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Enhancing Bandwidth Efficiency with MAR: A Detailed Analysis of the Constraint Model

This document discusses the Max Allocation with Reservation (MAR) Bandwidth Constraint Model intended for MPLS/DiffServ traffic engineering. It presents updated draft specifications, outlining the model’s efficiency in bandwidth sharing and protection mechanisms under congestion while allowing flexible bandwidth allocation. The paper includes simulation results comparing MAR, MAM, and No-DSTE under various network overload scenarios, including failures and traffic variations. Insights on setting bandwidth constraints and conclusions for future work are also provided, emphasizing the model's practical applicability in large-scale networks.

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Enhancing Bandwidth Efficiency with MAR: A Detailed Analysis of the Constraint Model

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  1. Max Allocation with Reservation (MAR)BW Constraint Model for MPLS/DiffServ TE & Performance Comparisons(draft-ietf-tewg-diff-te-mar-01.txt) • Outline • updates to draft • simplified functional specification • setting bandwidth constraints in MAR & MAM • new simulation analysis results • conclusions & next steps Jerry Ash gash@att.com

  2. MAR Bandwidth Constraint Model • supports greater efficiency in bandwidth sharing • provides protection of allocated bandwidth under congestion • allows bandwidth sharing in absence of congestion • by bandwidth reservation methods, robust to traffic variations • for CTs below their bandwidth constraint BCc • can seize any idle bandwidth on a link • for CTs above their bandwidth constraint BCc • can seize bandwidth if idle bandwidth > bandwidth-reservation threshold • meets all requirements for BC models • works well with or without preemption • mechanisms in use for 10+ years • for multiservice voice/data bandwidth allocation in large-scale networks

  3. Updates to Current Draft (draft-ietf-tewg-diff-te-mar-01.txt) • changes in notation to align with DSTE notation: • RESERVED_BW, UNRESERVED_BW, MAX_RESERVABLE_BW, bandwidth constraint (BCc), etc. • NORMALIZED(CTc) deleted • added Section 3 'assumptions & applicability', as agreed in IETF-56/TEWG meeting • clarified/simplified functional specification in Section 4 • added Section 5 ‘setting bandwidth constraints’ • explain how BCc set for MAR • added ANNEX A • moved descriptive material on MAR operation & analysis • added new simulation results, compare MAR, MAM, & No-DSTE: • simulation for focus overload & 50% general overload • simulations for single link failure and multiple link failure • simulations adjusting the MAM bandwidth allocations & observations/sensitivities in setting MAM bandwidth constraints

  4. Functional Specification of MAR • for bandwidth request = DBW on CTc on link k: • for LSP on high priority or normal priority CTc: • if RESERVED_BWck <= BCc: admit if DBW <= UNRESERVED_BWk • if RESERVED_BWck > BCc: admit if DBW <= UNRESERVED_BWk - RBW_THRESk • for LSP on best-effort priority CTc: • allocated bandwidth BCc = 0 • DiffServ queuing admits BE packets only if available link bandwidth • normal semantics of setup & holding priority apply • cross-CT preemption is permitted when preemption enabled

  5. Setting Bandwidth Constraints • normal priority CTc bandwidth constraints BCck on link k: • set in proportion to forecast/measured traffic load bandwidth TRAF_LOAD_BWck • PROPORTIONAL_BWck = TRAF_LOAD_BWck/[sum {TRAF_LOAD_BWck, c=0,MaxCT-1}] X MAX_RESERVABLE_BWk • BCck = PROPORTIONAL_BWck • high priority CTc bandwidth constraint BCck • set to multiple of proportional bandwidth • BCck = FACTOR X PROPORTIONAL_BWck (FACTOR = 2 or 3 is typical) • gives priority with some 'over-allocation' of maximum reservable bandwidth • bandwidth allocated to high priority CTs should be small fraction of total link bandwidth, maximum of 10-15% a reasonable guideline • best-effort priority CTc bandwidth constraint BCck = 0

  6. Analysis of MAR, MAM, & No-DSTE • options compared • MAR • LSPs set up with bandwidth reservation • normal priority CTs: BCck = PROPORTIONAL_BWk • high priority CTs: BCck = FACTOR X PROPORTIONAL_BWk • best-effort priority CTs: BCck = 0 • MAM • normal priority CTs: BCck = FACTOR1 X PROPORTIONAL_BWk • high priority CTs: BCck = FACTOR2 X PROPORTIONAL_BWk • best-effort priority CTs: BCck = 0 • each CT restricted to allocated bandwidth constraint BCck, as in normal operation of MAM • No-DSTE • LSPs set up without bandwidth reservation • bandwidth allocation requests admitted if bandwidth available • no queueing priority applied to any CT

  7. Analysis of MAR, MAM, & No-DSTE • full-scale 135-switch national network simulation model • 5 CTs • normal priority voice • high priority voice • normal priority data • high priority data • best-effort data • simulation comparisons for • 6X focused overload on Oakbrook • 50% general overload • single link failure (3 OC-48s) • multiple link failure (3 links with 3 OC-48, 3 OC-3, 4 OC-3, respectively) • MAM performance with different over-allocation factors

  8. Performance Comparison forMAR, MAM, & No-DSTEBandwidth Constraint Models6X Focused Overload on Oakbrook(Total Network % Lost/Delayed Traffic)

  9. Performance Comparison forMAR, MAM, & No-DSTEBandwidth Constraint Models50% General Overload(Total Network % Lost/Delayed Traffic)

  10. Performance Comparison forMAR, MAM, & No-DSTEBandwidth Constraint ModelsSingle Link Failure (3 OC-48)(Total Network % Lost/Delayed Traffic)

  11. Performance Comparison forMAR, MAM, & No-DSTEBandwidth Constraint ModelsMultiple Link Failure(3 Links with 3 OC-48, 3 OC-3, 4 OC-3, Respectively)(Total Network % Lost/Delayed Traffic)

  12. Performance Comparison forMAM Bandwidth Constraint ModelDifferent Over-allocation Factors 6X Focused Overload on Oakbrook (Total Network % Lost/Delayed Traffic)

  13. Conclusions & Next Steps • MAR bandwidth constraint model • supports greater efficiency in bandwidth sharing • provides protection of allocated bandwidth under congestion • allows bandwidth sharing in absence of congestion • by bandwidth reservation methods, robust to traffic variations • meets all requirements for BC models • works well with or without preemption • proposed next steps • last call on MAR

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