1 / 8

End-to-End Admission Control for DiffServ Networks with Pre-Congestion Notification

This document introduces the concept of Pre-Congestion Notification (PCN) and its use in achieving end-to-end controlled load (CL) service without requiring flow state or signaling in the core network. PCN allows for admission control and flow pre-emption for real-time flows in DiffServ networks. The document discusses the history of PCN, ongoing work, limitations, and possible enhancements.

carignan
Download Presentation

End-to-End Admission Control for DiffServ Networks with Pre-Congestion Notification

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Admission Control over DiffServ using Pre-Congestion Notification draft-briscoe-tsvwg-cl-phb-02.pdf draft-briscoe-tsvwg-cl-architecture-03.txt Philip Eardley,Bob Briscoe, Dave Songhurst - BT Francois Le Faucheur, Anna Charny, Vassilis Liatsos – Cisco Kwok-Ho Chan, Joe Babiarz, Stephen Dudley – Nortel Georgios Karagiannis - University of Twente / Ericsson Attila Bader, Lars Westberg - Ericsson IETF-66 tsvwg 10th July 2006

  2. Summary • Aim: • End-to-end Controlled Load (CL) service without flow state or signalling in the core / backbone • Solution: • Pre-Congestion Notification (PCN) builds on the concepts of ECN, RFC 3168, “The addition of Explicit Congestion Notification to IP”. • PCN-router marks packet “earlier” than ECN-router (bulk marking, not per flow) • admission marking • pre-emption marking • Feedback of these markings used in a particular network framework to achieve flow admission control and flow pre-emption • Applied to real-time flows (such as voice, video and multimedia streaming) in DiffServ networks. • History • Drafts from BT, Cisco, Nortel & Ericsson - working together intensively

  3. Drafts – ‘Pre-Congestion Notification marking’ draft-briscoe-tsvwg-cl-phb-02.pdf ‘An edge-to-edge Deployment Model for Pre-Congestion Notification: Admission Control over a DiffServ Region’ draft-briscoe-tsvwg-cl-architecture-03 • further deployment models using PCN (future work) • end-to-end / Open • others? Controlled environment • Signalling extensions • RSVP, draft-lefaucheur-rsvp-ecn-01 • NSIS (future work) • Border anti-cheating (related work) • draft-briscoe-tsvwg-re-ecn-border-cheat-01 • extending CL-region across operators • PCN over MPLS (related work) • MPLS & ECN/PCN, draft-davie-ecn-mpls-00

  4. Recent work On-going • Understanding behaviour of PCN better • Sensitivity to measurement accuracy, reaction timing & choice of parameter settings • Further simulations • Supplementing those reported last time • On-going & will be reported at the next ietf • Investigating algorithm variants • we believe the current algorithms are reasonably good • On-going work to assess if alternatives are better • eg would like same algorithm to work in other deployment models • Understanding & addressing known “corner cases” • New Section 5 indraft-briscoe-tsvwg-cl-architecture-03: Limitations of PCN & potential solutions • Otherwise drafts have (just) had clarifications & corrections, eg due to comments received (thanks) On-going Report now

  5. ECMP • PCN mechanism works well when all packets between a pair of ingress and egress gateways follow the same path • With ECMP (Equal Cost Multipath Routing) congestion-level-estimate is averaged over several paths • Therefore if paths have different pre-congestion level, the reaction is not quite accurate. • Similarly for Sustainable-aggregate-rate • Can avoid problem by tunnelling from ingress to egress (so get a path-specific Congestion-level-estimate) • Investigating other possible alternatives: • Eg (for flow pre-emption), only select from sub-set of flows that have actually had a Pre-emption Marked packet (or Router Marked packet)

  6. Sub-optimalities • Global fairness: • ‘Beat down’ effect: if more than one router congested, some aggregates may pre-empt more flows than they need to • Common problem for congestion control algorithms eg TCP, XCP • Could just accept it • Bi-directional sessions: • flow pre-emption for Aggregate A=>B independent of B=>A. • But if pre-empt flow in only one direction of a voice call, session is still torn down • End result: too many flows are pre-empted • Could just live with these sub-optimalities? • Investigating a number of possible enhancements

  7. Next steps & future work • Progress PCN marking draft • Standards track • get feedback / support • Progress deployment model draft • Informational track • CL-region: Edge-to-edge / Controlled • Do limited work on this doc • Signalling extensions for NSIS • To be discussed at NSIS meeting • Please say if you’d like to work on this • Other deployment model • End-to-end / Open • Ie fewer flows per link, and may be some non-PCN-routers • Not working on at the moment, but trying to ensure that marking (algorithms & encoding) wouldn’t preclude the End-to-end/Open deployment model

  8. Comments please!

More Related