Software Distribution Platform

Conception for a software distribution platform for a distributed network of WRT54GS nodes.

The identified requirements are as follows:

• nodes may be turned off or disconnected for any period of time from the remaining network
• no centralized datastore (avoids single point of failure)
• updates need to be reliable and cross-compatible beginning with version 1.0.0 (allow update of an node running 1.0.0 with a network of version 1.5.99 nodes around and also allow updates even with versions that have bad routing)
• broken, untrustworthy and malicious nodes may not install software (or interfere with the updating process?)
• trustworthy developer team and CA
• all nodes should have the same software version running most of the time (ideally every second)

The ideas to meet those requirements:

• sign each software update package with a CA key
• CA public key is preinstalled with the base system on every node to check authenticity
• discovery mechanism for newer versions on neighbours (push and/or pull (broadcast and/or query))
• if newer version is available, fetch it (e.g. over existing TFTP)
• infection distribution mechanism (new version can be injected on any connected node)
• synchronize system clocks over NTP (using UDP port 123) with neighbours, guaranteeing similar system times
• include software starting time (and end time for experimental software) in each update package
• coordinated switch over to new version if system_time > start_time
• coordinated switch-back to non-experimental version if system_time > end_time

Wiedemann 19:02, 17 Nov 2004 (CET)