Sunday, October 23, 2016

Inter-Cluster Music on Hold (MoH)


You need to enable the network infrastructure to support multicasting including multicast routing and PIM
MMoH can't be transcoded, doesn't support E-LCAC/RSVP and doesn't support MTP
MMoH isn't supported on ICT video calls

The concept of Intercluster MoH is similar to Intracluster MoH. The same two steps:

  1. Stop the current media stream
  2. Start new stream with MoH server

In the scenario of ICT, the holder phone will select the source audio file, while SIP/H323 trunk will select the MoH server. Therefore, we will always have the holdee phone and MoH server in two separate clusters.

Stop the Current Media Stream

To disable the current media stream in SIP protocol, an SDP INVITE message is sent from the holder cluster with C=IN IP4 0.0.0.0 and a=inactive. The holdee cluster will respond with 200OK including a=inactive. This is always Early Offer regardless of the trunk configuration

 

INVITE sip:3000@10.45.230.10:5060;transport=tcp SIP/2.0
Via: SIP/2.0/TCP 10.170.10.200:5060;branch=z9hG4bK201f1b3afe
……
Content-Type: application/sdp
Content-Length: 240
v=0
o=CiscoSystemsCCM-SIP 8 2 IN IP4 10.170.10.200
s=SIP Call
c=IN IP4 0.0.0.0
b=TIAS:64000
b=AS:64
t=0 0
m=audio 24588 RTP/AVP 9 101
a=rtpmap:9 G722/8000
a=ptime:20
a=inactive
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15

SIP/2.0 200 OK
Via: SIP/2.0/TCP 10.170.10.200:5060;branch=z9hG4bK201f1b3afe
……
Content-Type: application/sdp
Content-Length: 244
v=0
o=CiscoSystemsCCM-SIP 8 2 IN IP4 10.45.230.10
s=SIP Call
c=IN IP4 10.170.4.226
b=TIAS:64000
b=AS:64
t=0 0
m=audio 32004 RTP/AVP 9 101
a=rtpmap:9 G722/8000
a=ptime:20
a=inactive
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15

To disable the current media stream in H323 protocol, the holder cluster sends TCS=0 (EmptyCapabilitySet). Then both clusters will exchange Close Logical Channel (CLC) and ACKs.


Start New Stream with MoH Server

Unicast Moh

SIP ICT can be configured as Delayed Offer or Early Offer. However, the flow of MoH messaging is fixed regardless of the ICT type.

  1. Holder cluster will send non-SDP INVITE message to establish call between holdee and MoH server

INVITE sip:3000@10.45.230.10:5060;transport=tcp SIP/2.0
Via: SIP/2.0/TCP 10.170.10.200:5060;branch=z9hG4bK2242496dea
From: < sip:2000@10.170.10.200> ;tag=8~7689b99f-a889-44ca-94c1-e77fb5464394-28366982
To: < sip:3000@10.45.230.10> ;tag=8~8901f810-e3b7-43de-b8ef-31fe13e397a7-28384555
Date: Sun, 13 Dec 2015 10:19:28 GMT
Call-ID: f7c7c980-66d14628-4-c80aaa0a@10.170.10.200
Supported: timer,resource-priority,replaces
Min-SE: 1800
User-Agent: Cisco-CUCM9.1
Allow: INVITE, OPTIONS, INFO, BYE, CANCEL, ACK, PRACK, UPDATE, REFER, SUBSCRIBE, NOTIFY
CSeq: 103 INVITE
Max-Forwards: 70
Expires: 180
Allow-Events: presence
Supported: X-cisco-srtp-fallback
Supported: Geolocation
Session-Expires: 1800;refresher=uas
P-Asserted-Identity: < sip:2000@10.170.10.200>
Remote-Party-ID: < sip:2000@10.170.10.200> ;party=calling;screen=yes;privacy=off
Contact: < sip:2000@10.170.10.200:5060;transport=tcp>
Content-Length: 0

  1. After exchanging provisional messages, Holdee cluster will send 200OK with SDP contents indicating the supported capabilities of Holdee

SIP/2.0 200 OK
Via: SIP/2.0/TCP 10.170.10.200:5060;branch=z9hG4bK2242496dea
……
Content-Type: application/sdp
Content-Length: 417
v=0
o=CiscoSystemsCCM-SIP 8 3 IN IP4 10.45.230.10
s=SIP Call
c=IN IP4 10.170.4.226
b=TIAS:64000
b=AS:64
t=0 0
m=audio 32202 RTP/AVP 9 0 8 116 18 101
a=rtpmap:9 G722/8000
a=ptime:20
a=rtpmap:0 PCMU/8000
a=ptime:20
a=rtpmap:8 PCMA/8000
a=ptime:20
a=rtpmap:116 iLBC/8000
a=ptime:20
a=maxptime:60
a=fmtp:116 mode=20
a=rtpmap:18 G729/8000
a=ptime:20
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15

  1. Holder Cluster will verify the capabilities of the Holdee and accordingly select the suitable capabilities of the MoH stream
  2. Holder Cluster will send ACK message to holdee cluster confirming the agreed capabilities

ACK sip:3000@10.45.230.10:5060;transport=tcp SIP/2.0
Via: SIP/2.0/TCP 10.170.10.200:5060;branch=z9hG4bK2346a41b8
From: < sip:2000@10.170.10.200> ;tag=8~7689b99f-a889-44ca-94c1-e77fb5464394-28366982
To: < sip:3000@10.45.230.10> ;tag=8~8901f810-e3b7-43de-b8ef-31fe13e397a7-28384555
Date: Sun, 13 Dec 2015 10:19:28 GMT
Call-ID: f7c7c980-66d14628-4-c80aaa0a@10.170.10.200
Max-Forwards: 70
CSeq: 103 ACK
Allow-Events: presence
Content-Type: application/sdp
Content-Length: 188
v=0
o=CiscoSystemsCCM-SIP 8 3 IN IP4 10.170.10.200
s=SIP Call
c=IN IP4 10.170.10.200
t=0 0
m=audio 4000 RTP/AVP 0
a=X-cisco-media:umoh
a=rtpmap:0 PCMU/8000
a=ptime:20
a=sendonly

Note that the message is including the following attributes:

a=X-cisco-media:umoh - This indicates to Holdee Cluster that the MoH stream is going to be Unicast Moh
c=IN IP4 10.170.10.200 - This indicates to Holdee Cluster the IP of the MoH server, for Holdee phone/gateway to connect. The port will be 4000
a=sendonly - This indicates to Holdee Cluster that the direction of the stream is unidirectional from MoH Server to Holdee phone/gateway

Multicast Moh

For MMoH the messaging is slightly different. MMoH isn't supported with EO ICT

  1. Holder cluster will send non-SDP INVITE message to probe the capabilities of the holdee

INVITE sip:3000@10.45.230.10:5060;transport=tcp SIP/2.0
Via: SIP/2.0/TCP 10.170.10.200:5060;branch=z9hG4bK932d17d236
From: < sip:2000@10.170.10.200> ;tag=14~7689b99f-a889-44ca-94c1-e77fb5464394-28367010
To: < sip:3000@10.45.230.10> ;tag=14~8901f810-e3b7-43de-b8ef-31fe13e397a7-28384562
Date: Sun, 13 Dec 2015 11:18:50 GMT
Call-ID: 44af9e00-66d15415-7-c80aaa0a@10.170.10.200
Supported: timer,resource-priority,replaces
Min-SE: 1800
User-Agent: Cisco-CUCM9.1
Allow: INVITE, OPTIONS, INFO, BYE, CANCEL, ACK, PRACK, UPDATE, REFER, SUBSCRIBE, NOTIFY
CSeq: 103 INVITE
Max-Forwards: 70
Expires: 180
Allow-Events: presence
Supported: X-cisco-srtp-fallback
Supported: Geolocation
Session-Expires: 1800;refresher=uas
P-Asserted-Identity: < sip:2000@10.170.10.200>
Remote-Party-ID: < sip:2000@10.170.10.200> ;party=calling;screen=yes;privacy=off
Contact: < sip:2000@10.170.10.200:5060;transport=tcp>
Content-Length: 0

  1. After exchanging provisional messages, Holdee cluster will send 200OK with SDP contents indicating the supported capabilities of Holdee

SIP/2.0 200 OK
Via: SIP/2.0/TCP 10.170.10.200:5060;branch=z9hG4bK932d17d236
……
Content-Type: application/sdp
Content-Length: 418
v=0
o=CiscoSystemsCCM-SIP 14 3 IN IP4 10.45.230.10
s=SIP Call
c=IN IP4 10.170.4.226
b=TIAS:64000
b=AS:64
t=0 0
m=audio 27928 RTP/AVP 9 0 8 116 18 101
a=rtpmap:9 G722/8000
a=ptime:20
a=rtpmap:0 PCMU/8000
a=ptime:20
a=rtpmap:8 PCMA/8000
a=ptime:20
a=rtpmap:116 iLBC/8000
a=ptime:20
a=maxptime:60
a=fmtp:116 mode=20
a=rtpmap:18 G729/8000
a=ptime:20
a=rtpmap:101 telephone

  1. Holder Cluster will verify the received capabilities and select the ones matching MoH server configuration
  2. Later, Holder Cluster will send ACK message confirming the selected capabilities back to Holdee Cluster

ACK sip:3000@10.45.230.10:5060;transport=tcp SIP/2.0
Via: SIP/2.0/TCP 10.170.10.200:5060;branch=z9hG4bK94686a6d9e
From: < sip:2000@10.170.10.200> ;tag=14~7689b99f-a889-44ca-94c1-e77fb5464394-28367010
To: < sip:3000@10.45.230.10> ;tag=14~8901f810-e3b7-43de-b8ef-31fe13e397a7-28384562
Date: Sun, 13 Dec 2015 11:18:50 GMT
Call-ID: 44af9e00-66d15415-7-c80aaa0a@10.170.10.200
Max-Forwards: 70
CSeq: 103 ACK
Allow-Events: presence
Content-Type: application/sdp
Content-Length: 207
v=0
o=CiscoSystemsCCM-SIP 14 3 IN IP4 10.170.10.200
s=SIP Call
c=IN IP4 0.0.0.0
b=TIAS:64000
b=AS:64
t=0 0
m=audio 24618 RTP/AVP 9
a=X-cisco-media:mmoh
a=rtpmap:9 G722/8000
a=ptime:20
a=inactive

Note that the message is including the following attributes:

c=IN IP4 0.0.0.0 - This indicates to Holdee Cluster that MoH stream is inactive
a=X-cisco-media:mmoh - This indicates to Holdee Cluster that the MoH stream is going to be Multicast Moh
a=inactive - This indicates to Holdee Cluster that MoH stream is inactive

  1. Holder Cluster will send SDP INVITE message to establish the call between MoH Server and Holdee

INVITE sip:3000@10.45.230.10:5060;transport=tcp SIP/2.0
Via: SIP/2.0/TCP 10.170.10.200:5060;branch=z9hG4bK952d3086b5
……
Content-Type: application/sdp
Content-Length: 199
v=0
o=CiscoSystemsCCM-SIP 14 4 IN IP4 10.170.10.200
s=SIP Call
c=IN IP4 239.1.1.1
t=0 0
m=audio 16384 RTP/AVP 0
a=X-cisco-media:mmoh+ConnSendOnly
a=rtpmap:0 PCMU/8000
a=ptime:20
a=recvonly

Note that the message is including the following attributes:

c=IN IP4 239.1.1.1 - This indicates to Holdee Cluster the Multicast Group address for holdee endpoint to join using IGMP report
a=X-cisco-media:mmoh+ConnSendOnly - This indicates to Holdee Cluster that Moh stream will be multicast and unidirectional
a=recvonly - This indicates to Holdee Cluster that Moh stream will be unidirectional

  1. Holdee Cluster will respond with 200OK message indicating that Holder settings have been accepted

SIP/2.0 200 OK
Via: SIP/2.0/TCP 10.170.10.200:5060;branch=z9hG4bK952d3086b5
…….
Content-Type: application/sdp
Content-Length: 219
v=0
o=CiscoSystemsCCM-SIP 14 4 IN IP4 10.45.230.10
s=SIP Call
c=IN IP4 239.1.1.1
t=0 0
m=audio 16384 RTP/AVP 0 101
a=rtpmap:0 PCMU/8000
a=ptime:20
a=recvonly
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15

  1. In the background, holdee will initiate IGMP process to join the MMoH stream

Note the difference between UMoH and MMoH signaling

  1. In UMoH, single Delayed Offer exchange is used to connect the Holdee to MoH server and get the stream
  2. In MMoH, two transactions are used
    1. Delayed Offer exchange with C=IN IP4 0.0.0.0/a=inactive to probe the capabilities of the holdee
    2. Early Offer exchange for holdee to join multicast group and get the stream

Resume Calls

Resuming held call follow the same steps which are:

  1. Stop the current media stream with MoH Server
  2. Start new stream with Holder. In this stage new codec negotiation will take place similar to new call setup. Also, this signaling will follow trunk type as EO or DO

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