| Internet-Draft | Binding Label/SID | March 2023 |
| Sivabalan, et al. | Expires 28 September 2023 | [Page] |
In order to provide greater scalability, network confidentiality, and service independence, Segment Routing (SR) utilizes a Binding Segment Identifier (SID) (called BSID) as described in RFC 8402. It is possible to associate a BSID to an RSVP-TE-signaled Traffic Engineering Label Switched Path or an SR Traffic Engineering path. The BSID can be used by an upstream node for steering traffic into the appropriate TE path to enforce SR policies. This document specifies the concept of binding value, which can be either an MPLS label or Segment Identifier. It further specifies an extension to Path Computation Element (PCE) communication Protocol(PCEP) for reporting the binding value by a Path Computation Client (PCC) to the PCE to support PCE-based Traffic Engineering policies.¶
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 28 September 2023.¶
Copyright (c) 2023 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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶
A Path Computation Element (PCE) can compute Traffic Engineering paths (TE paths) through a network where those paths are subject to various constraints. Currently, TE paths are set up using either the RSVP-TE signaling protocol or Segment Routing (SR). We refer to such paths as RSVP-TE paths and SR-TE paths respectively in this document.¶
As per [RFC8402] SR allows a head-end node to steer a packet flow along a given path via a Segment Routing Policy (SR Policy). As per [RFC9256], an SR Policy is a framework that enables the instantiation of an ordered list of segments on a node for implementing a source routing policy with a specific intent for traffic steering from that node.¶
As described in [RFC8402], a Binding Segment Identifier (BSID) is bound to a Segment Routing (SR) Policy, instantiation of which may involve a list of Segment Identifiers (SIDs). Any packets received with an active segment equal to a BSID are steered onto the bound SR Policy. A BSID may be either a local (SR Local Block (SRLB)) or a global (SR Global Block (SRGB)) SID. As per Section 6.4 of [RFC9256] a BSID can also be associated with any type of interface or tunnel to enable the use of a non-SR interface or tunnel as a segment in a SID list. In this document, the term 'binding label/SID' is used to generalize the allocation of binding value for both SR and non-SR paths.¶
[RFC5440] describes the PCEP for communication between a Path Computation Client (PCC) and a PCE or between a pair of PCEs as per [RFC4655]. [RFC8231] specifies extensions to PCEP that allow a PCC to delegate its Label Switched Paths (LSPs) to a stateful PCE. A stateful PCE can then update the state of LSPs delegated to it. [RFC8281] specifies a mechanism allowing a PCE to dynamically instantiate an LSP on a PCC by sending the path and characteristics. This document specifies an extension to PCEP to manage the binding of label/SID that can be applied to SR, RSVP-TE, and other path setup types.¶
[RFC8664] provides a mechanism for a PCE (acting as a network controller) to instantiate SR-TE paths (candidate paths) for an SR Policy onto a head-end node (acting as a PCC) using PCEP. For more information on the SR Policy Architecture, see [RFC9256].¶
A binding label/SID has local significance to the ingress node of the corresponding TE path. When a stateful PCE is deployed for setting up TE paths, a binding label/SID reported from the PCC to the stateful PCE is useful for the purpose of enforcing end-to-end TE/SR policy. A sample Data Center (DC) and IP/MPLS WAN use-case is illustrated in Figure 1 with a multi-domain PCE. In the IP/MPLS WAN, an SR-TE LSP is set up using the PCE. The list of SIDs of the SR-TE LSP is {A, B, C, D}. The gateway node 1 (which is the PCC) allocates a binding SID X and reports it to the PCE. In the MPLS DC network, an end-to-end SR-TE LSP is established. In order for the access node to steer the traffic towards Node-1 and over the SR-TE path in WAN, the PCE passes the SID stack {Y, X} where Y is the node SID of the gateway node-1 to the access node and X is the BSID. In the absence of the BSID X, the PCE would need to pass the SID stack {Y, A, B, C, D} to the access node. This example also illustrates the additional benefit of using the binding label/SID to reduce the number of SIDs imposed by the access nodes with a limited forwarding capacity.¶
SID stack
{Y, X} +--------------+
| Multi-domain |
_ _ _ _ _ _ _ _ _ _ _ _ _ _| PCE |
| +--------------+
| ^
| | Binding
| .-----. | SID (X) .-----.
| ( ) | ( )
V .--( )--. | .--( )--.
+------+ ( ) +-------+ ( ) +-------+
|Access|_( MPLS DC Network )_|Gateway|_( IP/MPLS WAN )_|Gateway|
| Node | ( ==============> ) |Node-1 | ( ================> ) |Node-2 |
+------+ ( SR-TE path ) +-------+ ( SR-TE path ) +-------+
'--( )--' Node '--( )--'
( ) SID of ( )
'-----' Node-1 '-----'
is Y SIDs for SR-TE LSP:
{A, B, C, D}
Using the extension defined in this document, a PCC could report to the stateful PCE the binding label/SID it allocated via a Path Computation LSP State Report (PCRpt) message. It is also possible for a stateful PCE to request a PCC to allocate a specific binding label/SID by sending a Path Computation LSP Update Request (PCUpd) message. If the PCC can successfully allocate the specified binding value, it reports the binding value to the PCE. Otherwise, the PCC sends an error message to the PCE indicating the cause of the failure. A local policy or configuration at the PCC SHOULD dictate if the binding label/SID needs to be assigned.¶
To implement the needed changes to PCEP, in this document, we introduce a new OPTIONAL TLV that a PCC can use in order to report the binding label/SID associated with a TE LSP, or a PCE to request a PCC to allocate any or a specific binding label/SID value. This TLV is intended for TE LSPs established using RSVP-TE, SR-TE, or any other future method. In the case of SR-TE LSPs, the TLV can carry a binding label (for SR-TE path with MPLS data-plane) or a binding IPv6 SID (e.g., IPv6 address for SR-TE paths with IPv6 data-plane). Throughout this document, the term "binding value" means either an MPLS label or a SID.¶
As another way to use the extension specified in this document, to support the PCE-based central controller [RFC8283] operation where the PCE would take responsibility for managing some part of the MPLS label space for each of the routers that it controls, the PCE could directly make the binding label/SID allocation and inform the PCC. See Section 8 for details.¶
In addition to specifying a new TLV, this document specifies how and when a PCC and PCE can use this TLV, how they can allocate a binding label/SID, and associated error handling.¶
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.¶
The following terminologies are used in this document:¶
The new optional TLV called "TE-PATH-BINDING TLV" (whose format is shown in Figure 2) is defined to carry the binding label/SID for a TE path. This TLV is associated with the LSP object specified in [RFC8231]. This TLV can also be carried in the PCEP-ERROR object [RFC5440] in case of error. Multiple instances of TE-PATH-BINDING TLVs MAY be present in the LSP and PCEP-ERROR object. The type of this TLV is 55 (early allocated by IANA). The length is variable.¶
[Note to RFC Editor: Please remove "(early allocated by IANA)" before publication]¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 55 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BT | Flags | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Binding Value (variable length) ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TE-PATH-BINDING TLV is a generic TLV such that it is able to carry binding label/SID (i.e. MPLS label or SRv6 SID). It is formatted according to the rules specified in [RFC5440]. The value portion of the TLV comprises:¶
Binding Type (BT): A one-octet field that identifies the type of binding included in the TLV. This document specifies the following BT values:¶
Section 12.1.1 defines the IANA registry used to maintain all these binding types as well as any future ones. Note that multiple TE-PATH-BINDING TLVs with same or different Binding Types MAY be present for the same LSP. A PCEP speaker could allocate multiple TE-PATH-BINDING TLVs (of the same BT), and use different binding values in different domains or use-cases based on a local policy.¶
Flags: 1 octet of flags. The following flag is defined in the new registry "TE-PATH-BINDING TLV Flag field" as described in Section 12.1.1:¶
where:¶
Reserved: MUST be set to 0 while sending and ignored on receipt.¶
Binding Value: A variable-length field, padded with trailing zeros to a 4-octet boundary. When the BT is 0, the 20 bits represent the MPLS label. When the BT is 1, the 32 bits represent the MPLS label stack entry as per [RFC3032]. When the BT is 2, the 128 bits represent the SRv6 SID. When the BT is 3, the Binding Value also contains the SRv6 Endpoint Behavior and SID Structure, defined in Section 4.1. In this document, the TE-PATH-BINDING TLV is considered to be empty if no Binding Value is present. Note that the length of the TLV would be 4 in such a case.¶
This section specifies the format of the Binding Value in the TE-PATH-BINDING TLV when the BT is set to 3 for the SRv6 Binding SIDs [RFC8986]. The format is shown in Figure 4.¶
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | SRv6 Binding SID (16 octets) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Endpoint Behavior | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LB Length | LN Length | Fun. Length | Arg. Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Binding Value consists of:¶
[RFC8986] defines an SRv6 SID as consisting of LOC:FUNCT:ARG, where a locator (LOC) is encoded in the L most significant bits of the SID, followed by F bits of function (FUNCT) and A bits of arguments (ARG). A locator may be represented as B:N where B is the SRv6 SID locator block (IPv6 prefix allocated for SRv6 SIDs by the operator) and N is the identifier of the parent node instantiating the SID called locator node. The following fields are used to advertise the length of each individual part of the SRv6 SID as defined in :¶
The total of the locator block, locator node, function, and argument lengths MUST be lower or equal to 128 bits. If this condition is not met, the corresponding TE-PATH-BINDING TLV is considered invalid. Also, if the Endpoint Behavior is found to be unknown or inconsistent, it is considered invalid. A PCErr message with Error-Type = 10 ("Reception of an invalid object") and Error-Value = 37 ("Invalid SRv6 SID Structure") MUST be sent in such cases.¶
The SRv6 SID Structure could be used by the PCE for ease of operations and monitoring. For example, this information could be used for validation of SRv6 SIDs being instantiated in the network and checked for conformance to the SRv6 SID allocation scheme chosen by the operator as described in Section 3.2 of [RFC8986]. In the future, PCE could also be used for verification and the automation for securing the SRv6 domain by provisioning filtering rules at SR domain boundaries as described in Section 5 of [RFC8754]. The details of these potential applications are outside the scope of this document.¶
The binding value is usually allocated by the PCC and reported to a PCE via a PCRpt message (see Section 8 where PCE does the allocation). If a PCE does not recognize the TE-PATH-BINDING TLV, it would ignore the TLV in accordance with [RFC5440]. If a PCE recognizes the TLV but does not support the TLV, it MUST send a PCErr with Error-Type = 2 (Capability not supported).¶
Multiple TE-PATH-BINDING TLVs are allowed to be present in the same LSP object. This signifies the presence of multiple binding SIDs for the given LSP. In the case of multiple TE-PATH-BINDING TLVs, the existing instances of TE-PATH-BINDING TLVs MAY be included in the LSP object. In case of an error condition, the whole message is rejected and the resulting PCErr message MAY include the offending TE-PATH-BINDING TLV in the PCEP-ERROR object.¶
If a PCE recognizes an invalid binding value (e.g., label value from the reserved MPLS label space), it MUST send a PCErr message with Error-Type = 10 ("Reception of an invalid object") and Error Value = 2 ("Bad label value") as specified in [RFC8664].¶
For SRv6 BSIDs, it is RECOMMENDED to always explicitly specify the SRv6 Endpoint Behavior and SID Structure in the TE-PATH-BINDING TLV by setting the BT (Binding Type) to 3. This can enable the sender to have control of the SRv6 Endpoint Behavior and SID Structure. A sender MAY choose to set the BT to 2, in which case the receiving implementation chooses how to interpret the SRv6 Endpoint Behavior and SID Structure according to local policy.¶
If a PCC wishes to withdraw a previously reported binding value, it MUST send a PCRpt message with the specific TE-PATH-BINDING TLV with R flag set to 1. If a PCC wishes to modify a previously reported binding, it MUST withdraw the former binding value (with R flag set in the former TE-PATH-BINDING TLV) and include a new TE-PATH-BINDING TLV containing the new binding value. Note that other instances of TE-PATH-BINDING TLVs that are unchanged MAY also be included. If the unchanged instances are not included, they will remain associated with the LSP.¶
If a PCE requires a PCC to allocate a (or several) specific binding value(s), it may do so by sending a PCUpd or PCInitiate message containing a TE-PATH-BINDING TLV(s). If the value(s) can be successfully allocated, the PCC reports the binding value(s) to the PCE. If the PCC considers the binding value specified by the PCE invalid, it MUST send a PCErr message with Error-Type = TBD2 ("Binding label/SID failure") and Error Value = TBD3 ("Invalid SID"). If the binding value is valid, but the PCC is unable to allocate the binding value, it MUST send a PCErr message with Error-Type = TBD2 ("Binding label/SID failure") and Error Value = TBD4 ("Unable to allocate the specified binding value"). Note that, in case of an error, the PCC rejects the PCUpd or PCInitiate message in its entirety and can include the offending TE-PATH-BINDING TLV in the PCEP-ERROR object.¶
If a PCE wishes to request the withdrawal of a previously reported binding value, it MUST send a PCUpd message with the specific TE-PATH-BINDING TLV with R flag set to 1. If a PCE wishes to modify a previously requested binding value, it MUST request the withdrawal of the former binding value (with R flag set in the former TE-PATH-BINDING TLV) and include a new TE-PATH-BINDING TLV containing the new binding value. If a PCC receives a PCUpd message with TE-PATH-BINDING TLV where the R flag is set to 1, but either the binding value is missing (empty TE-PATH-BINDING TLV) or the binding value is incorrect, it MUST send a PCErr message with Error-Type = TBD2 ("Binding label/SID failure") and Error Value = TBD6 ("Unable to remove the binding value").¶
In some cases, a stateful PCE may want to request that the PCC allocate a binding value of the PCC's own choosing. It instructs the PCC by sending a PCUpd message containing an empty TE-PATH-BINDING TLV, i.e., no binding value is specified (bringing the Length field of the TLV to 4). A PCE can also request a PCC to allocate a binding value at the time of initiation by sending a PCInitiate message with an empty TE-PATH-BINDING TLV. Only one such instance of empty TE-PATH-BINDING TLV, per BT, SHOULD be included in the LSP object and others ignored on receipt. If the PCC is unable to allocate a new binding value as per the specified BT, it MUST send a PCErr message with Error-Type = TBD2 ("Binding label/SID failure") and Error-Value = TBD5 ("Unable to allocate a new binding label/SID").¶
As previously noted, if a message contains an invalid TE-PATH-BINDING TLV that leads to an error condition, the whole message is rejected including any other valid instances of TE-PATH-BINDING TLVs, if any. The resulting error message MAY include the offending TE-PATH-BINDING TLV in the PCEP-ERROR object.¶
If a PCC receives a TE-PATH-BINDING TLV in any message other than PCUpd or PCInitiate, it MUST close the corresponding PCEP session with the reason "Reception of a malformed PCEP message" (according to [RFC5440]). Similarly, if a PCE receives a TE-PATH-BINDING TLV in any message other than a PCRpt or if the TE-PATH-BINDING TLV is associated with any object other than an LSP or PCEP-ERROR object, the PCE MUST close the corresponding PCEP session with the reason "Reception of a malformed PCEP message" (according to [RFC5440]).¶
If a TE-PATH-BINDING TLV is absent in the PCRpt message and no binding values were reported before, the PCE MUST assume that the corresponding LSP does not have any binding. Similarly, if TE-PATH-BINDING TLV is absent in the PCUpd message and no binding values were reported before, the PCC's local policy dictates how the binding allocations are made for a given LSP.¶
Note that some binding types have similar information but different binding value formats. For example, BT=(2 or 3) is used for the SRv6 SID and BT=(0 or 1) is used for the MPLS Label. In case a PCEP speaker receives multiple TE-PATH-BINDING TLVs with the same SRv6 SID or MPLS Label but different BT values, it MUST send a PCErr message with Error-Type = TBD2 ("Binding label/SID failure") and Error-Value = TBD7 ("Inconsistent binding types").¶
In PCEP messages, LSP route information is carried in the Explicit Route Object (ERO), which consists of a sequence of subobjects. [RFC8664] defines the "SR-ERO subobject" capable of carrying a SID as well as the identity of the node/adjacency (NAI) represented by the SID. The NAI Type (NT) field indicates the type and format of the NAI contained in the SR-ERO. In case of binding SID, the NAI MUST NOT be included and NT MUST be set to zero. [RFC8664] Section 5.2.1 specifies bit settings and error handling in the case when NT=0.¶
[I-D.ietf-pce-segment-routing-ipv6] defines the "SRv6-ERO subobject" for an SRv6 SID. Similarly to SR-ERO (Section 6), the NAI MUST NOT be included and the NT MUST be set to zero. [RFC8664] Section 5.2.1 specifies bit settings and error handling in the case when NT=0.¶
Section 5 already includes the scenario where a PCE requires a PCC to allocate a specified binding value by sending a PCUpd or PCInitiate message containing a TE-PATH-BINDING TLV. This section specifies an OPTIONAL feature for the PCE to allocate the binding label/SID of its own accord in the case where the PCE also controls the label space of the PCC and can make the label allocation on its own as described in [RFC8283]. Note that the act of requesting a specific binding value (Section 5) is different from the act of allocating a binding label/SID as described in this section.¶
[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. [RFC9050] specifies the procedures and PCEP extensions for using the PCE as the central controller. It assumes that the exclusive label range to be used by a PCE is known and set on both PCEP peers. A future extension could add the capability to advertise this range via a possible PCEP extension as well (see [I-D.li-pce-controlled-id-space]).¶
When PCECC operations are supported as per [RFC9050], the binding label/SID MAY also be allocated by the PCE itself. Both peers need to exchange the PCECC capability as described in [RFC9050] before the PCE can allocate the binding label/SID on its own.¶
A new P flag in the LSP object [RFC8231] is introduced to indicate that the allocation needs to be made by the PCE. Note that the P flag could be used for other types of allocations (such as path segments [I-D.ietf-pce-sr-path-segment]) in future.¶
Note that -¶
If one or both speakers (PCE and PCC) have not indicated support and willingness to use the PCEP extensions for the PCECC as per [RFC9050] and a PCEP peer receives P=1 in the LSP object, it MUST:¶
It is assumed that the label range to be used by a PCE is known and set on both PCEP peers. The exact mechanism is out of the scope of [RFC9050] or this document. Note that the specific BSID could be from the PCE-controlled or the PCC-controlled label space. The PCE can directly allocate the label from the PCE-controlled label space using P=1 as described above, whereas the PCE can request the allocation of a specific BSID from the PCC-controlled label space with P=0 as described in Section 5.¶
Note that, the P-Flag in the LSP object SHOULD NOT be set to 1 without the presence of TE-PATH-BINDING TLV or any other future TLV defined for PCE allocation. On receipt of such an LSP object, the P-Flag is ignored. The presence of TE-PATH-BINDING TLV with P=1 indicates the allocation is for the binding label/SID. In the future, some other TLV (such as one defined in [I-D.ietf-pce-sr-path-segment]) could also be used alongside P=1 to indicate allocation of a different attribute. A future document should not attempt to assign semantics to P=1 without limiting its scope that both PCEP peers could agree on.¶
[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".¶
The security considerations described in [RFC5440], [RFC8231], [RFC8281], [RFC8664], and [RFC9050] are applicable to this specification. No additional security measure is required.¶
As described in [RFC8402] and [RFC8664], SR intrinsically involves an entity (whether head-end or a central network controller) controlling and instantiating paths in the network without the involvement of (other) nodes along those paths. Binding SIDs are in effect shorthand aliases for longer path representations, and the alias expansion is in principle known only by the node that acts on it. In this document, the expansion of the alias is shared between PCC and PCE, and rogue actions by either PCC or PCE could result in shifting or misdirecting traffic in ways that are hard for other nodes to detect. In particular, when a PCE propagates paths of the form {A, B, BSID} to other entities, the BSID values are opaque, and a rogue PCE can substitute a BSID from a different LSP in such paths to move traffic without the recipient of the path knowing the ultimate destination.¶
The case of BT=3 provides additional opportunities for malfeasance, as it purports to convey information about internal SRv6 SID structure. There is no mechanism defined to validate this internal structure information, and mischaracterizing the division of bits into locator block, locator node, function, and argument can result in different interpretation of the bits by PCC and PCE. Most notably, shifting bits into or out of the "argument" is a direct vector for affecting processing, but other attacks are also possible.¶
Thus, 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 BCP195 [RFC9325] (unless explicitly set aside in [RFC8253]).¶
All manageability requirements and considerations listed in [RFC5440], [RFC8231], and [RFC8664] apply to PCEP protocol extensions defined in this document. In addition, requirements and considerations listed in this section apply.¶
A PCC implementation SHOULD allow the operator to configure the policy the PCC needs to apply when allocating the binding label/SID.¶
If BT is set to 2, the operator needs to have local policy set to decide the SID structure and the SRv6 Endpoint Behavior of the BSID.¶
The PCEP YANG module [I-D.ietf-pce-pcep-yang] will be extended to include policy configuration for binding label/SID allocation.¶
The mechanisms defined in this document do not imply any new liveness detection and monitoring requirements in addition to those already listed in [RFC5440].¶
The mechanisms defined in this document do not imply any new operation verification requirements in addition to those already listed in [RFC5440], [RFC8231], and [RFC8664].¶
The mechanisms defined in this document do not imply any new requirements on other protocols.¶
The mechanisms defined in [RFC5440], [RFC8231], and [RFC8664] also apply to the PCEP extensions defined in this document.¶
IANA maintains the "Path Computation Element Protocol (PCEP) Numbers" registry. This document requests IANA actions to allocate code points for the protocol elements defined in this document.¶
This document defines a new PCEP TLV; IANA is requested to confirm the following early allocations from the "PCEP TLV Type Indicators" subregistry of the PCEP Numbers registry, as follows:¶
| Value | Description | Reference |
|---|---|---|
| 55 | TE-PATH-BINDING | This document |
IANA is requested to create a new subregistry "TE-PATH-BINDING TLV BT field" to manage the value of the Binding Type field in the TE-PATH-BINDING TLV. Initial values for the subregistry are given below. New values are assigned by Standards Action [RFC8126].¶
| Value | Description | Reference |
|---|---|---|
| 0 | MPLS Label | This document |
| 1 | MPLS Label Stack Entry | This document |
| 2 | SRv6 SID | This document |
| 3 | SRv6 SID with Behavior and Structure | This document |
| 4-255 | Unassigned | This document |
IANA is requested to create a new subregistry "TE-PATH-BINDING TLV Flag field" to manage the Flag field in the TE-PATH-BINDING TLV. New values are to be assigned by Standards Action [RFC8126]. Each bit should be tracked with the following qualities:¶
| Bit | Description | Reference |
|---|---|---|
| 0 | R (Removal) | This document |
| 1-7 | Unassigned | This document |
IANA is requested to confirm the early allocation for a new code-point in the "LSP Object Flag Field" sub-registry for the new P flag as follows:¶
| Bit | Description | Reference |
|---|---|---|
| 0 | PCE-allocation | This document |
This document defines a new Error-type and associated Error-Values for the PCErr message. IANA is requested to allocate new error-type and error-values within the "PCEP-ERROR Object Error Types and Values" subregistry of the PCEP Numbers registry, as follows:¶
| Error-Type | Meaning | Error-value | Reference |
|---|---|---|---|
| TBD2 | Binding label/SID failure | 0: Unassigned | This document |
| TBD3: Invalid SID | This document | ||
| TBD4: Unable to allocate the specified binding value | This document | ||
| TBD5: Unable to allocate a new binding label/SID | This document | ||
| TBD6: Unable to remove the binding value | This document | ||
| TBD7: Inconsistent binding types | This document |
We would like to thank Milos Fabian, Mrinmoy Das, Andrew Stone, Tom Petch, Aijun Wang, Olivier Dugeon, and Adrian Farrel for their valuable comments.¶
Thanks to Julien Meuric for shepherding. Thanks to John Scudder for the AD review.¶
Thanks to Theresa Enghardt for the GENART review.¶
Thanks to Martin Vigoureux, Benjamin Kaduk, Eric Vyncke, Lars Eggert, Murray Kucherawy, and Erik Kline for the IESG reviews.¶
Jonathan Hardwick Microsoft United Kingdom EMail: jonhardwick@microsoft.com Dhruv Dhody Huawei Technologies Divyashree Techno Park, Whitefield Bangalore, Karnataka 560066 India EMail: dhruv.ietf@gmail.com Mahendra Singh Negi RtBrick India N-17L, Floor-1, 18th Cross Rd, HSR Layout Sector-3 Bangalore, Karnataka 560102 India EMail: mahend.ietf@gmail.com Mike Koldychev Cisco Systems, Inc. 2000 Innovation Drive Kanata, Ontario K2K 3E8 Canada Email: mkoldych@cisco.com Zafar Ali Cisco Systems, Inc. Email: zali@cisco.com¶