15.1.2 UAS Behavior
15.1.2 UAS的行为

   A UAS first processes the BYE request according to the general UAS processing described in Section 8.2.  A UAS core receiving a BYE request checks if it matches an existing dialog.  If the BYE does not match an existing dialog, the UAS core SHOULD generate a 481 (Call/Transaction Does Not Exist) response and pass that to the server transaction.

?UAS首先根据第8.2节中描述的通用UAS处理来处理BYE请求。接收BYE请求的UAS核心检查它是否与现有对话匹配。如果BYE与现有对话不匹配，UAS核心应生成481（调用/事务不存在）响应，并将其传递给服务器事务。

      This rule means that a BYE sent without tags by a UAC will be rejected.  This is a change from RFC 2543, which allowed BYE without tags.

?此规则意味着UAC发送的不带标记的BYE将被拒绝。这是对RFC 2543的更改，RFC 2543允许BYE不带标签。

   A UAS core receiving a BYE request for an existing dialog MUST follow the procedures of Section 12.2.2 to process the request.  Once done, the UAS SHOULD terminate the session (and therefore stop sending and listening for media).  The only case where it can elect not to are multicast sessions, where participation is possible even if the other participant in the dialog has terminated its involvement in the session.  Whether or not it ends its participation on the session, the UAS core MUST generate a 2xx response to the BYE, and MUST pass that to the server transaction for transmission.

?收到对现有对话的BYE请求的UAS核心必须遵循第12.2.2节的程序来处理该请求。一旦完成，UAS应该终止会话（因此停止发送和侦听媒体）。唯一可以选择不参与的情况是多播会话，即使对话中的其他参与者已终止参与会话，也可以参与。无论是否结束对会话的参与，UAS核心都必须生成对BYE的2xx响应，并必须将其传递给服务器事务进行传输。

   The UAS MUST still respond to any pending requests received for that dialog.  It is RECOMMENDED that a 487 (Request Terminated) response be generated to those pending requests.

UAS仍然必须对收到的针对该对话的任何未决请求作出响应。建议对这些未决请求生成487（请求终止）响应。