What is a Tor directory server?
The sole purpose of directory servers is to maintain information on the status of each node on the Tor network. The directory servers track when nodes appear and disappear, helping to ensure that the network adds new nodes promptly, and quickly drops unhealthy nodes from the network.
What is advertised bandwidth?
advertised bandwidth: the volume of traffic, both incoming and outgoing, that a relay is willing to sustain, as configured by the operator and claimed to be observed from recent data transfers. bandwidth history: the volume of incoming and/or outgoing traffic that a relay claims to have handled on behalf of clients.