The demise of hub-and-spoke networks

* What is replacing hub-and-spoke network design?

Historically, data networks have been built using some form of a hub-and-spoke design mainly because that design reflected the natural traffic flow. One variant of this design has branch offices connected to regional offices, and has the regional offices connected to a headquarters facility. Another variant has the branch offices connected directly to a headquarters facility.

However, many factors are changing the traffic flow in data networks and hence causing IT organizations to move away from hub-and-spoke network designs. One factor is that branch offices often need access to multiple data centers, either for disaster recovery or for access to applications that are only hosted in one of the company’s data centers. Another is that the vast majority of companies have deployed VoIP and voice traffic does not tend to follow a hub-and-spoke pattern. Voice traffic tends to follow an any-to-any traffic pattern.

As companies move away from a hub-and-spoke network design and adopt either a some-to-many or an any-to-any topology they are increasing the complexity of their network. By the nature of networks that are large and which have complex network topologies, it is not uncommon for the underlying network infrastructure to change, experience instabilities, and to become misconfigured. In addition, the network itself is likely designed in a sub-optimum fashion due to its size and complexity. Any or all of these factors can have a negative impact on application performance. As a result, an organization that has a large complex network needs visibility into the operational architecture and dynamic behavior of the network.

One of the many strengths of IP is its distributed intelligence. For example, routers exchange reachability information with each other via a routing protocol such as OSPF (Open Shortest Path First). Based on this information, each router makes its own decision about how to forward a packet. While this distributed intelligence is a strength of IP, it is also a weakness. In particular, while each router makes its own forwarding decision, there is no single repository of routing information in the network.

Subsequent newsletters will discuss route analytics, a technology that can help IT organizations gain visibility into the operational architecture and dynamic behavior of the network. Route analytics is one of the topics that will be discussed at Network World’s IT Roadmap conference that will be held in Boston on March 6. If you live in the area, hopefully you will attend the conference.

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