FreeSWITCH 版本：1.10.12，以下简称 Fs
SIP 终端：Eyebeam 1.5.14.4
Eyebeam 设置注册的过期时间为 30
Fs 设置为 120，下面是详细配置：
<param name="sip-force-expires-max" value="120"/>
<param name="sip-force-expires-min" value="120"/>
<param name="sip-force-expires" value="120"/>
测试结果为：Eyebeam 续注册的时间大约为 110 秒，尊重了 Fs，只提前了一点点
第一次注册请求的日志为：
recv 547 bytes from udp/[192.168.31.166]:42690 at 11:56:12.650412:
------------------------------------------------------------------------
REGISTER sip:192.168.31.166 SIP/2.0
Via: SIP/2.0/UDP 192.168.31.166:42690;branch=z9hG4bK-d87543-c1699257fe720f17-1--d87543-;rport
Max-Forwards: 70
Contact: <sip:1001@192.168.31.166:42690;rinstance=c3f76577875a4ccd;transport=udp>
To: <sip:1001@192.168.31.166>
From: <sip:1001@192.168.31.166>;tag=1f43d91c
Call-ID: ZjIzNDI3YzE5NTIyMjBhNDUzOWZjOGNlNTg2ZTUzODE.
CSeq: 1 REGISTER
Expires: 30
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY, MESSAGE, SUBSCRIBE, INFO
User-Agent: eyeBeam release 1011d stamp 40820
Content-Length: 0
请留意，Expires 为 30，是一个独立的 SIP 头
Fs 回应 200 OK 的日志为：
SIP/2.0 200 OK
Via: SIP/2.0/UDP 192.168.31.166:42690;branch=z9hG4bK-d87543-294609005238a479-1--d87543-;rport=42690
From: <sip:1001@192.168.31.166>;tag=1f43d91c
To: <sip:1001@192.168.31.166>;tag=4aXXDKc0agt6N
Call-ID: ZjIzNDI3YzE5NTIyMjBhNDUzOWZjOGNlNTg2ZTUzODE.
CSeq: 2 REGISTER
Contact: <sip:1001@192.168.31.166:42690;rinstance=c3f76577875a4ccd;transport=udp>;expires=120
Date: Fri, 18 Oct 2024 11:56:12 GMT
User-Agent: FreeSWITCH-mod_sofia/1.10.12-dev-5976~218a00e2e9~64bit
Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, INFO, UPDATE, REGISTER, REFER, NOTIFY, PUBLISH, SUBSCRIBE
Supported: timer, path, replaces
Content-Length: 0
请留意，Fs 回应的 Expires 为 120，Expires 放到了 Contact 的参数里面（这是标准做法）
下面是 Eyebeam 的续注册日志：
recv 800 bytes from udp/[192.168.31.166]:42690 at 11:58:01.158276:
------------------------------------------------------------------------
REGISTER sip:192.168.31.166 SIP/2.0
Via: SIP/2.0/UDP 192.168.31.166:42690;branch=z9hG4bK-d87543-832df92ea024f538-1--d87543-;rport
Max-Forwards: 70
Contact: <sip:1001@192.168.31.166:42690;rinstance=c3f76577875a4ccd;transport=udp>
To: <sip:1001@192.168.31.166>
From: <sip:1001@192.168.31.166>;tag=1f43d91c
Call-ID: ZjIzNDI3YzE5NTIyMjBhNDUzOWZjOGNlNTg2ZTUzODE.
CSeq: 3 REGISTER
Expires: 30
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY, MESSAGE, SUBSCRIBE, INFO
User-Agent: eyeBeam release 1011d stamp 40820
Authorization: Digest username="1001",realm="192.168.31.166",nonce="ab6f2109-7bde-4b22-96fd-aec46a6b1f13",uri="sip:192.168.31.166",response="c3db123ada2a70362bdccb9208fa9c69",cnonce="5de6948dfa75d6d5ef669c640866b628",nc=00000002,qop=auth,algorithm=MD5
Content-Length: 0
请注意下面几个信息：
1. Call-ID 是同一个, CSeq 有增加，这明显是续注册请求；同时带了 Authorization 头（认证信息）。如果服务器设置的随机数没有过期，就不用再挑战了，直接回 200 OK
2. 11:58:01 同 11:56:12 之间大致相差 110秒, Eyebeam 尊重 Fs 的选择，而不是固执地使用自己 30 秒的设置
最后提一个问题: 如何让注册客户端立马下线，并且下次收到这个userid的注册请求时，总是失败？