Transcript Document 7375154

Traffic Grooming for Survivable WDM
Networks – Shared Protection
Kevin Su
University of Texas at San Antonio
10/6/2003
Kevin Su ([email protected])
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Outline
• Introduction
• Motivation
• System Model
– Grooming Node Architecture
– Network Model
• Proposed Schemes
– Protection-at-lightpath (PAL) level
– Mixed protection-at-connection (MPAC) level
– Separated protection-at-connection (SPAC) level
• Heuristic Algorithms
• Performance Evaluation
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Introduction
• WDM: stands for wavelength division multiplexing, it is a
technology that divides the bandwidth of an optical fiber into many
non-overlapping wavelengths, so that multiple communication
channels can operate simultaneously on different wavelengths.
– Increases the transmission capacity of optical fibers.
– Allows simultaneously transmission of multiple wavelengths within a
single fiber.
– Up to 320 wavelengths per fiber; per wavelength, 10Gb/s, STS-192
(OC-192), today; expected to grow to 40Gb/s, STS-768(OC-768),
soon.
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Introduction
• Traffic Grooming: refers to problem of efficiently packing lowspeed connections onto high-capacity lightpaths to better utilize
network resourses.
– The bandwidth requirement of a typical connection request is between
STS-1 (51.84 Mb/s) and STS-192(full wavelength)
• Protection: is a proactive procedure in which spare capacity is
reserved during connection setup.
– Working path: a path that carries traffic during normal operation
– Backup path: a path over which the connection is rerouted when a
working path fails
– Single Failure (single-fiber failure, single-node failure) ---0-----0
------0---
– Dedicated Protection
– Shared Protection
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Introduction
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Motivation
• Survivable Traffic Grooming
– Efficiently utilize the network resources (traffic grooming)
– A failure of a network element can cause the failure of several
lightpaths, thereby leading to large data and revenue loss (protection)
• Static Case
• Dynamic Case
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Grooming Node Architecture
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Network Model
• A network is represented as a weighted, directed graph
G=(V, E, C, λ, P)
–
–
–
–
–
V: set of nodes
E: set of unidirectional fibers (referred to links)
C: the cost function for each link
λ: the number of wavelengths on each link
P: number of grooming ports at each node
• Connection request is represented as a quadruple <s, d, B, t h >
– s: source node
– d: destination node
– B: bandwidth requirement
– t h : holding time
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Proposed Schemes - PAL
• Protection-at-lightpath (PAL) level provides end-to-end protection
w.r.t. lightpath. Under PAL, a connection is routed through a
sequence of protected lightpath, or p-lightpath.
• A p-lightpath has a lightpath as working path and link-disjoint path
as backup path
• Working path consumes a grooming-add port at the source node and
a grooming-drop port at the destination node
• Backup path doesn’t consume any grooming port and wavelengths
along a backup path are only reserved
• When working path fails, backup path is set up as a lightpath by
utilizing the grooming ports previously used by the working path
• Two p-lightpaths can share wavelengths along common backup
links if their working paths are link-disjoint.
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Proposed Schemes - PAL
•
•
•
•
Initial network configuration
Edge represents bidirectional fiber, each fiber has 2 wavelengths
Wavelength capacity STS-192, every node has 3 grooming ports
c1<0,2,STS-12, t1>; c2 < 0,3,STS-3, t2>; c3 <4,3,STS-48, t3>
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Proposed Schemes - PAL
• After provisioning c1
• c1<0,2,STS-12, t1>; c2 < 0,3,STS-3, t2>; c3 <4,3,STS-48, t3>
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Proposed Schemes - PAL
• After provisioning c2
• c1<0,2,STS-12, t1>; c2 < 0,3,STS-3, t2>; c3 <4,3,STS-48, t3>
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Proposed Schemes - PAL
• After provisioning c3
• c1<0,2,STS-12, t1>; c2 < 0,3,STS-3, t2>; c3 <4,3,STS-48, t3>
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Proposed Schemes – MPAC
• Mixed Protection-at-Connection (MPAC) level provides end-to-end
protection w.r.t. connection. Under MPAC, a connection is routed
via link-disjoint working path and backup path, each of which
traverses a sequence of lightpaths.
• A lightpath traversed by a working path utilizes a portion of its
capacity to carry traffic during normal operation
• A lightpath traversed by a backup path reserves part of its capacity
for that backup path
• “Mixed” means that capacity of one wavelength can be utilized by
both working paths and backup paths.
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Proposed Schemes - MPAC
• After provisioning c1
• c1<0,2,STS-12, t1>; c2 < 0,3,STS-3, t2>; c3 <4,3,STS-48, t3>
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Proposed Schemes - MPAC
• After provisioning c2
• c1<0,2,STS-12, t1>; c2 < 0,3,STS-3, t2>; c3 <4,3,STS-48, t3>
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Proposed Schemes - MPAC
• After provisioning c3
• c1<0,2,STS-12, t1>; c2 < 0,3,STS-3, t2>; c3 <4,3,STS-48, t3>
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Proposed Schemes – SPAC
• Separated Protection-at-Connection (MPAC) level provides end-toend protection w.r.t. connection. Under SPAL, a connection is routed
via link-disjoint working path and backup path.
• A working path traverses a sequence of lightpath.
• A backup path traverses a sequence of links, each of which has
judiciously reserved a number of wavelengths as backup resourses
• “Separated” means that the capacity of a wavelength can be utilized
by either working paths or backup paths, but not both.
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Proposed Schemes - SPAC
• After provisioning c1
• c1<0,2,STS-12, t1>; c2 < 0,3,STS-3, t2>; c3 <4,3,STS-48, t3>
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Proposed Schemes - SPAC
• After provisioning c2
• c1<0,2,STS-12, t1>; c2 < 0,3,STS-3, t2>; c3 <4,3,STS-48, t3>
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Proposed Schemes - SPAC
• After provisioning c3
• c1<0,2,STS-12, t1>; c2 < 0,3,STS-3, t2>; c3 <4,3,STS-48, t3>
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Proposed Schemes
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Heuristic Algorithm
• It is NP-complete to provision a connection request with shared
protection.
• The Author proposed heuristic for MPAC, SPAC, PAL
• MPAC
– Backup-sharing measuring
Every lightpath is associated with a conflict set to identify the sharing
potential between paths.
conflict set vl for lightpath l can be represented as an integer set
{ vle | e  E ,0  vle  STS  192} where vle represents the amount of traffic that will
be rerouted on lightpath l when link e fails. The amount of backup capacity
*
{vle }
reserved on lightpath l is thus vl  max
e
– Route computation
• Enumerates K candidate working paths
• For each candidate working path, computes a disjoint minimal-cost path as backup
path based on some cost function
• Selects the path pair of minimal cost
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Heuristic Algorithm
• SPAC (the same as MPAC except)
– Different backup-sharing measurement
– Different cost function in route computation
• PAL
– Different backup-sharing measurement
– Route computation
• Extend a stand shortest-path algorithm such that every hop along the resultant
shortest path corresponds to a p-lightpath, which can be either an exisiting plightpath or a new p-lightpath consisting of fresh wavelength links and free
grooming ports
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Performance Evaluation
•
•
•
•
•
•
•
•
Connection-arrival process is Poisson process
Connection-holding time follows a negative exponential distribution
Capacity of wavelength is STS-192
# of connection requests follows the distribution STS-1: STS-3: STS-12:
STS-48: STS-192 = 300: 20: 6: 4 :1
Load (in Erlang) is defined as connection-arrival rate times average
holding time times a connection’s average bandwidth normalized in the
unit of STS-192
Number of grooming ports is set as # of wavelengths times its nodal
degree times a scalar  ( 0    1,   1 implies that any incoming
wavelength to the W-Fabric can be dropped to the G-Fabric)
The number of alternate paths K = 2
Measurement metrics
amount of bandwidth blocked
– Bandwidth-blocking Ratio
– Resource-Efficiency Ratio
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amount of bandwidth offered
  ti

i i
 ( w , wg ) 
w  i  i  ti  wg  i  i  ti
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Network Topology
24-node example network topology
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Performance Evaluation
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Performance Evaluation
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Performance Evaluation
BBR versus network offered load
with k =1,2 and 3
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Conclusion and Future Work
• Investigate the survivable traffic-grooming problem in dynamic case
– PAL, MPAC, SPAC
– Findings:
• It is beneficial to groom working paths and backup paths separately as in
PAL and SPAC
• Separately protecting each individual connection yields the best
performance when the number of ports is suffcient
• Protecting each specific lightpath achieves the best performance when the
# of grooming ports is moderate or small
• Future work
– Considering the residual connection holding time
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References
• C. Ou, K. Zhu, H. Zang, L. H. Sahasrabuddhe, and B. Mukherjee.
“Traffic Grooming for Survivable WDM Networks – Shared
Protection”. Accepted to IEEE Journal of Selected Area in
Communication 2004.
• H. Zhu, H.Zang, K. Zhu, and B. Mukherjee, “A novel, generic graph
model for traffic grooming in heterogeneous WDM mesh networks”
IEEE/ACM Trans. Neworking, vol.11 pp.285-299, Apr. 2003
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