Network2/Self-test

In order for things to "just work", there are many subgoals that need to be satisfied. The purpose of the self-test algorithm is to speed up debugging by quickly and reliably identifying subgoals whose named requirements are satisfied but whose characteristic test fails.

The form of the self-test algorithm will be a decision-list which may, in the future, be incorporated into software.

A rough outline of that decision list is:

Do we have all the network interfaces that we should?
Is each interface attached to a link?
Does each interface have a link-local address?

Is every interface able to ping itself?
Does link-layer broadcast return responses?
Does network-layer broadcast return responses?

# assuming that we have a partner on the same link
Can we ping our partner?
Can we hear our partner pinging us?
Does there seem to be reasonable bandwidth on our link?

# assuming we have a link-local partner with a name
Do we and our partner have byte-identical names written down?
Can we both resolve the name to a link-local address?
Do we get the same address?
Can we both ping the address?
Can I connect to a service running at the address (e.g. ssh)

# assuming that we have a router
Can we ping our router?
Can we traceroute someone upstream of the router?

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