Electronic Mail and Instant Messaging

Electronic Mail and Instant Messaging
An Introduction

Prof. David Bernstein
James Madison University

Computer Science Department

bernstdh@jmu.edu

Getting Started

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

The Classic Approach

Electronic Mail Protocols

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

The Classic Server-Based Approach

Instant Messaging

The Classic Peer-to-Peer Approach

Thinking About Messaging

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"