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VCS flow-through or flow-around


our customer has VCS as SIP proxy. they dial out from SIP endpoint to our network. when I performed packet capture, I've not received any media from endpoint itself, instead I saw RTP was coming from VCS.

I know VCS-E always uses "flow through", but I expect VCS uses "flow around" and RTP coming from endpoint, not VCS. is there any configuration in VCS to decide media should be flow around or flow through?

thanks for any suggstion


Cisco Employee

VCS flow-through or flow-around

Hey Alex,

This article here should explain it. Its basically dependent on the license being consumed traversal or non-traversal.

Traversal call license usage on a Cisco VCS


Re: VCS flow-through or flow-around

In addition to the link adam posted, if you could draw down how the call flow looks like we might be able to say more.

On the vcs you talk about traversal and non-traversal/local calls.

That would reflect your flow-through (traversal) / flow-around (non-traversal).

Try to use the traversal/non-traversal that makes it easier for us and also you to understand when you read

documentations or look at the status of the vcs :-)

If the endpoint is behind NAT/Firewall/Traversal zone it is the expected behavior that you see the media

coming from the customers VCS-E.

And your posting is a bit confusing anyhow, as you write VCS-E and VCS, do you refer to a VCS-C?

If you have a setup where you offer for example a traversal zone for a customers VCS-C then this call

will be a traversal call which binds the media from the endpoint, to the VCS-C to the VCS-E.

If you need further help please make a drawing of the exact call flow and involved components.

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Re: VCS flow-through or flow-around

Hi Agoshtaei,

If the call goes through traversal zone then the media always goes through VCS (i.e. where VCSC and VCSE involved).

otherwise you can navigate on VCS Configuration > Calls  and from drop down option:

Optimal = VCS can remove itself from the media path, if possible

Always =  VCS always carries the media

regards, Ahmad

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