Underlay Options
The “underlay” is the transport that carries your traffic between your site and the IZO™+ Multi Cloud Connect network, beneath the cloud connection itself. Three underlays are used - private MPLS, internet, and dedicated Ethernet - and your site enters the network through a Fabric Port whose port type and access type you choose at ordering. The underlay you use is closely tied to the service model: private MPLS with IZO™+ Multi Cloud Connect Direct, internet with IZO™+ Multi Cloud Connect Flex.
What “underlay” means here
Every IZO™+ Multi Cloud Connect service has two layers. The overlay is the cloud connection you are building - the Cloud VC to AWS, Azure, Google Cloud, Oracle or IBM. The underlay is the transport that gets your traffic from your premises into the Tata Communications network so it can reach that Cloud VC. Choosing the underlay is about how your site connects in, not about which cloud you reach.
The three underlays
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Private MPLS - Your site reaches the network over Tata Communications’ private MPLS backbone - a predictable, SLA-backed transport that does not traverse the public internet. This is the underlay for IZO™+ Multi Cloud Connect Direct.
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Internet - Your site reaches the network over an internet connection, with the traffic secured across it. This is the underlay for IZO™+ Multi Cloud Connect Flex, where a VNF (for example an SD-WAN or firewall) typically sits on IZO™+ Multi Cloud Connect. Flex can also be delivered over MPLS where you already have MPLS access.
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Dedicated Ethernet - A dedicated Layer 2 Ethernet pipe reserved to a single customer, used for the dedicated-connection pattern. This underlay is described on Choosing an Underlay & Access Methods.
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Port Type - Hosted Port (a shared port provided by Tata Communications) or Dedicated Port (a physical port reserved exclusively for you).
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Access Type - Public (internet access through the port) or Private (dedicated private connectivity, configurable as Layer 3 or Layer 2).
How your site enters the network
Traffic follows a consistent path: your site --> last mile --> a Tata Communications point of presence (PoP) --> the Tata Communications backbone --> the cloud on-ramp. The last mile is the access circuit from your premises to the nearest PoP; from there the traffic rides the Tata Communications backbone to the point closest to your chosen cloud.
Your entry point into the network is a Fabric Port, and two of its fields set the underlay character:
The Fabric Port also carries the MCC Flavor (Direct or Flex), the location and data centre (the entry point into the network), the bandwidth, and single or dual link for resilience.