PCE Working Group Q. Zhao
Internet-Draft Z. Li
Intended status: Standards Track M. Negi
Expires: September 9, 2020 S. Peng
Huawei Technologies
C. Zhou
Cisco Systems
March 8, 2020
PCEP Procedures and Protocol Extensions for Using PCE as a Central
Controller (PCECC) of LSPs
draft-ietf-pce-pcep-extension-for-pce-controller-04
Abstract
The Path Computation Element (PCE) is a core component of Software-
Defined Networking (SDN) systems. It can compute optimal paths for
traffic across a network and can also update the paths to reflect
changes in the network or traffic demands.
PCE was developed to derive paths for MPLS Label Switched Paths
(LSPs), which are supplied to the head end of the LSP using the Path
Computation Element Communication Protocol (PCEP). But SDN has a
broader applicability than signaled (G)MPLS traffic-engineered (TE)
networks, and the PCE may be used to determine paths in a range of
use cases. PCEP has been proposed as a control protocol for use in
these environments to allow the PCE to be fully enabled as a central
controller.
A PCE-based central controller (PCECC) can simplify the processing of
a distributed control plane by blending it with elements of SDN and
without necessarily completely replacing it. Thus, the LSP can be
calculated/setup/initiated and the label forwarding entries can also
be downloaded through a centralized PCE server to each network
devices along the path while leveraging the existing PCE technologies
as much as possible.
This document specifies the procedures and PCEP protocol extensions
for using the PCE as the central controller.
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
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working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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 September 9, 2020.
Copyright Notice
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Basic PCECC Mode . . . . . . . . . . . . . . . . . . . . . . 5
4. PCEP Requirements . . . . . . . . . . . . . . . . . . . . . . 5
5. Procedures for Using the PCE as the Central Controller
(PCECC) . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Stateful PCE Model . . . . . . . . . . . . . . . . . . . 6
5.2. New LSP Functions . . . . . . . . . . . . . . . . . . . . 6
5.3. New PCEP Object . . . . . . . . . . . . . . . . . . . . . 7
5.4. PCECC Capability Advertisement . . . . . . . . . . . . . 7
5.5. LSP Operations . . . . . . . . . . . . . . . . . . . . . 8
5.5.1. Basic PCECC LSP Setup . . . . . . . . . . . . . . . . 8
5.5.2. Central Control Instructions . . . . . . . . . . . . 12
5.5.2.1. Label Download CCI . . . . . . . . . . . . . . . 12
5.5.2.2. Label Cleanup CCI . . . . . . . . . . . . . . . . 12
5.5.3. PCE Initiated PCECC LSP . . . . . . . . . . . . . . . 13
5.5.4. PCECC LSP Update . . . . . . . . . . . . . . . . . . 15
5.5.5. Re Delegation and Cleanup . . . . . . . . . . . . . . 17
5.5.6. Synchronization of Central Controllers Instructions . 17
5.5.7. PCECC LSP State Report . . . . . . . . . . . . . . . 17
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5.5.8. PCC Based Allocations . . . . . . . . . . . . . . . . 18
5.5.9. Binding Label . . . . . . . . . . . . . . . . . . . . 18
6. PCEP messages . . . . . . . . . . . . . . . . . . . . . . . . 19
6.1. The PCInitiate message . . . . . . . . . . . . . . . . . 19
6.2. The PCRpt message . . . . . . . . . . . . . . . . . . . . 21
7. PCEP Objects . . . . . . . . . . . . . . . . . . . . . . . . 21
7.1. OPEN Object . . . . . . . . . . . . . . . . . . . . . . . 22
7.1.1. PCECC Capability sub-TLV . . . . . . . . . . . . . . 22
7.2. PATH-SETUP-TYPE TLV . . . . . . . . . . . . . . . . . . . 22
7.3. CCI Object . . . . . . . . . . . . . . . . . . . . . . . 23
7.3.1. Address TLVs . . . . . . . . . . . . . . . . . . . . 24
8. Implementation Status . . . . . . . . . . . . . . . . . . . . 25
8.1. Huawei's Proof of Concept based on ONOS . . . . . . . . . 26
9. Security Considerations . . . . . . . . . . . . . . . . . . . 26
9.1. Malicious PCE . . . . . . . . . . . . . . . . . . . . . . 26
10. Manageability Considerations . . . . . . . . . . . . . . . . 27
10.1. Control of Function and Policy . . . . . . . . . . . . . 27
10.2. Information and Data Models . . . . . . . . . . . . . . 27
10.3. Liveness Detection and Monitoring . . . . . . . . . . . 27
10.4. Verify Correct Operations . . . . . . . . . . . . . . . 27
10.5. Requirements On Other Protocols . . . . . . . . . . . . 27
10.6. Impact On Network Operations . . . . . . . . . . . . . . 27
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
11.1. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 27
11.2. PATH-SETUP-TYPE-CAPABILITY Sub-TLV Type Indicators . . . 28
11.3. New Path Setup Type Registry . . . . . . . . . . . . . . 28
11.4. PCEP Object . . . . . . . . . . . . . . . . . . . . . . 28
11.5. CCI Object Flag Field . . . . . . . . . . . . . . . . . 28
11.6. PCEP-Error Object . . . . . . . . . . . . . . . . . . . 29
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 29
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 30
13.1. Normative References . . . . . . . . . . . . . . . . . . 30
13.2. Informative References . . . . . . . . . . . . . . . . . 31
Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 33
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 34
1. Introduction
The Path Computation Element (PCE) [RFC4655] was developed to offload
path computation function from routers in an MPLS traffic-engineered
network. Since then, the role and function of the PCE has grown to
cover a number of other uses (such as GMPLS [RFC7025]) and to allow
delegated control [RFC8231] and PCE-initiated use of network
resources [RFC8281].
According to [RFC7399], Software-Defined Networking (SDN) refers to a
separation between the control elements and the forwarding components
so that software running in a centralized system, called a
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controller, can act to program the devices in the network to behave
in specific ways. A required element in an SDN architecture is a
component that plans how the network resources will be used and how
the devices will be programmed. It is possible to view this
component as performing specific computations to place traffic flows
within the network given knowledge of the availability of network
resources, how other forwarding devices are programmed, and the way
that other flows are routed. This is the function and purpose of a
PCE, and the way that a PCE integrates into a wider network control
system (including an SDN system) is presented in [RFC7491].
In early PCE implementations, where the PCE was used to derive paths
for MPLS Label Switched Paths (LSPs), paths were requested by network
elements (known as Path Computation Clients (PCCs)), and the results
of the path computations were supplied to network elements using the
Path Computation Element Communication Protocol (PCEP) [RFC5440].
This protocol was later extended to allow a PCE to send unsolicited
requests to the network for LSP establishment [RFC8281].
[RFC8283] introduces the architecture for PCE as a central controller
as an extension of the architecture described in [RFC4655] and
assumes the continued use of PCEP as the protocol used between PCE
and PCC. [RFC8283] further examines the motivations and
applicability for PCEP as a Southbound Interface (SBI), and
introduces the implications for the protocol.
[I-D.ietf-teas-pcecc-use-cases] describes the use cases for the PCECC
architecture.
A PCE-based central controller (PCECC) can simplify the processing of
a distributed control plane by blending it with elements of SDN and
without necessarily completely replacing it. Thus, the LSP can be
calculated/setup/initiated and the label forwarding entries can also
be downloaded through a centralized PCE server to each network
devices along the path while leveraging the existing PCE technologies
as much as possible.
This draft specify the procedures and PCEP protocol extensions for
using the PCE as the central controller for static LSPs, where LSPs
can be provisioned as explicit label instructions at each hop on the
end-to-end path. Each router along the path must be told what label-
forwarding instructions to program and what resources to reserve.
The PCE-based controller keeps a view of the network and determines
the paths of the end-to-end LSPs, and the controller uses PCEP to
communicate with each router along the path of the end-to-end LSP.
The extension for PCECC in Segment Routing (SR) is specified in a
separate draft [I-D.zhao-pce-pcep-extension-pce-controller-sr].
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1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Terminology
Terminologies used in this document is same as described in the draft
[RFC8283].
3. Basic PCECC Mode
In this mode LSPs are provisioned as explicit label instructions at
each hop on the end-to-end path. Each router along the path must be
told what label forwarding instructions to program and what resources
to reserve. The controller uses PCEP to communicate with each router
along the path of the end-to-end LSP.
Note that the PCE-based controller will take responsibility for
managing some part of the MPLS label space for each of the routers
that it controls, and may take wider responsibility for partitioning
the label space for each router and allocating different parts for
different uses. This is also described in section 3.1.2. of
[RFC8283]. For the purpose of this document, it is assumed that
label range to be used by a PCE is known and set on both PCEP peers.
A future extension could add this capability to advertise the range
via possible PCEP extensions as well (see
[I-D.li-pce-controlled-id-space]). The rest of processing is similar
to the existing stateful PCE mechanism.
This document also allow a case where the label space is maintained
by PCC itself, and the labels are allocated by the PCC, in this case,
the PCE should request the allocation from PCC as described in
Section 5.5.8.
4. PCEP Requirements
Following key requirements associated PCECC should be considered when
designing the PCECC based solution:
1. PCEP speaker supporting this draft needs to have the capability
to advertise its PCECC capability to its peers.
2. PCEP speaker needs a means to identify PCECC based LSP in the
PCEP messages.
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3. PCEP procedures needs to allow for PCC based label allocations.
4. PCEP procedures needs to provide a means to update (or cleanup)
the label-download entry to the PCC.
5. PCEP procedures needs to provide a means to synchronize the
labels between PCE to PCC in PCEP messages.
5. Procedures for Using the PCE as the Central Controller (PCECC)
5.1. Stateful PCE Model
Active stateful PCE is described in [RFC8231]. PCE as a central
controller (PCECC) reuses existing Active stateful PCE mechanism as
much as possible to control the LSP.
5.2. New LSP Functions
Several new functions are required in PCEP to support PCECC. This
document extends the existing messages to support the new functions
required by PCECC:
(PCInitiate): a PCEP message described in [RFC8281]. PCInitiate
message is used to setup PCE-Initiated LSP based on PCECC
mechanism. It is also extended for Central Controller's
Instructions (CCI) (download or cleanup the Label forwarding
instructions in the context of this document) on all nodes along
the path.
(PCRpt): a PCEP message described in [RFC8231]. PCRpt message is
used to send PCECC LSP Reports. It is also extended to report the
set of Central Controller's Instructions (CCI) (label forwarding
instructions in the context of this document) received from the
PCE. See Section 5.5.6 for more details.
(PCUpd): a PCEP message described in [RFC8231]. PCUpd message is
used to send PCECC LSP Update.
The new functions defined in this document are mapped onto the PCEP
messages as shown in the following table.
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+----------------------------------------+--------------------------+
| Function | Message |
+----------------------------------------+--------------------------+
| PCECC Capability advertisement | Open |
| Label entry Add | PCInitiate |
| Label entry Cleanup | PCInitiate |
| PCECC Initiated LSP | PCInitiate |
| PCECC LSP Update | PCUpd |
| PCECC LSP State Report | PCRpt |
| PCECC LSP Delegation | PCRpt |
| PCECC Label Report | PCRpt |
+----------------------------------------+--------------------------+
5.3. New PCEP Object
This document specify a new PCEP object called CCI (see Section 7.3)
for the encoding of central controller's instructions. In the scope
of this document this is limited to Label forwarding instructions.
Future documents can create new CCI object-type for other types of
central control instructions. The CC-ID is the unique identifier for
the central controller's instructions in PCEP. The PCEP messages are
extended in this document to handle the PCECC operations.
5.4. PCECC Capability Advertisement
During PCEP Initialization Phase, PCEP Speakers (PCE or PCC)
advertise their support of PCECC extensions.
This document defines a new Path Setup Type (PST) [RFC8408] for
PCECC, as follows:
o PST = TBD1: Path is setup via PCECC mode.
A PCEP speaker MUST indicate its support of the function described in
this document by sending a PATH-SETUP-TYPE-CAPABILITY TLV in the OPEN
object with this new PST included in the PST list.
This document also defines the PCECC Capability sub-TLV
Section 7.1.1. PCEP speakers use this sub-TLV to exchange
information about their PCECC capability. If a PCEP speaker includes
PST=TBD1 in the PST List of the PATH-SETUP-TYPE-CAPABILITY TLV then
it MUST also include the PCECC Capability sub-TLV inside the PATH-
SETUP-TYPE-CAPABILITY TLV. If the sub-TLV is absent, then the PCEP
speaker MUST send a PCErr message with Error-Type 10 (Reception of an
invalid object) and Error-Value TBD2 (Missing PCECC Capability sub-
TLV) and MUST then close the PCEP session. If a PCEP speaker
receives a PATH-SETUP-TYPE-CAPABILITY TLV with a PCECC-CAPABILITY
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sub-TLV, but the PST list does not contain PST=TBD1, then the PCEP
speaker MUST ignore the PCECC-CAPABILITY sub-TLV.
The presence of the PST=TBD1 and PCECC Capability sub-TLV in PCC's
OPEN Object indicates that the PCC is willing to function as a PCECC
client. The presence of the PST=TBD1 and PCECC Capability sub-TLV in
PCE's OPEN message indicates that the PCE is interested in function
as a PCECC server.
The PCEP protocol extensions for PCECC MUST NOT be used if one or
both PCEP Speakers have not included the PST=TBD1 or the PCECC
Capability sub-TLV in their respective OPEN message. If the PCEP
Speakers support the extensions of this draft but did not advertise
this capability attempts a PCECC operation then a PCErr message with
Error-Type=19(Invalid Operation) and Error-Value=TBD3 (Attempted
PCECC operations when PCECC capability was not advertised) will be
generated and the PCEP session will be terminated.
A PCC or a PCE MUST include both PCECC-CAPABILITY sub-TLV and
STATEFUL-PCE-CAPABILITY TLV ([RFC8231]) (with I flag set [RFC8281])
in OPEN Object to support the extensions defined in this document.
If PCECC-CAPABILITY sub-TLV is advertised and STATEFUL-PCE-CAPABILITY
TLV is not advertised in OPEN Object, it MUST send a PCErr message
with Error-Type=19 (Invalid Operation) and Error-value=TBD4 (stateful
PCE capability was not advertised) and terminate the session. This
error is also triggered if PCECC-CAPABILITY sub-TLV is advertised and
I flag in the STATEFUL-PCE-CAPABILITY TLV is not set.
5.5. LSP Operations
The PCEP messages pertaining to PCECC MUST include PATH-SETUP-TYPE
TLV [RFC8408] in the SRP object to clearly identify the PCECC LSP is
intended.
5.5.1. Basic PCECC LSP Setup
In order to setup a LSP based on PCECC mechanism, a PCC MUST delegate
the LSP by sending a PCRpt message with PST set for PCECC (see
Section 7.2) and D (Delegate) flag (see [RFC8231]) set in the LSP
object.
LSP-IDENTIFIER TLV MUST be included for PCECC LSP, the tuple uniquely
identifies the LSP in the network. The LSP object is included in
central controller's instructions (label download) to identify the
PCECC LSP for this instruction. The PLSP-ID is the original
identifier used by the ingress PCC, so the transit LSR could have
multiple central controller instructions that have the same PLSP-ID.
The PLSP-ID in combination with the source (in LSP-IDENTIFIER TLV)
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MUST be unique. The PLSP-ID is included for maintainability reasons
to ease debugging. As per [RFC8281], the LSP object could include
SPEAKER-ENTITY-ID TLV to identify the PCE that initiated these
instructions. Also the CC-ID is unique on the PCEP session as
described in Section 7.3.
When a PCE receives PCRpt message with D flags and PST Type set, it
calculates the path and assigns labels along the path; and set up the
path by sending PCInitiate message to each node along the path of the
LSP. The PCC generates a Path Computation State Report (PCRpt) and
include the central controller's instruction (CCI) and the identified
LSP. The CC-ID is uniquely identify the central controller's
instruction within a PCEP session. The PCC further responds with the
PCRpt messages including the CCI and LSP objects.
The Ingress node would receive one CCI object with O bit (out-label)
set. The transit node(s) would receive two CCI object with the in-
label CCI without O bit set and the out-label CCI with O bit set.
The egress node would receive one CCI object without O bit set. A
node can determine its role based on the setting of the O bit in the
CCI object(s).
Once the central controller's instructions (label operations) are
completed, the PCE MUST send the PCUpd message to the Ingress PCC.
This PCUpd message is as per [RFC8231] SHOULD include the path
information as calculated by the PCE.
Note that the PCECC LSPs MUST be delegated to a PCE at all times.
LSP deletion operation for PCECC LSP is same as defined in [RFC8231].
If the PCE receives PCRpt message for LSP deletion then it does Label
cleanup operation as described in Section 5.5.2.2 for the
corresponding LSP.
The Basic PCECC LSP setup sequence is as shown below.
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+-------+ +-------+
|PCC | | PCE |
|Ingress| +-------+
+------| | |
| PCC +-------+ |
| Transit| | |
+------| | |-- PCRpt,PLSP-ID=1, PST=TBD1, D=1--->| PCECC LSP
|PCC +--------+ | |
|Egress | | | |
+--------+ | | |
| | | |
|<------ PCInitiate,CC-ID=X,PLSP-ID=1 ------------ | Label
| | | L1,O=0 | download
|------- PCRpt,CC-ID=X,PLSP-ID=1 ----------------->| CCI
| | | |
| |<----- PCInitiate,PLSP-ID=1, ------------- | Labels
| | | CC-ID=Y1,O=0,L2 | download
| | | CC-ID=Y2,O=1,L1 | CCI
| |----- PCRpt,CC-ID=Y1,Y2,PLSP-ID=1 ------>|
| | | |
| | |<--- PCInitiate,CC-ID=Z,PLSP-ID=1 - | Label
| | | L2,O=1 | download
| | |---- PCRpt,CC-ID=Z,PLSP-ID=1 ------>| CCI
| | | |
| | |<-- PCUpd,PLSP-ID=1,PST=TBD1, D=1----| PCECC LSP
| | | | Update
| | | |
Figure 2: Basic PCECC LSP setup
The PCECC LSP are considered to be 'up' by default (on receipt of
PCUpd message from PCE). The Ingress MAY further choose to deploy a
data plane check mechanism and report the status back to the PCE via
PCRpt message.
In case where the label allocation are made by the PCC itself (see
Section 5.5.8), the PCE could request an allocation to be made by the
PCC, and where the PCC would send a PCRpt with the allocated label
encoded in the CC-ID object as shown below -
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+-------+ +-------+
|PCC | | PCE |
|Ingress| +-------+
+------| | |
| PCC +-------+ |
| Transit| | |
+------| | |-- PCRpt,PLSP-ID=1, PST=TBD1, D=1--->| PCECC LSP
|PCC +--------+ | |
|Egress | | | |
+--------+ | | |
| | | |
|<------ PCInitiate,CC-ID=X,PLSP-ID=1 ------------ | Label
| | | C=1 | download
|------- PCRpt,CC-ID=X,PLSP-ID=1 ----------------->| CCI
| | | Label=L1 |
| |<----- PCInitiate,PLSP-ID=1, ------------- | Labels
| | | CC-ID=Y1,C=1 | download
| | | CC-ID=Y2,C=0,L1 | CCI
| |----- PCRpt,PLSP-ID=1 ------------------>|
| | | CC-ID=Y1, Label=L2 |
| | | CC-ID=Y2 |
| | |<--- PCInitiate,CC-ID=Z,PLSP-ID=1 - | Label
| | | C=0,L2 | download
| | |---- PCRpt,CC-ID=Z,PLSP-ID=1 ------>| CCI
| | | |
| | |<-- PCUpd,PLSP-ID=1,PST=TBD1, D=1----| PCECC LSP
| | | | Update
| | | |
- The O bit is set as before (and thus not included)
Figure 3: Basic PCECC LSP setup (PCC allocation)
It should be noted that in this example, the request is made to the
egress node with C bit set in the CCI object to indicate that the
label allocation needs to be done by the egress and it responds with
the allocated label to the PCE. The PCE would further inform the
transit PCC without setting the C bit in the CCI object for out-label
but the C-bit is set for in-label so the transit node make the label
allocation (for the in-label) and report to the PCE. Similarly C bit
is unset towards the ingress to complete all the label allocation for
the PCECC LSP.
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5.5.2. Central Control Instructions
The new central controller's instructions (CCI) for the label
operations in PCEP is done via the PCInitiate message, by defining a
new PCEP Objects for CCI operations. Local label range of each PCC
is assumed to be known at both the PCC and the PCE.
5.5.2.1. Label Download CCI
In order to setup an LSP based on PCECC, the PCE sends a PCInitiate
message to each node along the path to download the Label instruction
as described in Section 5.5.1.
The CCI object MUST be included, along with the LSP object in the
PCInitiate message. The LSP-IDENTIFIER TLV MUST be included in LSP
object. The SPEAKER-ENTITY-ID TLV SHOULD be included in LSP object.
If a node (PCC) receives a PCInitiate message which includes a Label
to download as part of CCI, that is out of the range set aside for
the PCE, it MUST send a PCErr message with Error-type=TBD5 (PCECC
failure) and Error-value=TBD6 (Label out of range) and MUST include
the SRP object to specify the error is for the corresponding label
update via PCInitiate message. If a PCC receives a PCInitiate
message but failed to download the Label entry, it MUST send a PCErr
message with Error-type=TBD5 (PCECC failure) and Error-value=TBD7
(instruction failed) and MUST include the SRP object to specify the
error is for the corresponding label update via PCInitiate message.
New PCEP object for central control instructions (CCI) is defined in
Section 7.3.
5.5.2.2. Label Cleanup CCI
In order to delete an LSP based on PCECC, the PCE sends a central
controller instructions via a PCInitiate message to each node along
the path of the LSP to cleanup the Label forwarding instruction.
If the PCC receives a PCInitiate message but does not recognize the
label in the CCI, the PCC MUST generate a PCErr message with Error-
Type 19(Invalid operation) and Error-Value=TBD8, "Unknown Label" and
MUST include the SRP object to specify the error is for the
corresponding label cleanup (via PCInitiate message).
The R flag in the SRP object defined in [RFC8281] specifies the
deletion of Label Entry in the PCInitiate message.
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+-------+ +-------+
|PCC | | PCE |
|Ingress| +-------+
+------| | |
| PCC +-------+ |
| Transit| | |
+------| | |-- PCRpt,PLSP-ID=1,PST=TBD1,D=1,R=1-->| PCECC LSP
|PCC +--------+ | | remove
|Egress | | | |
+--------+ | | |
| | | |
|<------ PCInitiate,CC-ID=X,PLSP-ID=1 ------------ | Label
| | | R=1 | cleanup
|------- PCRpt,CC-ID=X,PLSP-ID=1 ------------------>| CCI
| | | |
| |<----- PCInitiate,CC-ID=Y1,Y2,PLSP-ID=1 -- | Label
| | | R=1 | cleanup
| |----- PCRpt,CC-ID=Y1,Y2,PLSP-ID=1 ------->| CCI
| | | |
| | |<--- PCInitiate,CC-ID=Z,PLSP-ID=1 -- | Label
| | | R=1 | cleanup
| | |---- PCRpt,CC-ID=Z,PLSP-ID=1 ------->| CCI
| | | |
As per [RFC8281], following the removal of the Label forwarding
instruction, the PCC MUST send a PCRpt message. The SRP object in
the PCRpt MUST include the SRP-ID-number from the PCInitiate message
that triggered the removal. The R flag in the SRP object MUST be
set.
In case where the label allocation are made by the PCC itself (see
Section 5.5.8), the removal procedure remains the same.
5.5.3. PCE Initiated PCECC LSP
The LSP Instantiation operation is same as defined in [RFC8281].
In order to setup a PCE Initiated LSP based on the PCECC mechanism, a
PCE sends PCInitiate message with Path Setup Type set for PCECC (see
Section 7.2) to the Ingress PCC.
The Ingress PCC MUST also set D (Delegate) flag (see [RFC8231]) and C
(Create) flag (see [RFC8281]) in LSP object of PCRpt message. The
PCC responds with first PCRpt message with the status as "GOING-UP"
and assigned PLSP-ID.
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Note that the label forwarding instructions from PCECC are send after
the initial PCInitiate and PCRpt exchange. This is done so that the
PLSP-ID and other LSP identifiers can be obtained from the ingress
and can be included in the label forwarding instruction in the next
PCInitiate message. The rest of the PCECC LSP setup operations are
same as those described in Section 5.5.1.
The LSP deletion operation for PCE Initiated PCECC LSP is same as
defined in [RFC8281]. The PCE should further perform Label entry
cleanup operation as described in Section 5.5.2.2 for the
corresponding LSP.
The PCE Initiated PCECC LSP setup sequence is shown below -
+-------+ +-------+
|PCC | | PCE |
|Ingress| +-------+
+------| | |
| PCC +-------+ |
| Transit| | |
+------| | |<--PCInitiate,PLSP-ID=0,PST=TBD1,D=1--| PCECC LSP
|PCC +--------+ | | Initiate
|Egress | | |--- PCRpt,PLSP-ID=2,P=1,D=1,C=1---> | PCECC LSP
+--------+ | | (GOING-UP) |
| | | |
|<------ PCInitiate,CC-ID=X,PLSP-ID=2 -------------- | Label
| | | | download
|------- PCRpt,CC-ID=X,PLSP-ID=2 ------------------>| CCI
| | | |
| |<----- PCInitiate,CC-ID=Y1,Y2,PLSP-ID=2 --- | Label
| | | | download
| |----- PCRpt,CC-ID=Y1,Y2,PLSP-ID=2 ------->| CCI
| | | |
| | |<--- PCInitiate,CC-ID=Z,PLSP-ID=2 --- | Label
| | | | download
| | |---- PCRpt,CC-ID=Z,PLSP-ID=2 ------->| CCI
| | | |
| | |<-- PCUpd, PLSP-ID=2, PST=TBD1, D=1-- | PCECC LSP
| | | (UP) | Update
| | |--- PCRpt,PLSP-ID=2,P=1,D=1,C=1---> |
| | | (UP) |
Once the label operations are completed, the PCE SHOULD send the
PCUpd message to the Ingress PCC. The PCUpd message is as per
[RFC8231].
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In case where the label allocation are made by the PCC itself (see
Section 5.5.8), the procedure remains similar.
5.5.4. PCECC LSP Update
In case of a modification of PCECC LSP with a new path, a PCE sends a
PCUpd message to the Ingress PCC. But to follow the make-before-
break procedures, the PCECC first update new instructions based on
the updated LSP and then update to ingress to switch traffic, before
cleaning up the old instructions. A new CC-ID is used to identify
the updated instruction, the existing identifiers in the LSP object
identify the existing LSP. Once new instructions are downloaded, the
PCE further updates the new path at the ingress which triggers the
traffic switch on the updated path. The Ingress PCC acknowledges
with a PCRpt message, on receipt of PCRpt message, the PCE does
cleanup operation for the old LSP as described in Section 5.5.2.2.
The PCECC LSP Update sequence is shown below -
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+-------+ +-------+
|PCC | | PCE |
|Ingress| +-------+
+------| | |
| PCC +-------+ |
| Transit| | |
+------| | | |
|PCC +--------+ | |
|Egress | | | |
+--------+ | | |
| | | | New Path
|<------ PCInitiate,CC-ID=XX,PLSP-ID=1 ----------- | for LSP
| | | | trigger
|------- PCRpt,CC-ID=XX,PLSP-ID=1 ---------------->| new CCI
| | | |
| |<----- PCInitiate,CC-ID=YY1,YY2,PLSP-ID=1--| Label
| | | | download
| |----- PCRpt,CC-ID=YY1,YY2,PLSP-ID=1 ---->| CCI
| | | |
| | |<--- PCInitiate,CC-ID=ZZ,PLSP-ID=1 - | Label
| | | | download
| | |---- PCRpt,CC-ID=ZZ,PLSP-ID=1 ----->| CCI
| | | |
| | |<-- PCUpd, PLSP-ID=1, PST=TBD1, D=1- | PCECC
| | | SRP=S | LSP Update
| | | |
| | |-- PCRpt,PLSP-ID=1,PST=TBD1,D=1 -->| Trigger
| | | (SRP=S) | Delete old
| | | | CCI
| | | |
|<------ PCInitiate,CC-ID=X, PLSP-ID=1 ----------- | Label
| | | R=1 | cleanup
|------- PCRpt,CC-ID=X, PLSP-ID=1 ---------------->| CCI
| | | |
| |<----- PCInitiate,CC-ID=Y1,Y2, PLSP-ID=1 - | Label
| | | R=1 | cleanup
| |----- PCRpt,CC-ID=Y1,Y2, PLSP-ID=1 ----->| CCI
| | | |
| | |<--- PCInitiate,CC-ID=Z, PLSP-ID=1 - | Label
| | | R=1 | cleanup
| | |---- PCRpt,CC-ID=Z, PLSP-ID=1 ----->| CCI
| | | |
The modified PCECC LSP are considered to be 'up' by default. The
Ingress MAY further choose to deploy a data plane check mechanism and
report the status back to the PCE via PCRpt message.
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In case where the label allocation are made by the PCC itself (see
Section 5.5.8), the procedure remains similar.
5.5.5. Re Delegation and Cleanup
As described in [RFC8281], a new PCE can gain control over the
orphaned LSP. In case of PCECC LSP, the new PCE MUST also gain
control over the central controllers instructions in the same way by
sending a PCInitiate message that includes the SRP, LSP and CCI
objects and carries the CC-ID and PLSP-ID identifying the
instruction, it wants to take control of.
Further, as described in [RFC8281], the State Timeout Interval timer
ensures that a PCE crash does not result in automatic and immediate
disruption for the services using PCE-initiated LSPs. Similarly the
central controller instructions are not removed immediately upon PCE
failure. Instead, they are cleaned up on the expiration of this
timer. This allows for network cleanup without manual intervention.
The PCC MUST support removal of CCI as one of the behaviors applied
on expiration of the State Timeout Interval timer.
5.5.6. Synchronization of Central Controllers Instructions
The purpose of Central Controllers Instructions synchronization
(labels in the context of this document) is to make sure that the
PCE's view of CCI (Labels) matches with the PCC's Label allocation.
This synchronization is performed as part of the LSP state
synchronization as described in [RFC8231] and [RFC8233].
As per LSP State Synchronization [RFC8231], a PCC reports the state
of its LSPs to the PCE using PCRpt messages and as per [RFC8281], PCE
would initiate any missing LSPs and/or remove any LSPs that are not
wanted. The same PCEP messages and procedure is also used for the
Central Controllers Instructions synchronization. The PCRpt message
includes the CCI and the LSP object to report the label forwarding
instructions. The PCE would further remove any unwanted instructions
or initiate any missing instructions.
5.5.7. PCECC LSP State Report
As mentioned before, an Ingress PCC MAY choose to apply any OAM
mechanism to check the status of LSP in the Data plane and MAY
further send its status in PCRpt message to the PCE.
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5.5.8. PCC Based Allocations
The PCE can request the PCC to allocate the label using the
PCInitiate message. The C flag in the CCI object is set to 1 to
indicate that the allocation needs to be done by the PCC. The PCC
would allocate the Label and would report to the PCE using the PCRpt
message.
If the value of the Label is 0 and the C flag is set, it indicates
that the PCE is requesting the allocation to be done by the PCC. If
the Label is 'n' and the C flag is set in the CCI object, it
indicates that the PCE requests a specific value 'n' for the Label.
If the allocation is successful, the PCC should report via PCRpt
message with the CCI object. Else, it MUST send a PCErr message with
Error-Type = TBD5 ("PCECC failure") and Error Value = TBD9 ("Invalid
CCI"). If the value of the the Label in the CCI object is valid, but
the PCC is unable to allocate it, it MUST send a PCErr message with
Error-Type = TBD5 ("PCECC failure") and Error Value = TBD10 ("Unable
to allocate the specified CCI").
If the PCC wishes to withdraw or modify the previously assigned
label, it MUST send a PCRpt message without any Label or with the
Label containing the new value respectively in the CCI object. The
PCE would further trigger the removal of the central controller
instruction as per this document.
5.5.9. Binding Label
As per [I-D.sivabalan-pce-binding-label-sid], when a stateful PCE is
deployed for setting up TE paths, it may be desirable to report the
binding label to the stateful PCE for the purpose of enforcing end-
to-end TE. In case of PCECC, the binding label may be allocated by
the PCE itself as described in this section. This procedure is thus
applicable for all path setup types including PCECC.
A P flag in LSP object is introduced in [I-D.li-pce-sr-path-segment]
to indicate the allocation needs to be made by the PCE. This flag is
used to indicate that the allocation needs to be made by the PCE. A
PCC would set this bit to 1 (and carry the TE-PATH-BINDING TLV
[I-D.sivabalan-pce-binding-label-sid] in LSP object) to request for
allocation of the binding label by the PCE in the PCReq or PCRpt
message. A PCE would also set this bit to 1 to indicate that the
binding label is allocated by PCE and encoded in the PCRep, PCUpd or
PCInitiate message (the TE-PATH-BINDING TLV is present in LSP
object). Further, a PCE would set this bit to 0 to indicate that the
allocation is done by the PCC instead.
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The ingress PCC could request the binding label to be allocated by
the PCE via PCRpt message as per [RFC8231]. The delegate flag
(D-flag) MUST also be set for this LSP. The TE-PATH-BINDING TLV MUST
be included with no Binding Value. The PCECC would allocate the
binding label and further respond to Ingress PCC with PCUpd message
as per [RFC8231] and MUST include the TE-PATH-BINDING TLV in a LSP
object. The P flag in the LSP object would be set to 1 to indicate
that the allocation is made by the PCE.
The PCE could allocate the binding label on its own accord for a PCE-
Initiated (or delegated LSP). The allocated binding label needs to
be informed to the PCC. The PCE would use the PCInitiate message
[RFC8281] or PCUpd message [RFC8231] towards the PCC and MUST include
the TE-PATH-BINDING TLV in the LSP object. The P flag in the LSP
object would be set to 1 to indicate that the allocation is made by
the PCE.
The PCECC capability MUST be exchanged on the PCEP session, before
PCE could allocate binding label. Note that the CCI object is not
used for binding allocation; this is done to maintain consistency
with the rest of the binding label/SID procedures as per
[I-D.sivabalan-pce-binding-label-sid].
6. PCEP messages
As defined in [RFC5440], a PCEP message consists of a common header
followed by a variable-length body made of a set of objects that can
be either mandatory or optional. An object is said to be mandatory
in a PCEP message when the object must be included for the message to
be considered valid. For each PCEP message type, a set of rules is
defined that specify the set of objects that the message can carry.
An implementation MUST form the PCEP messages using the object
ordering specified in this document.
LSP-IDENTIFIERS TLV MUST be included in the LSP object for PCECC LSP.
6.1. The PCInitiate message
The PCInitiate message [RFC8281] can be used to download or remove
the labels, the message has been extended as shown below -
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<PCInitiate Message> ::= <Common Header>
<PCE-initiated-lsp-list>
Where:
<Common Header> is defined in [RFC5440]
<PCE-initiated-lsp-list> ::= <PCE-initiated-lsp-request>
[<PCE-initiated-lsp-list>]
<PCE-initiated-lsp-request> ::=
(<PCE-initiated-lsp-instantiation>|
<PCE-initiated-lsp-deletion>|
<PCE-initiated-lsp-central-control>)
<PCE-initiated-lsp-central-control> ::= <SRP>
<LSP>
<cci-list>
<cci-list> ::= <CCI>
[<cci-list>]
Where:
<PCE-initiated-lsp-instantiation> and
<PCE-initiated-lsp-deletion> are as per
[RFC8281].
The LSP and SRP object is defined in [RFC8231].
When PCInitiate message is used for central controller's instructions
(labels), the SRP, LSP and CCI objects MUST be present. The SRP
object is defined in [RFC8231] and if the SRP object is missing, the
receiving PCC MUST send a PCErr message with Error-type=6 (Mandatory
Object missing) and Error-value=10 (SRP object missing). The LSP
object is defined in [RFC8231] and if the LSP object is missing, the
receiving PCC MUST send a PCErr message with Error-type=6 (Mandatory
Object missing) and Error-value=8 (LSP object missing). The CCI
object is defined in Section 7.3 and if the CCI object is missing,
the receiving PCC MUST send a PCErr message with Error-type=6
(Mandatory Object missing) and Error-value=TBD11 (CCI object
missing). More than one CCI object MAY be included in the PCInitiate
message for the transit LSR.
To cleanup the SRP object must set the R (remove) bit and include the
LSP and the CCI object.
At max two instances of CCI object would be included in case of
transit LSR to encode both in-coming and out-going label forwarding
instructions. Other instances MUST be ignored.
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6.2. The PCRpt message
The PCRpt message can be used to report the labels that were
allocated by the PCE, to be used during the state synchronization
phase.
<PCRpt Message> ::= <Common Header>
<state-report-list>
Where:
<state-report-list> ::= <state-report>[<state-report-list>]
<state-report> ::= (<lsp-state-report>|
<central-control-report>)
<lsp-state-report> ::= [<SRP>]
<LSP>
<path>
<central-control-report> ::= [<SRP>]
<LSP>
<cci-list>
<cci-list> ::= <CCI>
[<cci-list>]
Where:
<path> is as per [RFC8231] and the LSP and SRP object are
also defined in [RFC8231].
When PCRpt message is used to report the central controller's
instructions (labels), the LSP and CCI objects MUST be present. The
LSP object is defined in [RFC8231] and if the LSP object is missing,
the receiving PCE MUST send a PCErr message with Error-type=6
(Mandatory Object missing) and Error-value=8 (LSP object missing).
The CCI object is defined in Section 7.3 and if the CCI object is
missing, the receiving PCC MUST send a PCErr message with Error-
type=6 (Mandatory Object missing) and Error-value=TBD11 (CCI object
missing). Two CCI object can be included in the PCRpt message for
the transit LSR.
7. PCEP Objects
The PCEP objects defined in this document are compliant with the PCEP
object format defined in [RFC5440].
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7.1. OPEN Object
This document defines a new optional TLVs for use in the OPEN Object.
7.1.1. PCECC Capability sub-TLV
The PCECC-CAPABILITY sub-TLV is an optional TLV for use in the OPEN
Object for PCECC capability advertisement in PATH-SETUP-TYPE-
CAPABILITY TLV. Advertisement of the PCECC capability implies
support of LSPs that are setup through PCECC as per PCEP extensions
defined in this document.
Its format is shown in the following figure:
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=TBD12 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The type of the TLV is TBD12 and it has a fixed length of 4 octets.
The value comprises a single field - Flags (32 bits).
No flags are assigned right now.
Unassigned bits are considered reserved. They MUST be set to 0 on
transmission and MUST be ignored on receipt.
7.2. PATH-SETUP-TYPE TLV
The PATH-SETUP-TYPE TLV is defined in [RFC8408]; this document
defines a new PST value:
o PST = TBD1: Path is setup via PCECC mode.
On a PCRpt/PCUpd/PCInitiate message, the PST=TBD1 in PATH-SETUP-TYPE
TLV in SRP object indicates that this LSP was setup via a PCECC based
mechanism.
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7.3. CCI Object
The Central Control Instructions (CCI) Object is used by the PCE to
specify the forwarding instructions (Label information in the context
of this document) to the PCC, and MAY be carried within PCInitiate or
PCRpt message for label download.
CCI Object-Class is TBD13.
CCI Object-Type is 1 for the MPLS Label.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CC-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Flags |C|O|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Optional TLV //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields in the CCI object are as follows:
CC-ID: A PCEP-specific identifier for the CCI information. A PCE
creates an CC-ID for each instruction, the value is unique within
the scope of the PCE and is constant for the lifetime of a PCEP
session. The values 0 and 0xFFFFFFFF are reserved and MUST NOT be
used.
Flags: is used to carry any additional information pertaining to the
CCI. Currently, the following flag bit is defined:
* O bit(Out-label) : If the bit is set, it specifies the label is
the OUT label and it is mandatory to encode the next-hop
information (via IPV4-ADDRESS TLV or IPV6-ADDRESS TLV or
UNNUMBERED-IPV4-ID-ADDRESS TLV in the CCI object). If the bit
is not set, it specifies the label is the IN label and it is
optional to encode the local interface information (via
IPV4-ADDRESS TLV or IPV6-ADDRESS TLV or UNNUMBERED-IPV4-ID-
ADDRESS TLV in the CCI object).
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* C-Bit (PCC Allocation): If the bit is set to 1, it indicates
that the allocation needs to be done by the PCC for this
central controller instruction. A PCE set this bit to request
the PCC to make an allocation from its label space. A PCC
would set this bit to indicate that it has allocated the CC-ID
and report it to the PCE.
Label (20-bit): The Label information.
Reserved (12 bit): Set to zero while sending, ignored on receive.
7.3.1. Address TLVs
This document defines the following TLVs for the CCI object to
associate the next-hop information in case of an outgoing label and
local interface information in case of an incoming label.
IPV4-ADDRESS TLV:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD14 | Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPV6-ADDRESS TLV:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD15 | Length = 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// IPv6 address (16 bytes) //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
UNNUMBERED-IPV4-ID-ADDRESS TLV:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD16 | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Node-ID |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
LINKLOCAL-IPV6-ID-ADDRESS TLV:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD17 | Length = 40 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Local IPv6 address (16 octets) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Remote IPv6 address (16 octets) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The address TLVs are as follows:
IPV4-ADDRESS TLV: an IPv4 address.
IPV6-ADDRESS TLV: an IPv6 address.
UNNUMBERED-IPV4-ID-ADDRESS TLV: a Node ID / Interface ID tuple.
LINKLOCAL-IPV6-ID-ADDRESS TLV: a pair of (global IPv6 address,
interface ID) tuples.
8. Implementation Status
[Note to the RFC Editor - remove this section before publication, as
well as remove the reference to RFC 7942.]
This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in [RFC7942].
The description of implementations in this section is intended to
assist the IETF in its decision processes in progressing drafts to
RFCs. Please note that the listing of any individual implementation
here does not imply endorsement by the IETF. Furthermore, no effort
has been spent to verify the information presented here that was
supplied by IETF contributors. This is not intended as, and must not
be construed to be, a catalog of available implementations or their
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features. Readers are advised to note that other implementations may
exist.
According to [RFC7942], "this will allow reviewers and working groups
to assign due consideration to documents that have the benefit of
running code, which may serve as evidence of valuable experimentation
and feedback that have made the implemented protocols more mature.
It is up to the individual working groups to use this information as
they see fit".
8.1. Huawei's Proof of Concept based on ONOS
The PCE function was developed in the ONOS open source platform.
This extension was implemented on a private version as a proof of
concept for PCECC.
o Organization: Huawei
o Implementation: Huawei's PoC based on ONOS
o Description: PCEP as a southbound plugin was added to ONOS. To
support PCECC, an earlier version of this I-D was implemented.
Refer https://wiki.onosproject.org/display/ONOS/PCEP+Protocol
o Maturity Level: Prototype
o Coverage: Partial
o Contact: satishk@huawei.com
9. Security Considerations
The security considerations described in [RFC8231] and [RFC8281]
apply to the extensions described in this document. Additional
considerations related to a malicious PCE are introduced.
9.1. Malicious PCE
PCE has complete control over PCC to update the labels and can cause
the LSP's to behave inappropriate and cause major impact to the
network. As a general precaution, it is RECOMMENDED that these PCEP
extensions only be activated on authenticated and encrypted sessions
across PCEs and PCCs belonging to the same administrative authority,
using Transport Layer Security (TLS) [RFC8253], as per the
recommendations and best current practices in [RFC7525].
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10. Manageability Considerations
10.1. Control of Function and Policy
A PCE or PCC implementation SHOULD allow to configure to enable/
disable PCECC capability as a global configuration.
10.2. Information and Data Models
[RFC7420] describes the PCEP MIB, this MIB can be extended to get the
PCECC capability status.
The PCEP YANG module [I-D.ietf-pce-pcep-yang] could be extended to
enable/disable PCECC capability.
10.3. Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements in addition to those already
listed in [RFC5440].
10.4. Verify Correct Operations
Mechanisms defined in this document do not imply any new operation
verification requirements in addition to those already listed in
[RFC5440] and [RFC8231].
10.5. Requirements On Other Protocols
PCEP extensions defined in this document do not put new requirements
on other protocols.
10.6. Impact On Network Operations
PCEP extensions defined in this document do not put new requirements
on network operations.
11. IANA Considerations
11.1. PCEP TLV Type Indicators
IANA is requested to allocate the following TLV Type Indicator values
within the "PCEP TLV Type Indicators" sub- registry of the PCEP
Numbers registry:
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Value Meaning Reference
TBD14 IPV4-ADDRESS TLV This document
TBD15 IPV6-ADDRESS TLV This document
TBD16 UNNUMBERED-IPV4-ID-ADDRESS TLV This document
TBD17 LINKLOCAL-IPV6-ID-ADDRESS TLV This document
11.2. PATH-SETUP-TYPE-CAPABILITY Sub-TLV Type Indicators
[RFC8408] requested creation of "PATH-SETUP- TYPE-CAPABILITY Sub-TLV
Type Indicators" sub-registry. Further IANA is requested to allocate
the following code-point:
Value Meaning Reference
TBD12 PCECC-CAPABILITY This document
11.3. New Path Setup Type Registry
[RFC8408] created a sub-registry within the "Path Computation Element
Protocol (PCEP) Numbers" registry called "PCEP Path Setup Types".
IANA is requested to allocate a new code point within this registry,
as follows:
Value Description Reference
TBD1 Traffic engineering path is This document
setup using PCECC mode
11.4. PCEP Object
IANA is requested to allocate new code-point in the "PCEP Objects"
sub-registry for the CCI object as follows:
Object-Class Value Name Reference
TBD13 CCI Object-Type This document
0 Reserved
1 MPLS Label
11.5. CCI Object Flag Field
IANA is requested to create a new sub-registry to manage the Flag
field of the CCI object called "CCI Object Flag Field". New values
are to be assigned by Standards Action [RFC8126]. Each bit should be
tracked with the following qualities:
o Bit number (counting from bit 0 as the most significant bit)
o Capability description
o Defining RFC
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Two bits to be defined for the CCI Object flag field in this document
as follows:
Bit Description Reference
0-13 Unassigned This document
14 C Bit - PCC allocation This document
15 O Bit - Specifies label This document
is out-label
11.6. PCEP-Error Object
IANA is requested to allocate new error types and error values within
the "PCEP-ERROR Object Error Types and Values" sub-registry of the
PCEP Numbers registry for the following errors:
Error-Type Meaning
---------- -------
10 Reception of an invalid object.
Error-value = TBD2 : Missing PCECC
Capability sub-TLV
19 Invalid operation.
Error-value = TBD3 : Attempted PCECC
operations when
PCECC capability
was not advertised
Error-value = TBD4 : Stateful PCE
capability was not
advertised
Error-value = TBD8 : Unknown Label
6 Mandatory Object missing.
Error-value = TBD11 : CCI object missing
TBD5 PCECC failure.
Error-value = TBD6 : Label out of range.
Error-value = TBD7 : Instruction failed.
Error-value = TBD9 : Invalid CCI.
Error-value = TBD10 : Unable to allocate
the specified CCI.
12. Acknowledgments
We would like to thank Robert Tao, Changjing Yan, Tieying Huang and
Avantika for their useful comments and suggestions.
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13. References
13.1. Normative References
[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>.
[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,
<https://www.rfc-editor.org/info/rfc7420>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <https://www.rfc-editor.org/info/rfc7525>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[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>.
[RFC8233] Dhody, D., Wu, Q., Manral, V., Ali, Z., and K. Kumaki,
"Extensions to the Path Computation Element Communication
Protocol (PCEP) to Compute Service-Aware Label Switched
Paths (LSPs)", RFC 8233, DOI 10.17487/RFC8233, September
2017, <https://www.rfc-editor.org/info/rfc8233>.
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[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>.
[RFC8408] Sivabalan, S., Tantsura, J., Minei, I., Varga, R., and J.
Hardwick, "Conveying Path Setup Type in PCE Communication
Protocol (PCEP) Messages", RFC 8408, DOI 10.17487/RFC8408,
July 2018, <https://www.rfc-editor.org/info/rfc8408>.
13.2. Informative References
[RFC4655] Farrel, A., Vasseur, J., 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>.
[RFC7025] Otani, T., Ogaki, K., Caviglia, D., Zhang, F., and C.
Margaria, "Requirements for GMPLS Applications of PCE",
RFC 7025, DOI 10.17487/RFC7025, September 2013,
<https://www.rfc-editor.org/info/rfc7025>.
[RFC7399] Farrel, A. and D. King, "Unanswered Questions in the Path
Computation Element Architecture", RFC 7399,
DOI 10.17487/RFC7399, October 2014,
<https://www.rfc-editor.org/info/rfc7399>.
[RFC7491] King, D. and A. Farrel, "A PCE-Based Architecture for
Application-Based Network Operations", RFC 7491,
DOI 10.17487/RFC7491, March 2015,
<https://www.rfc-editor.org/info/rfc7491>.
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>.
[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>.
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[RFC8283] Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An
Architecture for Use of PCE and the PCE Communication
Protocol (PCEP) in a Network with Central Control",
RFC 8283, DOI 10.17487/RFC8283, December 2017,
<https://www.rfc-editor.org/info/rfc8283>.
[I-D.ietf-teas-pcecc-use-cases]
Zhao, Q., Li, Z., Khasanov, B., Dhody, D., Ke, Z., Fang,
L., Zhou, C., Communications, T., Rachitskiy, A., and A.
Gulida, "The Use Cases for Path Computation Element (PCE)
as a Central Controller (PCECC).", draft-ietf-teas-pcecc-
use-cases-05 (work in progress), March 2020.
[I-D.ietf-pce-pcep-yang]
Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A
YANG Data Model for Path Computation Element
Communications Protocol (PCEP)", draft-ietf-pce-pcep-
yang-13 (work in progress), October 2019.
[I-D.zhao-pce-pcep-extension-pce-controller-sr]
Zhao, Q., Li, Z., Negi, M., and C. Zhou, "PCEP Procedures
and Protocol Extensions for Using PCE as a Central
Controller (PCECC) of SR-LSPs", draft-zhao-pce-pcep-
extension-pce-controller-sr-05 (work in progress), July
2019.
[I-D.li-pce-controlled-id-space]
Li, C., Chen, M., Dong, J., Li, Z., Wang, A., Cheng, W.,
and C. Zhou, "PCE Controlled ID Space", draft-li-pce-
controlled-id-space-04 (work in progress), January 2020.
[I-D.sivabalan-pce-binding-label-sid]
Sivabalan, S., Filsfils, C., Tantsura, J., Hardwick, J.,
Previdi, S., and C. Li, "Carrying Binding Label/Segment-ID
in PCE-based Networks.", draft-sivabalan-pce-binding-
label-sid-07 (work in progress), July 2019.
[I-D.li-pce-sr-path-segment]
Li, C., Chen, M., Cheng, W., Dong, J., Li, Z., Gandhi, R.,
and Q. Xiong, "Path Computation Element Communication
Protocol (PCEP) Extension for Path Segment in Segment
Routing (SR)", draft-li-pce-sr-path-segment-08 (work in
progress), August 2019.
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Appendix A. Contributor Addresses
Dhruv Dhody
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
EMail: dhruv.ietf@gmail.com
Satish Karunanithi
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
EMail: satishk@huawei.com
Adrian Farrel
Juniper Networks, Inc
UK
EMail: adrian@olddog.co.uk
Xuesong Geng
Huawei Technologies
China
Email: gengxuesong@huawei.com
Udayasree Palle
EMail: udayasreereddy@gmail.com
Katherine Zhao
Futurewei Technologies
EMail: katherine.zhao@futurewei.com
Boris Zhang
Telus Ltd.
Toronto
Canada
EMail: boris.zhang@telus.com
Alex Tokar
Cisco Systems
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Slovak Republic
EMail: atokar@cisco.com
Authors' Addresses
Quintin Zhao
Huawei Technologies
125 Nagog Technology Park
Acton, MA 01719
USA
EMail: quintin.zhao@huawei.com
Zhenbin Li
Huawei Technologies
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
EMail: lizhenbin@huawei.com
Mahendra Singh Negi
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
EMail: mahend.ietf@gmail.com
Shuping Peng
Huawei Technologies
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
EMail: pengshuping@huawei.com
Chao Zhou
Cisco Systems
EMail: chao.zhou@cisco.com
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