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diff --git a/spec/dir-spec/downloading-from-other-auths.md b/spec/dir-spec/downloading-from-other-auths.md new file mode 100644 index 0000000..8f474e9 --- /dev/null +++ b/spec/dir-spec/downloading-from-other-auths.md @@ -0,0 +1,54 @@ +# Downloading information from other directory authorities + +## Downloading missing certificates from other directory authorities { #download-missing-certs } + +XXX when to download certificates. + +<a id="dir-spec.txt-3.6"></a> + +## Downloading server descriptors from other directory authorities { #download-missing-descs } + +Periodically (currently, every 10 seconds), directory authorities check +whether there are any specific descriptors that they do not have and that +they are not currently trying to download. +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 authority launches requests to the authorities for these +descriptors, such that each authority is only asked for descriptors listed +in its most recent vote. If 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. + +```text + Directory authorities must potentially cache multiple descriptors for each + router. Authorities must not discard any descriptor listed by any recent + consensus. If there is enough space to store additional descriptors, + authorities 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. + +<a id="dir-spec.txt-3.7"></a> + +## Downloading extra-info documents from other directory authorities { #download-missing-extrainfo } + +Periodically, an authority checks whether it is missing any extra-info +documents: in other words, if it has any server descriptors with an +extra-info-digest field that does not match any of the extra-info +documents currently held. If so, it downloads whatever extra-info +documents are missing. We follow the same splitting and back-off rules +as in section 3.6. + +<a id="dir-spec.txt-3.8"></a> |