PCE Working Group Y. Lee
Internet Draft Samsung
Intended status: Standard Track H. Zheng (Editor)
Expires: February 28, 2021 Huawei Technologies
R. Casellas
R. Vilalta
CTTC
D. Ceccarelli
F. Lazzeri
Ericsson
August 27, 2020
PCEP Extension for Flexible Grid Networks
draft-ietf-pce-flexible-grid-04
Abstract
This document provides the Path Computation Element Communication
Protocol (PCEP) extensions for the support of Routing and Spectrum
Assignment (RSA) in Flexible Grid networks.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with
the provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on February 28, 2020.
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Copyright Notice
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This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Terminology ................................................. 3
2. Requirements Language ....................................... 3
3. Introduction ................................................ 3
4. Spectrum Assignment (SA) Object ............................. 4
4.1. Frequency-Slot Selection TLV ........................... 6
4.2. Frequency-slot Restriction Constraint TLV .............. 8
4.2.1. Frequency-Slot Restriction Field ................. 10
5. Encoding of a RSA Path Reply ............................... 10
5.1. Error Indicator........................................ 11
5.2. NO-PATH Indicator ..................................... 11
6. Manageability Considerations ............................... 12
6.1. Control of Function and Policy ........................ 12
6.2. Information and Data Models ........................... 12
6.3. Verifying Correct Operation ........................... 12
6.4. Requirements on Other Protocols and Functional Components13
6.5. Impact on Network Operation ........................... 13
7. Implementation Status ...................................... 13
8. Security Considerations .................................... 14
9. IANA Considerations ........................................ 14
9.1. New PCEP Object........................................ 14
9.2. New PCEP TLV: Frequency Slot Selection TLV ............ 14
9.3. New PCEP TLV: Frequency Slot Restriction Constraint TLV.14
9.4. New PCEP TLV: Spectrum Allocation TLV ................. 15
9.5. New No-Path Reasons ................................... 15
9.6. New Error-Types and Error-Values ...................... 16
9.7. New Error-Values for Existing Error Type (24) ......... 16
10. References ................................................ 16
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10.1. Normative References ................................. 16
10.2. Informative References ............................... 17
11. Contributors .............................................. 18
Authors' Addresses ............................................ 19
1. Terminology
This document uses the terminology defined in [RFC4655], [RFC5440]
and [RFC7698].
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Introduction
[RFC4655] defines a Path Computation Element (PCE) based path
computation architecture and explains how a Path Computation Element
(PCE) may compute Label Switched Paths (LSP) in Multiprotocol Label
Switching Traffic Engineering (MPLS-TE) and Generalized MPLS (GMPLS)
networks at the request of Path Computation Clients (PCCs). A PCC
is said to be any network component that makes such a request and
may be, for instance, an Optical Switching Element within a
Wavelength Division Multiplexing (WDM) network. The PCE, itself,
can be located anywhere within the network, and may be within an
optical switching element, a Network Management System (NMS) or
Operational Support System (OSS), or may be an independent network
server.
The PCE communications Protocol (PCEP) is the communication protocol
used between a PCC and a PCE, and can also be used between
cooperating PCEs. [RFC4657] sets out the common protocol
requirements for PCEP. Additional application-specific requirements
for PCEP are deferred to separate documents.
[RFC8780] provides the PCEP extensions for the support of Routing
and Wavelength Assignment (RWA) in Wavelength Switched Optical
Networks (WSON) based on the requirements specified in [RFC6163] and
[RFC7449].
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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). [RFC7698] provides Framework and
Requirements for GMPLS-Based Control of Flexi-Grid Dense Wavelength
Division Multiplexing (DWDM) Networks.
The terms "Routing and Spectrum Assignment" (RSA) is introduced in
[RFC7698] to refer to the 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.
The term "Spectrum Switched Optical Networks" is also introduced in
[RFC7698] to refer to a flexi-grid enabled DWDM network, which can
be controlled by a GMPLS or PCE control plane.
This document provides PCEP extensions to support RSA in SSONs.
Figure 2 shows one typical PCE based implementation, which is
referred to as the Combined Routing and Spectrum Assignment (R&SA)
[RFC7698]. With this architecture, the two processes of routing and
spectrum assignment are accessed via a single PCE. This architecture
is the base architecture from which the PCEP extensions are
specified in this document.
+----------------------------+
+-----+ | +-------+ +--+ |
| | | |Routing| |SA| |
| PCC |<----->| +-------+ +--+ |
| | | |
+-----+ | PCE |
+----------------------------+
Figure 1 Combined Process (R&SA) architecture
4. Spectrum Assignment (SA) Object
This document aligns with GMPLS extensions for PCEP [RFC8779] for
generic property such as label, label-set and label assignment
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noting that frequency is a type of label. Frequency restrictions and
constraints are also formulated in terms of labels per [RFC7579].
Spectrum allocation can be performed by the PCE by different means:
(a) By means of Explicit Label Control (ELC) where the PCE
allocates which label to use for each interface/node along the
path.
(b) By means of a Label Set where the PCE provides a range of
potential frequency slots to allocate by each node along the path.
Option (b) allows distributed spectrum allocation (performed during
signaling) to complete spectrum assignment.
Additionally, given a range of potential spectrums to allocate, a PC
Request SHOULD convey the heuristic / mechanism to the allocation.
The format Routing Backus-Naur Form (RBNF) [RFC5511] of a PCReq
message per [RFC5440] after incorporating the Spectrum Assignment
(SA) object is as follows:
<PCReq Message> ::= <Common Header>
[<svec-list>]
<request-list>
Where:
<request-list>::=<request>[<request-list>]
<request>::= <RP>
<GENERALIZED ENDPOINTS>
[ <SA> ]
[other optional objects...]
If the SA object is present in the request, it MUST be encoded after
the GENERALIZED ENDPOINTS object.
SA Object-Class is (TBD1) (To be assigned by IANA).
SA Object-Type is 1.
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The format of the Spectrum Assignment (SA) object body is as
follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Flags |M|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Frequency-Slot Selection TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Frequency-Slot Restriction Constraint TLV |
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Optional TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2 SA Object
o Reserved (16 bits)
o Flags (16 bits)
One Flag bit is allocated as follows:
M (Mode - 1 bit): M bit is used to indicate the mode of spectrum
assignment. When M bit is set to 1, this indicates that the
spectrum assigned by the PCE must be explicit. That is, the
selected way to convey the allocated spectrum is by means of
Explicit Label Control (ELC) [RFC4003] for each hop of a
computed LSP. Otherwise, the spectrum assigned by the PCE
needs not be explicit (i.e., it can be suggested in the form
of label set objects in the corresponding response, to allow
distributed SA. In such case, the PCE MUST return a Label Set
Field as described in Section 2.6 of [RFC7579] in the
response. See Section 5 of this document for the encoding
discussion of a Label Set Field in a PCRep message.
4.1. Frequency-Slot Selection TLV
The Frequency-Slot Selection TLV is used to indicate the frequency-
slot selection constraint in regard to the order of frequency-slot
assignment to be returned by the PCE. This TLV is only applied when
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M bit is set in the SA Object specified in Section 4. This TLV
SHOULD NOT be present and MUST be ignored when the M bit is cleared.
The Frequency-Slot Selection sub-TLV value field is defined as:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S| FSA Method | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where:
Frequency-Slot Assignment (FSA) Method (7 bits):
0: unspecified (any); This does not constrain the SA method
used by a PCC This value is implied when the
Frequency-Slot Selection sub-TLV is absent.
1: First-Fit. All the feasible frequency slots are numbered3
(based on "n" parameter), and this SA method chooses the
available frequency-slot with the lowest index, where "n" is
the parameter in f = 193.1 THz + n x 0.00625 THz where 193.1
THz is the ITU-T "anchor frequency" and "n" is a positive
integer including 0 [RFC7698].
2: Random. This SA method chooses a feasible frequency-slot
value of "n" randomly.
3-127: Unassigned.
S (Symmetry, 1 bit): This flag is only meaningful when the request
is for a bidirectional LSP (see [RFC5440]).
0 denotes requiring the same frequency-slot in both directions;
1 denotes that different spectrums on both directions are
allowed.
IANA is to allocate a new PCEP TLV type, Frequency-Slot Selection
TLV (TBD2) in the "PCEP TLV Type Indicators" subregistry
(http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-tlv-type-
indicators).
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The processing rules for this TLV are as follows:
If a PCE does not support the attribute(s), its behavior is
specified below:
- S bit clear not supported: a PathErr MUST be generated with
The Error Code "Routing Problem" (24) with error sub-code
"Unsupported Frequency slot Selection Symmetry value" (TBD3).
- FSA method not supported: a PathErr MUST be generated with the
Error Code "Routing Problem" (24) with error sub-code
"Unsupported Frequency Slot Assignment value" (TBD4).
4.2. Frequency-slot Restriction Constraint TLV
For any request that contains a Frequency-slot assignment, the
requester (PCC) must be able to specify a restriction on the
frequency-slots to be used. This restriction is to be interpreted by
the PCE as a constraint on the tuning ability of the origination
laser transmitter or on any other maintenance related constraints.
The format of the Frequency-Slot Restriction Constraint TLV is as
follows:
<Frequency-lot Restriction Constraint> ::=
(<Action>
<Link Identifiers> <Freq-slot Restriction>)...
Where
<Link Identifiers> ::= <Link Identifier> [<Link Identifiers>]
See Section 4.3.1 in [RFC8780] for the encoding of the Link
Identifiers Field.
IANA is to allocate a new PCEP TLV, the Frequency slot Restriction
Constraint TLV type (TBD5). This TLV MAY appear more than once to be
able to specify multiple restrictions.
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The TLV data is defined as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Action | Count | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Identifiers |
| . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Frequency Slot Restriction Field |
// . . . . //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3 spectrum Restriction Constraint TLV Encoding
o Action: 8 bits
0 - Inclusive List indicates that one or more link identifiers
are included in the Link Set. Each identifies a separate link
that is part of the set.
1 - Inclusive Range indicates that the Link Set defines a
range of links. It contains two link identifiers. The first
identifier indicates the start of the range (inclusive). The
second identifier indicates the end of the range (inclusive).
All links with numeric values between the bounds are
considered to be part of the set. A value of zero in either
position indicates that there is no bound on the corresponding
portion of the range. Note that the Action field can be set to
0 when unnumbered link identifier is used.
o Count: The number of the link identifiers (8 bits)
Note that a PCC MAY add a frequency slot restriction that applies to
all links by setting the Count field to zero and specifying just a
set of frequency slots.
Note that all link identifiers in the same list must be of the same
type.
o Reserved: Reserved for future use (16 bits)
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o Link Identifiers: Identifies each link ID for which restriction
is applied. The length is dependent on the link format and the Count
field. See Section 4.3.1 in [RFC8780] for Link Identifier encoding.
4.2.1. Frequency-Slot Restriction Field
The Frequency-Slot Restriction Field of the Frequency slot
restriction TLV is encoded as defined in section 4.2 of [RFC8363].
5. Encoding of a RSA Path Reply
This section provides the encoding of a RSA Path Reply, in the
PCRep/PCUpd message, for frequency slot allocation as discussed in
Section 4. Spectrum Allocation TLV IANA is to allocate a new PCEP
TLV type, the Spectrum Allocation TLV type (TBD6). The TLV data is
defined as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |M|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Identifier |
| . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Allocated Spectrum(s) |
// . . . . //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4 Spectrum Allocation TLV Encoding
o Type (16 bits): The type of the TLV.
o Length (15 bits): The length of the TLV including the Type and
Length fields.
o M (Mode): 1 bit
- 0 indicates the allocation is under Explicit Label Control.
- 1 indicates the allocation is expressed in Label Sets.
Note that all link identifiers in the same list must be of the same
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type.
o Link Identifier (variable): Identifies the interface to which
assignment spectrum(s) is applied. See Section 3.3 for Link
Identifier encoding.
o Allocated Spectrum(s) (variable): Indicates the allocated
spectrum(s) to the link identifier. See Section 3.3.1 for encoding
details.
This TLV is encoded as an attributes TLV, per [RFC5420], which is
carried in the ERO LSP Attribute Subobjects per [RFC7570].
5.1. Error Indicator
To indicate errors associated with the RSA request, a new Error Type
(TDB) and subsequent error-values are defined as follows for
inclusion in the PCEP-ERROR Object:
A new Error-Type (TBD7) and subsequent error-values are defined as
follows:
Error-Type=TBD7; Error-value=1: if a PCE receives a RSA
request and the PCE is not capable of processing the request
due to insufficient memory, the PCE MUST send a PCErr message
with a PCEP-ERROR Object (Error-Type=TDB) and an Error-
value(Error-value=1). The PCE stops processing the request.
The corresponding RSA request MUST be cancelled at the PCC.
Error-Type=TBD7; Error-value=2: if a PCE receives a RSA
request and the PCE is not capable of RSA computation, the PCE
MUST send a PCErr message with a PCEP-ERROR Object (Error-
Type=TDB) and an Error-value (Error-value=2). The PCE stops
processing the request. The corresponding RSA computation
MUST be cancelled at the PCC.
5.2. NO-PATH Indicator
To communicate the reason(s) for not being able to find RSA for the
path request, the NO-PATH object can be used in the corresponding
response. The format of the NO-PATH object body is defined in
[RFC5440]. The object may contain a NO-PATH-VECTOR TLV to provide
additional information about why a path computation has failed.
One new bit flag is defined to be carried in the Flags field in the
NO-PATH-VECTOR TLV carried in the NO-PATH Object.
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Bit TBD8: When set, the PCE indicates no feasible route was
found that meets all the constraints (e.g., spectrum
restriction, etc.) associated with RSA.
6. Manageability Considerations
Manageability of SSON Routing and Spectrum Assignment (RSA) with PCE
must address the following considerations:
6.1. Control of Function and Policy
In addition to the parameters already listed in Section 8.1 of
[RFC5440], a PCEP implementation SHOULD allow configuring the
following PCEP session parameters on a PCC:
The ability to send a Flexi-Grid RSA request.
In addition to the parameters already listed in Section 8.1 of
[RFC5440], a PCEP implementation SHOULD allow configuring the
following PCEP session parameters on a PCE:
The support for Flexi-Grid RSA.
A set of Flexi-Grid RSA specific policies (authorized sender,
request rate limiter, etc).
These parameters may be configured as default parameters for any
PCEP session the PCEP speaker participates in, or may apply to a
specific session with a given PCEP peer or a specific group of
sessions with a specific group of PCEP peers.
6.2. Information and Data Models
Extensions to the PCEP YANG module may include to cover the Flexi-
Grid RSA information introduced in this document. Liveness Detection
and Monitoring Mechanisms defined in this document do not imply any
new liveness detection and monitoring requirements in addition to
those already listed in section 8.3 of [RFC5440].
6.3. Verifying Correct Operation
Mechanisms defined in this document do not imply any new
verification requirements in addition to those already listed in
section 8.4 of [RFC5440].
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6.4. Requirements on Other Protocols and Functional Components
The PCE Discovery mechanisms ([RFC5089] and [RFC5088]) may be used
to advertise Flexi-Grid RSA path computation capabilities to PCCs.
This draft has requirements on other protocols (ERO objects, etc.
which are under TEAS or CCAMP.)
6.5. Impact on Network Operation
Mechanisms defined in this document do not imply any new network
operation requirements in addition to those already listed in
section 8.6 of [RFC5440].
7. Implementation Status
[NOTE TO RFC EDITOR: This whole section and the reference to
[RFC7942] is to be removed before publication as an RFC]
This section records the status of known implementations of the
protocol defined by this specification at the time of posting of
this Internet-Draft, and is based on a proposal described in
[RFC7942].
The description of implementations in this section is intended to
assist the IETF in its decision processes in progressing drafts to
RFCs. Please note that the listing of any individual implementation
here does not imply endorsement by the IETF. Furthermore, no effort
has been spent to verify the information presented here that was
supplied by IETF contributors. This is not intended as, and must
not be construed to be, a catalog of available implementations or
their features. Readers are advised to note that other
implementations may exist.
According to [RFC7942], "this will allow reviewers and working
groups to assign due consideration to documents that have the
benefit of running code, which may serve as evidence of valuable
experimentation and feedback that have made the implemented
protocols more mature. It is up to the individual working groups to
use this information as they see fit".
At the time of posting the -04 version of this document, there are
no known implementations of this mechanism. It is believed that two
vendors are considering prototype implementations, but these plans
are too vague to make any further assertions.
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8. Security Considerations
This document has no requirement for a change to the security models
within PCEP. However, the additional information distributed in
order to address the RSA problem represents a disclosure of network
capabilities that an operator may wish to keep private.
Consideration should be given to securing this information.
9. IANA Considerations
IANA is requested to make allocations from the sub-registries as
described in the following sections.
9.1. New PCEP Object
As described in Section 4.1, a new PCEP Object is defined to carry
frequency-slot assignment related constraints. IANA is to allocate
the following from "PCEP Objects" sub-registry
(http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-objects):
Object Class Name Object Reference
Value Type
---------------------------------------------------------
TBD1 SA 1: Spectrum Assignment [This.I-D]
9.2. New PCEP TLV: Frequency Slot Selection TLV
As described in Sections 4.2, a new PCEP TLV is defined to indicate
spectrum selection constraints. IANA is to allocate this new TLV
from the "PCEP TLV Type Indicators" subregistry
(http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-tlv-type-
indicators).
Value Description Reference
---------------------------------------------------------
TBD2 Spectrum Selection [This.I-D]
9.3. New PCEP TLV: Frequency Slot Restriction Constraint TLV
As described in Section 4.3, a new PCEP TLV is defined to indicate
wavelength restriction constraints. IANA is to allocate this new TLV
from the "PCEP TLV Type Indicators" subregistry
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(http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-tlv-type-
indicators).
Value Description Reference
---------------------------------------------------------
TBD5 Frequency Slot Restriction [This.I-D]
Constraint
9.4. New PCEP TLV: Spectrum Allocation TLV
As described in Section 5, a new PCEP TLV is defined to indicate the
allocation of freq-slots(s) by the PCE in response to a request by
the PCC. IANA is to allocate this new TLV from the "PCEP TLV Type
Indicators" subregistry
(http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-tlv-type-
indicators).
Value Description Reference
---------------------------------------------------------
TBD6 Spectrum Allocation [This.I-D]
9.5. New No-Path Reasons
As described in Section 4.3, a new bit flag are defined to be
carried in the Flags field in the NO-PATH-VECTOR TLV carried in the
NO-PATH Object. This flag, when set, indicates that no feasible
route was found that meets all the RSA constraints (e.g., spectrum
restriction, signal compatibility, etc.) associated with a RSA path
computation request.
IANA is to allocate this new bit flag from the "PCEP NO-PATH-VECTOR
TLV Flag Field" subregistry
(http://www.iana.org/assignments/pcep/pcep.xhtml#no-path-vector-
tlv).
Bit Description Reference
-----------------------------------------------------
TBD8 No RSA constraints met [This.I-D]
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9.6. New Error-Types and Error-Values
As described in Section 5.1, new PCEP error codes are defined for
WSON RWA errors. IANA is to allocate from the ""PCEP-ERROR Object
Error Types and Values" sub-registry
(http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-error-object).
Error- Meaning Error-Value Reference
Type
---------------------------------------------------------------
TBD7 Flexi-Grid RSA Error 1: Insufficient [This.I-D]
Memory
2: RSA computation [This.I-D]
Not supported
9.7. New Error-Values for Existing Error Type (24)
As discussed in Section 4.1, two new PathErr values for the Existing
Error Type (24) are to be allocated:
Meaning Error-Value Reference
---------------------------------------------------------------
Unsupported Frequency slot
Selection Symmetry value TBD3 [This.I-D]
Unsupported Frequency Slot
Assignment value TBD4 [This.I-D]
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4003] Berger, L., "GMPLS Signaling Procedure for Egress
Control", RFC 4003, February 2005.
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[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) communication Protocol", RFC 5440, March
2009.
[RFC5511] A. Farrel, "Routing Backus-Naur Form (RBNF): A Syntax Used
to Form Encoding Rules in Various Routing Protocol
Specifications", RFC 5511, April 2009.
[RFC5088] Le Roux, JL, JP. Vasseur, Y. Ikejiri, and R. Zhang, "OSPF
Protocol Extensions for Path Computation Element (PCE)
Discovery," RFC 5088, January 2008.
[RFC5089] Le Roux, JL, JP. Vasseur, Y. Ikejiri, and R. Zhang, "IS-IS
Protocol Extensions for Path Computation Element (PCE)
Discovery," RFC 5089, January 2008.
[RFC8174] B. Leiba, "Ambiguity of Uppercase vs Lowercase in RFC 2119
Key Words", RFC 8174, May 2017.
10.2. Informative References
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, August 2006.
[RFC4657] Ash, J. and J. Le Roux, "Path Computation Element (PCE)
Communication Protocol Generic Requirements", RFC 4657,
September 2006.
[RFC5420] Farrel, A. "Encoding of Attributes for MPLS LSP
Establishment Using Resource Reservation Protocol Traffic
Engineering (RSVP-TE)", RFC 5420, February 2009.
[RFC6163] Lee, Y. and Bernstein, G. (Editors), and W. Imajuku,
"Framework for GMPLS and PCE Control of Wavelength
Switched Optical Networks", RFC 6163, March 2011.
[RFC7449] Lee, Y., et. al., "PCEP Requirements for WSON Routing and
Wavelength Assignment", RFC 7449, February 2015.
[RFC7570] Margaria, et al., "Label Switched Path (LSP) Attribute in
the Explicit Route Object (ERO)", RFC 7570, July 2015.
[RFC7579] Bernstein and Lee, "General Network Element Constraint
Encoding for GMPLS Controlled Networks", RFC 7579, June
2015.
Lee et al. Expires February 2021 [Page 17]
Internet-Draft PCEP Extension for Flexible Grid August 2020
[RFC7698] O. Gonzalez de Dios, R. Casellas, editors, "Framework and
Requirements for GMPLS-Based Control of Flexi-Grid Dense
Wavelength Division Multiplexing (DWDM) Networks", RFC
7698, November 2015.
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of
Running Code: The Implementation Status Section", BCP 205,
RFC 7942, July 2016,
[RFC8363] X. Zhang, H. Zheng, R. Casellas, O. Gonzalez de Dios, D.
Ceccarelli, "GMPLS OSPF-TE Extensions in Support of Flexi-
Grid Dense Wavelength Division Multiplexing (DWDM)
Networks", RFC8363, May 2018.
[RFC8779] Margaria, et al., "PCEP extensions for GMPLS", RFC 8779,
July 2020.
[RFC8780] Y. Lee (Ed.), and R. Casellas (Ed.), "PCEP Extension for
WSON Routing and Wavelength Assignment", RFC8780, July 2020.
[G.694.1] "Spectral grids for WDM applications: DWDM frequency
grid", ITU-T G.694.1, February 2012.
[G.872] "Architecture of optical transport networks", ITU-T G.872,
January 2017.
11. Contributors
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Authors' Addresses
Young Lee
Samsung
Email: younglee.tx@gmail.com
Haomian Zheng
Huawei Technologies
Email: zhenghaomian@huawei.com
Ramon Casellas
CTTC
Av. Carl Friedrich Gauss n7
Castelldefels, Barcelona 08860
Spain
Email: ramon.casellas@cttc.es
Ricard Vilalta
CTTC
Email: ricard.vilalta@cttc.es
Daniele Ceccarelli
Ericsson AB
Gronlandsgatan 21
Kista - Stockholm
Email: daniele.ceccarelli@ericsson.com
Francesco Lazzeri
Ericsson
Via Melen 77
Genova - Italy
Email: francesco.lazzeri@ericsson.com
Lee et al. Expires February 2021 [Page 19]
