One document matched: draft-li-ccamp-wson-igp-eval-01.txt
Differences from draft-li-ccamp-wson-igp-eval-00.txt
Network work group D. Li
Internet Draft J. Gao
Intended Status: Informational Y. Lee
Expires: January 2009 Huawei
July 11, 2008
Evaluation of Possible Interior Gateway Protocol Extensions for
Wavelength Switching Optical Networks
draft-li-ccamp-wson-igp-eval-01.txt
Status of this Memo
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This Internet-Draft will expire on January 11, 2009.
Abstract
Wavelength Division Multiplexing (WDM) is a technology for optical
communications, in which the user traffic is carried by data channels
of different optical wavelengths. In traditional WDM Networks, each
wavelength path is statically configured. With the deployment of the
Reconfigurable Optical Add-Drop Multiplexer (ROADM) and the
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Wavelength Selective Switch (WSS), WDM networks have become more
dynamic, and operators can flexibly set up wavelength paths to carry
user traffic.
This document discusses the set of Interior Gateway Protocol (IGP)
requirements that would enable distributed light path computation in
Wavelength Switched Optical Networks (WSON). An IGP impact analysis
is also provided. According to the analysis, there is no significant
impact on the IGP performance.
Table of Contents
1. Introduction.................................................2
2. Typical WDM Node.............................................3
3. Wavelength Conversion Constraints............................4
4. Available wavelength information.............................5
5. Requirements for IGP Extension...............................5
6. Assessment of the WDM node constraint information............6
6.1. Potential Wavelength Connectivity Information...........6
6.2. Wavelength Status Information...........................8
6.3. IGP Extensions..........................................8
6.3.1. Lambda Information of Each Fiber...................8
6.3.2. Potential Wavelength Connectivity Information......9
6.3.3. Wavelength Status Information.....................12
7. Security Considerations.....................................13
8. IANA Considerations.........................................13
9. Acknowledgments.............................................13
10. References.................................................13
10.1. Normative References..................................13
10.2. Informative References................................13
11. Authors' Addresses.........................................13
12. Full Copyright Statement...................................15
13. Intellectual Property Statement............................15
1. Introduction
Wavelength Division Multiplexing (WDM) is a technology for optical
communications, in which the user traffic is carried by different
data channels of optical wavelengths. In traditional WDM Networks,
each wavelength path is statically configured. With the deployment of
the Reconfigurable Optical Add-Drop Multiplexer (ROADM) and the
Wavelength Selective Switch (WSS), WDM networks have become more
dynamic, and operators can flexibly set up wavelength paths to carry
user traffic.
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[WSON-FRAME] provides control plane models for key wavelength
switched optical network subsystems and processes. Section 5.2 of
[WSON-FRAME] describes the subsystem properties which may be conveyed
via an Interior Gateway Protocol (IGP).
This document discusses the set of IGP requirements that would enable
distributed light path computation in Wavelength Switched Optical
Networks (WSON). An IGP impact analysis is also provided. According
to the analysis, there is no significant impact on the IGP
performance.
This document is currently limited to consideration of single
component links per TE link. Link Bundles are for future
consideration.
2. Typical WDM Node
Add Drop
Fiber5~8|||| |||| Fiber9~12
|||| ||||
|||| ||||
+-------------------------------+
| +---------------+ |
| /|---| +-----------+ |---|\ |
Fiber 1 | | |---| |\ /| |---| | | Fiber 3
Dir 1 =====|=| | . | | \ / | | . | |=|===== Dir 3
| | | . | |Wavelength | | . | | |
| \|---| | Switch | |---|/ |
| | | \ / | | |
| /|---| | / | |---|\ |
Fiber 2 | | |---| | / \ | |---| | | Fiber 4
Dir 2 =====|=| | . | | / \ | | . | |=|===== Dir 4
| | | . | | / \ | | . | | |
| \|---| | / \ | |---|/ |
| | |/ \| | |
| +---| +-----------+ |---+ |
| | +---------------+ | |
| | +- - - - - - -+ | |
| | | Wavelength | | |
| +----| Converter |----+ |
| | (Optional) | |
| +- - - - - - -+ |
+-------------------------------+
Figure 1: Typical WDM Node
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Figure 1 shows a typical WDM node, which consists of a Wavelength
Switch module, a Multiplexer/DeMultiplexer module, and a Wavelength
Converter module. In this example, there are four directions on the
line side, and four add/drop directions on the tributary side.
For example, in a 160-wavelength system, each fiber of the line side
contains 160 wavelengths, and traffic can be carried by each
wavelength. The wavelength can be switched to a different direction
(or a different fiber) at the WDM node.
Moreover, if the WDM node has the wavelength conversion capability,
one wavelength can be switched to a different wavelength of a
different direction. But there may be a limitation for wavelength
conversion, so that not every wavelength can be switched to any other
wavelength on any other fiber.
3. Wavelength Conversion Constraints
For each WDM node, not all the wavelengths on a fiber can necessarily
be converted to any other wavelength on any other fiber. For example,
lambda 1 on an incoming fiber might only be convertable to lambda 2,
lambda 3, or lambda 4 on a particular outgoing fiber, and cannot be
converted to lambda 5 or other wavelengths on that outgoing fiber.
The wavelength conversion constraints directly affect the potential
connectivity of wavelengths in WSON. There are three kinds of
wavelength conversion capabilities:
o No wavelength conversion.
o Partial wavelength conversion. Some of the wavelengths can be
converted to different wavelengths.
o Full wavelength conversion. All of the wavelengths can be
converted to any wavelengths.
If no wavelength conversion is possible, there may be three more
cases:
o Each of the wavelengths on one fiber can only be connected to the
same wavelength on some other fibers.
o Some subset of wavelengths on one fiber can be connected only as a
set to the same wavelengths on some other fibers.
o A particular wavelength on one fiber can be connected only to the
same wavelength on another specific fiber.
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4. Available wavelength information
In order to perform end-to-end wavelength computation, the wavelength
label is certainly convenient to have global semantics, but it is not
necessary. For example, an NMS could know the details of each NE and
perform its own mappings between the local significance wavelength
labels. So the collection of potential wavelength connectivity
information, wavelength path computation, and signaling the
wavelength path, all could be solved by local wavelength label
mappings performed by NMS. In order to avoid such complicated and
potentially error-prone operations, it is desirable to use the same
semantics for the wavelength label on every hop.
For example, the wavelength label range [lambda 1, lambda 5] of fiber
1 can be connected to the same wavelength label range of fiber 2. But
only lambda 3 is available to carry the traffic, other wavelength
labels are occupied. In order to compute a wavelength path, available
wavelength information needs to be known by the node performing the
computation.
If the wavelength availability information is not known by the node
performing the path computation, then the computation can only be
performed at the level of TE links, and wavelength assignment must be
resolved locally by the switches on a hop-by-hop basis enhanced by
signaling protocol mechanisms used to negotiate label selection.
However, this case may be very inefficient in the signaling protocol,
and can easily lead to blocking problems where a path is selected for
which there is no suitable wavelength availability, unless some or
all of the switches along the path are capable of full wavelength
conversion. In the general case of limited or no wavelength
conversion, information on wavelength availability is essential to
perform efficient and accurate path computation.
5. Requirements for IGP Extension
In WSON, wavelength path computations based on the data link topology
and the TE link states alone cannot guarantee that computed
wavelength paths can actually be successfully established. The
following three factors should also be considered in wavelength path
computation:
o Wavelength conversion constraints
o Wavelength connectivity
o Per-fiber wavelength availability information.
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Each WDM node has this information about its own fibers, but the
information needs to be distributed to the points of computation.
The IGP that is already used to advertise TE information within the
WSON is a candidate solution to distribute this constraint
information. If the IGP were to be used in this way then the
following requirements would need to be applied:
o The constraint information should be small, so that it must not
affect the performance of IGP;
o IGP extension should support all kinds of wavelength conversion
capabilities;
o IGP extension should support the scalability of different
wavelength multiplexer systems, such as 40-wavelength WDM, 80-
wavelength WDM, and 160-wavelength WDM;
6. Assessment of the WDM node constraint information
When computing an available wavelength from source to destination,
two types of information are needed along with potential paths. One
is available wavelength information in all the fibers, the other is
the potential wavelength connectivity in all the nodes.
In a deployed WDM network, the information which is required to
compute a wavelength path consists of:
o Potential wavelength connectivity information (Including
Wavelength conversion constraints and Wavelength connectivity
mentioned in section 5.)
o Wavelength status information i,e, Per-fiber wavelength
availability information .
6.1. Potential Wavelength Connectivity Information
The wavelength that an optical fiber can support is pre-configured,
static information. This information needs to be advertised only once
in the general case, because it is not expected to change frequently
when the network is running.
This information should be advertised again, only if:
o The link is updated to support more or fewer wavelengths;
o The link is changed to use a new wavelength band;
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o The switch at the end of the link runs out of shared wavelength
conversion capability (for example, uses up all capacity on a
switch fabric) which will affect the potential wavelength
connectivity.
For a fiber which can support 160 wavelengths, the size of wavelength
information supported by the fiber reaches about 160*4 = 640 bytes,
where each wavelength is identified by the wavelength label format
defined in [G.694-Label].
For a fiber that can support 160 wavelengths, and considering a node
that has wavelength conversion capability, the size of potential
wavelength connectivity information of each fiber pair may be as much
as 3200 bytes:
Input fiber = lambda 1, lambda 2, ..., lambda 160
Output fiber = lambda 1, lambda 2, ..., lambda 160
So the 160x160 matrix (M[160,160]) can be represented by a bitmap.
For example, if lambda 1 of Input fiber can be connected or converted
to lambda 4 of Output fiber, then M[1,4] is set to 1. Otherwise,
M[1,4] is set to 0. The bit-matrix is correlated to the static list
of wavelengths available on the fiber as described earlier in this
section.
Total size = 160 * 160 / 8 = 3200 bytes.
This information is not expected to change frequently. It can be
advertised just once. Further more, by applying some encoding or
compression algorithm, the size of this information may be reduced a
lot.
The wavelength conversion capability is not supported at all nodes in
a WSON. It may be the case that only a few WDM nodes support
wavelength conversion. In this case, for most of the WDM nodes, the
potential wavelength connectivity information may be simplified to
the following information:
o Input fiber and Output fiber with full wavelength range;
or,
o Input fiber and Output fiber with a specific wavelength range
(from lambda m to lambda n);
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o The wavelength connectivity between input fiber and output fiber
including wavelength switch capability and wavelength conversion
constraints.
6.2. Wavelength Status Information
In WSON, the status information of a certain wavelength in a fiber
should be refreshed following any change. When a wavelength is
assigned to set up a wavelength LSP or released when a wavelength LSP
is torn down, the status information of this wavelength on each link
along the path should be updated. This information is dynamic
information and needs to be distributed to all computation points.
To minimize the size of information, we can use a bitmap to indicate
the wavelength status information of a fiber, i.e. only one bit is
used to indicate the status of a certain wavelength (the wavelength
is either available or not available). The bitmap is correlated to
the static wavelength list described in Section 6.1.
For a fiber which can support 160 wavelengths, the size of the
wavelength status information of a fiber is only 20 bytes. So it
should not impact the IGP performance to advertise this information.
6.3. IGP Extensions
A new Opaque LSA can be introduced to carry wavelength information of
a fiber and potential wavelength connectivity information of node.
6.3.1. Wavelength Information of Each Fiber
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Lambda_num |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lambda 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lambda 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ...... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lambda n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Reserved: 16 bits
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This field is reserved. It MUST be set to 0 on transmission and MUST
be ignored on receipt.
Lambda_num: 16 bits
The number of wavelengths that the fiber supports;
Lambda n: 32 bits
The wavelength label information. The label format is defined in
Section 5 of [G.694-Label].
6.3.2. Potential Wavelength Connectivity Information
The format of potential wavelength connectivity information is
proposed 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U| B |C| Z | W | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Row | Column |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reachable link ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bitmap list |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ...... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ...... | Padded bit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
U: 1 bit
Bidirectional indicated bit.
1 = Unidirectional;
0 = Bidirectional;
If U is set to 1 (unidirectional), it only indicates the wavelength
potential connectivity from row link identified by Row link ID to
column link identified by column link ID.
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If U is set to 0 (bidirectional), it indicates that the wavelength
potential connectivity from row link identified by Row link ID to
column link identified by column link ID is the same as that of from
column link to row link.
B: 2 bits
Indicates the wavelength switching/converting capability of each pair
of TE links.
00 = Limited wavelength switching or wavelength conversion
Refers to the bitmap list data for the details of limited wavelength
switching or wavelength conversion for each pair of TE links.
01 = Non-blocking for same wavelength
Indicates there is no blocking only for the same wavelength of each
pair of TE links. In this case, the wavelength of this link can be
switched to only the same wavelength of the reachable link, and the
following bitmap may not need to be presented.
10 = Non-blocking for any wavelength
Indicates there is no blocking for the any wavelength of each pair of
TE links. In this case, any wavelength of this link can be switched
or converted to any wavelength of the reachable link, and the
following bitmap may not need to be presented.
11 = Reserved
C: 1 bit
Data compressed indicated bit
0 = Not compressed
Indicates the bitmap list data has not been compressed.
1 = Compressed
Indicates that the bitmap list data has been compressed by the
algorithm denoted per "Z" field.
Z: 4 bit
Compression Algorithm (TDB)
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Indicates which compression algorithm has been applied when the "C"
bit is set to 1.
W: 3 bit
Indicates how many bits are used to indicate the potential
connectivity information in the bitmap list data. Usually "W" is set
to 0, which indicates only one bit is used. This field can provide
the flexibility of bitmap list. For example, when we want to indicate
the temporary connection for testing, only one bit is not enough.
Reserved: 31 bits
This field is reserved. It MUST be set to 0 on transmission and MUST
be ignored on receipt.
Row: 16 bits
Indicates the number of rows in the matrix. This has the same value
as the count of wavelengths supported by this fiber (Lambda_num in
the wavelength information sub-TLV).
Column: 16 bits
Indicates the number of columns in the matrix. This has the same
value as the number of wavelengths of the TE link identified by
Reachable_link ID.
Reachable link ID: 32 bits
Indicates the TE link denoted by this format to which this matrix
applies. It is a 32 bit Unnumbered Interface ID.
Bitmap list: Variable Length
The matrix indicates the potential connectivity from lambdas on the
TE link denoted by this format, to Reachable link ID. Each bit or
each set of bits indicates the potential connectivity of a certain
wavelength pair indicated by M[m n]. If there has a potential
connectivity, the corresponding bit(s) are set to 1; otherwise they
are set to 0. Indexes start at 1 and run to the count of wavelength
on each fiber. The bit indicated by M[m n] is located at offset (m-
1)*32+n from the first bit when we use one bit to indicate the
potential connectivity information.
Padded bit: Variable Length
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It is used to pad the bit to make the whole number of bits in the
bitmap to be a multiple of 32. Padded bits MUST be set to 0.
The bit-matrix compression techniques will be discussed in a future
version of this document.
6.3.3. Wavelength Status Information
A new TE link sub-TLV of an Opaque LSA can be introduced to carry the
wavelength status 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| W | Reserved | Wavelength Status Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Wavelength_Status |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ...... | Padded bits |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
W: 3 bit
Indicates how many bits are used to denote the wavelength status
information. Usually "W" is set to 0, which indicates only one bit is
used to indicate if the wavelength is assigned.
Wavelength Status Length: 16 bits
Indicates the number of the wavelength of each TE link.
Wavelength Status Data: Variable Length
Each bit or several bits (indicated by "W") indicate the availability
status of one wavelength.
In the case of W = 1:
1 = Available
0 = Assigned (in use, or failed, or administratively down, or under
testing);
In the case of W = [2,8], TBD.
Padded bit: Variable Length
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It is used to pad the bit to make the whole number of bits in bitmap
be the time of 32. Padded bit MUST be set to 0.
7. Security Considerations
TBD.
8. IANA Considerations
This requirement document makes no requests for IANA action.
9. Acknowledgments
We would like to thank Adrian Farrel for his useful comments.
10. References
10.1. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997
[WSON-FRAME] G. Bernstein, Y. Lee, "Framework for GMPLS and PCE
Control of Wavelength Switched Optical Networks", Internet
Draft, work in progress, draft-ietf-ccamp-wavelength-
switched-00.txt, May 2008.
[G.694-Label] T. Otani, H. Guo, "Generalized Labels for G.694 Lambda-
Switching Capable Label Switching Routers", Internet Draft,
work in progress, draft-ietf-ccamp-gmpls-g-694-labels-
01.txt, May 2008.
10.2. Informative References
None.
11. Authors' Addresses
Dan Li
Huawei Technologies
F3-5-B R&D Center, Huawei Base
Shenzhen 518129 P.R.China
Phone: +86 755-289-71184
Email: danli@huawei.com
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Jianhua Gao
Huawei Technologies
F3-5-B R&D Center, Huawei Base
Shenzhen 518129 P.R.China
Phone: +86 755-289-73237
Email: gjhhit@huawei.com
Young Lee
Huawei Technologies
1700 Alma Drive, Suite 100
Plano, TX 75075 USA
Phone: +1 972-509-5599(x2240)
Email: ylee@huawei.com
Jianrui Han
Huawei Technologies
F3-5-B R&D Center, Huawei Base
Shenzhen 518129 P.R.China
Phone: +86 755-289-73234
Email: hanjianrui@huawei.com
Baoquan Rao
Huawei Technologies
F3-4-A R&D Center, Huawei Base
Shenzhen 518129 P.R.China
Phone: +86 755-289-73239
Email: raobaoquan@huawei.com
Xinghua Shi
Huawei Technologies
F3-4-A R&D Center, Huawei Base
Shenzhen 518129 P.R.China
Phone: +86 755-289-73238
Email: sxh@huawei.com
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12. Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on
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REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE
IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL
WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY
WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE
ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS
FOR A PARTICULAR PURPOSE.
13. Intellectual Property Statement
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Internet-Drafts are draft documents valid for a maximum of six
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