This was only briefly mentioned in class in the first lecture, but one property of a dynamic network is the death of nodes. Bruce Schneier comments on an internet-specific form of nodal death called “link rot.” Link rot is, quite simply, the disappearance of information linked to on the internet.

There are two general problems with node death. The first is, of course, the disappearance of the information contained by the node. The second is the disappearance of the connection through that node.

The problem is solved in both cases, unsurprisingly, by redundancy. The disappearance of connections through a node is solved by having a great number of connections going through different nodes between the starting node and ending node. For instance, a page on a link sharing sites such as del.icio.us could be considered at local gatekeeper. If a user’s page were to disappear, then the use wouldn’t know how to find nodes linked through that site, since that node provided a connection to other nodes. These nodes may be local gatekeepers, shortening the path between you and other information. However, the internet is extremely connected, so longer paths to finding those “lost” nodes most likely exist. You can imagine a situation, however, where a node is a gatekeeper. There, the loss of the node would break the network into two smaller components.

The problem of the disappearance of the informational content of a node, however, is more troublesome. For instance, I once linked to a story on Yahoo! on my blog, only to come back and find that the link was dead less than a month later. I found a similar version on another site, but not an identical article.

The internet is responding to this in some fashion. The Way Back Machine was one of the first solutions to this problem- it provides an archive of the internet. Nowadays, Google does a similar thing with Google cache. Sure, the website for the prostitution ring Governor Spitzer was patronizing may no longer be operating, but Google’s cache is still up. Of course, this is not a perfect solution. The cache information will eventually disappear, too, and Google sadly does not store pictures.