QUALIFYING CHARACTERISTICS OF LINK SHUTDOWN METHOD WTC 2012 - - PowerPoint PPT Presentation

QUALIFYING CHARACTERISTICS OF LINK SHUTDOWN METHOD

WTC 2012 Conference 4-7 March 2012 Miyazaki, JAPAN Simon Tembo, and Ken-ichi Yukimatsu Department of Computer Science and Engineering, Graduate School of Engineering and Resource Science, AKITA UNIVERSITY Shohei Kamamura, Takashi Miyamura and Kohei Shiomoto NTT Network Service Systems Laboratories, NTT CORPORATION

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INTRODUCTION

Cause of IP Network Failures

 Shutting down a link due to routine maintenance is considered as a planned network failure.

 Currently, ISPs use a graceful link shutdown method by first setting up the Interior Gateway Protocol (IGP) link metric to MAX_METRIC - 1 and then shutdown the link.  The link metric of a link can be increased to a larger metric by progressively increasing the metric

• f a link by 1, until the target metric

is reached  such that it cannot carry traffic anymore at which point the link can then be safely shutdown.  We present that a Pythagorean Triple Metric Sequence can be used to shutdown a link during routine maintenance.

20% 80%

Cause of IP Network Failures

Due to Routine Maintenance Due to Unplanned Failures

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1 m m



 

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Using Pythagorean Triple Properties to Compute MAX_METRIC – 1

• 1. Using Euclid Formula:

 Pythagorean triples from any two positive integers m and n; m>n.  In terms of sequence we have : {a, b, c}  If n = 1, the triples are  Graceful Link Shutdown Method: MAX_METRIC – 1

• Where m=256; n=1

2 2

m n  2mn

2 2

m n 

2 2 2

256 1 65,535 a m n     

2 512 b mn  

2 2 2

256 1 65,537 c m n     

2 2

{ 1, 2 , 1 } a m b m c m      

2 2 2 2

{ , 2 , } a m n b mn c m n      

16 2

_ 1 2 1 256 1 65,535 a MAX METRIC        

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Using Pythagorean Triple Properties and Genealogical Tree to Compute Pythagorean Triple Metric Sequence - Starting from {3,4,5}

m,n 2m-n, m 2m+n, m m+2n, n {a,b,c} {a-2b+2c, 2a-b+2c, 2a-2b+3c} {a+2b+2c, 2a+b+2c, 2a+2b+3c} {-a+2b+2c, -2a+b+2c, -2a+2b+3c} 2,1 3,2 4,3 8,3 7,2 5,2 8,5 12,5 9,2 4,1 7,4 9,4 6,1 {3,4,5} {5,12,13} {7,24,25} {55,48,73} {45,28,53} {21,20,29} {39,80,89} {119,120,169} {77,36,85} {15,8,17} {33,56,65} {65,72,97} {35,12,37} c a b

2 2 2 2

{ , 2 , } a m n b mn c m n      

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Using the Pythagorean Triple Metric Sequence Method we Compute Target Metrics for Link Shutdown

 If {a, b, c} is a Pythagorean triple, so is {ka, kb, kc} for any positive integer k, and that the smallest Pythagorean Triple is {3, 4, 5} when k=1.  The {3, 4, 5} triple and its multiples {3n, 4n, 5n} are the only Pythagorean triple that are in arithmetic progression and consecutively incrementing.  We use the Pythagorean Triple Sequence {3n, 4n, 5n} to determine a sequence

• f link metrics as target metrics to use to shut down a link.

2 1 4 3 n n n n n n

n PRIMITIVE TARGET METRIC 1 1 x 3, 4, 5 3, 4, 5 2 2 x 3, 4, 5 6, 8, 10 3 3 x 3, 4, 5 9, 12, 15 4 4 x 3, 4, 5 12, 16, 20 5 5 x 3, 4, 5 15, 20, 25 … … … n n x 3, 4, 5 3n, 4n, 5n

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Result of using Pythagorean Triple to Shut Down a Link Result of using Pythagorean Triple to Shut Down Two Links

When we shutdown links 1-2/2-1 traffic destined for node 2 routing is:

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 lk 0-1 lk 0-3 lk 1-0 lk 1-2 lk 1-4 lk 2-1 lk 2-4 lk 3-0 lk 3-4 lk 4-1 lk 4-2 lk 4-3 UTILIZATION All Links @n All Links @n; Except Links 1-2 & 2-1@5n; & Links 1-4 & 4-1 @4n

We are also able to shutdown two links (e.g. 1-2/2-1 and 1-4/4-1) using our Method.

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1 2 4 3 2 1 3 n n n 5n n n 4

Link Cost Routing

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 lk 0-1 lk 0-3 lk 1-0 lk 1-2 lk 1-4 lk 2-1 lk 2-4 lk 3-0 lk 3-4 lk 4-1 lk 4-2 lk 4-3 UTILIZATION All Links @n All Links @n; Except Links 1-2 & 2-1@5n

2 1 3 4n n n 5n n n 4

Link Cost Routing

Links that can be shut down when link cost reaches the link metric of {3n, 4n, 5n} Links that can be shut down ONLY when link cost reaches the link metric of {4n, 5n}

0.02 0.04 0.06 0.08 0.1 n 2n 3n 4n 5n LINK METRIC SEQUENCE 0.084314573 0.042157287 0.084314573 0.042157287 UTILIZATION lk 1-2 lk 2-1

0.05 0.1 0.15 0.2 0.25 0.3 n 2n 3n 4n 5n LINK METRIC SEQUENCE 0.268273642 0.009263101 0.0061754 0.268273642 0.009263101 0.0061754 UTILIZATION lk 0-3 lk 3-0

During our experiments each link was configured to {n, 2n, 3n, 4n, 5n} link metric; Some links it is only when the link metric reached {3n, 4n, 5n} that the link utilization was zero. Whereas other links it is only when the link metric reached {4n, 5n} that the link utilization became zero.

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Our Simulation Results in Summary & Conclusion

 We have presented a link shutdown method using the Pythagorean Triple Metric Sequence that can be used to configure and shutdown a link for routine maintenance.  Thus when a link is scheduled for routine maintenance the link can be configured to one of the metric in the sequence {3n, 4n, 5n} as the target metric before shutdown.  Future work, we plan to investigate the use of other Pythagorean Triple Sequences other than the {3n, 4n, 5n}.

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50% 50%

50% of the links were shutdown when link cost reached the link metric of {3n, 4n, 5n} 50% of the links were shutdown ONLY when link metrict reached the link metric of {4n, 5n}