Traffic Grooming in WDM Networks

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Traffic Grooming in WDM Networks
Kevin Su University of Texas at San Antonio
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WDM Technology

• 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.
• Each piece of equipment which sends an optical
  signal has an illusion that it has its own fiber.
• 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, OC-192, today expected to
  grow to 40Gb/s, OC-768, soon)

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WDM Technology

• SONET Add/Drop Multiplexer (SADM) can be used to
  aggregate lower rate stream from different
  end-users into a single high-rate SONET stream in
  Time Division Multiplexing (TDM) fashion.
• Optical cross connect (OXC) is a network element
  that perform wavelength switching and/or
  wavelength conversion.
• Wavelength switching switch traffic from a
  wavelength of an input fiber link to the same
  wavelength of any outgoing fiber link.
• Wavelength conversion traffic from a wavelength
  of an input fiber link can be switched to any
  wavelength in the outgoing fiber link.
• Lightpath a traffic route that using same or
  different wavelength without optical-electronic-op
  tical conversion in WDM optical networks.

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Wavelength Switching / Conversion
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Traffic Grooming

• Motivation
• Gap between capacity of a WDM Channel (OC-48, or
  OC-192, or OC-768) and bandwidth requirement of a
  typical connection request (e.g. STS-1, OC-3,
  OC-12 etc)
• In order to use network efficiently, low-speed
  traffic streams need to be efficiently
  multiplexed, or groomed onto high-speed
  lightpaths
• Problem Formulation
• Given a network configuration and a set of
  connection requests with different bandwidth
  granularities, such as OC-12.
• Determine how to set up lightpaths to satisfy the
  connection requests.
• Category
• Static Case (static traffic) Set of connection
  requests can all be given in advance
• Dynamic Case (dynamic traffic) connection
  requests are given one at a time

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Network Topology

• SONET Ring
• SONET ring network is currently the most
  widely deployed optical network infrastructure.
• Mesh Network
• Due to the increase of Internet traffic,
  more WDM networks would be deployed in general
  mesh topology to meet this demands. Thus more
  work needs to be done in the mesh networks
  grooming problem.

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Traffic Grooming Example
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Traffic Grooming Example
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Traffic Grooming Example
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Modeling Traffic Grooming Problem

• Static Case
• The problem is usually formulated as an Integer
  Linear Program (ILP) problem and get different
  optimal solution according to different goals.
  Unfortunately, for large networks it is
  computationally infeasible to solve the ILP
  problem. Therefore, many heuristic algorithms
  were proposed.
• Dynamic Case
• Usually problem is divided into 4 sub-problems.
  Using different algorithms to solve different
  sub-problems. Recently one integrated algorithm
  was proposed to solve the 4 problems altogether.

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Static Case (ILP)
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Subproblems in Traffic Grooming

• (1) Determine the virtual topology that consists
  of lightpaths
• NP-hard
• (2) Routing the lightpaths over the physical
  topology
• NP-hard
• (3) Performs wavelength assignment to the
  lightpaths
• (2) and (3) together are RWA problem
• (4) Routing the traffic on the virtual topology.

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Future Challenges

• Grooming with Protection
• Provide two routing path for each
  connection requests, one is primary traffic
  stream path (TSP), the other is link-disjoint
  backup traffic stream path (TSP). 11 protection
  (dedicated),
• 1 m (shared backup TSP).
• Multicast Traffic Grooming
• The objective is to construct multicast
  trees (or light-trees) that optically carry the
  multicast traffic from the source to the
  destination nodes, which will reduce the cost of
  network.

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Protection
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Multicast Traffic Grooming
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Multicast Traffic Grooming

• Session 1 Source A Destination B, C
  Traffic demand 1 unit
• Session 2 Source B Destination C Traffic
  demand 2 unit
• Session 3 Source A Destination F Traffic
  demand 1 unit
• Routing the demands using an SMT requires 7 ADMs
  and two wavelengths, as shown in Figure 1.
  However,
• using the routing shown in Figure 2 costs just 6
  ADMs and one wavelength

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References

• Ruda Dutta and George N. Rouskas, Traffic
  Grooming in WDM Networks Past and Future, IEEE
  Network 2002
• Sashisekaran Thiagarajan, Arun K.Somani Traffic
  Grooming for Survivable WDM Mesh Networks
  OptiComm 2001
• Ahmed E. Kamal, Raza Ul-Mustafa, Multicast
  Traffic Grooming in WDM Networks, OptiComm 2003
• Hui Zang, Canhui Ou, Biswanath Mukherjee
  Path-Protection Routing and Wavelength Assignment
  (RWA) in WDM Mesh Networks Under Duct-Layer
  Constraints, IEEE/ACM Transactions on Networking,
  April 2003