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Congestion Notification Process for Real-Time Traffic

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. Major Points. Motivation Simple network traffic condition notification Control at application

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Congestion Notification Process for Real-Time Traffic

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

  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 Congestion 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 Congestion 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 Congestion Notification Process for Real-Time Traffic 60th IETF

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

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