As I understand it, Tor clients can download "descriptors" from "directory caches" instead of download them directly from the directory authorities. This is to avoid overloading the network.

But I have seen that these three terms are sometimes used identically. In the context of the Tor network, are these three terms synonymous? Are there differences between them?

1 Answer 1


In version the directory spec v2 directory cache appear to be synonymous:

… Routers may act as directory mirrors (also called "caches"), …

I also took a look at the current spec (v3) which isn't as clear about it but I got the impression that it is used interchangeably.

When it comes to directory servers I found this:

Every Tor that is not a directory server (that is, those that do not have a DirPort set) …

I believe that includes directory caches/mirrors and authorities which would mean the meaning of directory server slightly differs.

Keep in mind that just because there is a formal definition for the terms, it doesn't mean it is used that way in the wild. I'd not be surprised to see all three word used synonymously.

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