text:
of Flexi-Grid Dense Wavelength Division Multiplexing (DWDM) Networks
O. Gonzalez de Dios, Ed.
Telefonica I+D
R. Casellas, Ed.
CTTC
F. Zhang
X. Fu
Stairnote
D. Ceccarelli
I. Hussain
Framework and Requirements for GMPLS-Based Control
To allow efficient allocation of optical spectral bandwidth for systems that have high bit-rates, the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) has extended its Recommendations G.694.1 and G.872 to include a new Dense Wavelength Division Multiplexing (DWDM) grid by defining a set of nominal central frequencies, channel spacings, and the concept of the "frequency slot". In such an environment, a data-plane connection is switched based on allocated, variable-sized frequency ranges within the optical spectrum, creating what is known as a flexible grid (flexi-grid).
Given the specific characteristics of flexi-grid optical networks and their associated technology, this document defines a framework and the associated control-plane requirements for the application of the existing GMPLS architecture and control-plane protocols to the control of flexi-grid DWDM networks. The actual extensions to the GMPLS protocols will be defined in companion documents.
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). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 5741.
2.1. Requirements Language ......................................5
2.2. Abbreviations ..............................................5
3. Overview of Flexi-Grid Networks .................................6
3.1. Flexi-Grid in the Context of OTN ...........................6
3.2. Flexi-Grid Terminology .....................................6
3.2.1. Frequency Slots .....................................7
3.2.2. Media-Layer Elements ................................9
3.2.3. Media Channels .....................................10
3.2.4. Optical Tributary Signals ..........................10
3.2.5. Composite Media Channels ...........................11
3.3. Hierarchy in the Media Layer ..............................11
3.4. Flexi-Grid Layered Network Model ..........................12
3.4.1. DWDM Flexi-Grid Enabled Network Element Models .....13
4. GMPLS Applicability ............................................14
4.1. General Considerations ....................................14
4.2. Consideration of TE Links .................................14
4.3. Consideration of LSPs in Flexi-Grid .......................17
4.4. Control-Plane Modeling of Network Elements ................22
4.5. Media Layer Resource Allocation Considerations ............22
4.6. Neighbor Discovery and Link Property Correlation ..........26
4.7. Path Computation, Routing and Spectrum Assignment (RSA) ...27
4.7.1. Architectural Approaches to RSA ....................28
4.8. Routing and Topology Dissemination ........................29
4.8.1. Available Frequency Ranges (Frequency
Slots) of DWDM Links ...............................29
4.8.2. Available Slot Width Ranges of DWDM Links ..........29
4.8.3. Spectrum Management ................................29
4.8.4. Information Model ..................................30
5. Control-Plane Requirements .....................................31
5.1. Support for Media Channels ................................31
5.1.1. Signaling ..........................................32
5.1.2. Routing ............................................32
5.2. Support for Media Channel Resizing ........................33
5.3. Support for Logical Associations of Multiple Media
Channels ..................................................33
5.4. Support for Composite Media Channels ......................33
5.5. Support for Neighbor Discovery and Link Property
Correlation ...............................................34
7. Manageability Considerations ...................................35
The term "flexible grid" ("flexi-grid" for short), as defined by the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) Study Group 15 in the latest version of [G.694.1], refers to the updated set of nominal central frequencies (a frequency grid), channel spacing, and optical spectrum management and allocation considerations that have been defined in order to allow an efficient and flexible allocation and configuration of optical spectral bandwidth for systems that have high bit-rates.
A key concept of flexi-grid is the "frequency slot": a variable-sized optical frequency range that can be allocated to a data connection. As detailed later in the document, a frequency slot is characterized by its nominal central frequency and its slot width, which, as per [G.694.1], is constrained to be a multiple of a given slot width granularity.
Compared to a traditional fixed-grid network, which uses fixed-size optical spectrum frequency ranges or frequency slots with typical channel separations of 50 GHz, a flexible-grid network can select its media channels with a more flexible choice of slot widths, allocating as much optical spectrum as required.
From a networking perspective, a flexible-grid network is assumed to be a layered network [G.872] [G.800] in which the media layer is the server layer and the optical signal layer is the client layer. In the media layer, switching is based on a frequency slot, and the size of a media channel is given by the properties of the associated frequency slot. In this layered network, a media channel can transport more than one Optical Tributary Signal (OTSi), as defined later in this document.
A Wavelength Switched Optical Network (WSON), addressed in [RFC6163], is a term commonly used to refer to the application/deployment of a GMPLS-based control plane for the control (e.g., provisioning and recovery) of a fixed-grid Wavelength Division Multiplexing (WDM) network in which media (spectrum) and signal are jointly considered.
This document defines the framework for a GMPLS-based control of flexi-grid enabled Dense Wavelength Division Multiplexing (DWDM) networks (in the scope defined by ITU-T layered Optical Transport Networks [G.872]), as well as a set of associated control-plane requirements. An important design consideration relates to the decoupling of the management of the optical spectrum resource and the client signals to be transported.
Further terminology specific to flexi-grid networks can be found in Section 3.2.
2.1. Requirements Language
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].
While [RFC2119] describes interpretations of these key words in terms of protocol specifications and implementations, they are used in this document to describe design requirements for protocol extensions.
2.2. Abbreviations
FS:
Frequency Slot
FSC:
Fiber-Switch Capable
LSR:
Label Switching Router
NCF:
Nominal Central Frequency
OCC:
Optical Channel Carrier
OCh:
Optical Channel
OCh-P:
Optical Channel Payload
OTN:
Optical Tributary Signal
OTSiG:
OTSi Group is a set of OTSi
PCE:
Path Computation Element
ROADM: Reconfigurable Optical Add/Drop Multiplexer
SSON:
Spectrum-Switched Optical Network
SWG:
Slot Width Granularity
3. Overview of Flexi-Grid Networks
3.1. Flexi-Grid in the Context of OTN
[G.872] describes, from a network level, the functional architecture of an OTN. It is decomposed into independent-layer networks with client/layer relationships among them. A simplified view of the OTN layers is shown in Figure 1.
| Digital Layer  |
| Signal Layer   |
|  Media Layer   |
Figure 1: Generic OTN Overview
In the OTN layering context, the media layer is the server layer of the optical signal layer. The optical signal is guided to its destination by the media layer by means of a network media channel. In the media layer, switching is based on a frequency slot.
In this scope, this document uses the term "flexi-grid enabled DWDM network" to refer to a network in which switching is based on frequency slots defined using the flexible grid. This document mainly covers the media layer, as well as the required adaptations from the signal layer. The present document is thus focused on the control and management of the media layer.
3.2. Flexi-Grid Terminology
This section presents the definitions of the terms used in flexi-grid
networks.  More details about these terms can be found in ITU-T
Recommendations [G.694.1], [G.872], [G.870], [G.8080], and
[G.959.1-2013].
Where appropriate, this document also uses terminology and lexicography from [RFC4397].
3.2.1. Frequency Slots
This subsection is focused on the frequency slot and related terms.
Frequency Slot [G.694.1]: The frequency range allocated to a slot within the flexible grid and unavailable to other slots. A frequency slot is defined by its nominal central frequency and its slot width.
Nominal Central Frequency: Each of the allowed frequencies as per the definition of the flexible DWDM grid in [G.694.1]. The set of nominal central frequencies can be built using the following expression:
f = 193.1 THz + n x 0.00625 THz
where 193.1 THz is the ITU-T "anchor frequency" for transmission over the C-band and 'n' is a positive or negative integer including 0.
-5 -4 -3 -2 -1  0  1  2  3  4  5     <- values of n
...+--+--+--+--+--+--+--+--+--+--+-
193.1 THz <- anchor frequency
Figure 2: Anchor Frequency and Set of Nominal Central Frequencies
Nominal Central Frequency Granularity: The spacing between allowed nominal central frequencies. It is set to 6.25 GHz [G.694.1].
Slot Width Granularity (SWG): 12.5 GHz, as defined in [G.694.1].
Slot Width: Determines the "amount" of optical spectrum, regardless of its actual "position" in the frequency axis. A slot width is constrained to be m x SWG (that is, m x 12.5 GHz), where 'm' is an integer greater than or equal to 1.
Frequency Slot 1     Frequency Slot 2
-------------     -------------------
|           |     |                 |
-3 -2 -1  0  1  2  3  4  5  6  7  8  9 10 11
...--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--...
^                    ^
Slot NCF = 193.1 THz    Slot NCF = 193.14375 THz
Slot width = 25 GHz     Slot width = 37.5 GHz
n = 0, m = 2            n = 7, m = 3
Figure 3: Example Frequency Slots
The symbol '+' represents the allowed nominal central frequencies.
The '--' represents the nominal central frequency granularity in units of 6.25 GHz.
The '^' represents the slot nominal central frequency.
The number on the top of the '+' symbol represents the 'n' in the frequency calculation formula.
The nominal central frequency is 193.1 THz when n equals zero.
Effective Frequency Slot [G.870]: That part of the frequency slots of the filters along the media channel that is common to all of the filters' frequency slots. Note that both the terms "frequency slot" and "effective frequency slot" are applied locally.
Figure 4 shows the effect of combining two filters along a channel. The combination of Frequency Slot 1 and Frequency Slot 2 applied to the media channel is the effective frequency slot shown.
Frequency Slot 1
|           |
..--+--+--+--+--X--+--+--+--+--+--+--+--+--+--+--+--...
Effective Frequency Slot
Figure 4: Effective Frequency Slot
3.2.2. Media-Layer Elements
Media Element: A media element directs an optical signal or affects the properties of an optical signal. It does not modify the properties of the information that has been modulated to produce the optical signal [G.870]. Examples of media elements include fibers, amplifiers, filters, and switching matrices.
Media Channel Matrix: The media channel matrix provides flexible connectivity for the media channels. That is, it represents a point of flexibility where relationships between the media ports at the edge of a media channel matrix may be created and broken. The relationship between these ports is called a "matrix channel". (Network) media channels are switched in a media channel matrix.
3.2.3. Media Channels
This section defines concepts such as the (network) media channel; the mapping to GMPLS constructs (i.e., LSP) is detailed in Section 4.
Media Channel: A media association that represents both the topology (i.e., path through the media) and the resource (frequency slot) that it occupies. As a topological construct, it represents a frequency slot (an effective frequency slot) supported by a concatenation of media elements (fibers, amplifiers, filters, switching matrices...). 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 filter.
Network Media Channel: Defined in [G.870] as a media channel that transports a single OTSi (defined in the next subsection).
3.2.4. Optical Tributary Signals
Optical Tributary Signal (OTSi): The optical signal that is placed within a network media channel for transport across the optical network. This may consist of a single modulated optical carrier or a group of modulated optical carriers or subcarriers. To provide a connection between the OTSi source and the OTSi sink, the optical signal must be assigned to a network media channel (see also [G.959.1-2013]).
OTSi Group (OTSiG): The set of OTSi that are carried by a group of network media channels. Each OTSi is carried by one network media channel. From a management perspective, it SHOULD be possible to manage both the OTSiG and a group of network media channels as single entities.
3.2.5. Composite Media Channels
It is possible to construct an end-to-end media channel as a composite of more than one network media channel. A composite media channel carries a group of OTSi (i.e., OTSiG). Each OTSi is carried by one network media channel. This OTSiG is carried over a single fiber.
In this case, the effective frequency slots may be contiguous (i.e., there is no spectrum between them that can be used for other media channels) or non-contiguous.
It is not currently envisaged that such composite media channels may be constructed from slots carried on different fibers whether those fibers traverse the same hop-by-hop path through the network or not.
Furthermore, it is not considered likely that a media channel may be constructed from a different variation of slot composition on each hop. That is, the slot composition (i.e., the group of OTSi carried by the composite media channel) must be the same from one end of the media channel to the other, even if the specific slot for each OTSi and the spacing among slots may vary hop by hop.
How the signal is carried across such groups of network media channels is out of scope for this document.
3.3. Hierarchy in the Media Layer
In summary, the concept of the frequency slot is a logical abstraction that represents a frequency range, while the media layer represents the underlying media support. Media channels are media associations, characterized by their respective (effective) frequency slots, and media channels are switched in media channel matrices. From the control and management perspective, a media channel can be logically split into network media channels.
In Figure 5, a media channel has been configured and dimensioned to support two network media channels, each of them carrying one OTSi.
Media Channel Frequency Slot
+-------------------------------X------------------------------+
|                                                              |
|       Frequency Slot                  Frequency Slot         |
|   +-----------X-----------+       +----------X-----------+   |
|   |         OTSi          |       |         OTSi         |   |
|   |           o           |       |          o           |   |
|   |           |           |       |          |           |   |
-4  -3  -2  -1   0   1   2   3   4   5   6   7  8   9  10  11  12
--+---+---+---+---+---+---+---+---+---+---+---+--+---+---+---+---+--
<- Network Media Channel ->    <- Network Media Channel ->
<------------------------ Media Channel ----------------------->
X - Frequency Slot Central Frequency
- Signal Central Frequency
Figure 5: Example of Media Channel, Network Media Channels, and
Associated Frequency Slots
3.4. Flexi-Grid Layered Network Model
In the OTN layered network, the network media channel transports a single OTSi (see Figure 6).
|                            OTSi                                 |
O - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - O
|                                                                 |
| Channel Port         Network Media Channel         Channel Port |
+--------+                 +-----------+                   +--------+
|  \ (1) |                 |    (1)    |                   | (1)  / |
|   \----|-----------------|-----------|-------------------|-----/  |
+--------+ Link Channel    +-----------+  Link Channel     +--------+
Media Channel            Media Channel                Media Channel
Matrix                   Matrix                       Matrix
The symbol (1) indicates a matrix channel
Figure 6: Simplified Layered Network Model
Note that a particular example of OTSi is the OCh-P. Figure 7 shows this specific example as defined in G.805 [G.805].
OCh AP                     Trail (OCh)                    OCh AP
O- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - O
--- OCh-P                                                OCh-P ---
\ / source                                               sink  \ /
+                                                              +
| OCh-P               OCh-P Network Connection           OCh-P |
O TCP - - - - - - - - - - - - - - - - - - - - - - - - - - -TCP O
|Channel Port          Network Media Channel      Channel Port |
O - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  O
+--------+                 +-----------+                 +---------+
|  \ (1) |  OCh-P LC       |    (1)    |  OCh-P LC       |  (1)  / |
|   \----|-----------------|-----------|-----------------|------/  |
+--------+ Link Channel    +-----------+  Link Channel   +---------+
Media Channel              Media Channel                Media Channel
Matrix                     Matrix                        Matrix
"LC" indicates a link connection
Figure 7: Layered Network Model According to G.805
3.4.1. DWDM Flexi-Grid Enabled Network Element Models
A flexible-grid network is constructed from subsystems that include WDM links, tunable transmitters, and receivers (i.e., media elements including media-layer switching elements that are media matrices), as well as electro-optical network elements. This is just the same as in a fixed-grid network, except that each element has flexible-grid characteristics.
As stated in Clause 7 of [G.694.1], the flexible DWDM grid 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 might not 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 is 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 where slot widths are a multiple of 25 GHz (by only requiring values of m that are even).
4. GMPLS Applicability
The goal of this section is to provide an insight into the application of GMPLS as a control mechanism in flexi-grid networks. Specific control-plane requirements for the support of flexi-grid networks are covered in Section 5. This framework is aimed at controlling the media layer within the OTN hierarchy and controlling the required adaptations of the signal layer. This document also defines the term "Spectrum-Switched Optical Network" (SSON) to refer to a flexi-grid enabled DWDM network that is controlled by a GMPLS or PCE control plane.
This section provides a mapping of the ITU-T G.872 architectural aspects to GMPLS and control-plane terms and also considers the relationship between the architectural concept or construct of a media channel and its control-plane representations (e.g., as a TE link, as defined in [RFC3945]).
4.1. General Considerations
The GMPLS control of the media layer deals with the establishment of media channels that are switched in media channel matrices. GMPLS labels are used to locally represent the media channel and its associated frequency slot. Network media channels are considered a particular case of media channels when the endpoints are transceivers (that is, the source and destination of an OTSi).
4.2. Consideration of TE Links
From a theoretical point of view, a fiber can be modeled as having a frequency slot that ranges from minus infinity to plus infinity. This representation helps us understand the relationship between frequency slots and ranges.
The frequency slot is a local concept that applies within a component or element. When applied to a media channel, we are referring to its effective frequency slot as defined in [G.872].
The association sequence of the three components (i.e., a filter, a fiber, and a filter) is a media channel in its most basic form. From the control-plane perspective, this may be modeled as a (physical) TE link with a contiguous optical spectrum. This can be represented by saying that the portion of spectrum available at time t0 depends on which filters are placed at the ends of the fiber and how they have been configured. Once filters are placed, we have a one-hop media channel. In practical terms, associating a fiber with the terminating filters determines the usable optical spectrum.
---------------+                             +-----------------
|                             |
+--------+                             +--------+
|        |                             |        |  +---------
---o|        ===============================        o--|
|        |             Fiber           |        |  | --\  /--
---o|        |                             |        o--|    \/
|        |                             |        |  |    /\
---o|        ===============================        o--| --/  \--
| Filter |                             | Filter |  |
|------- Basic Media Channel  ---------|
--------+                                      +--------
|--------------------------------------|
LSR    |               TE link                |  LSR
Figure 8: (Basic) Media Channel and TE Link
Additionally, when a cross-connect for a specific frequency slot is considered, the resulting media support of joining basic media channels is still a media channel, i.e., a longer association sequence of media elements and its effective frequency slot. In other words, it is possible to "concatenate" several media channels (e.g., patch on intermediate nodes) to create a single media channel.
The architectural construct resulting from the association sequence of basic media channels and media-layer matrix cross-connects can be represented as (i.e., corresponds to) a Label Switched Path (LSP) from a control-plane perspective.
----------+       +------------------------------+       +---------
|       |                              |       |
+------+       +------+                +------+       +------+
|      |       |      |  +----------+  |      |       |      |
--o|      =========      o--|          |--o      =========      o--
|      | Fiber |      |  | --\  /-- |  |      | Fiber |      |
--o|      |       |      o--|    \/    |--o      |       |      o--
|      |       |      |  |    /\    |  |      |       |      |
--o|      =========      o--***********|--o      =========      o--
|Filter|       |Filter|  |          |  |Filter|       |Filter|
|      |       |      |                |      |       |      |
<- Basic Media ->    <- Matrix ->       <- Basic Media ->
|Channel|           Channel            |Channel|
<-------------------- Media Channel ---------------->
------+                  +---------------+                  +------
|------------------|               |------------------|
LSR  |       TE link    |      LSR      |   TE link        |  LSR
Figure 9: Extended Media Channel
Furthermore, if appropriate, the media channel can also be represented as a TE link or Forwarding Adjacency (FA) [RFC4206], augmenting the control-plane network model.
<------------------------ Media Channel ----------->
------+                                                      +-----
|------------------------------------------------------|
LSR  |                               TE link                | LSR
Figure 10: Extended Media Channel TE Link or FA
4.3. Consideration of LSPs in Flexi-Grid
The flexi-grid LSP is a control-plane representation of a media channel. Since network media channels are media channels, an LSP may also be the control-plane representation of a network media channel (without considering the adaptation functions). From a control-plane perspective, the main difference (regardless of the actual effective frequency slot, which may be dimensioned arbitrarily) is that the LSP that represents a network media channel also includes the endpoints (transceivers), including the cross-connects at the ingress and egress nodes. The ports towards the client can still be represented as interfaces from the control-plane perspective.
Figure 11 shows an LSP routed between three nodes. The LSP is terminated before the optical matrix of the ingress and egress nodes and can represent a media channel. This case does not (and cannot) represent a network media channel because it does not include (and cannot include) the transceivers.
---------+       +--------------------------------+       +--------
|       |                                |       |
+------+       +------+                  +------+       +------+
|      |       |      |   +----------+   |      |       |      |
-o|      =========      o---|          |---o      =========      o-
|      | Fiber |      |   | --\  /-- |   |      | Fiber |      |
-o|>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>o-
|      |       |      |   |    /\    |   |      |       |      |
-o|      =========      o---***********|---o      =========      o-
|Filter|       |Filter|   |          |   |Filter|       |Filter|
|      |       |      |                  |      |       |      |
>>>>>>>>>>>>>>>>>>>>>>>>>>>> LSP >>>>>>>>>>>>>>>>>>>>>>>>
-----+                  +---------------+                +-----
|------------------|               |----------------|
LSR  |       TE link    |     LSR       |      TE link   | LSR
Figure 11: Flexi-Grid LSP Representing a Media Channel That Starts at
the Filter of the Outgoing Interface of the Ingress LSR and Ends at
the Filter of the Incoming Interface of the Egress LSR
In Figure 12, a network media channel is represented as terminated at the network side of the transceivers. This is commonly named an OTSi-trail connection.
|--------------------- Network Media Channel ----------------------|
+----------------------+           +----------------------+
|                                  |                      |
+------+        +------+           +------+        +------+
|      | +----+ |      |           |      | +----+ |      |OTSi
OTSi|      o-|    |-o      |  +-----+  |      o-|    |-o      |sink
src |      | |    | |      ===+-+ +-+==|      | |    | |      O---|R
T|***o******o********************************************************
|      | |\  /| |         | | | |  |      | |\  /| |      |
|      o-| \/ |-o      ===| | | |==|      o-| \/ |-o      |
|      | | /\ | |      |  +-+ +-+  |      | | /\ | |      |
|      o-|/  \|-o      |  |  \/ |  |      o-|/  \|-o      |
|Filter| |    | |Filter|  |  /\ |  |Filter| |    | |Filter|
+------+ |    | +------+  +-----+  +------+ |    | +------+
|        |    |        |           |        |    |        |
<------------------------------------------------------------------->
<------------------------------------------------------------------>
+-----+                   +--------+                +-----+
o--- |     |-------------------|        |----------------|     |---o
| LSR |       TE link     |  LSR   |   TE link      | LSR |
|     |-------------------|        |----------------|     |
Figure 12: LSP Representing a Network Media Channel (OTSi Trail)
In a third case, a network media channel is terminated on the filter ports of the ingress and egress nodes. This is defined in G.872 as an OTSi Network Connection. As can be seen from the figures, from a GMPLS modeling perspective there is no difference between these cases, but they are shown as distinct examples to highlight the differences in the data plane.
|---------------------  Network Media Channel --------------------|
+------------------------+               +------------------------+
+------+        +------+                 +------+          +------+
|      | +----+ |      |                 |      | +----+ |      |
|      o-|    |-o      |    +------+     |      o-|    |-o      |
|      | |    | |      =====+-+  +-+=====|      | |    | |      |
T-o******o********************************************************O-R
|      | |\  /| |           | |  | |     |      | |\  /| |      |
|      o-| \/ |-o      =====| |  | |=====|      o-| \/ |-o      |
|      | | /\ | |      |    +-+  +-+     |      | | /\ | |      |
|      o-|/  \|-o      |    |  \/  |     |      o-|/  \|-o      |
|Filter| |    | |Filter|    |  /\  |     |Filter| |    | |Filter|
+------+ |    | +------+    +------+     +------+ |    | +------+
|        |    |        |                 |        |    |        |
+----------------------+                 +----------------------+
<----------------------------------------------------------------->
<-------------------------------------------------------------->
+-----+                    +--------+                   +-----+
o--|     |--------------------|        |-------------------|     |--o
| LSR |       TE link      |  LSR   |      TE link      | LSR |
|     |--------------------|        |-------------------|     |
Figure 13: LSP Representing a Network Media Channel
(OTSi Network Connection)
Applying the notion of hierarchy at the media layer, by using the LSP as an FA (i.e., by using hierarchical LSPs), the media channel created can support multiple (sub-)media channels.
+--------------+                      +--------------+
| Media Channel|           TE         | Media Channel|  Virtual TE
|              |          link        |              |    link
|    Matrix    |o- - - - - - - - - - o|    Matrix    |o- - - - - -
|     +---------+      |
|     |  Media  |      |
|o----| Channel |-----o|
| Matrix  |
+---------+
Figure 14: Topology View with TE Link or FA
Note that there is only one media-layer switch matrix (one implementation is a flexi-grid ROADM) in SSON, while a signal-layer LSP (network media channel) is established mainly for the purpose of management and control of individual optical signals. Signal-layer LSPs with the same attributes (such as source and destination) can be grouped into one media-layer LSP (media channel); this has advantages in spectral efficiency (reduced guard band between adjacent OChs in one FSC channel) and LSP management. However, assuming that some network elements perform signal-layer switching in an SSON, there must be enough guard band between adjacent OTSi in any media channel to compensate for the filter concatenation effects and other effects caused by signal-layer switching elements. In such a situation, the separation of the signal layer from the media layer does not bring any benefit in spectral efficiency or in other aspects, and it makes the network switching and control more complex. If two OTSi must be switched to different ports, it is better to carry them via different FSC channels, and the media-layer switch is enough in this scenario.
As discussed in Section 3.2.5, a media channel may be constructed from a composite of network media channels. This may be achieved in two ways using LSPs. These mechanisms may be compared to the techniques used in GMPLS to support inverse multiplexing in Time Division Multiplexing (TDM) networks and in OTN [RFC4606] [RFC6344] [RFC7139].
In the first case, a single LSP may be established in the control plane. The signaling messages include information for all of the component network media channels that make up the composite media channel.
In the second case, each component network media channel is established using a separate control-plane LSP, and these LSPs are associated within the control plane so that the endpoints may see them as a single media channel.
4.4. Control-Plane Modeling of Network Elements
Optical transmitters and receivers may have different tunability constraints, and media channel matrices may have switching restrictions. Additionally, a key feature of their implementation is their highly asymmetric switching capability, which is described in detail in [RFC6163]. Media matrices include line-side ports that are connected to DWDM links and tributary-side input/output ports that can be connected to transmitters/receivers.
A set of common constraints can be defined:
Slot widths: The minimum and maximum slot width.
Granularity: The optical hardware may not be able to select parameters with the lowest granularity (e.g., 6.25 GHz for nominal central frequencies or 12.5 GHz for slot width granularity).
Available frequency ranges: The set or union of frequency ranges that have not been allocated (i.e., are available). The relative grouping and distribution of available frequency ranges in a fiber are usually referred to as "fragmentation".
Available slot width ranges: The set or union of slot width ranges supported by media matrices. It includes the following information:
Slot width threshold: The minimum and maximum slot width supported by the media matrix. For example, the slot width could be from 50 GHz to 200 GHz.
Step granularity: The minimum step by which the optical filter bandwidth of the media matrix can be increased or decreased. This parameter is typically equal to slot width granularity (i.e., 12.5 GHz) or integer multiples of 12.5 GHz.
4.5. Media Layer Resource Allocation Considerations
A media channel has an associated effective frequency slot. From the perspective of network control and management, this effective slot is seen as the "usable" end-to-end frequency slot. The establishment of an LSP is related to the establishment of the media channel and the configuration of the effective frequency slot.
A "service request" is characterized (at a minimum) by its required effective slot width. This does not preclude the request from adding additional constraints, such as also imposing the nominal central frequency. A given effective frequency slot may be requested for the media channel in the control-plane LSP setup messages, and a specific frequency slot can be requested on any specific hop of the LSP setup. Regardless of the actual encoding, the LSP setup message specifies a minimum effective frequency slot width that needs to be fulfilled in order to successfully establish the requested LSP.
An effective frequency slot must equally be described in terms of a central nominal frequency and its slot width (in terms of usable spectrum of the effective frequency slot). That is, it must be possible to determine the end-to-end values of the n and m parameters. We refer to this by saying that the "effective frequency slot of the media channel or LSP must be valid".
In GMPLS, the requested effective frequency slot is represented to the TSpec present in the RSVP-TE Path message, and the effective frequency slot is mapped to the FlowSpec carried in the RSVP-TE Resv message.
In GMPLS-controlled systems, the switched element corresponds to the 'label'. In flexi-grid, the switched element is a frequency slot, and the label represents a frequency slot. Consequently, the label in flexi-grid conveys the necessary information to obtain the frequency slot characteristics (i.e., central frequency and slot width: the n and m parameters). The frequency slot is locally identified by the label.
The local frequency slot may change at each hop, given hardware constraints and capabilities (e.g., a given node might not support the finest granularity). This means that the values of n and m may change at each hop. As long as a given downstream node allocates enough optical spectrum, m can be different along the path. This covers the issue where media matrices can have different slot width granularities. Such variations in the local value of m will appear in the allocated label that encodes the frequency slot as well as in the FlowSpec that describes the flow.
Different operational modes can be considered. For Routing and Spectrum Assignment (RSA) with explicit label control, and for Routing and Distributed Spectrum Assignment (R+DSA), the GMPLS signaling procedures are similar to those described in Section 4.1.3 of [RFC6163] for Routing and Wavelength Assignment (RWA) and for Routing and Distributed Wavelength Assignment (R+DWA). The main difference is that the label set specifies the available nominal central frequencies that meet the slot width requirements of the LSP.
The intermediate nodes use the control plane to collect the acceptable central frequencies that meet the slot width requirement hop by hop. The tail-end node also needs to know the slot width of an LSP to assign the proper frequency resource. Except for identifying the resource (i.e., fixed wavelength for WSON, and frequency resource for flexible grids), the other signaling requirements (e.g., unidirectional or bidirectional, with or without converters) are the same as for WSON as described in Section 6.1 of [RFC6163].
Regarding how a GMPLS control plane can assign n and m hop by hop along the path of an LSP, different cases can apply:
a. n and m can both change. It is the effective frequency slot that
matters; it needs to remain valid along the path.
b. m can change, but n needs to remain the same along the path.
This ensures that the nominal central frequency stays the same, but the width of the slot can vary along the path. Again, the important thing is that the effective frequency slot remains valid and satisfies the requested parameters along the whole path of the LSP.
c. n and m need to be unchanging along the path. This ensures that
the frequency slot is well known from end to end and is a simple way to ensure that the effective frequency slot remains valid for the whole LSP.
d. n can change, but m needs to remain the same along the path.
This ensures that the effective frequency slot remains valid but also allows the frequency slot to be moved within the spectrum from hop to hop.
The selection of a path that ensures n and m continuity can be delegated to a dedicated entity such as a Path Computation Element (PCE). Any constraint (including frequency slot and width granularities) can be taken into account during path computation. Alternatively, A PCE can compute a path, leaving the actual frequency slot assignment to be done, for example, with a distributed (signaling) procedure:
Each downstream node ensures that m is >= requested_m.
A downstream node cannot foresee what an upstream node will allocate. A way to ensure that the effective frequency slot is valid along the length of the LSP is to ensure that the same value of n is allocated at each hop. By forcing the same value of n, we avoid cases where the effective frequency slot of the media channel is invalid (that is, the resulting frequency slot cannot be described by its n and m parameters).
This may be too restrictive, since a node (or even a centralized/ combined RSA entity) may be able to ensure that the resulting end-to-end effective frequency slot is valid, even if n varies locally. That means that the effective frequency slot that characterizes the media channel from end to end is consistent and is determined by its n and m values but that the effective frequency slot and those values are logical (i.e., do not map "direct" to the physically assigned spectrum) in the sense that they are the result of the intersection of locally assigned frequency slots applicable at local components (such as filters), each of which may have different frequency slots assigned to them.
As shown in Figure 15, the effective slot is made valid by ensuring that the minimum m is greater than the requested m. The effective slot (intersection) is the lowest m (bottleneck).
C                B                A
|Path(m_req)   |                ^                |
|--------->    |                #                |
|              |                #                ^
-^--------------^----------------#----------------#--
Effective #              #                #                #
FS n, m   # . . . . . . .#. . . . . . . . # . . . . . . . .# <-fixed
#              #                #                #   n
-v--------------v----------------#----------------#---
|              |                #                v
|              |                #          Resv  |
|              |                v        <------ |
|              |                |FlowSpec(n, m_a)|
|              |       <--------|                |
|              |  FlowSpec(n,   |
<--------|      min(m_a, m_b))
FlowSpec(n,    |
min(m_a, m_b, m_c))
m_a, m_b, m_c: Selected frequency slot widths
Figure 15: Distributed Allocation with Different m and Same n
In Figure 16, the effective slot is made valid by ensuring that it is valid at each hop in the upstream direction. The intersection needs to be computed; otherwise, invalid slots could result.
C                B                 A
|Path(m_req)  ^                |                 |
|--------->   #                |                 |
|             #                ^                 ^
-^-------------#----------------#-----------------#--------
Effective #             #                #                 #
FS n, m   #             #                #                 #
#             #                #                 #
-v-------------v----------------#-----------------#--------
|             |                #                 v
|             |                #           Resv  |
|             |                v         <------ |
|             |                |FlowSpec(n_a, m_a)
|             |       <--------|                 |
|             |  FlowSpec(FSb [intersect] FSa)
<--------|
FlowSpec([intersect] FSa,FSb,FSc)
n_a: Selected nominal central frequency by node A
m_a: Selected frequency slot widths by node A
FSa, FSb, FSc: Frequency slot at each hop A, B, C
Figure 16: Distributed Allocation with Different m and Different n
Note that when a media channel is bound to one OTSi (i.e., is a network media channel), the effective FS must be the frequency slot of the OTSi. The media channel set up by the LSP may contain the effective FS of the network media channel effective FS. This is an endpoint property; the egress and ingress have to constrain the effective FS to be the OTSi effective FS.
4.6. Neighbor Discovery and Link Property Correlation
There are potential interworking problems between fixed-grid DWDM nodes and flexi-grid DWDM nodes. Additionally, even two flexi-grid nodes may have different grid properties, leading to link property conflict and resulting in limited interworking.
Devices or applications that make use of flexi-grid might not be able to support every possible slot width. In other words, different applications may be defined where each supports a different grid granularity. In this case, the link between two optical nodes with different grid granularities must be configured to align with the larger of both granularities. Furthermore, different nodes may have different slot width tuning ranges.
In summary, in a DWDM link between two nodes, at a minimum, the following properties need to be negotiated:
Grid capability (channel spacing) - Between fixed-grid and flexi-grid nodes.
Grid granularity - Between two flexi-grid nodes.
Slot width tuning range - Between two flexi-grid nodes.
4.7. Path Computation, Routing and Spectrum Assignment (RSA)
In WSON, if there is no (available) wavelength converter in an optical network, an LSP is subject to the "wavelength continuity constraint" (see Section 4 of [RFC6163]). Similarly, in flexi-grid, if the capability to shift or convert an allocated frequency slot is absent, the LSP is subject to the "spectrum continuity constraint".
Because of the limited availability of spectrum converters (in what is called a "sparse translucent optical network"), the spectrum continuity constraint always has to be considered. When available, information regarding spectrum conversion capabilities at the optical nodes may be used by RSA mechanisms.
The RSA process determines a route and frequency slot for an LSP. Hence, when a route is computed, the spectrum assignment process determines the central frequency and slot width based on the following:
the requested slot width
the information regarding the transmitter and receiver capabilities, including the availability of central frequencies and their slot width granularity
the information regarding available frequency slots (frequency ranges) and available slot widths of the links traversed along the route
4.7.1. Architectural Approaches to RSA
Similar to RWA for fixed grids [RFC6163], different ways of performing RSA in conjunction with the control plane can be considered. The approaches included in this document are provided for reference purposes only; other possible options could also be deployed.
Note that all of these models allow the concept of a composite media channel supported by a single control-plane LSP or by a set of associated LSPs.
4.7.1.1. Combined RSA (R&SA)
In this case, a computation entity performs both routing and frequency slot assignment. The computation entity needs access to detailed network information, e.g., the connectivity topology of the nodes and links, available frequency ranges on each link, and node capabilities.
The computation entity could reside on a dedicated PCE server, in the provisioning application that requests the service, or on the ingress node.
4.7.1.2. Separated RSA (R+SA)
In this case, routing computation and frequency slot assignment are performed by different entities. The first entity computes the routes and provides them to the second entity. The second entity assigns the frequency slot.
The first entity needs the connectivity topology to compute the proper routes. The second entity needs information about the available frequency ranges of the links and the capabilities of the nodes in order to assign the spectrum.
4.7.1.3. Routing and Distributed SA (R+DSA)
In this case, an entity computes the route, but the frequency slot assignment is performed hop by hop in a distributed way along the route. The available central frequencies that meet the spectrum continuity constraint need to be collected hop by hop along the route. This procedure can be implemented by the GMPLS signaling protocol.
4.8. Routing and Topology Dissemination
In the case of the combined RSA architecture, the computation entity needs the detailed network information, i.e., connectivity topology, node capabilities, and available frequency ranges of the links. Route computation is performed based on the connectivity topology and node capabilities, while spectrum assignment is performed based on the available frequency ranges of the links. The computation entity may get the detailed network information via the GMPLS routing protocol.
For WSON, the connectivity topology and node capabilities can be advertised by the GMPLS routing protocol (refer to Section 6.2 of [RFC6163]). Except for wavelength-specific availability information, the information for flexi-grid is the same as for WSON and can equally be distributed by the GMPLS routing protocol.
This section analyzes the necessary changes to link information required by flexible grids.
4.8.1. Available Frequency Ranges (Frequency Slots) of DWDM Links
In the case of flexible grids, channel central frequencies span from 193.1 THz towards both ends of the C-band spectrum with a granularity of 6.25 GHz. Different LSPs could make use of different slot widths on the same link. Hence, the available frequency ranges need to be advertised.
4.8.2. Available Slot Width Ranges of DWDM Links
The available slot width ranges need to be advertised in combination with the available frequency ranges, so that the computing entity can verify whether an LSP with a given slot width can be set up or not. This is constrained by the available slot width ranges of the media matrix. Depending on the availability of the slot width ranges, it is possible to allocate more spectrum than what is strictly needed by the LSP.
4.8.3. Spectrum Management
The total available spectrum on a fiber can be described as a resource that can be partitioned. For example, a part of the spectrum could be assigned to a third party to manage, or parts of the spectrum could be assigned by the operator for different classes of traffic. This partitioning creates the impression that the spectrum is a hierarchy in view of the management plane and the control plane: each partition could itself be partitioned. However, the hierarchy is created purely within a management system; it defines a hierarchy of access or management rights, but there is no corresponding resource hierarchy within the fiber.
The end of the fiber is a link end and presents a fiber port that represents all of the spectrum available on the fiber. Each spectrum allocation appears as a Link Channel Port (i.e., frequency slot port) within the fiber. Thus, while there is a hierarchy of ownership (the Link Channel Port and corresponding LSP are located on a fiber and therefore are associated with a fiber port), there is no continued nesting hierarchy of frequency slots within larger frequency slots. In its way, this mirrors the fixed-grid behavior where a wavelength is associated with a fiber port but cannot be subdivided even though it is a partition of the total spectrum available on the fiber.
4.8.4. Information Model
This section defines an information model to describe the data that represents the capabilities and resources available in a flexi-grid network. It is not a data model and is not intended to limit any protocol solution such as an encoding for an IGP. For example, information required for routing and path selection may be the set of available nominal central frequencies from which a frequency slot of the required width can be allocated. A convenient encoding for this information is left for further study in an IGP encoding document.
Fixed DWDM grids can also be described via suitable choices of slots in a flexible DWDM grid. However, devices or applications that make use of the flexible grid may not be capable of supporting every possible slot width or central frequency position. Thus, the information model needs to enable:
the exchange of information to enable RSA in a flexi-grid network
the representation of a fixed-grid device participating in a flexi-grid network
full interworking of fixed-grid and flexible-grid devices within the same network
interworking of flexible-grid devices with different capabilities
The information model is represented using the Routing Backus-Naur Format (RBNF) as defined in [RFC5511].
<Available Spectrum> ::=
<Available Frequency Range-List>
<Available NCFs>
<Available Slot Widths>
<Available Frequency Range-List> ::=
<Available Frequency Range> [<Available Frequency Range-List>]
<Available Frequency Range> ::=
( <Start NCF> <End NCF> ) |
<FS defined by (n, m) containing contiguous available NCFs>
<Available NCFs> ::=
<Available NCF Granularity> [<Offset>]
-- Subset of supported n values given by p x n + q
-- where p is a positive integer
-- and q (offset) belongs to 0,..,p-1.
<Available Slot Widths> ::=
<Available Slot Width Granularity>
<Min Slot Width>
-- given by j x 12.5 GHz, with j a positive integer <Max Slot Width>
-- given by k x 12.5 GHz, with k a positive integer (k >= j)
Figure 17: Routing Information Model
5. Control-Plane Requirements
The control of flexi-grid networks places additional requirements on the GMPLS protocols. This section summarizes those requirements for signaling and routing.
5.1. Support for Media Channels
The control plane SHALL be able to support media channels, characterized by a single frequency slot. The representation of the media channel in the GMPLS control plane is the so-called "flexi-grid LSP". Since network media channels are media channels, an LSP may also be the control-plane representation of a network media channel. Consequently, the control plane will also be able to support network media channels.
5.1.1. Signaling
The signaling procedure SHALL be able to configure the nominal central frequency (n) of a flexi-grid LSP.
The signaling procedure SHALL allow a flexible range of values for the frequency slot width (m) parameter. Specifically, the control plane SHALL allow setting up a media channel with frequency slot width (m) ranging from a minimum of m = 1 (12.5 GHz) to a maximum of the entire C-band (the wavelength range 1530 nm to 1565 nm, which corresponds to the amplification range of erbium-doped fiber amplifiers) with a slot width granularity of 12.5 GHz.
The signaling procedure SHALL be able to configure the minimum width (m) of a flexi-grid LSP. In addition, the signaling procedure SHALL be able to configure local frequency slots.
The control-plane architecture SHOULD allow for the support of the L-band (the wavelength range 1565 nm to 1625 nm) and the S-band (the wavelength range 1460 nm to 1530 nm).
The signaling process SHALL be able to collect the local frequency slot assigned at each link along the path.
The signaling procedures SHALL support all of the RSA architectural models (R&SA, R+SA, and R+DSA) within a single set of protocol objects, although some objects may only be applicable within one of the models.
5.1.2. Routing
The routing protocol will support all functions described in [RFC4202] and extend them to a flexi-grid data plane.
The routing protocol SHALL distribute sufficient information to compute paths to enable the signaling procedure to establish LSPs as described in the previous sections. This includes, at a minimum, the data described by the information model in Figure 17.
The routing protocol SHALL update its advertisements of available resources and capabilities as the usage of resources in the network varies with the establishment or teardown of LSPs. These updates SHOULD be amenable to damping and thresholds as in other traffic engineering routing advertisements.
The routing protocol SHALL support all of the RSA architectural models (R&SA, R+SA, and R+DSA) without any configuration or change of behavior. Thus, the routing protocols SHALL be agnostic to the computation and signaling model that is in use.
5.2. Support for Media Channel Resizing
The signaling procedures SHALL allow the resizing (growing or shrinking) of the frequency slot width of a media channel or network media channel. The resizing MAY imply resizing the local frequency slots along the path of the flexi-grid LSP.
The routing protocol SHALL update its advertisements of available resources and capabilities as the usage of resources in the network varies with the resizing of LSPs. These updates SHOULD be amenable to damping and thresholds as in other traffic engineering routing advertisements.
5.3. Support for Logical Associations of Multiple Media Channels
A set of media channels can be used to transport signals that have a logical association between them. The control-plane architecture SHOULD allow multiple media channels to be logically associated. The control plane SHOULD allow the co-routing of a set of media channels that are logically associated.
5.4. Support for Composite Media Channels
As described in Sections 3.2.5 and 4.3, a media channel may be composed of multiple network media channels.
The signaling procedures SHOULD include support for signaling a single control-plane LSP that includes information about multiple network media channels that will comprise the single compound media channel.
The signaling procedures SHOULD include a mechanism to associate separately signaled control-plane LSPs so that the endpoints may correlate them into a single compound media channel.
The signaling procedures MAY include a mechanism to dynamically vary the composition of a composite media channel by allowing network media channels to be added to or removed from the whole.
The routing protocols MUST provide sufficient information for the computation of paths and slots for composite media channels using any of the three RSA architectural models (R&SA, R+SA, and R+DSA).
5.5. Support for Neighbor Discovery and Link Property Correlation
The control plane MAY include support for neighbor discovery such that a flexi-grid network can be constructed in a "plug-and-play" manner. Note, however, that in common operational practice, validation processes are used rather than automatic discovery.
The control plane SHOULD allow the nodes at opposite ends of a link to correlate the properties that they will apply to the link. Such a correlation SHOULD include at least the identities of the nodes and the identities that they apply to the link. Other properties, such as the link characteristics described for the routing information model in Figure 17, SHOULD also be correlated.
Such neighbor discovery and link property correlation, if provided, MUST be able to operate in both an out-of-band and an out-of-fiber control channel.
The control-plane and data-plane aspects of a flexi-grid system are fundamentally the same as a fixed-grid system, and there is no substantial reason to expect the security considerations to be any different.
A good overview of the security considerations for a GMPLS-based control plane can be found in [RFC5920].
[RFC6163] includes a section describing security considerations for WSON, and it is reasonable to infer that these considerations apply and may be exacerbated in a flexi-grid SSON system. In particular, the detailed and granular information describing a flexi-grid network and the capabilities of nodes in that network could put stress on the routing protocol or the out-of-band control channel used by the protocol. An attacker might be able to cause small variations in the use of the network or the available resources (perhaps by modifying the environment of a fiber) and so trigger the routing protocol to make new flooding announcements. This situation is explicitly mitigated in the requirements for the routing protocol extensions where it is noted that the protocol must include damping and configurable thresholds as already exist in the core GMPLS routing protocols.
7. Manageability Considerations
GMPLS systems already contain a number of management tools:
MIB modules exist to model the control-plane protocols and the network elements [RFC4802] [RFC4803], and there is early work to provide similar access through YANG. The features described in these models are currently designed to represent fixed-label technologies such as optical networks using the fixed grid; extensions may be needed in order to represent bandwidth, frequency slots, and effective frequency slots in flexi-grid networks.
There are protocol extensions within GMPLS signaling to allow control-plane systems to report the presence of faults that affect LSPs [RFC4783], although it must be carefully noted that these mechanisms do not constitute an alarm mechanism that could be used to rapidly propagate information about faults in a way that would allow the data plane to perform protection switching. These mechanisms could easily be enhanced with the addition of technology-specific reason codes if any are needed.
The GMPLS protocols, themselves, already include fault detection and recovery mechanisms (such as the PathErr and Notify messages in RSVP-TE signaling as used by GMPLS [RFC3473]). It is not anticipated that these mechanisms will need enhancement to support flexi-grid, although additional reason codes may be needed to describe technology-specific error cases.
[RFC7260] describes a framework for the control and configuration of data-plane Operations, Administration, and Maintenance (OAM). It would not be appropriate for the IETF to define or describe data-plane OAM for optical systems, but the framework described in RFC 7260 could be used (with minor protocol extensions) to enable data-plane OAM that has been defined by the originators of the flexi-grid data-plane technology (the ITU-T).
The Link Management Protocol (LMP) [RFC4204] is designed to allow the two ends of a network link to coordinate and confirm the configuration and capabilities that they will apply to the link. LMP is particularly applicable to optical links, where the characteristics of the network devices may considerably affect how the link is used and where misconfiguration or mis-fibering could make physical interoperability impossible. LMP could easily be extended to collect and report information between the endpoints of links in a flexi-grid network.
[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>.
[G.800]    International Telecommunication Union, "Unified functional
architecture of transport networks", ITU-T
Recommendation G.800, February 2012,
<http://www.itu.int/rec/T-REC-G.800/>.
[G.805]    International Telecommunication Union, "Generic functional
Recommendation G.805, March 2000,
<https://www.itu.int/rec/T-REC-G.805-200003-I/en>.
[G.8080]   International Telecommunication Union, "Architecture for
the automatically switched optical network", ITU-T
Recommendation G.8080/Y.1304, February 2012,
<https://www.itu.int/rec/T-REC-G.8080-201202-I/en>.
[G.870]    International Telecommunication Union, "Terms and
definitions for optical transport networks", ITU-T
Recommendation G.870/Y.1352, October 2012,
<https://www.itu.int/rec/T-REC-G.870/en>.
[G.872]    International Telecommunication Union, "Architecture of
optical transport networks", ITU-T Recommendation G.872,
October 2012,
<http://www.itu.int/rec/T-REC-G.872-201210-I>.
[RFC3945]  Mannie, E., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", RFC 3945,
[RFC4202]  Kompella, K., Ed., and Y. Rekhter, Ed., "Routing
Extensions in Support of Generalized Multi-Protocol Label
Switching (GMPLS)", RFC 4202, DOI 10.17487/RFC4202,
October 2005, <http://www.rfc-editor.org/info/rfc4202>.
[RFC4206]  Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
Hierarchy with Generalized Multi-Protocol Label Switching
(GMPLS) Traffic Engineering (TE)", RFC 4206,
[RFC5511]  Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
Used to Form Encoding Rules in Various Routing Protocol
Specifications", RFC 5511, DOI 10.17487/RFC5511,
[G.959.1-2013]
International Telecommunication Union, "Optical transport network physical layer interfaces", Update to ITU-T Recommendation G.959.1, 2013.
[RFC3473]  Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
[RFC4204]  Lang, J., Ed., "Link Management Protocol (LMP)", RFC 4204,
[RFC4397]  Bryskin, I. and A. Farrel, "A Lexicography for the
Interpretation of Generalized Multiprotocol Label
Switching (GMPLS) Terminology within the Context of the
ITU-T's Automatically Switched Optical Network (ASON)
Architecture", RFC 4397, DOI 10.17487/RFC4397,
February 2006, <http://www.rfc-editor.org/info/rfc4397>.
[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,
[RFC4783]  Berger, L., Ed., "GMPLS - Communication of Alarm
Information", RFC 4783, DOI 10.17487/RFC4783,
December 2006, <http://www.rfc-editor.org/info/rfc4783>.
[RFC4802]  Nadeau, T., Ed., Farrel, A., and , "Generalized
Multiprotocol Label Switching (GMPLS) Traffic Engineering
Management Information Base", RFC 4802,
DOI 10.17487/RFC4802, February 2007,
[RFC4803]  Nadeau, T., Ed., and A. Farrel, Ed., "Generalized
Multiprotocol Label Switching (GMPLS) Label Switching
Router (LSR) Management Information Base", RFC 4803,
[RFC5920]  Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
[RFC6163]  Lee, Y., Ed., Bernstein, G., Ed., and W. Imajuku,
"Framework for GMPLS and Path Computation Element (PCE)
Control of Wavelength Switched Optical Networks (WSONs)",
RFC 6163, DOI 10.17487/RFC6163, April 2011,
[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,
[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,
[RFC7260]  Takacs, A., Fedyk, D., and J. He, "GMPLS RSVP-TE
Extensions for Operations, Administration, and Maintenance
(OAM) Configuration", RFC 7260, DOI 10.17487/RFC7260,
June 2014, <http://www.rfc-editor.org/info/rfc7260>.
The authors would like to thank Pete Anslow for his insights and clarifications, and Matt Hartley and Jonas Maertensson for their reviews.
This work was supported in part by the FP-7 IDEALIST project under grant agreement number 317999.
Adrian Farrel
Old Dog Consulting
Email: adrian@olddog.co.uk
Email: daniel@olddog.co.uk
Xian Zhang
Email: zhang.xian@huawei.com
Cyril Margaria
Email: cmargaria@juniper.net
Qilei Wang
Ruanjian Avenue, Nanjing, China
Email: wang.qilei@zte.com.cn
Malcolm Betts
Email: malcolm.betts@zte.com.cn
Optics CTO
Via Trento 30 20059 Vimercate (Milano) Italy
Email: sergio.belotti@alcatel-lucent.com
Yao Li
Nanjing University
Email: wsliguotou@hotmail.com
Fei Zhang
Email: zhangfei7@huawei.com
Lei Wang
Email: wang.lei@bupt.edu.cn
Guoying Zhang
China Academy of Telecom Research
No.52 Huayuan Bei Road, Beijing, China Email: zhangguoying@ritt.cn
Takehiro Tsuritani
KDDI R&D Laboratories Inc.
2-1-15 Ohara, Fujimino, Saitama, Japan
Email: tsuri@kddilabs.jp
Lei Liu
UC Davis, United States
Email: leiliu@ucdavis.edu
Eve Varma
Email: eve.varma@alcatel-lucent.com
Young Lee
Jianrui Han
Sharfuddin Syed
Rajan Rao
Marco Sosa
Biao Lu
Abinder Dhillon
Felipe Jimenez Arribas
Andrew G. Malis
Email: agmalis@gmail.com
Huub van Helvoort
Hai Gaoming BV
Email: huubatwork@gmail.com
Oscar Gonzalez de Dios (editor)
Ronda de la Comunicacion s/n
Madrid  28050
Email: oscar.gonzalezdedios@telefonica.com
Ramon Casellas (editor)
Av. Carl Friedrich Gauss n.7
Castelldefels  Barcelona
Email: ramon.casellas@cttc.es
Fatai Zhang
Huawei Base, Bantian, Longgang District
Email: zhangfatai@huawei.com
Xihua Fu
No.118, Taibai Road, Yanta District
Email: fu.xihua@stairnote.com
Daniele Ceccarelli
Via Calda 5
Email: daniele.ceccarelli@ericsson.com
Iftekhar Hussain
140 Caspian Ct.
Sunnyvale, CA  94089
Email: ihussain@infinera.com


Reading Mastery Signature Edition Grade K (McGraw Hill, 2008) is a 136 lesson Direct Instruction reading program designed to efficiently introduce the essential elements of the reading code to low-performing and beginning readers.
Morningside's accompanying see-say fluency workbook provides three versions of each of ten slices to practice new skills through seeing and saying sounds, word parts, and words. Ten additional cumulative slices reinforce skills mastered along the way. This fluency program can also be used with Reading Mastery Classic 1 (McGraw Hill, 2003).
Students should be given each slice after successful completion of specific lessons in Reading Mastery Signature Edition Grade K. The list of slices, sounds in each slice, and what lessons each slice should follow is available in the Table of Contents for this program.
For best results, students should demonstrate accuracy in the sounds presented in each slice before starting on frequency building timings. For example, Slice 1 features the sounds for a, m, s, e, and r. Once students have completed RMSE Lesson 26 and can accurately read those sounds, they are ready to start practicing to fluency with celeration!
There are also ten Cumulative Slices. Once students have achieved the frequency AIM for Slices 1 and 2, they should proceed to Cumulative Slice 1-2. Once they've achieved the frequency AIM on that slice, they'll continue to Slice 3, then Slice 4, then Cumulative Slice 3-4. This cumulative pattern will continue throughout the program.
At the end of the program there is one Review Slice, where students will read sounds, word parts, and words from all ten slices.
*The Table of Contents also lists the progression of slices that accompany the "Fast Cycle" version of Reading Mastery Signature Grade K for above-average readers. More information about how to use the Fast Cycle can be found in the Reading Mastery Signature Edition: Series Guide for the Reading Strand (ISBN: 978-0-07-612675-0).


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You are here: Home Page > Arts & Humanities > Religion > Christianity > The Seer of Bayside
The Seer of Bayside
Veronica Lueken and the Struggle to Define Catholicism
Joseph P. Laycock
First definitive study of Veronica Lueken and the Baysiders
Offers insight into the ongoing struggle between lay Catholics and Catholic authority
In 1968, Veronica Lueken, a Catholic housewife in Bayside, Queens, New York, began to experience visions of the Virgin Mary. Over almost three decades, she imparted more than 300 messages from Mary, Jesus, and other heavenly personages. These revelations, which were sent all over the world through newsletters, billboards, and local television, severely criticized the liturgical changes of Vatican II and the wickedness of American society. Unless everyone repented, Lueken warned, a "fiery ball" would collide with the Earth, causing death and destruction around the world. When Catholic Church authorities tried to dismiss, discredit, and even banish her, Lueken declared Pope Paul VI a communist imposter, accused the Church of being in error since Vatican II, and sought new venues in which to communicate her revelations. Since her death in 1995, her followers have continued to gather in Flushing Meadows Park, Queens, to promote her message. Known as "the Baysiders," they believe that St. Robert Bellarmine's Church, where Lueken held vigils until they were banned, will someday become "the Lourdes of America" and that Lueken will be elevated to sainthood. Joseph P. Laycock draws on untapped archival materials and a wealth of ethnographic research to unfold the fascinating story of Veronica Lueken and the Baysiders. Scholars have characterized the Baysiders variously as a new religious movement, a form of folk piety, and a traditionalist sect, but members of the group regard themselves as loyal Catholics-maybe the last in existence. They are critical of the hierarchy, which they see as corrupted by modernism, but also spurn those ultra-traditionalist Catholic groups who believe that the papal see is vacant. Laycock shows how the Baysiders have deviated significantly from mainstream Catholic culture while keeping in dialogue with Church authorities; the persistence of the Baysiders and other Marian groups, he argues, has helped bring about greater amenability toward devotional culture and private revelation on the part of the hierarchy. The Seer of Bayside is an invaluable study of the perpetual struggle between lay Catholics and the institutional church over who holds the power to define Catholic culture.
Chapter 1: A Walk in the Park
Chapter 2: When the Roses are in Bloom
Chapter 3: The Battle of Bayside
Chapter 4: Flushing Meadows
Chapter 5: We Have Become A Spectacle to the World
Chapter 6: After Veronica
Chapter 7: A New Age of Mary
Joseph P. Laycock, Assistant Professor of Religious Studies, Texas State University
Joseph P. Laycock is an assistant professor of religious studies at Texas State University. He has published over a dozen peer-reviewed journal articles and is currently working on a project about the moral panic over role-playing games during the 1980s.
"The Seer of Bayside is an excellent book, and I recommend it highly. Laycock's study has much to offer beyond its obvious contributions to scholarship on American Catholicism and post-Vatican II devotional cultures, however. Indeed, students and scholars alike will find in The Seer of Bayside an exemplary model for engaging with subjugated discourses" - Grant Shoffstall, International Journal for the Study of New Religions
"Laycock has written a compelling and perceptive book on the Baysiders' devotional life and their relationship to institutional Roman Catholicism, for which he is to be commended." - Jane Shaw, Times Higher Education
"Joseph Laycock has given us a compelling and very readable account of the drama surrounding one of America's most significant Marian apparition groups." - David G. Bromley, Director, World Religions and Spirituality Project, and Professor of Religious Studies and Sociology, Virginia Commonwealth University
"Joseph Laycock has given us an extraordinarily intimate and insightful picture of one of the most significant contemporary Marian movements, described in a manner that will make it must reading for all students of religion, regardless of discipline." - Michael Barkun, Professor Emeritus of Political Science, Maxwell School of Citizenship and Public Affairs, Syracuse University
"Laycocks treatment of the apocalyptic movement that grew from Luekens visions is sensitive, sophisticated, and evocative. As with all excellent studies of marginal religious groups, The Seer of Bayside sheds as much light on the center as it does on the fringes. The book offers powerful leverage into abiding questions about Catholics relationship with ecstatic religious experience, sacred places, and modern forms of civil and religious authority." - ohn C. Seitz, author of No Closure: Catholic Practice and Boston's Parish Shutdowns
The Battle of Bayside, Queens: a Q&A
From 1970 to 1975, Bayside Hills'a pleasant and prosperous neighborhood in Northeastern Queens, a borough of New York City'was embroiled in controversy when a local woman named Veronica Lueken announced that the Virgin Mary was appearing to her at St. Robert Bellarmine's Church. At first Lueken was regarded as a 'local kook.' Then, in 1973, a traditionalist Catholic group from Canada called The Pilgrims of St. Michael declared her 'the seer of the age' and pilgrims started to flock to Bayside Hills.
Prophecy, demonology, and the Extraordinary Synod of Bishops on the Family
From 5-19 October 2014, Pope Francis held the Extraordinary Synod of Bishops on the Family in Rome. The purpose of the synod was to discuss the Church's stance on such issues as divorce, birth control, and especially, the legalization of gay marriage.
The American Catholic Revolution
Mark S. Massa, S.J.
The Catholic Labyrinth
Peter McDonough
Speak of the Devil
Fighting Fundamentalist
Markku Ruotsila
In the Lógos of Love
James L. Heft, Una M. Cadegan
How Repentance Became Biblical
David A. Lambert
Faith in the New Millennium
Matthew Avery Sutton, Darren Dochuk
Heath W. Carter
Born of Conviction
Joseph T. Reiff
The Evolution of Atheism
Stephen LeDrew
New Testament Christianity in the Roman World
Harry O. Maier
Paul Froese
Arts & Humanities > Religion > Christianity
Arts & Humanities > Religion > Religious Studies > Religious Issues & Debates
Social Sciences > Sociology > Sociology of Religion
Arts & Humanities > Religion > Christianity > Christian Churches & Denominations > Roman Catholicism, Roman Catholic Church

redpajama_set_name: RedPajamaCommonCrawl


That's rather wonderful! Sometimes the most unassuming plants can put on the best displays.
What a beautiful flower, I love it. And so nice you can spread the joy to others with cuttings when it gets big enough!
Oh WOW what a nice surprise!
That's beautiful -- what a treat!


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Hyundai Motor receives two AutomotiveINNOVATIONS awards
Hyundai Motor receives significant PwC and CAM awards for pioneering product strategy
The awards were accepted by Jürgen Keller, Managing Director Hyundai Motor Germany
Hyundai Kona Electric and NEXO were noted as important innovation drivers
9 July 2019 - Hyundai has received two further major awards for the future-oriented direction of its drive technologies.
The company was honoured for the first time as 'Most Innovative Volume Brand' and 'Most Innovative Volume Brand - Alternative Drives' at the 2019 AutomotiveINNOVATIONS Awards evening by the Center of Automotive Management (CAM) and PricewaterhouseCoopers (PwC).
Jürgen Keller, Managing Director of Hyundai Motor Germany, accepted the prizes at a festive gala event in the Sky Lobby on the 48th floor of the PwC company headquarters.
Hyundai has been committed to sustainability for a long time. The company's words were followed by deeds that resulted in numerous innovations. Hyundai is currently the only manufacturer in the world to offer all major alternative drive forms in its series production: full-electric, hybrid, 48-volt mild hybrid, plug-in hybrid, and fuel cell.
Jürgen KellerManaging Director Hyundai Motor Germany
Kona Electric - the electric car with the highest range in the small SUV segment
The innovations in alternative drive systems earned Hyundai success in the 'Most Innovative Volume Brand' category, which Hyundai completed with a total of 43 index points ahead of Ford and VW. "One of the reasons for this is the particularly high proportion of innovations (almost 18 per cent) that can be attributed to alternative drive systems", according to the jury's statement. These include, for example, the Hyundai Kona Electric, the most wide-ranging battery electric vehicle in the small SUV segment.
NEXO impresses with higher efficiency
The jury also considers the Hyundai NEXO to be one of the most important innovators: "In addition to its fuel cell drive, it features a Blind Spot View Monitor, the Highway Driving Assist function and the Remote Parking function, which enables a vehicle to be parked fully automatically for the first time in this segment."
Hyundai Kona Electric and NEXO also play a decisive role in the presentation of the 'Most Innovative Volume Brand – Alternative Drives' award. With the new NEXO, Hyundai is already offering the second generation Fuel Cell vehicle after the 2013 released ix35 Fuel Cell, which is the world's first series-produced fuel cell vehicle. The range of 666 kilometres (according to WLTP standard) also played an important role, making the NEXO the ideal alternative drive option for long distances.
CAM database as basis for innovation study
The awards are based on a study among car manufacturers and suppliers, and on the CAM database of the independent scientific institute for empirical automotive and mobility research Center of Automotive Management in Bergisch-Gladbach, which is headed by the well-known car expert Prof. Dr. Stefan Bratzel. The most outstanding innovations of the year within the automotive industry are determined based on this data.
Hyundai Motor Introduces Electric Double-Decker Bus
Hyundai's 'Design Your Own World' CES 2019 Exhibition
Hyundai Motor Advances 'Future Mobility' Vision at Seoul Motor Show


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Green Brick Partners Closes 4.0% Senior Unsecured Notes Offering
Green Brick Partners has issued $75.0 million of senior unsecured notes due in 2026 at 4.0% to Prudential Private Capital in a Section 4(a)(2) private placement transaction
PLANO, Texas, Aug. 13, 2019 (GLOBE NEWSWIRE) -- Green Brick Partners, Inc. (Nasdaq: GRBK) ("Green Brick") is pleased to announce that Green Brick has issued $75.0 million of senior unsecured notes due in 2026 at a fixed rate of 4.00% per annum to Prudential Private Capital in a Section 4(a)(2) private placement transaction. The Company expects to use the net proceeds from the issuance of the senior unsecured notes to repay borrowings under the Company's existing revolving credit facilities.
"Green Brick Partners is very pleased to announce our inaugural issuance of senior unsecured notes," said Richard Costello, CFO of Green Brick Partners. "Our superior credit metrics allowed us to price 7-year notes at a fixed rate at 4.00%. This rate is only slightly higher than the long-term rates paid by the lower-leveraged large-cap builders and more attractive than the long-term rates paid by all small-cap and all mid-cap builders."
Principal on the senior unsecured notes is required to be paid in increments of $12.5 million on August 8, 2024 and $12.5 million on August 8, 2025. The final principal payment of $50.0 million is due on August 8, 2026.
Jim Brickman, CEO of Green Brick Partners, added "this transaction represents another positive step in Green Brick's long-term balance sheet strategy by laddering debt maturities, locking-in long-term borrowings at attractive rates, enabling us to have additional financial flexibility, and partnering with a world-class organization in Prudential Private Capital. The additional proceeds will enable us to continue to grow while striving to deliver the best risk-adjusted returns in the industry."
The senior unsecured notes have not been, and will not be, registered under the U.S. Securities Act of 1933, as amended (the "Act") or any state securities laws and may not be offered or sold in the United States absent registration or an applicable exemption from the registration requirements of the Act and applicable state securities laws.
"At Prudential Private Capital, our goal is to build ongoing relationships not only with solid companies, but also with excellent management teams. Thus, we are excited to provide $75 million of long-term, fixed-rate debt capital to support Green Brick's growth initiatives," said Brooke Ansel, Director of Prudential Private Capital. "We want to help businesses achieve their most ambitious goals in any market environment. From the outset of our connection with Green Brick, it was evident that we shared similar values in terms of a relationship-oriented approach to business."
For additional details, please refer the Form 8-K that was filed with the Securities and Exchange Commission on August 8, 2019.
About Green Brick Partners, Inc.:
Green Brick Partners, Inc. (Nasdaq: GRBK) is a diversified homebuilding and land development company. Green Brick owns a controlling interest in five homebuilders in Dallas, Texas (CB JENI Homes, Normandy Homes, Southgate Homes, Centre Living Homes, and Trophy Signature Homes), as well as a homebuilder in Atlanta, Georgia (The Providence Group) and a homebuilder in Port St. Lucie, Florida (GHO Homes). Green Brick also owns a noncontrolling interest in Challenger Homes in Colorado Springs, Colorado and retains interests in related financial services platforms, including Green Brick Title, Providence Group Title, and Green Brick Mortgage. The Company is engaged in all aspects of the homebuilding process, including land acquisition and development, entitlements, design, construction, marketing, and sales for its residential neighborhoods and master planned communities. For more information about Green Brick Partners Inc.'s homebuilding partners, please visit https://greenbrickpartners.com/team-builders/.
About Prudential Private Capital:
For more than 75 years, Prudential Private Capital has been partnering with a wide range of corporations, sponsors, and institutions to provide valuable insights, guidance, and customized capital solutions that enable them to achieve their growth and funding goals. In an industry where capital can seem like a commodity and relationships often fleeting and transactional, we are known for building enduring local partnerships based on a steady and patient commitment to our partners' long-term capital needs. With regional teams in 14 offices around the world, we manage a portfolio of nearly $89 billion (as of 6/30/19). For more information about Prudential Private Capital, please visit https://prudentialprivatecapital.com.
Forward-Looking and Cautionary Statements:
This press release is for information only, does not constitute an offer to sell or the solicitation of an offer to buy any security and shall not constitute an offer, solicitation or sale of any securities in any jurisdiction in which such offer, solicitation or sale would be unlawful.
Any statements in this press release about Green Brick's expectations, beliefs, plans, objectives, prospects, financial condition, assumptions or future events or performance that are not historical facts are forward-looking statements. These statements are often, but not always, made through the use of words or phrases such as "may," "will," "should," "predicts," "potential," "expects," "future," "positioned," "believes," "projects," "estimates" and similar expressions, as well as statements in the future tense. These statements are based on assumptions that Green Brick has made in light of its experience in the industry as well as its perceptions of historical trends, current conditions, expected future developments and other factors it believes are appropriate under the circumstances, as of the date of this press release. All such forward-looking statements involve estimates and assumptions that are subject to factors that could cause actual results to differ materially from the results expressed in the statements, and you should not place undue reliance on any such forward-looking statements. Among the factors that could cause actual results to differ materially are the following: general economic conditions, seasonality, cyclicality and competition in the homebuilding industry; the failure to recruit, retain and develop highly skills and competent employees; management and integration of acquisitions; labor and raw material shortages; an inability to acquire land for reasonable prices; an inability to develop and sell communities; government regulation risks; mortgage financing availability and volatility; severe weather or natural disasters; difficulty in obtaining sufficient capital; poor relations with community residents; and our debt and related service obligations. Additional factors that could cause actual results to differ are discussed in the "Risk Factors" and "Management's Discussion and Analysis of Financial Condition and Results of Operations" in the Company's annual and quarterly reports filed with the Securities and Exchange Commission. Green Brick undertakes no obligation to update any forward-looking statement except as required by law.
Contact: Shalott Cecchini
scecchini@greenbrickpartners.com
www.greenbrickpartners.com


8x10s,1 set of wallets ,and 1 11x14 print.
Check out this great article about bigger wall prints! Its so true!
SHe is just precious and we had so much fun with all her girly stuff!
These were all taken at my new studio so even if its cold and yucky we can still get beautiful images.
This week has been a photographers dream for winter I have been taking lots of images of Madilyn that i cant wait to work on.
$100 for 3hrs of learning about your camera and the functions. You will also learn how to shoot in manual and learn about all your auto modes. I will talk to you about lenses and what are the best kind for you. We will practice hands on and I will have a folder with handouts for you to take home.
It starts at 9:30am and will last till 12:30.
This will be a fun and casual learning environment.
All Skill levels are welcome to come and learn.
Standout Mounts at 45% off current pricing!
My lab is running a sale this week only, so I am passing the savings on to you! It may be the only time to purchase at such low prices! Enjoy!
Buy two Standout mounts and get a $50 print credit on your next session.
Buy three Standout mounts and get a $75 print credit on your next session.


How Much Do Penguins Cost?
Many people wonder how much do penguins cost when they see these cuddly and cute birds on tv or in a zoo. After all, who would not like to own an animal that looks so lovely and almost like a small toy. Well, if you have been looking online for how much penguins cost, you might be in for a surprise as you cannot buy penguins like any other pet. There are several conditions that you need to fulfill to make sure the penguins will be happy and comfortable.
First off, penguins need cold conditions to live and survive. The temperatures in their native Antarctica can plunge several degrees below zero and penguins need to be in the cold weather for their biology to function properly. If the weather around them is too hot or not cool enough, they will not be comfortable.
Also, penguins are social creatures that need to be close to other penguins to communicate, mate, and socialize. This is why penguins need to live with other penguins and if you are thinking of buying a penguin, be prepared to buy more than one or two of them.
While it is near impossible to legally obtain a penguin as a pet, as there are several conditions you need to fulfill and permits that you need to get in order to even consider owning a penguin. Even then, you can only get a penguin from a facility that holds USDA permits. Also, the penguin must be born in captivity, and it should not be a penguin that has been isolated from its natural habitat. As penguins fall under protected species, you cannot simply go to a pet shop to buy a penguin.
Along with that, you have to consider the various costs that you will have to bear in order to keep a penguin safe and happy outside of its natural habitat. Let's take a look at the cost of some of the arrangements that you will have to make in case you buy a penguin.
Feed – Penguins eat a lot of fish or krill when they are living in their natural habitat. To keep a penguin well-fed in captivity, you will need a large supply of fish that can come up to 400 pounds of fish a year per penguin. Penguins feed several times a day so they will need constant attention for their feeding times. Feeding a number of penguins can cost several thousands of dollars depending on the kind of fish you choose to feed them.
As you will be taking the penguins away from their natural habitat, you will also need to feed them with vitamins and supplements to make up for the loss of nutrients from exposure the sun and water.
Shelter Arrangements – Depending on the size and number of the penguins, you will need to make special living arrangements for the number of birds you plan to get. Penguins like to live, eat, and move around in groups so you will need space for them accordingly. Penguins require living spaces that have vegetation, cold water, pools of clean salt water, and temperature control.
Penguins are used to living in cold environments, and that's why they need really low temperatures to survive out of their natural environment. Maintaining a pool of salt water is also expensive as penguins need deep water to swim and dive into. The pool will require regular cleaning because penguins often poop in the water they swim in.
Medical Expenses – Penguins are unlike any other birds so you will need a specialist vet to examine and treat any medical issues that penguins might face. You also have to consider that a vet might charge more to examine a penguin as it is an exotic bird.
Transporting a penguin to a vet's clinic or getting a vet to examine a penguin at your house might add to the expenses. If you need any specialized vitamins or medicines for the penguin, you need to factor in that cost as well. In case a penguin falls sick, you might need to visit the vet in an emergency and that can add to the costs of keeping a penguin.
Cost of Permits – If you are willing to fulfill all the above-mentioned conditions, there are several other considerations as well. You will need to get the appropriate permits that can vary in cost depending on your local authorities.
Other Considerations – There are about 18 species of penguins present in the Southern hemisphere, and most of them are considered endangered. It is also illegal to buy a penguin and keep it as a pet. You also need to consider the ethical fact that you will be taking an endangered species out of its natural habitat to live in captivity. A penguin will never be as happy and healthy in captivity as it would be in a natural environment.
As buying a penguin is a near impossible task and it is also illegal, the next best thing you can do is adopt a penguin at your local zoo or any zoo in your country. You can visit the zoo's website and donate an appropriate sum for the well-being and care of the penguins in that zoo. Different zoos offer adoption programs, and you can check one out as per your budget and requirements.
There are several advantages of adopting a penguin as you will be contributing to the welfare of a species that is under the threat of extinction. Donating to zoos for penguin adoption is also a great way to spread useful knowledge about these wonderful birds.
So, do you still think you should buy a penguin? We hope that instead of buying you should consider adopting a penguin at a local zoo. Do let us know if you have any questions or queries about how much penguins cost. Our team will do its best to answer your questions in the comment section.