Internet DRAFT - draft-dong-idr-sr-policy-nrp
draft-dong-idr-sr-policy-nrp
IDR Working Group J. Dong
Internet-Draft Z. Hu
Intended status: Standards Track Huawei Technologies
Expires: 25 April 2024 R. Pang
China Unicom
23 October 2023
BGP SR Policy Extensions for Network Resource Partition
draft-dong-idr-sr-policy-nrp-04
Abstract
Segment Routing (SR) Policy is a set of candidate paths, each
consisting of one or more segment lists and the associated
information. The header of a packet steered in an SR Policy is
augmented with an ordered list of segments associated with that SR
Policy. A Network Resource Partition (NRP) is a subset of network
resources allocated in the underlay network which can be used to
support one or a group of RFC XXXX network slice services.
In networks where there are multiple NRPs, an SR Policy may be
associated with a particular NRP. The association between SR Policy
and NRP needs to be specified, so that for service traffic which is
steered into the SR Policy, the header of the packets can be
augmented with the information associated with the NRP. An SR Policy
candidate path can be distributed using BGP SR Policy. This document
defines the extensions to BGP SR policy to specify the NRP which the
SR Policy candidate path is associated with.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 25 April 2024.
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Copyright Notice
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This document is subject to BCP 78 and the IETF Trust's Legal
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. NRP Identifier of SR Policy . . . . . . . . . . . . . . . . . 3
3. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Scalability Considerations . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
RFC Editor Note: Please replace "RFC XXXX" in this document with the
RFC number assigned to [I-D.ietf-teas-ietf-network-slices], and
remove this note.
The concept of Segment Routing (SR) policy is defined in [RFC9256].
An SR Policy is a set of candidate paths, each consisting of one or
more segment lists. The head end of an SR Policy may learn multiple
candidate paths for an SR Policy. The header of a packet steered in
an SR Policy is augmented with an ordered list of segments associated
with that SR Policy. The BGP extensions to distribute SR Policy
candidate paths is defined in
[I-D.ietf-idr-segment-routing-te-policy].
[I-D.ietf-teas-ietf-network-slices] introduces the concept and the
characteristics of RFC XXXX network slice, and describes a general
framework for RFC XXXX network slice management and operation. It
also introduces the concept Network Resource Partition (NRP), which
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is a subset of the resources and associated policies in the underlay
network. RFC XXXX network slice can be realized by mapping one or
more connectivity constructs to an NRP. [I-D.ietf-teas-enhanced-vpn]
describes the framework and the candidate component technologies for
providing enhanced VPN (VPN+) services based on VPN and Traffic
Engineering (TE) technologies. Enhanced VPN (VPN+) can be used for
the realization of RFC XXXX network slices. In the context of
network slicing, an NRP is considered as an instantiation of the VTN
as defined in [I-D.ietf-teas-enhanced-vpn].
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 where there are multiple NRPs, an SR Policy may be
associated with a particular NRP. The association between SR Policy
and NRP needs to be specified, so that for service traffic which is
steered into the SR Policy, the header of the packets can be
augmented with the information associated with the NRP. An SR Policy
candidate path can be distributed using BGP SR Policy. This document
defines the extensions to BGP SR policy to specify the NRP which the
SR Policy candidate path is associated with.
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
BCP14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. NRP Identifier of SR Policy
In order to specify the NRP the candidate path of SR policy is
associated with, a new sub-TLV called "NRP sub-TLV" is defined in the
BGP Tunnel Encapsulation Attribute [RFC9012]. The NRP sub-TLV can be
carried in the BGP Tunnel Encapsulation Attribute with the tunnel
type set to SR Policy.
The NRP sub-TLV is optional and MUST NOT appear more than once for
one SR Policy candidate path. If the NRP sub-TLV appears more than
once, the associated BGP SR Policy NLRI is considered malformed and
the "treat-as-withdraw" strategy of [RFC7606] is applied.
The NRP sub-TLV has the following format:
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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 | Length | Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NRP ID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1. NRP Sub-TLV
where:
* Type: 123
* Length: 6
* Flags: 1-octet flag field. None is defined at this stage. The
flags SHOULD be set to zero on transmission and MUST be ignored on
receipt.
* RESERVED: 1 octet of reserved bits. It SHOULD be set to zero on
transmission and MUST be ignored on receipt.
* NRP ID: A 32-bit domain significant identifier which is used to
identify an NRP. Value 0 and 0xFFFFFFFF are reserved.
The encoding structure of BGP SR Policy with the NRP sub-TLV is
expressed as below:
SR Policy SAFI NLRI: <Distinguisher, Policy-Color, Endpoint>
Attributes:
Tunnel Encaps Attribute (23)
Tunnel Type: SR Policy (15)
Binding SID
SRv6 Binding SID
Preference
Priority
Policy Name
Policy Candidate Path Name
Explicit NULL Label Policy (ENLP)
NRP
Segment List
Weight
Segment
Segment
...
...
Figure 2. SR Policy Encoding with NRP sub-TLV
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3. Procedures
When a candidate path of SR Policy is instantiated with a specific
NRP, the originating node of SR Policy SHOULD include the NRP sub-TLV
in the BGP Tunnel Encapsulation Attribute of the BGP SR Policy. The
setting of other fields and attributes in BGP SR Policy SHOULD follow
the mechanism as defined in [I-D.ietf-idr-segment-routing-te-policy].
On reception of an SR Policy NLRI, a BGP speaker determines if it is
acceptable and usable according to the rules defined in Section 4.2
of [I-D.ietf-idr-segment-routing-te-policy]. If the SR Policy
candidate path selected as the best candidate path is associated with
an NRP, the headend node of the SR Policy SHOULD encapsulate the NRP
ID and the segment list of the selected candidate path in the header
of packets which are steered to the SR Policy. For SR Policy with
IPv6 data plane, the approach to encapsulate the NRP ID in IPv6 Hop-
by-Hop Options header is defined in
[I-D.ietf-6man-enhanced-vpn-vtn-id]. For SR Policy with MPLS data
plane, one approach to encapsulate the NRP ID to the packet is
defined in [I-D.li-mpls-enhanced-vpn-vtn-id].
Although the proposed mechanism allows that different candidate paths
in one SR policy be associated with different NRPs, in normal network
scenarios it is considered that the association between an SR Policy
and NRP is consistent, in such case all candidate paths of one SR
policy SHOULD be associated with the same NRP.
4. Scalability Considerations
The mechanism specified in this document adds additional information
to the SR Policy candidate paths. In order to steer traffic into
different NRPs using SR Policy, the SR Policies used for different
NRPs need to be different. As the number of NRP increases, the
number of SR Policies would also increase accordingly. When BGP is
used for distributing SR Policy candidate paths, the amount of
control plane information exchanged between the network controller
and the headend nodes would also increase. However, since the SR
Policies candidate paths distributed in BGP are only installed by the
corresponding headend nodes, the impacts to the BGP control plane are
considered acceptable.
5. Security Considerations
The security considerations of BGP [RFC4271] and BGP SR policy
[I-D.ietf-idr-segment-routing-te-policy] apply to this document.
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6. IANA Considerations
IANA has assigned the sub-TLV type as defined in Section 2 from "BGP
Tunnel Encapsulation Attribute sub-TLVs" registry.
Value Description Reference
----------------------------------------------------
123 NRP This document
7. Acknowledgments
The authors would like to thank Guoqi Xu, Lei Bao, Haibo Wang and
Shunwan Zhuang for their review and discussion of this document.
8. References
8.1. Normative References
[I-D.ietf-idr-segment-routing-te-policy]
Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P., and
D. Jain, "Advertising Segment Routing Policies in BGP",
Work in Progress, Internet-Draft, draft-ietf-idr-segment-
routing-te-policy-25, 26 September 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-
segment-routing-te-policy-25>.
[I-D.ietf-teas-enhanced-vpn]
Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A
Framework for Enhanced Virtual Private Network (VPN+)",
Work in Progress, Internet-Draft, draft-ietf-teas-
enhanced-vpn-14, 28 July 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-
enhanced-vpn-14>.
[I-D.ietf-teas-ietf-network-slices]
Farrel, A., Drake, J., Rokui, R., Homma, S., Makhijani,
K., Contreras, L. M., and J. Tantsura, "A Framework for
Network Slices in Networks Built from IETF Technologies",
Work in Progress, Internet-Draft, draft-ietf-teas-ietf-
network-slices-25, 14 September 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-
ietf-network-slices-25>.
[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>.
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[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>.
[RFC7606] Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K.
Patel, "Revised Error Handling for BGP UPDATE Messages",
RFC 7606, DOI 10.17487/RFC7606, August 2015,
<https://www.rfc-editor.org/info/rfc7606>.
[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>.
[RFC9012] Patel, K., Van de Velde, G., Sangli, S., and J. Scudder,
"The BGP Tunnel Encapsulation Attribute", RFC 9012,
DOI 10.17487/RFC9012, April 2021,
<https://www.rfc-editor.org/info/rfc9012>.
[RFC9256] Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov,
A., and P. Mattes, "Segment Routing Policy Architecture",
RFC 9256, DOI 10.17487/RFC9256, July 2022,
<https://www.rfc-editor.org/info/rfc9256>.
8.2. Informative References
[I-D.ietf-6man-enhanced-vpn-vtn-id]
Dong, J., Li, Z., Xie, C., Ma, C., and G. S. Mishra,
"Carrying Virtual Transport Network (VTN) Information in
IPv6 Extension Header", Work in Progress, Internet-Draft,
draft-ietf-6man-enhanced-vpn-vtn-id-05, 6 July 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-6man-
enhanced-vpn-vtn-id-05>.
[I-D.ietf-teas-nrp-scalability]
Dong, J., Li, Z., Gong, L., Yang, G., Guichard, J.,
Mishra, G. S., Qin, F., Saad, T., and V. P. Beeram,
"Scalability Considerations for Network Resource
Partition", Work in Progress, Internet-Draft, draft-ietf-
teas-nrp-scalability-02, 2 June 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-
nrp-scalability-02>.
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[I-D.li-mpls-enhanced-vpn-vtn-id]
Li, Z. and J. Dong, "Carrying Virtual Transport Network
(VTN) Information in MPLS Packet", Work in Progress,
Internet-Draft, draft-li-mpls-enhanced-vpn-vtn-id-03, 16
October 2022, <https://datatracker.ietf.org/doc/html/
draft-li-mpls-enhanced-vpn-vtn-id-03>.
Authors' Addresses
Jie Dong
Huawei Technologies
Email: jie.dong@huawei.com
Zhibo Hu
Huawei Technologies
Email: huzhibo@huawei.com
Ran Pang
China Unicom
Email: pangran@chinaunicom.cn
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