| PCE Working Group | Q. Zhao |
| Internet-Draft | Z. Li |
| Intended status: Standards Track | D. Dhody |
| Expires: December 21, 2018 | S. Karunanithi |
| Huawei Technologies | |
| A. Farrel | |
| Juniper Networks, Inc | |
| C. Zhou | |
| Cisco Systems | |
| June 19, 2018 |
PCEP Procedures and Protocol Extensions for Using PCE as a Central Controller (PCECC) of LSPs
draft-zhao-pce-pcep-extension-for-pce-controller-08
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.
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 December 21, 2018.
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.
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 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].
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.
Terminologies used in this document is same as described in the draft [RFC8283] and [I-D.ietf-teas-pcecc-use-cases].
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 taker 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. The rest of processing is similar to the existing stateful PCE mechanism.
Following key requirements associated PCECC should be considered when designing the PCECC based solution:
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.
This document defines the following new PCEP messages and extends the existing messages to support PCECC:
The new LSP functions defined in this document are mapped onto the messages as shown in the following table.
+----------------------------------------+--------------------------+ | 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 | +----------------------------------------+--------------------------+
This document specify a new object 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. 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.
During PCEP Initialization Phase, PCEP Speakers (PCE or PCC) advertise their support of PCECC extensions.
This document defines a new Path Setup Type (PST) [I-D.ietf-pce-lsp-setup-type] for PCECC, as follows:
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=TBD 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.
The presence of the PST 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 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 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 then a PCErr message with Error-Type=19(Invalid Operation) and Error-Value=TBD (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 SHOULD send a PCErr message with Error-Type=19 (Invalid Operation) and Error-value=TBD (stateful PCE capability was not advertised) and terminate the session.
The PCEP messages pertaining to PCECC MUST include PATH-SETUP-TYPE TLV [I-D.ietf-pce-lsp-setup-type] in the SRP object to clearly identify the PCECC LSP is intended.
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) MUST be unique. The PLSP-ID is included for maintainability reasons. 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 PCEP. The PCC further responds with the PCRpt messages including the CCI and LSP objects.
Once the central controller's instructions (label operations) are completed, the PCE SHOULD send the PCUpd message to the Ingress PCC. The 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 5.4.2.2 for the corresponding LSP.
The Basic PCECC LSP setup sequence is as shown below.
+-------+ +-------+
|PCC | | PCE |
|Ingress| +-------+
+------| | |
| PCC +-------+ |
| Transit| | |
+------| | |-- PCRpt,PLSP-ID=1, PST=TBD, D=1---->| PCECC LSP
|PCC +--------+ | |
|Egress | | | |
+--------+ | | |
| | | |
|<------ PCInitiate,CC-ID=X,PLSP-ID=1 ------------ | Label
| | | | download
|------- PCRpt,CC-ID=X,PLSP-ID=1 ----------------->|
| | | |
| |<----- PCInitiate,CC-ID=Y,PLSP-ID=1 ----- | Label
| | | | download
| |----- PCRpt,CC-ID=Y,PLSP-ID=1 ---------->|
| | | |
| | |<--- PCInitiate,CC-ID=Z,PLSP-ID=1 - | Label
| | | | download
| | |---- PCRpt,CC-ID=Z,PLSP-ID=1 ------>|
| | | |
| | |<-- PCUpd,PLSP-ID=1,PST=TBD, 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.
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.
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 5.4.1.
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=TBD (PCECC 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 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=TBD (PCECC failure) and Error-value=TBD (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.
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=TBD, "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.
+-------+ +-------+
|PCC | | PCE |
|Ingress| +-------+
+------| | |
| PCC +-------+ |
| Transit| | |
+------| | |-- PCRpt,PLSP-ID=1,PST=TBD,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 ------------------>|
| | | |
| |<----- PCInitiate,CC-ID=Y,PLSP-ID=1 ------ | Label
| | | R=1 | cleanup
| |----- PCRpt,CC-ID=Y,PLSP-ID=1 ----------->|
| | | |
| | |<--- PCInitiate,CC-ID=Z,PLSP-ID=1 -- | Label
| | | R=1 | cleanup
| | |---- PCRpt,CC-ID=Z,PLSP-ID=1 ------->|
| | | |
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.
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.
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 5.4.1.
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 5.4.2.2 for the corresponding LSP.
The PCE Initiated PCECC LSP setup sequence is shown below -
+-------+ +-------+
|PCC | | PCE |
|Ingress| +-------+
+------| | |
| PCC +-------+ |
| Transit| | |
+------| | |<--PCInitiate,PLSP-ID=0,PST=TBD,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 ------------------>|
| | | |
| |<----- PCInitiate,CC-ID=Y,PLSP-ID=2 ------- | Label
| | | | download
| |----- PCRpt,CC-ID=Y,PLSP-ID=2 ----------->|
| | | |
| | |<--- PCInitiate,CC-ID=Z,PLSP-ID=2 --- | Label
| | | | download
| | |---- PCRpt,CC-ID=Z,PLSP-ID=2 ------->|
| | | |
| | |<-- PCUpd, PLSP-ID=2, PST=TBD, 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].
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 5.4.2.2.
The PCECC LSP Update sequence is shown below -
+-------+ +-------+
|PCC | | PCE |
|Ingress| +-------+
+------| | |
| PCC +-------+ |
| Transit| | |
+------| | | |
|PCC +--------+ | |
|Egress | | | |
+--------+ | | |
| | | | New Path for
|<------ PCInitiate,CC-ID=XX,PLSP-ID=1 ----------- | LSP trigger
| | | | new instruct
|------- PCRpt,CC-ID=XX,PLSP-ID=1 ---------------->|
| | | |
| |<----- PCInitiate,CC-ID=YY,PLSP-ID=1------ | Label
| | | | download
| |----- PCRpt,CC-ID=YY,PLSP-ID=1 --------->|
| | | |
| | |<--- PCInitiate,CC-ID=ZZ,PLSP-ID=1 - | Label
| | | | download
| | |---- PCRpt,CC-ID=ZZ,PLSP-ID=1 ----->|
| | | |
| | |<-- PCUpd, PLSP-ID=1, PST=TBD, D=1-- | PCECC
| | | SRP=S | LSP Update
| | | |
| | |-- PCRpt,PLSP-ID=1,PST=TBD,D=1 -->| Trigger
| | | (SRP=S) | Delete old
| | | | instruct
| | | |
|<------ PCInitiate,CC-ID=X, PLSP-ID=1 ----------- | Label
| | | R=1 | cleanup
|------- PCRpt,CC-ID=X, PLSP-ID=1 ---------------->|
| | | |
| |<----- PCInitiate,CC-ID=Y, PLSP-ID=1 ----- | Label
| | | R=1 | cleanup
| |----- PCRpt,CC-ID=Y, PLSP-ID=1 --------->|
| | | |
| | |<--- PCInitiate,CC-ID=Z, PLSP-ID=1 - | Label
| | | R=1 | cleanup
| | |---- PCRpt,CC-ID=Z, PLSP-ID=1 ----->|
| | | |
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.
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.
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.
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.
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.
<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].
The PCInitiate message [RFC8281] can be used to download or remove the labels, the message has been extended as shown below -
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=TBD (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.
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.
<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].
The PCRpt message can be used to report the labels that were allocated by the PCE, to be used during the state synchronization phase.
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=TBD (CCI object missing). Two CCI object can be included in the PCRpt message for the transit LSR.
The PCEP objects defined in this document are compliant with the PCEP object format defined in [RFC5440].
This document defines a new optional TLVs for use in the OPEN Object.
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=TBD | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The type of the TLV is TBD 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.
The PATH-SETUP-TYPE TLV is defined in [I-D.ietf-pce-lsp-setup-type]; this document defines a new PST value:
On a PCRpt/PCUpd/PCInitiate message, the PST=TBD in PATH-SETUP-TYPE TLV in SRP object indicates that this LSP was setup via a PCECC based mechanism.
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 TBD.
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 |O|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Optional TLV //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields in the CCI object are as follows:
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=TBD | 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=TBD | 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=TBD | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Node-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The address TLVs are as follows:
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.
PCE has complete control over PCC to update the labels and can cause the LSP's to behave inappropriate and cause 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].
A PCE or PCC implementation SHOULD allow to configure to enable/disable PCECC capability as a global configuration.
[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.
Mechanisms defined in this document do not imply any new liveness detection and monitoring requirements in addition to those already listed in [RFC5440].
Mechanisms defined in this document do not imply any new operation verification requirements in addition to those already listed in [RFC5440] and [RFC8231].
PCEP extensions defined in this document do not put new requirements on other protocols.
PCEP extensions defined in this document do not put new requirements on network operations.
IANA is requested to confirm the early allocation of the following TLV Type Indicator values within the "PCEP TLV Type Indicators" sub- registry of the PCEP Numbers registry, and to update the reference in the registry to point to this document, when it is an RFC:
| Value | Meaning | Reference |
|---|---|---|
| TBD | PCECC-CAPABILITY | This document |
| TBD | IPV4-ADDRESS TLV | This document |
| TBD | IPV6-ADDRESS TLV | This document |
| TBD | UNNUMBERED-IPV4-ID-ADDRESS TLV | This document |
IANA is requested to allocate new PST Field in PATH- SETUP-TYPE TLV. The allocation policy for this new registry should be by IETF Consensus. The new registry should contain the following value:
| Value | Description | Reference |
|---|---|---|
| TBD | Traffic engineering path is | This document |
| setup using PCECC mode |
IANA is requested to allocate new registry for CCI PCEP object.
| Object-Class Value | Name | Reference |
|---|---|---|
| TBD | CCI Object-Type | This document |
| 1 | MPLS Label |
IANA is requested to create a registry to manage the Flag field of the CCI object.
One bit to be defined for the CCI Object flag field in this document:
Codespace of the Flag field (CCI Object)
| Bit | Description | Reference |
|---|---|---|
| 7 | Specifies label | This document |
| is out label |
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:
We would like to thank Robert Tao, Changjing Yan, Tieying Huang and Avantika for their useful comments and suggestions.
Udayasree Palle
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
EMail: udayasreereddy@gmail.com
Mahendra Singh Negi
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
EMail: mahendrasingh@huawei.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