Thursday, November 20, 2008

Quality of Service (QoS) Mechanism Selection in SDP

The IESG (note: part of IETF) has approved a draft which enables negotiating which QoS mechanism to use for a particular media stream: end-to-end with a differentiation between upstream and downstream. Therefore, two new attributes have been defined: qos-mech-send and qos-mech-recv. However, currently only two QoS mechanisms are defined, namely nsis and rsvp. Other mechansims - existing or future ones - needs to be registerd through IANA. The following example describes a session which support RSVP and NSIS in both directions whith a preference on RSVP. That is, the order of the actual QoS mechanisms is important.

m=audio 55000 RTP/AVP 0
a=qos-mech-send: rsvp nsis
a=qos-mech-recv: rsvp nsis

The current draft can be found here.
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