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Bandwidth Constraint Models for Diffserv-aware MPLS Traffic Engineering

Bandwidth Constraint Models for Diffserv-aware MPLS Traffic Engineering <draft-wlai-tewg-bcmodel-00.txt> IETF’55 TEWG Meeting Atlanta, Georgia, November 20, 2002 Wai Sum Lai AT&T Labs wlai@att.com. Bandwidth Allocation Algorithms

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Bandwidth Constraint Models for Diffserv-aware MPLS Traffic Engineering

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  1. Bandwidth Constraint Models for Diffserv-aware MPLS Traffic Engineering <draft-wlai-tewg-bcmodel-00.txt> IETF’55 TEWG Meeting Atlanta, Georgia, November 20, 2002 Wai Sum Lai AT&T Labs wlai@att.com

  2. Bandwidth Allocation Algorithms To determine if bandwidth should be granted to a new LSP from a given class of traffic. Two algorithms currently described in DSTE Requirements document: Explicit maximum allocation algorithm • Maximum allowable bandwidth usage of each class is being explicitly specified Russian doll algorithm • Specification of maximum allowable usage is being done cumulatively

  3. Class 1 Class 2 Class 3 Class 1 Classes 1 and 2 Classes 1, 2, & 3 Illustration of the Algorithms Explicit maximum allocation algorithm Russian doll algorithm Class 1 has highest priority, class 3 lowest

  4. Methodology for Comparison • Based on a Markov Chain model described in • W. S. Lai, “Traffic Engineering for MPLS,” Internet Performance and Control of Network Systems III Conference, SPIE Proceedings Vol. 4865, pp. 256-267, Boston, Massachusetts, USA, 29 July-1 August 2002. • http://www.columbia.edu/~ffl5/waisum/bcmodel.pdf • To provide uniform treatment of both Explicit Maximum Allocation and Russian Doll algorithms, and a comparison of their merits in a general setting • same model is being applied for both algorithms • only different parametric values are used for different algorithms

  5. Results of Analysis Russian doll algorithm • Allows greater sharing of bandwidth among different classes of traffic • Performs somewhat better under normal conditions • Works well when preemption is enabled Explicit maximum allocation algorithm • Provides more robust service isolation under high load • Does not depend on the use of preemption Preemption • Gives higher-priority traffic some immunity against the overloading of other classes • Results in a higher blocking/preemption for the overloaded class, when compared with a pure blocking environment

  6. Proposal Adopts the explicit maximum allocation algorithm or its variant, such as maximum allocation with reservation, as the default bandwidth constraint model Rationale • The higher degree of sharing allowed in the Russian doll algorithm causes its inability to offer robust service isolation under overload conditions. • Also, it requires use of preemption to operate well – preemption can be disabled as described in the DS-TE Requirements document. • Maximum allocation algorithms do not have these issues.

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