IMS

Early Media

'Early Media' ? Sounds easy, but what does it realy mean ? Why it is called 'Early' media ?

Early Media is a mechanism to enable two users (UAs) to communicate (mainly exchange 'media') BEFORE a call is really established. The keyword is 'media exchange Before call setup'. That is where the word 'EARLY' came from.

Why we need this kind of 'EARLY' stuff ? One of the most important motivation/application is 'Ringback Tone'.

As you know, Ring tone comes before you pick up the phone (i.e, before call setup). Therefore, Early Media can be a good option for Ring tone.

How Early it should be to be early ?

Overall SIP signaling process for Early Media is as follows. In Early Media, a Media is streamed to UA right after 180 Ringing but before 200 OK for INVITE. It means the media is being played before the completion of the VoLTE INVITE session. It means the media plays EARLIER than the normal VoLTE stream and this is why it is called Early Media.

Example 1 : Mode = NRBT, NRBT Model = Forking Mode

Following is an example protocol sequence (SIP sequence and Radio Sequence Consolidated). I would look much more complicated than the illustration above. This is because some of the signaling shown here would show up in a specific condition (so don't be panic if you don't see some of the message not showing up in your log) and some of the steps in the above illustration got expanded into multiple steps in the following sequence.  Just try to understand overall logic and pay special attention to those items that is highlighed in blue or red color.

INVITE

INVITE sip:0123456789@msg.sharetechnote.com;user=phone SIP/2.0

Max-Forwards: 70

Route: <sip:[2001:0:0:1::2]:50543;lr>

Via: SIP/2.0/TCP [2001::1:34ee:998c:afe:656f]:39013;branch=z9hG4bK090078f6d-6d3f9587

Call-ID: 090078e51-6865ba59@2001::1:34ee:998c:afe:656f

CSeq: 1 INVITE

From: <sip:001010123456789@ims.mnc01.mcc001.3gppnetwork.org>;tag=54467090078e83-099de555

To: <sip:0123456789@msg.sharetechnote.com;user=phone>

Contact: <sip:001010123456789@[2001::1:34ee:998c:afe:656f]:39013;ob>;+g.3gpp.icsi-ref="urn%3Aurn-7%3A3gpp-service.ims.icsi.mmtel";video;+g.3gpp.srvcc-alerting;+sip.instance="<urn:gsma:imei:35910506-000422-0>"

Accept-Contact: *;+g.3gpp.icsi-ref="urn%3Aurn-7%3A3gpp-service.ims.icsi.mmtel";video

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

P-Preferred-Identity: <sip:001010123456789@ims.mnc01.mcc001.3gppnetwork.org>

P-Access-Network-Info: 3GPP-E-UTRAN-FDD;utran-cell-id-3gpp=0010100010000000

Security-Verify: ipsec-3gpp;q=0.1;alg=hmac-md5-96;prot=esp;mod=trans;ealg=null;spi-c=1168670468;spi-s=2529630210;port-c=50542;port-s=50543

Require: sec-agree

Supported: 100rel,precondition,timer

P-Early-Media: supported

Privacy: none

Accept: application/sdp,application/3gpp-ims+xml

Session-Expires: 1800

User-Agent: Test-client/4.0.0 H81110t

Proxy-Require: sec-agree

Content-Length: 758

Content-Type: application/sdp

v=0

o=sip:001010123456789@ims.mnc01.mcc001.3gppnetwork.org 3677677740 3677677740 IN IP6 2001:0:0:1::11

s=-

c=IN IP6 2001:0:0:1::11

t=0 0

m=audio 50010 RTP/AVP 97 98 99 100 101 102

b=AS:49  // RTP Bandwidth

b=RS:0    // RTCP Send Frequency

b=RR:1200  // RTCP Report Frequency

a=rtpmap:97 AMR-WB/16000/1

a=fmtp:97 mode-change-capability=2

a=rtpmap:98 AMR-WB/16000/1

a=fmtp:98 octet-align=1; mode-change-capability=2

a=rtpmap:99 telephone-event/16000

a=fmtp:99 0-15

a=rtpmap:100 AMR/8000/1

a=fmtp:100 mode-change-capability=2

a=rtpmap:101 AMR/8000/1

a=fmtp:101 octet-align=1; mode-change-capability=2

a=rtpmap:102 telephone-event/8000

a=fmtp:102 0-15

a=curr:qos local none

a=curr:qos remote none

a=des:qos mandatory local sendrecv

a=des:qos optional remote sendrecv

a=sendrecv

a=ptime:20

a=maxptime:240

180 Ringing

SIP/2.0 180 Ringing

Max-Forwards: 70

Via: SIP/2.0/TCP [2001:0:0:1::2]:51411;branch=z9hG4bK4e08ed70d45b4a15ab70d543018f0bc7131;rport;transport=tcp

Via: SIP/2.0/TCP [2001:0:0:1::2]:51370;branch=z9hG4bKf7c824a224824132a3b9eb00817e4031a8b27ff14d5246;transport=tcp

Via: SIP/2.0/TCP [2001:0:0:1::2]:51410;branch=z9hG4bK4e08ed70d45b4a15ab70d543018f0bc712f;rport;transport=tcp

Via: SIP/2.0/TCP [2001::1:1d38:5367:b2a1:e712]:39025;branch=z9hG4bK41312f44a-3ae4266a

From: <sip:001010123456789@ims.mnc01.mcc001.3gppnetwork.org>;tag=5446741312f3fd-5cd2bed0

To: <sip:0123456789@msg.sharetechnote.com;user=phone>;tag=1111111111

Call-ID: 41312f3d6-335e20ae@2001::1:1d38:5367:b2a1:e712

CSeq: 1 INVITE

Accept-Contact: *;+g.3gpp.icsi-ref="urn%3Aurn-7%3A3gpp-service.ims.icsi.mmtel";require;explicit

Record-Route: <sip:[2001:0:0:1::2]:28101;lr>

Require: 100rel    // require PRACK

Supported: 100rel

RSeq: 1

Privacy: none

User-Agent: TestUA2/43e5624

Feature-Caps: +g.3gpp.srvcc-alerting;+g.3gpp.mid-call

Content-Length: 0

Contact: <sip:0123456789@[2001:0:0:1::2]:51364;transport=tcp>;+g.3gpp.icsi-ref="urn:urn-7:3gpp-service.ims.icsi.mmtel";video;+g.3gpp.srvcc-alerting;+g.3gpp.mid-call

183 Session Progress

SIP/2.0 183 Session Progress

Max-Forwards: 70

Via: SIP/2.0/TCP [2001:0:0:1::2]:51410;branch=z9hG4bK4e08ed70d45b4a15ab70d543018f0bc712f;rport;transport=tcp

Via: SIP/2.0/TCP [2001::1:1d38:5367:b2a1:e712]:39025;branch=z9hG4bK41312f44a-3ae4266a

From: <sip:001010123456789@ims.mnc01.mcc001.3gppnetwork.org>;tag=5446741312f3fd-5cd2bed0

To: <sip:0123456789@msg.sharetechnote.com;user=phone>;tag=3333333333

Call-ID: 41312f3d6-335e20ae@2001::1:1d38:5367:b2a1:e712

CSeq: 1 INVITE

P-Early-Media: sendrecv

RSeq: 1

Require: 100rel    // require PRACK

Supported: 100rel

Require: precondition

Contact: <sip:0123456789@[2001:0:0:1::2]:51364;transport=tcp>;+g.3gpp.icsi-ref="urn:urn-7:3gpp-service.ims.icsi.mmtel";video;+g.3gpp.srvcc-alerting;+g.3gpp.mid-call

Record-Route: <sip:[2001:0:0:1::2]:51410;lr>

User-Agent: sharetechnote-VirtualUA/43e5624

Content-Type: application/sdp

Content-Length: 482

v=0

o=sharetechnote 756 102758 IN IP6 2001:0:0:1::2

s=-

i=Early Dialog Session

c=IN IP6 2001:0:0:1::2

t=0 0

m=audio 60000 RTP/AVP 107

b=AS:38

b=RS:0

b=RR:0

a=fmtp:107 octet-align=1;mode-set=2;mode-change-capability=2;max-red=0

a=maxptime:20

a=ptime:20

a=rtpmap:107 AMR-WB/16000

a=rtcp:60001

a=curr:qos local none

a=curr:qos remote none

a=des:qos mandatory remote sendrecv

a=des:qos mandatory local sendrecv

a=conf:qos remote sendrecv

a=content:g.3gpp.cat

a=inactive

PRACK

PRACK sip:0123456789@[2001:0:0:1::2]:51364;transport=tcp SIP/2.0

Via: SIP/2.0/TCP [2001:0:0:1::2]:51411;branch=z9hG4bK4e08ed70d45b4a15ab70d543018f0bc7133;rport;transport=tcp

Via: SIP/2.0/TCP [2001:0:0:1::2]:51370; branch=z9hG4bKf7c824a224824132a3b9eb00817e4031533ebe244d5246;transport=tcp

Max-Forwards: 69

Call-ID: 41312f3d6-335e20ae@2001::1:1d38:5367:b2a1:e712

CSeq: 2 PRACK

To: <sip:0123456789@msg.sharetechnote.com;user=phone>;tag=1111111111

From: <sip:001010123456789@ims.mnc01.mcc001.3gppnetwork.org>;tag=5446741312f3fd-5cd2bed0

RAck: 1 1 INVITE

Require: 100rel

Supported: precondition

Supported: 100rel

Privacy: none

User-Agent: TestUA2/43e5624

Content-Length: 0

Record-Route: <sip:[2001:0:0:1::2]:28101;lr>

RRC Connection Reconfiguration

In this step, a dedicated EPS bearer for playing the early media is established and TFT(Traffic Flow Template) for flowing RTP stream. Blue Parts is what you may pay attention to but may vary depending on UE / NW configuration. The Red part is what would the most important parts for the flow to go through.

rrcConnectionReconfiguration-r8

    dedicatedInfoNASList: 1 item

        Item 0

            DedicatedInfoNAS: 271fc34b39057200c506050126312631172230100840c35a...

                Non-Access-Stratum (NAS)PDU

                    ...

                    EPS quality of service

                        Length: 5

                        Quality of Service Class Identifier (QCI): QCI 1 (1)

                        Maximum bit rate for uplink : 38 kbps

                        Maximum bit rate for downlink : 49 kbps

                        Guaranteed bit rate for uplink : 38 kbps

                        Guaranteed bit rate for downlink : 49 kbps

                    Traffic Flow Template

                        Length: 23

                        001. .... = TFT operation code: Create new TFT (1)

                        ...0 .... = E bit: Parameters list is not included

                        .... 0010 = Number of packet filters: 2

                        Packet filter 0

                            00.. .... = Spare bit(s): 0

                            ..11 .... = Packet filter direction: Bidirectional (3)

                            .... 0000 = Packet filter identifier: 1 (0)

                            Packet evaluation precedence: 0x10 (16)

                            Packet filter length: 0x08 (8)

                            Packet filter component type identifier: Single local port type (64)

                                Port: 50010 // Port Number for RTP

                            Packet filter component type identifier: Single remote port type (80)

                                Port: 60000 // Port Number for RTP

                            Packet filter component type identifier: Protocol identifier

                                                                      /Next header type (48)

                                Protocol/header: UDP (0x11)

                        Packet filter 1

                            00.. .... = Spare bit(s): 0

                            ..11 .... = Packet filter direction: Bidirectional (3)

                            .... 0001 = Packet filter identifier: 2 (1)

                            Packet evaluation precedence: 0x11 (17)

                            Packet filter length: 0x08 (8)

                            Packet filter component type identifier: Single local port type (64)

                                Port: 50011 // Port Number for RTCP

                            Packet filter component type identifier: Single remote port type (80)

                                Port: 60001 // Port Number for RTCP

                            Packet filter component type identifier: Protocol identifier

                                                                     /Next header type (48)

                                Protocol/header: UDP (0x11)

    radioResourceConfigDedicated

        drb-ToAddModList: 1 item

            Item 0

                DRB-ToAddMod

                    eps-BearerIdentity: 7

                    drb-Identity: 3

                    pdcp-Config

                        discardTimer: ms100 (1)

                        rlc-UM

                    rlc-Config: um-Bi-Directional (1)

                    logicalChannelIdentity: 5

                    logicalChannelConfig

                        ul-SpecificParameters

                            priority: 6

                            prioritisedBitRate: kBps8 (1)

                            bucketSizeDuration: ms100 (1)

                            logicalChannelGroup: 1

        mac-MainConfig: explicitValue (0)

            explicitValue

                ul-SCH-Config

                drx-Config: setup (1)

                timeAlignmentTimerDedicated: infinity (7)

                phr-Config: setup (1)

                mac-MainConfig-v1020

        physicalConfigDedicated

            tpc-PDCCH-ConfigPUCCH: setup (1)

            tpc-PDCCH-ConfigPUSCH: setup (1)

            antennaInfo: defaultValue (1)

                defaultValue: NULL

UPDATE/SDP

UPDATE sip:0123456789@[2001:0:0:1::2]:51364;transport=tcp SIP/2.0

Max-Forwards: 70

Route: <sip:[2001:0:0:1::2]:62933;lr>

Via: SIP/2.0/TCP [2001::1:1d38:5367:b2a1:e712]:39025;branch=z9hG4bK4131d902e-3d63d9ef

Call-ID: 41312f3d6-335e20ae@2001::1:1d38:5367:b2a1:e712

CSeq: 3 UPDATE

From: <sip:001010123456789@ims.mnc01.mcc001.3gppnetwork.org>;tag=5446741312f3fd-5cd2bed0

To: <sip:0123456789@msg.sharetechnote.com;user=phone>;tag=3333333333

Contact: <sip:001010123456789@[2001::1:1d38:5367:b2a1:e712]:39025;ob>;+g.3gpp.icsi-ref="urn%3Aurn-7%3A3gpp-service.ims.icsi.mmtel";video;+g.3gpp.srvcc-alerting;+sip.instance="<urn:gsma:imei:35910506-000422-0>"

Accept-Contact: *;+g.3gpp.icsi-ref="urn%3Aurn-7%3A3gpp-service.ims.icsi.mmtel";video

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

P-Preferred-Identity: <sip:001010123456789@ims.mnc01.mcc001.3gppnetwork.org>

P-Access-Network-Info: 3GPP-E-UTRAN-FDD;utran-cell-id-3gpp=0010100010000000

Security-Verify: ipsec-3gpp;q=0.1;alg=hmac-md5-96;prot=esp;mod=trans;ealg=null;spi-c=3971908422;spi-s=1501624932;port-c=62932;port-s=62933

Require: precondition, sec-agree

Supported: precondition

User-Agent: SHARETECH TEST-IMS-client/4.0.0 H81110t

Proxy-Require: sec-agree

Content-Length: 462

Content-Type: application/sdp

v=0

o=sip:001010123456789@ims.mnc01.mcc001.3gppnetwork.org 3677690491 3677690492 IN IP6 2001:0:0:1::11

s=-

c=IN IP6 2001:0:0:1::11

t=0 0

m=audio 50010 RTP/AVP 107

b=AS:38 // RTP Bandwidth. This is different from AS in INVITE/SDP,

            // so it will trigger ESM: MODIFY EPS BEARER CONTEXT REQUEST in Radio Access Network

b=RS:0 // RTCP Send Frequency

b=RR:900 // RTCP Report Frequency

a=rtpmap:107 AMR-WB/16000

a=fmtp:107 mode-set=2; octet-align=1; mode-change-capability=2; max-red=0

a=curr:qos local sendrecv

a=curr:qos remote none

a=des:qos mandatory local sendrecv

a=des:qos mandatory remote sendrecv

a=sendrecv

a=ptime:20

a=maxptime:240

200 OK/SDP

SIP/2.0 200 OK

Max-Forwards: 70

Via: SIP/2.0/TCP [2001::1:1d38:5367:b2a1:e712]:39025;branch=z9hG4bK4131d902e-3d63d9ef

From: <sip:001010123456789@ims.mnc01.mcc001.3gppnetwork.org>;tag=5446741312f3fd-5cd2bed0

To: <sip:0123456789@msg.sharetechnote.com;user=phone>;tag=3333333333

Call-ID: 41312f3d6-335e20ae@2001::1:1d38:5367:b2a1:e712

CSeq: 3 UPDATE

Allow: INVITE, UPDATE, BYE, CANCEL, ACK, PRACK

Contact: <sip:[2001:0:0:1::2]:51370;transport=tcp>

Record-Route: <sip:[2001:0:0:1::2]:62933;lr>

Require: precondition

User-Agent: sharetechnote-VirtualUA/43e5624

Content-Type: application/sdp

Content-Length: 490

Privacy: none

v=0

o=sharetechnote 756 102759 IN IP6 2001:0:0:1::2

s=-

i=Early Dialog Session

c=IN IP6 2001:0:0:1::2

t=0 0

m=audio 60000 RTP/AVP 107

b=AS:38 // RTP Bandwidth. This is different from AS in INVITE/SDP,

             // so it will trigger ESM: MODIFY EPS BEARER CONTEXT REQUEST in Radio Access Network

b=RS:0  // RTCP Send Frequency

b=RR:0  // RTCP Report Frequency

a=fmtp:107 octet-align=1;mode-set=2;mode-change-capability=2;max-red=0

a=maxptime:20

a=ptime:20

a=rtpmap:107 AMR-WB/16000

a=rtcp:60001

a=curr:qos local sendrecv

a=curr:qos remote sendrecv

a=des:qos mandatory remote sendrecv

a=des:qos mandatory local sendrecv

a=conf:qos remote sendrecv

a=content:g.3gpp.cat

a=sendrecv

ESM: MODIFY EPS BEARER CONTEXT REQUEST

This is to Adjust the NAS layer throughput according the the specified bandwidth in SIP:UPDATE/SDP

dlInformationTransfer-r8

     dedicatedInfoType: dedicatedInfoNAS (0)

         dedicatedInfoNAS: 27399eeab8067200c95b050126262626

             Non-Access-Stratum (NAS)PDU

                 0010 .... = Security header type: Integrity protected and ciphered (2)

                 .... 0111 = Protocol discriminator: EPS mobility management messages (0x07)

                 Message authentication code: 0x399eeab8

                 Sequence number: 6

                 0111 .... = EPS bearer identity: EPS bearer identity value 7 (7)

                 .... 0010 = Protocol discriminator: EPS session management messages (0x02)

                 Procedure transaction identity: 0

                 NAS EPS session management messages: Modify EPS bearer context request (0xc9)

                 EPS quality of service - New EPS QoS

                     Element ID: 0x5b

                     Length: 5

                     Quality of Service Class Identifier (QCI): QCI 1 (1)

                     Maximum bit rate for uplink : 38 kbps

                     Maximum bit rate for downlink : 38 kbps

                     Guaranteed bit rate for uplink : 38 kbps

                     Guaranteed bit rate for downlink : 38 kbps

200 OK / SDP

SIP/2.0 200 OK

Max-Forwards: 70

Via: SIP/2.0/TCP [2001:0:0:1::2]:51411;branch=z9hG4bK4e08ed70d45b4a15ab70d543018f0bc7131;rport;transport=tcp

Via: SIP/2.0/TCP [2001:0:0:1::2]:51370;branch=z9hG4bKf7c824a224824132a3b9eb00817e4031a8b27ff14d5246;transport=tcp

Via: SIP/2.0/TCP [2001:0:0:1::2]:51410;branch=z9hG4bK4e08ed70d45b4a15ab70d543018f0bc712f;rport;transport=tcp

Via: SIP/2.0/TCP [2001::1:1d38:5367:b2a1:e712]:39025;branch=z9hG4bK41312f44a-3ae4266a

From: <sip:001010123456789@ims.mnc01.mcc001.3gppnetwork.org>;tag=5446741312f3fd-5cd2bed0

To: <sip:0123456789@msg.sharetechnote.com;user=phone>;tag=1111111111

Call-ID: 41312f3d6-335e20ae@2001::1:1d38:5367:b2a1:e712

CSeq: 1 INVITE

Allow: ACK, BYE, CANCEL, INVITE, PRACK, UPDATE

Accept-Contact: *;+g.3gpp.icsi-ref="urn%3Aurn-7%3A3gpp-service.ims.icsi.mmtel";require;explicit

Record-Route: <sip:[2001:0:0:1::2]:28101;lr>

User-Agent: sharetechnote-VirtualUA/43e5624

Content-Type: application/sdp

Content-Length: 732

Contact: <sip:0123456789@[2001:0:0:1::2]:51364;transport=tcp>;+g.3gpp.icsi-ref="urn:urn-7:3gpp-service.ims.icsi.mmtel";video;+g.3gpp.srvcc-alerting;+g.3gpp.mid-call

v=0

o=sharetechnote 784 552784 IN IP6 2001:0:0:1::2

s=-

i=A VOIP Session

c=IN IP6 2001:0:0:1::2

t=0 0

m=audio 60002 RTP/AVP 97 98 99 100 101 102

b=AS:49  // RTP Bandwidth. This is different from AS in Previous SDP (UPDATE/SDP),

             // so it will trigger ESM: MODIFY EPS BEARER CONTEXT REQUEST in Radio Access Network

b=RS:0

b=RR:1200

a=rtpmap:97 AMR-WB/16000/1

a=fmtp:97 mode-change-capability=2

a=rtpmap:98 AMR-WB/16000/1

a=fmtp:98 octet-align=1; mode-change-capability=2

a=rtpmap:99 telephone-event/16000

a=fmtp:99 0-15

a=rtpmap:100 AMR/8000/1

a=fmtp:100 mode-change-capability=2

a=rtpmap:101 AMR/8000/1

a=fmtp:101 octet-align=1; mode-change-capability=2

a=rtpmap:102 telephone-event/8000

a=fmtp:102 0-15

a=curr:qos local none

a=curr:qos remote none

a=des:qos mandatory local sendrecv

a=des:qos optional remote sendrecv

a=ptime:20

a=maxptime:240

a=sendrecv

a=rtcp:60003

200 OK / SDP

SIP/2.0 200 OK

Max-Forwards: 70

Via: SIP/2.0/TCP [2001:0:0:1::2]:51370;branch=z9hG4bKf7c824a224824132a3b9eb00817e4031a8b27ff14d5246;transport=tcp

Via: SIP/2.0/TCP [2001:0:0:1::2]:51410;branch=z9hG4bK4e08ed70d45b4a15ab70d543018f0bc712f;rport;transport=tcp

Via: SIP/2.0/TCP [2001::1:1d38:5367:b2a1:e712]:39025;branch=z9hG4bK41312f44a-3ae4266a

From: <sip:001010123456789@ims.mnc01.mcc001.3gppnetwork.org>;tag=5446741312f3fd-5cd2bed0

To: <sip:0123456789@msg.sharetechnote.com;user=phone>;tag=1111111111

Call-ID: 41312f3d6-335e20ae@2001::1:1d38:5367:b2a1:e712

CSeq: 1 INVITE

Allow: ACK, BYE, CANCEL, INVITE, PRACK, UPDATE

Accept-Contact: *;+g.3gpp.icsi-ref="urn%3Aurn-7%3A3gpp-service.ims.icsi.mmtel";require;explicit

Record-Route: <sip:[2001:0:0:1::2]:51410;lr>

User-Agent: sharetechnote-VirtualUA/43e5624

Content-Type: application/sdp

Content-Length: 732

Contact: <sip:0123456789@[2001:0:0:1::2]:51364;transport=tcp>;+g.3gpp.icsi-ref="urn:urn-7:3gpp-service.ims.icsi.mmtel";video;+g.3gpp.srvcc-alerting;+g.3gpp.mid-call

Privacy: none

P-Asserted-Identity: <sip:0123456789@msg.sharetechnote.com;user=phone>

v=0

o=sharetechnote 784 552784 IN IP6 2001:0:0:1::2

s=-

i=A VOIP Session

c=IN IP6 2001:0:0:1::2

t=0 0

m=audio 60002 RTP/AVP 97 98 99 100 101 102

b=AS:49  // RTP Bandwidth. This is different from AS in Previous SDP (UPDATE/SDP),

             // so it will trigger ESM: MODIFY EPS BEARER CONTEXT REQUEST in Radio Access Network

b=RS:0

b=RR:1200

a=rtpmap:97 AMR-WB/16000/1

a=fmtp:97 mode-change-capability=2

a=rtpmap:98 AMR-WB/16000/1

a=fmtp:98 octet-align=1; mode-change-capability=2

a=rtpmap:99 telephone-event/16000

a=fmtp:99 0-15

a=rtpmap:100 AMR/8000/1

a=fmtp:100 mode-change-capability=2

a=rtpmap:101 AMR/8000/1

a=fmtp:101 octet-align=1; mode-change-capability=2

a=rtpmap:102 telephone-event/8000

a=fmtp:102 0-15

a=curr:qos local none

a=curr:qos remote none

a=des:qos mandatory local sendrecv

a=des:qos optional remote sendrecv

a=ptime:20

a=maxptime:240

a=sendrecv

a=rtcp:60003

200 OK / SDP

SIP/2.0 200 OK

Max-Forwards: 70

Via: SIP/2.0/TCP [2001:0:0:1::2]:51410;branch=z9hG4bK4e08ed70d45b4a15ab70d543018f0bc712f;rport;transport=tcp

Via: SIP/2.0/TCP [2001::1:1d38:5367:b2a1:e712]:39025;branch=z9hG4bK41312f44a-3ae4266a

From: <sip:001010123456789@ims.mnc01.mcc001.3gppnetwork.org>;tag=5446741312f3fd-5cd2bed0

To: <sip:0123456789@msg.sharetechnote.com;user=phone>;tag=1111111111

Call-ID: 41312f3d6-335e20ae@2001::1:1d38:5367:b2a1:e712

CSeq: 1 INVITE

Allow: ACK, BYE, CANCEL, INVITE, PRACK, UPDATE

Accept-Contact: *;+g.3gpp.icsi-ref="urn%3Aurn-7%3A3gpp-service.ims.icsi.mmtel";require;explicit

Record-Route: <sip:[2001:0:0:1::2]:51410;lr>

User-Agent: sharetechnote-VirtualUA/43e5624

Content-Type: application/sdp

Content-Length: 732

Contact: <sip:0123456789@[2001:0:0:1::2]:51364;transport=tcp>;+g.3gpp.icsi-ref="urn:urn-7:3gpp-service.ims.icsi.mmtel";video;+g.3gpp.srvcc-alerting;+g.3gpp.mid-call

Privacy: none

P-Asserted-Identity: <sip:0123456789@msg.sharetechnote.com;user=phone>

v=0

o=sharetechnote 784 552784 IN IP6 2001:0:0:1::2

s=-

i=A VOIP Session

c=IN IP6 2001:0:0:1::2

t=0 0

m=audio 60002 RTP/AVP 97 98 99 100 101 102

b=AS:49

b=RS:0

b=RR:1200

a=rtpmap:97 AMR-WB/16000/1

a=fmtp:97 mode-change-capability=2

a=rtpmap:98 AMR-WB/16000/1

a=fmtp:98 octet-align=1; mode-change-capability=2

a=rtpmap:99 telephone-event/16000

a=fmtp:99 0-15

a=rtpmap:100 AMR/8000/1

a=fmtp:100 mode-change-capability=2

a=rtpmap:101 AMR/8000/1

a=fmtp:101 octet-align=1; mode-change-capability=2

a=rtpmap:102 telephone-event/8000

a=fmtp:102 0-15

a=curr:qos local none

a=curr:qos remote none

a=des:qos mandatory local sendrecv

a=des:qos optional remote sendrecv

a=ptime:20

a=maxptime:240

a=sendrecv

a=rtcp:60003

200 OK / SDP

SIP/2.0 200 OK

Max-Forwards: 70

Via: SIP/2.0/TCP [2001::1:1d38:5367:b2a1:e712]:39025;branch=z9hG4bK41312f44a-3ae4266a

From: <sip:001010123456789@ims.mnc01.mcc001.3gppnetwork.org>;tag=5446741312f3fd-5cd2bed0

To: <sip:0123456789@msg.sharetechnote.com;user=phone>;tag=1111111111

Call-ID: 41312f3d6-335e20ae@2001::1:1d38:5367:b2a1:e712

CSeq: 1 INVITE

Allow: ACK, BYE, CANCEL, INVITE, PRACK, UPDATE

Accept-Contact: *;+g.3gpp.icsi-ref="urn%3Aurn-7%3A3gpp-service.ims.icsi.mmtel";require;explicit

Record-Route: <sip:[2001:0:0:1::2]:62933;lr>

User-Agent: sharetechnote-VirtualUA/43e5624

Content-Type: application/sdp

Content-Length: 732

Contact: <sip:0123456789@[2001:0:0:1::2]:51364;transport=tcp>;+g.3gpp.icsi-ref="urn:urn-7:3gpp-service.ims.icsi.mmtel";video;+g.3gpp.srvcc-alerting;+g.3gpp.mid-call

P-Asserted-Identity: <sip:0123456789@msg.sharetechnote.com;user=phone>

Privacy: none

v=0

o=sharetechnote 784 552784 IN IP6 2001:0:0:1::2

s=-

i=A VOIP Session

c=IN IP6 2001:0:0:1::2

t=0 0

m=audio 60002 RTP/AVP 97 98 99 100 101 102

b=AS:49

b=RS:0

b=RR:1200

a=rtpmap:97 AMR-WB/16000/1

a=fmtp:97 mode-change-capability=2

a=rtpmap:98 AMR-WB/16000/1

a=fmtp:98 octet-align=1; mode-change-capability=2

a=rtpmap:99 telephone-event/16000

a=fmtp:99 0-15

a=rtpmap:100 AMR/8000/1

a=fmtp:100 mode-change-capability=2

a=rtpmap:101 AMR/8000/1

a=fmtp:101 octet-align=1; mode-change-capability=2

a=rtpmap:102 telephone-event/8000

a=fmtp:102 0-15

a=curr:qos local none

a=curr:qos remote none

a=des:qos mandatory local sendrecv

a=des:qos optional remote sendrecv

a=ptime:20

a=maxptime:240

a=sendrecv

a=rtcp:60003

ACK

ACK sip:0123456789@[2001:0:0:1::2]:51364;transport=tcp SIP/2.0

Max-Forwards: 70

Route: <sip:[2001:0:0:1::2]:62933;lr>

Via: SIP/2.0/UDP [2001::1:1d38:5367:b2a1:e712]:39025;branch=z9hG4bK4238bb47b-3b6ff5e5

Call-ID: 41312f3d6-335e20ae@2001::1:1d38:5367:b2a1:e712

CSeq: 1 ACK

From: <sip:001010123456789@ims.mnc01.mcc001.3gppnetwork.org>;tag=5446741312f3fd-5cd2bed0

To: <sip:0123456789@msg.sharetechnote.com;user=phone>;tag=1111111111

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

Require: sec-agree

User-Agent: SHARETECH TEST-IMS-client/4.0.0 H81110t

Proxy-Require: sec-agree

Content-Length: 0

ACK

ACK sip:0123456789@[2001:0:0:1::2]:51364;transport=tcp SIP/2.0

Via: SIP/2.0/TCP [2001:0:0:1::2]:51411;branch=z9hG4bK4e08ed70d45b4a15ab70d543018f0bc7138;rport;transport=tcp

Max-Forwards: 69

Via: SIP/2.0/UDP [2001::1:1d38:5367:b2a1:e712]:39025;branch=z9hG4bK4238bb47b-3b6ff5e5

Call-ID: 41312f3d6-335e20ae@2001::1:1d38:5367:b2a1:e712

CSeq: 1 ACK

From: <sip:001010123456789@ims.mnc01.mcc001.3gppnetwork.org>;tag=5446741312f3fd-5cd2bed0

To: <sip:0123456789@msg.sharetechnote.com;user=phone>;tag=1111111111

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

User-Agent: SHARETECH TEST-IMS-client/4.0.0 H81110t

Content-Length: 0

ESM : MODIFY EPS BEARER CONTEXT REQUEST

dlInformationTransfer-r8

    dedicatedInfoType: dedicatedInfoNAS (0)

        dedicatedInfoNAS: 27f7fbaafa077200c95b05013131313136178230100840c3...

            Non-Access-Stratum (NAS)PDU

                0010 .... = Security header type: Integrity protected and ciphered (2)

                .... 0111 = Protocol discriminator: EPS mobility management messages (0x07)

                Message authentication code: 0xf7fbaafa

                Sequence number: 7

                0111 .... = EPS bearer identity: EPS bearer identity value 7 (7)

                .... 0010 = Protocol discriminator: EPS session management messages (0x02)

                Procedure transaction identity: 0

                NAS EPS session management messages: Modify EPS bearer context request (0xc9)

                EPS quality of service - New EPS QoS

                    Element ID: 0x5b

                    Length: 5

                    Quality of Service Class Identifier (QCI): QCI 1 (1)

                    Maximum bit rate for uplink : 49 kbps

                    Maximum bit rate for downlink : 49 kbps

                    Guaranteed bit rate for uplink : 49 kbps

                    Guaranteed bit rate for downlink : 49 kbps

                Traffic Flow Template

                    Element ID: 0x36

                    Length: 23

                    100. .... = TFT operation code: Replace packet filters in existing TFT (4)

                    ...0 .... = E bit: Parameters list is not included

                    .... 0010 = Number of packet filters: 2

                    Packet filter 0

                        00.. .... = Spare bit(s): 0

                        ..11 .... = Packet filter direction: Bidirectional (3)

                        .... 0000 = Packet filter identifier: 1 (0)

                        Packet evaluation precedence: 0x10 (16)

                        Packet filter length: 0x08 (8)

                        Packet filter component type identifier: Single local port type (64)

                            Port: 50010

                        Packet filter component type identifier: Single remote port type (80)

                            Port: 60002

                        Packet filter component type identifier: Protocol identifier

                                                                 /Next header type (48)

                            Protocol/header: UDP (0x11)

                    Packet filter 1

                        00.. .... = Spare bit(s): 0

                        ..11 .... = Packet filter direction: Bidirectional (3)

                        .... 0001 = Packet filter identifier: 2 (1)

                        Packet evaluation precedence: 0x11 (17)

                        Packet filter length: 0x08 (8)

                        Packet filter component type identifier: Single local port type (64)

                            Port: 50011

                        Packet filter component type identifier: Single remote port type (80)

                            Port: 60003

                        Packet filter component type identifier: Protocol identifier

                                                                 /Next header type (48)

                            Protocol/header: UDP (0x11)

Further Reading :

[1] SIP Media Management: Early Offer vs. Late Offer

[2] SIP Media Management: Early Media vs. Late Media

[3] RFC 3960 Early Media and Ringing Tone Generation in SIP  

[3] RFC 5009 - 8.The P-Early-Media Header Field

[3] 3GPP 24.229

[4] 3GPP 24.268

A.5 Providing announcements to a terminating user just after the call is answered and before establishing direct communication session between end users