Initial structure for the network operations (#1920)

This commit provides the initial sections for the
network operations content.

content/help/ops/traffic-management/introduction/index.md

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+---
+title: Introduction to Network Operations
+description: An introduction to Istio networking operational aspects.
+weight: 5
+---
+This section is intended as a guide to operators of an Istio based
+deployment.  It will provide information an operator of a Istio deployment
+would need to manage the networking aspects of an Istio service mesh.  Much
+of the information and many of the procedures that an Istio operator
+would require are already documented in other sections of the Istio
+documentation so this section will rely heavily on pointers to that
+other content.
+
+## Key Istio Concepts
+
+When attempting to understand, monitor or troubleshoot the networking within
+an Istio deployment it is critical to understand the fundamental Istio
+concepts starting with the service mesh.  The service mesh is described
+in [Architecture](/docs/concepts/what-is-istio/#architecture).  As noted
+in the architecture section Istio has a distinct control plane and a data
+plane and operationally it will be important to be able to monitor the
+network state of both.  The service mesh is a fully interconnected set of
+proxies that are utilized in both the control and data plane to provide
+the Istio features.
+
+Another key concept to understand is how Istio performs traffic management.
+This is described in [Traffic Management Explained](/docs/concepts/traffic-management).
+Traffic management allows fine grained control with respect to what external
+traffic can enter or exit the mesh and how those requests are routed.  The
+traffic management configuration also dictates how requests between
+microservices within the mesh are handled.  Full details on how to
+configure the traffic management is available
+here: [Traffic Management Configuration](/docs/tasks/traffic-management).
+
+The final concept that is essential for the operator to understand is how
+Istio uses gateways to allow traffic into the mesh or requests originating
+in the mesh from accessing external services. This is described with a
+configuration example here:
+[Istio Gateways](/docs/concepts/traffic-management/#gateways)
+
+## Network Layers Beneath the Mesh
+
+Istio's service mesh runs on top of the networking provided by the
+infrastructure environment (e.g. Kubernetes) on which the Istio mesh
+is deployed.  Istio has certain requirements of this networking layer.
+This guide will not attempt to provide any operational insight to this
+networking layer as many options exist.  In the case of Kubernetes a
+good reference to understand the container networking layer is
+[Kubernetes Cluster Operator](https://kubernetes.io/docs/user-journeys/users/cluster-operator/foundational/).
+Istio has the following requirements of the networking infrastructure
+underneath it:
+
+* The mapping of a service name to workload IP is discoverable by Pilot (this is more a service discovery requirement than a networking requirement)
+
+* The Pilot discovery process can reach the environment specific API server for service discovery.
+
+* Service endpoints have L3 reachability to all endpoints for services in the Istio mesh.
+
+* Any firewall or ACL rules at the infrastructure networking layer don't conflict with any of the Istio layer 3-7 traffic management rules
+
+* Any firewall or ACL rules at the infrastructure networking layer don't conflict with any of the ports used for Istio control traffic

content/help/ops/traffic-management/observing/index.md

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+---
+title: Observing Traffic Management
+description: Describes tools, techniques to observe or issues related to traffic management 
+weight: 5
+---
+
+* Migrate faq section here [FAQ content](/help/faq/traffic-management)
+
+* Provide operational statistics that can be used to observe the traffic management
+
+* Maybe a bunch of pointers to the tasks section would be appropriate

content/help/ops/traffic-management/ops_metrics/index.md

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+---
+title: Network Operational Metrics
+description: Describes tools and techniques that can be used to monitor network perfomance
+weight: 5
+---
+* The goal here is mostly to provide pointers to tools that should be used to ensure the networking aspects are not getting stressed or over-loaded.

content/help/ops/traffic-management/troubleshooting/index.md

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+---
+title: Troubleshooting Networking Issues
+description: Describes tools and techniques that can be used to root cause networking issues
+weight: 5
+---
+
+* Migrate content from old troubleshooting guide here
+
+* Provide a few general procedures that should be followed to isolate
+
+* Describe high level isolation steps and things to check.