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BROADNETS 2004San José, California, USA
October 25-29, 2004
pp-Cycle Network Design with Hop -Cycle Network Design with Hop Limits and Circumference LimitsLimits and Circumference Limits
Adil Kodian, Anthony Sack, Wayne D. Grover
Department of Electrical and Computer Engineering
p-Cycle Network Design with Hop Limits and Circumference Limits – Adil Kodian, Anthony Sack, Wayne D. Grover
BROADNETS 2004 – San José, California, USA – October 25-29, 2004 Department of Electrical and Computer Engineering
Presentation Overview
• What are p-cycles?
• Hop-limited p-cycle design
• Results
• Summary
p-Cycle Network Design with Hop Limits and Circumference Limits – Adil Kodian, Anthony Sack, Wayne D. Grover
BROADNETS 2004 – San José, California, USA – October 25-29, 2004 Department of Electrical and Computer Engineering
Presentation Overview
• What are p-cycles?
• Hop-limited p-cycle design
• Results
• Summary
p-Cycle Network Design with Hop Limits and Circumference Limits – Adil Kodian, Anthony Sack, Wayne D. Grover
BROADNETS 2004 – San José, California, USA – October 25-29, 2004 Department of Electrical and Computer Engineering
What Are p -Cycles?• A survivability mechanism for transport networks
Physical network topology – nodes (cities) with spans
(fibers) between them
Working capacity layer – individual demands are routed
between node pairs
Spare capacity layer – p-cycles are built to protect
working capacity on all spans
p-Cycle Network Design with Hop Limits and Circumference Limits – Adil Kodian, Anthony Sack, Wayne D. Grover
BROADNETS 2004 – San José, California, USA – October 25-29, 2004 Department of Electrical and Computer Engineering
How Do p -Cycles Protect Against Span Failure?
Sample p-Cycle
loopback
loopback
On-Cycle Failure
Break-in
Break-in
Straddling Span failure
p-Cycle Network Design with Hop Limits and Circumference Limits – Adil Kodian, Anthony Sack, Wayne D. Grover
BROADNETS 2004 – San José, California, USA – October 25-29, 2004 Department of Electrical and Computer Engineering
Presentation Overview
• What are p-cycles?
• Hop-limited p-cycle design
• Results
• Summary
p-Cycle Network Design with Hop Limits and Circumference Limits – Adil Kodian, Anthony Sack, Wayne D. Grover
BROADNETS 2004 – San José, California, USA – October 25-29, 2004 Department of Electrical and Computer Engineering
Why use short protection paths ?
• Simplify network design.
• Simplify network operation.
• Increase service availability.
p-Cycle Network Design with Hop Limits and Circumference Limits – Adil Kodian, Anthony Sack, Wayne D. Grover
BROADNETS 2004 – San José, California, USA – October 25-29, 2004 Department of Electrical and Computer Engineering
Path Length Constraints in Network Design
• Commonly used techniques to limit path length:
In mesh network design: limit the length of the longest route in the eligible route set Length <= H (Hop Limit)
In p-cycle network design: limit the circumference of the longest cycle in the eligible cycle set Length <= C (Circ. Limit)
Note: C = H +1
Straddling Span - Prot path length =
4
On-cycle Span - Prot path length = 7
Protection path length limit = 4
p-Cycle Network Design with Hop Limits and Circumference Limits – Adil Kodian, Anthony Sack, Wayne D. Grover
BROADNETS 2004 – San José, California, USA – October 25-29, 2004 Department of Electrical and Computer Engineering
Motivating Example
Initial Scenario
• All protection path lengths should be 4 hops (or less)
• Working capacities to be protected are as shown
1
1
1 1 1
2
1
12
1
Solution 1 (Hamiltonian p-cycle)
• No hop or circumference limits
• Only 8 units of spare capacity
• But some protection paths are longer than 4 (too long)
1
p-Cycle Network Design with Hop Limits and Circumference Limits – Adil Kodian, Anthony Sack, Wayne D. Grover
BROADNETS 2004 – San José, California, USA – October 25-29, 2004 Department of Electrical and Computer Engineering
Solution 3 (Shorter Paths)
• Corresponding hop limit of 4
• Only 18 units of spare capacity
• All protection paths are still adequate (within 4 hop limit)
1 1
1
Motivating Example
Solution 2 (Smaller Cycles)
• Circumference limit of 5
• 20 units of spare capacity
• No protection paths are too long (all within 4 hop limit)
(a)
1
1
1 1 1
2
1
12
11
2
1
p-Cycle Network Design with Hop Limits and Circumference Limits – Adil Kodian, Anthony Sack, Wayne D. Grover
BROADNETS 2004 – San José, California, USA – October 25-29, 2004 Department of Electrical and Computer Engineering
Hop-limited p -Cycle Design
• New parameters defined:
,Lpix
,Rpix
p-Cycle Network Design with Hop Limits and Circumference Limits – Adil Kodian, Anthony Sack, Wayne D. Grover
BROADNETS 2004 – San José, California, USA – October 25-29, 2004 Department of Electrical and Computer Engineering
• Minimize: Total modular capacity cost (spare + working)
• Subject to (along with other standard design constraints):
Highlights of ILP Design Model
,L ,L ,R ,Rp p p pi i i i i
p
x n x n w
P
Place enough cycles, considering each side separately, to protect all working units.
,Lp pin n,Rp p
in n
Number of copies of p-cycle p must be the maximum number required by any one failure, on either the L or R side of the p-cycle.
p-Cycle Network Design with Hop Limits and Circumference Limits – Adil Kodian, Anthony Sack, Wayne D. Grover
BROADNETS 2004 – San José, California, USA – October 25-29, 2004 Department of Electrical and Computer Engineering
Presentation Overview
• What are p-cycles?
• Hop-limited p-cycle design
• Results
• Summary
p-Cycle Network Design with Hop Limits and Circumference Limits – Adil Kodian, Anthony Sack, Wayne D. Grover
BROADNETS 2004 – San José, California, USA – October 25-29, 2004 Department of Electrical and Computer Engineering
Test Networks
(a) (b)
13n23s (501 cycles)
15n26s1 (871 cycles)
12n19s (127 cycles)
NSFNET (139 cycles)
p-Cycle Network Design with Hop Limits and Circumference Limits – Adil Kodian, Anthony Sack, Wayne D. Grover
BROADNETS 2004 – San José, California, USA – October 25-29, 2004 Department of Electrical and Computer Engineering
Results
5000
10000
15000
20000
25000
30000
3 4 5 6 7 8 9 10 11 12 U
Hop Limit
Dis
tan
ce-w
eig
hte
d C
apac
ity
Co
st
15n26s1 p-Cycles (Hop-limited model)
15n26s1 Mesh
13n23s p-Cycles (Hop-limited model)
13n23s Mesh
12n19s p-Cycles (Hop-limited model)
12n19s Mesh
NSFNET p-Cycles (Hop-limited model)
NSFNET Mesh
5000
10000
15000
20000
25000
30000
3 4 5 6 7 8 9 10 11 12 U
Hop Limit
Dis
tan
ce-w
eig
hte
d C
apac
ity
Co
st
15n26s1 p-Cycles (Hop-limited model)
15n26s1 Mesh
13n23s p-Cycles (Hop-limited model)
13n23s Mesh
12n19s p-Cycles (Hop-limited model)
12n19s Mesh
NSFNET p-Cycles (Hop-limited model)
NSFNET Mesh
• Threshold hop limit effect
p-Cycle Network Design with Hop Limits and Circumference Limits – Adil Kodian, Anthony Sack, Wayne D. Grover
BROADNETS 2004 – San José, California, USA – October 25-29, 2004 Department of Electrical and Computer Engineering
Results
5000
10000
15000
20000
25000
30000
3 4 5 6 7 8 9 10 11 12 U
Hop Limit
Dis
tan
ce-w
eig
hte
d C
apac
ity
Co
st
15n26s1 p-Cycles (Hop-limited model)
15n26s1 Mesh
13n23s p-Cycles (Hop-limited model)
13n23s Mesh
12n19s p-Cycles (Hop-limited model)
12n19s Mesh
NSFNET p-Cycles (Hop-limited model)
NSFNET Mesh
5000
10000
15000
20000
25000
30000
3 4 5 6 7 8 9 10 11 12 U
Hop Limit
Dis
tan
ce-w
eig
hte
d C
apac
ity
Co
st
15n26s1 p-Cycles (Hop-limited model)
15n26s1 Mesh
13n23s p-Cycles (Hop-limited model)
13n23s Mesh
12n19s p-Cycles (Hop-limited model)
12n19s Mesh
NSFNET p-Cycles (Hop-limited model)
NSFNET Mesh
• Exact comparison of mesh and p-cycle network design
p-Cycle Network Design with Hop Limits and Circumference Limits – Adil Kodian, Anthony Sack, Wayne D. Grover
BROADNETS 2004 – San José, California, USA – October 25-29, 2004 Department of Electrical and Computer Engineering
0
500
1000
1500
2000
2500
3000
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Hop Limits
Nu
mb
er o
f C
han
nel
s
Span-Restorable Mesh
C-Limited
H-Limited
Results
• Non-joint hop and circumference limited designs
• p-Cycle threshold occurs about 3 or 4 hops higher than for the corresponding mesh
•C and H limited designs perform equally well
p-Cycle Network Design with Hop Limits and Circumference Limits – Adil Kodian, Anthony Sack, Wayne D. Grover
BROADNETS 2004 – San José, California, USA – October 25-29, 2004 Department of Electrical and Computer Engineering
Results
• Actual path lengths in hop and circumference limited designs
0
50
100
150
200
250
300
350
400
450
500
2 3 4 5 6
Hop Length
Nu
mb
er o
f P
rote
ctio
n P
ath
s
Circumference Limited Path Length Limited
•Relatively lower number of long paths
p-Cycle Network Design with Hop Limits and Circumference Limits – Adil Kodian, Anthony Sack, Wayne D. Grover
BROADNETS 2004 – San José, California, USA – October 25-29, 2004 Department of Electrical and Computer Engineering
Results
• Bi-criteria objective function – reduces average path length
0
200
400
600
800
1000
1200
1400
1600
2 3 4 5 6
Hop Length
Num
ber of P
rote
ctio
n P
ath
s
Circumference Limited Path Length Limited Path Length Limited w / Bi-Criteria Objective
•Engineered for lower number of long paths
p-Cycle Network Design with Hop Limits and Circumference Limits – Adil Kodian, Anthony Sack, Wayne D. Grover
BROADNETS 2004 – San José, California, USA – October 25-29, 2004 Department of Electrical and Computer Engineering
Presentation Overview
• What are p-cycles?
• Hop-limited p-cycle design
• Results
• Summary
p-Cycle Network Design with Hop Limits and Circumference Limits – Adil Kodian, Anthony Sack, Wayne D. Grover
BROADNETS 2004 – San José, California, USA – October 25-29, 2004 Department of Electrical and Computer Engineering
Summary
• Circumference limiting is an accurate and simple surrogate for true hop-limited p-cycle designs.
• p-Cycles exhibit a threshold hop limit effect (like span restorable mesh) – but the threshold hop limit is higher than the corresponding mesh design.
• Above the threshold, p-cycle and mesh networks are equally efficient.
• Below the threshold, p-cycle capacity cost rises faster than in the corresponding mesh design.