Review

Monday, April 27, 2026

Topics

• 13.1 Primary responsibilities of network layer: logical addressing, routing, and packet forwarding
• 13.3 Roles and functions of the control and data planes
• 14.4 Creation and purpose of IP subnets
• 14.5 Network Address Translation (NAT)
• 15.2 Internet Protocol version 6 (IPv6)
• 16.4 Compare Link-State and Distance-Vector Routing
• 17.1 Discuss OSPF and BGP protocols
• 19.1 Primary responsibilities of link layer: framing, addressing, error detection, and media access control (MAC)
• 19.2 Error detection techniques used by the link layer, such as cyclic redundancy check (CRC), to detect transmission errors and ensure data integrity
• 20.2 Link access protocols: TDMA, FDMA, and CDMA

• 20.4 Purpose and function of Address Resolution Protocol (ARP)
• 21.3 Hidden terminal problem in WiFi networks; describe its impact on network performance; evaluate techniques to mitigate this issue
• 23.2 Common network security threats: malware, spoofing, phishing, denial-of-service (DoS) attacks, and man-in-the-middle attacks
• 24.2 Purpose of TLS in securing communications over a network, including its role in providing confidentiality, integrity, and authentication
• 25.1 Purpose and components of IPsec (Internet Protocol Security), including its role in providing authentication, confidentiality, and integrity for IP packets
• 25.3 Identify common security threats associated with wireless networks (e.g., eavesdropping, rogue access points, man-in-the-middle attacks)

Link Layer

• What does it do?
• What kind of addresses?
• How does it detect errors?
• How does it correct errors?
• Can reliable data transfer be achieved at the link layer?

• Framing, addressing, error detection, and media access control (MAC)
• MAC addresses: 48 bits, unique to each network interface card (NIC)
• Error detection: cyclic redundancy check (CRC)
• Error correction: possible with forward error correction (FEC) techniques, but not commonly used in practice
• WiFi uses ACKs and retransmissions;

Network Layer

• What does it do?
• What kind of addresses?
• How does it detect errors?
• How does it correct errors?

• Addressing, routing, and forwarding
• IPv4 errors: checksum only covers header, not payload; no error correction
• IPv6 errors: no checksum at all; relies on upper layers for error detection and correction

IPv6

• Why was it created?
• How large are the addresses?
• Is it more efficient than IPv4?
• Is it more secure than IPv4?

IPv4

• How large are the addresses?
• When will we run out of addresses globally?
• How do we function without enough addresses?

Subnetting

• What is a subnet?
• Why do we use subnets?
• What type of addresses are used in subnets?
• How do we determine the subnet mask?

Network Address Translation (NAT)

• What is it?
• Why do we use it?

Routing

• What does a router do?

1. receive routing information from neighbors
2. build a routing table
3. build a forwarding table
4. forward packets

Routing on the Internet: BGP

• What is an Autonomous System (AS)?
• What does eBGP do?
• What does iBGP do?

• AS: collection of IP networks and routers under the control of one entity that presents a common routing policy to the Internet
• eBGP: exchange routing information between ASes
• iBGP: advertise exit points to other routers within the same AS

Multiple Access Protocols

• TDMA: Time Division Multiple Access
• FDMA: Frequency Division Multiple Access
• CDMA: Code Division Multiple Access

Encryption

• What is symmetric encryption?
• What is asymmetric encryption?
• Which one is faster?
• What is hashing? What would I hash?
• What does hashing have to do with encryption?
• How do I know which key to use for encryption and decryption?

• Symmetric encryption: same key for encryption and decryption; faster; used for bulk data encryption
• Asymmetric encryption: public key for encryption, private key for decryption; slower; used for key exchange and digital signatures
• Hashing: one-way function that maps data of arbitrary size to a fixed-size output; used for data integrity and password storage; not encryption, but often used in conjunction with encryption for authentication and integrity verification
• Hashing uses: data integrity verification, password storage, digital signatures, and authentication codes
• Key management: public key infrastructure (PKI) for asymmetric encryption; secure key exchange protocols (e.g., Diffie-Hellman) for symmetric encryption

HTTPS

• What is HTTPS? How is it related to HTTP and TLS?
• Symmetric or asymmetric encryption?
• How to exchange keys securely to establish a secure connection?

• HTTPS: HTTP over TLS; provides confidentiality, integrity, and authentication for web communications
• Secure connection establishment: TLS handshake, which involves asymmetric encryption for key exchange and authentication, followed by symmetric encryption for data transfer
• Data security: encryption for confidentiality, message authentication codes (MACs) for integrity, and digital certificates for authentication

Common Network Security Threats

• Denial-of-Service
• Replay Attacks
• Man-in-the-Middle
• Phishing
• Cross-Site Scripting (XSS)
• SQL Injection

• How to protect against them?
• DoS: firewalls, rate limiting, DDoS mitigation services
• Replay: encryption + use nonces, timestamps, or sequence numbers to prevent replay attacks
• Man-in-the-Middle: encryption + authentication to prevent interception and tampering
• Phishing: user education, email filtering, multi-factor authentication
• XSS: input validation, Content Security Policy (CSP)
• SQL Injection: input validation, parameterized queries, least privilege database access

Subnetting Practice

Assigned network address space: 10.20.40.0/22

Assign an appropriate address to each subnet.

More Practice Problems

• Network Address Translation (NAT)
• Subnet Addressing
• Dijkstra’s Link-State Algorithm
• Link / Network Layer Addressing and Forwarding

Written Partial Review (WPR)

• 🎯 25 questions; 130 points total; 🕰 75 minutes
• 📄 Scratch paper provided; bring your pen 🖊 and calculator 🖩
• 📑 Show your work for partial credit
• ⛔ Closed book; closed notes; no internet access authorized
• 📜 You may use a single 8.5” x 11” sheet of paper with handwritten notes on both sides
• ⛔ No electronic devices allowed
• ⚠ All work must be your own; no collaboration or discussion with others
• ⚠ Academic Security: Do not discuss the content, structure, or any other information about the WPR with anyone else until the WPR is released from academic security.