Network Working Group J. Zhang
Internet-Draft YL. Zhao
Intended status: Informational ZY. Yu
Expires: April 26, 2012 BUPT
October 24, 2011
OSPF-TE Protocol Extension for Constraint-aware RSA in Flexi-Grid
Networks
draft-zhangj-ccamp-flexi-grid-ospf-te-ext-00
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.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 26, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
Zhang, et al. Expires April 26, 2012 [Page 1]
Internet-Draft Routing extension for C-RSA October 2011
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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 in Flexi-Grid
Networks . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Consecutive Spectrum Slots Information . . . . . . . . . . 5
4.3. Variable Guard Band Information . . . . . . . . . . . . . . 5
5. OSPF-TE Protocol Extension . . . . . . . . . . . . . . . . . . 6
5.1. Consecutive Spectrum Slots Weight Sub-TLV . . . . . . . . . 6
5.2. Variable Guard Band Sub-TLV . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 8
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
Zhang, et al. Expires April 26, 2012 [Page 2]
Internet-Draft Routing extension for C-RSA October 2011
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.
The routing and spectrum assignment (RSA) of flexi-grid networks need
to consider some constraints. In this memo two of those constraints
(other constraints are left for future considered) that are necessary
for RSA are discussed in detail, and then describes the OSPF-TE
protocol extension for these constraints related to RSA in flexi-grid
networks.
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
Zhang, et al. Expires April 26, 2012 [Page 3]
Internet-Draft Routing extension for C-RSA October 2011
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 in Flexi-Grid Networks
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.
Zhang, et al. Expires April 26, 2012 [Page 4]
Internet-Draft Routing extension for C-RSA October 2011
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. 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
Zhang, et al. Expires April 26, 2012 [Page 5]
Internet-Draft Routing extension for C-RSA October 2011
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.
5. OSPF-TE Protocol Extension
In this section, we define the enhancements to the Traffic
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 Variable Guard Band 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.
The format of the CSSW sub-TLV is as follows:
Zhang, et al. Expires April 26, 2012 [Page 6]
Internet-Draft Routing extension for C-RSA October 2011
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| 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.
Value: TBD
The content of the CSSW sub-TLV is left for future researching.
5.2. Variable Guard Band Sub-TLV
The Guard Band sub-TLV (which is also short for GB sub-TLV) describes
the spectrum interval between two client LSPs to avoid crosstalk and
other network elements(such as impairment elements) that can affect
the transmission performance of each client LSP.
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 = TBD | Length = TBD |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value = Variable Guard Band |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBD.
The Type of GB sub-TLV is left for future to define.
Zhang, et al. Expires April 26, 2012 [Page 7]
Internet-Draft Routing extension for C-RSA October 2011
Length: TBD.
The length of CSSW sub-TLV is based on the define of the value of it.
Value: TBD.
The content of the CSSW sub-TLV and it is left for future
researching.
6. Security Considerations
TBD.
7. Acknowledgments
TBD.
8. References
8.1. Normative References
[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.
8.2. Informative References
[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.
Zhang, et al. Expires April 26, 2012 [Page 8]
Internet-Draft Routing extension for C-RSA October 2011
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/
Zhang, et al. Expires April 26, 2012 [Page 9]