SPRING Working Group W. Jiang
Internet Draft China Mobile
Intended status: Standards Track C. Lin
Expires: December 20, 2024 New H3C Technologies
R. Chen
ZTE Corporation
June 21, 2024
Segment Routing Policy Extension for NRP
draft-jiang-spring-sr-policy-nrp-01
Abstract
Network Resource Partition (NRP), which is a subset of the resources
and associated policies in the underlay network. In networks with
multiple NRPs, an SR Policy can be associated with a particular NRP.
This document describes how the SR Policy extension for associated
NRP and the operational mechanisms function together.
Status of this Memo
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Table of Contents
1. Introduction...................................................3
1.1. Requirements Language.....................................3
2. Solution.......................................................4
3. SR Policy Extension for NRP....................................5
3.1. NRP ID of a Candidate Path................................5
3.2. Candidate Path Validity Verification......................6
3.3. Summary...................................................7
4. Steering into an SR Policy with NRP............................8
5. Manageability Considerations...................................8
6. Security Considerations........................................8
7. IANA Considerations............................................8
8. References.....................................................8
8.1. Normative References......................................8
8.2. Informative References....................................9
Acknowledgements.................................................10
Authors' Addresses...............................................11
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1. Introduction
A Segment Routing Policy (SR Policy) [RFC9256] is an ordered list of
segments (i.e., instructions) that represent a source-routed policy.
The headend node is said to steer a flow into an SR Policy. The
packets steered into an SR Policy have an ordered list of segments
associated with that SR Policy written into them. [RFC8660]
describes the representation and processing of this ordered list of
segments as an MPLS label stack for SR-MPLS, while [RFC8754] and
[RFC8986] describe the same for Segment Routing over IPv6 (SRv6)
with the use of the Segment Routing Header (SRH).
[RFC9543] provides the definition of IETF network slice for use
within the IETF and discusses the general framework for requesting
and operating IETF Network Slices, their characteristics, and the
necessary system components and interfaces.It also introduces the
concept Network Resource Partition (NRP), which is a subset of the
resources and associated policies in the underlay network.
As described in [I-D.ietf-teas-nrp-scalability], one scalable data
plane approach to support network slicing is to carry a dedicated
NRP ID in the data packet to identify the NRP the packet belongs to,
so that the packet can be processed and forwarded using the subset
of network resources allocated to the NRP.
In networks with multiple NRPs, an SR Policy can be associated with
a particular NRP. This document describes how the SR Policy
extension for associated NRP and the operational mechanisms function
together.
1.1. 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.
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2. Solution
----------------------------------------
( |PE|.............|PE|.............|PE| )
( -- SR Policy-1 -- SR Policy-1 -- )<---------+
---------------------------------------- |
SR Policy-1 with NRP 1 |
|
---------------------------------------- |
( |PE|..............................|PE| ) |
( -- SR Policy-2 -- )<-------+
---------------------------------------- |
SR Policy-2 with NRP 2 |
|
---------------------------------------------- |
( |PE|.....-.....|PE|...... |PE|.......|PE| ) |
( -- |P| -- :-...:-- -..:-- ) |
( : -:.............|P|.........|P| )--+
( -......................:-:..- - )
( |P|.........................|P|......: )
( - - )
----------------------------------------------
Underlay Network
Figure 1: Solution of SR Policy Extension for NRP
In each NRP for network slices, the connectivity among PEs is
achieved by SR Policies. The segment lists of these SR Policies
composed with segments associated with the corresponding NRPs.
Traffics are steered into the SR Policies, so that the corresponding
NRPs will be used for forwarding.
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Physical Interface 1
+---------------------------------------+
| |
| Layer-3 Sub-interface 1-1: 1Gbps |
|=======================================|
|>>>>>> Queue 1-1: NRP-1, 100Mbps >>>>>>|
|>>>>>> Queue 1-2: NRP-2, 200Mbps >>>>>>|
|>>>>>> ... >>>>>>|
|=======================================|
| |
| Layer-3 Sub-interface 1-2: 2Gbps |
|====================================== |
|>>>>>> Queue 1-1: NRP-1, 100Mbps >>>>>>|
|>>>>>> Queue 1-2: NRP-2, 200Mbps >>>>>>|
|>>>>>> ... >>>>>>|
|=======================================|
| |
+---------------------------------------+
Figure 2: Network Resource Partition
As shown in Figure 2, the bandwidth resource of a physical interface
is partitioned in two NRPs.
The NRPs are sliced by HQoS queues with dedicated bandwidth under
the layer-3 sub-interface. NRP needs to be identified by using an
extra dimension. On both MPLS-SR and SRv6 data plane, there are
several options for realizing NRP-ID, such as [I-D.ietf-6man-
enhanced-vpn-vtn-id], [I-D.cheng-spring-srv6-encoding-network-
sliceid], [I-D.decraene-mpls-slid-encoded-entropy-label-id], and [I-
D.li-mpls-enhanced-vpn-vtn-id]. As mentioned above, the traffics of
network slice are forwarded according to the segment list of SR
Policy. Firstly, the outgoing interface associated segment will be
the layer-3 sub-interface. Then, the HQoS queue will be selected
according to the NRP-ID carried in the packets, and the bandwidth
resource of NRP will be used.
3. SR Policy Extension for NRP
The SR Policy determines the path that packets will traverse, while
NRP reserves resources along the path designated by the SR Policy.
Through the integration of SR Policy and NRP, it ensures both the
forwarding path and resource reservation along the path.
3.1. NRP ID of a Candidate Path
The NRP ID of a candidate path is utilized to identify the resources
corresponding to the forwarding paths of all segment lists within an
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SR Policy. It is a 32-bit value serving as an identifier for the
Network Resource Partition. The NRP ID associated with a candidate
path of an SR Policy from a specific Protocol-Origin as specified
below:
o When provisioning is via configuration, it is specific to the
implementation's configuration model.
o When signaling is via PCEP, the method to uniquely signal an
individual candidate path along with its NRP ID is described in
[I-D.draft-dong-pce-pcep-nrp].
o When signaling is via BGP SR Policy, the method to uniquely
signal an individual candidate path along with its NRP ID is
described in [I-D.ietf-idr-sr-policy-nrp].It can be collected via
BGP-LS [I-D.draft-chen-idr-bgp-ls-sr-policy-nrp].
Under the same Candidate Path, all segment lists must share the same
NRP ID. While different Candidate Paths can have identical NRP IDs,
it is advisable for each candidate path within an SR Policy to
possess a unique NRP ID.
By associating NRP IDs with Candidate Paths, the assurance of both
the SR Policy's path and its resources is achieved. The process
involves the following steps:
o Planning the network topology resources and assigning NRP IDs.
o At the headend node, performing path arrangement. During the path
planning process of the SR Policy, resources are considered for
different candidate paths, and NRP IDs are configured under each
Candidate path to establish the association between the path and
resources.
3.2. Candidate Path Validity Verification
A candidate path is considered usable when it is valid, with the
validation rules outlined in Section 5 of [RFC9256]. When a
Candidate Path contains an NRP ID, a segment list of a candidate
path may be declared invalid if the resources corresponding to the
NRP ID on the segment list path do not exist. Additionally, if the
head-end is unable to perform path resolution for the first SID into
one or more outgoing interfaces and next-hops, along with the
corresponding NRP ID resources, the status of that segment list is
set to invalid.
When running fast detection protocols, such as Bidirectional
Forwarding Detection (BFD), the headend may compute and validate
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backup candidate paths and provision them into the forwarding plane
as a backup for the active path. In such cases, it is necessary to
include NRP encapsulation to detect the NRP resources along the
path, ensuring the availability of both the path and resources.
3.3. Summary
In summary, the information model is the following:
SR Policy POL1
Candidate Path CP1
Preference 200
NRP-ID 100
Segment List 1 <SID11...SID1i>, Weight 1
Segment List 2 <SID21...SID2j>, Weight 1
Segment List 3 <SID31...SID3k>, Weight 1
Candidate Path CP2
Preference 100
NRP-ID 200
Segment List 4 <SID41...SID4i>, Weight 1
Segment List 5 <SID51...SID5j>, Weight 1
Segment List 6 <SID61...SID6k>, Weight 1
SR Policy POL1 has two Candidate Paths, CP1 and CP2. CP1 is the
active candidate path (valid and with the highest Preference). NRP-
ID 100 is configured under CP1, while NRP-ID 200 is configured under
CP2. The three segment lists of CP1 with NRP-ID 100 are installed as
the forwarding instantiation of SR Policy POL1. NRP-ID 100 needs to
be configured and resources reserved on the paths traversed by
segment list 1, segment list 2, and segment list 3. When traffic is
steered on POL1 and flow-based hashed on segment list
<SID11...SID1i>, NRP-100 is added, and forwarding is based on the
resources pointed to by NRP-100.
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4. Steering into an SR Policy with NRP
The method of traffic steering aligns with the description in
Section 8 of [RFC9256]. When an SR policy's active path contains an
NRP ID, specific handling is necessary, as follows:
o when steering traffic to the SR policy through Per-Destination
Steering or Policy-Based Routing, after adding the corresponding
segment list encapsulation for the SR policy, NRP encapsulation
is also required. The specific NRP encapsulation details are
outside the scope of this document.
o Similarly, When steering traffic to the SR policy via the
BindingSID, after adding the segment list encapsulation for the
SR policy, NRP encapsulation is required. The specific NRP
encapsulation details are outside the scope of this document.
5. Manageability Considerations
This document specifies the detailed construction of the SR Policy
with NRP-ID and its operational mechanisms. Therefore, the
manageability considerations of [RFC9256] apply.
6. Security Considerations
The security considerations described in [RFC9256] also apply to
this document.
This document does not introduce any new security consideration.
7. IANA Considerations
This document has no IANA actions.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI
10.17487/RFC2119, March 1997, <https://www.rfc-
editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
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[RFC9256] Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and
P. Mattes, "Segment Routing Policy Architecture", BCP 14,
RFC 9256, DOI 10.17487/RFC9256, July 2022, <
https://www.rfc-editor.org/info/rfc9256 >.
[I-D.ietf-teas-nrp-scalability]Dong, J., Li, Z., Gong, L., Yang,
G., Mishra, G. S., and F. Qin, "Scalability Considerations
for Network Resource Partition", Work in Progress,
Internet-Draft, draft-ietf-teas-nrp-scalability-03, 21
October 2023,<https://datatracker.ietf.org/doc/html/draft-
ietf-teas-nrp-scalability-03>.
8.2. Informative References
[I-D.ietf-teas-nrp-scalability] Dong, J., Li, Z., Gong, L., Yang,
G., Mishra, G. S., and F. Qin, "Scalability Considerations
for Network Resource Partition", Work in Progress,
Internet-Draft, draft-ietf-teas-nrp-scalability-03, 21
October 2023,<https://datatracker.ietf.org/doc/html/draft-
ietf-teas-nrp-scalability-03>.
[I-D.ietf-6man-enhanced-vpn-vtn-id] Dong, J., Li, Z., Xie, C., Ma,
C., and G. Mishra, "Carrying Virtual Transport Network
(VTN) Identifier in IPv6 Extension Header", Work in
Progress, Internet-Draft, draft-ietf-6man-enhanced-vpn-
vtn-id-00, 5 March 2022, <http://www.ietf.org/internet-
drafts/draft-ietf-6man-enhanced-vpn-vtn-id-00.txt>.
[I-D.cheng-spring-srv6-encoding-network-sliceid] Cheng, W., Lin, C.,
Gong, L., Zadok, S., and X. Wang, "Encoding Network Slice
Identification for SRv6", Work in Progress, Internet-
Draft, draft-cheng-spring-srv6-encoding-network-sliceid-
04, 8 July 2022, <http://www.ietf.org/internet-
drafts/draft-cheng-spring-srv6-encoding-network-sliceid-
04.txt>.
[I-D.decraene-mpls-slid-encoded-entropy-label-id] Decraene B.,
Filsfils, C., Henderickx W., Saad T., Beeram V., "Using
Entropy Label for Network Slice Identification in MPLS
networks", Work in Progress, Internet-Draft, draft-
decraene-mpls-slid-encoded-entropy-label-id-04, 14 June
2022, <http://www.ietf.org/internet-drafts/draft-decraene-
mpls-slid-encoded-entropy-label-id-04.txt>.
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[I-D.li-mpls-enhanced-vpn-vtn-id] Li, Z. and J. Dong, "Carrying
Virtual Transport Network Identifier in MPLS Packet", Work
in Progress, Internet-Draft, draft-li-mpls-enhanced-vpn-
vtn-id-02, 7 March 2022, <http://www.ietf.org/internet-
drafts/draft-li-mpls-enhanced-vpn-vtn-id-02.txt>.
[I-D. draft-dong-pce-pcep-nrp] Dong, J.,S. Fang,Q. Xiong,S. Peng,L.
Han, "Path Computation Element Communication Protocol
(PCEP) Extensions for Network Resource Partition (NRP)",
Work in Progress, Internet-Draft, draft-dong-pce-pcep-nrp-
01, 23 October 2023,
<https://www.ietf.org/archive/id/draft-dong-pce-pcep-nrp-
01.txt>.
[I-D.ietf-idr-sr-policy-nrp] Dong, J., Hu, Z., and R. Pang, "BGP SR
Policy Extensions for Network Resource Partition", Work in
Progress,Internet-Draft, draft-ietf-idr-sr-policy-nrp-00,
17 December 2023, <https://datatracker.ietf.org/doc/html/
draft-ietf-idr-sr-policy-nrp-00>.
[I-D.draft-chen-idr-bgp-ls-sr-policy-nrp] R. Chen, J. Dong, D. Zhao,
L. Gong, Y. Zhu and R. Pang, "SR Policies Extensions for
Network Resource Partition in BGP-LS", Work in
Progress,Internet-Draft, draft-chen-idr-bgp-ls-sr-policy-
nrp-08,18 May 2024,<https://www.ietf.org/archive/id/draft-
chen-idr-bgp-ls-sr-policy-nrp-08.txt>.
Acknowledgements
TBD
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Authors' Addresses
Wenying Jiang
China Mobile
Beijing
China
Email: jiangwenying@chinamobile.com
Changwang Lin
New H3C Technologies
Beijing
China
Email: linchangwang.04414@h3c.com
Ran Chen
ZTE Corporation
Email: chen.ran@zte.com.cn
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