An Analytical Approach for the Two-Tier Resource Management

Model IPS-MOME 2005 14-15 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

1999 - 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

BB

BB

BB

BB

BBDiffserv Diffserv

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, 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

BBB

IRB

Domain BBBA

ERA

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 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

B B 2

T r a n s it D o m a in

E R 21

E R 22

E R N1

I R 2

B B 1

S o u r c e D o m a in

E R 1F lo w s α i

j

B B 4I R 4

D e s t in a t io n D o m a in

B B 3

I R 3

i

D e s t in a t io n D o m a in

B B 2

T r a n s it D o m a in

E R 21

E R 22

E R N1

I R 2

B B 1

S o u r c e D o m a in

E R 1F lo w s α i

j

B B 4I R 4

D e s t in a t io n D o m a in

B B 3

I R 3

i

B B 2

T r a n s it D o m a in

E R 21

E R 22

E R N1

I R 2

B B 2B B 2

T r a n s it D o m a in

E R 21

E R 22

E R N1

I R 2

B B 1

S o u r c e D o m a in

E R 1F lo w s α i

j

B B 1B B 1

S o u r c e D o m a in

E R 1F lo w s α i

j

B B 4I R 4

D e s t in a t io n D o m a in

B B 4B B 4I R 4

D e s t in a t io n D o m a in

B B 3

I R 3

B B 3B B 3

I R 3

i

D e s t in a t io n D o m a in

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

- αiF+1 is the surplus of bandwidth requested

in the source domain

B B 2

T r a n s it D o m a in

E R 21

E R 22

E R N1

I R 2

B B 1

S o u r c e D o m a in

E R 1F lo w s α i

j

B B 4I R 4

D e s t in a t io n D o m a in

B B 3

I R 3

i

D e s t in a t io n D o m a in

B B 2

T r a n s it D o m a in

E R 21

E R 22

E R N1

I R 2

B B 1

S o u r c e D o m a in

E R 1F lo w s α i

j

B B 4I R 4

D e s t in a t io n D o m a in

B B 3

I R 3

i

B B 2

T r a n s it D o m a in

E R 21

E R 22

E R N1

I R 2

B B 2B B 2

T r a n s it D o m a in

E R 21

E R 22

E R N1

I R 2

B B 1

S o u r c e D o m a in

E R 1F lo w s α i

j

B B 1B B 1

S o u r c e D o m a in

E R 1F lo w s α i

j

B B 4I R 4

D e s t in a t io n D o m a in

B B 4B B 4I R 4

D e s t in a t io n D o m a in

B B 3

I R 3

B B 3B B 3

I R 3

i

D e s t in a t io n D o m a in

The Analytical Model (4)- C1,..., CN are the capacities of the

paths IR2-ER21, ..., IR2-ERN

1

- λ1, ..., λN 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

B B 2

T r a n s it D o m a in

E R 21

E R 22

E R N1

I R 2

B B 1

S o u r c e D o m a in

E R 1F lo w s α i

j

B B 4I R 4

D e s t in a t io n D o m a in

B B 3

I R 3

i

D e s t in a t io n D o m a in

B B 2

T r a n s it D o m a in

E R 21

E R 22

E R N1

I R 2

B B 1

S o u r c e D o m a in

E R 1F lo w s α i

j

B B 4I R 4

D e s t in a t io n D o m a in

B B 3

I R 3

i

B B 2

T r a n s it D o m a in

E R 21

E R 22

E R N1

I R 2

B B 2B B 2

T r a n s it D o m a in

E R 21

E R 22

E R N1

I R 2

B B 1

S o u r c e D o m a in

E R 1F lo w s α i

j

B B 1B B 1

S o u r c e D o m a in

E R 1F lo w s α i

j

B B 4I R 4

D e s t in a t io n D o m a in

B B 4B B 4I R 4

D e s t in a t io n D o m a in

B B 3

I R 3

B B 3B B 3

I R 3

i

D e s t in a t io n D o m a in

The Analytical Model (5)• Our model is described by the non-linear system in μ1, ..., μN, I,

0...;0...1

1...,1...

1,1

max

11

..............................

11

1

11

1

1

11

NN

NN

iF

N

NN

LwI

L

rCI

L

rCI

Reduced to linear system in

I, 1/μ1, ..., 1/μN

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

LLw

L

rC

iF

jjj

1,max

L

rC

ILw

Niii

F

11,

1max 1

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