This structure represents generic STUN string attributes, such as STUN USERNAME, PASSWORD, SOFTWARE, REALM, and NONCE attributes.
This describes STUN REALM attribute. The REALM attribute is present in requests and responses. It contains text which meets the grammar for "realm" as described in RFC 3261 , and will thus contain a quoted string (including the quotes).
This describes STUN NONCE attribute. The NONCE attribute is present in requests and in error responses. It contains a sequence of qdtext or quoted-pair, which are defined in RFC 3261 . See RFC 2617  for guidance on selection of nonce values in a server.
This describes STUN SOFTWARE attribute. The SOFTWARE attribute contains a textual description of the software being used by the agent sending the message. It is used by clients and servers. Its value SHOULD include manufacturer and version number.
This describes STUN USERNAME attribute. The USERNAME attribute is used for message integrity. It identifies the shared secret used in the message integrity check. Consequently, the USERNAME MUST be included in any request that contains the MESSAGE-INTEGRITY attribute.
This describes STUN PASSWORD attribute. If the message type is Shared Secret Response it MUST include the PASSWORD attribute.