Spoke–hub distribution paradigm
The spoke-hub distribution paradigm (or model or network) is a system of connections arranged like a wire wheel, in which all traffic moves along spokes connected to the hub at the center. The model is commonly used in industry, in particular in transport, telecommunications and freight, as well as in distributed computing, where it is known as a star network.
Analysis of the model
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||This section contains a pro and con list, which is sometimes inappropriate. (August 2014)|
The hub-and-spoke model is most frequently compared to the point-to-point transit model.
- For a network of n nodes, only n - 1 routes are necessary to connect all nodes; that is, the upper bound is n - 1, and the complexity is O(n). This compares favorably to the routes, or O(n2), that would be required to connect each node to every other node in a point-to-point network. For example, in a system with 10 destinations, the spoke-hub system requires only 9 routes to connect all destinations, while a true point-to-point system would require 45 routes.
- The small number of routes may lead to more efficient use of transportation resources. For example, aircraft are more likely to fly at full capacity, and can often fly routes more than once a day.
- Complicated operations, such as package sorting and accounting, can be carried out at the hub, rather than at every node.
- Spokes are simple, and new ones can be created easily.
- Because the model is centralized, day-to-day operations may be relatively inflexible. Changes at the hub, or even in a single route, could have unexpected consequences throughout the network. It may be difficult or impossible to handle occasional periods of high demand between two spokes.
- Route scheduling is complicated for the network operator. Scarce resources must be used carefully to avoid starving the hub. Careful traffic analysis and precise timing are required to keep the hub operating efficiently.
- The hub constitutes a bottleneck or single point of failure in the network. Total cargo capacity of the network is limited by the hub's capacity. Delays at the hub (caused, for example, by bad weather conditions) can result in delays throughout the network. Delays at a spoke (from mechanical problems with an airplane, for example) can also affect the network.
- Cargo must pass through the hub before reaching its destination, requiring longer journeys than direct point-to-point trips. This trade-off may be desirable for freight, which can benefit from sorting and consolidating operations at the hub, but not for time-critical cargo and passengers.
- Two trips are required to reach most of the destinations, and the distance travelled may be very much longer than the actual distance between departure and destination points. Arriving at the hub and spending some time there increases the duration of the journey. Missing the connecting bus, flight, or train is possible and may be more troublesome than just a delay.
In 1955 Delta Air Lines pioneered the hub and spoke system at its hub in Atlanta, Georgia, in an effort to compete with Eastern Air Lines. In the mid-1970s FedEx adopted the hub and spoke model for overnight package delivery, and after the airline industry was deregulated in 1978, Delta's hub and spoke paradigm was adopted by several other airlines.
Airlines have extended the hub-and-spoke model in various ways. One method is to create additional hubs on a regional basis, and to create major routes between the hubs. This reduces the need to travel long distances between nodes that are close together. Another method is to use focus cities to implement point-to-point service for high traffic routes, bypassing the hub entirely.
The spoke-hub model is applicable to other forms of transportation:
- Sea transport, where feeder ships transport shipping containers from different ports to a central container terminal to be loaded onto larger vessels.
- Cargo airlines; for example, most UPS Airlines flights travel through its "Worldport" at Louisville International Airport, and a significant portion of FedEx Express parcels are processed at its "SuperHub" at Memphis International Airport.
- Freight rail transport, where cargo is hauled to a central exchange terminal. At the terminal, shipping containers are loaded from one freight car to another, and classification yards (marshalling yards) are used to sort freight cars into trains and divide them according to varying destinations.
- Public transit utilizes various transport hubs to allow passengers to transfer between different lines or transportation modes.
For passenger road transport, the spoke-hub model does not apply because drivers generally take the shortest or fastest route between two points.
The hub-and-spoke model has also been used in economic geography theory to classify a particular type of industrial district. Ann Markusen, an economic geographer, theorised about industrial districts, where a number of key industrial firms and facilities act as a hub, with associated businesses and suppliers benefiting from their presence and arranged around them like the spokes of a wheel. The chief characteristic of such hub-and-spoke industrial districts is the importance of one or more large companies, usually in one industrial sector, surrounded by smaller, associated businesses. Examples of cities with such districts include Seattle (where Boeing was founded), Silicon Valley (a high tech hub), and Toyota City, with Toyota.
East Asian relations
In the sphere of East Asian relations, according to Victor Cha, hub-and-spokes refers to the network of bilateral alliances between United States and other individual East Asian countries. This system constructs a dominant bilateral security architecture in East Asia, differing from the multilateral security architecture in Europe. United States acts as a "hub" and Asian countries such as South Korea, Taiwan and Japan fall under the category "spokes." Whereas there is a strong alliance between the hub and the spoke, there are no firmly established connections between the spokes themselves.
This system was famously inspired by John Foster Dulles, who served as US Secretary of State under the Eisenhower administration from 1953 to 1959. He addressed this term twice in Tokyo and once at the San Francisco Peace Treaty of September 1951. This led to talks for bilateral peace treaty between US and Japan. Security Treaty Between the United States and Japan of 1951, U.S.-South Korea Status of Forces Agreement of 1953 or U.S.-Republic of China Mutual Defense Treaty of 1954 (replaced by the Taiwan Relations Act) are some of the examples that manifests these bilateral relations.
In April 2014, all ten ASEAN defense chiefs and United States Secretary of Defense Chuck Hagel attended the U.S.-ASEAN Defense Forum in Hawaii. This marked the first time the U.S. had hosted the forum. This was part of an American attempt to get the countries to strengthen military ties between themselves.
- Hubs and Nodes
- Roundabout (traffic circle)
- Foreign policy of the United States for an example of international coordination through a third country.
- United Parcel Service
- Point-to-point transit (alternate shipping model)
- Delta Air Lines Newsroom - Press Kit. Delta.com. Retrieved on 2013-08-16.
- Cha, V. D. (2010). "Powerplay: Origins of the U.S. Alliance System in Asia". International Security 34 (3): 158–196. doi:10.1162/isec.2010.34.3.158.
- Hemmer, C.; Katzenstein, P. J. (2002). "Why is There No NATO in Asia? Collective Identity, Regionalism, and the Origins of Multilateralism". International Organization 56 (3): 575. doi:10.1162/002081802760199890. JSTOR 3078589.
- Keck, Zachary (2 April 2014). "US Swears Asia Pivot Isn't Dead". thediplomat.com. The Diplomat. Retrieved 3 April 2014.
- Badcock, B. A., 2002, Making Sense of Cities: A Geographical Survey, London: Arnold, pp. 63–94.
- Lawrence, H., 2004, "Aviation and the Role of Government", London: Kendall Hunt, pp. 227–230.
- Markusen, A., 1996, "Sticky Places in Slippery Space: A Typology of Industrial Districts", in Economic Geography, 72: 293–313.