由于SDP长度限制，终端发送a行过多导致视频呼叫建立失败

【问题现象】

Invite消息中的SDP长度大于网络限制，网络直接返回503 Service Unavailable，导致视频会话建立失败。
【原因定位】

问题原因：

1. INVITE消息中的SDP长度大于2048字节，网络直接返回503 Service Unavailable，导致视频电话建立失败。

[TX] 09.16 10:16:41
INVITE tel:13810813492;phone-context=ims.mnc007.mcc460.3gppnetwork.org
SIP/2.0
Supported: timer,100rel,precondition,sec-agree,histinfo P-Early-Media: supported
Proxy-Require: sec-agree Require: sec-agree Allow:
INVITE,ACK,OPTIONS,CANCEL,BYE,UPDATE,INFO,REFER,NOTIFY,MESSAGE,PRACK
P-Preferred-Identity: <sip:+8618811613433@bj.ims.mnc000.mcc460.3gppnetwork.org> User-Agent: Samsung IMS 5.0
Accept-Contact: *;+g.3gpp.icsi-ref=”urn%3Aurn-7%3A3gpp-service.ims.icsi.mmtel”;video P-Access-Network-Info: 3GPP-E-UTRAN-TDD;utran-cell-id-3gpp=4600710a7100d502 Session-Expires: 1800;refresher=uac
Min-SE: 90
P-Preferred-Service: urn:urn-7:3gpp-service.ims.icsi.mmtel Content-Type: application/sdp
Accept: application/sdp,application/3gpp-ims+xml
Route: <sip:[2409:8010:9210:1:1002:1002::]:9900;lr>
From:
<sip:+8618811613433@bj.ims.mnc000.mcc460.3gppnetwork.org>;tag=1309730347 To: <tel:13810813492;phone-context=ims.mnc007.mcc460.3gppnetwork.org>
Call-ID: 1370215984@2409:8800:9200:25bf::1
CSeq: 1 INVITE
Max-Forwards: 70
Contact: <sip:+8618811613433@[2409:8800:9200:25bf::1]:6000>;

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

+g.3gpp.mid-call;+g.3gpp.srvcc-alerting;+g.3gpp.ps2cs-srvcc-orig-pre-alerting;

+sip.instance=”<urn:gsma:imei:35818206-305334-0>”
Security-Verify: ipsec-3gpp;alg=hmac-md5-96;prot=esp;mod=trans;ealg=aes-cbc;

spi-c=2173635212;spi-s=4101955560;port-c=9950;port-s=9900
Via: SIP/2.0/TCP [2409:8800:9200:25bf::1]:6000;branch=z9hG4bK103530282smg;

transport=TCP;rport Content-Length: 2088

[RX] 09.16 10:16:43
SIP/2.0 503 Service Unavailable CSeq: 1 INVITE
registerd : false icon : -1 supported : 0 enabled : false VoPS : 1 SIP/2.0 503 Service Unavailable
Via: SIP/2.0/TCP [2409:8800:9200:25BF:0000:0000:0000:0001]:6000;branch

=z9hG4bK103530282smg;rport=5050;transport=TCP Call-ID: 1370215984@2409:8800:9200:25bf::1
From:
<sip:+8618811613433@bj.ims.mnc000.mcc460.3gppnetwork.org>;tag=1309730347 To: <tel:13810813492;phone-context=ims.mnc007.mcc460.3gppnetwork.org>;
tag=vvaxhopo CSeq: 1 INVITE
Warning: 399 00000.00000.A.129.402.228.255.255.05668.00002870 “Media Bearer Lost”
Content-Length: 0

2.  终端减少SDP中a行后，可正常建立通话。

[TX] 09.16 11:06:36
INVITE tel:13810813492;phone-context=ims.mnc007.mcc460.3gppnetwork.org
SIP/2.0
Supported: timer,100rel,precondition,sec-agree,histinfo P-Early-Media: supported
Proxy-Require: sec-agree Require: sec-agree Allow:
INVITE,ACK,OPTIONS,CANCEL,BYE,UPDATE,INFO,REFER,NOTIFY,MESSAGE,PRACK
P-Preferred-Identity: <sip:+8618811613433@bj.ims.mnc000.mcc460.3gppnetwork.org> User-Agent: Samsung IMS 5.0
Accept-Contact: *;+g.3gpp.icsi-ref=”urn%3Aurn-7%3A3gpp-service.ims.icsi.mmtel”;video P-Access-Network-Info: 3GPP-E-UTRAN-TDD;utran-cell-id-3gpp=4600710a7100d502 Session-Expires: 1800;refresher=uac
Min-SE: 90
P-Preferred-Service: urn:urn-7:3gpp-service.ims.icsi.mmtel Content-Type: application/sdp
Accept: application/sdp,application/3gpp-ims+xml
Route: <sip:[2409:8010:9210:1:1002:1002::]:9900;lr>
From: <sip:+8618811613433@bj.ims.mnc000.mcc460.3gppnetwork.org>; tag=568276553
To: <tel:13810813492;phone-context=ims.mnc007.mcc460.3gppnetwork.org>
Call-ID: 2506087614@2409:8800:920c:262a::1
CSeq: 1 INVITE
Max-Forwards: 70
Contact: <sip:+8618811613433@[2409:8800:920c:262a::1]:6000>;+g.3gpp.icsi-ref

=”urn%3Aurn-7%3A3gpp-service.ims.icsi.mmtel”;video;+g.3gpp.mid-call;
+g.3gpp.srvcc-alerting;+g.3gpp.ps2cs-srvcc-orig-pre-alerting;+sip.instance= “<urn:gsma:imei:35818206-000147-0>”
Security-Verify: ipsec-3gpp;alg=hmac-md5-96;prot=esp;mod=trans;ealg=aes-cbc; spi-c=3129873037;spi-s=3994572932;port-c=9950;port-s=9900
Via: SIP/2.0/TCP [2409:8800:920c:262a::1]:6000;branch=z9hG4bK536263972smg;

transport=TCP;rport Content-Length: 1645
…

[RX] 09.16 11:06:39
SIP/2.0 183 Session Progress
Via: SIP/2.0/TCP [2409:8800:920C:262A:0000:0000:0000:0001]:6000;branch
=z9hG4bK536263972smg;rport=5399;transport=TCP
Call-ID: 2506087614@2409:8800:920c:262a::1
From: <sip:+8618811613433@bj.ims.mnc000.mcc460.3gppnetwork.org>;tag=568276553 To:
<tel:13810813492;phone-context=ims.mnc007.mcc460.3gppnetwork.org>;tag=k4rf4wkf CSeq: 1 INVITE
Allow: INVITE,ACK,OPTIONS,CANCEL,BYE,UPDATE,INFO,REFER,NOTIFY,MESSAGE,PRACK Contact: <sip:[2409:8010:9210:0001:1002:1002:0000:0000]:9900;Hpt=8e92_16;CxtId=3;
TRC=ffffffff-ffffffff>;video;+g.3gpp.icsi-ref=”urn%3Aurn-7%3A3gpp-service. ims.icsi.mmtel”
Require: precondition,100rel RSeq: 1
P-E arly-Media: gated
Feature-Caps: *;+g.3gpp.srvcc;+g.3gpp.srvcc-alerting Content-Length: 1230
Content-Type: application/sdp

【解决方案】

三星终端减少SDP中携带a行，减少SDP长度进行问题规避。

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