Internet DRAFT - draft-wangl-ccamp-ospf-ext-constraint-flexi-grid
draft-wangl-ccamp-ospf-ext-constraint-flexi-grid
Network Working Group L. Wang
Internet-Draft Y. Li
Intended status: Standards Track ZTE
Expires: January 17, 2013 GY. Zhang
China Academy of Telecom
Research, MIIT
July 16, 2012
OSPF Extensions for Routing Constraint Encoding in Flexible-Grid
Networks
draft-wangl-ccamp-ospf-ext-constraint-flexi-grid-02
Abstract
In Flexible-Grid networks, network elements and links may impose
additional routing constraints, which cannot be ignored in Routing
and Spectrum Assignment (RSA) process. This document describes the
requirements of such constraints, and then provides efficient
encodings to specify how the information is carried.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
3. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Requirements of Routing Constraint for RSA in
Flexible-Grid Networks . . . . . . . . . . . . . . . . . . . . 4
4.1. Label set . . . . . . . . . . . . . . . . . . . . . . . . 8
4.2. Flexible-Grid Ability Constraint . . . . . . . . . . . . . 8
4.3. Optical Signal Compatibility Constraint . . . . . . . . . 9
4.4. switching capability . . . . . . . . . . . . . . . . . . . 10
5. Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.1. Label Set . . . . . . . . . . . . . . . . . . . . . . . . 10
5.2. Flexible-Grid Ability and Switching Cpability
Constraint . . . . . . . . . . . . . . . . . . . . . . . . 14
5.3. Optical Signal Compatibility Constraint . . . . . . . . . 16
6. Encoding Example . . . . . . . . . . . . . . . . . . . . . . . 17
6.1. Example of Label Set Encoding . . . . . . . . . . . . . . 17
6.2. Example of Flexible-Grid Ability Constraint Encoding . . . 20
6.3. Example of Signal Compatibility Encoding . . . . . . . . . 20
7. Security Considerations . . . . . . . . . . . . . . . . . . . 21
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
9.1. Normative References . . . . . . . . . . . . . . . . . . . 21
9.2. Informative References . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22
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1. Introduction
Flexible-Grid technique breaks the rigid nature of traditional DWDM
wavelength Grid, and enables flexible allocation of optical spectrum
resources to accommodate ultra-high data rate traffic. In such
environments, Network elements (such as nodes and Optical-to-
Electronic/Electronic-to-Optical sub-systems) and links may impose
additional routing constraints such as available frequency range,
flexible-grid ability and slot width range on ports/links, asymmetric
switch connectivity, signal processing limitations of each OE/EO
system, and so on. Without considering these constraints, it cannot
be guaranteed to obtain available results in RSA process especially
for network scenarios with various Flexible-Grid and Fixed-Grid
elements, which leads to inefficient routing and high blocking
probability of end-to-end paths.
This document describes the requirments of RSA, and then encodes the
constraints imposed by network elements and links, which could be
carried in OSPF Messages to flood to each node for efficient RSA. In
addition, such information could be conveyed by other mechanisms to a
Path Computation Element (PCE). Note that, impairment-related
constraints are not considered here.
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
Center Frequency Granularity (CFG): The minimum step by which the
center frequency of optical bandwidth can be increased or decreased.
.
frequency grid: A frequency grid is a reference set of frequencies
used to denote allowed nominal central frequencies that may be used
for defining applications.
Frequency slot: The frequency range allocated to a slot and
unavailable to other slots within a flexible grid. A frequency slot
is defined by its nominal central frequency and its slot width
[G.694.1v2].
[Editor's note: according to ITU-T WP3 Q12 interim meeting [ITU-T
WD12R2], one or multiple Optical Channels may be transported over a
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single frequency slot. If this viewpoint is accepted, the following
definitions are needed:
Single-Channel Frequency Slot: a frequency slot associated with a
single optical channel signal (that carries a single OCh payload).
Multi-Channel Frequency Slot: a frequency slot associated with
multiple optical channel signals (i.e. multiple OChs).]
Frequency Slot Channel: a topological construct that represents a
piece of spectrum supported by a concatenation of media elements
(fiber, amplifiers, filters..). This term is used to identify the
end-to-end physical layer entity with its corresponding (one or more)
frequency slots local at each link.
GMPLS: Generalized Multi-Protocol Label Switching.
Lowest/Highest frequency: the lowest/highest frequency of a frequency
slot.
OCH: Optical Channel
ROADM: Reconfigurable Optical Add-Drop Multiplexer.
RSA: Routing and spectrum assignment.
Slice: the basic slot unit, and the slot width of one slice is equal
to slot width granularity.
Slot width: The full width of a frequency slot in a flexible grid
[G.694.1v2].
Slot Width Granularity (SWG): the minimum step by which the optical
filter bandwidth of ROADM can be increased or decreased.
Accordingly, SWG (GHz) = 2 * CFG (GHz).
WSON: Wavelength Switched Optical Networks [RFC6163].
WSS: Wavelength Selective Switch.
4. Requirements of Routing Constraint for RSA in Flexible-Grid Networks
In Flexible-Grid network, there is one key problem: how to route and
allocate spectrum resources for each end-to-end optical channel, so
to fulfill their requirements in an efficient way? To address this
problem, some constraints must be taken into consideration, which are
listed as follows.
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-Spectrum availability constraint.
-Flexible-Grid ability constraint.
-Asymmetric switch connectivity constraint.
-Optical signal compatibility constraint.
-Other constraints.
The asymmetric switch connectivity constraint in Flexible-Grid
network could be well addressed by Connectivity matrix sub-TLV used
in Wavelength Switched Optical Networks (WSON)
[I-D.ietf-ccamp-general-constraint-encode]. The spectrum
availability constraint is studied in several drafts
[I-D.li-ccamp-flexible-grid-label]
[I-D.zhang-ccamp-flexible-grid-ospf-ext][I-D.dhillon-ccamp-super-chan
nel-ospfte-ext], and could be represented by Label-set extensions.
However, these extensions are not complete, so we reorganize the
Flexible-Grid label-set according to WSON definition. In addition,
Flexible-Grid ability constraint (icluding grid type and slot width
granularity/range) and optical signal conpatibility constraint are
also necessary for efficient RSA, but few document takes these into
account. we will describe the requirements and encodings of such
constraints in this draft.
Here a general scenario of Flexible-Grid Network is given in order to
illustrate these requirements.
+----+A-E2 B-I1+----+B-E2 C-I1+----+
| A |----------->| B |----------->| C |
| |<-----------| |<-----------| |
+----+A-I2 B-E1+----+B-I2 C-E1+----+
O| O| O|
A-I1||A-E1 B-I3||B-E3 C-I2||C-E2
|| || ||
|| || ||
|| || ||
|| || ||
D-E1||D-I1 E-E3||E-I3 F-E2||F-I2
|O |O |O
+----+D-E2 E-I1+----+E-E2 F-I1+----+
| D |----------->| E |----------->| F |
| |<-----------| |<-----------| |
+----+D-I2 E-E1+----+E-I2 F-E1+----+
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Figure 1. A sample network with both Fixed-Grid and Flexible-Grid
elements
Tributary Side: E5 I5 E6 I6
O | O |
| | | |
| O | O
+-----------------------+
|+-----+ +-----+|
Line side-1 --->||Split| |WSS-2||---> Line side-2
Input (I1) |+-----+ +-----+| Output (E2)
Line side-1 <---||WSS-1| |Split||<--- Line side-2
Output (E1) |+-----+ +-----+| Input (I2)
| ROADM |
|+-----+ +-----+|
Line side-3 --->||Split| |WSS-4||---> Line side-4
Input (I3) |+-----+ +-----+| Output (E4)
Line side-3 <---||WSS-3| |Split||<--- Line side-4
Output (E3) |+-----+ +-----+| Input (I4)
+-----------------------+
| O | O
| | | |
O | O |
Tributary Side: E7 I7 E8 I8
Figure 2. A ROADM Composed of WSSs and splitters (Internal
connections are not presented)
Figure 1 shows the network topology, while Figure 2 shows the
architecture of nodes. The ROADM of Figure 2 is composed of WSSs and
splitters. I1~4/E1~4 are line-side input/output ports, while I5~8/
E5~8 are tributary-side add/drop ports to/from line-side 1~4
respectively. The configuration of each line-side output port is
shown as follows:
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+----+---------+-----+------+-----------+---------+---------+
|Node|Node-Type|Ports| Type |Granularity|Min width|Max width|
+----+---------+-----+------+-----------+---------+---------+
| | |A-E1 | Flex | 25GHz | 50GHz | 300GHz |
| A | Flex |-----+------+-----------+---------+---------+
| | |A-E2 | Flex | 12.5GHz | 50GHz | 200GHz |
+----+---------+-----+------+-----------+---------+---------+
| | |B-E1 | Flex | 12.5GHz | 50GHz | 200GHz |
| | |-----+------+-----------+---------+---------+
| B | Mixed |B-E2 | Fixed| 50GHz | 50GHz | 50GHz |
| | |-----+------+-----------+---------+---------+
| | |B-E3 | Flex | 12.5GHz | 50GHz | 200GHz |
+----+---------+-----+------+-----------+---------+---------+
| | |C-E1 | Fixed| 50GHz | 50GHz | 50GHz |
| C | Fixed |-----+------+-----------+---------+---------+
| | |C-E2 | Fixed| 50GHz | 50GHz | 50GHz |
+----+---------+-----+------+-----------+---------+---------+
| | |D-E1 | Flex | 25GHz | 50GHz | 300GHz |
| D | Flex |-----+------+-----------+---------+---------+
| | |D-E2 | Flex | 25GHz | 50GHz | 300GHz |
+----+---------+-----+------+-----------+---------+---------+
| | |E-E1 | Flex | 25GHz | 50GHz | 300GHz |
| | |-----+------+-----------+---------+---------+
| E | Flex |E-E2 | Flex | 12.5Ghz | 50GHz | 200GHz |
| | |-----+------+-----------+---------+---------+
| | |E-E3 | Flex | 12.5GHz | 50GHz | 200GHz |
+----+---------+-----+------+-----------+---------+---------+
| | |F-E1 | Flex | 12.5GHz | 50GHz | 200GHz |
| F | Mixed |-----+------+-----------+---------+---------+
| | |F-E2 | Fixed| 50GHz | 50GHz | 50GHz |
+----+---------+-----+------+-----------+---------+---------+
The granularity denotes the slot width granularity. The Min-width
and Max-width denote the slot width range. There are three types of
nodes: Node A, node D and node E are Flexible-Grid ROADMs, which only
consist of Flexible-Grid elements; Node C is a Fixed-Grid ROADM,
which only consists of Fixed-Grid elements; Node B and Node F are
Mixed-Grid ROADMs, which consist of both Flexible-Grid and Fixed-Grid
Elements. Both Flexible-Grid ROADM and Mixed-Grid ROADM can support
Flexible-Grid LSPs to accommodate ultra-high data rate traffic such
as beyond 100G. In addition, the Fixed-Grid ROADM can be smoothly
updated to Mixed-Grid ROADM by adding Flexible-Grid ports. With
appropriate RSA, the network is able to support both Fixed-Grid LSPs
and Flexible-Grid LSPs in an efficient way.
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4.1. Label set
In Flexible-Grid networks, the spectrum assignment is not a local
matter due to spectral consecutiveness and continuity constraints, so
it is needed to get the information of which slice may or may not be
used on each link and node port along the path in RSA process. For
example, in the network of Figure 1, when a LSP request from node A
to node E with 150GHz slot width and route A->B->E arrives, the label
restriction of input port A-I6, output port E-E7, switch port A-E2,
B-I1, B-E3, E-I3 and spectrum availability of link AB, BE must be got
for the spectrum assignment. All the information is described by the
label set objects which is decided by the label format. The
generalized label for the flexible grid can be referred to
[I-D.farrkingel-ccamp-flexigrid-lambda-label] including central
frequency and slot width information.
As specified in [I-D.li-ccamp-flexible-grid-label] in section 4.1,
this kind of label format is backward compatible to support the
traditional 5 ways of wavelength label set encoding
[I-D.ietf-ccamp-general-constraint-encode].
o 1. Inclusive list
o 2. Exclusive list
o 3. Inclusive range
o 4. Exclusive range
o 5. Bitmap set
It can be seen that these 5 types of representations can be easily
inherited by incorporating the new flexible label into the object.
Note that in the procedure of flooding, any combination of the 5
types of label sets is feasible.
4.2. Flexible-Grid Ability Constraint
Flexible-Grid ability may include the grid type (Fixed-Grid or
Flexible-Grid) and slot width granularity/range. This information
can be seen as the attribution of network ports with relations to
links or nodes. The RSA requirements of such fields are listed as
follows:
Firstly, Flexible-Grid WSSs of different companies or product-types
may have different slot width granularity and range, which may be a
subset of possible values specified by ITU-T [G.694.1v2], so it
should be taken into consideration in RSA process to avoid invalid
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route selection. For example, in the network of Figure 1, when a
Flexible-Grid LSP request from node A to node E with 250GHz slot
width arrives, only the optical channel with a route A->D->E is able
to carry the traffic due to the slot width range limitations on other
ports.
In addition, The slot width granularity of network elements may
impact the spectral efficiency. For example, when a Flexible-Grid
LSP request from node A to node E with 87.5GHz slot width arrives,
100GHz Slot width must be assigned for the route A->D->E due to 25GHz
slot width granularity, which performs poor in spectral efficiency.
FurthermoreGBP[not]Although Flexible-Grid technology may offer full
backwards compatibility with the standard ITU-T DWDM grids, it is a
cost-efficient way to consider Flexible-Grid Ability constraints in
RSA process for Fixed-Grid requirements. For example, in the network
of figure 1, when a Fixed-Grid LSP request from node B to node F with
50GHz slot width arrives, it is a better route of B->C->F than the
route B->E->F, because that flexible-Grid WSSs are more expensive
than fixed-grid ones, and routing fixed-Grid requests on fixed-Grid
elements could leave the Flexible-Grid elements and related spectrum
resources to subsequent high data rate traffic.
4.3. Optical Signal Compatibility Constraint
Optical Signal Compatibility Constraint includes the signal
processing ability (for example, data rate, FEC and modulation
format) and modulation-related minimum slot width for each Optical-
to-Electronic (OE)/Electronic-to-Optical (EO) subsystem. The RSA
requirements of such fields are listed as follows:
Firstly, as described in [I-D.ietf-ccamp-rwa-wson-encode], OE/EO
subsystems may be limited to process only certain types of optical
signal in WSON or Flexible-Grid networks, so it is necessary to get
sufficient information characterizing OE/EO elements in RSA process
to determine the signal compatibility along the path. Examples of
such subsystems include transponders, regenerators and so on.
In addition, for each Flexible-Grid Label Switch Path, the required
slot width is determined by the attribution of optical signal.
However, a client only requests "data rate" as its traffic parameter
but do not care "slot width", so it is needed to establish the
mapping relations between data-rate/modulation-format and slot width,
which should be reflected in optical signal compatibility constraint.
For example, in the network of Figure 1, when a LSP request from node
A to Node E with 100Gbit/s data rate arrives, and both the
transmitter of node A and the responder of node E support optical
tributary signal class DP-QPSK 100G with the same FEC and
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corresponding slot width 50GHz, the minimum slot width required by
this LSP should be 50GHz.
4.4. switching capability
According to ITU-T WP3 Q12 interim meeting [ITU-T WD12R2], the media
layer corresponds to the server layer (flexigrid) and the signal
layer corresponds to the client layer (OCh).this means the separation
between the signal and the waveguide that the signal propagates
through. For example, one frequency slot channel setup in media
layer could be seen as a TE-link in signal layer, and carry one
(single-channel frequency slot) or multiple (multiple-channel
frequency slot) OCh.
For control plane, it needs to differentiate signal LSP (OCh) and
media LSP (frequency-slot channel), and specify the switching
capability (signal/media) of each interface/TE-link.
5. Encoding
5.1. Label Set
The general format for a label set is in accordance with that in
[I-D.ietf-ccamp-general-constraint-encode], with a new flag G (1bit)
representing the grid type of label sets(1~Flexible-Grid DWDM;
0~Fixed-Grid DWDM):
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|G| Act.| Num Labels | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| start Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| start Label(continue) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: Additional fields as necessary per action :
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
the label format is in accordance with that in
[I-D.farrkingel-ccamp-flexigrid-lambda-label].
In the case of Inclusive/Exclusive label lists (0/1), the label set
format is given as follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| 0or1| Num Labels (not used) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| First Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| First Label(continue) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last Label(continue) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Note that one label set may contain multiple labels. The lowest/
highest frequency of the K-th label is calculated as follows:
Lowest frequency_k = (central frequency_k) - (slot width_k)/2
= (193.1 + n_k * C.S.) - (2 * C.S. * m_k)/2
= (193.1 + (n_k - m_k) * C.S.) THz;
Highest frequency_k = Lowest frequency_k + slot width_k
= (193.1 + (n_k + m_k) * C.S.) THz;
In the case of Inclusive/Exclusive label ranges (2/3), the label set
format is given as follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| 2or3| Num Labels(not used) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Start Label #1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Start Label #1(continue) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| End Label #1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| End Label #1(continue) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: :
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Start Label #n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Start Label #n(continue) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| End Label #n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| End Label #n(continue) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Note that one label set may contain multiple label ranges. The value
of m in start/end label in meaningless on the label set, however, in
order to keep the integrity of labels and avoid misunderstanding, it
is set to default value: m = (slot width granularity)/12.5GHz.
The lowest/highest frequency of the K-th label range is calculated as
follows:
Lowest frequency_k = (central frequency_kstart) - (slot width
granularity)/2
= (193.1 + n_kstart * C.S.) - C.S.
= (193.1 + (n_kstart - 1) * C.S.) THz;
Highest frequency_k = (central frequency_kend) + (slot width
granularity)/2
= (193.1 + n_kend * C.S.) + C.S.
= (193.1 + (n_kend + 1) * C.S.) THz;
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In the case of bitmap (4), the label set format is given 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| 4 | Num Labels | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Start Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Start Label(continue) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bit Map Word #1 (Lowest numerical labels) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bit Map Word #N (Highest numerical labels) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Based on [I-D.ietf-ccamp-general-constraint-encode], Num labels
denote the number of slices represented by the bit map; where the
slice denotes the basic slot unit, and the slot width of one slice is
equal to the slot width granularity. As there may exist some
situations that the unused bandwidth between two occupied bandwidth
is odd times of the central frequency granularity (not integral times
of the slot with granularity), two bits are needed to represent a
single slice. Each bit in the bit map represents a particular label
of half a slice with a value of 1/0 indicating whether the part is in
the set or not. Bit position zero and one represent the lowest slice
and corresponds to the start label. The lowest/highest frequency of
label range represented by bit position K is calculated as follows:
Lowest frequency_k = (central frequency_start) + (K - 1) * (slot
width granularity)/2
= (193.1 + n_start * C.S.) + (K - 1) * C.S.
= 193.1 + (n_start + K -1) * C.S.;
Highest frequency_k = Low frequency_k + C.S.
= 193.1 + (n_start + K) * C.S.
The size of the bit map is (2 * Num Label) bits, but the bit map is
padded out to a full multiple of 32 bits so that the TLV is a
multiple of four bytes. "Bits that do not represent labels (i.e.,
those in positions) and beyond SHOULD be set to zero and MUST be
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ignored" [I-D.ietf-ccamp-general-constraint-encode].
5.2. Flexible-Grid Ability and Switching Cpability Constraint
To accommodate the feature of Flexible-Grid Ability and switching
capability constraint, we extend the Port Label Restriction sub-TLV
defined in [I-D.ietf-ccamp-general-constraint-encode] for Flexible-
Grid networks:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MatrixID | RstType = 5 | Switching Cap.| Encoding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Grid | C.S. |S|M|Reserved | Min-Width | Max-Width |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In WSON network, Matrix ID is used to represent "either the value in
the corresponding Connectivity Matrix sub-TLV or takes the value OxFF
to indicate the restriction applies to the port regardless of any
Connectivity Matrix" [I-D.ietf-ccamp-general-constraint-encode].
RstType is used to represent the restriction type. This document
defines a new RstType value to express the port Flexible-Grid
Supporting Ability constraint in Flexible-Grid networks:
5: GRID_ABILITY.
The meaning of Grid and C.S. is defined in
[I-D.farrkingel-ccamp-flexigrid-lambda-label], which is shown as
follows:
+---------------+-------+
| Grid | Value |
+---------------+-------+
| Reserved | 0 |
+---------------+-------+
| ITU-T DWDM | 1 |
+---------------+-------+
| ITU-T CWDM | 2 |
+---------------+-------+
| Flexible DWDM | 3 |
+---------------+-------+
| Any | 4(TBA)|
+---------------+-------+
| Future use | 5-7 |
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+---------------+-------+
+-------------+---------+
|C.S. (GHz) | Value |
+-------------+---------+
| Reserved | 0 |
+-------------+---------+
| 100 | 1 |
+-------------+---------+
| 50 | 2 |
+-------------+---------+
| 25 | 3 |
+-------------+---------+
| 12.5 | 4 |
+-------------+---------+
| 6.25 | 5 (TBA) |
+-------------+---------+
|Future use | 6 ~ 15 |
+-------------+---------+
A new Grid type "Any" is defined. the reason is explained later in
this document.
"Within the fixed grid network, the C.S. value is used to represent
the channel spacing, as the spacing between adjacent channels is
constant. While for flexible grid situation, this field should be
used to represent central frequency granularity."
[I-D.farrkingel-ccamp-flexigrid-lambda-label] Accordingly the slot
width granularity is twice of the C.S..
Min-Width/Max-Width: 8bits, unsigned integer. Min-Width/Max-Width
denotes the minimum/maximum slot width that the ROADM port supports,
which is an inherent attribution of the network elements. The
formula is shown as follows:
Minimum Slot Width (GHz) = 12.5GHz * Min-Width;
Maximum Slot Width (GHz) = 12.5GHz * Max-Width;
For flexible-Grid ports (Grid = 3), the possible values of slot width
are within the range [Minimum Slot Width, Maximum Slot Width] and
with the slot width granularity of 2 * C.S.; for Fixed-Grid ports
(Grid = 1 or 2), Min-Width/Max-Width is meaningless and padded with
0. For any port with Grid type "any", it means that the port support
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any Grid type, any slot width granularity and any slot width range,
so C.S. and Min-Width/Max-Width are meaningless and padded with 0.
One example of such port is A-I1, which is comprised of optical
splitter.
Note that, the similar field of Min-Width/Max-Width is also included
in object "BW sub-TLV" proposed by
[I-D.dhillon-ccamp-super-channel-ospfte-ext]. However, BW sub-TLV is
mainly used to present the available label set, so it belongs to
dynamic information according to [RFC6163] and should be flooded
frequently whenever the link state changes (for example, after the
setup/teardown of the path traversing the link). In this document,
the Port Label Restriction sub-TLV with GRID_ABILITY type is regarded
as relatively static information, as changes to these properties such
as Grid, C.S. and Min-Width/Max-Width require hardware upgrades. It
is more suitable to carry such information separated from available
label set in order to alleviate unnecessary flooding.
A new switching capability is defined here: 151, Spectrum Switch
Capable (SSC). When the switching capability is SSC, the field S
indicates the signal-layer switch capability (1-support, 0-not),
while the field M indicates the media-layer switch capability
(1-support, 0-not).
Other port label restrictions have no difference with that in
[I-D.ietf-ccamp-general-constraint-encode].
5.3. Optical Signal Compatibility Constraint
To accommodate the feature of Optical Signal Compatibility
Constraint, we extend the Modulation Type sub-TLV defined in
[I-D.ietf-ccamp-rwa-wson-encode] for Flexible-Grid networks:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S|I| Modulation ID | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| m | Possible additional modulation parameters |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: the modulation ID :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The meaning of S, I and Modulation ID is in accordance with that of
[I-D.ietf-ccamp-rwa-wson-encode].
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This document adds a new field "m" (8bit) to represent the minimum
slot width requirement for corresponding Modulation ID:
Minimum Slot Width = 12.5GHz * m.
Note that the modulation type sub-TLV may contain multiple modulation
IDs, which means the transmitter/responder/transponder/regennerator
support multiple data rate/modulation format.
This sub-TLV establishes mapping relations between data rate/
modulation format (Modulation ID) and slot width. In addition, it
also provides the signal processing ability for each OE/EO element in
the network. However, FEC may impact the value of m, but it is not
discussed here and leaved for further study. New values of
Modulation ID should be defined for ultra-high speed transmission,
but it depends on transmission technique and not specified in this
document.
Other signal compatibility constraints have no difference with that
in [I-D.ietf-ccamp-rwa-wson-encode].
6. Encoding Example
6.1. Example of Label Set Encoding
Taking the network of figure 1 as an example, the available spectral
resource of link AB is shown in figure 3.
#1 Lowest #2 Highest #3
|-|-| |---------|---------| |-------|-------|
| |Center Freq. | ^
|1 1 0 0 1 1 1 1 1 1 1 1 1 1 0 0 0 0 1 1 1 1 1 1 1 1|
__|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|__
n= -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10
| |___|
|_|_| 12.5GHz
|
slice
Figure 3. Spectral resource state of link AB
In figure 3, the spectral resource is from 193.1THz - 16 * 6.25GHz to
193.1THz + 10 * 6.25GHz. For label list type, the label set format
is given as follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| 0 | Num Labels(not used) | Length(28) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 |C.S.(5)| Identifier | n(-15) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| m(1) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 |C.S.(5)| Identifier | n(-7) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| m(5) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 |C.S.(5)| Identifier | n(6) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| m(4) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
For label range type, the label set format is given as follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| 2 | Num Labels(not used) | Length(52) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 |C.S.(5)| Identifier | n(-15) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| m(1) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 |C.S.(5)| Identifier | n(-15) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| m(1) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 |C.S.(5)| Identifier | n(-11) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| m(1) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 |C.S.(5)| Identifier | n(-3) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| m(1) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 |C.S.(5)| Identifier | n(3) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| m(1) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 |C.S.(5)| Identifier | n(9) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| m(1) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
For bitmap type, the label set format is given 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| 4 | Num Labels(26) | Length(16) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 |C.S.(5)| Identifier | n(-15) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| m(1) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|1|0|0|1|1|1|1|1|1|1|1|1|1|0|0|0|0|1|1|1|1|1|1|1|1|0|0|0|0|0|0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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6.2. Example of Flexible-Grid Ability Constraint Encoding
Taking the network of figure 1 as an example, the Flexible-Grid
ability constraint of A-E1 can be encoded as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MatrixID(0xff)| RstType(5) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 |C.S.(5)| Reserved | Min-Width(4) | Max-Width(16) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Flexible-Grid ability constraint of A-E2 can be encoded 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MatrixID(0xff)| RstType(5) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 3 |C.S.(4)| Reserved | Min-Width(4) | Max-Width(24) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Flexible-Grid ability constraint of B-E2 can be encoded 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MatrixID(0xff)| RstType(5) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 |C.S.(2)| Reserved | Min-Width(0) | Max-Width(0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
6.3. Example of Signal Compatibility Encoding
Assuming an optical transmitter can support the following modulation
types: optical tributary signal class DP-QPSK 100G (minimum slot
width: 50GHz); optical tributary signal class DP-BPSK 100G (minimum
slot width: 100GHz). T he Modulation Type sub-TLV is given as
follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0| DP-QPSK 100G | Length(8) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| m(4) | Possible additional modulation parameters |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0| DP-BPSK 100G | Length(8) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| m(8) | Possible additional modulation parameters |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
7. Security Considerations
8. IANA Considerations
TBD.
9. References
9.1. Normative References
[G.694.1v2]
ITU-T Recommendation G.694.1, "Spectral grids for WDM
apllications: DWDM frequency grid", November 2011.
[ITU-T WD12R2]
International Telecomunications Union, WD12R2, Q12-SG15,
"Proposed media layer terminology for G.872", May 2012.
[RFC2119] Bradner, S., "Key words for use in RFC's to Indicate
Requirement Levels", RFC 2119, March 1997.
[RFC6163] Lee, Y., Bernstain, G., and W. Imajuku, "Framework for
GMPLS and Path Computation Element Control of Wavelength
Switched Optical Networks", RFC 6163, April 2011.
9.2. Informative References
[I-D.dhillon-ccamp-super-channel-ospfte-ext]
Dhillon, A., Hussain, I., Rao, RJ., and M. Sosa, "OSPFTE
extension to support GMPLS for Flex Grid", October 2011.
[I-D.farrkingel-ccamp-flexigrid-lambda-label]
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Farrel, A., King, D., Li, Y., Zhang, F., and R. Casellas,
"Generalized Labels for the Flexi-Grid in Lambda-Switch-
Capable (LSC) Label Switching Routers", October 2011.
[I-D.hussain-ccamp-super-channel-label]
Hussain, I., Dhillon, A., Pan, Z., Sosa, M., Basch, B.,
Liu, S., and A-G. Malis, "Generalized Label for Super-
Channel Assignment on Flexible Grid", October 2011.
[I-D.ietf-ccamp-general-constraint-encode]
Bernstein, G., Lee, Y., Li, D., Imajuku, W., and JR. Han,
"General Network Element Constraint Encoding for GMPLS
Controlled Networks", May 2011.
[I-D.ietf-ccamp-rwa-wson-encode]
Bernstein, G., Lee, Y., Li, D., Imajuku, W., and JR. Han,
"Routing and Wavelength Assignment Information Encoding
for Wavelength Switched Optical Networks", October 2011.
[I-D.li-ccamp-flexible-grid-label]
Li, Y., Zhang, F., and R. Casellas, "Flexible Grid Label
Format in Wavelength Switched Optical Network", July 2011.
[I-D.zhang-ccamp-flexible-grid-ospf-ext]
Zhang, FT., Zi, XB., Casellas, R., Gonzales-de-Dios, O.,
and D. Ceccarelli, "GMPLS OSPF-TE Extensions in support of
Flexible-Grid in DWDM Networks", October 2011.
[I-D.zhang-ccamp-flexible-grid-requirements]
Zhang, FT., Zi, XB., Gonzales-de-Dios, O., and R.
Casellas, "Requirements for GMPLS Control of Flexible
Grids", October 2011.
[I-D.zhang-ccamp-flexible-grid-rsvp-te-ext]
Zhang, FT., Gonzales-de-Dios, O., and D. Ceccarelli,
"RSVP-TE Signaling Extensions in support of Flexible
Grid", October 2011.
[I-D.zhangj-ccamp-flexi-grid-ospf-te-ext]
Zhang, J., Zhao, YL., and ZY. Yu, "OSPF-TE Protocol
Extension for Constraint-aware RSA in Flexi-Grid
Networks", October 2011.
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Authors' Addresses
Lei Wang
ZTE
No.19, Huayuan East Road, Haidian District
Beijing 100191
P.R.China
Phone: +86 13811440067
Email: wang.lei131@zte.com.cn (hechen0001@gmail.com)
URI: http://www.zte.com.cn/
Yao Li
ZTE
P.R.China
Phone: +86 025 52871109
Email: li.yao3@zte.com.cn
URI: http://www.zte.com.cn/
Guoying Zhang
China Academy of Telecom Research, MIIT
No.52 Huayuan Beilu, Haidian District
Beijing 100083
P.R.China
Email: zhangguoying@mail.ritt.com.cn
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