[tor-dev] Tor Bandwidth Measurements Document Format

[juga <juga@xxxxxxxxxx>]

Hi,

as commented with teor and pastly, i send in-line a draft specification
for the document format that the bandwidth scanner implementations
should produce.

I've left my own questions/notes in square brackets.

Thanks,
juga.

=======================================

          Tor Bandwidth Measurements Document Format
          [juga: which name should we give to this document?]

1. Scope and preliminaries

  This document describes the format of Tor's bandwidth measurements
  document, version X.X.X [juga: which version should be this?]
  and later.

  Since Tor version X.X.X [juga: which tor version?] the directory
  authorities use the bandwidth measurements document called
  "V3BandwidthsFile" and produced by Torflow [1]
  (format described in README.spec.txt [2]).

    The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
    NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and
    "OPTIONAL" in this document are to be interpreted as described in
    RFC 2119.

1.2. Acknowledgements

  The original bandwidth measurement scanner (Torflow) and format was
  created by mike. Teor suggested to write this specification while
  contributing on pastly's new bandwidth scanner implementation.

  This specification was revised after feedback from:

    XXX

1.3 Outline

  The bandwidth measurements mentioned in sections 3.4.1 and 3.4.2
  of dir-spec.txt [3] are obtained by bandwidth authorities, which are
  either directory authorities or other servers running bandwidth
  measurement scanners and sending the results to the former.
  [juga: it seems that bandwidth authorities have not been formally
  before]

2. Format details

  Bandwidth measurements MUST contain the following sections:
  - Header (exactly once)
  - Relays measurements (zero or more times)

  Each section (or entry) ends with a separator.

2.1. Nonterminals

  The following nonterminals are defined in the Onionoo details
  document specification [4]:

    fingerprint
    nickname

  In the bandwidth measurement documents nickname is optional.

  The following nonterminals are defined in the in dir-spec.txt:

    NL      (newline)
    SP      (space)

    "bw" = INT, the aggregated measured bandwidth of this relay, in
    kilobytes per second.

  We introduce the following nonterminals:
  [juga: this should probably be defined more formally and should
  probably link to other documents, which ones?]

    "version" = The name and the version of the bandwidth scannner
    software, such as "sbws 0.1.0".
    The name of the software, if absent, is assumed to be "torflow".
    [juga: which should be the version if absent?]

    "timestamp" = INT, the Unix Epoch time when the file was created.

2.2. Header format

  It MUST consists of:

    "timestamp" timestamp NL
    "version" version NL

2.3. Relay measurements format

  Relays measurements MUST consist of the following items.

    "node_id" fingerprint SP
    "bw" bandwidth SP

  When there are no more items, the "bw" item ends with NL instead of
  SP.

2.4. Optional extra items

  Different implementations of the bandwidth measurements scanners MAY
  include other items per relay.

  For instance, sbws includes:

    "rtt" = INT, Round Trip Time (to obtain 1B)

  Every relay measurement in sbws consists of:

    "node_id" fingerprint SP
    "bw" bandwidth SP
    "nick=" nickname SP
    "rtt=" rtt SP
    "time=" timestamp NL

  Every relay measurement in Torflow consists of:

    "node_id" fingerprint SP
    "bw" bandwidth SP
    "nick=" nickname SP
    "measured_at=" slice timestamp NL

  The "measured_at" does not correspond to the "time" in sbws.
  [juga: actually, if bwauths use "measured_at", then the code on them
  or sbws should be changed].

  Torflow includes other items that are out of the scope of this
  document.

References:

1. https://gitweb.torproject.org/torflow.git
2.
https://gitweb.torproject.org/torflow.git/tree/NetworkScanners/BwAuthority/README.spec.txt#n332
3. https://gitweb.torproject.org/torspec.git/tree/dir-spec.txt
4. https://metrics.torproject.org/onionoo.html#details


A. Sample data

A.1. Torflow

1523911758
node_id=$68A483E05A2ABDCA6DA5A3EF8DB5177638A27F80 bw=392760 nick=Test
measured_at=1523911725 updated_at=1523911725 pid_error=4.11374090719
pid_error_sum=4.11374090719 pid_bw=57136645 pid_delta=2.12168374577
circ_fail=0.2 scanner=/filepath

A.2. sbws

1523911758
version=0.1.0
node_id=$68A483E05A2ABDCA6DA5A3EF8DB5177638A27F80 bw=392760 nick=Test
rtt=380 time=1523911725
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