Bundling Spans Temporal Discontinuities Between Networks
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“Persistence of Vision” Provides End-to-End Connectivity
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Bundling is a general-purpose mechanism that allows communication between temporally disconnected nodes.  Imagine this is your network, with the only “permanent” links in yellow.  At some point, there’s a communication opportunity for a portion of the network [CLICK].  This may be a deep-space communications pass or someone walking past a kiosk in an airport, for example.
Now, assuming the delay is low enough, nodes 1 and 2 can communicate using TCP [CLICK]
Eventually, however, that communication session is lost [CLICK]

Later, some other portion of the network becomes connected [CLICK]
Now nodes 2 and 3 can communicate [CLICK]  For a while…[CLICK]
And this continues [CLICK] Nodes 2 and 4 can communicate, [CLICK] nodes 3 and 4 [CLICK]

The essence of the store-and-forward bundling protocol is that it allows communications between nodes for which no contemporaneous end-to-end path ever exists, such as 1 and 4.  You can think of this sort of like the persistence of vision, where first one part of the network is illuminated [CLICK], then another [CLICK], and another [CLICK].  Bundling provides the “memory” that allows us to view these pieces not as disconnected islands, but as a connected whole.  [CLICK]

You might think this is no big deal, SMTP can sort of handle situations like this, but not well.