Network Working Group Y. Lee, Ed.
Internet Draft Huawei Technologies
Intended status: Standard Track R. Casellas, Ed.
Expires: February 2017 CTTC
December 16, 2016
PCEP Extension for WSON Routing and Wavelength Assignment
draft-ietf-pce-wson-rwa-ext-06.txt
Abstract
This document provides the Path Computation Element communication
Protocol (PCEP) extensions for the support of Routing and Wavelength
Assignment (RWA) in Wavelength Switched Optical Networks (WSON).
Lightpath provisioning in WSONs requires a routing and wavelength
assignment (RWA) process. From a path computation perspective,
wavelength assignment is the process of determining which wavelength
can be used on each hop of a path and forms an additional routing
constraint to optical light path computation.
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Table of Contents
1. Terminology....................................................3
2. Requirements Language..........................................3
3. Introduction...................................................3
4. Encoding of a RWA Path Request.................................6
4.1. Wavelength Assignment (WA) Object.........................6
4.2. Wavelength Selection TLV..................................8
4.3. Wavelength Restriction Constraint TLV.....................8
4.3.1. Link Identifier Field...............................11
4.3.2. Wavelength Restriction Field........................12
4.4. Signal processing capability restrictions................13
4.4.1. Signal Processing Exclusion XRO Sub-Object..........14
4.4.2. IRO sub-object: signal processing inclusion.........15
5. Encoding of a RWA Path Reply..................................15
5.1. Error Indicator..........................................16
5.2. NO-PATH Indicator........................................17
6. Manageability Considerations..................................17
6.1. Control of Function and Policy...........................17
6.2. Information and Data Models, e.g. MIB module.............18
6.3. Liveness Detection and Monitoring........................18
6.4. Verifying Correct Operation..............................18
6.5. Requirements on Other Protocols and Functional Components18
6.6. Impact on Network Operation..............................19
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7. Security Considerations.......................................19
8. IANA Considerations...........................................19
8.1. New PCEP Object..........................................19
8.2. New PCEP TLV: Wavelength Selection TLV...................20
8.3. New PCEP TLV: Wavelength Restriction Constraint TLV......20
8.4. New PCEP TLV: Wavelength Allocation TLV..................20
8.5. New PCEP TLV: Optical Interface Class List TLV...........21
8.6. New PCEP TLV: Client Signal TLV..........................21
8.7. New No-Path Reasons......................................21
8.8. New Error-Types and Error-Values.........................22
9. Acknowledgments...............................................22
10. References...................................................22
10.1. Informative References..................................22
10.2. Normative References....................................24
11. Contributors.................................................24
Authors' Addresses...............................................25
1. Terminology
This document uses the terminology defined in [RFC4655], and
[RFC5440].
2. 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].
3. Introduction
[RFC4655] defines a 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.
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The PCE communications Protocol (PCEP) is the communication protocol
used between a PCC and a PCE, and may 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.
This document 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].
WSON refers to WDM based optical networks in which switching is
performed selectively based on the wavelength of an optical signal.
WSONs can be transparent or translucent. A transparent optical
network is made up of optical devices that can switch but not
convert from one wavelength to another, all within the optical
domain. On the other hand, translucent networks include 3R
regenerators that are sparsely placed. In this document, only
wavelength converters that require electrical signal regeneration
are considered.
A Lambda Switch Capable (LSC) Label Switched Path (LSP) may span one
or several transparent segments, which are delimited by 3R
regenerators (typically with electronic regenerator and optional
wavelength conversion). Each transparent segment or path in WSON is
referred to as an optical path. An optical path may span multiple
fiber links and the path should be assigned the same wavelength for
each link. In such case, the optical path is said to satisfy the
wavelength-continuity constraint. Figure 1 illustrates the
relationship between a LSC LSP and transparent segments (optical
paths).
+---+ +-----+ +-----+ +-----+ +-----+
| |I1 | | | | | | I2| |
| |o------| |-------[(3R) ]------| |--------o| |
| | | | | | | | | |
+---+ +-----+ +-----+ +-----+ +-----+
(X LSC) (LSC LSC) (LSC LSC) (LSC X) SwCap
<-------> <-------> <-----> <------->
<-----------------------><---------------------->
Transparent Segment Transparent Segment
<------------------------------------------------->
LSC LSP
Figure 1 Illustration of a LSC LSP and transparent segments
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Note that two optical paths within a WSON LSP do not need to operate
on the same wavelength (due to the wavelength conversion
capabilities). Two optical paths that share a common fiber link
cannot be assigned the same wavelength; Otherwise, both signals
would interfere with each other. Note that advanced additional
multiplexing techniques such as polarization based multiplexing are
not addressed in this document since the physical layer aspects are
not currently standardized. Therefore, assigning the proper
wavelength on a lightpath is an essential requirement in the optical
path computation process.
When a switching node has the ability to perform wavelength
conversion, the wavelength-continuity constraint can be relaxed, and
a LSC Label Switched Path (LSP) may use different wavelengths on
different links along its route from origin to destination. It is,
however, to be noted that wavelength converters may be limited due
to their relatively high cost, while the number of WDM channels that
can be supported in a fiber is also limited. As a WSON can be
composed of network nodes that cannot perform wavelength conversion,
nodes with limited wavelength conversion, and nodes with full
wavelength conversion abilities, wavelength assignment is an
additional routing constraint to be considered in all lightpath
computation.
For example (see Figure 1), within a translucent WSON, a LSC LSP may
be established between interfaces I1 and I2, spanning 2 transparent
segments (optical paths) where the wavelength continuity constraint
applies (i.e. the same unique wavelength must be assigned to the LSP
at each TE link of the segment). If the LSC LSP induced a Forwarding
Adjacency / TE link, the switching capabilities of the TE link would
be (X X) where X refers to the switching capability of I1 and I2.
For example, X can be PSC, TDM, etc.
This document aligns with GMPLS extensions for PCEP [PCEP-GMPLS] for
generic property such as label, label-set and label assignment
noting that wavelength is a type of label. Wavelength restrictions
and constraints are also formulated in terms of labels per
[RFC7579].
The optical modulation properties, which are also referred to as
signal compatibility, are already considered in signaling in
[RFC7581] and [RFC7688]. In order to improve the signal quality and
limit some optical effects several advanced modulation processing
are used. Those modulation properties contribute not only to optical
signal quality checks but also constrain the selection of sender and
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receiver, as they should have matching signal processing
capabilities. This document includes signal compatibility
constraints as part of RWA path computation. That is, the signal
processing capabilities (e.g., modulation and FEC) by the means of
optical interface class (OIC) must be compatible between the sender
and the receiver of the optical path across all optical elements.
This document, however, does not address optical impairments as part
of RWA path computation. See [RFC6566] for more information on
optical impairments and GMPLS.
4. Encoding of a RWA Path Request
Figure 2 shows one typical PCE based implementation, which is
referred to as the Combined Process (R&WA). With this architecture,
the two processes of routing and wavelength assignment are accessed
via a single PCE. This architecture is the base architecture from
which the requirements have been specified in [RFC7449] and the PCEP
extensions that are going to be specified in this document based on
this architecture.
+----------------------------+
+-----+ | +-------+ +--+ |
| | | |Routing| |WA| |
| PCC |<----->| +-------+ +--+ |
| | | |
+-----+ | PCE |
+----------------------------+
Figure 2 Combined Process (R&WA) architecture
4.1. Wavelength Assignment (WA) Object
Wavelength 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. in the
sense that the allocated labels MAY appear after an interface route
subobject.
(b) By means of a Label Set where the PCE provides a range of
potential labels to allocate by each node along the path.
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Option (b) allows distributed label allocation (performed during
signaling) to complete wavelength assignment.
Additionally, given a range of potential labels to allocate, the
request SHOULD convey the heuristic / mechanism to the allocation.
The format of a PCReq message after incorporating the WA object is
as follows:
<PCReq Message> ::= <Common Header>
[<svec-list>]
<request-list>
Where:
<request-list>::=<request>[<request-list>]
<request>::= <RP>
<ENDPOINTS>
<WA>
[other optional objects...]
If the WA object is present in the request, it MUST be encoded after
the ENDPOINTS object.
The format of the Wavelength Assignment (WA) 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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Wavelength Selection TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Wavelength Restriction Constraint TLV |
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Optional TLVs //
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| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3 WA Object
o Reserved (16 bits)
o Flags (16 bits)
The following new flags SHOULD be set
. M (Mode - 1 bit): M bit is used to indicate the mode of
wavelength assignment. When M bit is set to 1, this indicates
that the label assigned by the PCE must be explicit. That is,
the selected way to convey the allocated wavelength is by means
of Explicit Label Control (ELC) [RFC4003] for each hop of a
computed LSP. Otherwise, the label 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
WA. 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.
4.2. Wavelength Selection TLV
The Wavelength Selection TLV is used to indicate the wavelength
selection constraint in regard to the order of wavelength assignment
to be returned by the PCE. This TLV is only applied when M bit is
set in the WA Object specified in Section 4.1. This TLV MUST NOT be
used when the M bit is cleared.
The encoding of this TLV is specified as the Wavelength Selection
Sub-TLV in Section 4.2.2 of [RFC7689].
4.3. Wavelength Restriction Constraint TLV
For any request that contains a wavelength assignment, the requester
(PCC) MUST be able to specify a restriction on the wavelengths 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. Note
that if the LSP LSC spans different segments, the PCE MUST have
mechanisms to know the tunability restrictions of the involved
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wavelength converters / regenerators, e.g. by means of the TED
either via IGP or NMS. Even if the PCE knows the tunability of the
transmitter, the PCC MUST be able to apply additional constraints to
the request.
The format of the Wavelength Restriction Constraint TLV is as
follows:
<Wavelength Restriction Constraint> ::=
<Action> <Count> <Reserved>
(<Link Identifiers> <Wavelength Restriction>)...
Where
<Link Identifiers> ::= <Link Identifier> [<Link Identifiers>]
See Section 4.2.1. for the encoding of the Link Identifiers Field.
The Wavelength Restriction Constraint TLV type is TBD, recommended
value is TBD. This TLV MAY appear more than once to be able to
specify multiple restrictions.
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 |
| . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Wavelength Restriction Field |
// . . . . //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4 Wavelength Restriction Constraint TLV Encoding
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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.
Note that "interfaces" such as those discussed in the Interfaces MIB
[RFC2863] are assumed to be bidirectional.
o Count: The number of the link identifiers (8 bits)
Note that a PCC MAY add a Wavelength restriction that applies to all
links by setting the Count field to zero and specifying just a set
of wavelengths.
Note that all link identifiers in the same list must be of the same
type.
o Reserved: Reserved for future use (16 bits)
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 4.2.1. for Link Identifier encoding and Section
4.2.2. for the Wavelength Restriction Field encoding, respectively.
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4.3.1. Link Identifier Field
The link identifier field can be an IPv4, IPv6 or unnumbered
interface ID.
<Link Identifier> ::=
<IPV4 Address> | <IPV6 Address> | <Unnumbered IF ID>
The encoding of each case is as follows:
IPv4 prefix Entry
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 = 1 | IPv4 address (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 address (continued) | Prefix Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv6 prefix Sub-TLV
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 = 2 | IPv6 address (16 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 address (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 address (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 address (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 address (continued) | Prefix Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Unnumbered Interface ID Sub-TLV
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
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 3 | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TE Node ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.3.2. Wavelength Restriction Field
The Wavelength Restriction Field of the wavelength restriction TLV
is encoded as a Label Set field as specified in [RFC7579] section
2.6, as shown below, with base label encoded as a 32 bit LSC label,
defined in [RFC6205]. See [RFC6205] for a description of Grid, C.S,
Identifier and n, as well as [RFC7579] for the details of each
action.
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| Num Labels | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Grid | C.S | Identifier | n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Additional fields as necessary per action |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Action:
0 - Inclusive List
1 - Exclusive List
2 - Inclusive Range
3 - Exclusive Range
4 - Bitmap Set
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Num Labels is generally the number of labels. It has a specific
meaning depending on the action value. Num Labels is a 12 bit
integer.
Length is the length in bytes of the entire label set field.
See Sections 2.6.1 - 2.6.3 of [RFC7579] for details on additional
field discussion for each action.
4.4. Signal processing capability restrictions
Path computation for WSON includes the check of signal processing
capabilities, those capability MAY be provided by the IGP. Moreover,
a PCC should be able to indicate additional restrictions for those
signal compatibility, either on the endpoint or any given link.
The supported signal processing capabilities are the one described
in [RFC7446]:
. Optical Interface Class List
. Bit Rate
. Client Signal
The Bit Rate restriction is already expressed in [PCEP-GMPLS] in the
BANDWIDTH object.
In order to support the Optical Interface Class information and the
Client Signal information new TLVs are introduced as endpoint-
restriction in the END-POINTS type Generalized endpoint:
. Client Signal TLV
. Optical Interface Class List TLV
The END-POINTS type generalized endpoint is extended as follows:
<endpoint-restrictions> ::= <LABEL-REQUEST>
<Wavelength Restriction Constraint>
[<signal-compatibility-restriction>...]
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Where
signal-compatibility-restriction ::=
<Optical Interface Class List> <Client Signal>
The encoding for the Optical Interface Class List is described in
Section 4.1 of [RFC7581].
The encoding for the Client Signal Information is described in
Section 4.2 of [RFC7581].
4.4.1. Signal Processing Exclusion XRO Sub-Object
The PCC/PCE should be able to exclude particular types of signal
processing along the path in order to handle client restriction or
multi-domain path computation.
In order to support the exclusion a new XRO sub-object is defined:
the signal processing exclusion:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X| Type = X | Length | Reserved | Attribute |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-sub objects |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5 Signaling Processing XRO Sub-Object
Refer to [RFC5521] for the definition of X, Type, Length and
Attribute.
The Attribute field indicates how the exclusion sub-object is to be
interpreted. The Attribute can only be 0 (Interface) or 1 (Node).
The sub-sub objects are encoded as in RSVP signaling definition
[RFC7689].
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4.4.2. IRO sub-object: signal processing inclusion
Similar to the XRO sub-object the PCC/PCE should be able to include
particular types of signal processing along the path in order to
handle client restriction or multi-domain path computation.
This is supported by adding the sub-object "processing" defined for
ERO in [RFC7689] to the PCEP IRO object.
5. Encoding of a RWA Path Reply
This section provides the encoding of a RWA Path Reply for
wavelength allocation as discussed in Section 4. Recall that
wavelength 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 labels to allocate by each node along the path.
Option (b) allows distributed label allocation (performed during
signaling) to complete wavelength allocation.
The Wavelength Allocation TLV type is TBD, recommended value is TBD.
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 Wavelength(s) |
// . . . . //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6 Wavelength Allocation TLV Encoding
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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
type.
o Link Identifier (variable): Identifies the interface to which
assignment wavelength(s) is applied. See Section 4.2.1. for Link
Identifier encoding.
o Allocated Wavelength(s) (variable): Indicates the allocated
wavelength(s) to the link identifier. See Section 4.2.2 for encoding
details.
This TLV is encoded as an attributes TLV, per [RFC5420], which is
carried in the ERO LSP Attribute Subobjects per [RFC7570]. The type
value of the Wavelength Restriction Constraint TLV is TBD by IANA.
5.1. Error Indicator
To indicate errors associated with the RWA 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 (TDB) and subsequent error-values are defined as
follows:
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. Error-Type=TBD; Error-value=1: if a PCE receives a RWA 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 RWA request MUST be cancelled at the PCC.
. Error-Type=TBD; Error-value=2: if a PCE receives a RWA request
and the PCE is not capable of RWA 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 RWA computation MUST be
cancelled at the PCC.
5.2. NO-PATH Indicator
To communicate the reason(s) for not being able to find RWA 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.
. Bit TDB: When set, the PCE indicates no feasible route was
found that meets all the constraints (e.g., wavelength
restriction, signal compatibility, etc.) associated with RWA.
6. Manageability Considerations
Manageability of WSON Routing and Wavelength Assignment (RWA) 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:
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. The ability to send a WSON RWA 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 WSON RWA.
. A set of WSON RWA 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, e.g. MIB module
Extensions to the PCEP MIB module defined in [RFC7420] should be
defined, so as to cover the WSON RWA information introduced in this
document. A future revision of this document will list the
information that should be added to the MIB module.
6.3. 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].
6.4. 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]
6.5. Requirements on Other Protocols and Functional Components
The PCE Discovery mechanisms ([RFC5089] and [RFC5088]) may be used
to advertise WSON RWA path computation capabilities to PCCs.
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6.6. 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. 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 RWA problem represents a disclosure of network
capabilities that an operator may wish to keep private.
Consideration should be given to securing this information.
8. IANA Considerations
IANA maintains a registry of PCEP parameters. IANA has made
allocations from the sub-registries as described in the following
sections.
8.1. New PCEP Object
As described in Section 4.1, a new PCEP Object is defined to carry
wavelength 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
---------------------------------------------------------
TDB WA 1: Wavelength-Assignment [This.I-D]
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8.2. New PCEP TLV: Wavelength Selection TLV
As described in Sections 4.2, a new PCEP TLV is defined to indicate
wavelength 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
---------------------------------------------------------
TBD Wavelength Selection [This.I-D]
8.3. New PCEP TLV: Wavelength Restriction Constraint TLV
As described in Sections 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
(http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-tlv-type-
indicators).
Value Description Reference
---------------------------------------------------------
TBD Wavelength Restriction [This.I-D]
Constraint
8.4. New PCEP TLV: Wavelength Allocation TLV
As described in Section 5, a new PCEP TLV is defined to indicate the
allocation of wavelength(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
---------------------------------------------------------
TBD Wavelength Allocation [This.I-D]
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8.5. New PCEP TLV: Optical Interface Class List TLV
As described in Section 4.3, a new PCEP TLV is defined to indicate
the optical interface class list. 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
---------------------------------------------------------
TBD Optical Interface [This.I-D]
Class List
8.6. New PCEP TLV: Client Signal TLV
As described in Section 4.3, a new PCEP TLV is defined to indicate
the client signal information. 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
---------------------------------------------------------
TBD Client Signal Information [This.I-D]
8.7. New No-Path Reasons
As described in Section 5.2., 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 RWA constraints (e.g., wavelength
restriction, signal compatibility, etc.) associated with a RWA 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).
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Bit Description Reference
-----------------------------------------------------
TBD No RWA constraints met [This.I-D]
8.8. 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
---------------------------------------------------------------
TDB WSON RWA Error 1: Insufficient [This.I-D]
Memory
2: RWA computation {This.I-D]
Not supported
9. Acknowledgments
The authors would like to thank Adrian Farrel for many helpful
comments that greatly improved the contents of this draft.
This document was prepared using 2-Word-v2.0.template.dot.
10. References
10.1. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group
MIB", RFC 2863, June 2000.
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[RFC4003] Berger, L., "GMPLS Signaling Procedure for Egress Control",
RFC 4003, February 2005.
[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.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) communication Protocol", RFC 5440, March
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.
[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.
[RFC6566] Y. Lee, G. Bernstein, D. Li, G. Martinelli, "A Framework
for the Control of Wavelength Switched Optical Networks
(WSON) with Impairments", RFC 6566, March 2012.
[RFC7420] Koushik, A., E. Stephan, Q. Zhao, D. King, and J.
Hardwick, "Path Computation Element Communication Protocol
(PCEP) Management Information Base (MIB) Module", RFC
7420, December 2014.
[RFC7446] Y. Lee, G. Bernstein. (Editors), "Routing and Wavelength
Assignment Information Model for Wavelength Switched
Optical Networks", RFC 7446, February 2015.
[RFC7449] Lee, Y., et. al., "PCEP Requirements for WSON Routing and
Wavelength Assignment", RFC 7449, February 2015.
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10.2. Normative References
[PCEP-GMPLS] Margaria, et al., "PCEP extensions for GMPLS", draft-
ietf-pce-gmpls-pcep-extensions, work in progress.
[RFC5420] Farrel, A. "Encoding of Attributes for MPLS LSP
Establishment Using Resource Reservation Protocol Traffic
Engineering (RSVP-TE)", RFC5420, February 2009.
[RFC5521] Oki, E, T. Takeda, and A. Farrel, "Extensions to the Path
Computation Element Communication Protocol (PCEP) for
Route Exclusions", RFC 5521, April 2009.
[RFC6205] Tomohiro, O. and D. Li, "Generalized Labels for Lambda-
Switching Capable Label Switching Routers", RFC 6205,
January, 2011.
[RFC7570] Margaria, et al., "Label Switched Path (LSP) Attribute in
the Explicit Route Object (ERO)", RFC 7570, July 2015.
[RFC7689] Bernstein et al, "Signaling Extensions for Wavelength
Switched Optical Networks", RFC 7689, November 2015.
[RFC7688] Y. Lee, and G. Bernstein, "OSPF Enhancement for Signal and
Network Element Compatibility for Wavelength Switched
Optical Networks", RFC 7688, November 2015.
[RFC7581] Bernstein and Lee, "Routing and Wavelength Assignment
Information Encoding for Wavelength Switched Optical
Networks", RFC7581, June 2015.
[RFC7579] Bernstein and Lee, "General Network Element Constraint
Encoding for GMPLS Controlled Networks", RFC 7579, June
2015.
11. Contributors
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Authors' Addresses
Young Lee, Editor
Huawei Technologies
1700 Alma Drive, Suite 100
Plano, TX 75075, USA
Phone: (972) 509-5599 (x2240)
Email: leeyoung@huawei.com
Ramon Casellas, Editor
CTTC PMT Ed B4 Av. Carl Friedrich Gauss 7
08860 Castelldefels (Barcelona)
Spain
Phone: (34) 936452916
Email: ramon.casellas@cttc.es
Fatai Zhang
Huawei Technologies
Email: zhangfatai@huawei.com
Cyril Margaria
Nokia Siemens Networks
St Martin Strasse 76
Munich, 81541
Germany
Phone: +49 89 5159 16934
Email: cyril.margaria@nsn.com
Oscar Gonzalez de Dios
Telefonica Investigacion y Desarrollo
C/ Emilio Vargas 6
Madrid, 28043
Spain
Phone: +34 91 3374013
Email: ogondio@tid.es
Greg Bernstein
Grotto Networking
Fremont, CA, USA
Phone: (510) 573-2237
Email: gregb@grotto-networking.com
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