| Internet-Draft | PCEP Extensions for Topology Filter | February 2025 |
| Xiong, et al. | Expires 27 August 2025 | [Page] |
This document proposes a set of extensions for Path Computation Element Communication Protocol (PCEP) to support the topology filter during path computation.¶
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[RFC5440] describes the Path Computation Element Computation Protocol (PCEP) which is used between a Path Computation Element (PCE) and a Path Computation Client (PCC) (or other PCE) to enable computation of Multi-protocol Label Switching (MPLS) for Traffic Engineering Label Switched Path (TE LSP). PCEP Extensions for the Stateful PCE Model [RFC8231] describes a set of extensions to PCEP to enable active control of MPLS-TE and Generalized MPLS (GMPLS) tunnels. As depicted in [RFC4655], a PCE MUST be able to compute the path of a TE LSP by operating on the TED and considering bandwidth and other constraints applicable to the TE LSP service request.¶
A PCE always perform path computation based on the network topology information collected through BGP-LS [RFC9552]. BGP-LS can get multiple link-state data from multiple IGP instance, or multiple virtual topologies from a single IGP instance. In some cases, as per [I-D.ietf-teas-yang-topology-filter], a path may be computed within a network topology such as a specified topology, a topology associated with a specific IGP domain, a topology learnt from a specific TE information source, a topology defined by the application of one or more topology filters, a topology associated with an Network Resource Partition (NRP) and so on. The PCE MUST take the topology related constraints into consideration during the path computation.¶
As defined in [I-D.ietf-teas-yang-topology-filter], a topology filter is a data construct that is used to filter network topologies. This document proposes a set of extensions for PCEP to support the topology filter during path computation.¶
The terminology is defined as [RFC5440], [RFC9552] and [RFC8795].¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].¶
As defined in [I-D.ietf-teas-yang-topology-filter], a topology filter specifies the topology reference or a set of filtering rules. The topology filters carry a list of topology filters and a topology filter-set constitutes a list of topology filter references.¶
The topology reference indicates a predefined TE topology or a specific IGP domain. A TE topology can be identified from a global scope such as a provider ID, a client ID or a topology ID. And a specific IGP domain can be identified by protocol ID, instance ID, division ID, algo ID and MT ID. The PCE should consider these identifiers as topology constraints during path computation.¶
The filtering rules specify a set of constraints on the topology including include-any, include-all and exclude. A set of attributes that can be used as rules to filter the topology such as link affinity, link name, node prefix, AS number and TE information source. The filtering rules of these attributes can be used to compute path at PCE.¶
This document defines a new TOPOLOGY-FILTER object to carry the topology filter. The TOPOLOGY-FILTER object is optional and specifies the specific topology to be taken into account by the PCE during path computation. The TOPOLOGY-FILTER object can be carried within a PCReq message, or a PCRep message in case of unsuccessful path computation.¶
TOPOLOGY-FILTER Object-Class is TBD1.¶
TOPOLOGY-FILTER Object-Type is TBD2.¶
The format of the TOPOLOGY-FILTER object body is:¶
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Optional TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Reserved (24 bits): This field MUST be set to zero on transmission and MUST be ignored on receipt.¶
Flags (8 bits): No flags are currently defined. Unassigned flags MUST be set to zero on transmission and MUST be ignored on receipt.¶
The format of optional TLVs is defined in [RFC5440] and may be used to carry topology filter information as defined in section.¶
As defined in [RFC9552], the IGP domain has a unique IGP representation by using the combination of OSPF Area-ID, Router-ID, Protocol-ID, Multi-Topology Identifier (MT-ID), and BGP-LS Instance-ID. This document defines a new IGP Domain Identifier TLV for topology filter to identify a IGP domain within a referenced topology.¶
The IGP Domain Identifier TLV is optional and the format is as following shown:¶
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=TBD3 | Length=24 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol-ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Instance-ID |
| (64 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OSPF Area-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Algorithm-ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Multi-Topology-ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The code point for the TLV type is TBD3. The TLV length is 24 octets.¶
Protocol-ID (8 bits): defined in [RFC9552] section 5.2.¶
Instance-ID (64 bits): defined in [RFC9552] section 5.2.¶
OSPF Area-ID (32 bits): defined in [RFC9552] section 5.2.1.4.¶
Algorithm-ID (8 bits): defined in [I-D.ietf-pce-sid-algo] section 3.4.¶
Multi-Topology-ID (16 bits): defined in [RFC9552] section 5.2.2.1.¶
Reserved: This fields MUST be set to zero on transmission and MUST be ignored on receipt.¶
This document defines a new TE Topology Identifier TLV for topology filter to identify a predefined TE topology within a referenced topology.¶
The TE Topology Identifier TLV is optional and the format is as following shown:¶
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=TBD4 | Length=12 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Provider ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Client ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Topology ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The code point for the TLV type is TBD4. The TLV length is 12 octets.¶
Provider ID (32 bits): defined in [RFC8776].¶
This document defines a new Filtering Rules TLV for topology filter to carry a set of constrains on the topology by include-any, include-all and exclude.¶
The Filtering Rules TLV is optional and the format is as following shown :¶
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=TBD5 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Include-any |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Include-all |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Exclude |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Optional sub-TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The code point for the TLV type is TBD5. The TLV length is variable.¶
The sub-TLVs carry the attributes that can be used as rules to filter the topology.¶
The Link ID is used to identify the link that is used during the path calculation.¶
The Link ID sub-TLV is defined:¶
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=TBD6 | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The code point for the TLV type is TBD6. The TLV length is 6 octets.¶
Link ID (32bits ): defined in IS-IS [RFC5307] and OSPF [RFC3630].¶
The Admin Group is used to include the links that is used during the path calculation.¶
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=TBD7 | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Admin Group |
+- -+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The code point for the sub-TLV type is TBD7. The length is variable.¶
Extended Administrative Group: Extended Administrative Group as defined in [RFC7308].¶
The format of the Source Protocol sub-TLV is:¶
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=TBD8 | Length | Reserved | Protocol-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Instance-ID |
| (64 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The code point for the TLV type is TBD8. The TLV length is 10 octets.¶
A PCC MAY insert a TOPOLOGY-FILTER object in PCReq message to indicate the specific topology that MUST be considered by the PCE during path computation. The PCE will compute the path with the constrains with the filtering rules and reply the result to the PCC with a PCRep message.¶
The PCE could perform path computation based on the topology identified by the topology filter rules that can be applied on either the native topology or a user specified topology. The absence of the IGP Domain Identifier TLV and TE Topology Identifier TLV indicate that the PCE should compute within a native topology and only Filtering Rules TLV is applied as the filtering rules.¶
IANA is requested to make allocations for Topology Filter Object from the registry, as follows:¶
TOPOLOGY-FILTER Object-Class is TBD1.¶
TOPOLOGY-FILTER Object-Type is TBD2.¶
The TLVs for Topology Filter Object is as follows:¶
| Type | TLV | Reference |
|---|---|---|
| TBD3 | IGP Domain Identifier TLV | [this document] |
| TBD4 | TE Topology Identifier TLV | [this document] |
| TBD5 | Filtering Rules TLV | [this document] |
IANA is requested to make allocations for sub-TLVs from the registry, as follows:¶
TBA¶
TBA¶