Congestion Notification Process for Real-Time Traffic draft-babiarz-tsvwg-rtecn-01.txt Jozef Babiarz Kwok Ho Chan Victor Firoiu 60 th IETF, Aug. 5 th, 2004

Aug. 5th, 2004Congestion Notification Process for Real-Time Traffic 60th IETF 2 Major Points Motivation –Simple network traffic condition notification –Control at application Would like to extend the usage of ECN for real-time UDP flows –Voice (IP telephony), video conferencing and video/multimedia streaming flows No impact to ECN for TCP (RFC 3168) –Building on concepts in RFC 3168 New or modified ECN semantics are needed –Some applications need to support two levels of traffic load indication ECN bits are used to convey on-path traffic levels detected in the network to the end-system / application As in RFC 3168, the end-system / application must react to ECN bit markings accordingly –This draft does not document behavior of the application DiffServ and different service classes are used to separate real-time from other flows

Aug. 5th, 2004Congestion Notification Process for Real-Time Traffic 60th IETF 3 Function Performed by Router Flow measurement is performed per service class –Measurement method used in router should not add delay or jitter to packets Provide indication for two congestion levels ECN capable router just measure flow rate and set ECN bits if rate was exceeded

Aug. 5th, 2004Congestion Notification Process for Real-Time Traffic 60th IETF 4 Function Performed by Application ECN bit marking provides indication to end-system / application that specific traffic level was exceeded for that flow ECN capable end-systems or applications take the appropriated action to avoid congestion Example: –Receiving end notifies the transmitting end when congestion has been encountered –If encountered during session setup The application may not setup the new session –After session was established Reduce sending rate Stop sending packets Or preempt the session

Aug. 5th, 2004Congestion Notification Process for Real-Time Traffic 60th IETF 5 Example: Admission Control Access link Access link Links where flow admission control is performed Non ECN capable router ECN capable router (ingress and egress ports) ECN capable routers (egress ports only) This could also be a LER ECN capable router (ingress port only) BW limited core link IP Network Application Manager UDP/RTP test flow Session Control (SIP or other)

Aug. 5th, 2004Congestion Notification Process for Real-Time Traffic 60th IETF 6 Usage Flow admission control of real-time traffic Rate control of established real-time flows Preemption of established real-time flows Features –Simple procedure in the network –Flow control is provide by application –Allows end-to-end control –Based on current network load conditions –Selective deployment of flow measurement and ECN marking in network –End stations need to be ECN capability

Aug. 5th, 2004Congestion Notification Process for Real-Time Traffic 60th IETF 7 Next Steps Explore alternative ECN semantics –Simplicity in router implementation –Looking at methods to prevent cheating Would like to request for comments and further discussion on the usage of ECN concept for controlling real-time UDP flows.