Editing Load-balanced switch (section)

===Single global router===
Since the line cards in a load-balanced switch do not need to be physically near one another, one possible implementation is to use an entire continent- or global-sized backbone network as the interconnection mesh, and core routers as the "line cards".  Such an implementation suffers from having all latencies increased to twice the worst-case transmission latency.  But it has a number of intriguing advantages:

* Large backbone packet networks typically have massive overcapacity (10x or more) to deal with imperfect capacity planning, congestion, and other problems.  A load-balanced switch backbone can deliver 100% throughput with an overcapacity of just 2x, as measured across the whole system.
* The underpinnings of large backbone networks are usually optical channels that cannot be quickly switched.  These map well to the constant-rate 2R/N channels of the load-balanced switch's mesh.
* No route tables need be changed based on global congestion information, because there is no global congestion.
* Rerouting in the case of a node failure does require changing the configuration of the optical channels.  But the reroute can be precomputed (there are only a finite number of nodes that can fail), and the reroute causes no congestion that would then require further route table changes.