Читать книгу Understanding Infrastructure Edge Computing - Alex Marcham - Страница 59

Much like the term edge itself, fronthaul, backhaul, and midhaul are all contextual terms. Whether a particular segment of network connectivity fits into any of these three categories depends primarily on the context in which it is observed, specifically by the locations where the network connectivity begins and where it ends combined with the point of view of the person using the terms. Whenever these terms are used, it is worthwhile clarifying the context of the speaker so that the topology that is being described can be fully understood to help to minimise the chance of any resulting confusion.

In the context of infrastructure edge computing, we will use the infrastructure edge data centre as the starting point for our network connectivity when using these terms. This means that when we refer to fronthaul connectivity in this context, it is network connectivity between an infrastructure edge data centre and a piece of network infrastructure such as a telecoms tower or cable headend.

Midhaul in this context refers to the network infrastructure that is used to connect infrastructure edge data centres to one another across an area such as a city. This network is often an example of a MAN, as it connects network endpoints together across an area which is typically the size of a city. Building upon our use of LAN, MAN, and WAN in an earlier section, each infrastructure edge data centre can be considered a LAN in itself, and so the midhaul network infrastructure often does fit our description of a MAN as a network connecting many LANs distributed across a specific area.

Backhaul, when used in the context of infrastructure edge computing, refers to the range of network infrastructure which is used to connect an infrastructure edge data centre back to a piece of regional network or data centre infrastructure. An example of this is a WAN link, which is used to connect one or more infrastructure edge data centres to an IX in a neighbouring city. As such, this connectivity is typically a WAN although, depending on the distance required, it may alternatively be called a MAN.

The way in which we will use these terms throughout this book can be seen in the diagram in Figure 3.4. Terms denoting geographical network scale such as LAN, MAN, and WAN are overlaid as appropriate:

Figure 3.4 Fronthaul, backhaul, and midhaul networks.