Direct Routing with Local Media Optimization - 6-7 seconds silence

Copper Contributor


  • Oracle E-SBC (Acme Packet) with internal media interface and public interface for MS Teams Trunk and media.
  • Media Bypass enabled (always) with Local Media Optimisation
  • Client is in corporate network (internal), the media traffic should flow beetween client and internal media interface of the SBC (the Client cannot reach public IP-addresses directly, HTTP only via Proxy, E-SBC media interface is reachable from client network)

Problem: Incoming call to MSTeams Client via E-SBC. RTP from caller to callee is fine, but the RTP from the callee to the caller takes 6-7 seconds until it is established.


In the SIP flow you can see, that there is a ReINVITE from E-SBC to MSTreams Cloud, directly after the first 200 OK arrives at the SBC. But the Client/MSTeams SBC needs 6-7 seconds to answer the ReINVITE with the 200 OK. After that, everything is fine, and both can hear each other. But it takes 6-7 seconds until the caller can hear the callee.


Find attached a schematic SIP sequence diagram with the relevant messages and also a Wireshark capture with absolute times


Is that a normal behaviour (it's montioned here, but only for "some cases") or does anybody know how to get around this?




Sequencediagram_MSTeams_Direct-Routing_LMO-Problem.pngwireshark trace.png

2 Replies

Looking at the errors seems like the Oracle SBC is not sending all the SIP Options. Below was the response when I was working on a similar issue from the support team. Only difference was we had Meta Switch SBC instead of Oracle.

Looks like SBC does not send all the NOTIFY messages to indicate the progress of the call leg to the transferee, whereas we only see NOTIFY with 100 Trying. There should be at least couple more messages indicating session progress (18x) and answer (200OK) in line with what's happening on the call leg to transferee. Please address the issue to the SBC hosting provider and certified SBC vendor."

Check if this helps you.

With Regards
Satish U


@RealTime_M365 _if_ there are 183 responses missing, they are missing from the Microsoft side. A 18x message is a response to an INVITE. (And we are sending the INVITE).

So I don't think that this has something to do with our problem.