PCE Working Group Q. Zhao
Internet-Draft Z. Li
Intended status: Standards Track M. Negi
Expires: January 9, 2020 Huawei Technologies
C. Zhou
Cisco Systems
July 8, 2019
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
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
when a PCE-based controller is also responsible for configuring the
forwarding actions on the routers, in addition to computing the paths
for packet flows in a segment routing network and telling the edge
routers what instructions to attach to packets as they enter the
network.
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Status of This Memo
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This Internet-Draft will expire on January 9, 2020.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. PCECC SR . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. PCEP Requirements . . . . . . . . . . . . . . . . . . . . . . 6
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 . . . . . . . . . . . . . 7
5.4. PCEP session IP address and TEDB Router ID . . . . . . . 7
5.5. LSP Operations . . . . . . . . . . . . . . . . . . . . . 8
5.5.1. PCECC Segment Routing (SR) . . . . . . . . . . . . . 8
5.5.1.1. PCECC SR Node/Prefix SID allocation . . . . . . . 8
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5.5.1.2. PCECC SR Adjacency Label allocation . . . . . . . 10
5.5.1.3. Redundant PCEs . . . . . . . . . . . . . . . . . 12
5.5.1.4. Re Delegation and Cleanup . . . . . . . . . . . . 12
5.5.1.5. Synchronization of Label Allocations . . . . . . 13
5.5.1.6. PCC Based Allocations . . . . . . . . . . . . . . 13
5.5.1.7. Binding SID . . . . . . . . . . . . . . . . . . . 13
6. PCEP messages . . . . . . . . . . . . . . . . . . . . . . . . 14
6.1. Central Control Instructions . . . . . . . . . . . . . . 14
6.1.1. The PCInitiate message . . . . . . . . . . . . . . . 14
6.1.2. The PCRpt message . . . . . . . . . . . . . . . . . . 15
7. PCEP Objects . . . . . . . . . . . . . . . . . . . . . . . . 16
7.1. OPEN Object . . . . . . . . . . . . . . . . . . . . . . . 16
7.1.1. PCECC Capability sub-TLV . . . . . . . . . . . . . . 16
7.2. PATH-SETUP-TYPE TLV . . . . . . . . . . . . . . . . . . . 17
7.3. CCI Object . . . . . . . . . . . . . . . . . . . . . . . 17
7.4. FEC Object . . . . . . . . . . . . . . . . . . . . . . . 19
8. Implementation Status . . . . . . . . . . . . . . . . . . . . 21
8.1. Huawei's Proof of Concept based on ONOS . . . . . . . . . 21
9. Security Considerations . . . . . . . . . . . . . . . . . . . 22
10. Manageability Considerations . . . . . . . . . . . . . . . . 22
10.1. Control of Function and Policy . . . . . . . . . . . . . 22
10.2. Information and Data Models . . . . . . . . . . . . . . 22
10.3. Liveness Detection and Monitoring . . . . . . . . . . . 22
10.4. Verify Correct Operations . . . . . . . . . . . . . . . 23
10.5. Requirements On Other Protocols . . . . . . . . . . . . 23
10.6. Impact On Network Operations . . . . . . . . . . . . . . 23
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
11.1. PCECC-CAPABILITY sub-TLV . . . . . . . . . . . . . . . . 23
11.2. New Path Setup Type Registry . . . . . . . . . . . . . . 23
11.3. PCEP Object . . . . . . . . . . . . . . . . . . . . . . 24
11.4. PCEP-Error Object . . . . . . . . . . . . . . . . . . . 24
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 24
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
13.1. Normative References . . . . . . . . . . . . . . . . . . 24
13.2. Informative References . . . . . . . . . . . . . . . . . 26
Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 31
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].
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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
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.
[I-D.ietf-pce-pcep-extension-for-pce-controller] 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.
Segment Routing (SR) technology leverages 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). [RFC8402] provides an introduction to SR
architecture. The corresponding IS-IS and OSPF extensions are
specified in [I-D.ietf-isis-segment-routing-extensions] and
[I-D.ietf-ospf-segment-routing-extensions] , respectively. It relies
on a series of forwarding instructions being placed in the header of
a packet. The segment routing architecture supports operations that
can be used to steer packet flows in a network, thus providing a form
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of traffic engineering. [I-D.ietf-pce-segment-routing] specify the
SR specific PCEP extensions.
PCECC may further use PCEP protocol for SR SID (Segment Identifier)
distribution on the SR nodes with some benefits.
This document specifies the procedures and PCEP protocol extensions
when a PCE-based controller is also responsible for configuring the
forwarding actions on the routers (SR SID distribution in this case),
in addition to computing the paths for packet flows in a segment
routing network and telling the edge routers what instructions to
attach to packets as they enter the network.
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] 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 [RFC8402], 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/prefix/adjacency label (SID) via PCEP.
Rest of the processing is similar to existing stateful PCE with SR
mechanism.
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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. 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 5.5.1.6.
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 procedures MUST provide a means to update (or cleanup) the
label- map entry to the PCC.
o PCEP procedures SHOULD provide a means to synchronize the SR
labels allocations between PCE to PCC in the PCEP messages.
o PCEP procedures MAY allow for PCC based label allocations.
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 extensions which
are described in [I-D.ietf-pce-pcep-extension-for-pce-controller] for
PCECC-SR as well.
PCEP messages PCRpt, PCInitiate, PCUpd are also used to send LSP
Reports, LSP setup and LSP update respectively. The extended
PCInitiate message described in
[I-D.ietf-pce-pcep-extension-for-pce-controller] is used to download
or cleanup central controller's instructions (CCIs) (SR SID in scope
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of this document). The extended PCRpt message described in
[I-D.ietf-pce-pcep-extension-for-pce-controller] is also used to
report the CCIs (SR SIDs) from PCC to PCE.
[I-D.ietf-pce-pcep-extension-for-pce-controller] specify an object
called CCI for the encoding of central controller's instructions.
This document extends the CCI by defining a new object-type for
segment routing. The PCEP messages are extended in this document to
handle the PCECC operations for SR.
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.ietf-pce-pcep-extension-for-pce-controller].
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.
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5.5. LSP Operations
The PCEP messages pertaining to PCECC-SR MUST include PATH-SETUP-TYPE
TLV [RFC8408] with PST=TBD 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 [RFC8402] 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/index/SID) centrally and uses PCEP to advertise the
SID. In some deployments PCE (and PCEP) are better suited than IGP
because of centralized nature of PCE and direct TCP based PCEP
session to the node.
5.5.1.1. PCECC SR Node/Prefix SID allocation
Each node (PCC) is allocated a node-SID by the PCECC. The PCECC
sends PCInitiate message 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.
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 PCInitiate message with a CCI encoding a
SID, out of the range set aside for the SRGB, it MUST send a PCErr
message with Error-type=TBD (PCECC failure) and Error-value=TBD (SID
out of range) and MUST include the SRP object to specify the error is
for the corresponding label update via PCInitiate message.
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 PCInitiate message in this
case MUST NOT have LSP object but uses the new FEC object defined in
this document.
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+---------+ +-------+
|PCC | | PCE |
|192.0.2.3| +-------+
+------| | |
| PCC +---------+ |
| 192.0.2.2| | |
+------| | | |
|PCC +----------+ | |
|192.0.2.1| | | |
+---------+ | | |
| | | |
|<------- PCInitiate, FEC=192.0.2.1---------------- | Label Map
| | | CC-ID=X | update
|------- PCRpt,CC-ID=X --------------------------->| CCI
|Find | | |
|Nexthop|<------- PCInitiate, FEC=192.0.2.1-------- | Label Map
|locally| | CC-ID=Y | update
| |----- PCRpt,CC-ID=Y -------------------->| CCI
| | | |
| | |<--- PCInitiate, FEC=192.0.2.1---- | Label Map
| | | CC-ID=Z | update
| | |---- PCRpt,CC-ID=Z -------------->| CCI
| | | |
The forwarding behavior 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 PCInitiate
message.
The above example Figure 1 depict FEC and PCEP speakers that uses
IPv4 address. Similarly IPv6 address (such as 2001:DB8::1) can be
used during PCEP session establishment as well in FEC object as
described in this specification.
In case where the label allocation are made by the PCC itself (see
Section 5.5.1.6), the PCE could still 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 |
|192.0.2.3| +-------+
+------| | |
| PCC +---------+ |
| 192.0.2.2| | |
+------| | | |
|PCC +----------+ | |
|192.0.2.1| | | |
+---------+ | | |
| | | |
|<------- PCInitiate, FEC=192.0.2.1---------------- | Label Map
| | | CC-ID=X,C=1 | request
|------- PCRpt,CC-ID=X,Label ---------------------->| CCI
|Find | | |
|Nexthop|<------- PCInitiate, FEC=192.0.2.1-------- | Label Map
|locally| | CC-ID=Y,C=0,Label | update
| |----- PCRpt,CC-ID=Y -------------------->| CCI
| | | |
| | |<--- PCInitiate, FEC=192.0.2.1---- | Label Map
| | | CC-ID=Z,C=0,Label | update
| | |---- PCRpt,CC-ID=Z -------------->| CCI
| | | |
It should be noted that in this example, the request is made to the
node 192.0.2.1 with C bit set in the CCI object to indicate that the
allocation needs to be done by this PCC and it responds with the
allocated label/SID to the PCE. The PCE would further inform the
other PCCs in the network about the allocation without setting the C
bit.
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 by the PCECC. The PCECC sends
PCInitiate message 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 PCInitiate message in this case MUST NOT have
LSP object but uses the new FEC object defined in this document.
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+---------+ +-------+
|PCC | | PCE |
|192.0.2.3| +-------+
+------| | |
| PCC +---------+ |
| 192.0.2.2| | |
+------| | | |
|PCC +----------+ | |
|192.0.2.1| | | |
+---------+ | | |
| | | |
|<------ PCInitiate, FEC=198.51.100.1 / --------- | Label Map
| | | 198.51.100.2 | update
| | | CC-ID=A | CCI
|------- PCRpt,CC-ID=A ------------------------->|
| | | |
| |<----- PCInitiate, FEC=198.51.100.2---- | Label Map
| | | 198.51.100.1 | update
| | | CC-ID=B | CCI
| |----- PCRpt,CC-ID=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 =
TBD (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 PCInitiate
message.
The above example Figure 3 depict FEC and PCEP speakers that uses
IPv4 address. Similarly IPv6 address (such as 2001:DB8::1,
2001:DB8::2) can be used during PCEP session establishment as well in
FEC object as described in this specification.
In case where the label allocation are made by the PCC itself (see
Section 5.5.1.6), the PCE could still 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 |
|192.0.2.3| +-------+
+------| | |
| PCC +---------+ |
| 192.0.2.2| | |
+------| | | |
|PCC +----------+ | |
|192.0.2.1| | | |
+---------+ | | |
| | | |
|<------ PCInitiate, FEC=198.51.100.1------------ | Label Map
| | | 198.51.100.2 | request
| | | CC-ID=A,C=1 | CCI
|------- PCRpt,CC-ID=A,Label -------------------->|
| | | |
| |<----- PCInitiate, FEC=198.51.100.2---- | Label Map
| | | 198.51.100.1 | request
| | | CC-ID=B,C=1 | CCI
| |----- PCRpt,CC-ID=B,Label------------->|
| | | |
In this example the request is made to the node 192.0.2.1 with C bit
set in the CCI object to indicate that the allocation needs to be
done by this PCC for the adjacency (198.51.100.1 - 198.51.100.2) and
it responds with the allocated label/SID to the PCE. Similarly,
another request is made to the node 192.0.2.2 with C bit set in the
CCI object to indicate that the allocation needs to be done by this
PCC for the adjacency (198.51.100.2 - 198.51.100.1).
5.5.1.3. Redundant PCEs
[I-D.litkowski-pce-state-sync] describes synchronization mechanism
between the stateful PCEs. The SR SIDs allocated by a PCE MUST also
be synchronized among PCEs for PCECC SR state synchronization. Note
that the SR SIDs are independent to the PCECC-SR LSP, and remains
intact till any topology change. The redundant PCEs MUST have a
common view of all SR SIDs allocated in the domain.
5.5.1.4. Re Delegation and Cleanup
[I-D.ietf-pce-pcep-extension-for-pce-controller] describes the action
needed for CCIs for the Basic PCECC LSP on this terminated session.
Similarly actions should be applied for the SR SID as well.
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5.5.1.5. Synchronization of Label Allocations
[I-D.ietf-pce-pcep-extension-for-pce-controller] describes the
synchronization of Central Controller's Instructions (CCI) via LSP
state synchronization as described in [RFC8231] and [RFC8232]. Same
procedures should be applied for SR SIDs as well.
5.5.1.6. PCC Based Allocations
The PCE can request the PCC to allocate the label/SID 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 SID/Label/Index and would report to the PCE using
the PCRpt message.
If the value of the SID/Label/Index 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 SID/Label/Index is 'n' and the C flag is set in the CCI
object, it indicates that the PCE requests a specific value 'n' for
the SID/Label/Index. 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 = TBD ("PCECC failure") and Error Value
= TBD ("Invalid CCI"). If the value of the the SID/Label/Index in
the CCI object is valid, but the PCC is unable to allocate it, it
MUST send a PCErr message with Error-Type = TBD ("PCECC failure") and
Error Value = TBD ("Unable to allocate the specified CCI").
If the PCC wishes to withdrawn or modify the previously assigned
label/SID, it MUST send a PCRpt message without any SID/Label/Index
or with the SID/Label/Index 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.
5.5.1.7. Binding SID
A PCE as a central controller can allocate and provision the
node/prefix/adjacency label (SID) via PCEP. One such SID is binding
SID as described in [I-D.sivabalan-pce-binding-label-sid], the PCECC
mechanism can also be used to allocate the binding SID as described
in this section.
A procedure for binding label/SID allocation is described in
[I-D.ietf-pce-pcep-extension-for-pce-controller] and is applicable
for all path setup types (including SR paths).
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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. Central Control Instructions
6.1.1. The PCInitiate message
The PCInitiate Message defined in [RFC8281] and extended in
[I-D.ietf-pce-pcep-extension-for-pce-controller] is further extended
to support SR based central control instructions.
The format of the extended PCInitiate message is as follows:
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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>)|
(<FEC>
<CCI>)
<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 to distribute SR SIDs, the SRP, FEC
and CCI objects MUST be present. The error handling for missing SRP
or CCI object is as per
[I-D.ietf-pce-pcep-extension-for-pce-controller]. If the FEC object
is missing, the receiving PCC MUST send a PCErr message with Error-
type=6 (Mandatory Object missing) and Error-value=TBD (FEC object
missing).
To cleanup the SRP object must set the R (remove) bit.
6.1.2. The PCRpt message
The PCRpt message can be used to report the SR instructions received
from the central controller (PCE) during the state synchronization
phase.
The format of the PCRpt message is as follows:
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<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>)|
(<FEC>
<CCI>)
<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 label map allocations, the
FEC and CCI objects MUST be present. The error handling for CCI
object is as per [I-D.ietf-pce-pcep-extension-for-pce-controller].
If the FEC object is missing, the receiving PCC MUST send a PCErr
message with Error-type=6 (Mandatory Object missing) and Error-
value=TBD (FEC object missing).
7. PCEP Objects
7.1. OPEN Object
7.1.1. PCECC Capability sub-TLV
[I-D.ietf-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:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |S|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 [RFC8408]. PST = TBD is used
when Path is setup via PCECC SR mode.
On a PCRpt/PCUpd/PCInitiate message, the PST=TBD indicates that this
LSP was setup via a PCECC-SR based mechanism where either the SIDs
were allocated/instructed by PCE via PCECC mechanism.
7.3. CCI Object
The Central Control Instructions (CCI) Object is used by the PCE to
specify the forwarding instructions is defined in
[I-D.ietf-pce-pcep-extension-for-pce-controller]. This document
defines another object-type for SR purpose.
CCI Object-Type is TBD for SR as below -
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MT-ID | Algorithm | Flags |C|N|E|V|L|O|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// SID/Label/Index (variable) //
+---------------------------------------------------------------+
| |
// Optional TLV //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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The field CC-ID is as described in
[I-D.ietf-pce-pcep-extension-for-pce-controller]. Following new
fields are defined for CCI Object-Type TBD -
MT-ID: Multi-Topology ID (as defined in [RFC4915]).
Algorithm: Single octet identifying the algorithm the SID is
associated with. See [I-D.ietf-ospf-segment-routing-extensions].
Flags: is used to carry any additional information pertaining to the
CCI. The O bit was defined in
[I-D.ietf-pce-pcep-extension-for-pce-controller], this document
further defines following bits-
* L-Bit (Local/Global): If set, then the value/index carried by
the CCI object has local significance. If not set, then the
value/index carried by this object has global significance.
* V-Bit (Value/Index): If set, then the CCI carries an absolute
value. If not set, then the CCI carries an index.
* E-Bit (Explicit-Null): If set, any upstream neighbor of the
node that advertised the SID MUST replace the SID with the
Explicit-NULL label (0 for IPv4) before forwarding the packet.
* N-Bit (No-PHP): If set, then the penultimate hop MUST NOT pop
the SID before delivering packets to the node that advertised
the SID.
* 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 SR label/ID space. A
PCC would set this bit to indicate that it has allocated the
CC-ID and report it to the PCE.
SID/Label/Index: According to the V and L flags, it contains either:
A 32-bit index defining the offset in the SID/Label space
advertised by this router.
A 24-bit label where the 20 rightmost bits are used for
encoding the label value.
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7.4. FEC Object
The FEC Object is used to specify the FEC information and MAY be
carried within PCInitiate or PCRpt 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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) //
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| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
FEC Object-Type is 6 'Linklocal 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 octets) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Remote IPv6 address (16 octets) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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.
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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.
Linklocal IPv6 Adjacency: where a pair of (global IPv6 address,
interface ID) tuples is used. FEC object-type is 6, and the Object-
Length is 40 in this case.
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
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
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o Description: PCEP as a southbound plugin was added to ONOS. To
support PCECC-SR, 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
[I-D.ietf-pce-pcep-extension-for-pce-controller] apply to the
extensions described in this document.
As per [RFC8231], 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] (unless explicitly set aside in
[RFC8253]).
10. Manageability Considerations
10.1. Control of Function and Policy
A PCE or PCC implementation SHOULD allow to configure to enable/
disable PCECC SR capability as a global configuration.
10.2. 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.
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].
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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 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.
11. IANA Considerations
11.1. PCECC-CAPABILITY sub-TLV
[I-D.ietf-pce-pcep-extension-for-pce-controller] defines the PCECC-
CAPABILITY sub-TLV and requests that IANA creates a registry to
manage the value of the PCECC-CAPABILITY sub-TLV's 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
IANA is requested to allocate a new bit in the PCECC-CAPABILITY sub-
TLV Flag Field registry, as follows:
Bit Description Reference
31 S((PCECC-SR-CAPABILITY)) This document
11.2. 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:
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Value Description Reference
TBD Traffic engineering path is This document
setup using PCECC-SR mode
11.3. PCEP Object
IANA is requested to allocate new code-point for the new FEC object
in "PCEP Objects" sub-registry as follows:
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
Object-Type : 6 Linklocal IPv6 Adjacency
11.4. 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
---------- -------
6 Mandatory Object missing.
Error-value = TBD : FEC object missing
19 Invalid operation.
Error-value = TBD : SR capability was
not advertised
12. Acknowledgments
We would like to thank Robert Tao, Changjing Yan, Tieying Huang and
Avantika for their useful comments and suggestions.
13. References
13.1. Normative References
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[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>.
[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>.
[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>.
[RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
RFC 4915, DOI 10.17487/RFC4915, June 2007,
<https://www.rfc-editor.org/info/rfc4915>.
[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>.
[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>.
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[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>.
[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>.
[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>.
[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>.
[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
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[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>.
[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>.
[RFC8232] Crabbe, E., Minei, I., Medved, J., Varga, R., Zhang, X.,
and D. Dhody, "Optimizations of Label Switched Path State
Synchronization Procedures for a Stateful PCE", RFC 8232,
DOI 10.17487/RFC8232, September 2017,
<https://www.rfc-editor.org/info/rfc8232>.
[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>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[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-04 (work in progress), July 2019.
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[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-12 (work in progress), July 2019.
[I-D.ietf-pce-pcep-extension-for-pce-controller]
Zhao, Q., Li, Z., Negi, M., and C. Zhou, "PCEP Procedures
and Protocol Extensions for Using PCE as a Central
Controller (PCECC) of LSPs", draft-ietf-pce-pcep-
extension-for-pce-controller-02 (work in progress), July
2019.
[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-16 (work in progress),
March 2019.
[I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,
Gredler, H., and B. Decraene, "IS-IS Extensions for
Segment Routing", draft-ietf-isis-segment-routing-
extensions-25 (work in progress), May 2019.
[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-27 (work in progress), December 2018.
[I-D.litkowski-pce-state-sync]
Litkowski, S., Sivabalan, S., Li, C., and H. Zheng, "Inter
Stateful Path Computation Element (PCE) Communication
Procedures.", draft-litkowski-pce-state-sync-06 (work in
progress), July 2019.
[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-13 (work in progress), February 2019.
[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-22
(work in progress), May 2019.
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[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.
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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
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
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Alex Tokar
Cisco Systems
Slovak Republic
EMail: atokar@cisco.com
Authors' Addresses
Quintin Zhao
Huawei Technologies
125 Nagog Technology Park
Acton, MA 01719
USA
EMail: quintinzhao@gmail.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: mahendrasingh@huawei.com
Chao Zhou
Cisco Systems
EMail: choa.zhou@cisco.com
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