Network Working Group
Internet Draft Sharfuddin Syed
Intended status: Standard Track Rajan Rao
Expires: Oct 23, 2012 Marco Sosa
Biao Lu
Infinera
Bert Basch
Andrew G. Malis
Verizon Communications
April 23, 2012
A Framework for control of Flex Grid Networks
draft-syed-ccamp-flexgrid-framework-ext-01.txt
Abstract
This document provides a framework for applying the Generalized
Multi-Protocol Label Switching (GMPLS) architecture and protocols to
a Flex-Grid capable optical switching layer.
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Copyright Notice
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Table of Contents
1. Introduction...................................................2
2. Terminology....................................................3
3. Acronyms.......................................................4
4. Requirements and constraints...................................5
5. Use cases......................................................8
6. Protocol Implications.........................................14
7. Security Considerations.......................................14
8. IANA Considerations...........................................14
9. References....................................................15
9.1. Normative References.....................................15
9.2. Informative References...................................15
10. Acknowledgments..............................................16
11. Authors' Addresses...........................................16
12. Contributor's List...........................................17
1. Introduction
To enable scaling to data rates beyond 100 Gbps, next generation
transport systems based on a super-channel concept are currently
being developed. To allow efficient allocation of optical spectral
bandwidth for such high bit rate systems, the International
Telecommunication Union Telecommunication Standardization Sector
(ITU-T) is extending the G.694.1 grid standard beyond the
traditional fixed grid assignment of a constant spectral width per
channel (termed ''Fixed-Grid'') to include flexible grid (termed
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''Flex-Grid'') support allowing for varying spectral width per
channel, to support a variety of high-bit rate channels, each
optimizing the spectral bandwidth needed for its particular channel
type.
Current IETF GMPLS efforts for routing and signaling on Wavelength
Switched Optical Networks (WSONs) have been focused on Routing and
Wavelength Assignment (RWA) for fixed grid Reconfigurable Optical
Add-Drop Multiplexors (ROADMs) and line systems. This framework
document is intended to set the stage on introducing the flexible
grid concept, and setting the requirements and use cases to be taken
into consideration for extending the GMPLS protocols to include
support for flexible grid capable elements and the need for
specifying blocks of spectrum, rather than just wavelengths.
Section 2 of this document provides background terminology, while
section 3 provides an acronym list. Section 4 then goes over a set
of requirements that must be considered when defining the protocol
extensions to support flexible grid elements. Section 5 then
provides further background with a set of use cases. Section 6 goes
over protocol implications; section 7 covers security
considerations; section 8 lists IANA considerations. Section 9
provides a list of references. Acknowledgements and contact
information is provided in sections 10-12.
2. Terminology
A. Frequency Slot:
A frequency range allocated to a given channel and
unavailable to other channels within the same flexible grid
[FLEX-GRID]
It is a contiguous portion of the spectrum available for an
optical passband filter. A frequency slot is defined by its
nominal central frequency and its slot width.
B. Spectral Slice:
The minimum granularity of a frequency slot (e.g. 12.5GHz).
C. Slot width:
The full width of a frequency slot in a flexible grid [FLEX-
GRID].
The slot width is equal to number of spectral slices in the
slot times the width of spectral slice.
D. Super-channel:
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A super-channel is a collection of one or more frequency
slots to be treated as a unified entity for management and
control plane purposes (Ref to figure-1).
E. Contiguous Spectrum Super-channel:
A contiguous spectrum super-channel is a super-channel with a
single frequency slot (Ref to figure-1).
F. Split-Spectrum super-channel:
A split-Spectrum super-channel is a super-channel with
multiple frequency slots.
Each frequency slot will be allocated an independent passband
filter, irrespective of whether frequency slots are adjacent
or not.
200 GHz 200 GHz 200 GHz 200 GHz
<------> <------> <------> <------>
________ ________ ________ ________
| | | | | | | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
|________| |________| |________| |________|
|<--s1-->| |<--s2-->| |<--------s3----------->|
Contiguous Spectrum super-channels Split Spectrum super-channel
Figure 1: Super-Channel
3. Acronyms
OCG: Optical Carrier Group
SCH: Super Channel
OCh: Optical Channel
OCC: Optical Channel Carrier
OTUk: Optical channel Transport Unit level k
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ODUk: Optical channel Data Unit Level k
ODUj: Optical channel Data Unit Level j
CDC: Colorless, Directionless and Contentionless
CD: Colorless and Directionless
ROADM: Reconfigurable Optical Add-Drop Multiplexer
4. Requirements and constraints
This section covers the high level requirements for the support of
super-channels over flexible grid infrastructure (Flex-Grid).
Specifically, the scope of requirements and constraints listed in
this section covers the functionality that shall be supported by the
control plane sub-system. The Features are listed as a list of
Requirements Tagged as Rn, for better traceability and coverage in
other related drafts and/or for references by other related
standards across other standard bodies.
R1: Flexible size of super-channel
The protocol shall allow the super-channels on the Flex-Grid to be
of different size/width. The number of slices and the granularity of
each slice shall be flexible.
R2: Flexible mapping of super-channel
The super-channels shall be allowed to be mapped to any spectrum
location in the ITU Grid.
The frequency slots allocation of super-channels on the ITU-Grid
shall confirm to [FLEX-GRID]
R3: Contiguous Spectrum and Split Spectrum super-channel
The protocol shall allow the use of super-channels which can be
contiguous or non-contiguous.
Example: consider a system supporting 500GHz super-channel.
In case of contiguous spectrum, the super-channel is allocated with
40 slices of 12.5GHz granularity. This super-channel is placed
directly on the Flex-Grid at any location.
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In case of split spectrum, the super-channel is divided into
multiple members. Considering the same example scenario, the 500GHz
super-channel can be divided into 2 member split spectrum channels.
Each member is allocated a different flexible location on the Flex-
Grid. Each frequency slot can be 250GHz, 20x12.5GHz slices allocated
for frequency slot.
R4: Co-routing of split-spectrum super-channel
The protocol shall support the co-routing of frequency slots
within the split-spectrum super-channels.
Please refer to the Figure 5 and Use Case 3, depicting the co-
routing of split-spectrum super-channels.
R5: Flexible Modulation Formats and polarization mode for different
super-channels on the same Flex-Grid
Each super-channel mapped on to the Flex-Grid system shall have the
capability to support different modulation formats with either
single or dual polarization modes.
R6: Fixed vs Flexible Grid super-channel interworking
The Control Plane protocol shall handle nodes which support flex-
grid functionality in addition to nodes that only support fixed grid
functionality. The enhanced control plane protocol with the flex-
grid extensions shall also be able to work with fixed grid network
in a backwards compatible manner.
This requirement is to enable introduction of flex-grid systems into
existing fixed-grid network. This can also be used to deploy flex-
grid system in certain segments of the network. Please also refer to
the use case section of this document.
R7: Support for the CDC based super-channels over Flex-Grid
The super-channel over the Flex-Grid control plane frame work shall
support CDC (Connectionless, Directionless and Contentionless)
architecture. Further, flexibility of control shall be provided,
such that, depending on deployment scenarios and application, a sub-
set of CDC features are used on a given network segment. Hence, each
type of ROADMs shall be supported.
R8: Directionless/Contentionless super-channels
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The protocol shall allow for routing the super-channels in different
fiber directions/degrees, based on the following criteria:
a) Based on spectral slices
b) Based on fibers/nodes
The super-channels with the same frequency slot mapping are not
allowed to be provisioned over a given fiber direction.
Please refer to the Figure 5 and Use Case 3, depicting the handling
of same super-channel at a CDC node.
R9: Resizing of super-channel bandwidth
Depending on the spectral bandwidth changes, the protocol shall
allow super-channels resizing.
R10: super-channel LSP restoration
The protocol shall support the super-channel based LSP restoration
feature, with the following features:
a) During the restoration process, it shall be possible for the
protocol to pick different frequency slots of super-channel,
keeping the number and size of slices the same.
b) LSP restoration with optional pre-computed path (with or without
resource reservation) shall be supported.
c) Revertive and Non-Revertive restoration options shall be provided.
R11: Embedded Control Channel for super-channel routing and
signaling
The system shall continue to use the standard mechanism for ECC
defined in [ref: OSC based control channel], for OAM features
required to be supported between network elements deploying super-
channel over Flex-Grid.
R12: Management Plane and Control Plane feature interaction for
super-channel
The system shall keep track of important bandwidth related
parameters for the Flex-Grid based system. Important parameters
include (but not limited to):
a) Available Spectral Slices
b) Provisioned super-channels along with provisioned spectral-slices
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5. Use cases
The use cases described in this section are for information only.
The OTN hierarchy described in this section is sure to be discussed
in ITU SG-15 Q6 & Q14. Within the scope of this frame-work document,
the main focus is super-channel entity. The remaining layers are
described to illustrate the relationship with the digital layers.
With respect to the mapping hierarchy in the OTN layers, multiple
OCHs are mapped to the SCH, and multiple OCCs (Optical Channel
Carriers) are mapped to an OCH. This hierarchy is depicted in Figure
2 below. Specifically, the following flexibility of number of
instances that are mapped between the layers shall be supported.
X number of OCC mapped to OCH
Y number of OCH mapped to SCH
Z number of SCH mapped to OCG
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__________ __________
| | | |
| ODUj | ... | ODUj |
|__________| |__________|
| |
| |
____|__________________|____
| |
| OTUk |
|____________________________|
|
|
_____________|______________
| |
| OCH |
|____________________________|
| |
| |
____|_____ _____|____
| | | |
|carrier 1 | ... |carrier n |
|__________| |__________|
| |
| |
____|__________________|____
| |
| SCH |
|____________________________|
|
|
______________|_____________
| |
| SCG |
|____________________________|
Figure 2: Super-Channel mapping to OTN hierarchy
Example Use Case 1: Super-Channel with multiple OCHs and multiple
carriers per OCHs.
The following Figure 3 gives an example use case where multiple OCH
are carrier over a single SCH. Please note that this is an example
use case only. In general, the system shall be capable of supporting
flexible mapping where there is flexible number of carriers mapped
into an OCH and a flexible number of OCHs mapped to a single Super-
Channel.
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____ ____ ____ ____ ____ ____ ____ ____ ____ ____
| | | || | | || | | || | | || | | |
|ODUj|..|ODUj||ODUj|..|ODUj||ODUj|..|ODUj||ODUj|..|ODUj||ODUj|..|ODUj|
|____| |____||____| |____||____| |____||____| |____||____| |____|
| | | | | | | | | |
| | | | | | | | | |
_|______|___ _|______|___ _|______|___ _|______|___ _|_______|__
| || || || || |
| OTUk || OTUk || OTUk || OTUk || OTUk |
|____________||____________||____________||____________||____________|
| | | | |
| | | | |
_____|_______ _____|______ _____|______ _____|______ _____|______
| || || || || |
| OCH || OCH || OCH || OCH || OCH |
|____________||____________||____________||____________||____________|
| | | | | | | | | |
| | | | | | | | | |
_|__ _|__ _|__ _|__ _|__ _|__ _|__ _|__ _|__ _|__
| | | | | | | | | | | | | | | | | | | |
| C1 | | C2 | | C3 | | C4 | | C5 | | C6 | | C7 | | C8 | | C9 | |C10 |
|____| |____| |____| |____| |____| |____| |____| |____| |____| |____|
| | | | | | | | | |
| | | | | | | | | |
_|______|______|______|______|______|______|______|______|______|___
| |
| SCH |
|____________________________________________________________________|
|
|
______________|_____________
| |
| OCG |
|____________________________|
Figure 3: Super-Channel use case showing multiple OCH and multiple carriers per OCH
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Example Use Case 2:
The following Figure 4 shows the case where multiple OCHs are
carried over separate super-channels.
____ ____ ____ ____
| | | | | | | |
|ODUj|.. |ODUj| |ODUj|.. |ODUj|
|____| |____| |____| |____|
| | | |
| | | |
___|________________________|____ __|_________________________|____
| | | |
| OTUk | | OTUk |
|_________________________________| |_________________________________|
| |
| |
________________|________________ ________________|________________
| | | |
| OCH | | OCH |
|_________________________________| |_________________________________|
| | | | | | | | | |
| | | | | | | | | |
__|__ _|__ _|__ _|__ _|__ _|__ _|__ _|__ _|__ _|__
| | | | | | | | | | | | | | | | | | | |
| C1 | | C2 | | C3 | | C4 | | C5 | | C6 | | C7 | | C8 | | C9 | |C10 |
|____| |____| |____| |____| |____| |____| |____| |____| |____| |____|
| | | | | | | | | |
| | | | | | | | | |
__|______|______|______|______|_ _|______|______|______|______|__
| | | |
| SCH1 | | SCH2 |
|________________________________| |________________________________|
\ /
\ /
\____________________________________/
|
______________|_____________
| |
| SCG |
|____________________________|
Figure 4: Split-Spectrum Super-Channel use case showing multiple OCH and multiple
carriers per OCH
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Example Use Case 3: Network Level Use Case of super-channel
A network level diagram to illustrate the use of CDC based super-
channel (contiguous spectrum and split-spectrum) is shown in Figure
5 below. In this scenario, N1 and N2 are digital/TDM nodes, where
the client services originate. N2, N3, N4 and N5 are Optical/WDM
nodes on which the super-channels are provisioned. Node N2 is CDC
ROADM and Nodes N3, N4 and N5 are Colorless ROADMs only.
Four super-channels are provisioned in this example network. Super-
Channels S1 are contiguous spectrum super-channels, both using the
same frequency slots, and are added/dropped at Node N2. The
contention for the same super-channel (with exactly the same
frequency slot mapping) is avoided by routing these super-channels
in different degrees of the network. Alternatively, if these super-
channels have to go through the same fiber path, then the frequency
slots occupied on the Flex-Grid shall be different.
Super-channels S2-1 and S2-2 illustrates the split-spectrum super-
channel that is co-routed over the same fibers in the network.
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|
|
---------
| |
| N4 |
| |
| |
---------
/ \
S1, s2-1, s2-2 / \ s2-1, s2-2
_________ _________ / D1 \_________ ______
| |--s1----| | | | | |
| |--s2-1--| | | N5 |--s2-1-| N6 |
| N1 |--s2-2--| N2 | | |--s2-1-| |
_ |_________|--s1--- |_________| |_________| |______|
\ D2 /
S1 \ /
\ /
_________
| |
| N3 |
| |
|_________|
|
|
| s1
Figure 5: Super-Channel Network Level use case
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Example Use Case 4: Fixed and Flexible Grid Interworking
- In Figure 6:
o The Nodes N2 and N3 are Flex-Grid and Fixed grid capable
nodes
o The Nodes N1 and N4 are fixed grid capable nodes.
- Fixed and Flexible support on the same interface
o In Figure 6, this is represented by Link L3
- BW advertisement that include both fixed and flexible grid by Flex
Grid capable nodes
- Signaling support for both fixed and flex-grid.
________ _________ ________ ________
| |--L1--| | | | | |
| | | |---L3--- | |---L4----| |
| |--L2--| | | | | |
|________| |_________| |________| |________|
Figure 6: Use case for fixed and flex-grid interworking
6. Protocol Implications
Support GMPLS Routing extensions to satisfy requirements in section
4.0.
Support GMPLS Signaling extensions to satisfy requirements in
section 4.0.
7. Security Considerations
<Add any security considerations>
8. IANA Considerations
IANA needs to assign a new Grid field value to represent ITU-T Flex-
Grid.
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9. References
9.1. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
9.2. Informative References
[1] ITU-T Recommendation G.694.1, "Spectral grids for WDM
applications: DWDM frequency grid", June 2002
[2] [FLEX-GRID] Unpublished ITU-T Study Group-15 doc: G.694.1
[Rev-2, 12/2011]
[3] [RFC 6163] Framework for GMPLS and Path Computation Element
(PCE) Control of Wavelength Switched Optical Networks (WSONs)
[4] draft-ietf-ccamp-rwa-info-13.txt: Routing and Wavelength
Assignment Information Model for Wavelength Switched Optical
Networks
[5] draft-syed-ccamp-flexgrid-framework-ext.pdf - - PDF version of
this draft which contains figures.
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10. Acknowledgments
11. Authors' Addresses
Sharfuddin Syed
Infinera
140 Caspian Ct., Sunnyvale, CA 94089
Email: ssyed@infinera.com
Rajan Rao
Infinera
140 Caspian Ct., Sunnyvale, CA 94089
Email: rrao@infinera.com
Marco Sosa
Infinera
140 Caspian Ct., Sunnyvale, CA 94089
Email: msosa@infinera.com
Biao Lu
Infinera
140 Caspian Ct., Sunnyvale, CA 94089
Email: blu@infinera.com
Bert Basch
Verizon Communications
60 Sylvan Rd., Waltham, MA 02451
Email: bert.e.basch@verizon.com
Andrew G. Malis
Verizon Communications
60 Sylvan Rd., Waltham, MA 02451
Email: andrew.g.malis@verizon.com
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12. Contributor's List
Radhakrishna Valiveti
Email: rvaliveti@infinera.com
Iftekhar Hussain
Email: IHussain@infinera.com
Abinder Dhillon
Email: ADhillon@infinera.com
Mike VanLeeuwen
Email: MVanleeuwen@infinera.com
Ping Pan
Email: ppan@infinera.com
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