Review

Wednesday, February 25, 2026

Topics

  • 2.1 Basic components of a network
  • 2.2 Advantages and disadvantages of different types of network media
  • 2.3 Five-layer TCP/IP model and the principle of encapsulation
  • 3.1 Compare and contrast packet switching and circuit switching
  • 3.2 Four types of delays and their causes
  • 3.3 Concept of throughput; identify the bottleneck
  • 4.2 Common application layer protocols and their purposes
  • 5.1 HTTP protocol; how messages are exchanged
  • 6.1 Functions of DNS; why they are crucial
  • 6.2 DNS server architecture; how it relates to domain names
  • 6.3 DNS vulnerabilities and discuss mitigation strategies
  • 8.2 Key services provided by transport layer - segmentation, multiplexing, flow control, error control
  • 8.3 Connection oriented vs connectionless transport layer protocols - TCP vs UDP
  • 9.2 Key principles and techniques of reliable data transfer
  • 9.4 Compare Selective Repeat and Go-Back-N protocols - window management, retransmission, error recovery
  • 10.3 Three-way handshake mechanism used by TCP to establish a connection
  • 11.1 How TCP handles congestion
  • 11.2 How TCP delivers messages in order vs in a timely manner using sender and receiver buffers

What is a protocol?

Put the five layers of the TCP/IP model in the correct order

  • Link
  • Network
  • Physical
  • Application
  • Transport
  • Frame
  • Bits
  • Segment
  • Datagram
  • Message

Packet switching vs Circuit switching

What protocol layer?

  • DNS
  • TCP
  • HTTP
  • Ethernet
  • IP
  • UDP
  • SMTP

Cookies

  • What are they?
  • Why are they used?
  • What are the risks?

What are the elements of a socket?

What are the four sources of delay in a network?

  • Processing
  • Propagation
  • Queuing
  • Transmission

Delay Calculation

  • Your computer has a 1Gbps connection to your router
  • Router has 0.2 Gbps bandwidth to the neighborhood trunk
  • Trunk has 400 Mbps bandwidth to the central office

Where is the bottleneck?

What is the throughput of the network?

How does a transport layer protocol detect an error in a segment?

A reliable data transfer protocol must handle what potential problems?

  • Loss
  • Corruption
  • Duplication
  • Ordering

How does reliable data transfer handle errors?

Difference between flow control and congestion control?

TCP three-way handshake - what are the three steps?

What happens when a receiver detects a corrupted packet?

  1. Requests retransmission
  2. Drops the packet
  3. Executes error correction
  4. Sends an acknowledgment for the last correctly received packet

When does TCP resend a segment?

  1. When the timer expires
  2. When it receives a NAK
  3. When it receives three duplicate ACKs
  4. Never

What is the purpose of DNS?

  1. To route packets across the internet
  2. To map domain names to IP addresses
  3. To map IP addresses to domain names
  4. To resolve MAC addresses to IP addresses

What types of records are stored in DNS?

What are the three phases of congestion control in TCP?

  • Slow start
  • Congestion avoidance
  • Fast recovery

Timeout Interval Calculation

Suppose the EstimatedRTT is currently \(200\) ms, the DevRTT is \(30\) ms, and the value of α is \(0.125\) and β is 0.25. The most recent SampleRTT is \(240\) ms. What is the new TimeoutInterval?

Delay Calculation

Suppose a packet of 6000 bytes is sent from a computer, passing through two routers before reaching the destination server. Each router has a processing delay of 3 ms. There is no processing delay at the source or destination. The length of each link is as follows:

  • Link 1 (Computer to Router 1): 1200 km
  • Link 2 (Router 1 to Router 2): 800 km
  • Link 3 (Router 2 to Server): 1000 km

Assume no queuing delay and that the propagation speed is \(3 \times 10^8\) m/s.

The bandwidths of the links are:

  • Link 1: 300 Mbps
  • Link 2: 100 Mbps
  • Link 3: 1 Gbps

WPR 1

  • 🎯 25 questions; 100 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.