PCEP Extension for Stateful Inter-Domain Tunnels
draft-ietf-pce-stateful-interdomain-04
| Document | Type | Active Internet-Draft (pce WG) | |
|---|---|---|---|
| Authors | Olivier Dugeon , Julien Meuric , Young Lee , Daniele Ceccarelli | ||
| Last updated | 2023-10-23 | ||
| Replaces | draft-dugeon-pce-stateful-interdomain | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | (None) | ||
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| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
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draft-ietf-pce-stateful-interdomain-04
Path Computation Element Working Group 0. Dugeon
Internet-Draft J. Meuric
Intended status: Standards Track Orange Labs
Expires: 25 April 2024 Y. Lee
Samsung Electronics
D. Ceccarelli
Cisco System
23 October 2023
PCEP Extension for Stateful Inter-Domain Tunnels
draft-ietf-pce-stateful-interdomain-04
Abstract
This document specifies how to use a Backward Recursive or
Hierarchical method to derive inter-domain paths in the context of
stateful Path Computation Element (PCE). The mechanism relies on the
PCInitiate message to set up independent paths per domain. Combining
these different paths together enables them to be operated as end-to-
end inter-domain paths, without the need for a signaling session
between inter-domain border routers. It delivers a new tool in the
MPLS toolbox in order for operator to build Intent-Based Networking.
For this purpose, this document defines a new Stitching Label, new
Association Type, and a new PCEP communication Protocol (PCEP)
Capability.
Status of This Memo
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This Internet-Draft will expire on 25 April 2024.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. General Assumptions . . . . . . . . . . . . . . . . . . . 4
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6
2. Stitching Label . . . . . . . . . . . . . . . . . . . . . . . 8
2.1. Definition . . . . . . . . . . . . . . . . . . . . . . . 8
2.2. Inter-domain traffic steering . . . . . . . . . . . . . . 8
2.2.1. Stitching RSVP-TE . . . . . . . . . . . . . . . . . . 9
2.2.2. Stitching Segment Routing . . . . . . . . . . . . . . 9
2.2.3. Strict traffic steering . . . . . . . . . . . . . . . 10
2.3. Inter-domain Flags for TE-PATH-BINDING TLV . . . . . . . 10
2.4. Operations . . . . . . . . . . . . . . . . . . . . . . . 11
3. Backward Recursive PCInitiate Procedure . . . . . . . . . . . 12
3.1. Mode of Operation . . . . . . . . . . . . . . . . . . . . 12
3.2. Example . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.3. Completion Failure of Inter-domain Path Setup
Procedure . . . . . . . . . . . . . . . . . . . . . . . . 18
4. Hierarchical PCInitiate Procedure . . . . . . . . . . . . . . 18
4.1. Mode of Operation . . . . . . . . . . . . . . . . . . . . 19
4.2. Completion Failure of Inter-domain Path Setup
Procedure . . . . . . . . . . . . . . . . . . . . . . . . 21
4.3. Example for Stateful H-PCE Stiching Procedure . . . . . . 22
5. Inter-domain Path Management . . . . . . . . . . . . . . . . 25
5.1. Stitching Label PCE Capabilities . . . . . . . . . . . . 25
5.2. Identification of Inter-domain Paths . . . . . . . . . . 26
5.3. Inter-domain Association Group . . . . . . . . . . . . . 27
5.4. Modification of Inter-domain Paths . . . . . . . . . . . 28
5.5. Modification of Local Paths . . . . . . . . . . . . . . . 29
5.6. Tear-Down of Inter-domain Paths . . . . . . . . . . . . . 29
6. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 30
6.1. Mixing Technologies . . . . . . . . . . . . . . . . . . . 30
6.2. Inter-Area . . . . . . . . . . . . . . . . . . . . . . . 31
6.3. Nested traffic . . . . . . . . . . . . . . . . . . . . . 31
6.4. VPN . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
6.5. Intent-Based Networking . . . . . . . . . . . . . . . . . 32
6.6. QoS management . . . . . . . . . . . . . . . . . . . . . 33
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 33
7.1. TE-PATH-BINDING flag . . . . . . . . . . . . . . . . . . 33
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7.2. Association Type Value . . . . . . . . . . . . . . . . . 34
7.3. PCEP Error Values . . . . . . . . . . . . . . . . . . . . 34
7.4. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 35
7.5. Stitching Label PCE Capability . . . . . . . . . . . . . 35
8. Security Considerations . . . . . . . . . . . . . . . . . . . 35
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 36
10. Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . 36
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 36
11.1. Normative References . . . . . . . . . . . . . . . . . . 36
11.2. Informative References . . . . . . . . . . . . . . . . . 37
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 39
1. Introduction
The PCE working group has produced a set of RFCs to standardize the
behavior of the Path Computation Element ([RFC4655] and [RFC5440]) as
a tool to help MultiProtocol Label Switching - Traffic Engineering
(MPLS-TE)/Generalized MPLS (GMPLS) Label Switched Paths (LSPs) and
Segment Routing paths placement. This also includes the ability to
compute inter-domain LSPs or Segment Routing paths following a
distributed BRPC [RFC5441] or hierarchical H-PCE [RFC6805] approach.
Such inter-domain paths could then serve as an Explicit Route Object
(ERO) input for the RSVP-TE signaling to set up the tunnels within
the underlying network. Three kinds of inter-domain paths could be
established:
* Contiguous tunnel ([RFC3209] and [RFC3473]): The RSVP-TE signaling
crosses the boundary between two domains. This kind of tunnel is
not recommended mostly for security and scalability purpose. In
addition, the initiating domain imposes huge constraints on
subsequent domains, because they undergo the tunnel request
without being able to control it.
* Stitching tunnel ([RFC5150]): Each domain establishes in its own
network the corresponding part of the inter-domain path
independently. Then, a second end-to-end RSVP-TE Path message is
sent by the initiating domain to stitch the different tunnel parts
to form the inter-domain path.
* Nesting tunnel ([RFC4206]): This is similar to the stitching mode
but, this time, with the possibility to set up tunnel hierarchy.
However, these inter-domain paths depend on signaling using RSVP-TE
to be set up, but it is not common to allow signaling across
administrative domain borders, especially in operational networks.
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For Segment Routing, issues are different as there is no signaling
between routers. First, a segment path depends on a stack of segment
identifiers but, in an inter-domain path, this stack may become too
large with respect to hardware constraint. If Extensions for Segment
Routing [RFC8664] takes into account the Maximum Stack Depth (MSD), a
PCE may be unable to find a solution when it computes an end-to-end
inter-domain path. The second issue is related to the path
confidentiality because all Node-SID must be stacked by the head end
router while some of the Node-SIDs are associated to routers of the
next domains. It is clear that operators would not disclose details
of their network, which includes Node-SIDs. Thus, it is not possible
to stack remote labels for an end-to-end inter-domain path even if
MSD constraint is respected.
The purpose of this document is to take the benefit of Active
Stateful PCE [RFC8231] and PCE-Initiated [RFC8281] modes to stitch or
nest inter-domain paths directly using PCEP between domains' PCEs
while avoiding the use of another signaling between inter-domain
border nodes. The mechanism keeps each operator free to
independently set up their respective part of the inter-domain paths,
i.e. the signaling (for MPLS-TE and GMPLS) is scoped on a per domain
basis, individually.
The PCInitiate message is used from destination domain to source
domain, to recursively set up the end-to-end tunnel. Binding Label /
Segment Identifier (BSID) [I-D.ietf-pce-binding-label-sid] is used to
convey the specific labels or SIDs to automatically stitch or nest
the different local LSPs. And PCRep in conjunction with PCUpd
messages are used to report, maintain, modify and tear down inter-
domain paths. This method is also applicable to Segment Routing to
build inter-domain segment paths. To enable this mechanism, this
document defines a new Stitching Label, new Association Type, and a
new PCEP communication Protocol (PCEP) Capability.
1.1. General Assumptions
In the remainder of this document, the same references as per BRPC
[RFC5441] are used and the following set of assumptions are made (see
figure below):
* Domain refers to administrative partitions, i.e. an IGP area or an
Autonomous System (AS).
* Inter-domain path is used to refer to a path that crosses two or
more different domains as defined previously,
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* At least one PCE is deployed in each domain. These PCEs are all
active stateful-capable and can request to enforce LSPs in their
respective domain by means of PCInitiate messages.
* LSRs, including border nodes, are PCC-enabled and support active
stateful mode. PCEP sessions are established between these
routers and their domains' PCE.
* Each PCE establishes a PCEP session with its respective neighbor
domains' PCEs. The way a PCE discovers its neighboring PCEs is
out of the scope of this document.
* Each PCC is able to configure a Binding Label/Segment Identifier
(BSID) and each PCE is able to request a BSID to a PCC or a
neighbor domains' PCE.
* PCEs are able to compute an end-to-end path as per BRPC procedure
[RFC5441] or as per H-PCE procedure (stateless [RFC6805] or
stateful [RFC8751]).
* "Path" is a generic term to refer to both LSP setup by mean of
RSVP-TE or Segment Path in a Segment Routing network.
...(H-PCE)...........................
. . .
. . .
-------------- -------------- --------------
|Domain-A . | | . Domain-B| | . Domain-C|
| . | | . | | . |
| PCE------+--PCEP---+---PCE--------+--PCEP---+---PCE |
| / | | / | | / |
| / | | / | | / |
| Src=========BNA-------BNB1===========BNB2------BNC=========Dst |
| | Inter- | | Inter- | |
-------------- Domain -------------- Domain --------------
Link Link
Figure 1: Example of the representation of 3 domains with 3 PCEs
Operations, according to the figure above, are as follow:
1. The PCEs in Domain-A, Domain-B, and Domain-C communicate using
PCEP either directly, as shown, using BRPC or with a parent PCE
if using H-PCE.
2. The PCE in Domain-A selects an end-to-end domain path. It tells
the PCE in Domain-B that the path will be used, and that PCE
passes the information on to the PCE in Domain-C.
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3. Each of the PCEs use PCEP to instruct the segment head ends
backward from destination to source:
a. In Domain-C, the PCE instructs the ingress Border Node, BNC,
with the path to reach the Destination. The instructions
also ask BNC to provide the incoming label or SID that will
be stitched to the intra-domain path. Once done, PCE reports
this label or SID to PCE of Domain-B.
b. In Domain-B, the PCE instructs the ingress Border Node, BNB1,
with the path to reach the egress Border Node, BNB2. The
instructions also tell BNB1 the label or SID to use on the
inter-domain link to BNC and ask to provide the incoming
label or SID that will be stitched to the intra-domain path.
Once done, PCE reports this label or SID to PCE of Domain-A.
c. In Domain-A, the PCE instructs the Source node with the path
to use to reach Border Node, BNA. The instructions also
include the label or SID to use on the inter-domain link to
BNB1.
1.2. Terminology
ABR: Area Border Routers. Routers used to connect two IGP areas
(areas in OSPF or levels in IS-IS).
AS: Autonomous System
ASBR: Autonomous System Border Router. Router used to connect
together ASes (of the same or different service providers) via one or
more inter-AS links.
BSID: Binding Label / Segment Identifier.
Border Node (BN): a boundary node is either an ABR in the context of
inter-area TE or an ASBR in the context of inter-AS TE.
BN-en(i): Entry BN of domain(i) connecting domain(i-1) to domain(i)
along a determined sequence of domains. Multiple entry BN-en(i)
could be used to connect domain(i-1) to domain(i).
BN-ex(i): Exit BN of domain(i) connecting domain(i) to domain(i+1)
along a determined sequence of domains. Multiple exit BN-ex(i) could
be used to connect domain(i) to domain(i+1).
Domains: Autonomous System (AS) or IGP Area. An Autonomous System is
composed by one or more IGP area.
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ERO(i): The Explicit Route Object scoped to domain(i)
IGP-TE: Interior Gateway Protocol with Traffic Engineering support.
Both OSPF-TE and IS-IS-TE are identified in this category.
Inter-domain path: A path that crosses two or more domains through a
pair of Border Node (BN-ex, BN-en).
LK(i): A Link that connect BN-ex(i-1) to BN-en(i). Note that BN-
ex(i-1) could be connected to BN-en(i) by more than one link. LK(i)
identifies which of the multiple links will be used for the inter-
domain path setup. For inter-AS scenario, LK(i) represents the link
between ASBR of domain i to the ASBR of domain i-1. For inter-area
scenario, LK(i) is present only in IS-IS networks and represents the
link between ABR of region L1, reciprocally L2, to the ABR of region
L2, reciprocally L1.
Local path: A path that does not cross a domain border. It is set up
either from entry BN-en, to output BN-ex or between both. This path
could be enforce by means of RSVP-TE signaling or Segment Routing
labels stack.
Local path(i): A Local path of domain(i)
PLSP-ID(i): A PLSP-ID that identifies, in the domain(i), the local
part of an inter-domain path.
PCE: Path Computation Element. An entity (component, application, or
network node) that is capable of computing a network path or route
based on a network graph and applying computational constraints.
PCE(i) is a PCE within the scope of domain(i).
R(i,j): The router j of domain i
Stitching Label (SL): A dedicated label that is used to stitch two
RSVP-TE LSPs or two Segment Routing paths.
SL(i): A Stitching Label that links domain(i-1) to domain(i) and is
conveyed as an inter-domain BSID.
TPB(): An empty TE-PATH-BINDING TLV to request an inter-domain BSID
i.e. a Stitching Label.
TPB(i): A TE-PATH-BINDING TLV with an inter-domain Binding Value
equal to the Stitching Label SL(i).
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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 RFC 2119 [RFC2119].
2. Stitching Label
This section introduces the concept of Stitching Label that allows
stitching and nesting of local paths in order to form an inter-domain
path that cross several different domains.
2.1. Definition
The operation of stitch or nest a local path(i) to a local path(i+1)
in order to form and inter-domain path mainly consists in defining
the label that the output BN-ex(i) will use to send its traffic to
the entry BN-en(i+1). Indeed, the entry BN-en(i+1) needs to identify
the incoming traffic (e.g. IP packets), in order to know if this
traffic must follow the local path(i+1) or not. Forwarding
Equivalent Class (FEC) could be used for that purpose. But, when
stitching or nesting tunnels, the FEC is reduced to the incoming
label that the entry BN-en(i+1) has chosen for the local path(i+1).
In this document, we introduce the term of "Stitching Label (SL)" to
refer to this label. Such label is usually exchanged between output
BN-ex(i) and entry BN-en(i+1) with the RSVP-TE signaling. But, as we
want to avoid to use RSVP-TE signaling due to operational
constraints, and allow compatibility support for Segment Routing,
this Stitching Label is here conveyed by PCEP. Binding Label /
Segment Identifier (BSID) [I-D.ietf-pce-binding-label-sid] defines a
new TE-PATH-BINDING TLV to exchange a Binding Segment / Label
Identifier (BSID) between a PCC and a PCE. This BSID is then used to
steer incoming traffic using this BSID into the associated path.
Thus, the Stitching Label defines in this draft is a particular use
case of BSID, named inter-domain BSID, and could be conveyed in the
TE-PATH-BINDING TLV of the LSP Object without any modification of
PCEP nor PCEP Objects.
2.2. Inter-domain traffic steering
If BSID allows to automatically steer traffic identified with this
BSID into the associated path, for inter-domain BSID, it is different
as the Stitching Label is associated to the inter-domain link LK(i+1)
i.e. the link between the border node BN-ex(i) of the domain(i) and
the border node BN-en(i+1) of the domain(i+1). Indeed, the Border
Node BN-en(i+1) needs to received the traffic identified by the
Stitching Label SL(i+1) from BN-ex(i). Thus, it is necessary to
instruct the border node BN-ex(i) to push the Stitching Label(i+1) on
top of the packets of traffic going from domain(i) to domain(i+1),
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and send them to the border node BN-en(i+1) through the inter-domain
link LK(i+1). Depending of technology used by domain(i), RSVP-TE or
Segment Routing, the operation uses two different approaches.
.-,( ),-. .-,( ),-.
+----+ .-( ) +----+ LK(i+1) +----+ ( )-.
| BN |( Domain(i) )| BN |------------| BN |( Domain(i+1 )
+----+ '-( ) +----+ SL(i+1) +----+ ( ).-'
| '-.( ).-' | | '-.( ).-'
BN-en(i) BN-ex(i) BN-en(i+1)
Figure 2: Inter-domain Link
2.2.1. Stitching RSVP-TE
In case of RSVP-TE, the Border Node BN-ex(i) needs to received the
Stitching Label from BN-en(i) through the RSVP-TE message and install
in its L(F)IB a SWAP instruction to the Stitching Label and forward
it to the next Border Node BN-en(i+1). For that purpose, the Egress
Control mechanism, as per RFC4003 section 2.1 [RFC4003], is
RECOMMENDED to instruct the Border Node BN-ex(i) of this action.
Other mechanisms to program the L(F)IB could be used, e.g. NETCONF.
Thus, PCE(i) SHOULD provide SL(i+1) and LK(i+1) to the PCC BN-en(i)
through the ERO = {..., [LK(i+1), SL(i+1)]} as the last SubObject in
conformance to [RFC4003]. As a result, BN-ex(i) installs in its MPLS
L(F)IB the SWAP instruction to label SL(i+1) with forward to LK(i+1).
It is left to implementation of PCE to get the LK(i+1) value. One
solution consist to retrieve it from the PKS(i) or the ERO previously
computed during the BRPC process.
2.2.2. Stitching Segment Routing
In case of Segment Routing, the Stitching Label SL(i+1) will be
inserted into the label stack in order to become the top label in the
stack when the packet reaches BN-en(i+1). Thus, the Stitching Label
SL(i+1) serves as a Binding SID entry for BN-en(i+1) to identify the
packets that follow the next Segment Path. For that purpose, BN-
en(i) MUST install in its MPLS L(F)IB an instruction to replace the
incoming Stitching Label SL(i) by the label stack given by the ERO(i)
plus the Stitching Label SL(i+1).
When a packet reaches BN-ex(i), the last label in the stack before
the label SL(i+1) corresponds to a SID that allows to reach BN-
en(i+1). When there are multiple interfaces between Border Nodes,
BN-ex(i) needs to know how to send the packets to BN-en(i+1).
Similarly to the Egress Control mechanism used with RSVP-TE, it is
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RECOMMENDED to use the inter-domain SID defined as per draft Egress
Peer Engineering [RFC9086] for that purpose. The inter-domain SID
named here I-SID(i+1) is announced by BN-ex(i) to PCE(i) through BGP-
LS for each interface that connect BN-ex(i) to neighbors BN-en(i+1).
Thus, PCE(i) SHOULD provide SL(i+1) and I-SID(i+1) to the PCC BN-
en(i) through the EROso that the label stack will end with {BN-ex(i)
SID, I-SID(i+1), SL(i+1)} and should be processed as follows:
* The penultimate router of domain(i) pops its node SID, and sends
the packet to the next node designated by the top label in the
label stack, i.e. the node SID of BN-ex(i) or the adjacency SID of
the link between the router and BN-ex(i).
* BN-ex(i) pops its node SID or its adjacency SID and looks up the
next label in the stack, i.e. the inter-domain SID which
corresponds to the interface to BN-en(i+1). BN-ex(i) pops this
inter-domain SID as well and sends the packet to BN-ex(i) through
the corresponding interface.
* BN-en(i+1) looks up the top label which is the Stitching Label
SL(i+1), pops it and replaces it by the sub-sequent label stack.
Other mechanisms, e.g. NETCONF, could be used to configure the
inter-domain SID on exit Border Nodes.
2.2.3. Strict traffic steering
The Binding Label / Segment Identifier has been defined as a global
traffic steering identifier. Thus, if an entry border node BN-en(i)
is configured with a Stitching Label SL(i), any domain connected to
this border node through different interface could send traffic to
domain(i) and subsequent domains even if they are not part of the
inter-domain path. However, some operators would prefer to configure
a strict enforcement of traffic steering. In this case, the border
node BN-en(i) SHOULD restrict the MPLS L(F)IB configuration to accept
traffic with the Stitching Label SL(i) to the incoming link LK(i).
2.3. Inter-domain Flags for TE-PATH-BINDING TLV
In order to convey the Stitching Label and manage traffic steering at
inter-domain, this specification defines new flags (See IANA section
of this document) for the Binding Label / Segment Identifier. The
format of the TE-PATH-BINDING TLV is defined in Binding Label /
Segment Identifier (BSID) [I-D.ietf-pce-binding-label-sid] and
included here for easy reference with the addition of the new flags
as follow:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 55 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BT |R|I|S| Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Binding Value (variable length) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: TE-PATH-BINDING TLV
* I flag: Inter-Domain Binding indicates that this Binding Value
corresponds to an inter-domain path, thus that this Binding Value
is a Stitching Label.
* S flag: Strict Binding indicates that the PCC MUST restrict the
Binding Value to the interface that corresponds to the domain
source End-Point of the associated path and MUST reject incoming
traffic with this Binding Value when it reaches the PCC through
another interface.
2.4. Operations
An empty TE-PATH-BINDING TLV with the I flag set to 1 MUST be present
in a PCInitiate messages sent by a PCE(i-1) to its neighbor PCE(i) in
the Backward Recursive method or by the Parent PCE to the Child
PCE(i) to initiate a new inter-domain path. In its response, the
neighbor PCE(i) or Child PCE(i) MUST return a Stitching Label SL in
the TE-PATH-BINDING TLV with the I flag set in the LSP object of the
PCRpt message to PCE(i-1) or the Parent PCE. PCE(i-1) MUST NOT
provide a Stitching Label as a Binding Value of the TE-PATH-BINDING
TLV to its neighbor PCE(i).
An empty TE-PATH-BINDING TLV with the I flag set to 1 MUST be present
in the PCInitiate message sent by a PCE(i) requesting to a PCC of
domain(i) to initiate a new local path(i) which is part of an inter-
domain path. The I flag MUST be set by the PCE(i) only after
receiving a PCInitiate message with an empty TE-PATH-BINDING with the
I flag set from a neighbor PCE(i-1) in the Backward Recursive method
or Parent PCE in the Hierarchical method. In its response, the PCC
of domain(i) MUST return a Stitching Label SL in the TE-PATH-BINDING
TLV with the I flag set in the LSP object of the PCRpt message.
Alternatively, the PCE(i) could provide a Stitching Label as a
Binding Value of the TE-PATH-BINDING TLV with the I flag set to the
PCC of the domain(i) when initiating a new local path(i) as per
section #8 of draft Binding Label / Segment Identifier (BSID)
[I-D.ietf-pce-binding-label-sid]. If the PCC is not able to allocate
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a BSID for inter-domain, it MUST send a PCErr message with Error-Type
= "Binding label/SID failure" and Error-Value = "Unable to allocate a
new binding label/SID" defined in draft Binding Label / Segment
Identifier (BSID) [I-D.ietf-pce-binding-label-sid].
If a PCE(i) receives a PCRpt without a TE-PATH-BENDING TLV while it
has requested a Stitching Label in the PCInitiate message, it MUST
send a PCErr message with Error-Type = "Mandatory Object missing""
and Error-Value = TBD2. If a PCE(i) receives a PCRpt with a TE-PATH-
BENDING TLV with the I flag unset while it has requested a Stitching
Label in the PcInitiate message, it MUST send a PCErr message with
Error-Type = "Binding label/SID failure" and Error-Value = TBD3.
PCE(i) SHOULD set the S flag in addition to the I flag if it requests
traffic steering strictly coming from a given interface, i.e.
traffic using the BSID and coming from a different interface MUST be
rejected by the PCC. When the S flag is set, PCE(i) MUST set the
EndPoint source address of the requested local path with the IP
address of the interface where the traffic is strictly steered. When
the PCC receives an LSP object with an empty TE-PATH-BINDING TLV and
the S flag set, it MUST allocate a Binding Value and configure its
MPLS L(F)IB to accept traffic with this BSID only coming from the
interface identified by the source address of the EndPoint Object.
If the PCC is not be able to strictly steer traffic, it MUST send a
PCErr message with Error-Type = "Binding label/SID failure" and
Error-Value = "Unable to allocate a new binding label/SID".
3. Backward Recursive PCInitiate Procedure
This section describes how to set up inter-domain paths that cross
different domains by using a Backward Recursive method. It is
compatible with the inter-domain path computation by means of the
BRPC procedure as describe in RFC5441 [RFC5441].
3.1. Mode of Operation
This section describes how PCInitiate and PCRpt messages are combined
between PCE in order to set up inter-domain paths between a source
domain(1) to a destination domain(n). S and D are respectively the
source and destination of the inter-domain path. Domain(1) and
domain(n) are different and connected through 0 (i.e. direct
connection when n = 2) or more intermediate domains denoted domain(i)
with i = [2, n-1].
First, the PCE(1) runs standard BRPC algorithm as per RFC5441
[RFC5441] with its neighbor PCEs in order to compute the inter-domain
path from S to D, where S and D are respectively a node in the
domain(1) and domain(n). Path Key confidentiality as per RFC5520
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[RFC5520] SHOULD be used to obfuscate the detailed ERO(i) of the
different domains(i). The resulting ERO is in the form {S, PKS(1),
BN-ex(1), ..., BN-en(i), PKS(i), BN-ex(i), ..., BN-en(n), PKS(n), D}
when Path Key is used and of the form {S, R(1,1), ..., R(1,k), BN-
ex(1), ..., BN-en(i), R(i,1), ..., R(i,l), BN-ex(i), ..., BN-en(n),
R(n,1), ..., R(n,m), D} otherwise . As subsequent domains are not
aware about the computed end-to-end ERO in case of Virtual Source
Path trees (VSPTs), the final ERO selected by the PCE(1) MUST be sent
in the PCInitiate message to indicate to the subsequent PCEs which
path has been finally chosen. PCE(1) MUST ensure that this ERO is
self comprehensive by subsequent PCEs. Indeed, when a PCE(i)
receives the ERO, it MUST be able to verify that this ERO matches its
own scope and be able to determine the next PCE(i+1). When Path Key
is used, PCEs MUST encode the Path Key with a reachable IP address so
that previous PCEs in the AS chain are able to join them. When Path
Key is not used, the PCEs MUST be able to retrieve an IP address of
the next PCE corresponding to the ERO (e.g., relying on a per prefix
table).
The complete procedure with Path Key follows the different steps
described below:
Steps 1: Initialization
Once ERO(S, D) is computed, PCE(1) sends a PCInitiate message to
PCE(2) containing an ERO equal to {S, PKS(2), ..., PKS(i), ...,
PKS(n), D}, an LSP Object containing an empty TE-PATH-BINDING TLV
with the I flag set and the End-Points Object = (S, D). The ERO
corresponds to the one PCE(1) has received from PCE(2) during the
BRPC process in which only Path Key are kept. In case of multiple
EROs, i.e. VSPT, PCE(1) has chosen one of them and used the selected
one for the PCInitiate message. PKS(i) could be replaced by the full
ERO description if Path Key is not used by PCE(i).
When PCE(i) receives a PCInitiate message from domain(i-1) with an
LSP containing an empty TE-PATH-BINDING TLV with I flag set and ERO =
{PKS(i), PKS(i+1), ..., PKS(n), D)}, it MUST sends the received
PCInitiate message to PCE(i+1) with a popped ERO and records its
received PKS(i) part. All PCE(i)s MUST generate the appropriate
PCInitiate message to PCE(i+1) up to PCE(n), i.e. to the destination
domain(n).
Steps 2: Actions taken at the destination domain(n) by PCE(n)
1. When a PCInitiate message reaches the destination domain(n),
PCE(n) retrieves the detailed ERO(n) from the PKS(n) if necessary
and MUST send to BN-en(n) a PCInitiate message with the ERO(n) =
{BN-en(n), ..., D}, an LSP containing an empty TE-PATH-BINDING
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TLV with the I flag set and End-Points Object = {BN(n), D} in
order to inform the PCC BN-en(n) that this local path(n) is part
of an inter-domain service and that it MUST allocate a Binding
Value for this path.
2. When the PCC BN-en(n) receives the PCInitiate message from its
PCE(n), it sets up the local path from entry BN-en(n) to D by
means of RSVP-TE signaling or Segment Routing, accordingly to the
PST value, with the given ERO(n).
3. Once the tunnel is set up, BN-en(n) chooses a free label for the
Stitching Label SL(n) and adds a new entry in its MPLS L(F)IB
with this SL(n) label. Then, it MUST send a PCRpt message to its
PCE(n) including PLSP-ID(n) and a TE-PATH-BINDING TLV with the
Binding Value equal to SL(n) and the I flag set
4. Once PCE(n) receives the PCRpt from the PCC BN-en(n) with the
RRO, PLSP-ID and TE-PATH-BINDING TLV with the I flag set, it MUST
send to the PCE(n-1) a PCRpt containing the TE-PATH-BINDING TLV
it received from the PCC BN-en(n) and PLSP-ID(n). PCE(n) MAY add
{PKS(n), D} in the RRO.
Steps i: Actions performed by all intermediate domains(i), for i = 2
to n-1
1. When the PCE(i) receives a PCRpt message from domain(i+1) with an
LSP object containing PLSP-ID(i+1) and a Binding Value in the TE-
PATH-BINDIG TLV with the I flag set, it retrieves the detailed
ERO(i) from the PKS(i), recorded in step 1, if necessary. Then,
it MUST send to the PCC BN-en(i) a PCInitiate message with this
ERO(i), an LSP object containing an empty TE-PATH-BINDING TLV
with the I flag set and the End-Points Object = {BN-en(i), BN-
ex(i)} in order to inform the PCC BN-en(i) that this local
path(i) is part of an inter-domain path and that it MUST allocate
a Binding Value for this path. PCE(i) sets Path Setup Type (PST)
to 0, respectively to 1 to instruct the PCC to enforce the local
path by means of RSVP-TE respectively Segment Routing.
2. Egress Control mechanism, as per RFC4003 section 2.1 [RFC4003]
for RSVP-TE, respectively, Egress Peer Engineering [RFC9086] for
Segment Routing, is used to stitch and steer traffic between the
border node BN-ex(i) and BN-en(i+1). This allow PCE(i) to
instruct the egress node of domain(i), i.e. BN-ex(i), to forward
packets belonging to this tunnel with the Stitching Label. For
that purpose, PCE(i) should identify the link LK(i+1) by
retrieving from the PKS(i) the corresponding IP address of the
link LK(i+1) for RSVP-TE or from the BGP-LS the label that could
be use to reach link LK(i+1) for Segment Routing. As a result,
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BN-ex(i) installs in its MPLS L(F)IB the SWAP instruction to
label SL(i+1) with forward to LK(i+1). Thus, PCE(i) MUST
complete the ERO(i), in order to provide the Stitching Label
SL(i+1) and Link identifier LK(i+1) to the PCC, as the last hop
of the local path i.e. ERO(i) = {ERO(i), [LK(i+1), SL(i+1)]}.
3. When the PCC BN-en(i) receives the PCInitiate message from its
PCE(i), it sets up the local path from BN-en(i) to BN-ex(i) by
means of RSVP-TE signaling or Segment Routing, accordingly to the
PST value, with the given ERO(i).
4. Once the tunnel is set up, PCC BN-en(i) chooses a free label for
the Stitching Label SL(i) and adds a new entry in its MPLS L(F)IB
with this SL(i) label. Then, it MUST send a PCRpt message to its
PCE(i) including PLSP-ID(i) and a TE-PATH-BINDING TLV with the I
flag set containing a Binding Value equal to SL(i).
5. Once PCE(i) receives the PCRpt from the PCC BN-en(i) with the RRO
PLSP-ID and TE-PATH-BINDING TLV with the I flag set, it MUST send
to the PCE(i-1) a PCRpt containing the TE-PATH-BINDING TLV it
received from the PCC BN-en(i) and the PLSP-ID(i). PCE(i) MAY
add {PKS(i), ..., PKS(n)} in the RRO.
Steps n: Actions performed at the source domain(1) by PCE(1)
Once PCE(1) receives the PCRpt message from PCE(2) with the TE-PATH-
BINDING TLV with the I flag set containing the Binding Value equal to
the Stitching Label SL(2), it MUST send a PCInitiate message to PCC
node S with ERO equal to {ERO(1), [LK(2), SL(2)]}, once retrieves the
identifier of link LK(2), and End-Points Object = {S, BN-ex(1)}. This
time, no TE-PATH-BINDING TLV is provided as the PCC S does not need
to return a Stitching Label SL, because it is the head-end of the
inter-domain path. A usual PCRpt message is sent back to PCE(1) by
the PCC node S.
3.2. Example
In the figure below, two different domains S and D are interconnected
through BN respectively BN-S and BN-D. PE-S and PE-D are edge
routers. All routers in the figure are connected to their respective
PCE through PCEP. In this example, we consider that PCE(S) needs to
set up an inter-domain path between PE-S and PE-D acting as source
and destination of the path. To simplify the figure, neither
intermediate routers between (PE-S, BN-S), (BN-D and PE-D), nor RSVP-
TE messages are represented, but they are all presents. The
following notation is used (in this example, we use the PKS for the
sake of simplicity):
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* PKS(D) = Path Key corresponding to the path from BN(D) to PE-D
* ERO(D) = Explicit Route Object corresponding to the path from
BN(D) to PE-D, retrieved from PKS(D)
* RRO(D) = Record Route Object of the local path(D) from BN(D) to
PE-D
* SL(D) = Stitching Label for the local path from BN(D) to PE-D
* ERO(S) = Explicit Route Object corresponding to the path from PE-S
to BN(S)
* RRO(S) = Record Route Object of local path(S) from PE-S to BN(S)
* TPB(I) = Empty TE-PATH-BINDING TLV with the I flag set
* TPB(I, SL) = TE-PATH-BINDING TLV with Binding Value equal to
Stitching Label SL and the I flag set
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PE-S PCE-S BN-D PCE-D
| | | |
| [ -------- Standard BRPC exchange ------------]
| | | |
| | PCInitiate(ERO={PKS(D)}, TPB(I)
| | --------------------------------------> |
| | | |
| | PCInitiate(ERO = ERO(D), TPB(I))
| | | <------- |
| | | |
| | PCRpt(RRO = {RRO(D)}, TPB(I, SL))
| | | ------> |
| | | |
| PCRpt(RRO = {PKS(D)}, TPB(I, SL), PLSP-ID(D))
| | <-------------------------------------- |
| | | |
| PCInitiate(ERO={ERO(S), LK(D), SL(D), BN(D)}) |
| <------- | | |
| | | |
| PCRpt(RRO={RRO(S)}) | |
| -------> | | |
| | | |
+----------------------+ +----------------------+
| | | |
| +------+ | PCEP | +------+ |
| +---->|PCE(S)|<-------------------------------->|PCE(D)| |
| | +------+ | | +------+ |
| | ^ | | ^ ^ |
| | | | | | | |
| |PCEP | | | | | |
| | |PCEP | | PCEP | | PCEP |
| v | | | | | |
(PE-S) +------> (BN-S) <---------> (BN-D)<----+ +----> (PE-D)
| | Inter-Domain | |
| Domain (S) | Link | Domain (D) |
+----------------------+ +----------------------+
[--- LSP Tunnel (S) ---][---- SL label ----][--- LSP Tunnel (D) ---]
Figure 4: Example of inter-domain path setup between two domains
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3.3. Completion Failure of Inter-domain Path Setup Procedure
In case of error during path setup, PCRpt and or PCErr messages MUST
be used to signal the problem to the neighbor PCE domain backward.
In particular, if the new I flag of the TE-PATH-BINDING TLV defined
in this document is not supported by the neighbor PCE or PCC, the
PCE, respectively PCC, MUST return a PCErr message with Error-Type =
"Binding label/SID failure" and Error-Value = "Unable to allocate a
new binding label/SID" (as per section #12 of draft Binding Label /
Segment Identifier (BSID) [I-D.ietf-pce-binding-label-sid]) to its
neighbor PCE respectively PCE.
If a PCE(i) receives a PCInitiate message from its peer PCE(i-1)
without an TE-PATH-BINDING with the I flag set in the LSP object, it
MUST return a PCErr message with Error-Type = 24 (LSP instantiation
error) and Error-Value = 1 (Unacceptable instantiation parameters) to
its peer PCE(i-1).
Following a PCInitiate message with an LSP object containing an empty
TE-PATH-BINDING TLV with the I flag set, if a neighbor PCE(i+1) or a
PCC returns no TE-PATH-BINDING TLV, or a TE-PATH-BINDING TLV without
the I flag set, the PCE(i), respectively the PCE(i), MUST return a
PCErr message with Error-Type = "Binding label/SID failure" and
Error-Value = "Unable to allocate a new binding label/SID".
In case of completion failure, the PCE(i) MUST propagate the PCErr
message up to the PCE(1). In turn, PCE(1) MUST send a PCInitate
message (R flag set in the SRP Object as per [RFC8281]) to tear down
this inter-domain path from its neighbor PCEs. PCE(i) MUST propagate
the PCInitiate message and remove its local path by means of
PCInitiate message to its PCC BN-en(i) and send back PCRpt message to
PCE(i-1).
In case of error in domain(i+1), PCE(i) MAY add the AS number of
domain(i+1) in the RRO to identify the faulty domain.
4. Hierarchical PCInitiate Procedure
This section describes how to set up inter-domain paths that cross
different domains by using a hierarchical method. It is compatible
with inter-domain path computation as described in [RFC6805].
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4.1. Mode of Operation
This section describes how PCInitiate and PCRpt messages are combined
between PCEs in order to set up inter-domain paths between a source
domain(1) to a destination domain(n). S and D are respectively the
source and destination of the inter-domain path. Domain(1) and
domain(n) are different and connected through 0 or more intermediate
domains denoted domain(i) with i = (2, n-1). Domains are directly
connected when n = 2.
First, the Parent PCE contacts its Child PCE as per [RFC6805] in
order to compute the inter-domain path from S to D, where S and D are
respectively a node in the domain(1) and domain(n). Path Key
confidentiality as per RFC5520 [RFC5520] SHOULD be used to obfuscate
the detailed ERO(i) of the different domains(i). The resulting ERO
is of the form (S, PKS(1), BN-ex(1), ..., BN-en(i), PKS(i), BN-ex(i),
..., BN-en(n), PKS(n), D) when Path Key is used and of the form {S,
R(1,1), ..., R(1,k), BN-ex(1), ..., BN-en(i), R(i,1), ..., R(i,l),
BN-ex(i), ..., BN-en(n), R(n,1), ..., R(n,m), D} otherwise.
The complete procedure with Path Key follow the different steps
described below:
Step 1: Initialization
1. The Parent PCE MUST send a PCInitiate message to Child PCE(n)
with an ERO = {PKS(n)} an LSP containing an empty TE-PATH-BINDING
TLV with the I flag set and End-Points = {BN-en(n), D}. Then,
PCE(n) retrieves the ERO from the PKS(n), if necessary, and MUST
send to BN-en(n) a PCInitiate message with the ERO(n) = {BN-
en(n), ..., D}, an LSP Object with empty TE-PATH-BINDING TLV with
the I flag set and End-Points Object = {BN-en(n), D} in order to
inform the PCC BN-en(n) that this local path(n) is part of an
inter-domain path and that it MUST allocate a Binding Value for
this path.
2. When the PCC BN-en(n) receives the PCInitiate message from its
PCE(n), it sets up the local path from the entry BN-en(n) to D by
means of RSVP-TE signaling or Segment Routing, accordingly to the
PST value, with the given ERO(n).
3. Once the path is set up, it chooses a free label for the
Stitching Label SL(n) and adds a new entry in its MPLS L(F)IB
with this SL(n) label. Then, it MUST send a PCRpt message to its
PCE(n) with PLSP-ID(n) and a TE-PATH-BINDING TLV with the I flag
set and a Binding Value equal to SL(n).
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4. Once PCE(n) receives the PCRpt from the PCC BN-en(n) with the
RRO, PLSP-ID and TE-PATH-BINDING TLV with the I flag set, it MUST
send to its Parent PCE a PCRpt containing the TE-PATH-BINDING TLV
it received from the PCC BN-en(n) and PLSP-ID(n). PCE(n) MAY add
PKS(n) in the RRO.
Steps i: Actions performed for all intermediate domains(i), for i =
n-1 to 2
1. Once the Parent PCE receives a PcRpt from Child PCE(i+1), it MUST
send a PCInitiate message to Child PCE(i) with an LSP object
containing an empty TE-PATH-BINDING TLV with the I flag set, the
ERO(i) to which it appends the SL(i+1) i.e. ERO(i) = {PKS(i),
SL(i+1)} and End-Points = {BN-en(i), BN-ex(i)}.
2. When PCE(i) receives a PcInitiate message from its Parent PCE, it
retrieves the detailed ERO(i) from the PKS(i) if necessary.
Then, it MUST send to the PCC BN-en(i) a PCInitiate message with
an LSP object containing an empty TE-PATH-BINDIG TLV with the I
flag set, this ERO(i) and End-Points Object = {BN-en(i), BN-
ex(i)} in order to inform the PCC BN-en(i) that this local
path(i) is part of an inter-domain path and that it MUST allocate
a Binding Value for this path. PCE(i) sets Path Setup Type (PST)
to 0, respectively to 1 to instruct the PCC to enforce the local
path by means of RSVP-TE respectively Segment Routing.
3. Egress Control mechanism, as per RFC4003 section 2.1 [RFC4003]
for RSVP-TE, respectively, Egress Peer Engineering [RFC9086] for
Segment Routing, is used to stitch and steer traffic between the
border node BN-ex(i) and BN-en(i+1). This allow PCE(i) to
instruct the egress node of domain(i), i.e. BN-ex(i), to forward
packets belonging to this tunnel with the Stitching Label. For
that purpose, PCE(i) should identify the link LK(i+1) by
retrieving from the PKS(i) the corresponding IP address of the
link LK(i+1) for RSVP-TE or from the BGP-LS the label that could
be use to reach link LK(i+1) for Segment Routing. As a result,
BN-ex(i) installs in its MPLS L(F)IB the SWAP instruction to
label SL(i+1) with forward to LK(i+1). Thus, PCE(i) MUST
complete the ERO(i), in order to provide the Stitching Label
SL(i+1) and Link identifier LK(i+1) to the PCC, as the last hop
of the local path i.e. ERO(i) = {ERO(i), [LK(i+1), SL(i+1)]}.
4. When the PCC BN-en(i) receives the PCInitiate message from its
PCE(i), it sets up the local path from BN-en(i) to BN-ex(i) by
means of RSVP-TE signaling or Segment Routing, accordingly to the
PST value, with the given ERO(i).
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5. Once the tunnel is set up, PCC BN-en(i) chooses a free label for
the Stitching Label SL(i) and adds a new entry in its MPLS L(F)IB
with this SL(i) label. Then, it MUST send a PCRpt message to its
PCE(i) with PLSP-ID(i) and a TE-PATH-BINDING TLV with I flag set
and a Binding Value equal to SL(i).
6. Once PCE(i) receives the PCRpt from the PCC BN-en(i) with the
RRO, PLSP-ID and TE-PATH-BINDING TLV with the I flag set, it MUST
send to its Parent PCE a PCRpt containing the TE-PATH-BINDING TLV
it received from the PCC BN-en(i) and the PLSP-ID(i). PCE(i) MAY
add {PKS(i), ..., PKS(n)} in the RRO.
7. Once the Parent PCE receives the PCRpt from the Child PCE(i), it
stores the corresponding PLSP-ID for this inter-domain path part.
Steps n: Actions performed to the source domain(1)
Finally, the Parent PCE MUST send a last PCInitiate message to its
Child PCE(1) with an LSP Object containing an empty TE-PATH-BINDING
TLV with the I flag set, ERO = {PKS(1), SL(2)} and End-Points = {S,
BN-ex(1)}. In turn, Child PCE(1) MUST send a PCInitiate message to
PCC node S with ERO equal to {ERO(1), [LK(2), SL(2)]} and End-Points
Object = {S, BN-ex(1)}. This time, no TE-PATH-BINDING TLV is provided
as the PCC S does not need to return a Stitching Label SL, because it
is the head-end of the inter-domain path. A usual PCRpt message is
sent back to PCE(1) by the PCC node S. In turn, Child PCE(1) sends a
final PCRpt message to the Parent PCE with the PSLP-ID(1). PCE(1)
MAY add {S, BN-ex(1)} in the RRO.
4.2. Completion Failure of Inter-domain Path Setup Procedure
In case of error during path set up, PCRpt and/or PCErr messages MUST
be used to signal the problem to the Parent PCE. In particular, if
the new I flag of the TE-PATH-BINDING TLV defined in this document is
not supported by the Child PCE or the PCC, the Child PCE,
respectively the PCC, MUST return a PCErr message with Error-Type =
"Binding label/SID failure" and Error-Value = "Unable to allocate a
new binding label/SID" (as per section #12 of draft Binding Label /
Segment Identifier (BSID) [I-D.ietf-pce-binding-label-sid]) to its
Parent PCE respectively PCE.
If a PCE(i) receives a PCInitiate message from its Parent PCE without
an TE-PATH-BINDING with the I flag set in the LSP, it MUST return a
PCErr message with Error-Type = 24 (LSP instantiation error) and
Error-Value = 1 (Unacceptable instantiation parameters) to its Parent
PCE.
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Following a PCInitiate message with an LSP containing an empty TE-
PATH-BINDING TLV with the I flag set, if a Child PCE or a PCC returns
no TE-PATH-BINDING TLV, or a TE-PATH-BINDING TLV without the I flag
set, the Parent PCE, respectively the Child PCE, MUST return a PCErr
message with Error-Type = "Binding label/SID failure" and Error-Value
= "Unable to allocate a new binding label/SID".
In case of completion failure, the Parent PCE MUST send a PCInitate
message (R flag set in the SRP Object as per [RFC8281]) to tear down
this inter-domain path from the Child PCEs that already set up their
respective part of the inter-domain path. Child PCE(i) MUST remove
its local path by means of PCInitiate message with R flag set to 1 to
its PCC BN-en(i) and send back a PCRpt message to the Parent PCE.
In case of error during path setup, PCRpt and or PCErr messages MUST
be used to signal the problem to the neighbor PCE domain backward.
4.3. Example for Stateful H-PCE Stiching Procedure
Taking the sample hierarchical domain topology example from [RFC6805]
as the reference topology for the entirety of this section.
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-----------------------------------------------------------------
| Domain 5 |
| ------- |
| |P-PCE 5| |
| ------- |
| |
| ---------------- ---------------- ---------------- |
| | Domain 1 | | Domain 2 | | Domain 3 | |
| | | | | | | |
| | ------- | | ------- | | ------- | |
| | |C-PCE 1| | | |C-PCE 2| | | |C-PCE 3| | |
| | ------- | | ------- | | ------- | |
| | | | | | | |
| | ----| |---- ----| |---- | |
| | |BN11+---+BN21| |BN23+---+BN31| | |
| | - ----| |---- ----| |---- - | |
| | |S| | | | | |D| | |
| | - ----| |---- ----| |---- - | |
| | |BN12+---+BN22| |BN24+---+BN32| | |
| | ----| |---- ----| |---- | |
| | | | | | | |
| | ---- | | | | ---- | |
| | |BN13| | | | | |BN33| | |
| -----------+---- ---------------- ----+----------- |
| \ / |
| \ ---------------- / |
| \ | | / |
| \ |---- ----| / |
| ----+BN41| |BN42+---- |
| |---- ----| |
| | | |
| | ------- | |
| | |C-PCE 4| | |
| | ------- | |
| | | |
| | Domain 4 | |
| ---------------- |
| |
-----------------------------------------------------------------
Figure 5: Hierarchical domain topology from RFC6805
Section 3.3.1 of [RFC8751] describes the per-domain stitched LSP mode
and list all the steps needed. To support SL-based stitching, using
the reference architecture described in the figure above, the steps
are modified as follows (note that we do not use PKS in this example
for simplicity):
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Step 1: initialization
The P-PCE (PCE5) is requested to initiate a path. Steps 4 to 10 of
section 4.6.2 of [RFC6805] are executed to determine the end-to-end
path, which are split into per-domain paths, e.g. {S-BN41,
BN41-BN33, BN33-D}.
Step 2: Path (BN33-D) at C-PCE3:
1. The P-PCE (P-PCE5) sends the initiate request to the C-PCE
(C-PCE3) via PCInitiate message for path (BN33-D) with
ERO={BN33..D} and an LSP object containing an empty TE-PATH-
BINDING TLV with the I flag set and PST = 0/1 based on the setup
type.
2. C-PCE3 further propagates the initiate message it receives from
P-PCE to BN33.
3. BN33 initiates the setup of the path and reports to the status
("GOING-UP") to C-PCE3.
4. C-PCE3 further reports the status of the path to the P-PCE
(P-PCE5)
5. The node BN33 notifies the path state to C-PCE3 when the state is
"UP"; it also sends the Stitching Label (SL33) as the Binding
Value of the TE-PATH-BINDING TLV with the I flag set and the RRO
through the PCRpt message.
6. C-PCE3 further reports the PCRpt message it receives from BN33 to
the P-PCE (P-PCE5).
Step 3: Path (BN41-BN33) at C-PCE4
1. The P-PCE (P-PCE5) sends the initiate request to the C-PCE
(C-PCE4) via PCInitiate message for path (BN41-BN33) with
ERO={BN41..BN42,SL33,BN33} and an LSP object containing an empty
TE-PATH-BINDING TLV with the I flag set and PST = 0/1 based on
the setup type.
2. C-PCE4 further propagates the initiate message it receives from
P-PCE to BN41 once complete the the ERO with the Link Identifier
LK33 i.e. ERO={BN41..BN42,LK33,SL33,BN33}.
3. BN41 initiates the setup of the path and reports the path status
("GOING-UP") to C-PCE4.
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4. C-PCE4 further reports the status of the path to the P-PCE
(P-PCE5).
5. The node BN41 notifies the path state to C-PCE4 when the state is
"UP"; it also sends the Stitching Label (SL41) as the Binding
Value of the TE-PATH-BINDING TLV with the I flag set and the RRO
through the PCRpt message.
6. C-PCE4 further reports the PCRpt message it receives from BN41 to
the P-PCE (P-PCE5).
Step 3: Path (S-BN41) at C-PCE1
1. The P-PCE (P-PCE5) sends the initiate request to the C-PCE
(C-PCE1) via PCInitiate message for path (S-BN41) with
ERO={S..BN13,SL41,BN41} and an LSP object containing an empty TE-
PATH-BINDING TLV with the I flag set and PST = 0/1 based on the
setup type.
2. C-PCE1 further propagates the initiate message it receives from
P-PCE to node S once complete the the ERO with the Link
Identifier LK41 i.e. ERO={S..BN13,LK41,SL41,BN41}.
3. S initiates the setup of the path and reports the path status
("GOING-UP") to C-PCE1.
4. C-PCE1 further reports the status of the path to the P-PCE
(P-PCE5)
5. The node S notifies the path state to C-PCE1 when the state is
"UP".
6. C-PCE1 further reports the PCRpt message it receives from node S
to the P-PCE (P-PCE5).
5. Inter-domain Path Management
This section describes how inter-domain paths could be managed.
5.1. Stitching Label PCE Capabilities
A PCE needs to know if its neighbor PCEs as well as PCCs are able to
configure and provide a Stitching Label. The STITCHING-LABEL-PCE-
CAPABILITY TLV is an optional TLV for use in the OPEN object for
Stitching Label PCE capability advertisement. Its format is shown in
the following figure:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD7 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |I|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: STITCHING-LABEL-PCE-CAPABILITY TLV Format
The Type (16 bits) of the TLV is TBD7. The Length field is 16 bits
long and has a fixed value of 4.
The value comprises a single 32 bits "Flags" field:
I (INTER-DOMAIN-STITCHING-LABEL-CAPABILITY - 1 bit): if set to 1 by a
PCE, the I flag indicates that the domain is supporting Stitching
Label to set up inter-domain paths. When set by a PCC, the I flag
indicates the the PCC is able to provide a Stitching Label as value
of TE-PATH-BINDING TLV.
Unassigned bits are considered reserved. They MUST be set to 0 on
transmission and MUST be ignored on receipt.
PCC MUST set the I flag when adding the Stitching Label Capability to
the PCEP Open Message when establishing a PCEP session with a PCE.
A PCE MUST set the I flag when establishing a PCEP session with a
neighbor PCE when adding Stitching Label Capability to the PCEP Open
Message.
5.2. Identification of Inter-domain Paths
First, in order to manage inter-domain paths composed by the
stitching or nesting of local paths, it is important to identify
them. For this purpose, the PLSP-ID managed by the PCEs are combined
to one provided by PCCs to form a global identifier as follow:
* PCE(i) in the Backward Recursive method or the Child PCE in
Hierarchical method MUST create a new unique PLSP-ID for this
inter-domain path part and MUST send it in the PCRpt message, to
the PCE(i-1), respectively the Parent PCE. In addition this new
PLSP-ID MUST be associated to the one received from the PCC that
instantiates the local path part for further reference.
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* In the Hierarchical mode, the Parent PCE MUST store and associate
the different PLSP-ID(i)s received from the different Child
PCE(i)s in order to identify the different part of the inter-
domain paths.
* In the Backward Recursive method, PCE(i) MUST store and associate
its PLSP-ID(i) and the PLSP-ID(i+1) it received from the PCE(i+1).
PCE(n), i.e. the last one in the chain, does not need to perform
such association.
Further reference to the inter-domain path will use this PLSP-ID(i).
In the Backward Recursive method, PCE(i) MUST replace the PLSP-ID(i)
by PLSP-ID(i+1) in the PCUpd, PCRpt or PCinitiate message before
propagating it to PCE(i+1); and PCE(i) MUST replace the PLSP-ID(i+1)
by PLSP-ID(i) in the PCRpt message before propagating it to the
PCE(i-1). In the Hierarchical method, the Parent PCE MUST use the
corresponding PLSP-ID(i) of the Child PCE(i).
5.3. Inter-domain Association Group
In case of failure, a PCE(i) will received PCRpt messages from its
PCCs and neighbors PCE(i+1) to synchronize the Inter-domain paths.
In addition, it may received PCInitiate messages from its previous
neighbors PCE(i-1) to re-initiate its inter-domain path part. As the
PCE(i) may loose the PLSP-ID association, a new association group
(within Association Object) is used to ease the association of the
different parts of the inter-domain path: the local part and the PCE-
to-PCE part. The use of the Association Object is MANDATORY in the
Backward Recursive method and OPTIONAL in the Hierarchical method.
For that purpose, a new Inter-Domain Association Type with value TBD4
is defined. The first PCE in the Backward Recursive chain (the one
which received the initial request) MUST send the PCInitiate message
with an Association Object as follows:
* Association Type field MUST be set to new value TBD4
* Association ID MUST be set to a unique value. In case the
Association ID field is too short or wraps, the first PCE MAY use
the Extended Association ID to increase the number of association
groups. The Association ID is managed locally by the PCE and does
not need to be coordinated with neighbor or remote PCEs.
* IPV4 or IPv6 association source MUST be set to the IP address
which identifies PCE(1) in domain(1).
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* The Global Association Source TLV MUST be present and set with the
ASN number of domain(1). It allows to create a globally unique
association scope without putting constraint on operator's IP
association source. Thus the IP Association Source is associated
with the Global Association source to form a unique identifier.
* Extended Association ID MAY be present and MANDATORY if
association ID is too short or wraps.
Subsequent PCE(i), for i = 2 to n, MUST send this Association Object
as is to the local PCC and the neighbor PCE(i+1).
In case of error with the association group, a PCErr message MUST be
raised with Error = 26 (Association Error) and Error value set
accordingly. A new Error value TBD6 is defined to identify
association of inter-domain paths.
In the Hierarchical method, the Parent PCE MAY act as the initiator
of the Association and send to the Child PCEs an Association Object
that follows the same rules as for the Backward Recursive method. In
turn, Child PCEs MUST propagate the Association Object to the local
PCCs as is.
5.4. Modification of Inter-domain Paths
For the Backward Recursive method, each domain manages their
respective local path of an inter-domain path independently of each
other. In particular, Stitching Label(i) is managed by domain(i) and
is of interest of domain(i-1) only. Thus, Stitching Label SL(i) is
not supposed to be propagated to other domains. The same behavior
apply to PLSP-ID(i). In the Hierarchical method, the Parent PCE MUST
ensure the correct distribution of Stitching Label SL(i) to Child
PCE(i-1). The PLSP-ID(i) is kept for the usage of the Parent PCE and
thus is not propagated. Only the Association Object defined in
section 5.2 is propagated if it is present.
If PCE(i) needs to modify its local path(i) with a PCUpd message to
the PCC BN-en(i), once the PCRpt message received from the PCC BN-
en(i), it MUST sends a new PCRpt message to advertise the
modification. This message is targeted to its neighbor PCE(i-1) in
the Backward Recursive method, respectively to the Parent PCE in the
Hierarchical method. In this case PLSP-ID(i) is used to identify the
inter-domain path. PCE(i-1), respectively the Parent PCE, MUST
propagate the PCRpt message if the modification implies the upstream
domain, e.g. if the PCRpt indicates that the Stitching Label SL(i)
has changed.
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PCE(1), respectively the Parent PCE, could modify the inter-domain
path. For that purpose, it MUST send a PCUpd message to its neighbor
PCEs, respectively Child PCE, using the PLSP-ID it received. Each
PCE(i) MUST process the PCUpd message the same way they process the
PCInitiate message as define in section 3.1 for the Backward
Recursive method and in section 4.1 for the Hierarchical method.
In case a failure appear in domain(i), e.g. path becoming down,
PCE(i) MUST sends a PCRpt message to its neighbor PCE(i-1),
respectively its Parent PCE to advertise the problem in its local
part of the inter-domain path. Once PCE(1), respectively the Parent
PCE, receives this PCRpt message indicating that the path is down, it
is up to the PCE(1), respectively the Parent PCE to take appropriate
correction e.g. start a new path computation to update the ERO.
5.5. Modification of Local Paths
The modification of local paths, i.e. between BN-en(i) and BN-ex(i),
is also left to the discretion of PCE(i). More precisely, if the
PCE(i) wishes to modify the local part of the inter-domain path, it
MUST send a standard PcUpd message and wait to receive the
corresponding PcRpt message. The PCE(i) MUST propagate the PcUpd
message to the PCE(i-1) if and only if the modification of the local
part of the interdomain path affects the domain(i-1), i.e. if the
Stitching Label is modified or if the modification failed and the
local path goes down.
However, PCE(i) MUST NOT modify the BN-ex(i-1), BN-en(i), BN-ex(i)
and BN-en(i+1) as the interdomain path is only delegated to the
PCE(i) and is not initiated by the PCE(i). Only PCE(1) is able to
modify the BN-en(1.. n) and BN-ex(1 .. n) by triggering a new inter-
domain path computation using the Backward Recursive or the
Hierarchical method. Once the new inter-domain path is computed
according to step 1 of section 3 respectively 4, the instantiation of
the inter-domain path follows the same steps by replacing the PcInit
messages with PcUpd messages.
5.6. Tear-Down of Inter-domain Paths
The tear-down of an inter-domain path is only possible by the inter-
domain path initiator i.e. PCE(1). For the Backward Recursive
method, a PCInitiate message with R flag set to 1, PLSP-ID set
accordingly to section 5.1 and the Association Object with R flag set
to 1, is sent by PCE(1) to PCE(n) through PCE(i), and processed the
same way as described in section 3.1. For the Hierarchical method, a
PCInitiate message with R flag set to 1 is sent by the Parent PCE to
each Child PCE(i) with corresponding PLSP-ID(i), and processed
according to section 4.1. Each domain PCE(i) is responsible to tear
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down its part of the path and the PCC MUST release both the Stitching
label SL(i) in its L(F)IB and the path when it receives the
PCInitiate message with the R flag set to 1 and the corresponding
PLSP-ID(i). The Association Group MUST also be removed by the PCC
and PCE(i).
6. Applicability
The newly introduce Stitching Label SL serves to stitch or nest part
of local paths to form an inter-domain path. Each domain is free to
decide if the incoming path is stitched or nested and how the path is
enforced, e.g. through RSVP-TE or Segment Routing. At the peering
point, the Border Node BN-ex(i) MUST encapsulate the packet with the
Stitching Label, i.e. the MPLS label prior to send them to the next
Border Node BN-en(i+1). Thus, only IP/MPLS networks are supported by
this specification.
6.1. Mixing Technologies
During the instantiation procedure, if PCE(i) decides to reuse a
local tunnel which is not yet part of an inter-domain tunnel, it
SHOULD send a PCUpd message with an LSP containing an empty TE-PATH-
BINDING TLV with the I flag set to 1 to the PCC BN-en(i), in order to
request a Stitching Label SL(i), and new ERO(i) to add the Stitching
Label SL(i+1) and the associated link to the previous ERO.
[RFC8453] describes framework for Abstraction and Control of TE
Networks (ACTN), where each Physical Network Controller (PNC) is
equivalent to C-PCE and the Multi-Domain Service Coordinator (MDSC)
to the P-PCE. The per-domain stitched LSP as per the Hierarchical
PCE architecture described in Section 3.3.1 and Section 4.1 of
[RFC8751] is well suited for ACTN. The Stitching Label mechanism as
described in this document is well suited for ACTN when per-domain
LSPs need to be stitched to form an E2E tunnel or a VN Member. It is
to be noted that certain VNs require isolation from other clients.
The SL mechanism described in this document can be applicable to the
VN isolation use-case by uniquely identifying the concatenated
stitching labels across multi-domain only to a certain VN member or
an E2E tunnel.
As each operator is free to enforce the tunnel with its technology
choice, it is a local policy decision for PCE(i) to instantiate the
local part of the end-to-end tunnel by either RSVP-TE or Segment
Routing. The PST value 0 or 1 used in the PCinitiate message sent by
the PCE(i) to the local PCC is determined by the local policy. How
the local policy decision is set in the PCE is out of the scope of
this document. This flexibility is allowed because the SL principle
allows to mix (data plane) technologies between domains. For
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example, a domain(i) could use RSVP-TE while domain(i+1) uses SR.
The SL could serve to stitch indifferently Segment Paths and RSVP-TE
tunnels. Indeed, the SL will be part of the label stack in order to
become the top label in the stack when reaching the BN-en(i+1). This
SL could be swapped as usual if the next domain uses RSVP-TE tunnels.
When the upstream domain uses an RSVP-TE tunnel, the SL will serve as
a key for the BN-en(i+1) to determine which label stack it must use
on top of the packet for a Segment Routing path. Finally, PCE(i)
MUST completes accordingly ERO(i) with the identifier of Link(i+1):
IP address of link between BN-ex(i) and BN-en(i+1) for RSVP-TE or EPE
label of link between BN-ex(i) and BN-en(i+1) for Segment Routing.
6.2. Inter-Area
If use cases for inter-AS are easily identifiable, this is less
evident for inter-area. However, two scenarios have been identified:
* Paths between levels for IS-IS networks.
* Reduction of labels stack depth for Segment Routing.
Thus, the SL could be used to stitch or nest independent tunnels
deployed through different IS-IS levels, even if there are controlled
by the same PCE. IS-IS levels are considered as domains but under
the control of the same PCE. In this scenario, there is no exchange
between PCEs (it remains internal and implementation matter) and new
TLVs are only applicable between the PCE and PCCs. The PCE requests
to the different PCCs it identifies (i.e. BNs of the different IS-IS
levels) to set up SLs and propagated them.
In large-scale networks, MSD could constraints the path computation
in the possibility of path selection i.e. explicit expression of a
path could exceeded the MSD. The SL could be used to split a too
long explicit path regarding the MSD constraints. In this scenario,
there is also no communications between PCEs and new TLVs are only
used between PCE and PCCs.
6.3. Nested traffic
When a domain(i) would groups into the same local path all traffic
that enter into the domain through the same border node BN-en(i) and
exit by the same border node BN-ex(i), it could be useful to identify
the different inter-domain paths within this local path. Indeed,
traffic entering in this nested local path could goes to different
domains or different destination of the same domain. Thus, it is
mandatory to keep them perfectly identifiable through a dedicated
Stitching Label. In this case, PCE(i) proceeds as if it nested
internal traffic. Nested tunnel MUST be created in top of existing
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inter-domain local path. Subsequent inter-domain local path will
follow this nested local path. As a consequence, PCE(i) MUST NOT
request a second Stitching Label(i) for an existing inter-domain
local path.
6.4. VPN
For VPN use case, inter-domain paths link PEs that spawn in different
domains. Such connectivity could be considered as Seamless MPLS. In
order for the source PE to route L3/L2 VPN packets to the
destination, it must be aware that the next-hop BGP i.e. the
destination PE, is joignable through the appropriate inter-domain
path. For that purpose, the corresponding prefix i.e. the L3/L2 VPN
one, must be exchange with 'next hop unchanged' command to keep
unmodified the IP address of the PE which advertised this VPN prefix.
And, like for inter-domain option C, Route Reflectors could be use to
exchange and advertise between domains the IP addresses of BGP next-
hop i.e. in general the loopback IP address of the PE routers.
6.5. Intent-Based Networking
Intent-Based Networking as per [RFC9315] defines goals and outcomes
that an implementation must respect. The present memo addresses most
of the concepts of Intent-Based Networking and in particular:
* From a service point of view, the inter-domain path computation is
abstracted though by the use of PKS and enforcement technology
i.e. RSVP-TE, SR-TE, over-provisioning ... is done independently
by each domain. The user is therefore is unaware of the details
of the creation, modification, deletion and management of the
inter-domain path,
* AS path computation performed during the initial step allows to
include or exclude some domains allowing geography or geo-
political routing,
* Intra domain path computation done by domain(i) allows to include
or exclude some Border Nodes, internal nodes, internal links ...
based on any policy deployed by domain(i) and independently of the
other domains,
* Traffic usage is controlled by each domains independently while
end-to-end constraints are respected during inter-domain path
computation and enforcement.
In addition, the Backward Recursive method avoids the usage of a
centralize controller and completely distributes the service
instantiation across the involved domains.
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6.6. QoS management
When performing the path computation, the initial request to the
PCE(1) could contains the CLASSTYPE (CT) Object in the list of
constrained parameters. This Class-Type MUST be propagated during
the inter-domain path computation in the Backward Recursive method,
respectively to the Parent PCE in the Hierarchical method and take
into account for Bandwidth Reservation. As per [RFC5455], each
PCE(i) MUST store the Class-Type in order to complete the path
computation, in particular in the Backward Recursive method. In
addition, the Class-Type MAY be used by domain(i) to set the EXP bits
in the MPLS label in order for router to process the packets
accordingly to DiffServ-TE configured in the domain(i). To maintain
the independance, domain(i) is free to implement or not DiffServ-TE
queuing, and if DiffServe-TE queing is implemented, to configre the
different queue parameters with its own traffic engineering rules.
Thus, the proposed mechanism just allows to propagate the EXP bits
without modification. If domain(i) is not able or would not accept
traffic in the specified Class-Type, during the inter-domain path
computation it MUST reply with a NO_PATH Object to domain(i-1) for
the Backward Recursive method, respectively to the Parent PCE in the
Hierarchical method.
In case of Bandwidth Reservation i.e. initial request containts a
Bandwidth Metric Object, domain (i) MAY configure the BN-en(i) of the
inter-domain path to verify and enforce traffic corresponding to the
requested bandwidth with the mechanism domain(i) seems appropriate.
In other words, domain(i) MAY apply its own traffic engineering and
policy rules at the entry of its domain independtly from the other
domains. The detailed configuration of the QoS for the BN-en(i)
router is outside the scope of this draft.
7. IANA Considerations
7.1. TE-PATH-BINDING flag
Binding Label / Segment Identifier (BSID)
[I-D.ietf-pce-binding-label-sid] defines the TE-PATH-BINDING TLV Flag
field. IANA is requested to allocate new flag in the PCEP TE-PATH-
BINDING TLV Flag field registry, as follows:
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+=====+===========================+===========+
| Bit | Description | Reference |
+=====+===========================+===========+
| 1 | I (Inter-domain Binding | This |
| | Label/Segment Identifier) | Document |
+-----+---------------------------+-----------+
| 2 | S (Strictly steer | This |
| | traffic) | Document |
+-----+---------------------------+-----------+
Table 1
7.2. Association Type Value
PCE Association Group [RFC8697] defines the ASSOCIATION Object and
requests that IANA creates a registry to manage the value of the
Association Type value. IANA is requested to allocate a new code
point in the PCEP ASSOCIATION GROUP TLV Association Type field
registry, as follows:
+==================+================================+
| Association Type | Description |
+==================+================================+
| TBD1 | Inter-domain Association Group |
+------------------+--------------------------------+
Table 2
7.3. PCEP Error Values
IANA is requested to allocate code-points in the PCEP-ERROR Object
Error Values registry for a new error-value of Error-Type 6 Mandatory
Object Missing Error and new error-value of Error-Type 26 Association
Error:
+============+=============+=================================+
| Error-Type | Error-Value | Description |
+============+=============+=================================+
| 6 | TBD2 | LSP TE-PATH-BINDING missing TLV |
+------------+-------------+---------------------------------+
| 26 | TBD3 | Error in association of Inter- |
| | | domain LSPs |
+------------+-------------+---------------------------------+
Table 3
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7.4. PCEP TLV Type Indicators
IANA is requested to allocate a new TLV Type Indicator for the
"Stitching Label PCE Capability" within the "PCEP TLV Type
Indicators" sub-registry of the "Path Computation Element Protocol
(PCEP) Numbers" registry:
+=======+================================+===============+
| Value | Description | Reference |
+=======+================================+===============+
| TBD4 | STITCHING-LABEL-PCE-CAPABILITY | This Document |
+-------+--------------------------------+---------------+
Table 4
7.5. Stitching Label PCE Capability
IANA is requested to allocate a new sub-registry, named "STITCHING-
LABEL-PCE-CAPABILITY TLV Flag Field", within the "Path Computation
Element Protocol (PCEP) Numbers" registry, to manage the Flag field
in the STITCHING-LABEL-PCE-CAPABILITY TLV of the PCEP OPEN object
(class = 1). New values are assigned by Standards Action [RFC8126].
Each bit should be tracked with the following qualities:
* Bit number (counting from bit 0 as the most significant bit)
* Capability description
* Defining RFC
+=======+===================================+===============+
| Value | Description | Reference |
+=======+===================================+===============+
| 31 | INTER-DOMAIN-STITCHING-CAPABILITY | This Document |
+-------+-----------------------------------+---------------+
Table 5
8. Security Considerations
No modification of PCE protocol (PCEP) has been requested by this
draft which does not introduce any issue regarding security.
Concerning the PCEP session between PCEs, authors recommend to use
the secured version of PCEP as defined in PCEPS [RFC8253] or use any
other secured tunnel mechanism, e.g. IPsec tunnel to transport PCEP
session between PCEs.
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9. Acknowledgements
The authors want to thanks PCE's WG members, and in particular Dhruv
Dhody who greatly contributed to the Hierarchical section of this
document and Quan Xiong for his advice.
10. Disclaimer
This work has been performed in the framework of the H2020-ICT-2014
project 5GEx (Grant Agreement no. 671636), which is partially funded
by the European Commission. This information reflects the
consortium's view, but neither the consortium nor the European
Commission are liable for any use that may be done of the information
contained therein.
11. References
11.1. Normative References
[I-D.ietf-pce-binding-label-sid]
Sivabalan, S., Filsfils, C., Tantsura, J., Previdi, S.,
and C. Li, "Carrying Binding Label/Segment Identifier
(SID) in PCE-based Networks.", Work in Progress, Internet-
Draft, draft-ietf-pce-binding-label-sid-16, 27 March 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-pce-
binding-label-sid-16>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>.
[RFC5441] Vasseur, JP., Ed., Zhang, R., Bitar, N., and JL. Le Roux,
"A Backward-Recursive PCE-Based Computation (BRPC)
Procedure to Compute Shortest Constrained Inter-Domain
Traffic Engineering Label Switched Paths", RFC 5441,
DOI 10.17487/RFC5441, April 2009,
<https://www.rfc-editor.org/info/rfc5441>.
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[RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for Stateful PCE", RFC 8231,
DOI 10.17487/RFC8231, September 2017,
<https://www.rfc-editor.org/info/rfc8231>.
[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, DOI 10.17487/RFC8281, December 2017,
<https://www.rfc-editor.org/info/rfc8281>.
[RFC8697] Minei, I., Crabbe, E., Sivabalan, S., Ananthakrishnan, H.,
Dhody, D., and Y. Tanaka, "Path Computation Element
Communication Protocol (PCEP) Extensions for Establishing
Relationships between Sets of Label Switched Paths
(LSPs)", RFC 8697, DOI 10.17487/RFC8697, January 2020,
<https://www.rfc-editor.org/info/rfc8697>.
11.2. Informative References
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<https://www.rfc-editor.org/info/rfc3209>.
[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
DOI 10.17487/RFC3473, January 2003,
<https://www.rfc-editor.org/info/rfc3473>.
[RFC4003] Berger, L., "GMPLS Signaling Procedure for Egress
Control", RFC 4003, DOI 10.17487/RFC4003, February 2005,
<https://www.rfc-editor.org/info/rfc4003>.
[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,
<https://www.rfc-editor.org/info/rfc4206>.
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<https://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,
<https://www.rfc-editor.org/info/rfc5150>.
[RFC5455] Sivabalan, S., Ed., Parker, J., Boutros, S., and K.
Kumaki, "Diffserv-Aware Class-Type Object for the Path
Computation Element Communication Protocol", RFC 5455,
DOI 10.17487/RFC5455, March 2009,
<https://www.rfc-editor.org/info/rfc5455>.
[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,
<https://www.rfc-editor.org/info/rfc5520>.
[RFC6805] King, D., Ed. and A. Farrel, Ed., "The Application of the
Path Computation Element Architecture to the Determination
of a Sequence of Domains in MPLS and GMPLS", RFC 6805,
DOI 10.17487/RFC6805, November 2012,
<https://www.rfc-editor.org/info/rfc6805>.
[RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
"PCEPS: Usage of TLS to Provide a Secure Transport for the
Path Computation Element Communication Protocol (PCEP)",
RFC 8253, DOI 10.17487/RFC8253, October 2017,
<https://www.rfc-editor.org/info/rfc8253>.
[RFC8453] Ceccarelli, D., Ed. and Y. Lee, Ed., "Framework for
Abstraction and Control of TE Networks (ACTN)", RFC 8453,
DOI 10.17487/RFC8453, August 2018,
<https://www.rfc-editor.org/info/rfc8453>.
[RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "Path Computation Element Communication
Protocol (PCEP) Extensions for Segment Routing", RFC 8664,
DOI 10.17487/RFC8664, December 2019,
<https://www.rfc-editor.org/info/rfc8664>.
[RFC8751] Dhody, D., Lee, Y., Ceccarelli, D., Shin, J., and D. King,
"Hierarchical Stateful Path Computation Element (PCE)",
RFC 8751, DOI 10.17487/RFC8751, March 2020,
<https://www.rfc-editor.org/info/rfc8751>.
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[RFC9086] Previdi, S., Talaulikar, K., Ed., Filsfils, C., Patel, K.,
Ray, S., and J. Dong, "Border Gateway Protocol - Link
State (BGP-LS) Extensions for Segment Routing BGP Egress
Peer Engineering", RFC 9086, DOI 10.17487/RFC9086, August
2021, <https://www.rfc-editor.org/info/rfc9086>.
[RFC9315] Clemm, A., Ciavaglia, L., Granville, L. Z., and J.
Tantsura, "Intent-Based Networking - Concepts and
Definitions", RFC 9315, DOI 10.17487/RFC9315, October
2022, <https://www.rfc-editor.org/info/rfc9315>.
Authors' Addresses
Olivier Dugeon
Orange Labs
2, Avenue Pierre Marzin
22307 Lannion
France
Email: olivier.dugeon@orange.com
Julien Meuric
Orange Labs
2, Avenue Pierre Marzin
22307 Lannion
France
Email: julien.meuric@orange.com
Young Lee
Samsung Electronics
Email: younglee.tx@gmail.com
Daniele Ceccarelli
Cisco System
Torshamnsgatan, 48
Stockholm
Sweden
Email: daniele.ietf@gmail.com
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