An Analytical Approach for the Two-Tier Resource Management Model IPS-MOME March 2004 Y. Rebahi

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

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

Introduction (2) Routes are pre-configured Routes are adjusted to the topology and policy changes

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 K. Nichols, et Al, “A Two-bit Differentiated Services Architecture for the Internet”, RFC 2638, July 1999

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 BB Diffserv

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, ER A informs BB A, which requests from BB B an eventual increase of resource allocation of the traffic crossing domain A towards domain B BB B checks the available resources in its domain with IR B. If the answer is positive, BB B will inform BB A and then the resource allocation agreement is reshaped BB B IR B Domain B BB A ER A Domain A

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

The Analytical Model (2) For simplicity, our model uses only one transit domain Topology - One Egress Router in the source domain ER 1 - One Ingress Router in the transit domain IR 2 - The flows exiting the source domain are aggregated when traversing this domain - N Egress Routers ER 1,..., ER N are used in the transit domain

The Analytical Model (3) Notations - L is the predefined amount of bandwidth of the traffic agreed on between the source and the transit domain - ω is a value close to 1 - ω. 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 - α i F+1 is the surplus of bandwidth requested in the source domain

The Analytical Model (4) -C 1,..., C N are the capacities of the paths IR 2 -ER 2 1,..., IR 2 -ER N 1 -λ 1,..., λ N are the used proportions for the bandwidth distribution in the transit domain -μ 1,..., μ N are the proportions to be used for the distribution of the bandwidth surplus in the transit domain

The Analytical Model (5) Our model is described by the non-linear system in μ 1,..., μ N, I, Reduced to linear system in I, 1/ μ 1,..., 1/μ N

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

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