The size of the message-body does not include the CRLF separating header fields and body. Any Content-Length greater than or equal to zero is a valid value. If no body is present in a message, then the Content-Length header field value MUST be set to zero.
contentLengththe content-length of the message body as a decimal number of octets.
javax.sip.InvalidArgumentExceptionif contentLength is less than zero.