratum 2 — Syncs from stratum 1 servers
- Stratum 3+ — Downstream clients (your server is likely here)
Port: 123 UDP
Network+ exam tipLower stratum = more accurate. Stratum 0 = atomic clock. Your server is likely stratum 3 or 4. Know that NTP uses UDP port 123.
SNMP — Versions
| Version | Authentication | Encryption | Notes |
|---|---|---|---|
| v1 | Community strings | None | Legacy, insecure |
| v2c | Community strings | None | Improved performance, still no encryption |
| v3 | User-based auth | Yes (privacy) | Use in production — only version with encryption |
Ports: 161 (queries), 162 (traps)
Network+ exam tipSNMPv3 is the only version with encryption — always recommend v3 for security. Know ports 161 (queries) and 162 (traps).