Path Computation Element (PCE) Protocol Extensions for Stateful PCE Usage in GMPLS-controlled Networks
draft-ietf-pce-pcep-stateful-pce-gmpls-13
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 9504.
Expired & archived
|
|
|---|---|---|---|
| Authors | Young Lee , Haomian Zheng , Oscar Gonzalez de Dios , Victor Lopez , Zafar Ali | ||
| Last updated | 2020-10-25 (Latest revision 2020-04-23) | ||
| Replaces | draft-zhang-pce-pcep-stateful-pce-gmpls, draft-ietf-pce-remote-initiated-gmpls-lsp | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
| Document shepherd | (None) | ||
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| Consensus boilerplate | Unknown | ||
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| Send notices to | (None) |
draft-ietf-pce-pcep-stateful-pce-gmpls-13
PCE Working Group Y. Lee (Editor)
Internet-Draft Samsung
Intended status: Standards Track H. Zheng (Editor)
Expires: October 24, 2020 Huawei
O. G. de Dios
V. Lopez
Telefonica
Z. Ali
Cisco Systems
April 24, 2020
Path Computation Element (PCE) Protocol Extensions for Stateful PCE
Usage in GMPLS-controlled Networks
draft-ietf-pce-pcep-stateful-pce-gmpls-13
Abstract
The Path Computation Element (PCE) facilitates Traffic Engineering
(TE) based path calculation in large, multi-domain, multi-region, or
multi-layer networks. The PCE communication Protocol (PCEP) has been
extended to support stateful PCE functions where the PCE retains
information about the paths already present in the network, but
those extensions are technology-agnostic. This memo provides
extensions required for PCEP so as to enable the usage of a stateful
PCE capability in GMPLS-controlled networks.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with
the provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
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at any time. It is inappropriate to use Internet-Drafts as
reference material or to cite them other than as "work in progress."
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This Internet-Draft will expire on October 24, 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
Table of Contents .............................................. 2
1. Introduction ................................................ 3
2. Conventions used in this document............................ 4
3. General Context of Stateful PCE and PCEP for GMPLS .......... 4
4. Main Requirements ........................................... 5
5. Stateful PCEP Extensions for GMPLS Networks ................. 6
5.1. Capability Advertisement for Stateful PCEP in GMPLS .... 6
5.2. LSP Synchronization in GMPLS-controlled Networks ....... 7
5.3. LSP Delegation and Cleanup ............................. 8
5.4. LSP Operations in Stateful PCEP for GMPLS-controlled
Networks .................................................... 8
5.4.1. LSP Update in GMPLS-controlled Networks ........... 8
5.4.2. LSP Initiation in GMPLS-controlled Networks ....... 9
6. Modification of Existing PCEP Messages and Procedures ....... 9
6.1. Modification for LSP Re-optimization ................... 9
6.2. Modification for Route Exclusion ...................... 10
6.2.1. Modification for SRP Object to indicate Bi-directional
LSP ..................................................... 11
7. PCEP Object Extensions ..................................... 11
7.1. Generalized Endpoint .................................. 11
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7.2. GENERALIZED-BANDWIDTH object .......................... 12
7.3. The LSP Protection Information ........................ 12
7.4. ERO Extension ......................................... 12
7.4.1. ERO with explicit label control .................. 13
7.4.2. ERO with Path Keys ............................... 13
7.5. Switch Layer Object ................................... 14
8. IANA Considerations ........................................ 14
8.1. New PCEP Error Codes .................................. 14
8.2. New Subobject for the Exclude Route Object ............ 14
8.3. New "B" Flag in the SRP Object ........................ 15
9. Manageability Considerations ............................... 15
9.1. Requirements on Other Protocols and Functional Components15
10. Security Considerations ................................... 15
11. Acknowledgement ........................................... 16
12. References ................................................ 16
12.1. Normative References ................................. 16
12.2. Informative References ............................... 16
13. Contributors' Address ..................................... 18
Authors' Addresses ............................................ 19
1. Introduction
[RFC4655] presents the architecture of a Path Computation Element
(PCE)-based model for computing Multiprotocol Label Switching (MPLS)
and Generalized MPLS (GMPLS) Traffic Engineering Label Switched
Paths (TE LSPs). To perform such a constrained computation, a PCE
stores the network topology (i.e., TE links and nodes) and resource
information (i.e., TE attributes) in its TE Database (TED). Such a
PCE is usually referred as a stateless PCE. To request path
computation services to a PCE, [RFC5440] defines the PCE
communication Protocol (PCEP) for interaction between a Path
Computation Client (PCC) and a PCE, or between two PCEs. PCEP as
specified in [RFC5440] mainly focuses on MPLS networks and the PCEP
extensions needed for GMPLS-controlled networks are provided in
[PCEP-GMPLS].
Stateful PCEs are shown to be helpful in many application scenarios,
in both MPLS and GMPLS networks, as illustrated in [RFC8051].
Further discussion of concept of a stateful PCE can be found in
[RFC7399]. In order for these applications to able to exploit the
capability of stateful PCEs, extensions to PCEP are required.
[RFC8051] describes how a stateful PCE can be applicable to solve
various problems for MPLS-TE and GMPLS networks and the benefits it
brings to such deployments.
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[RFC8231] provides the fundamental extensions needed for stateful
PCE to support general functionality. Furthermore, [RFC8281]
describes the setup and teardown of PCE-initiated LSPs under the
active stateful PCE model, without the need for local configuration
on the PCC. However, both the documents left out the specification
for technology-specific objects/TLVs, and does not cover the GMPLS
networks (e.g., WSON, OTN, SONET/ SDH, etc. technologies). This
document focuses on the extensions that are necessary in order for
the deployment of stateful PCEs and the requirements for remote-
initiated LSPs in GMPLS-controlled networks. Section 3 provides
General context of Stateful PCE and PCEP for GMPLS are provided in
Section 3, and PCE initiation requirement for GMPLS is provided in
section 4. Protocol extensions is included in section 5, as a
solution to address such requirements.
2. Conventions used in this document
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. General Context of Stateful PCE and PCEP for GMPLS
This section is built on the basis of Stateful PCE in [RFC8231] and
PCEP for GMPLS in [PCEP-GMPLS].
The operation for Stateful PCE on LSPs can be divided into two types,
active stateful PCE and passive stateful PCE.
For active stateful PCE, PCUpd message is sent from PCE to PCC to
update the LSP state for the LSP delegated to PCE. Any changes to
the delegated LSPs generate a PCRpt message by the PCC to PCE to
convey the changes of the LSP. Any modifications to the Objects/TLVs
that are identified in this document to support GMPLS technology-
specific attributes will be carried in the PCRpt and PCUpd messages.
For passive stateful PCEs, PCReq/PCRep messages are used to convey
path computation instructions. GMPLS-technology specific Objects
and TLVs are defined in [PCEP-GMPLS], so this document just points
at that work and only adds the stateful PCE aspects where applicable.
Passive Stateful PCE makes use of PCRpt messages when reporting LSP
State changes sent by PCC to PCEs. Any modifications to the
Objects/TLVs that are identified in this document to support GMPLS
technology-specific attributes will be carried in the PCRpt message.
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[PCEP-GMPLS] defines GMPLS-technology specific Objects/TLVs and this
document makes use of these Objects/TLVs without modifications where
applicable. Some of these Objects/TLVs may require modifications to
incorporate stateful PCE where applicable. The remote-initiated LSP
would follow the principle specified in [RFC8281], and GMPLS-
specific extensions are also included in this document.
4. Main Requirements
This section notes the main functional requirements for PCEP
extensions to support stateful PCE for use in GMPLS-controlled
networks, based on the description in [RFC8051]. Many
requirements are common across a variety of network types (e.g.,
MPLS-TE networks and GMPLS networks) and the protocol extensions to
meet the requirements are already described in [RFC8231]. This
document does not repeat the description of those protocol
extensions. This document presents protocol extensions for a set of
requirements which are specific to the use of a stateful PCE in a
GMPLS-controlled network.
The requirements for GMPLS-specific stateful PCE are as follows:
o Advertisement of the stateful PCE capability. This generic
requirement is covered in Section 5.4 of [RFC8231], and the
GMPLS capability TLV as per [PCEP-GMPLS] MUST be advertised as
well. This document assumes that STATEFUL-PCE-CAPABILITY TLV
specified in [RFC8231] can be used for GMPLS Stateful PCE
capability advertisement and there is no further extensions.
o Active LSP update is covered in Section 6.2 of [RFC8231].
Section 5.1 of this document provides extension for its
application in GMPLS-controlled networks.
o LSP state synchronization and LSP state report. This is a
generic requirement already covered in Section 5.6. of
[RFC8231]. However, there are further extensions required
specifically for GMPLS-controlled networks and discussed in
Section 5.2.
o LSP delegation is already covered in Section 5.7 of [RFC8231].
The delegation procedure is reused in this document without any
further extensions. Statement can be found in section 5.3 in
this document.
o All the PCEP messages need to be capable to indicate GMPLS-
specific switching capabilities per TE link basis. GMPLS LSP
creation requires knowledge of LSP switching capability (e.g.,
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TDM, L2SC, OTN-TDM, LSC, etc.) to be used according to [RFC3471],
[RFC3473].
o In order to create/modify/delete GMPLS LSPs, the PCEP messages
also need to indicate knowledge of the encoding type (e.g., WSON,
Ethernet, SONET/ SDH, OTN, etc.) to be used by the LSP according
to [RFC3471], [RFC3473].
o GMPLS LSP creation/modification/deletion requires information of
the generalized payload (G-PID) to be carried by the LSP per
[RFC3471], [RFC3473]. It also requires the specification of data
flow specific traffic parameters (also known as Tspec), which
are technology specific. Such information would be needed for
PCEP message.
o GMPLS extends the addressing to include unnumbered interface
identifiers, as defined in [RFC3477].
o In some technologies path calculation is tightly coupled with
label selection along the route. For example, path calculation
in a WDM network may include lambda continuity and/or lambda
feasibility constraints and hence a path computed by the PCE is
associated with a specific lambda (label). Hence, in such
networks, the label information needs to be provided to a PCC in
order for a PCE to initiate GMPLS LSPs under the active stateful
PCE model, i.e., explicit label control may be required.
o Stateful PCEP message also need to indicate the protection
context information for the LSP specified by GMPLS, as defined
in [RFC4872], [RFC4873].
5. Stateful PCEP Extensions for GMPLS Networks
5.1. Capability Advertisement for Stateful PCEP in GMPLS
Capability Advertisement has been specified in [RFC8231], and can be
achieved by using the "STATEFUL-PCE-CAPABILITY TLV". GMPLS-
CAPABILITY TLV has been defined in [PCEP-GMPLS], and would be useful
for stateful PCEP in GMPLS network as well.
Besides the above, this document does not have additional extension
regarding the capability advertisement.
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5.2. LSP Synchronization in GMPLS-controlled Networks
PCCs need to report the attributes of LSPs to the PCE to enable
stateful operation of a GMPLS network. This process is known as
LSP state synchronization. The LSP attributes include bandwidth,
associated route, and protection information etc., are stored by the
PCE in the LSP database (LSP-DB). Note that, as described in
[RFC8231], the LSP state synchronization covers both the bulk
reporting of LSPs at initialization as well the reporting of new or
modified LSP during normal operation. Incremental LSP-DB
synchronization may be desired in a GMPLS-controlled network and it
is specified in [RFC8232].
[RFC8231] describes mechanisms for LSP synchronization using the
Path Computation State Report (PCRpt) message, but does not cover
reporting of technology-specific attributes. As stated in [RFC8231],
the <path> construct is further composed of a compulsory Explicit
Route Object (ERO) and a compulsory attribute-list and an optional
Record Route Object (RRO). In order to report LSP states in GMPLS
networks, this specification allows the use within a PCRpt message
both of technology- and GMPLS-specific attribute objects and TLVs
defined in [PCEP-GMPLS] as follows:
o Include Route Object (IRO)/ Exclude Route Object (XRO)
Extensions to support the inclusion/exclusion of labels and
label sub-objects for GMPLS. (See Section 2.6 and 2.7 in [PCEP-
GMPLS])
o END-POINTS (Generalized END-POINTS Object Type. See Section 2.5
in [PCEP-GMPLS])
o BANDWIDTH (Generalized BANDWIDTH Object Type. See Section 2.3
in [PCEP-GMPLS])
o LSPA (PROTECTION ATTRIBUTE TLV, See Section 2.8 in [PCEP-GMPLS].
The END-POINTS object SHOULD be carried within the attribute-list to
specify the endpoints pertaining to the reported LSP. The XRO object
MAY be carried to specify the network resources that the reported
LSP avoids and a PCE SHOULD consider avoid these network resources
during the process of re-optimizing after this LSP is delegated to
the PCE. To be more specific, the <attribute-list> is updated as
follows using the notations of [RFC5511]:
<attribute-list> ::= [<END-POINTS>]
[<LSPA>]
[<BANDWIDTH>]
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[<metric-list>]
[<IRO>]
[<XRO>]
<metric-list>::= <METRIC>[<metric-list>]
If the LSP being reported protects another LSP, the PROTECTION-
ATTRIBUTE TLV [PCEP-GMPLS] MUST be included in the LSPA object to
describe its attributes and restrictions. Moreover, if the status of
the protecting LSP changes from non-operational to operational, the
PCC SHOULD synchronize the state change of the LSPs to the stateful
PCE using a PCRpt message. This use case arises, for example, when
the protecting LSP becomes operational due to the failure of the
primary LSP.
5.3. LSP Delegation and Cleanup
LSP delegation and cleanup procedure specified in [RFC8231] are
equally applicable to GMPLS LSPs and this document does not modify
the associated usage.
5.4. LSP Operations in Stateful PCEP for GMPLS-controlled Networks
Both passive and active stateful PCE mechanism in [RFC8231] are
applicable in GMPLS-controlled networks.
5.4.1. LSP Update in GMPLS-controlled Networks
[RFC8231] defines the Path Computation LSP Update Request (PCUpd)
message to enable to update the attributes of an LSP. However,
[RFC8231] does not define technology-specific parameters.
A key element of the PCUpd message is the attribute-list construct
defined in [RFC5440] and extended by many other PCEP specifications.
For GMPLS purposes we note that the BANDWIDTH object used in the
attribute-list is defined in [PCEP-GMPLS]. Furthermore, additional
TLVs are defined for the LSPA object in [PCEP-GMPLS] and MAY be
included to indicate technology-specific attributes. There are other
technology-specific attributes that need to be conveyed in the
<intended-attribute-list> of the <path> construct in the PCUpd
message. Note that these path details in the PCUpd message are the
same as the <attribute-list> of the PCRep message. See Section 5.3
for the details.
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5.4.2. LSP Initiation in GMPLS-controlled Networks
PCInitiate message defined in [RFC8281] needs to be extended in
GMPLS network to support the LSP initiation. The extension includes
the following objects:
6. Modification of Existing PCEP Messages and Procedures
[Editor Notes]: the whole section would need re-working, the
objective is to indicate the RBNF model for the PCEP extension,
especially where new objects and TLVs are specified.
One of the advantages mentioned in [RFC8051] is that the stateful
nature of a PCE simplifies the information conveyed in PCEP messages,
notably between PCC and PCE, since it is possible to refer to PCE
managed state for active LSPs. To be more specific, with a stateful
PCE, it is possible to refer to an LSP with a unique identifier in
the scope of the PCC-PCE session and thus use such identifier to
refer to that LSP. Note this is also applicable to packet networks.
6.1. Modification for LSP Re-optimization
The Request Parameters (RP) object on a Path Computation Request
(PCReq) message carries the R bit. When set, this indicates that
the PCC is requesting re-optimization of an existing LSP. Upon
receiving such a PCReq, a stateful PCE SHOULD perform the re-
optimization in the following cases:
o The existing bandwidth and route information of the LSP to be
re-optimized is provided in the PCReq message using the
BANDWIDTH object and the ERO.
o The existing bandwidth and route information is not supplied
in the PCReq message, but can be found in the PCE's LSP-DB.
In this case, the LSP MUST be identified using an LSP
identifier carried in the PCReq message, and that fact
requires that the LSP identifier was previously supplied
either by the PCC in a PCRpt message or by the PCE in a PCRep
message. [RFC8231] defines how this is achieved using a
combination of the per-node LSP identifier (PLSP-ID) and the
PCC's address.
If no LSP state information is available to carry out re-
optimization, the stateful PCE should report the error "LSP state
information unavailable for the LSP re-optimization" (Error Type =
TBD1, Error value= TBD2).
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6.2. Modification for Route Exclusion
[RFC5521] defines a mechanism for a PCC to request or demand that
specific nodes, links, or other network resources are excluded from
paths computed by a PCE. A PCC may wish to request the computation
of a path that avoids all link and nodes traversed by some other LSP.
To this end this document defines a new sub-object for use with
route exclusion defined in [RFC5521]. The LSP exclusion sub-object
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X|Type (TBD3) | Length | Attributes | Flag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Symbolic Path Name //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
X bit and Attribute fields are defined in [RFC5521].
Type: Subobject Type for an LSP exclusion sub-object. Value of
TBD3. To be assigned by IANA.
Length: The Length contains the total length of the subobject in
bytes, including the Type and Length fields.
Flags: This field may be used to further specify the exclusion
constraint with regard to the LSP. Currently, no values are
defined.
Symbolic Path Name: This is the identifier given to an LSP and is
unique in the context of the PCC address as defined in [RFC8231].
Reserved: MUST be transmitted as zero and SHOULD be ignored on
receipt.
This sub-object is OPTIONAL in the exclude route object (XRO) and
can be present multiple times. When a stateful PCE receives a PCReq
message carrying this sub-object, it SHOULD search for the
identified LSP in its LSP-DB and then exclude from the new path
computation all resources used by the identified LSP. If the
stateful PCE cannot recognize one or more of the received LSP
identifiers, it should send an error message PCErr reporting "The
LSP state information for route exclusion purpose cannot be found"
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(Error-type = TBD1, Error-value = TBD4). Optionally, it may provide
with the unrecognized identifier information to the requesting PCC
using the error reporting techniques described in [RFC5440].
6.2.1. Modification for SRP Object to indicate Bi-directional LSP
The format of the SRP object is defined in [RFC8231]. The object is
used in PCUpd and PCInitiate messages for GMPLS.
This document defines a new flag to be carried in the Flags field of
the SRP object. This flag indicates a bidirectional co-routed LSP
setup operation initiated by the PCE as follows:
o B (Bidirectional LSP -- 1 bit): If set to 0, it indicates a
request to create a uni-directional LSP. If set to 1, it
indicates a request to create a bidirectional co-routed LSP.
The bit position is TBD5 as assigned by IANA (see Section 5.3)
7. PCEP Object Extensions
7.1. Generalized Endpoint
This document does not modify the usage of END-POINTS object for PCE
initiated LSPs as specified in [RFC8281] . It augments the usage as
specified below.
END-POINTS object has been extended by [PCEP-GMPLS] to include a new
object type called "Generalized Endpoint". PCInitiate message sent
by a PCE to a PCC to trigger a GMPLS LSP instantiation MUST include
the END-POINTS with Generalized Endpoint object type. Furthermore,
the END-POINTS object MUST contain "label request" TLV. The label
request TLV is used to specify the switching type, encoding type and
G-PID of the LSP being instantiated by the PCE.
If the END-POINTS Object of type Generalized Endpoint is missing the
label request TLV, the PCC MUST send a PCErr message with Error-
type=6 (Mandatory Object missing) and Error-value= TBA (label
request TLV missing).
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If the PCC does not support the END-POINTS Object of type
Generalized Endpoint, the PCC MUST send a PCErr message with Error-
type = 3(Unknown Object), Error-value = 2(unknown object type).
The unnumbered endpoint TLV can be used to specify unnumbered
endpoint addresses for the LSP being instantiated by the PCE. The
END-POINTS MAY contain other TLVs defined in [PCEP-GMPLS].
7.2. GENERALIZED-BANDWIDTH object
LSP initiate message defined in [RFC8281] can optionally include the
BANDWIDTH object. However, the following possibilities cannot be
represented in the BANDWIDTH object:
o Asymmetric bandwidth (different bandwidth in forward and
reverse direction), as described in [RFC6387].
o Technology specific GMPLS parameters (e.g., Tspec for
SDH/SONET, G.709, ATM, MEF, etc.) are not supported.
GENERALIZED-BANDWIDTH object has been defined in [PCEP-GMPLS] to
address the above-mentioned limitation of the BANDWIDTH object.
This document specifies the use of GENERALIZED-BANDWIDTH object in
PCInitiate message. Specifically, GENERALIZED-BANDWIDTH object MAY
be included in the PCInitiate message. The GENERALIZED-BANDWIDTH
object in PCInitiate message is used to specify technology specific
Tspec and asymmetrical bandwidth values for the LSP being
instantiated by the PCE.
7.3. The LSP Protection Information
LSPA in the PCEP message can be used to specify protection
attributes of the LSP being instantiated by the stateful PCE.
7.4. ERO Extension
GMPLS network does not have special requirement on modifying the
usage of ERO object for stateful PCEP in [RFC8231] and PCE initiated
LSPs as specified in [RFC8281]. It augments the usage as specified
in the following sections.
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7.4.1. ERO with explicit label control
As mentioned earlier, there are technologies and scenarios where
active stateful PCE requires explicit label control in order to
instantiate an LSP.
Explicit label control (ELC) is a procedure supported by RSVP-TE,
where the outgoing label(s) is (are) encoded in the ERO. [PCEP-GMPLS]
extends the ERO object of PCEP to include explicit label control.
The ELC procedure enables the PCE to provide such label(s) directly
in the path ERO.
The extended ERO object in PCInitiate message can be used to specify
label along with ERO to PCC for the LSP being instantiated by the
active stateful PCE.
7.4.2. ERO with Path Keys
There are many scenarios in packet and optical networks where the
route information of an LSP may not be provided to the PCC for
confidentiality reasons. A multi-domain or multi-layer network is
an example of such networks. Similarly, a GMPLS User- Network
Interface (UNI) [RFC4208] is also an example of such networks.
In such scenarios, ERO containing the entire route cannot be
provided to PCC (by PCE). Instead, PCE provides an ERO with Path
Keys to the PCC. For example, in the case UNI interface between the
router and the optical nodes, the ERO in the LSP Initiate Message
may be constructed as follows:
o The first hop is a strict hop that provides the egress
interface information at PCC. This interface information is
used to get to a network node that can extend the rest of the
ERO. (Please note that in the cases where the network node is
not directly connected with the PCC, this part of ERO may
consist of multiple hops and may be loose).
o The following(s) hop in the ERO may provide the network node
with the path key [RFC5520] that can be resolved to get the
contents of the route towards the destination.
o There may be further hops but these hops may also be encoded
with the path keys (if needed).
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This document does not change encoding or processing roles for the
path keys, which are defined in [RFC5520].
7.5. Switch Layer Object
[RFC8282] specifies the SWITCH-LAYER object which defines and
specifies the switching layer (or layers) in which a path MUST or
MUST NOT be established. A switching layer is expressed as a
switching type and encoding type. [PCEP-GMPLS], which defines the
GMPLS extensions for PCEP, suggests using the SWITCH-LAYER object.
Thus, SWITCH-LAYER object can be used in the PCInitiate message to
specify the switching layer (or layers) of the LSP being remotely
initiated.
8. IANA Considerations
8.1. New PCEP Error Codes
IANA is requested to make the following allocation in the "PCEP-
ERROR Object Error Types and Values" registry.
Error Type Meaning Reference
TBD1 LSP state information missing [This.I-D]
Error-value TBD2: LSP state information unavailable [This.I-D]
for the LSP re-optimization
Error-value TBD4: LSP state information for route
exclusion purpose cannot be found [This.I-D]
This document defines the following new Error-Value:
Error-Type Error-Value Reference
6 Error-value TBD5: Label Request TLV
missing [This.I-D]
8.2. New Subobject for the Exclude Route Object
IANA maintains the "PCEP Parameters" registry containing a
subregistry called "PCEP Objects". This registry has a subregistry
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for the XRO (Exclude Route Object) listing the sub-objects that can
be carried in the XRO. IANA is requested to assign a further sub-
object that can be carried in the XRO as follows:
Value Description Reference
----------+------------------------------+-------------
TBD3 LSP identifier sub-object [This.I-D]
8.3. New "B" Flag in the SRP Object
IANA maintains a subregistry, named the "SRP Object Flag Field",
within the "Path Computation Element Protocol (PCEP) Numbers"
registry, to manage the Flag field of the SRP object.
IANA is requested to make an assignment from this registry as
follows:
Bit Description Reference
--- ---------------------------- ----------
TDB5 Bi-directional co-routed LSP [This.I-D]
9. Manageability Considerations
The description and functionality specifications presented related
to stateful PCEs should also comply with the manageability
specifications covered in Section 8 of [RFC4655]. Furthermore, a
further list of manageability issues presented in [RFC8231] should
also be considered.
Additional considerations are presented in the next section.
9.1. Requirements on Other Protocols and Functional Components
When the detailed route information is included for LSP state
synchronization (either at the initial stage or during LSP state
report process), this requires the ingress node of an LSP carry the
RRO object in order to enable the collection of such information.
10. Security Considerations
This draft provides additional extensions to PCEP so as to
facilitate stateful PCE usage in GMPLS-controlled networks, on top
of [RFC8231]. The PCEP extensions to support GMPLS-controlled
networks should be considered under the same security as for MPLS
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networks, as noted in [RFC7025]. Therefore, the security
considerations elaborated in [RFC5440] still apply to this draft.
Furthermore, [RFC8231] provides a detailed analysis of the
additional security issues incurred due to the new extensions and
possible solutions needed to support for the new stateful PCE
capabilities and they apply to this document as well.
11. Acknowledgement
We would like to thank Adrian Farrel, Cyril Margaria, George Swallow
and Jan Medved for the useful comments and discussions.
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to indicate
requirements levels", RFC 2119, March 1997.
[RFC5440] Vasseur, J.-P., and Le Roux, JL., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
March 2009.
[RFC5521] Oki, E., Takeda, T., and A. Farrel, "Extensions to the
Path Computation Element Communication Protocol (PCEP) for
Route Exclusions", RFC 5521, April 2009.
[RFC8174] B. Leiba, "Ambiguity of Uppercase vs Lowercase in RFC 2119
Key Words", RFC 8174, May 2017.
[RFC8231] Crabbe, E., Medved, J., Varga, R., Minei, I., "Path
Computation Element Communication Protocol (PCEP)
Extensions for Stateful PCE", RFC 8231, September 2017.
[RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for PCE-Initiated LSP Setup in a Stateful PCE
Model", RFC 8281, December 2017.
[PCEP-GMPLS] Margaria, C., Gonzalez de Dios, O., Zhang, F., "PCEP
extensions for GMPLS", draft-ietf-pce-gmpls-pcep-
extensions, work in progress.
12.2. Informative References
[RFC5511] A. Farrel, "Routing Backus-Naur Form (RBNF): A Syntax Used
to Form Encoding Rules in Various Routing Protocol
Specifications", RFC 5511, April 2009.
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[RFC8051] Zhang, X., Minei, I., et al, "Applicability of Stateful
Path Computation Element (PCE) ", RFC 8051, January 2017.
[RFC8232] Crabbe, E., Minei, I., Medved, J., Varga, R., Zhang, X.,
and D. Dhody, "Optimizations of Label Switched Path State
Synchronization Procedures for a Stateful PCE", RFC 8232,
September 2017.
[RFC8282] Oki, E., Takeda, T., Farrel, A., and F. Zhang, "Extensions
to the Path Computation Element communication Protocol
(PCEP) for Inter-Layer MPLS and GMPLS Traffic Engineering",
RFC 8282, December 2017.
[RFC3471] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description", RFC
3471, January 2003.
[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol
Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
January 2003.
[RFC3477] Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links
in Resource ReSerVation Protocol - Traffic Engineering
(RSVP-TE)", RFC 3477, January 2003.
[RFC4208] Swallow, G., Drake, J., Ishimatsu, H., and Y. Rekhter,
"Generalized Multiprotocol Label Switching (GMPLS) User
Network Interface (UNI): Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Support for the Overlay
Model", RFC 4208, October 2005.
[RFC4655] Farrel, A., Vasseur, J.-P., and Ash, J., "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
August 2006.
[RFC4872] Lang, J., Ed., Rekhter, Y., Ed., and D. Papadimitriou,
Ed., "RSVP-TE Extensions in Support of End-to-End
Generalized Multi-Protocol Label Switching (GMPLS)
Recovery", RFC 4872, May 2007.
[RFC4873] Berger, L., Bryskin, I., Papadimitriou, D., and A. Farrel,
"GMPLS Segment Recovery", RFC 4873, May 2007.
[RFC5520] Bradford, R., Ed., Vasseur, JP., and A. Farrel,
"Preserving Topology Confidentiality in Inter-Domain Path
Computation Using a Path-Key-Based Mechanism", RFC 5520,
April 2009.
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[RFC6387] Takacs, A., Berger, L., Caviglia, D., Fedyk, D., and J.
Meuric, "GMPLS Asymmetric Bandwidth Bidirectional Label
Switched Paths (LSPs)", RFC 6387, September 2011.
[RFC7025] Otani, T., Ogaki, K., Caviglia, D., Zhang, F., and C.
Margaria, "Requirements for GMPLS Applications of PCE",
RFC 7025, September 2013,
[RFC7399] Farrel, A., King, D., "Unanswered Questions in the Path
Computation Element Architecture", RFC 7399, October 2014.
13. Contributors' Address
Xian Zhang
Huawei Technologies
Email: zhang.xian@huawei.com
Dhruv Dhody
Huawei Technology
India
Email: dhruv.ietf@gmail.com
Yi Lin
Huawei Technologies
Email: yi.lin@huawei.com
Fatai Zhang
Huawei Technologies
Email: zhangfatai@huawei.com
Ramon Casellas
CTTC
Av. Carl Friedrich Gauss n7
Castelldefels, Barcelona 08860
Spain
Email: ramon.casellas@cttc.es
Siva Sivabalan
Cisco Systems
Email: msiva@cisco.com
Clarence Filsfils
Cisco Systems
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Email: cfilsfil@cisco.com
Robert Varga
Pantheon Technologies
Email: nite@hq.sk
Authors' Addresses
Young Lee (Editor)
Samsung
Email: younglee.tx@gmail.com
Haomian Zheng (Editor)
Huawei Technologies
H1, Huawei Xiliu Beipo Village, Songshan Lake
Dongguan, Guangdong 523808
P.R.China
Email: zhenghaomian@huawei.com
Oscar Gonzalez de Dios
Telefonica
Phone: +34 913374013
Email: oscar.gonzalezdedios@telefonica.com
Victor Lopez
Telefonica
Email: victor.lopezalvarez@telefonica.com
Zafar Ali
Cisco Systems
Email: zali@cisco.com
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