Network Redundancy

On this page, you will learn how the layout of the Internet is redundant (more than one path from here to there) in order to ensure reliability.

CSN-1.B.5, CSN-1.B.7, CSN-1.E.3, CSN-1.E.4, CSN-1.E.5, CSN-1.E.6, CSN-1.E.7
CSN-1.A.5, CSN-1.A.6, CSN-1.B.6, CSN-1.E.2, CSN-1.E.5

Thomas (David) Petite (born 1956) is a member of the Fond du Lac Band of the Lake Superior Chippewa tribe. David is best known for his work on wireless enabled devices. He is one of the early inventors of the wireless ad hoc networks, a temporary decentralized type of wireless network that enables all mobile phones to work today. His inventions were also a driving force behind the development of what is now known as the "Smart Grid" which monitors and harnesses the power of wireless-enabled devices at a specific location.

Given the enormous number of devices on the Internet and the reality that pieces of a complex system fail at unexpected times (and often in groups of neighbors such as a whole city), the Internet had to be designed to be reliable. This is achieved by building many redundant connections into the physical systems of the Internet. That way, if part of the Internet fails, data can be re-routed via a different path. And such changes to the path can happen in transit because routing on the Internet is dynamic; it is not specified in advance. Creating such redundancy can require additional resources (such as additional computers and cables) but it also increases the Internet's fault tolerance (ability to work around problems) and helps the Internet scale (expand) to more devices and people.

  1. Talk with Your Partner Describe what's going on in this animation.
    Someone should follow-up with Dan about where these images came from. --MF, 8/29/19
    A network of nodes joined with edges, with a sender node and a receiver node. The sender is able to send a message to the receiver even when an intermediate node is damaged in the network, as the message is able to traverse an alternate path highlighting network's redundancy.

In the animation, a lightening bolt strikes one of the nodes. There are many reasons a node can fail, such as power failure, chip burnout, etc. The other thing that can happen is that the nodes can all be fine, but the green lines linking the nodes, which represent connections, could fail (e.g., a cable could be cut or disconnected, either accidentally or on purpose).

  1. graph of a network with a sender and a receiver at each end and multiple connections among multiple notes between them In this model of a network, what is the minimum number of nodes (connection points) that can stop working before the sender and the receiver can't communicate? (Other than the sender or the receiver themselves, of course.)
    graph of a network with a sender and a receiver at each end and multiple connections among multiple notes between them In the same model network, what is the maximum number of nodes that can fail and still let Sender and Receiver communicate?
  2. CSN-1.E
    Talk with Your Partner Write Out Your Thoughts
    1. Describe the benefits of fault tolerance. What kind of problems could arise with the connection of millions of devices across the planet that make it necessary for the Internet to be fault-tolerant?
    2. What feature(s) of the Internet makes it fault-tolerant?
    3. In what ways can the Internet fail?