通常VOLTE通话之前在IMS和SIP应用阶段我们会遇到各种各样的问题，针对问题可通过以下节点对进行排查： kangguoying20200927

1.终端注册前（Before Register)

       终端开机首先要完成网络驻留，期间包括小区选择、接入和附着等过程；之后终端才会发起到IMS的注册请消息。

 注册前需检查的内容包括：PDN，PDN名称，IP版本（IPv4,IPv6,IPv4IPv6或无要求），IPv6代理，NAS接口，PLMN要求，CSCF寻址等； kangguoying20200927

2.终端注册时（Right At Register) kangguoying20200927

      终端在注册时需注意 包括：ISIM、User ID和加密等信息;注册示例如下： kangguoying20200927

      REGISTER sip:(1)test.3gpp.com SIP/2.0 kangguoying20200927

      f: <sip:(2)[email]001010123456789@ims.mnc246.mcc081.3gppnetwork.org[/email]>;tag=2922225

      t: <sip:001010123456789@ims.mnc246.mcc081.3gppnetwork.org> kangguoying20200927

      CSeq: 2922203 REGISTER kangguoying20200927

      i: 2922206_181933240@2001:0:0:1::3 kangguoying20200927

      v: SIP/2.0/TCP [2001:0:0:1::3]:5060;branch=z9hG4bK3941737881

      Max-Forwards: 70 kangguoying20200927

      m: <sip:001010123456789@[2001:0:0:1::3]:5060>; kangguoying20200927

                        +sip.instance="<urn:gsma:imei:35425006-000655-0>"; kangguoying20200927

                        +g.3gpp.icsi-ref="urn%3Aurn-7%3A3gpp-service.ims.icsi.mmtel";

                        +g.3gpp.smsip kangguoying20200927

      Route: <sip:[2001:0:0:1::2]:5060;lr> kangguoying20200927

      l: 0 kangguoying20200927

      Authorization: Digest uri="sip:(3)test.3gpp.com",

                          username="(4)[email]001010123456789@test.3gpp.com[/email]",

                          response="", kangguoying20200927

                          realm="(5)test.3gpp.com",

                          nonce="" kangguoying20200927

      Expires: 600000 kangguoying20200927

      Require: sec-agree kangguoying20200927

      Proxy-Require: sec-agree

      k: path,sec-agree

      Allow: INVITE,BYE,CANCEL,ACK,NOTIFY,UPDATE,REFER,PRACK,INFO,MESSAGE,OPTIONS

      Security-Client: kangguoying20200927

      ipsec-3gpp; alg=hmac-md5-96; ealg=des-ede3-cbc; spi-c=799251570; spi-s=1387593208; port-c=8006; port-s=8906,

      ipsec-3gpp; alg=hmac-md5-96; ealg=aes-cbc; spi-c=799251570; spi-s=1387593208;port-c=8006; port-s=8906,

      ipsec-3gpp; alg=hmac-md5-96; ealg=null; spi-c=799251570; spi-s=1387593208;port-c=8006; port-s=8906,

      ipsec-3gpp; alg=hmac-sha-1-96; ealg=des-ede3-cbc; spi-c=799251570; spi-s=1387593208;port-c=8006; port-s=8906,

      ipsec-3gpp; alg=hmac-sha-1-96; ealg=aes-cbc; spi-c=799251570; spi-s=1387593208; port-c=8006; port-s=8906,

      ipsec-3gpp; alg=hmac-sha-1-96; ealg=null; spi-c=799251570; spi-s=1387593208; port-c=8006;port-s=8906

3.  终端注册后（After Register)  

     当收到注册接受“Accept）和回送”200 OK“时，注册并没有完成；需要关注是否：认证、IPSec算法、SUBSCRIPION/NOTIFICATION和终端是否要求”Precondition“；

4.VOLTE呼叫检查

    终端在注册完成后不能发起VOLTE呼叫，此时需对以下项目进行检查：

    4.1 SIP消息专用(UDP&TCP)端口； kangguoying20200927

    4.2 认证中是否包括”INVITE“（如不包括，则终端拒绝拨号）； kangguoying20200927

    4.3 注册前是否完成认证（如未认证，则终端不会发送"INVITE”消息）； kangguoying20200927

    4.4 终端是否要求“Precondition”（预留资源）； kangguoying20200927 kangguoying20200927

    4.5终端是否发出“PRACK”消息，或发送的PRACK消息中包含有“SDP”； kangguoying20200927

5.IPv4版本中IMS消息流程

    1)  Power-On UE（开机） kangguoying20200927

    2)  Initiate Access Network Registration (e.g, LTE Registration)初始注册（LTE网络ATTACH) kangguoying20200927

    3) UE -> NW : PDN Connectivity Request (for IMS PDN) (PDN连接，如IMS） kangguoying20200927

       *  UE需要 (DNS, CSCF IP地址等) kangguoying20200927

    4) UE <- NW : Activate Default EPS Bearer Context Request (for IMS PDN)（网络分配EP默认承载，如IMS PDN）

     5) UE -> NW : Activate Default EPS Bearer Context Accept（激活默认承载，上下文） kangguoying20200927

     6) UE IMS Stack -> UE SIP Stack : REGISTER（UE IMS与SIP协议栈）注册

     7) UE SIP Stack -> UE Radio Stack (PDCP -> PHY) : REGISTER（UE  PDCP->PHY)注册

     8) NW Radio Stack (PHY -> PDCP) -> NW SIP Stack : REGISTER（NW PHY->PDCP)SIP协议栈注册

     9) NW SIP Stack -> NW IMS Stack : REGISTER（NW SIP->IMS)协议栈注册

原文来自：http://www.sharetechnote.com/   

整理：kangguoying20200927

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