PCEP Requirements and Extensions for the support of Wavelength Switched Optical Networks (WSON)

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PCEP Requirements and Extensions for the support
of Wavelength Switched Optical Networks (WSON)
draft-lee-pce-WSON-routing-wavelength-01.txt
Young Lee ylee_at_huawei.com Huawei Greg
Bernstein gregb_at_grotto-networking.com Grotto
Networking
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Outline

• Applicability of PCE to WSON/RWA
• PCEP Requirements
• Summary Next Step

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Wavelength Constraints in WSON Path Computation

• The path in WSON is referred to as a lightpath.
• A lightpath may span multiple fiber links and the
  path should be assigned a wavelength for each
  link.
• Two lightpaths that share a common fiber link
  cannot be assigned the same wavelength. To
  prevent this a signaling system must block setup
  requests that could result in this condition.
• Therefore, assigning the proper wavelength on a
  lightpath is an essential requirement in the
  optical path computation process.
• In a transparent optical network, a lightpath
  must operate on the same wavelength across all
  fiber links that it traverses. This constraint is
  known as the wavelength continuity constraint.

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Illustration wavelength constraints
D
E
C
B
A
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PCEP Requirements

• PCE Computation Options
• Wavelength Assignment and Wavelength Set
  information
• Optimization Degree
• Lightpath Route Parameters
• Wavelength Selection Preference (optional)
• Timeliness Characteristics (optional)
• Duration of lightpath (optional)

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PCE Computation Options

• The following RWA computation options should be
  conveyed in the PC Request
• The request is for Wavelength Assignment (WA)
  only.
• The request is for both Routing and Wavelength
  Assignment (RWA).
• The request is for Routing (R) only.
• The request is for Routing (R) with the
  suggested/restricted wavelength set.

PC Request RP object RC bits
PCC
PCE
PC Reply RP object RC bits
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Wavelength Assignment and Wavelength Set
information

• The PCE MUST specify the wavelength assignment
  and/or wavelength set information in response to
  the wavelength assignment/wavelength set Request
  made by the PCC in the PCReq message.
• Note Wavelength assignment is the part of path
  computation in a transparent optical network that
  chooses a wavelength that meets the wavelength
  continuity constraint.

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Optimization Degree

• The PC Request Message should indicate the degree
  of optimization associated with lightpath
  computation.
• Concurrent Optimization multiple lightpaths
  requested at one time.
• Lightpath(s) and backup lightpath(s) requested at
  one time.
• Sequential Optimization single lightpath
  requested at a time.
• The PC Reply Message should include the original
  optimization degree associated with the request
  when replying the path computation results.

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Lightpath Route Parameters

• The following Lightpath Route Parameters should
  be indicated
• Bidirectional Assignment of wavelengths for a
  bidirectional LSP request. This means that the
  same wavelength should be assigned in both
  directions on each hop.
• Simultaneous assignment of the same wavelength to
  primary and backup paths.
• The PC Reply Message should include the
  original lightpath route parameter associated
  with the request when replying the path
  computation results.

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Wavelength SelectionPreference - optional

• The PC Request may indicate the Wavelength
  Selection Preference to which a path computation
  request is applied. The Wavelength Selection
  Preference to be supported at the minimum is
• Random
• First Fit
• Most Used
• Least Loaded
• Dont Care
• The PC Reply should indicate which wavelength
  selection preference has actually been applied.

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Timeliness Characteristics - optional

• The request may indicate specific timeliness
  characteristics of lightpath.
• Time Critical this type of request is useful for
  those lightpath establishment requests used for
  restoration of service or other high priority
  real time services.
• Soft Time Bound this type of request is a more
  typical new connection request. While expected
  to be responsive, there should be more time to
  take into account network optimization.
• Scheduled this type of request is useful when
  the requested lightpath connections are not time
  critical (i.e., the request is significantly
  ahead of their intended "in-service" time.

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Duration of lightpath - optional

• The request may indicate specific lightpath
  duration information associated with the request.
  This may be useful to the PCE since it is not
  worthwhile to optimize lightpaths with relatively
  short duration as compared to pseudo-static
  paths.

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Summary Next Step

• Lightpath provisioning in WSON requires a routing
  and wavelength assignment (RWA) which is a
  routing constraint in WSON path computation -gt So
  it is within PCE WG charter.
• Continue to refine PCEP requirements and encoding
  details.