Sunday, 23 October 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.