1. 1 Max Allocation with Reservation (MAR) BW Constraint Model for MPLS/DiffServ TE ( draft-ash-mpls-dste-bcmodel-max-alloc-resv-00.txt) qOutline vbrief review –‘you have read the draft’ –concepts: dynamic bandwidth reservation & MAR –analysis of MAR vissues vconclusions Jerry Ash gash@att.com

2. 2 MAR Bandwidth Constraint Model qallocates bandwidth to individual class types (CTs) qprotects allocated bandwidth by bandwidth reservation methods, as needed, but otherwise fully share bandwidth qdifferentiates high-priority, normal-priority, and best-effort priority services qprovides admission control to reject connection requests when needed to meet performance objectives qdoes not require use of preemption  mechanisms in use for 10+ years for multiservice voice/data bandwidth allocation in large-scale networks

3. 3 Dynamic Bandwidth Reservation qgives preference to certain traffic vfrom class types (CT) below their Bwalloc von preferred (shortest) path qpreferred traffic allowed to seize any idle bandwidth on a link qnon-preferred traffic (on CT above Bwalloc or on alternate paths) can seize bandwidth only if there is a minimum level of idle bandwidth (called the “bandwidth-reservation threshold”) qon congested link preferred traffic sees low loss while non-preferred traffic sees much higher loss vthis situation maintained across wide variation in percentage of preferred traffic vbandwidth reservation robust to traffic variations vas shown in mathematical models & in simulation studies vvery widely used in practice

4. 4 Dynamic Bandwidth Reservation Performance under 10% Overload

5. 5 Illustrative Use of MAR Link Load States & Allowed Load State qlocal link states kept of idle link bandwidth vavailable-bandwidth (ABW) –more than RBW + requested BW available vreserved-bandwidth (RBW) –less than RBW + request B available vbandwidth-not-available (BNA) –not enough bandwidth for flow/LSP qallowed load states for flow/LSP setup vwhen BW < BWalloc any idle link bandwidth can be seized if link not in BNA state vwhen BW > BWalloc, links must be in ABW state (RBW state not allowed)

6. 6 Illustrative Use of MAR

7. 7 Analysis of MAR qoptions compared vMAR -- flows/LSPs set up with dynamic bandwidth reservation vfull sharing -- flows/LSPs set up with no dynamic bandwidth reservation qfull-scale 135-switch national network simulation model v5 CTs -- normal priority voice, high priority voice, normal priority data, high priority data, & best-effort data v3 levels of traffic priority -- high, normal, best-effort

8. 8 Performance Comparison for MAR & Full Sharing Bandwidth Constraint Models 6X Focused Overload on Oakbrook (Total Network % Lost/Delayed Traffic)

9. 9 Performance Comparison for MAR & Full Sharing Bandwidth Constraint Models 50% General Overload (Total Network % Lost/Delayed Traffic)

10. 10 Issues qdefault BC model must consider all requirements vmust not require use of preemption to work well –many comments on list in support of this vmust provide BW isolation under congestion qcomparisons of BC models vRussian Doll model –works better when preemption is enabled –otherwise full sharing under overload can degrade performance of some CTs vmaximum allocation & maximum allocation with reservation –provide protection of allocated bandwidth under congestion –MAR allows BW sharing in absence of congestion qprotect from pathological setting of thresholds & use vissue for all BC models vnot needed, assume intelligent implementation

11. 11 Conclusions qMAR bandwidth constraint model vimproves performance over methods that lack bandwidth protection & allow more bandwidth sharing under congestion vachieves service differentiation for high-priority, normal-priority, and best-effort priority services vsupports greater efficiency in bandwidth sharing while still providing bandwidth isolation & protection against QoS degradation vdoes not require use of preemption vbandwidth reservation is necessary for stable & efficient network performance qproposed next steps in selecting default BC model vmake maximum allocation (MA) the default BC model –MA is well understood & very simple –requires no protocol extensions –operates well with or without preemption vmake Russian Doll (RD) an optional BC model (if TEWG agrees to have a second model) –should be used only when preemption is also used vcontinue to study possible extensions to MA, such as MAR, to improve performance

12. 12 Backup Slides

13. 13 Network Instability Under Congestion qunder congestion networks can exhibit “instability” with drastic loss of network throughput vby as much as 50% of traffic carrying capacity vshown mathematically in [NaM73, Kru82, Aki84] & in numerous simulation studies qsimple example: fully-connected network with first-choice routing on the 1-link direct path or, if unavailable, on (one of many) 2-link alternate paths vunder congestion 1-link direct path often not available & 2-link alternate path may be found and used v2-link connections take twice the resources as 1-link connections, which leads to more congestion and more alternate routing on 2-link connections vcan lead to two possible network states: –most or all connections on 1-link paths (desired condition) –most or all connections on 2-link paths (half the throughput) qsolution: use dynamic bandwidth reservation to favor shortest paths vs. longer alternate paths

14. 14 MAR Allowed Load State Threshold