An Analytical Approach for the TwoTier Resource Management Model

1
An Analytical Approach for the Two-Tier
Resource Management Model

• IPS-MOME 2005
• 14-15 March 2004
• Y. Rebahi

2
Outline

• Introduction
• The Two-Tier architecture for resource allocation
  
• - The Bandwidth Broker
• The analytical model for this architecture
• Future work

3
Introduction

• Interconnections between a lot of various
  administrative domains
• Each domain takes care of its internal resource
  allocation (in an independent way) as well as its
  relations with its neighbours
• Predefined bilateral agreements between
  neighboring domains
• The end to end data delivery is provided by
  concatenating the forwarding activities for the
  the different administrative domains

4
Introduction (2)

• Routes are pre-configured
• Routes are adjusted to the topology and policy
  changes

5
The Two-Tier Architecture

• Scalable resource management
• Two levels of resource allocation
• - intra-domain allocation (each
  administrative domain is free to choose whatever
  resource allocation mechanism that seems
  suitable)
• - inter-domain allocation (achieved through
  bilateral agreements)
• - intra and inter domain resource
  management are independent
• - no conflict between the two resource
  management levels
• End to end QoS is achieved through the
  concatenation of the bilateral agreements
• Resource allocation is adjusted according to the
  demand and the topology changes
• References
• - A. Terzis, et Al, A Two-Tier Resource
  Management Model for The Internet, Global
  Internet, Dec 1999
• - K. Nichols, et Al, A Two-bit
  Differentiated Services Architecture for the
  Internet, RFC 2638, July 1999

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The Two-Tier architecture (2)

• The tow-tier resource allocation model is
  achieved through the Bandwidth Broker (BB) which
  is,
• - A logical entity residing in each domain
• - Manages internal demands and resource
  allocation according to the domains policies
• - Maintains bilateral agreements with
  neighboring domains

7
The Two-Tier architecture (3)

• A predefined level of resource allocation exists
  between the domains A and B
• When the resource demand in domain A exeeds a
  certain threshold, ERA informs BBA, which
  requests from BBB an eventual increase of
  resource allocation of the traffic crossing
  domain A towards domain B
• BBB checks the available resources in its domain
  with IRB. If the answer is positive, BBB will
  inform BBA and then the resource allocation
  agreement is reshaped

8
The Analytical Model

• To analyse in depth the two-tier resource
  management scheme and predict its performance
• To prove the existence of rigourous and stable
  solutions
• to estimate the used parameters in order to help
  in detecting limitations and handling future
  optimisations

9
The Analytical Model (2)

• For simplicity , our model uses only one transit
  domain
• Topology
• - One Egress Router in the source domain
  ER1
• - One Ingress Router in the transit domain
  IR2
• - The flows exiting the source domain are
  aggregated when traversing this domain
• - N Egress Routers ER1,..., ERN are used in
  the transit domain

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The Analytical Model (3)

• Notations
• - L is the predefined amount of bandwidth
  of the traffic agreed on between the source and
  the transit domain
• - ? is a value close to 1
• - ?. L is the bandwidth threshold that when
  exeeded, the resource allocation between the
  domains has to be re-negociated
• - r is the current bandwidth request in the
  source domain
• - I is a value greater than 1
• - I.r is the new bandwidth amount requested
  during the re-negociation
• - aiF1 is the surplus of bandwidth requested
  in the source domain

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The Analytical Model (4)

• C1,..., CN are the capacities of the paths
  IR2-ER21, ..., IR2-ERN1
• ?1, ..., ?N are the used proportions for the
  bandwidth distribution in the transit domain
• µ1, ..., µN are the proportions to be used for
  the distribution of the bandwidth surplus in the
  transit domain

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The Analytical Model (5)

• Our model is described by the non-linear system
  in µ1, ..., µN, I,

Reduced to linear system in I, 1/µ1, ..., 1/µN
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The Analytical Model (6)

• Using the Fourier-Motzkin Elimination procedure,
• The bandwidth increase request satisfies this
  double-estimate below which provides a range of
  values for which the resource allocation is
  correctly feasible. This will help avoiding
  considerable gaps between the levels of allocated
  and current resources. If i is less than lower
  bound, the bandwidth reservation can not satisfy
  the bandwidth demand. If I greater than the upper
  bound, the bandwidth reservation is higher than
  the real need

j 1,..., N
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Future Work

• Consider more than one transit domain
• Provide simulation results for validating our
  model
• Compare between the results obtained from our
  analytical model and the ones from existing
  simulations