Spoke-hub distribution paradigm - AbsoluteAstronomy.com

The hub-and-spoke distribution paradigm (or model or network) is a system of connections arranged like a chariot

Chariot

The chariot is a type of horse carriage used in both peace and war as the chief vehicle of many ancient peoples. Ox carts, proto-chariots, were built by the Proto-Indo-Europeans and also built in Mesopotamia as early as 3000 BC. The original horse chariot was a fast, light, open, two wheeled...

wheel, in which all traffic moves along spoke
Spoke
A spoke is one of some number of rods radiating from the center of a wheel , connecting the hub with the round traction surface....

s connected to the hub at the center. The model is commonly used in industry, in particular in transport

Transport

Transport or transportation is the movement of people, cattle, animals and goods from one location to another. Modes of transport include air, rail, road, water, cable, pipeline, and space. The field can be divided into infrastructure, vehicles, and operations...

, telecommunications and freight, as well as in distributed computing

Distributed computing

Distributed computing is a field of computer science that studies distributed systems. A distributed system consists of multiple autonomous computers that communicate through a computer network. The computers interact with each other in order to achieve a common goal...

Analysis of the model

The hub-and-spoke model is most frequently compared to the point-to-point transit

Point-to-point transit

Point-to-point transit refers to a transportation system where a plane, bus or train travels directly to a destination, rather than going through a central hub...

model.

Benefits

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
Big O notation
In mathematics, big O notation is used to describe the limiting behavior of a function when the argument tends towards a particular value or infinity, usually in terms of simpler functions. It is a member of a larger family of notations that is called Landau notation, Bachmann-Landau notation, or...

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 generally leads 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.

Customers may find the network more intuitive. Scheduling is convenient for them since there are few routes, with frequent service.

Drawbacks

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
Single point of failure
A single point of failure is a part of a system that, if it fails, will stop the entire system from working. They are undesirable in any system with a goal of high availability or reliability, be it a business practice, software application, or other industrial system.-Overview:Systems can be made...

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 flights are required to reach the most of the destinations. Landing on the hub and spending some time there increases the duration of the journey (safety screening may be necessary again before boarding the second plane). Miss of the connecting flight is possible and may be more troublesome than just a flight delay.

Commercial aviation

In 1955 Delta Air Lines

Delta Air Lines

Delta Air Lines, Inc. is a major airline based in the United States and headquartered in Atlanta, Georgia. The airline operates an extensive domestic and international network serving all continents except Antarctica. Delta and its subsidiaries operate over 4,000 flights every day...

pioneered the hub and spoke system at its hub in Atlanta

Atlanta, Georgia

Atlanta is the capital and most populous city in the U.S. state of Georgia. According to the 2010 census, Atlanta's population is 420,003. Atlanta is the cultural and economic center of the Atlanta metropolitan area, which is home to 5,268,860 people and is the ninth largest metropolitan area in...

, Georgia

Georgia (U.S. state)

Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...

http://www.delta.com/about_delta/corporate_information/delta_stats_facts/delta_through_decades/index.jsp, in an effort to compete with Eastern Air Lines

Eastern Air Lines

Eastern Air Lines was a major United States airline that existed from 1926 to 1991. Before its dissolution it was headquartered at Miami International Airport in unincorporated Miami-Dade County, Florida.-History:...

. In the mid-1970s FedEx adopted the hub and spoke model for overnight package delivery, and after the airline industry was deregulated

Airline Deregulation Act

The Airline Deregulation Act is a United States federal law signed into law on October 24, 1978. The main purpose of the act was to remove government control over fares, routes and market entry from commercial aviation...

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

Focus city

In the airline industry, a focus city is a location that is not a hub, but from which the airline has non-stop flights to several destinations other than its hubs...

to implement point-to-point service for high traffic routes, bypassing the hub entirely.

Transportation

The spoke-hub model is applicable to other forms of transportation:

Sea transport
Ship transport
Ship transport is watercraft carrying people or goods . Sea transport has been the largest carrier of freight throughout recorded history. Although the importance of sea travel for passengers has decreased due to aviation, it is effective for short trips and pleasure cruises...

, where feeder ship
Feeder ship
Feeder vessels or feeder ships are ships of various sizes, but mostly understood to be sea going vessels with an average capacity of carrying to . Feeders collect shipping containers from different ports and transport them to central container terminals where they are loaded to bigger vessels. In...

s transport shipping containers from different ports to a central container terminal to be loaded onto larger vessels.
Cargo airline
Cargo airline
Cargo airlines are airlines dedicated to the transport of cargo. Some cargo airlines are divisions or subsidiaries of larger passenger airlines.-Logistics:...

s; for example, most UPS Airlines
UPS Airlines
UPS Airlines is an American cargo airline owned by United Parcel Service Inc. . The company is headquartered in Louisville, Kentucky. Its home airport is located at Louisville International Airport...

flights travel through its "Worldport
Worldport (UPS air hub)
Worldport is the worldwide air hub for UPS located at the Louisville International Airport in Louisville, Kentucky. Although UPS has had a hub at Louisville since 1980, the term was not used officially by the company until 2002, after a $1 billion, five-year expansion...

" at Louisville International Airport
Louisville International Airport
Louisville International Airport is a joint civil-military public airport centrally located in the city of Louisville in Jefferson County, Kentucky, USA. The airport covers 1,200 acres and has three runways. Its IATA airport code SDF is based on the airport's former name, Standiford Field...

, and a significant portion of FedEx Express parcels are processed at its "SuperHub" at Memphis International Airport
Memphis International Airport
Memphis International Airport is a joint civil-military public airport located three miles south of the central business district of Memphis, a city in Shelby County, Tennessee, United States....

.
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 yard
Classification yard
A classification yard or marshalling yard is a railroad yard found at some freight train stations, used to separate railroad cars on to one of several tracks. First the cars are taken to a track, sometimes called a lead or a drill...

s (marshalling yards) are used to sort freight cars into trains and divide them according to varying destinations.
Public transit
Public transport
Public transport is a shared passenger transportation service which is available for use by the general public, as distinct from modes such as taxicab, car pooling or hired buses which are not shared by strangers without private arrangement.Public transport modes include buses, trolleybuses, trams...

utilizes various transport hubs to allow passengers to transfer between different lines or transportation modes.

For passenger road transport

Road transport

Road transport or road transportation is transport on roads of passengers or goods. A hybrid of road transport and ship transport is the historic horse-drawn boat.-History:...

, the spoke-hub model does not apply because drivers generally take the shortest or fastest route between two points.

Industrial distribution

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

Boeing

The Boeing Company is an American multinational aerospace and defense corporation, founded in 1916 by William E. Boeing in Seattle, Washington. Boeing has expanded over the years, merging with McDonnell Douglas in 1997. Boeing Corporate headquarters has been in Chicago, Illinois since 2001...

was founded) and Toyota City, with Toyota

Toyota Motor Corporation