P2P E-Mail

E-mail is a mission-critical communication function for virtually all institutions, including corporations, universities, militaries, and families. Given the paramount importance of e-mail in modern society, it is disturbing how vulnerable the e-mail user can be to attacks and failures. Indeed, modern e-mail employs a server-centric design, in the user is critically dependent on its mail server, which receives, stores, and provides access to the user’s inbox. If this mail server is down – due to, for example, inadvertant faults, disasters, physical attacks or cyber attacks – the user can neither receive nor access its messages. Many mail service providers including Hotmail, YahooMail, and Critical Path have patched the dependability problem by creating mail-server clusters. The cluster is not only responsible for receiving, storing and delivering many users’ messages, but it also replicates messages across the different servers in the cluster. Thus, if one of the mail servers becomes unavailable, the cluster can continue to receive, store, and deliver messages. However, this patch only provides a marginal improvement in dependability, as it does not address scenarios in which the entire cluster is taken out, such as when the cluster is behind an access link that is severed for flooded with denial-of-service traffic, or when the building housing the cluster is physically bombed.