The first test will take place in class on Wednesday, October 3. It will cover course material through Friday, September 28. From the textbook, this includes: Chapter 1, Sections 1.1, 1.2, 1.3, 1.5, and some general ideas from 1.4; Chapter 2, especially Sections 2.1, 2.2, 2.3 2.4, and basic ideas from 2.5; and Chapter 3, Sections 3.1, 3.2, 3.3 and basic ideas from 3.4. You are also responsible for Labs 1 through 4, and for aspects of Java socket programming that were covered in lecture; the Java thread API will not be on the test.
The test will include: some shorter essay-type questions such as definitions; longer, more conceptual essay questions about general network principles; questions about network tools and configuration; and questions about socket programming and the Java Socket API. You might be asked to write some basic Java code with sockets, such as code to contact a server and exchange some data. You might be given some Java code and asked to explain it. The test will be four pages long, with room for answers.
Here are some of the terms and ideas that you should know for the test:
the Internet: a global packet-switched network of networks using the IP protocol packet-switching and packet-switched networks comparison with circuit-switched networks routers (packet-switches between networks) hosts (computers on the network edge) protocol layered protocols and why layered protocols are used encapsulation in protocol layers headers added and used by the different layers IP addresses port numbers throughput and latency sources of delay: processing delay queueing delay transmission delay propagation delay how queuing is used at routers and how it can lead to dropped packets The five layer Internet protocol stack: Application layer (messages) Transport layer (segments) Network layer (datagrams) Link layer (frames) Physical layer (bits) Responsibilities of layers in the Internet protocol stack Transport layer: process-to-process delivery of application-layer messages Network layer: host-to-host delivery of transport layer packets, across multiple networks and routers Link layer: host-to-host delivery within a single local network Physical layer: transmission of bits between directly connected devices application layer: uses transport layer services for process-to-process delivery implements its own architectures, protocols, and policies uses a client/server model on the Internet server "listens" for communications from client at a known IP address and port client sends a connection request to the server HTTP: HyperText Transfer Protocol used for communication between web servers and web clients (browsers) standard port number is 80 a request/response protocol stateless (no state information is automatically preserved between requests) request format: request line, headers, blank line, and (for POST command) data request line example: GET /index.html HTTP/1.1 some request headers: Host:, Connection:, If-Modified-Since:, Cookie: response format: status line, headers, blank line, data status line example: HTTP/1.1 200 OK status codes such as 200 OK, 404 Not Found some response headers: Content-Type:, Content-Length:, Connection:, Set-Cookie: MIME types and why they are used in HTTP persistent connections (Connection: keep-alive vs. Connection: close) Web caching and web proxies SMTP: Simple Mail Transfer Protocol Mail agents and mail servers SMTP used to send mail from mail agent to server and from server to server other protocols (IMAP, POP, webmail) are used to retrieve mail from server traditionally used a plain text conversation on port 25 message headers From:, To:, and Subject: -- part of the mail message SMTP commands MAIL FROM:, RCPT TO: -- part of the "envelope", not the message MIME was introduced to enable binary mail attachments, non-ASCII characters, etc. DNS MX records are used to find the mail server for a email addressm DNS: Domain Name System global, hierarchical, distributed database record types include: A, NS, MX root DNS servers TLD (top-level domain) and TLD servers authoritative name server for a domain local DNS servers DSN queries and answers how a DNS server looks up an IP address caching in DNS and the time-to-live field in DNS database records Peer-to-peer applications why they probably still need a server why they can be faster and more efficient than pure client/server applications multiplexing and demultiplexing in the transport layer TCP (Transmission Control Protocol): connection-oriented, reliable, two-way communication, with congestion control TCP requires connection setup and connection state for each connection UDP (User Datagram Protocol): simple, unreliable process-to-processes delivery UDP checksums and error detection the UDP header: source and destination port numbers, length, checksum UDP does not do congestion control basic ideas for reliable communication: ACK and NAK timeouts and retransmission (to account for packet loss) sequence numbers (to account for duplicate and out-of-order packets) pipelining (to allow multiple packets to be transmitted but not ACKed) Wireshark packet sniffer how Wireshark lets you observe network traffic and packet contents basic network tools: ping, traceroute, nslookup, ifconfig, telnet, netstat socket programming in Java programming basic TCP clients and servers class ServerSocket: constructor: serverSocket = new ServerSocket(port) major method: clientSocket = serverSocket.accept() class Socket: constructor for client side: socket = new Socket(host,port) on sever side, returned by serverSocket.accept(); major methods: socket.getInputStream(), socket.getOutputStream(), socket.close() using socket streams to send and receive messages blocking in serverSocket.accept(), new Socket(), and read operations on Sockets running a server in an infinite loop to handle a sequence of client connections basic ideas of threads and parallel processing why servers are multithreaded thread pools