ACCEPT, ACCEPT_ENCODING, ACCEPT_LANGUAGE, ACK, ALERT_INFO, ALLOW, ALLOW_EVENTS, ALPHA, AND, AT, AUTHENTICATION_INFO, AUTHORIZATION, BACK_QUOTE, BACKSLASH, BAR, BYE, CALL_ID, CALL_INFO, CANCEL, COLON, CONTACT, CONTENT_DISPOSITION, CONTENT_ENCODING, CONTENT_LANGUAGE, CONTENT_LENGTH, CONTENT_TYPE, CSEQ, DATE, DIGIT, DOLLAR, DOT, DOUBLEQUOTE, ENCRYPTION, END, EQUALS, ERROR_INFO, EVENT, EXCLAMATION, EXPIRES, FROM, GREATER_THAN, HAT, HIDE, HT, ID, IN_REPLY_TO, INVITE, L_CURLY, L_SQUARE_BRACKET, LESS_THAN, LPAREN, MAX_FORWARDS, MIME_VERSION, MIN_EXPIRES, MINUS, NOTIFY, NULL, OPTIONS, ORGANIZATION, PERCENT, PLUS, POUND, PRIORITY, PROXY_AUTHENTICATE, PROXY_AUTHORIZATION, PROXY_REQUIRE, QUESTION, QUOTE, R_CURLY, R_SQUARE_BRACKET, RACK, REASON, RECORD_ROUTE, REFER_TO, REGISTER, REPLY_TO, REQUIRE, RESPONSE_KEY, RETRY_AFTER, ROUTE, RPAREN, RSEQ, SEMICOLON, SERVER, SIP, SLASH, SP, STAR, START, SUBJECT, SUBSCRIBE, SUBSCRIPTION_STATE, SUPPORTED, TEL, TILDE, TIMESTAMP, TO, UNDERSCORE, UNSUPPORTED, USER_AGENT, VIA, WARNING, WHITESPACE, WWW_AUTHENTICATE |