Segment Routing based Solution for Hierarchical IETF Network Slices
draft-gong-teas-hierarchical-slice-solution-02
| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Liyan Gong , Weiqiang Cheng , Changwang Lin , Mengxiao Chen , Jie Dong , Ran Chen , Yanrong Liang | ||
| Last updated | 2023-07-06 | ||
| RFC stream | (None) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
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| Send notices to | (None) |
draft-gong-teas-hierarchical-slice-solution-02
Network Working Group L. Gong
Internet Draft W. Cheng
Intended status: Informational China Mobile
Expires: January 9, 2023 C. Lin
M. Chen
New H3C Technologies
J. Dong
Huawei Technologies
R. Chen
ZTE Corporation
Y. Liang
Ruijie Networks Co., Ltd.
July 9, 2023
Segment Routing based Solution for Hierarchical IETF Network Slices
draft-gong-teas-hierarchical-slice-solution-02
Abstract
This document describes a Segment Routing based solution for two-
level hierarchical IETF network slices. Level-1 network slice is
realized by associating Flex-Algo with dedicated sub-interfaces, and
level-2 network slice is realized by using SR Policy with additional
NRP-ID on data plane.
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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material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 9, 2023.
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Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction...................................................2
1.1. Requirements Language.....................................4
2. Solution based on Segment Routing..............................4
3. Example........................................................7
4. Security Considerations.......................................11
5. IANA Considerations...........................................11
6. References....................................................11
6.1. Normative References.....................................11
6.2. Informative References...................................12
Authors' Addresses...............................................14
1. Introduction
Network slicing provides the ability to partition a physical network
into multiple isolated logical networks of varying sizes,
structures, and functions so that each slice can be dedicated to
specific services or customers. [I-D.ietf-teas-ietf-network-slices]
defines the term "IETF Network Slice" and establishes the general
principles of network slicing in the IETF context. A Network
Resource Partition (NRP) is a collection of resources in the
underlay network. Each NRP is used as the underlay network construct
to support one or a group of IETF network slice services.
Hierarchical composition of IETF Network Slice means that a network
slice can be further sliced into other network slices. Figure 1
shows the architecture of two-level hierarchical IETF network
slices. Network resources are partitioned in a hierarchical manner.
Network resources of the underlay network are partitioned into
multiple level-1 network slices. Then network resources of a level-1
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network slice are further partitioned into multiple level-2 network
slices.
+-------------------+
| Underlay |
| Network |
+---------+---------+
|
+-------------+-------------+
| |
V V
+-----------+ +-----------+
| Level-1 | | Level-1 |
| Network | | Network |
| Slice | | Slice |
| 1 | | 2 |
+-----+-----+ +-----+-----+
| |
+------+------+ +------+------+
| | | |
V V V V
+---------+ +---------+ +---------+ +---------+
| Level-2 | | Level-2 | | Level-2 | | Level-2 |
| Network | | Network | | Network | | Network |
| Slice | | Slice | | Slice | | Slice |
| 1-1 | | 1-2 | | 2-1 | | 2-2 |
+---------+ +---------+ +---------+ +---------+
Figure 1: Architecture of Two-level Hierarchical IETF Network Slices
[I-D.dong-teas-hierarchical-ietf-network-slice] describes several
possible scenarios of hierarchical IETF network slices. For example,
level-1 can be industry slices which are used to deliver services
for different vertical industries, and level-2 can be customer
slices which are created to meet specific requirements of some or
all of the customers within the corresponding industry of level-1.
For the two-level hierarchical IETF network slices discussed in this
document, the level-1 and level-2 network slices are both created
and managed by the same operator, and they are used to provide
services at different granularity.
Segment Routing (SR) [RFC8402] is a source routing paradigm that
explicitly indicates the forwarding path for packets at the ingress
node. IETF network slices may be realized by using Segment Routing
technologies.
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This document proposes a Segment Routing based solution for two-
level hierarchical IETF network slices. Level-1 network slice is
realized by associating Flex-Algo with dedicated sub-interfaces, and
level-2 network slice is realized by using SR Policy with additional
NRP-ID on data plane.
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.
2. Solution based on Segment Routing
Flex-Algo is a mechanism that allows IGP to compute the best paths
along the constrained topology in a distributed manner. [I-D.ietf-
lsr-flex-algo] specifies the way of using Segment Routing (SR)
Prefix-SIDs and SRv6 locators to steer packets for Flex-Algo.
As shown in Figure 2, each NRP for level-1 network slices is
associated with a Flex-Algo. All the nodes belong to the level-1 NRP
participate in the associated Flex-Algo. All the links belong to the
level-1 NRP are included by the Admin Group rules of the associated
Flex-Algo. Traffics of the level-1 network slices are steered into
the Flex-Algo paths by using Prefix-SIDs or SRv6 locators, so that
the corresponding level-1 NRPs will be used for forwarding.
Segment Routing Policy (SR Policy) is an ordered list of segments
that represent a source-routed policy [I-D.ietf-spring-segment-
routing-policy]. The packets steered into an SR Policy carry an
ordered list of segments associated with that SR Policy.
In each NRP for level-2 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 Flex-Algo
of the level-1 NRP. So, the level-2 forwarding paths are restricted
in the level-1 topology. Traffics of the level-2 network slice are
steered into the SR Policies, so that the corresponding level-2 NRPs
will be used for forwarding.
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----------------------------------------
( |PE|.............|PE|.............|PE| )
( -- SR Policy -- SR Policy -- )<--+
---------------------------------------- |
Level-2 NRP 1-1 |
|
---------------------------------------- |
( |PE|..............................|PE| ) |
( -- SR Policy -- )<--+
---------------------------------------- |
Level-2 NRP 1-2 |
|
----------------------------------------- |
( |PE|.......|PE|........|PE|.......|PE| )--+
( --: -- :-- -- )
( : - : )<-------+
( :........|P|........: Flex-Algo 128 ) |
----------------------------------------- |
Level-1 NRP 1 |
|
----------------------------------------- |
( |PE|..................|PE| ) |
( --: :-- ) |
( -: :- )<-------+
( |P|..................|P| Flex-Algo 129 ) |
----------------------------------------- |
Level-1 NRP 2 |
|
---------------------------------------------- |
( |PE|.....-.....|PE|...... |PE|.......|PE| ) |
( -- |P| -- :-...:-- -..:-- ) |
( : -:.............|P|.........|P| )--+
( -......................:-:..- - )
( |P|.........................|P|......: )
( - - )
----------------------------------------------
Underlay Network
Figure 2: Framework of Solution
The network resources for the two-level network slices are also
partitioned in a hierarchical manner.
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Physical Interface 1
+-------------------------------------------+
| |
| Layer-3 Sub-interface 1-1: NRP-1, 1Gbps |
|===========================================|
|>>>>>> Queue 1-1-1: NRP-1-1, 100Mbps >>>>>>|
|>>>>>> Queue 1-1-2: NRP-1-2, 200Mbps >>>>>>|
|>>>>>> ... >>>>>>|
|===========================================|
| |
| Layer-3 Sub-interface 1-2: NRP-2, 2Gbps |
|===========================================|
|>>>>>> Queue 1-2-1: NRP-2-1, 100Mbps >>>>>>|
|>>>>>> Queue 1-2-2: NRP-2-2, 200Mbps >>>>>>|
|>>>>>> ... >>>>>>|
|===========================================|
| |
+-------------------------------------------+
Figure 3: Hierarchical Network Resource Partition
As shown in Figure 3, the bandwidth resource of a physical interface
is partitioned in two levels.
The level-1 NRPs are sliced by layer-3 sub-interfaces with dedicated
bandwidth. The Admin Group of layer-3 sub-interface is included by
the Flex-Algo which is associated with the level-1 NRP. Meanwhile,
it is excluded or not included by irrelevant Flex-Algos. So, the
topology of a level-1 network slice consists of a set of layer-3
sub-interfaces with dedicated bandwidth of the relevant level-1 NRP.
When the traffics are forwarded according to Prefix-SIDs or SRv6
locators of the associated Flex-Algo, the corresponding bandwidth
resources are used.
The level-2 NRPs are sliced by HQoS queues with dedicated bandwidth
under the layer-3 sub-interface of level-1 NRP. Since the Flex-Algo
associated Prefix-SIDs or SRv6 locators are used as the data plane
identifier of level-1 NRP, level-2 NRP needs to be identified by
using an extra dimension. On both MPLS-SR and SRv6 data plane, there
are several options for realizing level-2 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
level-2 network slice are forwarded according to the segment list of
SR Policy. Firstly, the outgoing interface of the Flex-Algo
associated segment will be the layer-3 sub-interface of level-1 NRP.
Then, the HQoS queue will be selected according to the level-2 NRP-
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ID carried in the packets, and the bandwidth resource of level-2 NRP
will be used.
Each NRP can be used to support one or a group of network slice. If
multiple level-1 network slices need to share the same level-1 NRP,
those level-1 network slices should be associated to the same Flex-
Algo, while a single level-1 NRP is still mapped to a single Flex-
Algo. If multiple level-2 network slices need to share the same
level-2 NRP, the SR Polices for those level-2 network slices should
be associated to the same level-2 NRP-ID, and those level-2 network
slices must belong to the same level-1 network slice, or different
level-1 network slices which share the same level-1 NRP.
In the typical per-industrial-per-customer scenario of two-level
hierarchical network slices, NRP sharing among different slices may
be unnecessary. One-to-one mapping between network slice and NRP may
be easier for deployment.
3. Example
The example network in Figure 4 is used for illustration.
+---+ +---+ +---+
|PE1|-----|P1 |-----|PE2|
+---+ +---+ +---+
| |
| |
| |
+---+ |---| +---+
|P3 |-----|PE3|-----|P2 |
+---+ |---| +---+
Figure 4: Example Network
There are two level-1 network slices to be deployed, slice 1 for
education and slice 2 for healthcare. The customers of education
access from all PEs. The customers of healthcare access from PE1 and
PE2.
Under slice 1, two universities require separate slices for
interconnections among branch campuses. University 1 needs
interconnection between PE1 and PE2 and interconnection between PE1
and PE3. University 2 needs interconnection between PE1 and PE2.
Under slice 2, only one customer requires level-2 network slice.
Assume that the mapping between network slice and NRP is one to one.
The topology of NRPs for the above network slices is shown in Figure
5.
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Level-1 NRP 1 for Level-1 Network Slice 1:
PE1-----P1------PE2
| |
| |
| |
P3------PE3-----P2
Level-1 NRP 2 for Level-1 Network Slice 2:
PE1-----P1------PE2
Level-2 NRP 1-1 for Level-2 Network Slice 1-1:
PE1<----->PE2
^
|
+------>PE3
Level-2 NRP 1-2 for Level-2 Network Slice 1-2:
PE1<----->PE2
Level-2 NRP 2-1 for Level-2 Network Slice 2-1:
PE1<----->PE2
Figure 5: Topology of NRPs
The provider assigns Flex-Algo 128 and 129 respectively for the two
level-1 NRPs. All nodes participate in Flex-Algo 128. Only PE1, P1
and PE2 participate in Flex-Algo 129. Layer-3 sub-interfaces are set
up for level-1 NRPs. HQoS queues under the layer-3 sub-interfaces
are further set up for level-2 NRPs.
Taking PE1 as an example, the network resource partition of link
bandwidth is shown in Figure 6.
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+---+ Physical Interface 1 +---+
| |-------------------------------------------| |
| | Layer-3 Sub-interface 1-1: NRP-1, 1Gbps | |
| |===========================================| |
| |>>>>>> Queue 1-1-1: NRP-1-1, 100Mbps >>>>>>| |
| |>>>>>> Queue 1-1-2: NRP-1-2, 200Mbps >>>>>>| |
| |===========================================| |
| | |P1 |
| | Layer-3 Sub-interface 1-2: NRP-2, 2Gbps | |
| |===========================================| |
|PE1|>>>>>> Queue 1-2-1: NRP-2-1, 100Mbps >>>>>>| |
| |===========================================| |
| |-------------------------------------------| |
| | +---+
| |
| | Physical Interface 2 +---+
| |-------------------------------------------| |
| | Layer-3 Sub-interface 2-1: NRP-1, 1Gbps | |
| |===========================================|P3 |
| |>>>>>> Queue 2-1-1: NRP-1-1, 100Mbps >>>>>>| |
| |===========================================| |
| |-------------------------------------------| |
+---+ +---+
Figure 6: Network Resource Partition on PE1
Physical interface 1 on PE1 corresponds to link PE1-P1, and physical
interface 2 corresponds to link PE1-P3.
Under interface 1, there are two layer-3 sub-interfaces 1-1 and 1-2.
Sub-interfaces 1-1 is used as NRP-1 with dedicated bandwidth for
level-1 network slice 1. Using Admin Group rules, sub-interfaces 1-1
is associated with Flex-Algo 128. Traffics of level-1 network slice
1 are steered into Flex-Algo 128. When the packets are forwarded
from PE1 to P1, sub-interfaces 1-1 is selected as the outgoing
interface and associated bandwidth resource will be used. Similarly,
sub-interface 1-2 is used as NRP-2 for level-1 network slice 2, and
associated with Flex-Algo 129.
Under layer-3 sub-interfaces 1-1, two HQoS queues 1-1-1 and 1-1-2
are further used as NRP-1-1 and NRP-1-2, with dedicated bandwidth
for level-2 network slice 1-1 and 1-2. These queues are associated
with the NRP-ID. When packets are forwarded through sub-interfaces
1-1, level-2 NRP-ID in the packets will be checked. If level-2 NRP-
ID exists, the packet will be treated as level-2 network slice
traffic, and will be forwarded using the associated queue with
dedicated bandwidth for level-2 network slice. Similarly, HQoS queue
1-2-1 is used as NRP-2-1 for level-2 network slice 2-1.
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Under interface 2, only layer-3 sub-interface 2-1 for level-1
network slice 1 is configured, along with HQoS queue 2-1-1 for
level-2 network slice 1-1. NRPs for other network slices are not
necessary, since the link PE1-P3 is not involved in their
topologies.
If a packet from university 1 at PE1 needs to be forwarded to
university 2 at PE2, the level-1 network slice 1 for education will
be used, as shown in Figure 7. PE1 encapsulates the packet with an
outer IPv6 header, and the Destination Address in the outer header
is End SID for PE2 associated with Flex-Algo 128. Along the path
PE1->P1->PE2, the packet is forwarded through layer-3 sub-interface
associated with Flex-Algo 128, using dedicated bandwidth for the
level-1 network slice 1.
If a packet from a branch campus of university 1 at PE1 needs to be
forwarded to another branch campus of the same university at PE2,
the level-2 network slice 1-1 for university 1 will be used, as
shown in Figure 8. Assume that the level-2 NRP-ID is carried in HBH.
PE1 encapsulates the packet with an outer IPv6 header, along with
HBH and SRH. The SRH carries the segment-list of SR Policy to PE2,
and the SIDs are all associated with Flex-Algo 128. The HBH carries
the level-2 NRP-ID associated with level-2 network slice 1-1. Along
the path PE1->P1->PE2, the packet is forwarded through the HQoS
queue associated with the level-2 NRP-ID, under the layer-3 sub-
interface associated with Flex-Algo 128. The dedicated bandwidth for
level-2 network slice 1-1 will be used, other than sharing the
bandwidth for level-1 network slice 1.
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+------------+ +------------+
| IPv6 | | IPv6 |
| DA=End-PE2 | | DA=End-PE2 |
| (FA-128) | | (FA-128) |
+-------+ +------------+ +------------+ +-------+
|Payload| --> | Payload | --> | Payload | --> |Payload|
+-------+ PE1 +------------+ P1 +------------+ PE2 +-------+
Figure 7: Packet Forwarding of Level-1 Network Slice 1
+------------+ +------------+
| IPv6 | | IPv6 |
+------------+ +------------+
| HBH | | HBH |
| NRP-1-1 | | NRP-1-1 |
+------------+ +------------+
| SRH | | SRH |
|End.DT | |End.DT |
|End.X-P1-PE2| |End.X-P1-PE2|
|End.X-PE1-P1| |End.X-PE1-P1|
|(FA-128) | |(FA-128) |
+-------+ +------------+ +------------+ +-------+
|Payload| --> | Payload | --> | Payload | --> |Payload|
+-------+ PE1 +------------+ P1 +------------+ PE2 +-------+
Figure 8: Packet Forwarding of Level-2 Network Slice 1-1
4. Security Considerations
TBD.
5. IANA Considerations
This document has no IANA actions.
6. References
6.1. 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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[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[I-D.ietf-teas-ietf-network-slices] 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, 30 June 2022,
<https://www.ietf.org/archive/id/draft-ietf-teas-ietf-
network-slices-12.txt>.
[I-D.ietf-lsr-flex-algo] Psenak, P., Hegde, S., Filsfils, C.,
Talaulikar, K., and A. Gulko, "IGP Flexible Algorithm",
draft-ietf-lsr-flex-algo-20 (work in progress), May 2022.
[I-D.ietf-spring-segment-routing-policy] Filsfils, C., Talaulikar,
K., Voyer, D., Bogdanov, A., and P. Mattes, "Segment
Routing Policy Architecture", Work in Progress, Internet-
Draft, draft-ietf-spring-segment-routing-policy-22, 22
March 2022, <http://www.ietf.org/internet-drafts/draft-
ietf-spring-segment-routing-policy-22.txt>.
6.2. Informative References
[I-D.dong-teas-hierarchical-ietf-network-slice] Dong, J., and Z. Li,
"Considerations about Hierarchical IETF Network Slices",
Work in Progress, Internet-Draft, draft-dong-teas-
hierarchical-ietf-network-slice-01, 7 March 2022,
<http://www.ietf.org/internet-drafts/draft-dong-teas-
hierarchical-ietf-network-slice-01.txt>.
[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>.
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[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>.
[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>.
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Authors' Addresses
Liyan Gong
China Mobile
Email: gongliyan@chinamobile.com
Weiqiang Cheng
China Mobile
Email: chengweiqiang@chinamobile.com
Changwang Lin
New H3C Technologies
Email: linchangwang.04414@h3c.com
Mengxiao Chen
New H3C Technologies
Email: chen.mengxiao@h3c.com
Jie Dong
Huawei Technologies
Email: jie.dong@huawei.com
Ran Chen
ZTE Corporation
Email: chen.ran@zte.com.cn
Yanrong Liang
Ruijie Networks Co., Ltd.
Email: liangyanrong@ruijie.com.cn
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