Network Survivability Against Region FailureSignal Processing, Communications and Computing (ICSPCC), 2011 IEEE

International Conference on

Ran Li , Xiaoliang Wang , Xiaohong Jiang

Adviser: Frank , Yeong - Sung Lin Present by Jason Chang

Agenda

INTRODUCTION BackgroundRegion failure model and SPM routing

REGION-DISJOINT MULTI-PATH ROUTINGOptimization of Traffic ThroughputComplexity Analysis

SPM AGAINST SINGLE REGION FAILUREProblem Formulation

NETWORK UPGRADE PROBLEM

NUMERICAL RESULT

CONCLUSION

Agenda

INTRODUCTION BackgroundRegion failure model and SPM routing

REGION-DISJOINT MULTI-PATH ROUTINGOptimization of Traffic ThroughputComplexity Analysis

SPM AGAINST SINGLE REGION FAILUREProblem Formulation

NETWORK UPGRADE PROBLEM

NUMERICAL RESULT

CONCLUSION

Background

Communication has been a tremendous success with significant impact on our daily life.

people are increasingly relying on large-scale communicationslarge-scale computer networks are now facing more and more potential threats

It is essential for the large-scale computer networks to have the capability of guaranteeing mission-critical information change.

Background

Previously work around network survivability mainly focuses on single link or node failure in a logical topology.

link cut and router software/hardware error are the main failure modes

Network scale is increasing and network robustness is becoming more stringent , the multiple simultaneous failure scenarios have been address in some recent research works.

technique of providing protection if a second link fails before recovering from the first link failureresilient routing schemesSRLG(shared risk link group)Based on graph-theoretical optimization technique , the strategies for protection and restoration of optical paths against SLRG failures

Background

In real networks some disruptive events which may simultaneously affect multiple network components confined to a specific area are so called region failure.

Region failures may lead to catastrophic data loss and may take a long time to be recovered.

Due to the fact that the network failures due to a region failure are geographically correlated , the geographical layout of network components needs to be carefully take into account in the region failure-related network survivability analysis.

Background

Intuitively , the region failure can be considered as a highly localized event where the failed nodes and links are clustered in a geographical area.

Background

In recent years , various methodologies have been proposed to evaluate the impact of region failure.

identify the most vulnerable region to a region failure in real network physical topologies , where the region failures are modeled as line-segment cuts or circular cuts arbitrarily placed on network planeanalyze network failures after randomly localized linear cutphysical connectivity logical connectivity under physical link failure

Background

The classical Menger’s theorem(i.e. the max-flow min-cut theorem) does not hold any more for region-based connectivity analysis.

Region failure model and SPM routing

The region failure is modeled as a circular disk of radius r , which centers at a network node.

Any network component intersecting with this region will be destroyed and removed from the network.

Approach to dealing with network components failure is to provide both backup path and primary path for each traffic demand.

To improve the efficiency of protection :shared backup path protection

self – protection multipath routing

For simplicity , we assume that the cost effective self-protecting multipath routing is adopted and all routing paths are known in advance.

Region failure model and SPM routing

Self-protecting multi-path routing (SPM) is based on the idea of traffic load-balance.

In IP/MPLS networks , it is possible to setup two or more working path , and the spare capacity of these working path can be applied to provide backup for each other when network failure occurs.

Region failure model and SPM routing

SPM consists of disjoint paths and the traffic is distributed over all of them according to a traffic distribution function.

Due to the fact that two of the routing path may be covered by a single region , only one of them can be applied.

Region failure model and SPM routing

Agenda

INTRODUCTION BackgroundRegion failure model and SPM routing

REGION-DISJOINT MULTI-PATH ROUTINGOptimization of Traffic ThroughputComplexity Analysis

SPM AGAINST SINGLE REGION FAILUREProblem Formulation

NETWORK UPGRADE PROBLEM

NUMERICAL RESULT

CONCLUSION

Optimization of Traffic Throughput

Notation Description

G(N,E) a network with |N| nodes and |E| links

R a finite candidate regions

e = (i,j) a link between two adjacent nodes i and j

ue the link capacity of e = (i,j)

Tsd the demand of connection requirement from node s to node d

PBsd the set of routing paths illustrated in Figure 3(b)

the path from s to d using link e

the traffic split ratio for path P , P PBsd

the traffic throughput

Optimization of Traffic Throughput

The optimization function aims at maximizing the traffic throughput：

Optimization of Traffic Throughput

Additionally , paths between a source-destination pair should be region-disjoint：

Complexity Analysis

As the number of connections is less than and the number of paths for one connection is less than the outdegree of the source node, ,the number of variable is thus bounded by .

The total number of equations in the constraint (1) is

, while the number of equations in the constraint (2) is .

N(N 1)

N 1Psd 2( 1)N N

N(N 1)

(N 1)E N

Agenda

INTRODUCTION BackgroundRegion failure model and SPM routing

REGION-DISJOINT MULTI-PATH ROUTINGOptimization of Traffic ThroughputComplexity Analysis

SPM AGAINST SINGLE REGION FAILUREProblem Formulation

NETWORK UPGRADE PROBLEM

NUMERICAL RESULT

CONCLUSION

The SPM consist of multiple paths over which the traffic is distributed according to a load balancing function.

The backup capacities may be shared by different flows in various failure scenario.

Our target is maximize network throughput under any single region failure.

Problem Formulation

Problem Formulation

Notation Description

G(N,E) a network with |N| nodes and |E| links

R a finite candidate regions

e = (i,j) a link between two adjacent nodes i and j

ue the link capacity of e = (i,j)

PBsd the set of routing paths illustrated in Figure 3(b)

the traffic split ratio for path P , P PBsd

link e is covered by region rk , rk R

r0 the normal scenario (no failure)

R’ R r0

k

erf

We use as the traffic spilt ration of path P for demand from s to d in case of a region failure

The throughput of this demand can be expressed as:

Problem Formulation

P ( )sd kr

R'kr

Problem Formulation

The function of LP model can then be expressed as:

Agenda

INTRODUCTION BackgroundRegion failure model and SPM routing

REGION-DISJOINT MULTI-PATH ROUTINGOptimization of Traffic ThroughputComplexity Analysis

SPM AGAINST SINGLE REGION FAILUREProblem Formulation

NETWORK UPGRADE PROBLEM

NUMERICAL RESULT

CONCLUSION

For a network can not accommodate all the traffic with regard to any single region failure , we may need to upgrade the network by providing additional link capacity.

To realize a minimum capacity for a upgrade for a given network such that it can serve all traffic matrix in case of any single region failure.

Network Upgrade Problem

We denote the additional capacity require by link as , then we have :

Network Upgrade Problem

e( )c e

Agenda

INTRODUCTION BackgroundRegion failure model and SPM routing

REGION-DISJOINT MULTI-PATH ROUTINGOptimization of Traffic ThroughputComplexity Analysis

SPM AGAINST SINGLE REGION FAILUREProblem Formulation

NETWORK UPGRADE PROBLEM

NUMERICAL RESULT

CONCLUSION

Two real network topologies are adopted in our simulation , the USA network and the NFSNET network.

Set capacity as 1 for all the links.

The demands are generated randomly with equal probability between any pair of nodes.

Bandwidth requirements are over provided in the interval of 0 – 50 with uniform distribution.

Numerical Result

USA network :26 nodes

41 links

Max distance : 187

Average distance : 111

Minimum distance : 66

Numerical Result

NFSNET network :79 nodes

109 links

Max distance : 154

Average distance : 175

Minimum distance : 36

Numerical Result

Numerical Result

The throughput decreases as the region size increase :

The worst region failure in the network that results in the maximum throughput degradation : (in USA network)

Numerical Result

The worst region failure in the network that results in the maximum throughput degradation : (in NFSNET network)

Numerical Result

Agenda

INTRODUCTION BackgroundRegion failure model and SPM routing

REGION-DISJOINT MULTI-PATH ROUTINGOptimization of Traffic ThroughputComplexity Analysis

SPM AGAINST SINGLE REGION FAILUREProblem Formulation

NETWORK UPGRADE PROBLEM

NUMERICAL RESULT

CONCLUSION

Evaluate the impact of region failures on network survivability.

Apply the region – disjoint self – protecting multi – path routing.

The existing networks are actually very vulnerable to the region failure.

It is critical to design a fault – tolerant network against region failure.

Conclusion

Thanks for your listening