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+<a id="bandwidth-file-spec.txt-2.1"></a>
+
+# Definitions
+
+The following nonterminals are defined in Tor directory protocol
+sections 1.2., 2.1.1., 2.1.3.:
+
+```text
+    bool
+    Int
+    SP (space)
+    NL (newline)
+    KeywordChar
+    ArgumentChar
+    nickname
+    hexdigest (a '$', followed by 40 hexadecimal characters
+      ([A-Fa-f0-9]))
+
+  Nonterminal defined section 2 of version-spec.txt [4]:
+
+    version_number
+
+  We define the following nonterminals:
+
+    Line ::= ArgumentChar* NL
+    RelayLine ::= KeyValue (SP KeyValue)* NL
+    HeaderLine ::= KeyValue NL
+    KeyValue ::= Key "=" Value
+    Key ::= (KeywordChar | "_")+
+    Value ::= ArgumentCharValue+
+    ArgumentCharValue ::= any printing ASCII character except NL and SP.
+    Terminator ::= "=====" or "===="
+                   Generators SHOULD use a 5-character terminator.
+    Timestamp ::= Int
+    Bandwidth ::= Int
+    MasterKey ::= a base64-encoded Ed25519 public key, with
+                  padding characters omitted.
+    DateTime ::= "YYYY-MM-DDTHH:MM:SS", as in ISO 8601
+    CountryCode ::= Two capital ASCII letters ([A-Z]{2}), as defined in
+                    ISO 3166-1 alpha-2 plus "ZZ" to denote unknown country
+                    (eg the destination is in a Content Delivery Network).
+    CountryCodeList ::= One or more CountryCode(s) separated by a comma
+                        ([A-Z]{2}(,[A-Z]{2})*).
+```
+
+Note that key_value and value are defined in Tor directory protocol
+with different formats to KeyValue and Value here.
+
+Tor versions earlier than 0.3.5.1-alpha require all lines in the file
+to be 510 characters or less. The previous limit was 254 characters in
+Tor 0.2.6.2-alpha and earlier. Parsers MAY ignore longer Lines.
+
+Note that directory authorities are only supported on the two most
+recent stable Tor versions, so we expect that line limits will be
+removed after Tor 0.4.0 is released in 2019.