| Internet-Draft | PCEP Extension for NRP-ID | November 2021 |
| Xiong, et al. | Expires 10 May 2022 | [Page] |
This document proposes a set of extensions for PCEP to support the identifier of Network Resource Partition (NRP-ID) as the constraint of network slicing during path computation.¶
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[RFC5440] describes the Path Computation Element 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. The constraint parameters are provided such as metric, bandwidth, delay, affinity, etc. However these parameters can't meet the network slicing requirements.¶
According to 5G context, network slicing is the collection of a set of technologies to support network service differentiation and meeting the diversified requirements from vertical industries. IETF Network Slice is defined in [I-D.ietf-teas-ietf-network-slice-definition]. The slices may be viewed as virtual networks and partition the network resources into sub-topologies in transport network. Slice Aggregate is a a collection of packets that match a slice policy selection criteria and are given the same forwarding treatment as defined in [I-D.bestbar-teas-ns-packet]. And Network Resource Partition is the collection of resources that are used to support a slice aggregate. The identifier of Network Resource Partition (NRP-ID) could be used to identify the slice and network resource and viewed as constraints of network slicing when PCE is deployed. PCE MUST take the identifier of slicing into consideration during path computation.¶
This document proposes a set of extensions for PCEP to support the NRP-ID as the constraint of network slicing during path computation.¶
The terminology is defined as [RFC5440] and [I-D.ietf-teas-ietf-network-slice-definition].¶
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.¶
As defined in [RFC5440] , the LSPA object is used to specify the LSP attributes to be taken into account by the PCE during path computation such as constraints. This document proposes new TLV for the LSPA object to carry TE constraints in Network Slicing.¶
The NRP-ID TLV is optional and is defined to carry the slice specific constraint. PCEP message needs to carry NRP-ID to let the scope of path calculation to be limited in a specific network resources partition.¶
There are many control plane technologies to realize network slice. Some control plane technologies may directly maintain resources per slice granularity in the link-state database, only for the case with small slice scalability. [I-D.bestbar-teas-ns-packet] proposes a more scalable slicing scheme. The resource information in link-state database is identified by NRP-ID to distinguish the logical topologies corresponding to different slice-aggregate. Within the controller, a slice-aggregate includes one or more slices mapped to it. If the number of slices is small, the resources per slice granularity can be maintained directly in the link-state database. In this case, different slice may be mapped to different slice-aggregate. If the number of slices is large, it is not recommended to maintain the slice granularity resources in the link-state database, but the aggregated granularity.¶
It is required to define a NRP-ID constraint in the TE purpose definition of overlay service. For example, VPN routes may have Color attribute (refer to [I-D.ietf-idr-tunnel-encaps] and [I-D.ietf-spring-segment-routing-policy]). Color represents aspecific TE purpose, which can contain an NRP-ID.¶
When the controller receives the path computation request with a NRP- ID constraint, it can use the resources identified by specific NRP-ID in TED to calculate the path. PCE may maintain resources per path within the resource pool identified by NRP-ID.¶
In a PCReq message, a PCC MAY insert one NRP-ID TLV to indicate the slice based virtual network that MUST be considered by the PCE. The PCE will perform path computation based on the intra-domain or inter- domain sub-topology identified by the specific NRP-ID, that can be used to find the corresponding customized topology or referenced topology, and corresponding resources.¶
In a PCRep/PCInit/PCUpd message, the NRP-ID TLV MAY be carried so as to provide the network slicing information for the computed path. The headend may put the NRP-ID, or other information that can be deduced to a NRP-ID, to an encapsulated data packet.¶
The format of the NRP-ID TLV is shown as Figure 1:¶
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=TBD1 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NRP-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The code point for the TLV type is TBD1. The TLV length is 4 octets.¶
NRP-ID (32 bits): indicates the identifier of Network Resource Partition to represent an IETF Network Slice that is defined in [I-D.ietf-teas-ietf-network-slice-definition].¶
TBA¶
TBA¶
IANA is requested to make allocations from the registry, as follows:¶
| Type | TLV | Reference |
|---|---|---|
| TBD1 | NRP-ID TLV | [this document] |