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Electronic Mail and Instant Messaging
An Introduction


Prof. David Bernstein
James Madison University

Computer Science Department
bernstdh@jmu.edu

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Getting Started
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  • Electronic mail protocols and instant messaging protocols are both application level protocols
  • There are many variants -- we'll consider some pure examples and then some hybrids
Electronic Mail
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The Classic Approach

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Electronic Mail Protocols
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  • SMTP RFC 5321:
    • Transfers message from the sender's server to the receiver's server
  • Access Protocols:
    • POP3 RFC 1939 (provides for authentication and download)
    • IMAP RFC 3501 (adds server-side storage)
Instant Messaging
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The Classic Server-Based Approach

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Instant Messaging
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The Classic Peer-to-Peer Approach

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Thinking About Messaging
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  • An Observation:
    • The differences between electronic mail and instant messaging systems have not been considered systematically
  • What Are The Issues?
    • Synchronous or Asynchronous
    • Full Duplex or Half Duplex
    • Push or Pull
    • Different Roles of the "Server"
There's Always More to Learn
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