Internet DRAFT - draft-zhangj-ccamp-flexi-grid-ospf-te-ext
draft-zhangj-ccamp-flexi-grid-ospf-te-ext
Network Working Group J. Zhang
Internet-Draft YL. Zhao
Intended status: Informational ZY. Yu
Expires: April 21, 2013 BUPT
XF. Lin
DJ. Wang
XH. Fu
ZTE Corporation
October 18, 2012
OSPF-TE Protocol Extension for Constraint-aware RSA in Flexi-Grid
Networks
draft-zhangj-ccamp-flexi-grid-ospf-te-ext-02
Abstract
ITU-T Study Group 15 has introduced a new flexible grids technology
of DWDM network which is an effective solution to improve the
efficiency of spectrum resource utilization. This memo extends the
OSPF-TE protocol to support constraint-aware routing and spectrum
assignment (RSA) in flexi-grid networks.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 21, 2013.
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document authors. All rights reserved.
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Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
3. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Motivation for Routing Protocol Extension . . . . . . . . . . 4
4.1. Constraints Considerations for RSA . . . . . . . . . . . . 4
4.2. Consecutive Spectrum Slots Information . . . . . . . . . . 5
4.3. Spectrum Compactness . . . . . . . . . . . . . . . . . . . 5
4.4. Variable Guard Band Information . . . . . . . . . . . . . 6
4.5. Modulation level Information . . . . . . . . . . . . . . . 6
5. OSPF-TE Protocol Extension . . . . . . . . . . . . . . . . . . 6
5.1. Consecutive Spectrum Slots Weight Sub-TLV . . . . . . . . 7
5.2. Spectrum Compactne Sub-TLV . . . . . . . . . . . . . . . . 8
6. Super-Channel Label Encoding Format with GB . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . . 10
9.2. Informative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
To enable the dynamic and effective allocation of spectrum resource
based on the demand of the client LSP's requests, the latest revision
of ITU-T Recommendation [G.694.1] has introduced a flexible grid
technique in DWDM optical networks. The flexible grid has a finer
granularity (i.e. according to the definition of flexible grid in
[G.694.1], the data channel can be selected on a channel spacing of
6.25 GHz with a variable slot width measured in units of 12.5 GHz)
for the spectrum slot.
In the dynamic flexi-grid networks, except for selecting an
appropriate route for the client LSP, the appropriate width of
spectrum slot is also needed to choose and assigned to the client
LSP. The spectrum bandwidth assigned to the client LSP is made up of
an appropriate number of consecutive spectrum slots from end-to-end,
which is determined by the used modulation format, according to the
client LSPs data rate requests and physical constraints of the
selected path.
Compared with ITU-T fix-grid optical network some extra constraints
need to be considered when running the routing and spectrum resource
assignment (RSA) in flexi-grid networks. In this memo two of those
constraints (other constraints are left for future considered) that
are necessary for RSA are discussed in detail in flexi-grid networks,
and Spectrum Compactness is introduced .and then the extension of
OSPF-TE protocol for these constraints related to RSA in flexi-grid
networks is described and also the the value of super-channel bitmap
member.
2. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Terminologies
CSSW: Consecutive spectrum slots weight
GB: Guard band
RSA: Routing and spectrum assignment
WSON: Wavelength switched optical networks
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4. Motivation for Routing Protocol Extension
In this section we introduce the RSA constraints and the motivation
of routing protocol extension for of flexi-grid networks
4.1. Constraints Considerations for RSA
When processing RSA in flexi-grid networks, the constraints
information (such as the information of spectrum bandwidth in a
network link and so on.) are necessary for computing and selecting an
appropriate backup route and a certain number of consecutive spectrum
slots for the client LSPs effectively.
Some of the necessary constraints are listed as follows:
o Spectral consecutiveness constraint
o Variable guard band constraint
o Spectral continuity constraint
o Impairments constraint
o Other constraints
All the constraints can generate important impacts for the
performance of the client LSPs, even for the entire network. The
first two constraints are mainly talked about in this memeo.
Just like the wavelength continuity constraint in WSON, the spectral
continuity constraint means allocation of the same spectrum slots on
each link along a path because not all of the nodes in optical
networks have the ability of wavelength conversion.
The degradation of the optical signals due to impairments that
accumulate along the path (without 3R regeneration), can result in
unacceptable bit error rates or even a complete failure to demodulate
and/or detect the received
signal[draft-ietf-ccamp-wson-impairments-07]. So it is necessary to
consider about the impairments constraint within flexi-grid networks.
The impairments constraint in flexi-grid networks will be studied in
future in this memo.
Also, there may be some other constraints for RSA, other than the
four kinds above, such as the modulation levels constraint, which are
left for future researching.
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4.2. Consecutive Spectrum Slots Information
The spectral consecutiveness constraint is that the allocated
spectrum slots must be chosen from consecutive spectrum slots in the
spectrum space on each link of flexi-grid networks.
Compared with the technology of WSON, the number of spectrum slots in
flexi-grid networks will be much larger than the number of wavelength
in WSON. After a long running time, the situation of available
spectrum slots will be much complex, especially the situation of the
available consecutive spectrum slots.
After selecting a route, the appropriate consecutive spectrum slots
need to be assigned for the client LSP. When we choose one of the
backup routes for the client LSP without considering the situation
about the available consecutive spectrum slots information, the route
may have no enough consecutive spectrum slots which means that the
selected route have no available resource for the LSP's request, and
then the client LSP will be rejected or trigger another path
computation process which will increase the blocking rate of the
network or increase network resources consumed by communication and
computing of new route.
When computing a route with the knowledge of the consecutive spectrum
slots information of the network link (for example, the number of ten
available consecutive spectrum slots in a network link, or the number
of twenty available consecutive spectrum slots in a network link.),
it will be very useful to select a better route which has higher
probability of enough available consecutive spectrum slots for the
client LSP. And this will improve the success rate of setting up new
client LSPs.
4.3. Spectrum Compactness
With a new client LSP arriving, a path connection needs to be
establish and proper consecutive of spectral resource needs to be
assigned to this LSP. With the LSP ending, the path connection is
released, and the spectral resource could be assigned for new LSP.
In a dynamic traffic scenario, this setup and tear down process leads
to fragmentation of spectrum resources Note that the probability of
using these pieces of fragmentations is very low since they are not
consecutive. If united together, e.g. one block, they could be used
for new LSP. This process is named defragmentation, which aim to
improve the utilization of spectrum resource. In order to make the
defragmentation more effective, the occupation of spectrum in a link
or in the network is needed to be better known, Spectrum Compactness
is proposed[OFC2012 JTh2A.35].
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4.4. Variable Guard Band Information
Some spectrum slots need to be reserved as Guard Band(GB) between two
adjacent client LSPs to avoid bad impact of non-linear impairments
and other network elements. Since the granularity of the flexi-grid
networks will be very small, the spectrum interval, i.e., GB need to
be considered more carefully to avoid poor quality impact of the
adjacent client LSPs. Which means with the changing of network
environment and the operating of the network, the bandwidth of the GB
also need to change.
In flexi-grid networks, with the increasing of the total
transportation power and the smaller of the channel space, the
channel crosstalk that results from non-linear effects will become
the important factor that affects the performance of the network.
The impact between two adjacency client LSPs may be changing based on
the change of crosstalk and other changes of network. With the
changing of those parameters, the interferences between two adjacency
client LSPs may be increasing, if the Guard Band is fixed, the
quality of the adjacent client LSPs and also the network's will be
decreased. If the GB can be varied based on the network environment
changing, then the bad impact can be avoided.
4.5. Modulation level Information
Based on OFDM, diferent modulation formats could be selected based on
the distance to serve different connections, since the physical
impairments will have high probability to degrade the quality of
connection requests with low-level modulation format such as OOK if
the distance of the connection request is very long.
Supposing there is a scenario, the number of a connection' hops is
very huge, and in some of the connection' link, there is not enough
spectrum resource to serve the connection if use low-level format.
Bandwidth resizing method can be used to solve this scenario.
Bandwidth resizing method is that changing the modulation format in
the middle node of a connection since every network node in the
flexible grids networks based on OFDM technology which has the
ability of choosing different modulation formats, which means several
different modulation formats could be choose in different links for a
connection in the flexible grids networks. So it requests that the
modulation formats of every links of a connection should be
advertised.
5. OSPF-TE Protocol Extension
In this section, we define the enhancements to the Traffic
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Engineering (TE) properties of flexi-grid networks' TE links that can
be announced in OSPF-TE LSAs.
The TE LSA, which is an opaque 10 LSA with area flooding scope
[RFC3630], has only one top-level and has one or more nested sub-TLVs
for extensibility. [RFC3630] also defines two top Type/Length/Value
(TLV) triplet to support traffic engineering of OSPF, i.e. (1) Router
Address TLV and (2) Link TLV. In this memo, we enhance the sub-TLVs
for the Link TLV in support of flexi-grid networks. Specifically, we
add the following sub-TLVs to the Link TLV:
o Consecutive spectrum slots weight sub-TLV
o Spectrum Compactne sub-TLV
5.1. Consecutive Spectrum Slots Weight Sub-TLV
In distribution networks, we propose the CSSW as a sub-TLV of OSPF-TE
Link TLV which represents the situation of the available consecutive
spectrum slots in a link of the flexi-grid networks for example the
percentage of the total bandwidth of the number of five consecutive
spectrum slots, the percentage of the total bandwidth of the number
of ten consecutive spectrum slots ... ). With knowing the weight of
available consecutive spectrum slots in a link, the spectrum resource
assignment in the flexi-grid networks can be working more efficiently
in a distributed network.
slot num 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
slot status||||||||| |||| | | ||||||| | | | | | | | | | |
The figure above shows a link's spectrum status.Assume there are 20
slots on a link, and slot 0, slot 1, slot 2, slot 4, slot 8 and slot
9 are occpuded by three requests. The number of five consecutive
spectrum slots is 6, they are (11~15), (12~16), (13~17), (14~18),
(15~19). The number of ten consecutive spectrum slots is 1, and it
is from slot 10 to slot 10,i.e., (10~19). The number of Spectrum
Joint is 10.
The format of the CSSW sub-TLV is as follows:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = TBD | Length = variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| method| Reserve |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value : Consecutive Spectrum Slots Weight |
// //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBD. The Type of CSSW sub-TLV is left for future to define.
Length: Variable. The length of CSSW sub-TLV is based on its define
of the value which is variable based on different implementation
ways. method: the method to describe the status of consecutive
spectrum. Value: Based on the description method of the status of
consecutive spectrum.
The content of the CSSW sub-TLV is left for future researching.
5.2. Spectrum Compactne Sub-TLV
The Spectrum Compactne sub-TLV based Defragmentation scheme which
indicates the occupation of spectrum in a link or in the network.
The format of the GB sub-TLV is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Method| Value: Spectrum Compactne |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBD.
The Type of Spectrum Compactne sub-TLV is left for future to define.
Length: TBD.
The length of Spectrum Compactne sub-TLV is based on the define of
the value of it.
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Method: Represents different evaluation methods of Spectrum
Compactne.
Value: Based on the method of Spectrum Compactne evaluation.
The different evaluation methods of Spectrum Compactne are left for
future researching.
6. Super-Channel Label Encoding Format with GB
As discussed in [draft-hussain-ccamp-super-channel-label-03], the
Super-Channel is proposed to support flexi-grid networks. In this
memo, we extend the Super-Channel Label Encoding Format by
considering the Guard Band information.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Super-Channel Id (16-bit) |Grid | S.S. | MF |R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| n_start of Grid (16-bit) |Num of Slices in Grid (16-bit) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Bitmap Word #1(first set of 32 slices from the left most edge) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Bitmap Word #2 (next set of 32 contiguous slice numbers) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Bitmap Word #N(last set of 32 contiguous slice numbers) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The above figure shows an encoding Format of Super-Channel Label, all
the fine-detail information can be accessed in
[draft-hussain-ccamp-super-channel-label-03], but to consider about
the Guard Band information, the meaning of the bitmap value is
changed: 0 -- reprents that slice reservation is not required 1 --
reprents that slice reservation is required 2 -- reprents that slice
is required by Guard Band
MF: To show the Modulation Formates that the flexible grids networks
support, we add an eight bit information of MF fields.
R: Reserved(1-bit)
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7. Security Considerations
TBD.
8. Acknowledgments
TBD.
9. References
9.1. Normative References
[OFC2012JTh2A.35]
Yu, X., Zhang, J., Zhao, Y., Peng, T., Bai, Y., Wang, D.,
and X. Lin, "Spectrum Compactness based Defragmentation in
Flexible Bandwidth Optical Networks", RFC 3630,
September 2003.
[RFC2119] Bradner, S., "Key words for use in RFC's to Indicate
Requirement Levels", RFC 2119, March 1997.
[RFC2328] Moy, J., "OSPF Version 2", RFC 2328, April 1998.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
September 2003.
9.2. Informative References
[draft-hussain-ccamp-super-channel-label-03]
Hussain, I., Dhillon, A., Pan, Z., Sosa, M., Basch, B.,
Liu, S., and A. G. Malis, "Generalized Label for Super-
Channel Assignment on Flexible Grid", March 2012.
[draft-ietf-ccamp-wson-impairments-07]
Lee, Y., Bernstein, G., Li, D., and G. Martinelli, "A
Framework for the Control of Wavelength Switched Optical
Networks (WSON) with Impairments", July 2011.
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Authors' Addresses
Jie Zhang
BUPT
No.10,Xitucheng Road,Haidian District
Beijing 100876
P.R.China
Phone: +8613911060930
Email: lgr24@bupt.edu.cn
URI: http://www.bupt.edu.cn/
Yongli Zhao
BUPT
No.10,Xitucheng Road,Haidian District
Beijing 100876
P.R.China
Phone: +8613811761857
Email: yonglizhao@bupt.edu.cn
URI: http://www.bupt.edu.cn/
Ziyan Yu
BUPT
No.10,Xitucheng Road,Haidian District
Beijing 100876
P.R.China
Phone: +8615116984347
Email: yzhziyan@gmail.com
URI: http://www.bupt.edu.cn/
Xuefeng Lin
ZTE Corporation
No.16,Huayuan Road,Haidian District
Beijing 100191
P.R.China
Phone: +8615901011821
Email: lin.xuefeng@zte.com.cn
URI: http://www.zte.com.cn/
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Dajiang Wang
ZTE Corporation
No.16,Huayuan Road,Haidian District
Beijing 100191
P.R.China
Phone: +8613811795408
Email: wang.dajiang@zte.com.cn
URI: http://www.zte.com.cn/
Xihua Fu
ZTE Corporation
West District,ZTE Plaza,No.10,Tangyan South Road,Gaoxin District
Xi'an 710065
P.R.China
Phone: +8613798412242
Email: fu.xihua@zte.com.cn
URI: http://www.zte.com.cn/
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