PCE Working Group E. Oki
Internet-Draft University of Electro-Communications
Intended status: Standards Track T. Takeda
Expires: July 7, 2017 NTT
A. Farrel
Juniper Networks
F. Zhang
Huawei Technologies Co., Ltd.
January 3, 2017
Extensions to the Path Computation Element communication Protocol (PCEP)
for Inter-Layer MPLS and GMPLS Traffic Engineering
draft-ietf-pce-inter-layer-ext-12
Abstract
The Path Computation Element (PCE) provides path computation
functions in support of traffic engineering in Multiprotocol Label
Switching (MPLS) and Generalized MPLS (GMPLS) networks.
MPLS and GMPLS networks may be constructed from layered service
networks. It is advantageous for overall network efficiency to
provide end-to-end traffic engineering across multiple network layers
through a process called inter-layer traffic engineering. PCE is a
candidate solution for such requirements.
The PCE communication Protocol (PCEP) is designed as a communication
protocol between Path Computation Clients (PCCs) and PCEs. This
document presents PCEP extensions for inter-layer traffic
engineering.
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].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 7, 2017.
Copyright Notice
Copyright (c) 2017 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
Provisions Relating to IETF Documents
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Overview of PCE-Based Inter-Layer Path Computation . . . . . 4
3. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 4
3.1. INTER-LAYER Object . . . . . . . . . . . . . . . . . . . 4
3.2. SWITCH-LAYER Object . . . . . . . . . . . . . . . . . . . 7
3.3. REQ-ADAP-CAP Object . . . . . . . . . . . . . . . . . . . 9
3.4. New Metric Types . . . . . . . . . . . . . . . . . . . . 10
3.5. SERVER-INDICATION Object . . . . . . . . . . . . . . . . 10
4. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.1. Path Computation Request . . . . . . . . . . . . . . . . 11
4.2. Path Computation Reply . . . . . . . . . . . . . . . . . 12
4.3. Stateful PCE and PCE Initiated LSPs . . . . . . . . . . . 13
5. Updated Format of PCEP Messages . . . . . . . . . . . . . . . 13
6. Manageability Considerations . . . . . . . . . . . . . . . . 15
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
7.1. New PCEP Objects . . . . . . . . . . . . . . . . . . . . 16
7.2. New Registry for INTER-LAYER Object Flags . . . . . . . . 16
7.3. New Metric Types . . . . . . . . . . . . . . . . . . . . 17
8. Security Considerations . . . . . . . . . . . . . . . . . . . 17
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 18
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
11.1. Normative References . . . . . . . . . . . . . . . . . . 18
11.2. Informative References . . . . . . . . . . . . . . . . . 19
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Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction
The Path Computation Element (PCE) defined in [RFC4655] is an entity
that is capable of computing a network path or route based on a
network graph, and applying computational constraints. A Path
Computation Client (PCC) may make requests to a PCE for paths to be
computed, and a PCE may initiate or modify services in a network by
supplying new paths ([I-D.ietf-pce-stateful-pce],
[I-D.ietf-pce-pce-initiated-lsp]).
A network may comprise multiple layers. These layers may represent
separations of technologies (e.g., packet switch capable (PSC), time
division multiplex (TDM), lambda switch capable (LSC)) [RFC3945],
separation of data plane switching granularity levels (e.g., VC4 and
VC12) [RFC5212], or a distinction between client and server
networking roles (e.g., commercial or administrative separation of
client and server networks). In this multi-layer network, Label
Switched Paths (LSPs) in lower layers are used to carry higher-layer
LSPs. The network topology formed by lower-layer LSPs and advertised
as traffic engineering links (TE links) in the higher layer is called
a Virtual Network Topology (VNT) [RFC5212]. Discussion of other ways
that network layering can be supported such that connectivity in a
higher layer network can be provided by LSPs in a lower layer network
is provided in [RFC7926].
It is important to optimize network resource utilization globally,
i.e., taking into account all layers, rather than optimizing resource
utilization at each layer independently. This allows better network
efficiency to be achieved. This is what we call inter-layer traffic
engineering. This includes mechanisms allowing the computation of
end-to-end paths across layers (known as inter-layer path
computation), and mechanisms for control and management of the VNT by
setting up and releasing LSPs in the lower layers [RFC5212].
PCE can provide a suitable mechanism for resolving inter-layer path
computation issues. The framework for applying the PCE-based path
computation architecture to inter-layer traffic engineering is
described in [RFC5623].
The PCE communication protocol (PCEP) is designed as a communication
protocol between PCCs and PCEs and is defined in [RFC5440]. A set of
requirements for PCEP extensions to support inter-layer traffic
engineering is described in [RFC6457].
This document presents PCEP extensions for inter-layer traffic
engineering that satisfy the requirements described in [RFC6457].
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2. Overview of PCE-Based Inter-Layer Path Computation
[RFC4206] defines a way to signal a higher-layer LSP which has an
explicit route that includes hops traversed by LSPs in lower layers.
The computation of end-to-end paths across layers is called Inter-
Layer Path Computation.
A Label Switching Router (LSR) in the higher-layer might not have
information on the lower-layer topology, particularly in an overlay
or augmented model [RFC3945], and hence may not be able to compute an
end-to-end path across layers.
PCE-based inter-layer path computation consists of using one or more
PCEs to compute an end-to-end path across layers. This could be
achieved by relying on a single PCE that has topology information
about multiple layers and can directly compute an end-to-end path
across layers considering the topology of all of the layers.
Alternatively, the inter-layer path computation could be performed
using multiple cooperating PCEs where each PCE has information about
the topology of one or more layers (but not all layers) and where the
PCEs collaborate to compute an end-to-end path.
As described in [RFC5339], a hybrid node may advertise a single TE
link with multiple switching capabilities. Those TE links exist at
the layer/region boarder normally. In this case, a PCE needs to be
capable of specifying the server layer path information when the
server layer path information is required to be returned to the PCC.
[RFC5623] describes models for inter-layer path computation in more
detail. It introduces the Virtual Network Topology Manager (VNTM), a
functional element that controls the VNT, and sets out three distinct
models (and a fourth hybrid model) for inter-layer control involving
a PCE, triggered signalling, and a Network Management System (NMS).
3. Protocol Extensions
This section describes PCEP extensions for inter-layer path
computation. Four new objects are defined: the INTER-LAYER object,
the SWITCH-LAYER object, the REQ-ADAP-CAP object, and the SERVER-
INDICATION object. Also, two new metric types are defined.
3.1. INTER-LAYER Object
The INTER-LAYER object is optional and can be used in PCReq and PCRep
messages, and also in PCRpt, PCUpd, and PCInitiate messages.
In a PCReq message, the INTER-LAYER object indicates whether inter-
layer path computation is allowed, the type of path to be computed,
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and whether triggered signaling (hierarchical LSPs per [RFC4206] or
stitched LSPs per [RFC5150] depending on physical network
technologies) is allowed. When the INTER-LAYER object is absent from
a PCReq message, the receiving PCE MUST process as though inter-layer
path computation had been explicitly disallowed (I-bit set to zero -
see below).
In a PCRep message, the INTER-LAYER object indicates whether inter-
layer path computation has been performed, the type of path that has
been computed, and whether triggered signaling is used.
When a PCReq message includes more than one request, an INTER-LAYER
object is used per request. When a PCRep message includes more than
one path per request that is responded to, an INTER-LAYER object is
used per path.
The applicability of this object to PCRpt and PCUpd messages follows
as the usage of other objects on those messages as described in
[I-D.ietf-pce-stateful-pce]. The applicability of this object to the
PCInitiate message follows as the usage of other objects on those
messages as described in [I-D.ietf-pce-pce-initiated-lsp]. These
messages use the <attribute-list> as defined in [RFC5440] and
extended by further PCEP extensions, and so the <attribute-list> as
extended in Section 5 can be used to include the INTER-LAYER object
on these messages.
INTER-LAYER Object-Class TBD1 to be assigned by IANA.
INTER-LAYER Object-Type 1 to be assigned by IANA.
The format of the INTER-LAYER object body is shown in Figure 1.
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 |T|M|I|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: The INTER-LAYER Object
I flag (1 bit): The I flag is used by a PCC in a PCReq message to
indicate to a PCE whether an inter-layer path is allowed. When the I
flag is set (one), the PCE MAY perform inter-layer path computation
and return an inter-layer path. When the flag is clear (zero), the
path that is returned MUST NOT be an inter-layer path.
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The I flag is used by a PCE in a PCRep message to indicate to a PCC
whether the path returned is an inter-layer path. When the I flag is
set (one), the path is an inter-layer path. When it is clear (zero),
the path is contained within a single layer either because inter-
layer path computation was not performed or because a mono-layer path
(without any virtual TE link and without any loose hop that spans the
lower-layer network) was found notwithstanding the use of inter-layer
path computation.
M flag (1 bit): The M flag is used by a PCC in a PCReq message to
indicate to a PCE whether mono-layer path or multi-layer path is
requested. When the M flag is set (one), multi-layer path is
requested. When it is clear (zero), mono-layer path is requested.
The M flag is used by a PCE in a PCRep message to indicate to a PCC
whether mono-layer path or multi-layer path is returned. When M flag
is set (one), multi-layer path is returned. When M flag is clear
(zero), mono-layer path is returned.
If the I flag is clear (zero), the M flag has no meaning and MUST be
ignored.
[RFC6457] describes two sub-options for mono-layer path.
o A mono-layer path that is specified by strict hops. The path may
include virtual TE links.
o A mono-layer path that includes loose hops that span the lower-
layer network.
The choice of this sub-option can be specified by the use of O flag
in the RP object specified in [RFC5440].
T flag (1 bit): The T flag is used by a PCC in a PCReq message to
indicate to a PCE whether triggered signaling is allowed. When the T
flag is set (one), triggered signaling is allowed. When it is clear
(zero), triggered signaling is not allowed.
The T flag is used by a PCE in a PCRep message to indicate to a PCC
whether triggered signaling is required to support the returned path.
When the T flag is set (one), triggered signaling is required. When
it is clear (zero), triggered signaling is not required.
Note that triggered signaling is used to support hierarchical
[RFC4206] or stitched [RFC5150] LSPs according to the physical
attributes of the network layers.
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If the I flag is clear (zero), the T flag has no meaning and MUST be
ignored.
Note that the I flag and M flag differ in the following ways. When
the I flag is clear (zero), virtual TE links must not be used in path
computation. In addition, loose hops that span the lower-layer
network must not be specified. Only regular TE links from the same
layer may be used.
o When the I flag is set (one), the M flag is clear (zero), and the
T flag is set (one), virtual TE links are allowed in path
computation. In addition, when the O flag of the RP object is
set, loose hops that span the lower-layer network may be
specified. This will initiate lower-layer LSP setup, thus inter-
layer path is setup even though the path computation result from a
PCE to a PCC include hops from the same layer only.
o However, when the I flag is set (one), the M flag is clear (zero),
and the T flag is clear (zero), since triggered signaling is not
allowed, virtual TE links that have not been pre-signaled MUST NOT
be used in path computation. In addition, loose hops that span
the lower-layer network MUST NOT be specified. Therefore, this is
equivalent to the I flag being clear (zero).
Reserved bits of the INTER-LAYER object sent between a PCC and PCE in
the same domain MUST be transmitted as zero and SHOULD be ignored on
receipt. A PCE that forwards a path computation request to other
PCEs MUST preserve the settings of reserved bits in the PCReq
messages it sends and in the PCRep messages it forwards to PCCs.
Note that the flags in the PCRpt message indicate the state of an
LSP, whereas the flags in the PCUpd and the PCInitiate messages
indicate the intended/desired state as determined by the PCE.
3.2. SWITCH-LAYER Object
The SWITCH-LAYER object is optional on a PCReq message and specifies
switching layers in which a path MUST, or MUST NOT, be established.
A switching layer is expressed as a switching type and encoding type.
When a SWITCH-LAYER object is used on a PCReq it is interpreted in
the context of the INTER-LAYER object on the same message. If no
INTER-LAYER object is present, the PCE MUST process the SWITCH-LAYER
object as though inter-layer path computation had been explicitly
disallowed. In such a case, the SWITCH-LAYER object MUST NOT have
more than one LSP Encoding Type and Switching Type with the I flag
set.
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The SWITCH-LAYER object is optional on a PCRep message, where it is
used with the NO-PATH object in the case of unsuccessful path
computation to indicate the set of constraints that could not be
satisfied.
The SWTCH-LAYER object may be used on a PCRpt message consistent with
how properties of existing LSPs are reported on that message
[I-D.ietf-pce-stateful-pce]. The PCRpt message uses the <attribute-
list> as defined in [RFC5440] and extended by further PCEP
extensions. This message can use the <attribute-list> as extended in
Section 5 to carry the SWITCH-LAYER object. The SWTCH-LAYER object
is not used on a PCUpd or PCInitiate messages.
SWITCH-LAYER Object-Class TBD2 is to be assigned by IANA.
SWITCH-LAYER Object-Type 1 is to be assigned by IANA.
The format of the SWITCH-LAYER object body is shown in Figure 2.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP Enc. Type |Switching Type | Reserved |I|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . |
// . //
| . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP Enc. Type |Switching Type | Reserved |I|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: The SWITCH-LAYER Object
Each row indicates a switching type and encoding type that must or
must not be used for specified layer(s) in the computed path.
The format is based on [RFC3471], and has equivalent semantics.
LSP Encoding Type (8 bits): see [RFC3471] for a description of
parameters.
Switching Type (8 bits): see [RFC3471] for a description of
parameters.
I flag (1 bit): the I flag indicates whether a layer with the
specified switching type and encoding type must or must not be used
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by the computed path. When the I flag is set (one), the computed
path MUST traverse a layer with the specified switching type and
encoding type. When the I flag is clear (zero), the computed path
MUST NOT enter or traverse any layer with the specified switching
type and encoding type.
When a combination of switching type and encoding type is not
included in SWITCH-LAYER object, the computed path MAY traverse a
layer with that combination of switching type and encoding type.
A PCC may want to specify only a Switching Type and not an LSP
Encoding Type. In this case, the LSP Encoding Type is set to zero.
3.3. REQ-ADAP-CAP Object
The REQ-ADAP-CAP object is optional and is used to specify a
requested adaptation capability for both ends of the lower layer LSP.
The REQ-ADAP-CAP object is used in a PCReq message for inter-PCE
communication, where the PCE that is responsible for computing higher
layer paths acts as a PCC to request a path computation from a PCE
that is responsible for computing lower layer paths.
The REQ-ADAP-CAP object is used in a PCRep message in case of
unsuccessful path computation (in this case, the PCRep message also
contains a NO-PATH object, and the REQ-ADAP-CAP object is used to
indicate the set of constraints that could not be satisfied).
The REQ-ADAP-CAP object MAY be used in a PCReq message in a mono-
layer network to specify a requested adaptation capability for both
ends of the LSP. In this case, it MAY be carried without an INTER-
LAYER Object.
The applicability of this object to PCRpt and PCUpd messages follows
as the usage of other objects on those messages as described in
[I-D.ietf-pce-stateful-pce]. The applicability of this object to the
PCInitiate message follows as the usage of other objects on those
messages as described in [I-D.ietf-pce-pce-initiated-lsp]. These
messages use the <attribute-list> as defined in [RFC5440] and
extended by further PCEP extensions. These messages can use the
<attribute-list> as extended in Section 5 to carry the REQ-ADAP-CAP
object.
REQ-ADAP-CAP Object-Class TBD3 is to be assigned by IANA.
REQ-ADAP-CAP Object-Type 1 is to be assigned by IANA.
The format of the REQ-ADAP-CAP object body is shown in Figure 3.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Switching Cap | Encoding | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: The REQ-ADAP-CAP Object
The format is based on [RFC6001] and has equivalent semantics as the
Interface Adjustment Capability Descriptor (IACD) Upper Switching
Capability and Lower Switching Capability fields.
Switching Capability (8 bits): see [RFC4203] for a description of
parameters.
Encoding (8 bits): see [RFC3471] for a description of parameters.
A PCC may want to specify a Switching Capability, but not an
Encoding. In this case, the Encoding MUST be set zero.
3.4. New Metric Types
This document defines two new metric types for use in the PCEP METRIC
object.
IANA has assigned the value TBD5 to indicate the metric "Number of
adaptations on a path."
IANA has assigned the value TBD6 to indicate the metric "Number of
layers to be involved on a path."
See Section 4.1, Section 4.2, and Section 4.3 for a description of
how these metrics are applied.
3.5. SERVER-INDICATION Object
The SERVER-INDICATION is optional and is used to indicate that path
information included in the ERO is server layer information and
specify the characteristics of the server layer, e.g., the switching
capability and encoding of the server layer path.
The format of the SERVER-INDICATION object body is shown in Figure 4.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Switching Cap | Encoding | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Optional TLVs ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: The SERVER-INDICATION Object
SERVER-INDICATION Object-Class TBD4 to be assigned by IANA.
SERVER-INDICATION Object-Type 1 to be assigned by IANA.
Switching Capability (8 bits): see [RFC4203] for a description of
parameters.
Encoding (8 bits): see [RFC3471] for a description of parameters.
Optional TLVs: Optional TLVs MAY be included within the object to
specify more specific server layer path information (e.g., traffic
parameters). Such TLVs will be defined by other documents.
4. Procedures
4.1. Path Computation Request
A PCC requests or allows inter-layer path computation in a PCReq
message by including the INTER-LAYER object with the I flag set. The
INTER-LAYER object indicates whether inter-layer path computation is
allowed, which path type is requested, and whether triggered
signaling is allowed.
The SWITCH-LAYER object, which MUST NOT be present unless the INTER-
LAYER object is also present, is optionally used to specify the
switching types and encoding types that define layers that must, or
must not, be used in the computed path. When the SWITCH-LAYER object
is used with the INTER-LAYER object I flag clear (zero), inter-layer
path computation is not allowed, but constraints specified in the
SWITCH-LAYER object apply. Example usage includes path computation
in a single layer GMPLS network.
The REQ-ADAP-CAP object is optionally used to specify the interface
switching capability of both ends of the lower layer LSP. The REQ-
ADAP-CAP object is used in inter-PCE communication, where the PCE
that is responsible for computing higher layer paths makes a request
as a PCC to a PCE that is responsible for computing lower layer
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paths. Alternatively, the REQ-ADAP-CAP object may be used in the
NMS-VNTM model, where the VNTM makes a request as a PCC to a PCE that
is responsible for computing lower-layer paths.
The METRIC object is optionally used to specify metric types to be
optimized or bounded. When metric type TBD5 is used, it indicates
that path computation MUST minimize or bound the number of
adaptations on a path. When metric type TBD6 is used, it indicates
that path computation MUST minimize or bound the number of layers to
be involved on a path.
Furthermore, in order to allow different objective functions to be
applied within different network layers, multiple OF objects
[RFC5541] MAY be present. In such a case, the first OF object
specifies an objective function for the higher-layer network, and
subsequent OF objects specify objection functions of the subsequent
lower-layer networks.
4.2. Path Computation Reply
In the case of successful path computation, the requested PCE replies
to the requesting PCC for the inter-layer path computation result in
a PCRep message that MAY include the INTER-LAYER object. When the
INTER-LAYER object is included in a PCRep message, the I flag, M
flag, and T flag indicate semantics of the path as described in
Section 3.1. Furthermore, when the C flag of the METRIC object in a
PCReq is set, the METRIC object MUST be included in the PCRep to
provide the computed metric value, as specified in [RFC5440].
The PCE MAY specify the server layer path information in the ERO. In
this case, the requested PCE replies with a PCRep message that
includes at least two sets of ERO information in the path-list, one
is for the client layer path information, and another one is the
server layer path information. When SERVER-INDICATION is included in
a PCRep message, it indicates that the path in the ERO is the server
layer path information. The server layer path specified in the ERO
could be loose or strict. On receiving the replied path, the PCC
(e.g., NMS, ingress node) can trigger the signaling to setup the LSPs
according to the computed paths.
In the case of unsuccessful path computation, the PCRep message also
contains a NO-PATH object, and the SWITCH-TYPE object and/or the REQ-
ADAP-CAP MAY be used to indicate the set of constraints that could
not be satisfied.
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4.3. Stateful PCE and PCE Initiated LSPs
Processing for stateful PCEs is described in
[I-D.ietf-pce-stateful-pce]. That document defines the PCRpt message
to allow a PCC to report to a PCE an LSP that already exists in the
network and to delegate control of that LSP to the PCE.
When the LSP is a multi-layer LSP (or a mono-layer LSP for which
specific adaptations exist), the message objects defined in this
document are used on the PCRpt to describe an LSP that is delegated
to the PCE so that the PCE may process the LSP.
Furthermore, [I-D.ietf-pce-stateful-pce] defines the PCUpd message to
allow a PCE to modify an LSP that has been delegated to it. When the
LSP is a multi-layer LSP (or a mono-layer LSP for which specific
adaptations exist), the message objects defined in this document are
used on the PCUpd to describe the new attributes of the modified LSP.
Processing for PCE initiated LSPs is described in
[I-D.ietf-pce-pce-initiated-lsp]. That document defines the
PCInitiate message that is used by a PCE to request a PCC to set up a
new LSP. When the LSP is a multi-layer LSP (or a mono-layer LSP for
which specific adaptations exist), the message objects defined in
this document are used on the PCInitiate to describe the attributes
of the new LSP.
The new metric types defined in this document can also be used with
the stateful PCE extensions. The format of PCEP messages described
in [I-D.ietf-pce-stateful-pce] and [I-D.ietf-pce-pce-initiated-lsp]
uses <attribute-list> (which is extended in Section 5 for the purpose
of including the new metrics.
The stateful PCE implementation MAY use the extension of PCReq and
PCRep messages as defined in Section 5 to enable the use of inter-
layer parameters during passive stateful operations too, using the
LSP object.
5. Updated Format of PCEP Messages
Message formats in this section, as those in [RFC5440] are presented
using Routing Backus-Naur Format (RBNF) as specified in [RFC5511].
The format of the PCReq message is updated as shown in Figure 5
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<PCReq Message>::= <Common Header>
[<svec-list>]
<request-list>
where:
<svec-list>::=<SVEC>
[<svec-list>]
<request-list>::=<request>[<request-list>]
<request>::= <RP>
<END-POINTS>
[<LSP>]
[<LSPA>]
[<BANDWIDTH>]
[<metric-list>]
[<of-list>]
[<RRO>[<BANDWIDTH>]]
[<IRO>]
[<LOAD-BALANCING>]
[<INTER-LAYER> [<SWITCH-LAYER>]]
[<REQ-ADAP-CAP>]
where:
<of-list>::=<OF>[<of-list>]
<metric-list>::=<METRIC>[<metric-list>]
Figure 5: The Updated PCReq Message
The format of the PCRep message is updated as shown in Figure 6
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<PCRep Message> ::= <Common Header>
<response-list>
where:
<response-list>::=<response>[<response-list>]
<response>::=<RP>
[<LSP>]
[<NO-PATH>]
[<attribute-list>]
[<path-list>]
<path-list>::=<path>[<path-list>]
<path>::= <ERO><attribute-list>
where:
<attribute-list>::=[<of-list>]
[<LSPA>]
[<BANDWIDTH>]
[<metric-list>]
[<IRO>]
[<INTER-LAYER>]
[<SWITCH-LAYER>]
[<REQ-ADAP-CAP>]
[<SERVER-INDICATION>]
<of-list>::=<OF>[<of-list>]
<metric-list>::=<METRIC>[<metric-list>]
Figure 6: The Updated PCRep Message
6. Manageability Considerations
Implementations of this specification should provide a mechanism to
configure any optional features (such as whether a PCE supports
inter-layer computation, and which metrics are supported).
A Management Information Base (MIB) module for modeling PCEP is
described in [RFC7420]. Systems that already use a MIB module to
manage their PCEP implementations might want to augment that module
to provide controls and indicators for support of inter-layer
features defined in this document, and to add counters of messages
sent and received containing the objects defined here.
However, the preferred mechanism for configuration is through a YANG
model. Work has started on a YANG model for PCEP
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[I-D.ietf-pce-pcep-yang], and this could be enhanced as described for
the MIB module, above.
Additional policy configuration might be provided to allow a PCE to
discriminate between the computation services offered to different
PCCs.
A set of monitoring tools for the PCE-based architecture are provided
in [RFC5886]. Systems implementing this specification and PCE
monitoring should consider defining extensions to the mechanisms
defined in [RFC5886] to help monitor inter-layer path computation
requests.
7. IANA Considerations
IANA maintains a registry called the "Path Computation Element
Protocol (PCEP) Numbers". This document requests IANA to carry out
actions on subregistries of that registry.
7.1. New PCEP Objects
IANA is requested to make the following assignments from the "PCEP
Objects" subregistry.
Object-Class Value |Name |Object-Type |Reference
-------------------+-------+-----------------------+-----------
INTER-LAYER | TBD1 | 1: Inter-layer | [This.I-D]
| | 2-15: Unassigned |
SWITCH-LAYER | TBD2 | 1: Switch-layer | [This.I-D]
| | 2-15: Unassigned |
REQ-ADAP-CAP | TBD3 | 1: Req-Adap-Cap | [This.I-D]
| | 2-15: Unassigned |
SERVER-INDICATION | TBD4 | 1: Server-indication | [This.I-D]
Figure 7
7.2. New Registry for INTER-LAYER Object Flags
IANA is requested to create a new subregistry to manage the Flag
field of the INTER-Layer object called the "Inter-Layer Object Path
Property Bits" registry.
New bit numbers may be allocated only by an "IETF Review" action
[RFC5226]. Each bit should be tracked with the following qualities:
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o Bit number (counting from bit 0 as the most significant bit up to
a maximum of bit 31)
o Capability Description
o Defining RFC
IANA is requested to pre-populate the registry as follows:
Bit | Flag | Multi-Layer Path Property | Reference
----+------+-------------------------------+------------
0-28| Unassigned |
29 | T | Triggered Signalling Allowed | [This.I-D]
30 | M | Multi-Layer Requested | [This.I-D]
31 | I | Inter-Layer Allowed | [This.I-D]
Figure 8
7.3. New Metric Types
Two new metric types are defined in this document for the METRIC
object (specified in [RFC5440]). The IANA is requested to make the
following allocations from the "Metric Object T Field" registry.
Value | Description | Reference
------+---------------------------------+------------
TBD5 | Number of adaptations on a path | [This.I-D]
TBD6 | Number of layers on a path | [This.I-D]
Figure 9
IANA is further requested to update the registry to show an
assignment action of "IETF Consensus" as already documented in
[RFC5440].
8. Security Considerations
Inter-layer traffic engineering with PCE may raise new security
issues when PCE-PCE communication is done between different layer
networks for inter-layer path computation. Security issues may also
exist when a single PCE is granted full visibility of TE information
that applies to multiple layers.
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Path-Key-based mechanism defined in [RFC5520] MAY be applied to
address the topology confidentiality between different layers.
9. Acknowledgments
The authors would like to thank Cyril Margaria for his valuable
comments. Helpful comments and suggested text were offered by Dhruv
Dhody who also fixed the RBNF. Jonathan Hardwick provided a helpful
review as document shepherd.
10. Contributors
Jean-Louis Le Roux
France Telecom R&D
Av Pierre Marzin
Lannion
France
22300
Email: jeanlouis.leroux@orange.com
11. References
11.1. Normative References
[I-D.ietf-pce-pce-initiated-lsp]
Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP
Extensions for PCE-initiated LSP Setup in a Stateful PCE
Model", draft-ietf-pce-pce-initiated-lsp-07 (work in
progress), July 2016.
[I-D.ietf-pce-stateful-pce]
Crabbe, E., Minei, I., Medved, J., and R. Varga, "PCEP
Extensions for Stateful PCE", draft-ietf-pce-stateful-
pce-18 (work in progress), December 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3471] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description",
RFC 3471, DOI 10.17487/RFC3471, January 2003,
<http://www.rfc-editor.org/info/rfc3471>.
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[RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", RFC 3945,
DOI 10.17487/RFC3945, October 2004,
<http://www.rfc-editor.org/info/rfc3945>.
[RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005,
<http://www.rfc-editor.org/info/rfc4203>.
[RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
Hierarchy with Generalized Multi-Protocol Label Switching
(GMPLS) Traffic Engineering (TE)", RFC 4206,
DOI 10.17487/RFC4206, October 2005,
<http://www.rfc-editor.org/info/rfc4206>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<http://www.rfc-editor.org/info/rfc5440>.
[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,
DOI 10.17487/RFC5520, April 2009,
<http://www.rfc-editor.org/info/rfc5520>.
11.2. Informative References
[I-D.ietf-pce-pcep-yang]
Dhody, D., Hardwick, J., Beeram, V., and j.
jefftant@gmail.com, "A YANG Data Model for Path
Computation Element Communications Protocol (PCEP)",
draft-ietf-pce-pcep-yang-01 (work in progress), October
2016.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<http://www.rfc-editor.org/info/rfc4655>.
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[RFC5150] Ayyangar, A., Kompella, K., Vasseur, JP., and A. Farrel,
"Label Switched Path Stitching with Generalized
Multiprotocol Label Switching Traffic Engineering (GMPLS
TE)", RFC 5150, DOI 10.17487/RFC5150, February 2008,
<http://www.rfc-editor.org/info/rfc5150>.
[RFC5212] Shiomoto, K., Papadimitriou, D., Le Roux, JL., Vigoureux,
M., and D. Brungard, "Requirements for GMPLS-Based Multi-
Region and Multi-Layer Networks (MRN/MLN)", RFC 5212,
DOI 10.17487/RFC5212, July 2008,
<http://www.rfc-editor.org/info/rfc5212>.
[RFC5339] Le Roux, JL., Ed. and D. Papadimitriou, Ed., "Evaluation
of Existing GMPLS Protocols against Multi-Layer and Multi-
Region Networks (MLN/MRN)", RFC 5339,
DOI 10.17487/RFC5339, September 2008,
<http://www.rfc-editor.org/info/rfc5339>.
[RFC5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
Used to Form Encoding Rules in Various Routing Protocol
Specifications", RFC 5511, DOI 10.17487/RFC5511, April
2009, <http://www.rfc-editor.org/info/rfc5511>.
[RFC5541] Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of
Objective Functions in the Path Computation Element
Communication Protocol (PCEP)", RFC 5541,
DOI 10.17487/RFC5541, June 2009,
<http://www.rfc-editor.org/info/rfc5541>.
[RFC5623] Oki, E., Takeda, T., Le Roux, JL., and A. Farrel,
"Framework for PCE-Based Inter-Layer MPLS and GMPLS
Traffic Engineering", RFC 5623, DOI 10.17487/RFC5623,
September 2009, <http://www.rfc-editor.org/info/rfc5623>.
[RFC5886] Vasseur, JP., Ed., Le Roux, JL., and Y. Ikejiri, "A Set of
Monitoring Tools for Path Computation Element (PCE)-Based
Architecture", RFC 5886, DOI 10.17487/RFC5886, June 2010,
<http://www.rfc-editor.org/info/rfc5886>.
[RFC6001] Papadimitriou, D., Vigoureux, M., Shiomoto, K., Brungard,
D., and JL. Le Roux, "Generalized MPLS (GMPLS) Protocol
Extensions for Multi-Layer and Multi-Region Networks (MLN/
MRN)", RFC 6001, DOI 10.17487/RFC6001, October 2010,
<http://www.rfc-editor.org/info/rfc6001>.
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[RFC6457] Takeda, T., Ed. and A. Farrel, "PCC-PCE Communication and
PCE Discovery Requirements for Inter-Layer Traffic
Engineering", RFC 6457, DOI 10.17487/RFC6457, December
2011, <http://www.rfc-editor.org/info/rfc6457>.
[RFC7420] Koushik, A., Stephan, E., Zhao, Q., King, D., and J.
Hardwick, "Path Computation Element Communication Protocol
(PCEP) Management Information Base (MIB) Module",
RFC 7420, DOI 10.17487/RFC7420, December 2014,
<http://www.rfc-editor.org/info/rfc7420>.
[RFC7926] Farrel, A., Ed., Drake, J., Bitar, N., Swallow, G.,
Ceccarelli, D., and X. Zhang, "Problem Statement and
Architecture for Information Exchange between
Interconnected Traffic-Engineered Networks", BCP 206,
RFC 7926, DOI 10.17487/RFC7926, July 2016,
<http://www.rfc-editor.org/info/rfc7926>.
Authors' Addresses
Eiji Oki
University of Electro-Communications
Tokyo
Japan
Email: oki@ice.uec.ac.jp
Tomonori Takeda
NTT
3-9-11 Midori-cho
Musashino-shi, Tokyo
Japan
Email: tomonori.takeda@ntt.com
Adrian Farrel
Juniper Networks
Email: afarrel@juniper.net
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Fatai Zhang
Huawei Technologies Co., Ltd.
F3-5-B R&D Center, Huawei Base
Bantian, Longgang District, Shenzhen 518129
P. R. China
Phone: +86-755-28972912
Email: zhangfatai@huawei.com
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