address the technical issues in heterogeneous networks that may
lack continuous network connectivity.
Architecture:
-Goals
Interoperability across ‘radically heterogeneous’ networks
Tolerate delay and disruption
Acceptable performance in high loss/delay/error environments
Decent performance for low loss/delay/error environments
-Components
Flexible naming scheme
Message abstraction and API
Extensible Store-and-Forward Overlay Routing
Per-(overlay)-hop reliability and authentication
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Emails:
Mail servers and user agents
Simple Mail Transfer Protocol (SMTP)
• Client-server protocol
– Client is the sending mail server
– Server is the receiving mail server
• Reliable data transfer
– Built on top of TCP (on port 25)
• Push protocol
– Sending server pushes the file to the receiving server
– … rather than waiving for the receiver to request it
Retrieving e-mail from a mail server
E-mail message format:
E-Mail Must Tolerate Disruptions:
-Message abstraction
Sending a (potentially large) message
From one user to another user
Okay if there is some delay in delivering the message
-Users may not be online together
Receiver may be offline when the sender sends
Sender may be offline when the receiver receives
Cannot afford to wait until they are both online
-Users may connect from different places
Home, work, airport, hotel room, …
Cannot assume a single IP address, or single host
~cygnosis~
