Computer Science & Software Engineering

CSCI 466 Networks Fall 2012

MIDTERM INFORMATION

• 50 minutes, during lecture on Friday, November 2nd, 1pm
• Location: HS 001
• No makeups will be considered without an official University excuse
• Closed book, closed notes
• You are allowed a one-sided 8 1/2 x 11 note sheet, hand-written
• No electronic devices except for a calculator

• Computer Networking: A Top-Down Approach, Chapters 1-3
• Review exercises from Chapter 1-3 of book (exercises listed on schedule page)
• Lectures 0-17
• Labs and programming assignments through 10/26

• What's a protocol
• Network edge vs. network core
• Access networks: DSL, cable, fiber to the home, ethernet, WiFi, 3G, satellite
• Calculating transmission delay using packet size and bandwidth
• Physical transmission media: twister pair, coax, fiber, terrestrial radio, satellite, microwave
• Packet switching and store-and-forward
• Routing vs. forwarding
• Circuit switching vs. packet switching
• FDM vs. TDM
• Structure of Internet: access ISPs, regional ISPs, access ISPs, content providers, Internet exchange points
• Network delays: processing, queueing, transmission, propagation
• Causes of packet loss
• Latency, RTT, jitter
• Protocol layers: application, transport, network, link, physical
• OSI model vs. 5-layer model
• How payload is encapsulated by layers
• Network attacks: malware, spyware, (distributed) denial of service, packet sniffing, IP spoofing
• Internet and web history
• Client-server vs. Peer-to-Peer (P2P) architecture
• Socket abstraction for process-to-process communication
• Addressing host endpoint using IP address plus port number
• Desired services: data integrity, timing, throughput, security
• Which desired services do TCP and UDP provide?
• Components of the web: URLs, HTML, HTTP
• HTTP request-response protocol, stateless, TCP on port 80
• Format of HTTP request and response messages
• Common HTTP request methods: GET, POST
• Common HTTP headers: Host, Content-Length, Last-Modified, Set-Cookie, Cookie, If-Modified-Since, ETag, If-No-Match
• Common HTTP response codes: 200, 304, 404
• HTTP non-persistent and persistent connections, pipelining
• HTTP conditional GETs
• Where HTTP caching may occur
• Be able to read and understand Python socket programs
• Format of email, header with name:value pairs and body
• What MIME is, why is it needed, basic content types
• Base64 encoding of non-text data
• HTTP vs. SMTP, pull vs. push protocol
• SMTP, ASCII protocol on TCP port 25
• Why POP3/IMAP are needed in addition to SMTP
• Advantages/disadvantages POP3 vs. IMAP
• FTP, TCP port 20/21, separate control and data connection channels
• SSH, TCP port 22, why better than telnet?
• SSH, connection setup process, use to tunnel insecure traffic
• DNS, UDP on 53, mapping of domain name to IP address
• DNS name resolution process, recursive/iterative queries, resource record
• DNS caching, negative caching, cache poisoning
• Peer-to-Peer (P2P), centralized/pure/hybrid
• Performance advantage of P2P versus client-server
• BitTorrent process, joining torrent, sharing chunks, tit-for-tat
• Distributed Hash Tables (DHT), why they might be useful for P2P
• How a circular DHT works, shortcut links
• What transport layer does, major protocols, TCP vs. UDP
• Multiplexing/demultiplexing key for UDP and TCP
• Advantages of UDP, fields in header, checksum calculation
• Reliable data transport, finite state machine (FSM) notation
• Building blocks of reliable transport: acknowledgements, error detection, sequence numbers, timers
• Stop-and-wait protocol using alternating bit sequence numbers, why its slow
• Pipelined reliable data transport, Go-Back-N and Selective Repeat
• Transmission Control Protocol (TCP), reliable byte stream
• TCP: buffering at sender and receiver, segment header, Maximum Segment Size (MSS)
• TCP: sequence number, ACK number, cumulative ACKs
• TCP: adaptive timeout calculated from sampled RTTs
• TCP: use of receive window field for flow control, window probes
• TCP: Silly Window Syndrome, why it might happen, how to prevent it
• TCP: Overcoming limited size of sequence number and receive window fields
• TCP: Three-way handshake, SYN flooding attack and how to prevent
• Causes of network congestion
• Basic approaches to congestion control, end-to-end versus network-assisted
• Additive increase, multiplicative decrease (AIMD) and why it leads to fairness
• TCP: Sender's use of congestion window
• TCP congestion control: slow-start, congestion avoidance, fast retransmission, fast recovery
• How people can cheat to get around TCP's congestion control, how network might still provide fairness
• TCP splitting: why you might need, how it works

Page last updated: December 26, 2012