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Diffstat (limited to 'doc/spec/path-spec.txt')
| -rw-r--r-- | doc/spec/path-spec.txt | 52 |
1 files changed, 35 insertions, 17 deletions
diff --git a/doc/spec/path-spec.txt b/doc/spec/path-spec.txt index 78f3b63bcb..8a85718a08 100644 --- a/doc/spec/path-spec.txt +++ b/doc/spec/path-spec.txt @@ -192,23 +192,41 @@ of their choices. below) - XXXX Choosing the length - For circuits that do not need to be "fast", when choosing among - multiple candidates for a path element, we choose randomly. - - For "fast" circuits, we pick a given router as an exit with probability - proportional to its bandwidth. - - For non-exit positions on "fast" circuits, we pick routers as above, but - we weight the bandwidth of Exit-flagged nodes depending - on the fraction of bandwidth available from non-Exit nodes. Call the - total bandwidth for Exit nodes under consideration E, - and the total bandwidth for all nodes under - consideration T. If E<T/3, we do not consider Exit-flagged nodes. - Otherwise, we weight their bandwidth with the factor (E-T/3)/E. This - ensures that bandwidth is evenly distributed over nodes in 3-hop paths. - - Similarly, guard nodes are weighted by the factor (G-T/3)/G, and not - considered for non-guard positions if this value is less than 0. + For "fast" circuits, we only choose nodes with the Fast flag. For + non-"fast" circuits, all nodes are eligible. + + For all circuits, we weight node selection according to router bandwidth. + + We also weight the bandwidth of Exit and Guard flagged nodes depending on + the fraction of total bandwidth that they make up and depending upon the + position they are being selected for. + + These weights are published in the consensus, and are computed as described + in Section 3.4.3 of dir-spec.txt. They are: + + Wgg - Weight for Guard-flagged nodes in the guard position + Wgm - Weight for non-flagged nodes in the guard Position + Wgd - Weight for Guard+Exit-flagged nodes in the guard Position + + Wmg - Weight for Guard-flagged nodes in the middle Position + Wmm - Weight for non-flagged nodes in the middle Position + Wme - Weight for Exit-flagged nodes in the middle Position + Wmd - Weight for Guard+Exit flagged nodes in the middle Position + + Weg - Weight for Guard flagged nodes in the exit Position + Wem - Weight for non-flagged nodes in the exit Position + Wee - Weight for Exit-flagged nodes in the exit Position + Wed - Weight for Guard+Exit-flagged nodes in the exit Position + + Wgb - Weight for BEGIN_DIR-supporting Guard-flagged nodes + Wmb - Weight for BEGIN_DIR-supporting non-flagged nodes + Web - Weight for BEGIN_DIR-supporting Exit-flagged nodes + Wdb - Weight for BEGIN_DIR-supporting Guard+Exit-flagged nodes + + Wbg - Weight for Guard+Exit-flagged nodes for BEGIN_DIR requests + Wbm - Weight for Guard+Exit-flagged nodes for BEGIN_DIR requests + Wbe - Weight for Guard+Exit-flagged nodes for BEGIN_DIR requests + Wbd - Weight for Guard+Exit-flagged nodes for BEGIN_DIR requests Additionally, we may be building circuits with one or more requests in mind. Each kind of request puts certain constraints on paths: |