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Differences from draft-li-ccamp-grid-property-lmp-00.txt
Network Working Group Y. Li
Internet-Draft ZTE
Intended status: Standards Track R. Casellas
Expires: September 9, 2012 CTTC
Y. Wang
CATR
March 8, 2012
Link Management Protocol Extensions for Grid Property Negotiation
draft-li-ccamp-grid-property-lmp-01
Abstract
The recent updated version of ITU-T [G.694.1] has introduced the
flexible-grid DWDM technique, which provides a new tool that
operators can implement to provide a higher degree of network
optimization than is possible with fixed-grid systems. This document
describes the extensions to the Link Management Protocol (LMP) to
negotiate link grid property between the adjacent DWDM nodes before
the link is brought up.
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
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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 September 9, 2012.
Copyright Notice
Copyright (c) 2012 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
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(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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carefully, as they describe your rights and restrictions with respect
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions Used in This Document . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Flexi-fixed Grid Nodes Interworking . . . . . . . . . . . 4
3.2. Flexible-Grid Capability Negotiation . . . . . . . . . . . 5
3.3. Problem Summary . . . . . . . . . . . . . . . . . . . . . 6
4. LMP extensions . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Grid Property Subobject . . . . . . . . . . . . . . . . . 6
5. Messages Exchange Procedure . . . . . . . . . . . . . . . . . 8
5.1. Flexi-fixed Grid Nodes Messages Exchange . . . . . . . . . 8
5.2. Flexible Nodes Messages Exchange . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Normative references . . . . . . . . . . . . . . . . . . . 10
8.2. Informative References . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
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1. Introduction
The recent updated version of ITU-T [G.694.1] has introduced the
flexible-grid DWDM technique, which provides a new tool that
operators can implement to provide a higher degree of network
optimization than is possible with fixed-grid systems. A flexible-
grid network supports allocating an arbitrary spectral slot to a
channel. Mixed bitrate transmission systems can allocate their
channels with different spectral bandwidths/slot widths so that they
can be optimized for the bandwidth requirements of the particular
bitrate and modulation scheme of the individual channels. This
technique is regarded to be a promising way to improve the spectrum
utilization efficiency and fundamentally reduce the cost of the core
network.
During the practical deployment procedure, fixed-grid optical nodes
will be gradually replaced by flexible nodes. This will lead to an
interworking problem between fixed-grid DWDM and flexible-grid DWDM
nodes. Additionally, even two flexible-grid optical nodes may have
different grid properties, leading to link property conflict.
Therefore, this document describes the extensions to the Link
Management Protocol (LMP) to negotiate a link grid property between
two adjacent DWDM nodes before the link is brought up.
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 RFC 2119 [RFC2119].
2. Terminology
For the flexible DWDM grid, the allowed frequency slots have a
nominal central frequency (in THz) defined by:
193.1 + n * 0.00625
where n is a positive or negative integer including 0 and 0.00625 is
the nominal central frequency granularity in THz
and a slot width defined by:
12.5 * m
where m is a positive integer and 12.5 is the slot width granularity
in GHz. Any combination of frequency slots is allowed as long as no
two slots overlap.
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In this contribution, some other definitions are listed below:
Grid granularity: Grid granularity includes two elements: nominal
central frequency granularity and slot width granularity. The value
of slot width granularity is always configured to be twice of the
central frequency granularity, so that the spectral resources can be
allocated without leaving any gaps. Therefore, when grid granularity
appears alone, we just refer to the nominal central frequency
granularity.
Tuning range: In this draft we just refer to the tuning range of the
spectral bandwidth or slot width.
Channel spacing: In traditional fixed-grid network, the adjacent
channel spacing is constant. While for the flexible-grid network,
the adjacent channel spacing is determined by the two central
frequencies.
3. Problem Statement
3.1. Flexi-fixed Grid Nodes Interworking
+---+ +---+ +---+ +---+ +---+
| A |---------| B |=========| C |=========| D +--------+ E |
+---+ +---+ +---+ +---+ +---+
Figure 1
^ ^ ^ ^
------->|<----50GHz---->|<----50GHz---->|<----50GHz---->|<------
..... | | | | .....
+-------+-------+-------+-------+-------+--------+------+-------+-
n=-2 -1 0 1 2
Fixed channel spacing of 50 GHz (Node C)
^ ^ ^ ^
| | | |
--------+---------------+---------------+---------------+---------
..... | n=-8, m=4 | n=0, m=4 | n=8, m=4 | .....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
n=-16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16
|_|
Flexi-grid (Nodes B,D) 6.25 GHz
Central frequency granularity=6.25 GHz
Slot width granularity=12.5 GHz
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Figure 2
Figure 1 shows an example of interworking between flexible and fixed-
grid nodes. Nodes A, B, D, E support flexible-grid. All these nodes
can support frequency slots with a central frequency granularity of
6.25 GHz and slot width granularity of 12.5 GHz. Given the
flexibility in flexible-grid nodes, it is possible to configure the
nodes in such a way that the central frequencies and slot width
parameters are backwards compatible with the fixed DWDM grids
(adjacent flexible frequency slots with channel spacing of 8*6.25 and
slot width of 4*12.5 GHz is equivalent to fixed DWDM grids with
channel spacing of 50 GHz).
As node C can only support the fixed-grid DWDM property with channel
spacing of 50 GHz, to establish a LSP through node B,C,D, the links
between B to C and C to D must set to align with the fixed-grid
values. This link grid property must be negotiated before
establishing the LSP.
3.2. Flexible-Grid Capability Negotiation
+---+ +---+
| F +------------| G |
+---+ +---+
+------------------+-------------+-----------+
| Unit (GHz) | Node F | Node G |
+------------------+-------------+-----------+
| Grid granularity | 6.25 (12.5) | 12.5 (25) |
+------------------+-------------+-----------+
| Tuning range | [12.5, 100] | [25, 200] |
+------------------+-------------+-----------+
Figure 3
The updated version of ITU-T [G.694.1] has defined the flexible-grid
with 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 be able to support every
possible slot width. In other words, applications may be defined
where different grid granularity can be supported. Taking node F as
an example, an application could be defined where the nominal central
frequency granularity is 12.5 GHz requiring slot widths being
multiple of 25 GHz . Therefore the link between two optical nodes
with different grid granularity must be configured to align with the
larger of both granularities. Besides, different nodes may have
different slot width tuning ranges. For example, in figure 3, node F
can only support slot width with tuning change from 12.5 to 100 GHz,
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while node G supports tuning range from 25 GHz to 200 GHz. The link
property of slot width tuning range for the link between F and G
should be chosen as the range intersection, resulting in a range from
25 GHz to 100 GHz.
3.3. Problem Summary
In summary, in a DWDM Link between two nodes, the following
properties can be negotiated:
o Grid capability (channel spacing) --- Between fixed-grid and
flexible-grid nodes.
o Grid granularity --- Between two flexible-grid nodes.
o Slot width tuning range--- Between two flexible-grid nodes.
4. LMP extensions
4.1. Grid Property Subobject
According to [RFC4204], the LinkSummary message is used to verify the
consistency of the link property on both sides of the link before it
is brought up. The LinkSummary message contains negotiable and non-
negotiable DATA_LINK objects, carrying a series of variable-length
data items called subobjects, which illustrate the detailed link
properties. The subobjects are defined in Section 12.12.1 in
[RFC4204].
To solve the problems stated in section 3, this draft extends the LMP
protocol by introducing a new DATA_LINK subobject called "Grid
property", allowing the grid property correlation between adjacent
nodes. The encoding format of this new subobject 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 | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Grid | C.S. | Reserved | Min | Max |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type=TBD, Grid property type.
Grid:
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The value is used to represent which grid the node/interface
supports. Values defined in [RFC6205] identify DWDM [G.694.1] and
CWDM [G.694.2]. The value defined in
[I-D.farrkingel-ccamp-flexigrid-lambda-label] identifies flexible
DWDM.
+---------------+-------+
| Grid | Value |
+---------------+-------+
| Reserved | 0 |
+---------------+-------+
| ITU-T DWDM | 1 |
+---------------+-------+
| ITU-T CWDM | 2 |
+---------------+-------+
| Flexible DWDM | 3 |
+---------------+-------+
| Future use | 4-7 |
+---------------+-------+
C.S.:
For a fixed-grid node/interface, the C.S. value is used to represent
the channel spacing, as the spacing between adjacent channels is
constant. For a flexible-grid node/interface, this field should be
used to represent the central frequency granularity.
+------------+-------+
| C.S. (GHz) | Value |
+------------+-------+
| Reserved | 0 |
+------------+-------+
| 100 | 1 |
+------------+-------+
| 50 | 2 |
+------------+-------+
| 25 | 3 |
+------------+-------+
| 12.5 | 4 |
+------------+-------+
| 6.25 | 5 |
+------------+-------+
| Future use | 6-15 |
+------------+-------+
Min & Max:
The slot width tuning range the interface supports (indicated by the
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m value defined in section 2). For example, for slot width tuning
range from 25 GHz to 100 GHz (with regarding to a node with slot
width granularity of 12.5 GHz ), the values of Min and Max should be
2 and 8 respectively. For fixed-grid nodes, these two fields are
meaningless and should be set to zeros.
5. Messages Exchange Procedure
5.1. Flexi-fixed Grid Nodes Messages Exchange
To demonstrate the procedure of grid property correlation, the model
shown in Figure 1 is reused. Node B starts sending messages.
o After inspecting its own node/interface property, node B sends
node C a LinkSummary message including the MESSAGE ID, TE_LINK ID
and DATA_LINK objects. The setting and negotiating of MESSAGE ID
and TE_link ID can be referenced to [RFC4204]. As node B supports
flexible-grid property, the Grid and C.S. values in the grid
property subobject are set to be 3 and 5 respectively. The slot
width tuning range is from 12.5 GHz to 200 GHz. Meanwhile, the N
bit of the DATA_LINK object is set to 1, indicating that the
property is negotiable.
o When node C receives the LinkSummary message from B, it checks the
Grid, C.S., Min and Max values in the grid property subobject.
Node C can only support fixed-grid DWDM and realizes that the
flexible-grid property is not acceptable for the link. Since the
receiving N bit in the DATA_LINK object is set, indicating that
the Grid property of B is negotiable, node C responds to B with a
LinkSummaryNack containing a new Error_code object and state that
the property needs further negotiation. Meanwhile, an accepted
grid property subobject (Grid=2, C.S.=2, fixed DWDM with channel
spacing of 50 GHz) is carried in LinkSummaryNack message. At this
moment, the N bit in the DATA_LINK object is set to 0, indicating
that the grid property subobject is non-negotiable.
o As the channel spacing and slot width of node B can be configured
to be any integral multiples of 6.25 GHz and 12.5 GHz
respectively, node B supports the fixed DWDM values announced by
node C. Consequently, node B will resend the LinkSummary message
carrying the grid property subobject with values of Grid=2 and
C.S.=2.
o Once received the LinkSummary message from node B, node C replies
with a LinkSummaryACK message. After the message exchange, the
link between node B and C is brought up with a fixed channel
spacing of 50 GHz.
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In the above mentioned grid property correlation scenario, the node
supporting a flexible-grid is the one that starts sending LMP
messages. The procedure where the initiator is the fixed-grid node
is as follows:
o After inspecting its own interface property, Node C sends B a
LinkSummary message containing a grid property subobject with
Grid=2, C.S.=2. The N bit in the DATA_LINK object is set to 0,
indicating that it is non-negotiable.
o As the channel spacing and slot width of node B can be configured
to be any integral multiples of 6.25 GHz and 12.5 GHz
respectively, node B is able to support the fixed DWDM parameters.
Then, node B will make appropriate configuration and reply node C
the LinkSummaryACK message.
o After the message exchange, the link between node B and C is
brought up with a fixed channel spacing of 50 GHz.
5.2. Flexible Nodes Messages Exchange
To demonstrate the procedure of grid property correlation between to
flexi-grid capable nodes, the model shown in figure 3 is reused. The
procedure of grid property correlation (negotiating the grid
granularity and slot width tuning range) is similar to the scenarios
mentioned above.
o The Grid, C.S., Min and Max values in the grid property subobject
sent from node F to G are set to be 3,5,1,8 respectively.
Meanwhile, the N bit of the DATA_LINK object is set to 1,
indicating that the grid property is negotiable.
o When node G has received the LinkSummary message from F, it will
analyze the Grid, C.S., Min and Max values in the Grid property
subobject. But node G can only support grid granularity of 12.5
GHz and a slotwdith tuning range from 25 GHz to 200 GHz.
Considering the property of node F, node G then will respond F a
LinkSummaryNack containing a new Error_code object and state that
the property need further negotiation. Meanwhile, an accepted
grid property subobject (Grid=3, C.S.=4, Min=1, Max=4, the slot
width tuning range is set to the intersection of Node F and G) is
carried in LinkSummaryNack message. Meanwhile, the N bit in the
DATA_LINK object is set to 1, indicating that the grid property
subobject is non-negotiable.
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o As the channel spacing and slot width of node F can be configured
to be any integral multiples of 6.25 GHz and 12.5 GHz
respectively, node F can support the lager granularity. The
suggested slot width tuning range is acceptable for node F. In
consequence, node F will resend the LinkSummary message carrying
the grid subobject with values of Grid=3, C.S.=4, Min=1 and Max=4.
o Once received the LinkSummary message from node F, node G replies
with a LinkSummaryACK message. After the message exchange, the
link between node F and G is brought up supporting central
frequency granularity of 12.5 GHz and slot width tuning range from
25 GHz to 100 GHz.
From the perspective of the control plane, once the links have been
brought up, wavelength constraint information can be advertised and
the wavelength label can be assigned hop-by-hop when establishing a
LSP based on the link grid property.
6. IANA Considerations
TBD
7. Security Considerations
TBD
8. References
8.1. Normative references
[G.694.1] International Telecommunications Union, "Spectral grids
for WDM applications: DWDM frequency grid", Recommendation
G.694.1, June 2002 .
[G.694.2] International Telecommunications Union, "Spectral grids
for WDM applications: CWDM wavelength grid",
Recommendation G.694.2, December 2003 .
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4204] Lang, J., "Link Management Protocol (LMP)", RFC 4204,
October 2005.
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[RFC6205] Otani, T. and D. Li, "Generalized Labels for Lambda-
Switch-Capable (LSC) Label Switching Routers", RFC 6205,
March 2011.
8.2. Informative References
[I-D.farrkingel-ccamp-flexigrid-lambda-label]
King, D., Farrel, A., Li, Y., Zhang, F., and R. Casellas,
"Generalized Labels for the Flexi-Grid in Lambda-Switch-
Capable (LSC) Label Switching Routers",
draft-farrkingel-ccamp-flexigrid-lambda-label-01 (work in
progress), October 2011.
Authors' Addresses
Yao Li
ZTE
Email: li.yao3@zte.com.cn
Ramon Casellas
CTTC
Email: ramon.casellas@cttc.es
Yu Wang
China Academy of Telecom Research, MIIT
No.52 Huayuan Beilu, Haidian District,Beijing,P.R. China, 100083
Email: wangyu@mail.ritt.com.cn
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