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/**
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 * Unpublished - rights reserved under the Copyright Laws of the United States.
 * Copyright ? 2003 Sun Microsystems, Inc. All rights reserved.
 * Copyright ? 2005 BEA Systems, Inc. All rights reserved.
 *
 * Use is subject to license terms.
 *
 * This distribution may include materials developed by third parties. 
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 * Module Name   : JSIP Specification
 * File Name     : FromHeader.java
 * Author        : Phelim O'Doherty
 *
 *  HISTORY
 *  Version   Date      Author              Comments
 *  1.1     08/10/2002  Phelim O'Doherty    
 *~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 */
package javax.sip.header;



import java.text.ParseException;



/**
 * The From header field indicates the logical identity of the initiator

 * of the request, possibly the user's address-of-record. This may be different

 * from the initiator of the dialog.  Requests sent by the callee to the caller

 * use the callee's address in the From header field.

 * 

* Like the To header field, it contains a URI and optionally a display name, * encapsulated in a {@link javax.sip.address.Address}. It is used by SIP * elements to determine which processing rules to apply to a request (for * example, automatic call rejection). As such, it is very important that the * From URI not contain IP addresses or the FQDN of the host on which the UA is * running, since these are not logical names. *

* The From header field allows for a display name. A UAC SHOULD use * the display name "Anonymous", along with a syntactically correct, but * otherwise meaningless URI (like sip:[email protected]), if the * identity of the client is to remain hidden. *

* Usually, the value that populates the From header field in requests * generated by a particular UA is pre-provisioned by the user or by the * administrators of the user's local domain. If a particular UA is used by * multiple users, it might have switchable profiles that include a URI * corresponding to the identity of the profiled user. Recipients of requests * can authenticate the originator of a request in order to ascertain that * they are who their From header field claims they are. *

* Two From header fields are equivalent if their URIs match, and their * parameters match. Extension parameters in one header field, not present in * the other are ignored for the purposes of comparison. This means that the * display name and presence or absence of angle brackets do not affect * matching. *

    *
  • The "Tag" parameter - is used in the To and From header fields of SIP * messages. It serves as a general mechanism to identify a dialog, which is * the combination of the Call-ID along with two tags, one from each * participant in the dialog. When a User Agent sends a request outside of a dialog, * it contains a From tag only, providing "half" of the dialog ID. The dialog * is completed from the response(s), each of which contributes the second half * in the To header field. When a tag is generated by a User Agent for insertion into * a request or response, it MUST be globally unique and cryptographically * random with at least 32 bits of randomness. Besides the requirement for * global uniqueness, the algorithm for generating a tag is implementation * specific. Tags are helpful in fault tolerant systems, where a dialog is to * be recovered on an alternate server after a failure. A UAS can select the * tag in such a way that a backup can recognize a request as part of a dialog * on the failed server, and therefore determine that it should attempt to * recover the dialog and any other state associated with it. *
* For Example:
* From: "Bob" sips:[email protected] ;tag=a48s
* From: sip:[email protected];tag=887s
* From: Anonymous sip:[email protected];tag=hyh8
* * @author BEA Systems, NIST * @version 1.2 */ public interface FromHeader extends HeaderAddress, Parameters, Header { /** * Sets the tag parameter of the FromHeader. The tag in the From field of a * request identifies the peer of the dialog. When a UA sends a request * outside of a dialog, it contains a From tag only, providing "half" of * the dialog Identifier. *

* The From Header MUST contain a new "tag" parameter, chosen by the UAC * applicaton. Once the initial From "tag" is assigned it should not be * manipulated by the application. That is on the client side for outbound * requests the application is responsible for Tag assigmennment, after * dialog establishment the stack will take care of Tag assignment. * * @param tag - the new tag of the FromHeader * @throws ParseException which signals that an error has been reached * unexpectedly while parsing the Tag value. */ public void setTag(String tag) throws ParseException; /** * Gets the tag of FromHeader. The Tag parameter identified the Peer of the * dialogue and must always be present. * * @return the tag parameter of the FromHeader. */ public String getTag(); /** * Compare this FromHeader for equality with another. This method * overrides the equals method in javax.sip.Header. This method specifies * object equality as outlined by * RFC3261. * Two From header fields are equivalent if their URIs match, and their * parameters match. Extension parameters in one header field, not present * in the other are ignored for the purposes of comparison. This means that * the display name and presence or absence of angle brackets do not affect * matching. When comparing header fields, field names are always * case-insensitive. Unless otherwise stated in the definition of a * particular header field, field values, parameter names, and parameter * values are case-insensitive. Tokens are always case-insensitive. Unless * specified otherwise, values expressed as quoted strings are case-sensitive. * * @param obj the object to compare this FromHeader with. * @return true if obj is an instance of this class * representing the same FromHeader as this, false otherwise. * @since v1.2 */ public boolean equals(Object obj); /** * Name of FromHeader */ public final static String NAME = "From"; }





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