It is based on if UA(User Agent) starts relaying RTP packets(active) or wait for the first packet from its peer (passive). It could be used for avoiding RTP proxy when one NAT is involved in the session.

For example if public User Agent supports passive role and SER knows it then public UA waits until gets first RTP packet from NATed User Agent, reads source IP address/port of the packet and starts relaying RTP packets to the source IP address/port.. It is also called symmetric RTP. This is the second situation out of three categories I stated.

This practice is also called Connection Oriented Media.

Ladislav

PS: Hard to say if this is being implemented because it is based on Internet Draft and it is not standard yet. I know just that some gateways are supporting it.

Gould, Aaron wrote:

what is the definition of a active ua and a passive ua?

thanks aaron

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From: serusers-bounces@lists.iptel.org on behalf of Ladislav Andel Sent: Tue 5/16/2006 4:40 AM To: serusers@lists.iptel.org Subject: Re: [Serusers] Active Passive role supported in UAs

Actually, it might be divided into three categories:

1. UA is advertising its role
2. UA is not advertising its role but can be set to be active or passive

(some Cisco gateways can do it) 3) UA can be set by sending a=direction:passive (or active) from SIP proxy. This will make the UA passive or active.

Any ideas about this topic?

Ladislav

Ladislav Andel wrote:

...

Hello everybody, I'm sorry for this off topic. I'm trying to make a list of UAs which supports active, passive role. (Regarding connection oriented media or so) These UAs can be gateways, hardphones, softphones, B2BUAs etc.

I would appreciate any contribution to my list and thank you, Ladislav

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