CS640 Quiz 4 Study Guide

e4-topics.md

<title>e4-topics</title>

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date: 2019-12-09

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Exam 4 Topics

Covers lectures 21 - 25

First Pass

• L21
• L22
• L23
• L24
• L25

Second Pass

• L21
• L22
• L23
• L24
• L25

Fair Queuing (L21)

• Goals
  • Congestion control
  • Good behaviors
  • Isolation across flows
• Solution: Give each flow it’s own queue
  • Round-robin
• Solution: Bit-by-bit round robin
• Solution: Fair Queue
• Solution: Deficit Round Robin (DRR)

Domain Name System (L22)

• Goal: We want to assign human readable names to hosts
• Naming Hosts
  • Processed right to left, with periods as seperators
  • cs.wisc.edu
  • Right most is TLD (Top Level Domain)
    • .com, .gov, .net
• Domain Name Hierarchy
  • Example:

.

.com

.net

.edu

google.com

maps.google.com

scholar.google.com

wisc.edu

cs.wisc.edu

doit.wisc.edu

• Zones
  • ICANN is top level
  • Name servers: very redundant to cover failures
• DNS Records
  • 4 fields
  • name, type, value, TTL
  • name: domain name
  • type
    • A: Value is an IPv4 address
    • AAAA: Value is an IPv6 address
    • NS: Value is domain name for a DNS server that is responsible for the zone containing the DN
    • CNAME: Value is another domain name for a particular host
    • MX: Value is the domain name for a mail server that accepts messages for the DN
  • TTL: Specifies how long another DNS server can cache the record
• Root NS
  • Contains records for all TLD name servers
• Name Resolution
  • Algorithm
    • Start at root and keep asking more specific name servers until you get answer
  • Advanced Name Resolution
    • Can return different sets of records for the same query
    • Used for load balancing or geo-based server selection

HTTP (L23)

• Requests
  • method
    • GET, PUT, DELETE, HEAD
  • “URL”
  • version
  • host
  • options
• Response
  • version
  • status
  • content length
  • MIME
• HTTP and TCP
  • Problems:
    • Too manny RTTs
    • Never enters steady TCP
  • Solution: HTTP 1.1
    • Pipeling and persistent connections
    • 1 tear down at end of session
    • Problem:
      • How do we have TCP SEQNO
      • Solution: Application-level framing
  • HTTP 2.0
    • “SPDY”
    • Adds PUSH

Peer-to-peer Networks

• Use Cases
  • Software update distribution
  • HBO content distribution
  • File sharing
• Questions
  • How do you join the network?
    • Through other peers?
  • How do you discover data or services?