Generalized Labels for the Flexi-Grid in Lambda Switch Capable (LSC) Label Switching Routers
RFC 7699
| Document | Type | RFC - Proposed Standard (November 2015) | |
|---|---|---|---|
| Authors | Adrian Farrel , Daniel King , Yao Li , Fatai Zhang | ||
| Last updated | 2018-12-20 | ||
| Replaces | draft-farrkingel-ccamp-flexigrid-lambda-label | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
GENART Last Call review
(of
-04)
by Robert Sparks
Ready w/nits
|
||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Daniele Ceccarelli | ||
| Shepherd write-up | Show Last changed 2015-07-27 | ||
| IESG | IESG state | RFC 7699 (Proposed Standard) | |
| Action Holders |
(None)
|
||
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | Deborah Brungard | ||
| Send notices to | (None) | ||
| IANA | IANA review state | IANA OK - Actions Needed | |
| IANA action state | RFC-Ed-Ack |
RFC 7699
Internet Engineering Task Force (IETF) A. Farrel
Request for Comments: 7699 D. King
Updates: 3471, 6205 Old Dog Consulting
Category: Standards Track Y. Li
ISSN: 2070-1721 Nanjing University
F. Zhang
Huawei Technologies
November 2015
Generalized Labels for the Flexi-Grid in
Lambda Switch Capable (LSC) Label Switching Routers
Abstract
GMPLS supports the description of optical switching by identifying
entries in fixed lists of switchable wavelengths (called grids)
through the encoding of lambda labels. Work within the ITU-T Study
Group 15 has defined a finer-granularity grid, and the facility to
flexibly select different widths of spectrum from the grid. This
document defines a new GMPLS lambda label format to support this
flexi-grid.
This document updates RFCs 3471 and 6205 by introducing a new label
format.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7699.
Farrel, et al. Standards Track [Page 1]
RFC 7699 GMPLS Labels for Flexi-Grid November 2015
Copyright Notice
Copyright (c) 2015 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
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions Used in This Document . . . . . . . . . . . . . 4
2. Overview of Flexi-Grid . . . . . . . . . . . . . . . . . . . . . 4
3. Fixed-Grid Lambda Label Encoding . . . . . . . . . . . . . . . . 5
4. Flexi-Grid Label Format and Values . . . . . . . . . . . . . . . 5
4.1. Flexi-Grid Label Encoding . . . . . . . . . . . . . . . . . 5
4.2. Considerations of Bandwidth . . . . . . . . . . . . . . . . 7
4.3. Composite Labels . . . . . . . . . . . . . . . . . . . . . 7
5. Manageability and Backward Compatibility Considerations . . . . 9
5.1. Control-Plane Backward Compatibility . . . . . . . . . . . 9
5.2. Manageability Considerations . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 10
7.1. Grid Subregistry . . . . . . . . . . . . . . . . . . . . . 10
7.2. DWDM Channel Spacing Subregistry . . . . . . . . . . . . . 11
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.1. Normative References . . . . . . . . . . . . . . . . . . . 11
8.2. Informative References . . . . . . . . . . . . . . . . . . 11
Appendix A. Flexi-Grid Example . . . . . . . . . . . . . . . . . . 13
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 14
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
Farrel, et al. Standards Track [Page 2]
RFC 7699 GMPLS Labels for Flexi-Grid November 2015
1. Introduction
As described in [RFC3945], GMPLS extends MPLS from supporting only
Packet Switch Capable (PSC) interfaces and switching, to also support
four new classes of interfaces and switching that include Lambda
Switch Capable (LSC).
A functional description of the extensions to MPLS signaling needed
to support this new class of interface and switching is provided in
[RFC3471].
Section 3.2.1.1 of [RFC3471] states that wavelength labels "only have
significance between two neighbors": global wavelength semantics are
not considered. [RFC6205] defines a standard lambda label format
that has a global semantic and is compliant with both the Dense
Wavelength Division Multiplexing (DWDM) grid [G.694.1] and the Coarse
Wavelength Division Multiplexing (CWDM) grid [G.694.2]. The terms
DWDM and CWDM are defined in [G.671].
A flexible-grid network selects its data channels as arbitrarily
assigned pieces of the spectrum. Mixed bitrate transmission systems
can allocate their channels with different spectral bandwidths so
that the channels can be optimized for the bandwidth requirements of
the particular bit rate and modulation scheme of the individual
channels. This technique is regarded as a promising way to improve
the network utilization efficiency and fundamentally reduce the cost
of the core network.
The "flexi-grid" has been developed within the ITU-T Study Group 15
to allow selection and switching of pieces of the optical spectrum
chosen flexibly from a fine-granularity grid of wavelengths with
variable spectral bandwidth [G.694.1].
[RFC3471] defines several basic label types including the lambda
label. Section 3.2.1.1 of [RFC3471] states that wavelength labels
"only have significance between two neighbors"; global wavelength
semantics are not considered. In order to facilitate
interoperability in a network composed of LSC equipment, [RFC6205]
defines a standard lambda label format and is designated an update of
RFC 3471.
This document continues the theme of defining global semantics for
the wavelength label by adding support for the flexi-grid. Thus,
this document updates [RFC6205] and [RFC3471].
This document relies on [G.694.1] for the definition of the optical
data plane and does not make any updates to the work of the ITU-T.
Farrel, et al. Standards Track [Page 3]
RFC 7699 GMPLS Labels for Flexi-Grid November 2015
1.1. 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].
2. Overview of Flexi-Grid
[G.694.1] defines DWDM fixed grids. The latest version of that
document extends the DWDM fixed grids to add support for flexible
grids. The basis of the work is to allow a data channel to be formed
from an abstract grid anchored at 193.1 THz and selected on a channel
spacing of 6.25 GHz with a variable slot width measured in units of
12.5 GHz. Individual allocations may be made on this basis from
anywhere in the spectrum, subject to allocations not overlapping.
[G.694.1] provides clear guidance on the support of flexible grid by
implementations in Section 2 of Appendix I:
The flexible DWDM grid defined in clause 7 has a nominal central
frequency granularity of 6.25 GHz and a slot width granularity of
12.5 GHz. However, devices or applications that make use of the
flexible grid may not have to be capable of supporting every
possible slot width or position. In other words, applications may
be defined where only a subset of the possible slot widths and
positions are required to be supported.
For example, an application could be defined where the nominal
central frequency granularity is 12.5 GHz (by only requiring
values of n that are even) and that only requires slot widths as a
multiple of 25 GHz (by only requiring values of m that are even).
Some additional background on the use of GMPLS for flexible grids can
be found in [RFC7698].
2.1. Composite Labels
It is possible to construct an end-to-end connection as a composite
of more than one flexi-grid slot. The mechanism used in GMPLS is
similar to that used to support inverse multiplexing familiar in
time-division multiplexing (TDM) and optical transport networks
(OTNs). The slots in the set could potentially be contiguous or non-
contiguous (only as allowed by the definitions of the data plane) and
could be signaled as a single LSP or constructed from a group of
LSPs. For more details, refer to Section 4.3.
How the signal is carried across such groups of channels is out of
scope for this document.
Farrel, et al. Standards Track [Page 4]
RFC 7699 GMPLS Labels for Flexi-Grid November 2015
3. Fixed-Grid Lambda Label Encoding
[RFC6205] defines an encoding for a global semantic for a DWDM label
based on four fields:
- Grid: used to select which grid the lambda is selected from.
Values defined in [RFC6205] identify DWDM [G.694.1] and CWDM
[G.694.2].
- C.S. (Channel Spacing): used to indicate the channel spacing.
[RFC6205] defines values to represent spacing of 100, 50, 25, and
12.5 GHz.
- Identifier: a local-scoped integer used to distinguish different
lasers (in one node) when they can transmit the same frequency
lambda.
- n: a two's-complement integer to take a positive, negative, or
zero value. This value is used to compute the frequency as
defined in [RFC6205] and based on [G.694.1]. The use of n is
repeated here for ease of reading the rest of this document: in
case of discrepancy, the definition in [RFC6205] is normative.
Frequency (THz) = 193.1 THz + n * frequency granularity (THz)
where the nominal central frequency granularity for the flexible
grid is 0.00625 THz
4. Flexi-Grid Label Format and Values
4.1 Flexi-Grid Label Encoding
This document defines a generalized label encoding for use in flexi-
grid systems. As with the other GMPLS lambda label formats defined
in [RFC3471] and [RFC6205], the use of this label format is known a
priori. That is, since the interpretation of all lambda labels is
determined hop by hop, the use of this label format requires that all
nodes on the path expect to use this label format.
For convenience, however, the label format is modeled on the fixed-
grid label defined in [RFC6205] and briefly described in Section 3.
Figure 1 shows the format of the Flexi-Grid Label. It is a 64-bit
label.
Farrel, et al. Standards Track [Page 5]
RFC 7699 GMPLS Labels for Flexi-Grid November 2015
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. | Identifier | n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| m | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1 : The Flexi-Grid Label Encoding
This document defines a new Grid value to supplement those in
[RFC6205]:
+----------+---------+
| Grid | Value |
+----------+---------+
|ITU-T Flex| 3 |
+----------+---------+
Within the fixed-grid network, the C.S. value is used to represent
the channel spacing, as the spacing between adjacent channels is
constant. For the flexible-grid situation, this field is used to
represent the nominal central frequency granularity.
This document defines a new C.S. value to supplement those in
[RFC6205]:
+------------+---------+
| C.S. (GHz) | Value |
+------------+---------+
| 6.25 | 5 |
+------------+---------+
The meaning of the Identifier field is maintained from [RFC6205] (see
also Section 3).
The meaning of n is maintained from [RFC6205] (see also Section 3).
The m field is used to identify the slot width according to the
formula given in [G.694.1] as follows. It is a 16-bit integer value
encoded in line format.
Slot Width (GHz) = 12.5 GHz * m
The Reserved field MUST be set to zero on transmission and SHOULD be
ignored on receipt.
Farrel, et al. Standards Track [Page 6]
RFC 7699 GMPLS Labels for Flexi-Grid November 2015
An implementation that wishes to use the flexi-grid label encoding
MUST follow the procedures of [RFC3473] and of [RFC3471] as updated
by [RFC6205]. It MUST set Grid to 3 and C.S. to 5. It MUST set
Identifier to indicate the local identifier of the laser in use as
described in [RFC6205]. It MUST also set n according to the formula
in Section 3 (inherited unchanged from [RFC6205]). Finally, the
implementation MUST set m as described in the formula stated above.
4.2. Considerations of Bandwidth
There is some overlap between the concepts of bandwidth and label in
many GMPLS-based systems where a label indicates a physical switching
resource. This overlap is increased in a flexi-grid system where a
label value indicates the slot width and so affects the bandwidth
supported by an LSP. Thus, the m parameter is both a property of the
label (i.e., it helps define exactly what is switched) and of the
bandwidth.
In GMPLS signaling [RFC3473], bandwidth is requested in the
SENDER_TSPEC object and confirmed in the FLOWSPEC object. The m
parameter, which is a parameter of the GMPLS flexi-grid label as
described above, is also a parameter of the flexi-grid Tspec and
Flowspec as described in [FLEXRSVP].
4.3. Composite Labels
The creation of a composite of multiple channels to support inverse
multiplexing is already supported in GMPLS for TDM and OTN (see
[RFC4606], [RFC6344], and [RFC7139]). The mechanism used for flexi-
grid is similar.
To signal an LSP that uses multiple flexi-grid slots, a "compound
label" is constructed. That is, the LABEL object is constructed from
a concatenation of the 64-bit Flexi-Grid Labels shown in Figure 1.
The number of elements in the label can be determined from the length
of the LABEL object. The resulting LABEL object is shown in Figure 2
including the object header that is not normally shown in
diagrammatic representations of RSVP-TE objects. Note that r is the
count of component labels, and this is backward compatible with the
label shown in Figure 1 where the value of r is 1.
The component labels MUST be presented in increasing order of the
value n. Implementations MUST NOT infer anything about the encoding
of a signal into the set of slots represented by a compound label
from the label itself. Information about the encoding MAY be handled
in other fields in signaling messages or through an out-of-band
system, but such considerations are outside the scope of this
document.
Farrel, et al. Standards Track [Page 7]
RFC 7699 GMPLS Labels for Flexi-Grid November 2015
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Object Length (4 + 8r) | Class-Num (16)| C-Type (2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Grid | C.S. | Identifier | n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| m | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Grid | C.S. | Identifier | n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| m | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2 : A Compound Label for Virtual Concatenation
Note that specific rules must be applied as follows:
- Grid MUST show "ITU-T Flex" value 3 in each component label.
- C.S. MUST have the same value in each component label.
- Identifier in each component label may identify different physical
equipment.
- Values of n and m in each component label define the slots that
are concatenated.
At the time of writing, [G.694.1] only supports only groupings of
adjacent slots (i.e., without intervening unused slots that could be
used for other purposes) of identical width (same value of m), and
the component slots must be in increasing order of frequency (i.e.,
increasing order of the value n). The mechanism defined here MUST
NOT be used for other forms of grouping unless and until those forms
are defined and documented in Recommendations published by the ITU-T.
Note further that while the mechanism described here naturally means
that all component channels are corouted, a composite channel can
also be achieved by constructing individual LSPs from single flexi-
grid slots and managing those LSPs as a group. A mechanism for
achieving this for TDM is described in [RFC6344], but is out of scope
for discussion in this document because the labels used are normal,
single-slot labels and require no additional definitions.
Farrel, et al. Standards Track [Page 8]
RFC 7699 GMPLS Labels for Flexi-Grid November 2015
5. Manageability and Backward Compatibility Considerations
This section briefly considers issues of manageability and backward
compatibility.
5.1. Control-Plane Backward Compatibility
Labels are carried in two ways in GMPLS: for immediate use on the
next hop and for use at remote hops.
It is an assumption of GMPLS that both ends of a link know what label
types are supported and only use appropriate label types. If a label
of an unknown type is received, it will be processed as if it was of
a known type since the Label Object and similar label-carrying
objects do not contain a type identifier. Thus, the introduction of
a flexi-grid label in this document does not change the compatibility
issues, and a legacy node that does not support the new flexi-grid
label should not expect to receive or handle such labels. If one is
incorrectly used in communication with a legacy node, it will attempt
to process it as an expected label type with a potentially poor
outcome.
It is possible that a GMPLS message transitting a legacy node will
contain a flexi-grid label destined for or reported by a remote node.
For example, an LSP that transits links of different technologies
might record flexi-grid labels in a Record Route Object that is
subsequently passed to a legacy node. Such labels will not have any
impact on legacy implementations except as noted in the manageability
considerations in the next section.
5.2. Manageability Considerations
This document introduces no new elements for management. That is,
labels can continue to be used in the same way by the GMPLS protocols
and where those labels were treated as opaque quantities with local
or global significance, no change is needed to the management
systems.
However, this document introduces some changes to the nature of a
label that may require changes to management systems. Although
Section 3.2 of [RFC3471] makes clear that a label is of variable
length according to the type and that the type is supposed to be
known a priori by both ends of a link, a management system is not
guaranteed to be updated in step with upgrades or installations of
new flexi-grid functionality in the network.
Farrel, et al. Standards Track [Page 9]
RFC 7699 GMPLS Labels for Flexi-Grid November 2015
But, an implementation expecting a 32-bit lambda label would not fail
ungracefully because the first 32 bits follow the format of
[RFC6205]. It would look at theses labels and read but not recognize
the new grid type value. It would then give up trying to parse the
label and (presumably) the whole of the rest of the message.
The management system can be upgraded in two steps:
- Firstly, systems that handle lambda labels as 32-bit quantities
need to be updated to handle the increased length (64 bits) of
labels as described in this document. These "unknown" 64-bit
labels could be displayed as opaque 64-bit quantities and still
add a lot of value for the operator (who might need to parse the
label by hand). However, an implementation that already supports
lambda labels as defined in [RFC6205] can safely continue to
process the first 32 bits and display the fields defined in RFC
6205 as before, leaving just the second 32 bits as opaque data.
- Second, a more sophisticated upgrade to a management system would
fully parse the flexi-grid labels and display them field by field
as described in this document.
6. Security Considerations
[RFC6205] notes that the definition of a new label encoding does not
introduce any new security considerations to [RFC3471] or [RFC3473].
That statement applies equally to this document.
For a general discussion on MPLS and GMPLS-related security issues,
see the MPLS/GMPLS security framework [RFC5920].
7. IANA Considerations
IANA maintains the "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Parameters" registry that contains several
subregistries.
7.1. Grid Subregistry
IANA has allocated a new entry in this subregistry as follows:
Value Grid Reference
----- ------------------------- ----------
3 ITU-T Flex RFC 7699
Farrel, et al. Standards Track [Page 10]
RFC 7699 GMPLS Labels for Flexi-Grid November 2015
7.2. DWDM Channel Spacing Subregistry
IANA has allocated a new entry in this subregistry as follows:
Value Channel Spacing (GHz) Reference
----- ------------------------- ----------
5 6.25 RFC 7699
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3471] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description",
RFC 3471, DOI 10.17487/RFC3471, January 2003,
<http://www.rfc-editor.org/info/rfc3471>.
[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
DOI 10.17487/RFC3473, January 2003,
<http://www.rfc-editor.org/info/rfc3473>.
[RFC6205] Otani, T., Ed., and D. Li, Ed., "Generalized Labels for
Lambda-Switch-Capable (LSC) Label Switching Routers",
RFC 6205, DOI 10.17487/RFC6205, March 2011,
<http://www.rfc-editor.org/info/rfc6205>.
[G.694.1] International Telecommunication Union, "Spectral grids for
WDM applications: DWDM frequency grid", ITU-T
Recommendation G.694.1, February 2012,
<https://www.itu.int/rec/T-REC-G.694.1/en>.
8.2. Informative References
[RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", RFC 3945,
DOI 10.17487/RFC3945, October 2004,
<http://www.rfc-editor.org/info/rfc3945>.
Farrel, et al. Standards Track [Page 11]
RFC 7699 GMPLS Labels for Flexi-Grid November 2015
[RFC4606] Mannie, E. and D. Papadimitriou, "Generalized Multi-
Protocol Label Switching (GMPLS) Extensions for
Synchronous Optical Network (SONET) and Synchronous
Digital Hierarchy (SDH) Control", RFC 4606,
DOI 10.17487/RFC4606, August 2006,
<http://www.rfc-editor.org/info/rfc4606>.
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
<http://www.rfc-editor.org/info/rfc5920>.
[RFC6344] Bernstein, G., Ed., Caviglia, D., Rabbat, R., and H. van
Helvoort, "Operating Virtual Concatenation (VCAT) and the
Link Capacity Adjustment Scheme (LCAS) with Generalized
Multi-Protocol Label Switching (GMPLS)", RFC 6344,
DOI 10.17487/RFC6344, August 2011,
<http://www.rfc-editor.org/info/rfc6344>.
[RFC7139] Zhang, F., Ed., Zhang, G., Belotti, S., Ceccarelli, D.,
and K. Pithewan, "GMPLS Signaling Extensions for Control
of Evolving G.709 Optical Transport Networks", RFC 7139,
DOI 10.17487/RFC7139, March 2014,
<http://www.rfc-editor.org/info/rfc7139>.
[RFC7698] Gonzalez de Dios, O., Ed., Casellas, R., Ed., Zhang, F.,
Fu., X., Ceccarelli, D., and I. Hussain, "Framework and
Requirements for GMPLS-Based Control of Flexi-Grid Dense
Wavelength Division Multiplexing (DWDM) Networks",
RFC 7698, DOI 10.17487/RFC7698, November 2015,
<http://www.rfc-editor.org/info/rfc7698>.
[G.671] International Telecommunication Union, "Transmission
characteristics of optical components and subsystems",
ITU-T Recommendation G.671, February 2012,
<https://www.itu.int/rec/T-REC-G.671/en>.
[G.694.2] International Telecommunication Union, "Spectral grids for
WDM applications: CWDM wavelength grid", ITU-T
Recommendation G.694.2, December 2003,
<https://www.itu.int/rec/T-REC-G.694.2/en>.
[FLEXRSVP] Zhang, F., Zhang, X., Farrel, A., Gonzalez de Dios, O.,
and D. Ceccarelli, "RSVP-TE Signaling Extensions in
support of Flexible Grid", Work in Progress, draft-ietf-
ccamp-flexible-grid-rsvp-te-ext-03, August 2015.
Farrel, et al. Standards Track [Page 12]
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Appendix A. Flexi-Grid Example
Consider a fragment of an optical LSP between node A and node B using
the flexible grid. Suppose that the LSP on this hop is formed:
- using the ITU-T Flexi-Grid
- the nominal central frequency of the slot is 193.05 THz
- the nominal central frequency granularity is 6.25 GHz
- the slot width is 50 GHz.
In this case, the label representing the switchable quantity that is
the flexi-grid quantity is encoded as described in Section 4.1 with
the following parameter settings. The label can be used in signaling
or in management protocols to describe the LSP.
Grid = 3 : ITU-T Flexi-Grid
C.S. = 5 : 6.25 GHz nominal central frequency granularity
Identifier = local value indicating the laser in use
n = -8 :
Frequency (THz) = 193.1 THz + n * frequency granularity (THz)
193.05 (THz) = 193.1 (THz) + n * 0.00625 (THz)
n = (193.05 - 193.1) / 0.00625 = -8
m = 4 :
Slot Width (GHz) = 12.5 GHz * m
50 (GHz) = 12.5 (GHz) * m
m = 50 / 12.5 = 4
Farrel, et al. Standards Track [Page 13]
RFC 7699 GMPLS Labels for Flexi-Grid November 2015
Acknowledgments
This work was supported in part by the FP-7 IDEALIST project under
grant agreement number 317999.
Very many thanks to Lou Berger for discussions of labels of more than
32 bits. Many thanks to Sergio Belotti and Pietro Vittorio Grandi
for their support of this work. Thanks to Gabriele Galimberti for
discussion of the size of the "m" field, and to Iftekhar Hussain for
discussion of composite labels. Robert Sparks, Carlos Pignataro, and
Paul Wouters provided review comments during IETF Last Call.
The Vancouver 2012 Pool Party drove early discussions and rough
consensus. It comprised: Dieter Beller, Ramon Casellas, Daniele
Ceccarelli, Oscar Gonzalez de Dios, Iftekhar Hussain, Cyril Margaria,
Lyndon Ong, Fatai Zhang, and Adrian Farrel.
Contributors
Zhang Fei
Huawei Technologies
Email: zhangfei7@huawei.com
Ramon Casellas
CTTC
Email: ramon.casellas@cttc.es
Authors' Addresses
Adrian Farrel
Old Dog Consulting
Email: adrian@olddog.co.uk
Daniel King
Old Dog Consulting
Email: daniel@olddog.co.uk
Yao Li
Nanjing University
Email: wsliguotou@hotmail.com
Fatai Zhang
Huawei Technologies
Email: zhangfatai@huawei.com
Farrel, et al. Standards Track [Page 14]