Add preliminary data section to network check enhancement.

[sanchezl]

Add Preliminary Data section highlighting cases in which the enhancement has provided value.

1. confirmed service endpoints experience long delays in being updated during upgrades because the kube-controller-manager rollout slows down the endpoint update because it takes an outage on local kube-apiserver rollout. We are addressing by switching to the internal LB.
2. confirmed connection timeout from kube-apiserver to openshift-apiserver service during upgrade. reason unknown: https://prow.ci.openshift.org/view/gcs/origin-ci-test/logs/release-openshift-origin-installer-e2e-gcp-upgrade-4.5-stable-to-4.6-ci/1285910416773353472 namespaces/openshift-kube-apiserver/controlplane.operator.openshift.io/podnetworkconnectivitychecks/kube-apiserver-ci-op-v92gtp5p-77d57-ds8mq-master-1-to-openshift-apiserver-service-172-30-23-188-443.yaml at "2020-07-22T13:37:21Z"
3. suspected openstack drops its external loadbalancer for ten seconds
4. confirmed Azure host-network pods cannot reliably contact load balancers, leading to kubelet, sdn, kcm, ks instability
5. confirmed Azure pod-network pods cannot reliably contact load balancers

[sanchezl]

/assign @deads2k

[openshift-bot]

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[russellb]

It would be great to have links that show how the analysis was done and these conclusions were reached. If any of that is in a place you can link to, a follow-up PR would be great. I don't know if CI job artifacts ever get garbage collected, but if they do, I suppose the links you've included will stop working. In any case, this looks like something we should just merge. Sorry it sat so long.

/approve
/lgtm

[openshift-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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[russellb]

/retest

[openshift-bot]

/retest

Please review the full test history for this PR and help us cut down flakes.

[openshift-bot]

/retest

Please review the full test history for this PR and help us cut down flakes.

[openshift-bot]

/retest

Please review the full test history for this PR and help us cut down flakes.

[openshift-bot]

/retest

Please review the full test history for this PR and help us cut down flakes.

[openshift-bot]

/retest

Please review the full test history for this PR and help us cut down flakes.

[openshift-bot]

/retest

Please review the full test history for this PR and help us cut down flakes.

[openshift-bot]

/retest

Please review the full test history for this PR and help us cut down flakes.

[openshift-bot]

/retest

Please review the full test history for this PR and help us cut down flakes.

[russellb]

@sanchezl can you fix the markdownlint issues? Thanks!

[openshift-ci]

@sanchezl: The following test failed, say /retest to rerun all failed tests:

Test name	Commit	Details	Rerun command
ci/prow/markdownlint	e76bbcd	link	/test markdownlint

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[openshift-bot]

Issues go stale after 90d of inactivity.

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/lifecycle stale

[openshift-bot]

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/lifecycle rotten
/remove-lifecycle stale

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/close

[openshift-ci]

@openshift-bot: Closed this PR.

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