commit 5c2ee924adbc0ec3b3ebd7f39e0139de5a15069e Author: Karsten Loesing karsten.loesing@gmx.net Date: Tue Jan 14 12:28:48 2014 +0100

Copy 4.3 "Downloading router descriptors" after 3.5.

This commit does not yet repair section numbering or references. --- dir-spec.txt | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+)

diff --git a/dir-spec.txt b/dir-spec.txt index e46da61..ad59fcd 100644 --- a/dir-spec.txt +++ b/dir-spec.txt @@ -1903,6 +1903,40 @@

XXX when to download certificates.

+4.3. Downloading and storing router descriptors (authorities and caches) + + Periodically (currently, every 10 seconds), directory servers check + whether there are any specific descriptors that they do not have and that + they are not currently trying to download. Caches identify these + descriptors by hash in the recent network-status consensus documents; + authorities identify them by hash in vote (if publication date is more + recent than the descriptor we currently have). + + [XXXX need a way to fetch descriptors ahead of the vote? v2 status docs can + do that for now.] + + If so, the directory server launches requests to the authorities for these + descriptors, such that each authority is only asked for descriptors listed + in its most recent vote (if the requester is an authority) or in the + consensus (if the requester is a cache). If we're an authority, and more + than one authority lists the descriptor, we choose which to ask at random. + + If one of these downloads fails, we do not try to download that descriptor + from the authority that failed to serve it again unless we receive a newer + network-status (consensus or vote) from that authority that lists the same + descriptor. + + Directory servers must potentially cache multiple descriptors for each + router. Servers must not discard any descriptor listed by any recent + consensus. If there is enough space to store additional descriptors, + servers SHOULD try to hold those which clients are likely to download the + most. (Currently, this is judged based on the interval for which each + descriptor seemed newest.) +[XXXX define recent] + + Authorities SHOULD NOT download descriptors for routers that they would + immediately reject for reasons listed in section 3.2. + 3.6. Computing a consensus from a set of votes

Given a set of votes, authorities compute the contents of the consensus