<p>For reference, from sip grammar (rfc3261, section25):</p>

<pre><code>uri-parameters    =  *( ";" uri-parameter)
uri-parameter     =  transport-param / user-param / method-param
                     / ttl-param / maddr-param / lr-param / other-param

other-param       =  pname [ "=" pvalue ]
pname             =  1*paramchar
pvalue            =  1*paramchar
paramchar         =  param-unreserved / unreserved / escaped
param-unreserved  =  "[" / "]" / "/" / ":" / "&" / "+" / "$"
</code></pre>

<p>Therefore '[' and ']' are allowed in uri parameter, being part of 'param-unreserved' group of chars.</p>

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