QMCS 370 - Class Today

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QMCS 370 - Class Today

• Homework
• Next Homework
• States and HTTP/HTML

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Homework

• Domain Names questions?
• Mail Bagging 6.1
• Headers 6.5
• 6.8, 9, 10
• ... and hand them in!

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Next Homework Next Thursday

• Problem 7.1
• Describes a set of users and applications they
  use
• Identifies some physical locations
• Describes existing IT infrastructure
• a cohesive IT architectural plan
• Identify the servers and clients needed, by
  user/application
• Identify which layers each one has (ref. figure
  7.5)
• Indicate where clients and servers will reside
• Which company offices or facilities
• Is laptop access needed
• For each group of stakeholders, make a list of
  advantages and disadvantages

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The HTTP/HTML State Problem

• Why does a server want to keep track?
• Reserve own images for own pages
• Associate ordered merchandise with one user
• See what a user did to predict what a user wants
• Whats in an HTTP transaction?
• Client side
• Type of request GET, POST usually
• URL of interest
• Contents of a form for POST
• Types of data accepted for GET
• Referrer field
• Cookie field
• Other data expiration, caching, ...
• How do we keep track?

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Statelessness in Servers

• How does the server recognize that a series of
  transactions belong to one user?
• Options
• Simple identifier in transactions (magic path
  names)
• Other protocol headers (Referrer, Cookie)
• Cookies
• Connection identifiers (IP address, for example)
• Something with crypto (maybe a cookie)
• What are cookies anyway?

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What does statelessness mean?

• The server protocol layer doesnt keep track of
  the state
• A separate level of application specific logic
  must keep track of state
• For example cookie ID or transaction ID is
  linked to DB entries
• This is NOT built into the HTTP protocol
  implementation
• In-line linking and statelessness
• The HTTP/HTML technology allows one page to refer
  to content (especially graphics) anywhere on the
  Web
• Some server owners hate this
• There are tricks to prevent such references in
  some cases

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