Internet-Draft PCEP Extension for NRP-ID July 2022
Xiong, et al. Expires 7 January 2023 [Page]
Intended Status:
Standards Track
Q. Xiong
ZTE Corporation
S. Peng
ZTE Corporation
V. Beeram
Juniper Networks
T. Saad
Juniper Networks

PCEP Extension for NRP-ID


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.

Status of This Memo

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

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This Internet-Draft will expire on 7 January 2023.

Table of Contents

1. Introduction

[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. As defined in [I-D.ietf-teas-ietf-network-slice-definition], an IETF network slice is a logical network topology connecting a number of endpoints using a set of shared or dedicated network resources that are used to satisfy specific Service Level Objectives (SLOs). As defined in [I-D.ietf-teas-ietf-network-slices], a Network Resource Partition (NRP) is a collection of resources (bufferage, queuing, scheduling, etc.) in the underlay network to support the IETF Network Slice service (or any other service that needs logical network structures with required characteristics to be created). And as per [I-D.ietf-teas-ns-ip-mpls], NRP Identifier (NRP-ID) indicates an identifier that is globally unique within an NRP domain and that can be used in the control or management plane to identify the resources associated with the NRP. The 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.

2. Conventions used in this document

2.1. Terminology

The terminology is defined as [RFC5440] and [I-D.ietf-teas-ietf-network-slice-definition].

2.2. 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.

3. PCEP Extensions for Network Resource Partition

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 for 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 limit the network resources for path calculation within a NRP domain.

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                              |

Figure 1: Figure 1: NRP-ID TLV

The code point for the TLV type is TBD1. The TLV length is 4 octets.

NRP-ID (32 bits): indicates a NRP Identifier as defined in [I-D.ietf-teas-ns-ip-mpls].

3.2. Protocol Operation

As defined in [I-D.ietf-teas-ns-ip-mpls], NRP state aware TE (NRP-TE) should implement the TE path selection that takes into account the available network resources associated with a specific NRP. The NRP-ID TLV should be carried in PCEP messages when computing NRP state aware TE paths. The PCE may maintain network resources per path and the NRP state within the resource pool identified by NRP-ID.

In a PCReq message, a PCC MAY request the PCC to compute the NRP-TE path and insert a NRP-ID TLV to indicate the resources within a NRP domain. 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. The PCE may reply the PCC with NRP-ID TLV carried in PCRep message and the headend may insert the NRP-ID into an encapsulated data packet. In case of unsuccessful path computation when the NRP-ID constraint could not be satisfied, the the PCRep message may contain a NO-PATH object.

In a PCInit/PCUpd message, the PCE MAY compute the optimal NRP-TE path and carry the NRP-ID TLV so as to provide the network slicing information. If a PCC is unable to recognize a NRP-ID value passed in an LSP PCInit/PCUpd request, the PCC must keep the LSP in DOWN state, and include an LSP Error Code value of "Unsupported NRP" [Value to be assigned by IANA] in LSP State Report message.

4. Security Considerations


5. Acknowledgements


6. IANA Considerations

IANA is requested to make allocations from the registry, as follows:

Table 1
Type TLV Reference
TBD1 NRP-ID TLV [this document]

7. Normative References

Rokui, R., Homma, S., Makhijani, K., Contreras, L. M., and J. Tantsura, "Definition of IETF Network Slices", Work in Progress, Internet-Draft, draft-ietf-teas-ietf-network-slice-definition-01, , <>.
Farrel, A., Drake, J., Rokui, R., Homma, S., Makhijani, K., Contreras, L. M., and J. Tantsura, "Framework for IETF Network Slices", Work in Progress, Internet-Draft, draft-ietf-teas-ietf-network-slices-12, , <>.
Saad, T., Beeram, V. P., Dong, J., Wen, B., Ceccarelli, D., Halpern, J., Peng, S., Chen, R., Liu, X., Contreras, L. M., Rokui, R., and L. Jalil, "Realizing Network Slices in IP/MPLS Networks", Work in Progress, Internet-Draft, draft-ietf-teas-ns-ip-mpls-00, , <>.
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <>.
Farrel, A., Vasseur, J.-P., and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC 4655, DOI 10.17487/RFC4655, , <>.
Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, DOI 10.17487/RFC5440, , <>.
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <>.
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, , <>.

Authors' Addresses

Quan Xiong
ZTE Corporation
No.6 Huashi Park Rd
Hubei, 430223
Shaofu Peng
ZTE Corporation
No.50 Software Avenue
Jiangsu, 210012
Vishnu Pavan Beeram
Juniper Networks
Tarek Saad
Juniper Networks