[e2e] load balancing

[Noel Chiappa]

    > From: Xai Xi <xaixili at live.com>

    > Do you recall any early attempts to combine traffic load balancing and
    > routing in the same distributed process? Were there any deployments?

The ARPANet did this, in both versions of the routing it ran.

Note that including load in path selection can reduce the stability of the
routing; at worst, there can be feedback loops which cause oscillations, and
other unstable behaviour. The original ARPANet routing was subject to
numerous problems of this sort; see BBN Report 3803, which discusses the
problems in some detail.

Note that the new ARPANet routing didn't completely cure the problem, merely
ameliorated it. That's because the fundamental problem, a feedback loop
between path selection and load, was still there. There are ways to break the
feedback loop and still have path selection dependent on load, but not in a
routing architecture that looks anything like that (e.g. hop-by-hop path
selection).

	Noel