PCE Working Group Q. Zhao
Internet-Draft Z. Li
Intended status: Standards Track D. Dhody
Expires: September 5, 2018 S. Karunanithi
Huawei Technologies
A. Farrel
Juniper Networks, Inc
C. Zhou
Cisco Systems
March 4, 2018
PCEP Procedures and Protocol Extensions for Using PCE as a Central
Controller (PCECC) of SR-LSPs
draft-zhao-pce-pcep-extension-pce-controller-sr-02
Abstract
In certain networks deployment scenarios, service providers would
like to keep all the existing MPLS functionalities in both MPLS and
GMPLS while removing the complexity of existing signaling protocols
such as LDP and RSVP-TE. PCE has been proposed to be used as a
central controller (PCECC) so that LSP can be calculated/setup/
initiated and label forwarding entries are 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
when the PCE functions as one of the central controller components in
Segment Routing(SR).
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at 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 5, 2018.
Zhao, et al. Expires September 5, 2018 [Page 1]
Internet-Draft PCECC March 2018
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. PCECC SR . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. PCEP Requirements . . . . . . . . . . . . . . . . . . . . . . 5
5. Procedures for Using the PCE as the Central Controller
(PCECC) in Segment Routing . . . . . . . . . . . . . . . . . 6
5.1. Stateful PCE Model . . . . . . . . . . . . . . . . . . . 6
5.2. New LSP Functions . . . . . . . . . . . . . . . . . . . . 6
5.3. PCECC Capability Advertisement . . . . . . . . . . . . . 6
5.4. PCEP session IP address and TEDB Router ID . . . . . . . 7
5.5. LSP Operations . . . . . . . . . . . . . . . . . . . . . 7
5.5.1. PCECC Segment Routing (SR) . . . . . . . . . . . . . 7
5.5.1.1. PCECC SR Node/Prefix Label allocation . . . . . . 8
5.5.1.2. PCECC SR Adjacency Label allocation . . . . . . . 9
5.5.1.3. Redundant PCEs . . . . . . . . . . . . . . . . . 10
5.5.1.4. Session Termination . . . . . . . . . . . . . . . 11
5.5.1.5. LABEL-DB Synchronization . . . . . . . . . . . . 11
6. PCEP messages . . . . . . . . . . . . . . . . . . . . . . . . 11
6.1. Label Operations . . . . . . . . . . . . . . . . . . . . 11
6.1.1. The PCLabelUpd message . . . . . . . . . . . . . . . 12
6.1.2. The PCLabelRpt message . . . . . . . . . . . . . . . 12
7. PCEP Objects . . . . . . . . . . . . . . . . . . . . . . . . 13
7.1. OPEN Object . . . . . . . . . . . . . . . . . . . . . . . 13
7.1.1. PCECC Capability sub-TLV . . . . . . . . . . . . . . 13
7.2. PATH-SETUP-TYPE TLV . . . . . . . . . . . . . . . . . . . 14
7.3. FEC Object . . . . . . . . . . . . . . . . . . . . . . . 14
8. Security Considerations . . . . . . . . . . . . . . . . . . . 16
9. Manageability Considerations . . . . . . . . . . . . . . . . 16
9.1. Control of Function and Policy . . . . . . . . . . . . . 16
9.2. Information and Data Models . . . . . . . . . . . . . . . 16
Zhao, et al. Expires September 5, 2018 [Page 2]
Internet-Draft PCECC March 2018
9.3. Liveness Detection and Monitoring . . . . . . . . . . . . 16
9.4. Verify Correct Operations . . . . . . . . . . . . . . . . 16
9.5. Requirements On Other Protocols . . . . . . . . . . . . . 16
9.6. Impact On Network Operations . . . . . . . . . . . . . . 17
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
10.1. PCECC-CAPABILITY TLV . . . . . . . . . . . . . . . . . . 17
10.2. PCEP Object . . . . . . . . . . . . . . . . . . . . . . 17
10.3. PCEP-Error Object . . . . . . . . . . . . . . . . . . . 17
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
12.1. Normative References . . . . . . . . . . . . . . . . . . 18
12.2. Informative References . . . . . . . . . . . . . . . . . 19
Appendix A. Using existing PCEP message . . . . . . . . . . . . 22
Appendix B. Contributor Addresses . . . . . . . . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction
The Path Computation Element communication Protocol (PCEP) provides
mechanisms for Path Computation Elements (PCEs) to perform route
computations in response to Path Computation Clients (PCCs) requests.
PCEP Extensions for PCE-initiated LSP Setup in a Stateful PCE Model
[RFC8231] describes a set of extensions to PCEP to enable active
control of MPLS-TE and GMPLS tunnels.
[RFC8281] describes the setup and tear down of PCE-initiated LSPs
under the active stateful PCE model, without the need for local
configuration on the PCC, thus allowing for a dynamic MPLS network
that is centrally controlled and deployed.
[RFC8283] introduces the architecture for PCE as a central
controller, examines the motivations and applicability for PCEP as a
southbound interface, and introduces the implications for the
protocol. [I-D.ietf-teas-pcecc-use-cases] describes the use cases
for the PCECC architecture.
[I-D.zhao-pce-pcep-extension-for-pce-controller] specify the PCEP
extension for the PCE as the central controller (PCECC). This
document extends the PCECC procedures for Segment Routing (SR).
Segment Routing (SR) technology leverage the source routing and
tunneling paradigms. A source node can choose a path without relying
on hop-by-hop signaling protocols such as LDP or RSVP-TE. Each path
is specified as a set of "segments" advertised by link- state routing
protocols (IS-IS or OSPF).
[I-D.ietf-spring-segment-routing] provides an introduction to SR
technology. The corresponding IS-IS and OSPF extensions are
Zhao, et al. Expires September 5, 2018 [Page 3]
Internet-Draft PCECC March 2018
specified in [I-D.ietf-isis-segment-routing-extensions] and
[I-D.ietf-ospf-segment-routing-extensions] , respectively.
A Segment Routed path (SR path) can be derived from an IGP Shortest
Path Tree (SPT). Segment Routed Traffic Engineering paths (SR-TE
paths) may not follow IGP SPT. Such paths may be chosen by a
suitable network planning tool and provisioned on the source node of
the SR-TE path.
It is possible to use a stateful PCE for computing one or more SR-TE
paths taking into account various constraints and objective
functions. Once a path is chosen, the stateful PCE can instantiate
an SR-TE path on a PCC using PCEP extensions specified in [RFC8281]
using the SR specific PCEP extensions described in
[I-D.ietf-pce-segment-routing].
PCECC may further use PCEP protocol for SR label distribution instead
of IGP extensions with some benefits.
The [I-D.zhao-pce-pcep-extension-for-pce-controller], specifies the
procedures and PCEP protocol extensions for using the PCE as one of
the the central controller components and user cases where LSPs are
calculated/setup/initiated and label forwarding entries are
downloaded on each hop along the path, through extending the existing
PCE architectures and PCEP.
This draft specify the procedures and PCEP protocol extensions for
using the PCE as the central controller for SR label distribution and
user cases where SR LSPs are calculated/setup/initiated/downloaded
through extending the existing PCE architectures and PCEP.
[Important Note - Note that this document achieves by extending the
new PCEP message defined in
[I-D.zhao-pce-pcep-extension-for-pce-controller]. The authors and WG
also debated on the use of existing PCEP messages. Section 5 defines
the first approach where as Appendix A defines the latter. The
authors are open to either of the approach and will follow the
direction of the WG.]
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.
Zhao, et al. Expires September 5, 2018 [Page 4]
Internet-Draft PCECC March 2018
2. Terminology
Terminologies used in this document is same as described in the draft
[RFC8283] and [I-D.ietf-teas-pcecc-use-cases].
3. PCECC SR
[I-D.ietf-pce-segment-routing] specifies extensions to PCEP that
allow a stateful PCE to compute, update or initiate SR-TE paths. An
ingress node of an SR-TE path appends all outgoing packets with a
list of MPLS labels (SIDs). This is encoded in SR-ERO subobject,
capable of carrying a label (SID) as well as the identity of the
node/adjacency label (SID).
The notion of segment and SID is defined in
[I-D.ietf-spring-segment-routing], which fits the MPLS architecture
[RFC3031] as the label which is managed by a local allocation process
of LSR (similarly to other MPLS signaling protocols)
[I-D.ietf-spring-segment-routing-mpls]. The SR information such as
node/adjacency label (SID) is flooded via IGP as specified in
[I-D.ietf-isis-segment-routing-extensions] and
[I-D.ietf-ospf-segment-routing-extensions].
As per [RFC8283], PCE as a central controller can allocate and
provision the node/adjacency label (SID) via PCEP.
Rest of the processing is similar to existing stateful PCE with SR
mechanism.
For the purpose of this document, it is assumed that label range to
be used by a PCE is set on both PCEP peers. Further, a global label
range is assumed to be set on all PCEP peers in the SR domain.
4. PCEP Requirements
Following key requirements for PCECC-SR should be considered when`
designing the PCECC based solution:
o PCEP speaker supporting this draft MUST have the capability to
advertise its PCECC-SR capability to its peers.
o PCEP speaker not supporting this draft MUST be able to reject
PCECC-SR related message with a reason code that indicates no
support for PCECC.
o PCEP SHOULD provide a means to update (or cleanup) the label- map
entry to the PCC.
Zhao, et al. Expires September 5, 2018 [Page 5]
Internet-Draft PCECC March 2018
o PCEP SHOULD provide a means to synchronize the SR labels between
PCE to PCC in PCEP messages.
5. Procedures for Using the PCE as the Central Controller (PCECC) in
Segment Routing
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
This document uses the same PCEP messages and its extenstions which
are described in [I-D.zhao-pce-pcep-extension-for-pce-controller] for
PCECC-SR as well.
PCEP messages PCRpt, PCInitiate, PCUpd are also used to send PCECC-SR
Reports, LSP setup and LSP update respectively.
PCLabelUpd message described in
[I-D.zhao-pce-pcep-extension-for-pce-controller] is used to download
or cleanup SR Label entry.
PCLabelRpt message described in
[I-D.zhao-pce-pcep-extension-for-pce-controller] is also used to
report the set of SR Label entries from PCC to PCE for which explicit
action is required from PCE (update or cleanup or do nothing for
these Label entries).
[Editor's Note: [I-D.zhao-pce-pcep-extension-for-pce-controller]
defines new messages PCLabelUpd and PCLabelRpt. The authors and WG
also debated on the use of existing PCEP messages. Further the
document also includes an appendix on how the existing messages can
be extended to add this functionality. WG needs to decide the final
direction i.e. new specific messages are needed or existing PCEP
messages can be extended. See See Appendix A to see the extension of
existing message for PCECC-SR functionality.]
5.3. PCECC Capability Advertisement
During PCEP Initialization Phase, PCEP Speakers (PCE or PCC)
advertise their support of PCECC extensions. A PCEP Speaker includes
the "PCECC Capability" sub-TLV, described in
[I-D.zhao-pce-pcep-extension-for-pce-controller].
Zhao, et al. Expires September 5, 2018 [Page 6]
Internet-Draft PCECC March 2018
A new S-bit is added in PCECC-CAPABILITY sub-TLV to indicate support
for PCECC-SR. A PCC MUST set S-bit in PCECC-CAPABILITY sub-TLV and
include SR-PCE-CAPABILITY sub-TLV ([I-D.ietf-pce-segment-routing]) in
OPEN Object (inside the the PATH-SETUP-TYPE-CAPABILITY TLV) to
support the PCECC SR extensions defined in this document. If S-bit
is set in PCECC-CAPABILITY sub-TLV and SR-PCE-CAPABILITY sub-TLV is
not advertised in OPEN Object, PCE SHOULD send a PCErr message with
Error-Type=19 (Invalid Operation) and Error-value=TBD(SR capability
was not advertised) and terminate the session.
5.4. PCEP session IP address and TEDB Router ID
PCE may construct its TEDB by participating in the IGP ([RFC3630] and
[RFC5305] for MPLS-TE; [RFC4203] and [RFC5307] for GMPLS). An
alternative is offered by BGP-LS [RFC7752] and
[I-D.dhodylee-pce-pcep-ls].
PCEP [RFC5440] speaker MAY use any IP address while creating a TCP
session. It is important to link the session IP address with the
Router ID in TEDB for successful PCECC operations.
During PCEP Initialization Phase, PCC SHOULD advertise the TE mapping
information. Thus a PCC includes the "Node Attributes TLV"
[I-D.dhodylee-pce-pcep-ls] with "IPv4/IPv6 Router-ID of Local Node",
in the OPEN Object for this purpose. [RFC7752] describes the usage
as auxiliary Router-IDs that the IGP might be using, e.g., for TE
purposes. If there are more than one auxiliary Router-ID of a given
type, then multiple TLVs are used to encode them.
If "IPv4/IPv6 Router-ID" TLV is not present, the TCP session IP
address is directly used for the mapping purpose.
5.5. LSP Operations
The PCEP messages pertaining to PCECC-SR MUST include PATH-SETUP-TYPE
TLV [I-D.ietf-pce-lsp-setup-type] in the SRP object to clearly
identify the PCECC-SR LSP is intended.
5.5.1. PCECC Segment Routing (SR)
Segment Routing (SR) as described in
[I-D.ietf-spring-segment-routing] depends on "segments" that are
advertised by Interior Gateway Protocols (IGPs). The SR-node
allocates and advertises the SID (node, adj etc) and flood via the
IGP. This document proposes a new mechanism where PCE allocates the
SID (label) centrally and uses PCEP to advertise the SID. In some
deployments PCE (and PCEP) are better suited than IGP because of
Zhao, et al. Expires September 5, 2018 [Page 7]
Internet-Draft PCECC March 2018
centralized nature of PCE and direct TCP based PCEP session to the
node.
5.5.1.1. PCECC SR Node/Prefix Label allocation
Each node (PCC) is allocated a node-SID (label) by the PCECC. The
PCECC sends PCLabelUpd to update the label map of each node to all
the nodes in the domain. The TE router ID is determined from the
TEDB or from "IPv4/IPv6 Router-ID" Sub-TLV
[I-D.dhodylee-pce-pcep-ls], in the OPEN Object Section 5.4.
Note: See Appendix A for how we could use PCInitiate message
instead.]
It is RECOMMENDED that PCEP session with PCECC SR capability to use a
different session IP address during TCP session establishment than
the node Router ID in TEDB, to make sure that the PCEP session does
not get impacted by the SR Node/Prefix Label maps (Section 5.4).
If a node (PCC) receives a PCLabelUpd message with a Label, out of
the range set aside for the global label, it MUST send a PCErr
message with Error-type=TBD (label download failure) and Error-
value=TBD (Label out of range) and MUST include the SRP object to
specify the error is for the corresponding label update
[I-D.zhao-pce-pcep-extension-for-pce-controller].
On receiving the label map, each node (PCC) uses the local
information to determine the next-hop and download the label
forwarding instructions accordingly. The PCLabelUpd message in this
case MUST NOT have LSP object but uses new FEC object.
Zhao, et al. Expires September 5, 2018 [Page 8]
Internet-Draft PCECC March 2018
+---------+ +-------+
|PCC | | PCE |
|192.0.2.3| +-------+
+------| | |
| PCC +---------+ |
| 192.0.2.2| | |
+------| | | |
|PCC +----------+ | |
|192.0.2.1| | | |
+---------+ | | |
| | | |
|<------- PCLabelUpd, FEC=192.0.2.1---------------- | Label Map
| | | Label=X | update
|Find | | |
|Nexthop|<------- PCLabelUpd, FEC=192.0.2.1-------- | Label Map
|locally| | Label=X | update
| | | |
| | |<--- PCLabelUpd, FEC=192.0.2.1---- | Label Map
| | | Label=X | update
| | | |
The forwarding behaviour and the end result is similar to IGP based
"Node-SID" in SR. Thus, from anywhere in the domain, it enforces the
ECMP-aware shortest-path forwarding of the packet towards the related
node.
PCE relies on the Node/Prefix Label cleanup using the same PCLabelUpd
message.
5.5.1.2. PCECC SR Adjacency Label allocation
[I-D.ietf-pce-segment-routing] extends PCEP to allow a stateful PCE
to compute and initiate SR-TE paths, as well as a PCC to request a
path subject to certain constraint(s) and optimization criteria in SR
networks.
For PCECC SR, apart from node-SID, Adj-SID is used where each
adjacency is allocated an Adj-SID (label) by the PCECC. The PCECC
sends PCLabelUpd to update the label map of each Adj to the
corresponding nodes in the domain. Each node (PCC) download the
label forwarding instructions accordingly. Similar to SR Node/Prefix
Label allocation, the PCLabelUpd message in this case MUST NOT have
LSP object but uses new FEC object. Note: See Appendix A for how we
could use PCInitiate message instead.]
Zhao, et al. Expires September 5, 2018 [Page 9]
Internet-Draft PCECC March 2018
+---------+ +-------+
|PCC | | PCE |
|192.0.2.3| +-------+
+------| | |
| PCC +---------+ |
| 192.0.2.2| | |
+------| | | |
|PCC +----------+ | |
|192.0.2.1| | | |
+---------+ | | |
| | | |
|<------ PCLabelUpd, FEC=192.0.2.1 / ------------ | Label Map
| | | 192.0.2.2 | update
| | | Label=A |
| | | |
| |<----- PCLabelUpd, FEC=192.0.2.2------- | Label Map
| | | 192.0.2.1 | update
| | | Label=B |
| | | |
The forwarding behavior and the end result is similar to IGP based
"Adj-SID" in SR.
The Path Setup Type for segment routing MUST be set for PCECC SR (see
Section 7.2). All PCEP procedures and mechanism are similar to
[I-D.ietf-pce-segment-routing].
PCE relies on the Adj label cleanup using the same PCLabelUpd
message.
5.5.1.3. Redundant PCEs
[I-D.litkowski-pce-state-sync] describes synchronization mechanism
between the stateful PCEs. The SR Labels allocated by a PCE should
also be synchronized among PCEs for PCECC SR state synchronization.
Note that the SR labels are downloaded independent to the PCECC LSP,
and remains intact till any topology change. The redundant PCEs MUST
have a common view of all SR labels allocated in the domain.
Incase the session to the PCE that allocated the SR labels is down,
similar to the LSP re-delegation mechanims, the SR labels are re-
delegated to a redundant PCE using the PCLabelRpt message. This is
done so that the SR labels remains intact and cosntant in case of
session disconnect.
Zhao, et al. Expires September 5, 2018 [Page 10]
Internet-Draft PCECC March 2018
5.5.1.4. Session Termination
[I-D.zhao-pce-pcep-extension-for-pce-controller] describes the action
needed for label provisioned for the Basic PCECC LSP on this
terminated session. Similarly actions should be applied for SR
Labels as well.
Additionally, if PCC has any alternate PCEP session with another PCE,
then PCC MUST deligate the SR labels of this session to this
alternate PCE in a sequence of PCLabelRpt message. PCE can accept it
and can send PCLabelUpd message to update or clean the label.
Extensions for PCLabelUpd and PCLabelRpt message for SR label are
described in Section 6.1.
5.5.1.5. LABEL-DB Synchronization
[I-D.zhao-pce-pcep-extension-for-pce-controller] describes LABEL-DB
Synchronization procedures needed for the labels provisioned for the
Basic PCECC LSP. Same procedures should be applied for SR labels as
well.
See [I-D.palle-pce-controller-labeldb-sync] for the optimizations for
LABEL-DB synchronization procedure.
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.
6.1. Label Operations
[Editor's Note: [I-D.zhao-pce-pcep-extension-for-pce-controller]
defines new messages PCLabelUpd and PCLabelRpt. The authors and WG
also debated on the use of existing PCEP messages. Further the
document also includes an appendix on how the existing messages can
be extended to add this functionality. WG needs to decide the final
direction i.e. new specific messages are needed or existing PCEP
messages can be extended. See See Appendix A to see the extension of
existing message for PCECC-SR functionality.]
Zhao, et al. Expires September 5, 2018 [Page 11]
Internet-Draft PCECC March 2018
6.1.1. The PCLabelUpd message
Label Update Message (PCLabelUpd) defined in
[I-D.zhao-pce-pcep-extension-for-pce-controller] is extended to
update the label map at the PCC.
The format of the extended PCLabelUpd message is as follows:
<PCLabelUpd Message> ::= <Common Header>
<pce-label-update-list>
Where:
<pce-label-update-list> ::= <pce-label-update>
[<pce-label-update-list>]
<pce-label-update> ::= (<pce-label-download>|<pce-label-map>)
Where:
<pce-label-map> ::= <SRP>
<LABEL>
<FEC>
<pce-label-download> is defined in
[I-D.zhao-pce-pcep-extension-for-pce-controller].
The FEC object is defined in Section 7.3. Either FEC object or LSP
object defined in [I-D.zhao-pce-pcep-extension-for-pce-controller] is
mandatory in PCLabelUpd message. The FEC object encodes the Node and
Adjacency information of the Label Map.
6.1.2. The PCLabelRpt message
Label Report Message (PCLabelRpt) defined in
[I-D.zhao-pce-pcep-extension-for-pce-controller] is extended to
report or delegate the label map to PCE.
The format of the PCLabelRpt message is as follows:
Zhao, et al. Expires September 5, 2018 [Page 12]
Internet-Draft PCECC March 2018
<PCLabelRpt Message> ::= <Common Header>
<pce-label-report-list>
Where:
<pce-label-report-list> ::= <pce-label-report>
[<pce-label-report-list>]
<pce-label-report> ::= (<pce-label-delegate>|<pce-label-map>)
Where:
<pce-label-map> ::= <SRP>
<LABEL>
<FEC>
<pce-label-delegate> is defined in
[I-D.zhao-pce-pcep-extension-for-pce-controller].
The FEC object is defined in Section 7.3. Either FEC object or LSP
object defined in [I-D.zhao-pce-pcep-extension-for-pce-controller] is
mandatory in PCLabelRpt message. The FEC object encodes the Node and
Adjacency information of the Label Map.
7. PCEP Objects
7.1. OPEN Object
7.1.1. PCECC Capability sub-TLV
[I-D.zhao-pce-pcep-extension-for-pce-controller] defined the PCECC-
CAPABILITY TLV.
A new S-bit is defined in PCECC-CAPABILITY sub-TLV for PCECC-SR:
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=TBD | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |S|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Zhao, et al. Expires September 5, 2018 [Page 13]
Internet-Draft PCECC March 2018
S (PCECC-SR-CAPABILITY - 1 bit): If set to 1 by a PCEP speaker, it
indicates that the PCEP speaker is capable for PCECC-SR capability
and PCE would allocate node and Adj label on this session.
7.2. PATH-SETUP-TYPE TLV
The PATH-SETUP-TYPE TLV is defined in [I-D.ietf-pce-lsp-setup-type].
PST = 1 (defined in [I-D.ietf-pce-segment-routing]) can be reused
when Path is setup via PCECC SR mode.
On a PCRpt/PCUpd/PCInitiate message, the PST=1 indicates that this
LSP was setup via a SR based mechanism where either the labels are
allocated by PCE via PCECC mechanism or advertised by IGP. For the
label map download or cleanup the PST type is set to PCECC as per
[I-D.zhao-pce-pcep-extension-for-pce-controller].
7.3. FEC Object
The FEC Object is used to specify the FEC information and MAY be
carried within PCLabelUpd message.
FEC Object-Class is TBD.
FEC Object-Type is 1 'IPv4 Node ID'.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Node ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
FEC Object-Type is 2 'IPv6 Node ID'.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// IPv6 Node ID (16 bytes) //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
FEC Object-Type is 3 'IPv4 Adjacency'.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Zhao, et al. Expires September 5, 2018 [Page 14]
Internet-Draft PCECC March 2018
| Local IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
FEC Object-Type is 4 'IPv6 Adjacency'.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Local IPv6 address (16 bytes) //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Remote IPv6 address (16 bytes) //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
FEC Object-Type is 5 'Unnumbered Adjacency with IPv4 NodeIDs'.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Node-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Node-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The FEC objects are as follows:
IPv4 Node ID: where IPv4 Node ID is specified as an IPv4 address of
the Node. FEC Object-type is 1, and the Object-Length is 4 in this
case.
IPv6 Node ID: where IPv6 Node ID is specified as an IPv6 address of
the Node. FEC Object-type is 2, and the Object-Length is 16 in this
case.
IPv4 Adjacency: where Local and Remote IPv4 address is specified as
pair of IPv4 address of the adjacency. FEC Object-type is 3, and the
Object-Length is 8 in this case.
Zhao, et al. Expires September 5, 2018 [Page 15]
Internet-Draft PCECC March 2018
IPv6 Adjacency: where Local and Remote IPv6 address is specified as
pair of IPv6 address of the adjacency. FEC Object-type is 4, and the
Object-Length is 32 in this case.
Unnumbered Adjacency with IPv4 NodeID: where a pair of Node ID /
Interface ID tuples is used. FEC Object-type is 5, and the Object-
Length is 16 in this case.
8. Security Considerations
The security considerations described in
[I-D.zhao-pce-pcep-extension-for-pce-controller] apply to the
extensions described in this document.
9. Manageability Considerations
9.1. Control of Function and Policy
A PCE or PCC implementation SHOULD allow to configure to enable/
disable PCECC SR capability as a global configuration.
9.2. Information and Data Models
[RFC7420] describes the PCEP MIB, this MIB can be extended to get the
PCECC SR capability status.
The PCEP YANG module [I-D.ietf-pce-pcep-yang] could be extended to
enable/disable PCECC SR capability.
9.3. 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].
9.4. 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].
9.5. Requirements On Other Protocols
PCEP extensions defined in this document do not put new requirements
on other protocols.
Zhao, et al. Expires September 5, 2018 [Page 16]
Internet-Draft PCECC March 2018
9.6. Impact On Network Operations
PCEP implementation SHOULD allow a limit to be placed on the rate of
PCLabelUpd messages sent by PCE and processed by PCC. It SHOULD also
allow sending a notification when a rate threshold is reached.
10. IANA Considerations
10.1. PCECC-CAPABILITY TLV
[I-D.zhao-pce-pcep-extension-for-pce-controller] defines the PCECC-
CAPABILITY TLV and requests that IANA creates a registry to manage
the value of the PCECC-CAPABILITY TLV's Flag field. IANA is
requested to allocate a new bit in the PCECC-CAPABILITY TLV Flag
Field registry, as follows:
Bit Description Reference
31 S((PCECC-SR-CAPABILITY)) This document
10.2. PCEP Object
IANA is requested to allocate new registry for FEC PCEP object.
Object-Class Value Name Reference
TBD FEC This document
Object-Type : 1 IPv4 Node ID
Object-Type : 2 IPv6 Node ID
Object-Type : 3 IPv4 Adjacency
Object-Type : 4 IPv6 Adjacency
Object-Type : 5 Unnumbered Adjacency
with IPv4 NodeID
10.3. 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
---------- -------
19 Invalid operation.
Error-value = TBD : SR capability was
not advertised
Zhao, et al. Expires September 5, 2018 [Page 17]
Internet-Draft PCECC March 2018
11. Acknowledgments
We would like to thank Robert Tao, Changjing Yan, Tieying Huang and
Avantika for their useful comments and suggestions.
12. References
12.1. 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>.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, DOI 10.17487/RFC5305, October
2008, <https://www.rfc-editor.org/info/rfc5305>.
[RFC5307] Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions
in Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 5307, DOI 10.17487/RFC5307, October 2008,
<https://www.rfc-editor.org/info/rfc5307>.
[RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005,
<https://www.rfc-editor.org/info/rfc4203>.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
DOI 10.17487/RFC3630, September 2003,
<https://www.rfc-editor.org/info/rfc3630>.
Zhao, et al. Expires September 5, 2018 [Page 18]
Internet-Draft PCECC March 2018
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016,
<https://www.rfc-editor.org/info/rfc7752>.
[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>.
[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>.
12.2. Informative References
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001,
<https://www.rfc-editor.org/info/rfc3031>.
[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., Ke, Z., Fang, L., Zhou,
C., Communications, T., and A. Rachitskiy, "The Use Cases
for Using PCE as the Central Controller(PCECC) of LSPs",
draft-ietf-teas-pcecc-use-cases-01 (work in progress), May
2017.
[I-D.ietf-pce-lsp-setup-type]
Sivabalan, S., Tantsura, J., Minei, I., Varga, R., and J.
Hardwick, "Conveying path setup type in PCEP messages",
draft-ietf-pce-lsp-setup-type-08 (work in progress),
January 2018.
Zhao, et al. Expires September 5, 2018 [Page 19]
Internet-Draft PCECC March 2018
[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-06 (work in progress), January 2018.
[I-D.zhao-pce-pcep-extension-for-pce-controller]
Zhao, Q., Li, Z., Dhody, D., Karunanithi, S., Farrel, A.,
and C. Zhou, "PCEP Procedures and Protocol Extensions for
Using PCE as a Central Controller (PCECC) of LSPs", draft-
zhao-pce-pcep-extension-for-pce-controller-06 (work in
progress), October 2017.
[I-D.ietf-pce-segment-routing]
Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "PCEP Extensions for Segment Routing",
draft-ietf-pce-segment-routing-11 (work in progress),
November 2017.
[I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,
Gredler, H., Litkowski, S., Decraene, B., and J. Tantsura,
"IS-IS Extensions for Segment Routing", draft-ietf-isis-
segment-routing-extensions-15 (work in progress), December
2017.
[I-D.ietf-ospf-segment-routing-extensions]
Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", draft-ietf-ospf-segment-
routing-extensions-24 (work in progress), December 2017.
[I-D.litkowski-pce-state-sync]
Litkowski, S., Sivabalan, S., and D. Dhody, "Inter
Stateful Path Computation Element communication
procedures", draft-litkowski-pce-state-sync-02 (work in
progress), August 2017.
[I-D.dhodylee-pce-pcep-ls]
Dhody, D., Lee, Y., and D. Ceccarelli, "PCEP Extension for
Distribution of Link-State and TE Information.", draft-
dhodylee-pce-pcep-ls-09 (work in progress), January 2018.
[I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing
Architecture", draft-ietf-spring-segment-routing-15 (work
in progress), January 2018.
Zhao, et al. Expires September 5, 2018 [Page 20]
Internet-Draft PCECC March 2018
[I-D.ietf-spring-segment-routing-mpls]
Bashandy, A., Filsfils, C., Previdi, S., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing with MPLS
data plane", draft-ietf-spring-segment-routing-mpls-12
(work in progress), February 2018.
[I-D.palle-pce-controller-labeldb-sync]
Palle, U., Dhody, D., and S. Karunanithi, "LABEL-DB
Synchronization Procedures for a PCE as a central
controller(PCECC)", draft-palle-pce-controller-labeldb-
sync-02 (work in progress), October 2017.
Zhao, et al. Expires September 5, 2018 [Page 21]
Internet-Draft PCECC March 2018
Appendix A. Using existing PCEP message
This is a temporary section added to this document, till the time a
decision on the use of new messages v/s extending existing message is
resolved. This section should be removed before the final
publication of the document.
The PCInitiate message can be used to download or remove the labels -
<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-label-download>|
<PCE-initiated-label-map>)
<PCE-initiated-lsp-label-download> ::= <SRP>
<LSP>
<label-list>
<label-list> ::= <LABEL>
[<label-list>]
<PCE-initiated-label-map> ::= <SRP>
<LABEL>
<FEC>
Where:
<PCE-initiated-lsp-instantiation> and
<PCE-initiated-lsp-deletion> are as per
[RFC8281].
The LSP and SRP object is defined in [RFC8231].
The PCRpt message can be used to report the labels that were
allocated by the PCE, to be used during the state synchronization
phase.
Zhao, et al. Expires September 5, 2018 [Page 22]
Internet-Draft PCECC March 2018
The format of the PCRpt message is as follows:
<PCRpt Message> ::= <Common Header>
<state-report-list>
Where:
<state-report-list> ::= <state-report>[<state-report-list>]
<state-report> ::= (<lsp-state-report>|
<pce-label-report>)
<lsp-state-report> ::= [<SRP>]
<LSP>
<path>
<pce-label-report> ::= (<pce-label-delegate>|
<pce-label-map>)
<pce-label-delegate> ::= <SRP>
<LSP>
<label-list>
<label-list> ::= <LABEL>
[<label-list>]
<pce-label-map> ::= <SRP>
<LABEL>
<FEC>
Where:
<path> is as per [RFC8231] and the LSP and SRP object are
also defined in [RFC8231].
The procedure for LSP-DB synchronization would also change, in-case
we use the existing message. It will be the PCCs that would first
report all the labels downloaded by the PCE during the state
synchronization from PCC towards PCE, and then in case of any
discrepancies PCE would use the PCInitiate message to add/remove
labels.
Appendix B. Contributor Addresses
Zhao, et al. Expires September 5, 2018 [Page 23]
Internet-Draft PCECC March 2018
Udayasree Palle
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
EMail: udayasreereddy@gmail.com
Katherine Zhao
Huawei Technologies
2330 Central Expressway
Santa Clara, CA 95050
USA
EMail: katherine.zhao@huawei.com
Boris Zhang
Telus Ltd.
Toronto
Canada
EMail: boris.zhang@telus.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
Zhao, et al. Expires September 5, 2018 [Page 24]
Internet-Draft PCECC March 2018
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
Chao Zhou
Cisco Systems
EMail: choa.zhou@cisco.com
Zhao, et al. Expires September 5, 2018 [Page 25]