Network Working Group Tomohiro Otani
Internet Draft Takehiro Tsuritani
Updates: RFC3471 KDDI
Category: Standards Track Dan Li
Huawei
Expires: June 2010 December 7, 2009
Generalized Labels for Lambda-Switching Capable Label Switching
Routers
draft-ietf-ccamp-gmpls-g-694-lambda-labels-05.txt
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Abstract
Technology in the optical domain is constantly evolving and as a
consequence new equipment providing lambda switching capability has
been developed and is currently being deployed. However, [RFC3471]
has defined that a wavelength label (section 3.2.1.1) "only has
significance between two neighbors" and global wavelength continuity
is not considered. In order to achieve interoperability in a network
composed of next generation lambda switch-capable equipment, this
document defines a standard lambda label format, being compliant
with either [G.694.1](DWDM-grid) or [G.694.2](CWDM-grid). Moreover
some consideration on how to ensure lambda continuity with RSVP-TE
is provided. This document is a companion to the Generalized Multi-
Protocol Label Switching (GMPLS) signaling. It defines the label
format when Lambda Switching is requested in an all optical network.
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].
Table of Contents
1. Introduction..................................................2
2. Assumed network model and related problem statement...........3
3. Label Related Formats.........................................6
3.1. Wavelength Labels........................................6
3.2. DWDM Wavelength Label....................................7
3.3. CWDM Wavelength Label....................................8
4. Security Considerations.......................................9
5. IANA Considerations...........................................9
6. Acknowledgments..............................................10
7. References...................................................10
7.1. Normative References....................................10
7.2. Informative References..................................10
8. Author's Address.............................................11
9. Appendix A. DWDM Example.....................................12
10. Appendix B. CWDM Example....................................12
1. Introduction
As described in [RFC3945], Generalized MPLS (GMPLS) extends MPLS
from supporting only packet (Packet Switching Capable - PSC)
interfaces and switching to also include support for four new
classes of interfaces and switching:
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o Layer-2 Switch Capable (L2SC)
o Time-Division Multiplex (TDM)
o Lambda Switch Capable (LSC)
o Fiber-Switch Capable (FSC).
A functional description of the extensions to MPLS signaling needed
to support new classes of interfaces and switching is provided in
[RFC3471].
This document presents details that are specific to the use of GMPLS
with a new generation of Lambda Switch Capable (LSC) equipment.
Technologies such as Reconfigurable Optical Add/Drop Multiplex (ROADM)
and Wavelength Cross-Connect (WXC) operate at the wavelength
switching level. As such, the wavelength is important information
that is necessary to set up a wavelength-based LSP appropriately and
the wavelength defined in [G.694.1] or [G.694.2] is widely utilized.
2. Assumed network model and related problem statement
Figure 1 depicts an all-optically switched network consisting of
different vendor's optical network domains. Vendor A's network
consists of ROADM or WXC, and vendor B's network consists of number
of photonic cross-connect (PXC) and Dense wavelength division
multiplexing (DWDM) multiplexer & demultiplexer, otherwise both
vendors' networks might be based on the same technology.
In this case, the use of standardized wavelength label information is
quite significant to establish a wavelength-based LSP. It is also an
important constraint when conducting CSPF calculation for RSVP-TE
signaling. The way the Constrained Shortest Path First (CSPF) is
performed is outside the scope of this document.
It is needless to say, a LSP must be appropriately provisioned
between a selected pair of ports not only within Domain A but also
over multiple domains satisfying wavelength constraints.
Figure 2 illustrates in detail the interconnection between Domain A
and Domain B.
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|
Domain A (or Vendor A) | Domain B (or Vendor B)
|
Node-1 Node-2 | Node-6 Node-7
+--------+ +--------+ | +-------+ +-+ +-+ +-------+
| ROADM | | ROADM +---|------+ PXC +-+D| |D+-+ PXC |
| or WXC +========+ or WXC +---|------+ +-+W+=====+W+-+ |
| (LSC) | | (LSC) +---|------+ (LSC) +-+D| |D+-+ (LSC) |
+--------+ +--------+ | | +-|M| |M+-+ |
|| || | +++++++++ +-+ +-+ +++++++++
|| Node-3 || | ||||||| |||||||
|| +--------+ || | +++++++++ +++++++++
||===| WXC +===|| | | DWDM | | DWDM |
| (LSC) | | +--++---+ +--++---+
||===+ +===|| | || ||
|| +--------+ || | +--++---+ +--++---+
|| || | | DWDM | | DWDM |
+--------+ +--------+ | +++++++++ +++++++++
| ROADM | | ROADM | | ||||||| |||||||
| or WXC +========+ or WXC +=+ | +-+ +++++++++ +-+ +-+ +++++++++
| (LSC) | | (LSC) | | | |D|-| PXC +-+D| |D+-+ PXC |
+--------+ +--------+ +=|==+W|-| +-+W+=====+W+-+ |
Node-4 Node-5 | |D|-| (LSC) +-+D| |D+-+ (LSC) |
| |M|-| +-+M| |M+-+ |
| +-+ +-------+ +-+ +-+ +-------+
| Node-8 Node-9
Figure 1 Wavelength-based network model
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+-------------------------------------------------------------+
| Domain A | Domain B |
| | |
| +---+ lambda 1 | +---+ |
| | |---------------|---------| | |
| WDM | N | lambda 2 | | N | WDM |
| =====| O |---------------|---------| O |===== |
| O | D | . | | D | O |
| T WDM | E | . | | E | WDM T |
| H =====| 2 | lambda n | | 6 |===== H |
| E | |---------------|---------| | E |
| R +---+ | +---+ R |
| | |
| N +---+ | +---+ N |
| O | | | | | O |
| D WDM | N | | | N | WDM D |
| E =====| O | WDM | | O |===== E |
| S | D |=========================| D | S |
| WDM | E | | | E | WDM |
| =====| 5 | | | 8 |===== |
| | | | | | |
| +---+ | +---+ |
+-------------------------------------------------------------+
Figure 2 Interconnecting details between two domains
In the scenario of Figure 1, consider the setting up of a
bidirectional LSP from ingress switch 1 to egress switch 9. In order
to satisfy wavelength continuity constraint, a fixed wavelength
(lambda 1) needs to be used in domain A and domain B. A Path message
will be used for the signaling, the PATH message must contain the
upstream label and a label set object; both containing the same
lambda. The label set object is made by only one sub channel that
must be same as the upstream label. The path setup will continue
downstream to switch 9 by configuring each lambda switch based on the
wavelength label. This label allows the correct switching of lambda
switches and the label contents needs to be used over the inter-
domain. As same above, the path setup will continue downstream to
switch 9 by configuring lambda switch based on multiple wavelength
labels. If the node has a tunable wavelength transponder, the tuning
wavelength is considered as a part of wavelength switching operation.
Not using a standardized label would add undue burden on the operator
to enforce policy as each manufacturer may decide on a different
representation and therefore each domain may have its own label
formats. Moreover, manual provisioning may lead to misconfiguration
if domain-specific labels are used.
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Therefore, a wavelength label should be standardized in order to
allow interoperability between multiple domains; otherwise
appropriate existing labels are identified in support of wavelength
availability. As identical wavelength information, the ITU-T
frequency grid specified in [G.694.1] for Dense WDM (DWDM) and
wavelength information in [G.694.2] for Coarse WDM (CWDM) are used by
LSRs and should be followed as a wavelength label.
3. Label Related Formats
To deal with the widening scope of MPLS into the optical and time
domains, several new forms of "label" have been defined in [RFC3471].
This section contains clarifications for the Wavelength label based
on [G.694.1] or [G.694.2] and Label Set definition specific for LSC
LSRs.
3.1. Wavelength Labels
In section 3.2.1.1 of [RFC3471], a Wavelength label is defined to
have significance between two neighbors, and the receiver may need to
convert the received value into a value that has local significance.
LSC equipment uses multiple wavelengths controlled by a single
control channel. In such case, the label indicates the wavelength to
be used for the LSP. This document proposes to standardize the
wavelength label. As an example of wavelength values, the reader is
referred to [G.694.1] which lists the frequencies from the ITU-T DWDM
frequency grid. The same can be done for CWDM technology by using
the wavelength defined in [G.694.2]. In that sense, we can call
wavelength labels.
Since the ITU-T DWDM grid is based on nominal central frequencies, we
need to indicate the appropriate table, the channel spacing in the
grid and a value n that allows the calculation of the frequency. That
value can be positive or negative.
The frequency is calculated as such in [G.694.1]:
Frequency (THz) = 193.1 THz + n * channel spacing (THz)
, where n is a two's-complement integer (positive, negative or 0) and
channel spacing is defined to be 0.0125, 0.025, 0.05 or 0.1 THz. When
wider channel spacing such as 0.2 THz is utilized, the combination of
narrower channel spacing and the value n can provide proper frequency
with that channel spacing. Channel spacing is not utilized to
indicate the LSR capability but only to specify a frequency in
signaling.
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For the other example of the case of the ITU-T CWDM grid, the spacing
between different channels was defined to be 20nm, so we need to pass
the wavelength value in nm in this case. Examples of CWDM wavelengths
are 1471, 1491, etc. nm.
The wavelength is calculated as follows
Wavelength (nm) = 1471 nm + n * 20 nm
, where n is a two's-complement integer (positive, negative or 0).
The grids listed in [G.694.1] and [G.694.2] are not numbered and
change with the changing frequency spacing as technology advances, so
an index is not appropriate in this case.
3.2. DWDM Wavelength Label
For the case of DWDM, the information carried in a Wavelength label
is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Grid | C.S | Reserved | n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) Grid: 3 bits
The value for grid is set to 1 for ITU-T DWDM Grid as defined in
[G.694.1].
+----------+---------+
| Grid | Value |
+----------+---------+
| Reserved | 0 |
+----------+---------+
|ITU-T DWDM| 1 |
+----------+---------+
|ITU-T CWDM| 2 |
+----------+---------+
|Future use| 3 - 7 |
+----------+---------+
(2) C.S.(channel spacing): 4 bits
DWDM channel spacing is defined as follows.
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+----------+---------+
| C.S(GHz) | Value |
+----------+---------+
| Reserved | 0 |
+----------+---------+
| 100 | 1 |
+----------+---------+
| 50 | 2 |
+----------+---------+
| 25 | 3 |
+----------+---------+
| 12.5 | 4 |
+----------+---------+
|Future use| 5 - 15 |
+----------+---------+
(3) n: 16 bits
n is a two's-complement integer to take either a negative, zero or a
positive value. The value used to compute the frequency as shown
above.
3.3. CWDM Wavelength Label
For the case of CWDM, the information carried in a Wavelength label
is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Grid | C.S | Reserved | n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The structure of the label in the case of CWDM is the same as that of
DWDM case.
(1) Grid: 3 bits
The value for grid is set to 2 for ITU-T CWDM Grid as defined in
[G.694.2].
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+----------+---------+
| Grid | Value |
+----------+---------+
| Reserved | 0 |
+----------+---------+
|ITU-T DWDM| 1 |
+----------+---------+
|ITU-T CWDM| 2 |
+----------+---------+
|Future use| 3 - 7 |
+----------+---------+
(2) C.S.(channel spacing): 4 bits
CWDM channel spacing is defined as follows.
+----------+---------+
| C.S(nm) | Value |
+----------+---------+
| Reserved | 0 |
+----------+---------+
| 20 | 1 |
+----------+---------+
|Future use| 2 - 15 |
+----------+---------+
(3) n: 16 bits
n is a two's-complement integer. The value used to compute the
wavelength as shown above.
We do not need to define a new type as the information stored is
either a port label or a wavelength label. Only the wavelength label
as above needs to be defined.
4. Security Considerations
This document introduces no new security considerations to [RFC3473].
GMPLS security is described in section 11 of [RFC3471] and refers to
[RFC3209] for RSVP-TE.
5. IANA Considerations
This document has no actions for IANA.
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6. Acknowledgments
The authors would like to thank Adrian Farrel, Lawrence Mao, Zafar
Ali and Daniele Ceccarelli for the discussion and their comments.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching
(MPLS) Signaling Functional Description", RFC 3471,
January 2003.
[RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching
(MPLS) Signaling - Resource ReserVation Protocol Traffic
Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.
[RFC3945] Mannie, E., Ed., "Generalized Multiprotocol Label Switching
(GMPLS) Architecture", RFC 3945, October 2004.
7.2. Informative References
[G.694.1] ITU-T Recommendation G.694.1, "Spectral grids for WDM
applications: DWDM frequency grid", June 2002.
[G.694.2] ITU-T Recommendation G.694.2, "Spectral grids for WDM
applications: CWDM wavelength grid", December 2003.
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8. Author's Address
Tomohiro Otani
KDDI Corporation
2-3-2 Nishishinjuku Shinjuku-ku Tokyo, 163-8003, Japan
Phone: +81-3-3347-6006
Email: tm-otani@kddi.com
Takehiro Tsuritani
KDDI R&D Laboratories Inc.
2-1-15 Ohara Fujimino-shi Saitama, 356-8502, Japan
Phone: +81-49-278-7806
Email: tsuri@kddilabs.jp
Dan Li
Huawei Technologies
F3-5-B R&D Center, Huawei Base,
Shenzhen 518129 China
Phone: +86 755-289-70230
Email: danli@huawei.com
Richard Rabbat
Google, Inc.
1600 Amphitheatre Pkwy
Mountain View, CA 94043
Email: rabbat@alum.mit.edu
Sidney Shiba
Email: sidney.shiba@yahoo.com
Hongxiang Guo
Email: hongxiang.guo@gmail.com
Keiji Miyazaki
Fujitsu Laboratories Ltd
4-1-1 Kotanaka Nakahara-ku, Kawasaki Kanagawa, 211-8588, Japan
Phone: +81-44-754-2765
Email: miyazaki.keiji@jp.fujitsu.com
Diego Caviglia
Ericsson
16153 Genova Cornigliano, ITALY
Phone: +390106003736
Email: diego.caviglia@ericsson.com
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9. Appendix A. DWDM Example
Considering the network displayed in figure 1 it is possible to show
an example of LSP set up using the lambda labels.
Node 1 receives the request for establishing an LSP from itself to
Node 9. The ITU-T grid to be used is the DWDM one, the channel
spacing is 50Ghz and the wavelength to be used is 193,35 THz.
Node 1 signals the LSP via a Path message including a Wavelength
Label structured as defined in section 4.2:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Grid | C.S | Reserved | n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where:
Grid = 1 : ITU-T DWDM grid
C.S. = 2 : 50 GHz channel spacing
n = 5 :
Frequency (THz) = 193.1 THz + n * channel spacing (THz)
193.35 (THz) = 193.1 (THz) + n* 0.05 (THz)
n = (193.35-193.1)/0.05 = 5
10. Appendix B. CWDM Example
The network displayed in figure 1 can be used also to display an
example of signaling using the Wavelength Label in a CWDM environment.
This time the signaling of an LSP from Node 4 to Node 7 is considered.
Such LSP exploits the CWDM ITU-T grid with a 20nm channel spacing and
is to established using wavelength equal to 1331 nm.
Node 4 signals the LSP via a Path message including a Wavelength
Label structured as defined in section 4.3:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Grid | C.S | Reserved | n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where:
Grid = 2 : ITU-T CWDM grid
C.S. = 1 : 20 nm channel spacing
n = -7 :
Wavelength (nm) = 1471 nm + n * 20 nm
1331 (nm) = 1471 (nm) + n * 20 nm
n = (1331-1471)/20 = -7
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