Chapter 5: Computer Networks and Network Security System¶
Syllabus: ACtE05
Coverage: ACtE0501 through ACtE0506
Status: DRAFT - syllabus and assigned-question pass complete; independent source audit pending
Exam use: Recall, recognition, protocol comparison, subnetting, ports, and security-logic MCQs
Chapter map¶
| Code | Area | Fast recognition cue |
|---|---|---|
ACtE0501 |
Introduction to computer networks and physical layer | Models, devices, standards, media |
ACtE0502 |
Data link layer | Framing, MAC, Ethernet, ARP, PPP, CSMA/CD |
ACtE0503 |
Network layer | IPv4/IPv6, subnetting, routing algorithms and protocols |
ACtE0504 |
Transport layer | TCP vs UDP, ports, sockets, buffering, congestion |
ACtE0505 |
Application layer | HTTP, HTTPS, FTP, mail, DNS, sockets, analyzers |
ACtE0506 |
Network security | Threats, RSA, signatures, PGP, TLS, IPsec, WEP, firewalls |
Chapter rapid-revision sheet¶
| Topic | Must-remember cue |
|---|---|
| OSI vs TCP/IP | 7-layer reference vs deployed Internet stack |
| Device distinction | Hub bits, switch MAC, router IP |
| ARP | IPv4-to-MAC on local LAN |
| 802 families | 802.3 Ethernet, 802.4 Token Bus, 802.5 Token Ring, 802.11 WLAN |
| Routing | RIP distance vector, OSPF link state, BGP inter-domain path vector |
| Subnetting | Usable hosts \(=2^h-2\) |
| Transport | TCP reliable connection-oriented; UDP simple connectionless |
| Ports | HTTP 80, HTTPS 443, FTP 21, SMTP 25, DNS 53, SSH 22 |
| Application tools | PuTTY and WinSCP are tools, not protocols |
| Web security | HTTPS = HTTP over TLS |
| RSA logic | Private key signs, public key verifies |
| WLAN security | WEP obsolete; modern practice uses WPA2/WPA3 |
Assigned-question audit¶
| Target | Deciding fact | Result |
|---|---|---|
set1-025 |
FTP and Telnet are application-layer protocols | Supported by ACtE0501 |
set1-026 |
classic half-duplex Ethernet sends a jam sequence after collision detection | Supported by ACtE0502 |
set1-027 |
IPv4 addresses are 32 bits | Supported by ACtE0503 |
set1-028 |
Packet Tracer is a network simulation and configuration-learning tool | Supported by ACtE0505 |
set1-029 |
IKE authenticates peers and negotiates IPsec SAs and keys | Supported by ACtE0506 |
set1-030 |
sliding-window flow control keeps multiple frames in flight on a large bandwidth-delay path | Supported by ACtE0502 |
set1-077 |
OSI transport provides end-to-end service; TCP supplies reliability, while UDP does not | Best layer answer, with protocol qualification |
set1-078 |
ARP maps a local IPv4 address to a MAC address | Supported by ACtE0502/ACtE0503 |
set1-079 |
link-state routers build a topology map and run a shortest-path algorithm such as Dijkstra | Supported by ACtE0503 |
set1-080 |
WEP was the original 802.11 confidentiality mechanism and is now broken | Supported by ACtE0506 |
Sources and verification note¶
- Coverage authority: NEC syllabus in
syllab.mdforACtE0501throughACtE0506. - Recommended networking verification sources: Kurose and Ross, Computer Networking: A Top-Down Approach; Forouzan, Data Communications and Networking; Tanenbaum and Wetherall, Computer Networks.
- Recommended standards: IETF RFCs for IP, ICMP, TCP, UDP, BGP, IPsec/IKE, and DNS; IEEE 802.3 and 802.11 for Ethernet and WLAN topics.
- Recommended security verification: Stallings, Cryptography and Network Security; NIST guidance for TLS and wireless-security terminology.
- Verification posture: this is a review-dense first edition. Facts are written to be technically correct and exam-useful, but doubtful model-paper keys should be checked against standards instead of copied. WEP is intentionally described as obsolete, and SSL is treated as historical relative to TLS.