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When defining infrastructure edge computing in a previous chapter, the term last mile networks was used to denote the dividing line between the locations of the device edge and infrastructure edge to allow us to separate these two very different domains from one another. Last mile networks are key because they represent, for the majority of users and endpoints, the way that they connect to any of the network‐accessible resources that they seek to use. That is why these networks are also referred to as the access layer, when we consider the internet as a network of networks; there must be a first layer of network infrastructure which the endpoint connects to. The connectivity between that first layer then shapes much of the performance and cost that will be achievable in the network overall.

Recalling our discussion in a previous section on network interconnection, we can see that last mile network interconnection is especially critical to fulfil the promises of infrastructure edge computing. Where one endpoint is connected to one network and the endpoint or resource they want to access is connected to another, even if that endpoint is located in a nearby infrastructure edge data centre, if interconnection between these networks must take place a significant distance away in an IX, then the lower latency and cost of data transportation offered by the infrastructure edge data centre will not provide any benefit, as all traffic will move through the IX before it reaches the edge data centre.

The diagram in Figure 3.5 illustrates this challenge. Where access networks are not interconnected at the infrastructure edge, the benefits of the infrastructure edge data centre then cannot be achieved:

A last mile network does not necessarily have to be a publicly accessible LTE network, cable network, or a similar entity; it may be a dedicated fibre connection for a single large entity such as a hospital to provide that entity with direct connectivity to resources which are of significant interest on the infrastructure edge. This network connectivity could be referred to, playing on the terminology used for the cloud on‐ramp services briefly described in a previous section, as an edge on‐ramp of sorts.

Figure 3.5 Last mile or access network interconnection failure.

Infrastructure edge computing does not prescribe a specific type or scale of access network, and the ideal infrastructure edge computing deployment will be able to support multiple concurrent access networks of scales varying from a single intended user through to hundreds of thousands. How each type of access network can interconnect at the infrastructure edge data centre will be explored in a later chapter, but for the purposes of this section, just remember that the more networks the better.