Internet DRAFT - draft-dong-teas-hierarchical-ietf-network-slice
draft-dong-teas-hierarchical-ietf-network-slice
TEAS Working Group J. Dong
Internet-Draft Z. Li
Intended status: Informational Huawei Technologies
Expires: 8 September 2022 7 March 2022
Considerations about Hierarchical IETF Network Slices
draft-dong-teas-hierarchical-ietf-network-slice-01
Abstract
Network slicing is targeted at existing or emerging customers or
services which may request for network connectivity services with a
specific set of Service Level Objectives (SLOs) and Service Level
Expectations (SLEs). In some network scenarios, there can be
requirements for the deployment of hierarchical network slices.The
general framework of IETF network slice supports hierarchical network
slicing, while the technologies for realizing hierarchical IETF
network slice need to be considered.
This document describes the typical scenarios of hierarchical IETF
network slices, and provides the considerations and requirements on
the technologies in different network planes to realize hierarchical
IETF network slices.
Status of This Memo
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This Internet-Draft will expire on 8 September 2022.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Scenarios of Hierarchical IETF Network Slices . . . . . . . . 3
2.1. Per-Customer Network Slices in an Industrial Network
Slice . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Per-application Network Slices in a Customer Network
Slice . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3. Network Slice Services in a Wholesale Network Slice . . . 5
3. Considerations about Hierarchical Network Slice
Realization . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Forwarding Plane Network Resource Partitioning . . . . . 6
3.2. Data Plane Identifiers . . . . . . . . . . . . . . . . . 8
3.3. Control Plane . . . . . . . . . . . . . . . . . . . . . . 9
3.4. Management Plane . . . . . . . . . . . . . . . . . . . . 10
4. Security Considerations . . . . . . . . . . . . . . . . . . . 10
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 10
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Normative References . . . . . . . . . . . . . . . . . . 10
8.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
Network slicing is targeted at existing or emerging customers or
services which may request for network connectivity services with a
specific set of Service Level Objectives (SLOs) and Service Level
Expectations (SLEs). The concept and general framework of IETF
network slice are described in [I-D.ietf-teas-ietf-network-slices].
[I-D.ietf-teas-enhanced-vpn] describes the framework and technologies
which can be used for IETF network slice realization by utilizing
Virtual Private Network (VPN) and Traffic Engineering (TE) mechanisms
with enhancements that specific services require over traditional
VPNs.
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[I-D.ietf-teas-ietf-network-slices] mentions that IETF Network Slices
may be combined hierarchically, which means that a network slice may
itself be further sliced. The technologies for realizing
hierarchical IETF network slice need to be considered.
This document describes the typical scenarios in which the deployment
of hierarchical IETF network slices may be needed. This document
also provides the considerations and requirements on the technologies
in different network planes to realize hierarchical IETF network
slices.
2. Scenarios of Hierarchical IETF Network Slices
In this section, several possible network scenarios of hierarchical
IETF network slicing are introduced.
2.1. Per-Customer Network Slices in an Industrial Network Slice
One of the typical network slice deployment is in the multi-
industrial network case, in which a physical network is used to
deliver services of multiple vertical industries. Separate IETF
network slices are provided for different industries, such as health-
care, education, manufacturing, governmental affairs, etc. Then
within the network slice of a specific industry, there may be need to
create separate network slices for some or all of the customers
within this industry.
For example, within the education network slice, some of the
universities may require for a separate network slice to connect with
a set of the branch campuses. Another examples is within the health-
care network slice, some of the hospitals may require for a separate
network slice for the connectivity and services between a set of the
branch hospitals.
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---------------------------------/
/ Industry Slice 1 /
/ ----------------------- /
/ / Customer Slice 1 / /
/ -----------------------/ /
/ ----------------------- /
/ / Customer Slice 2 / /
/ -----------------------/ /
/ ... /
---------------------------------/
...
---------------------------------/
/ Industry Slice 2 /
/ ----------------------- /
/ / Customer Slice 1 / /
/ -----------------------/ /
/ ----------------------- /
/ / Customer Slice 2 / /
/ -----------------------/ /
/ ... /
---------------------------------/
Figure 1. Hierarchical Network Slices: Scenario 1
2.2. Per-application Network Slices in a Customer Network Slice
Another network slice deployment case is to provide dedicated IETF
network slices for some important customers as the first-level
network slices. While the customers may require to further split
their network slices into different sub-network slices for different
applications.
For example, a network slice for a hospital may be further divided to
carry different type of medical services, such as remote patient
monitoring, remote ultrasound diagnose, medical image transmission
etc.
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---------------------------------/
/ Customer Slice 1 /
/ ----------------------- /
/ / APP Slice 1 / /
/ -----------------------/ /
/ ----------------------- /
/ / APP Slice 2 / /
/ -----------------------/ /
/ ... /
---------------------------------/
...
---------------------------------/
/ Customer Slice 2 /
/ ----------------------- /
/ / APP Slice 1 / /
/ -----------------------/ /
/ ----------------------- /
/ / APP Slice 2 / /
/ -----------------------/ /
/ ... /
---------------------------------/
Figure 2. Hierarchical Network Slices: Scenario 2
2.3. Network Slice Services in a Wholesale Network Slice
IETF network slice can also be delivered as a wholesale service to
other network operators. In this case a network operator can be the
customer of a network slice, and it may also need to deliver IETF
network slice services to its customers. This is similar to the
Carrier's Carrier VPN service mode, while some additional
requirements on the SLOs and SLEs may be required by the second-level
network slice customer.
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---------------------------------/
/ Wholesale Slice 1 /
/ ----------------------- /
/ / Customer Slice 1 / /
/ -----------------------/ /
/ ----------------------- /
/ / Customer Slice 2 / /
/ -----------------------/ /
/ ... /
---------------------------------/
...
---------------------------------/
/ Wholesale Slice 2 /
/ ----------------------- /
/ / Customer Slice 1 / /
/ -----------------------/ /
/ ----------------------- /
/ / Customer Slice 2 / /
/ -----------------------/ /
/ ... /
---------------------------------/
Figure 3. Hierarchical Network Slices: Scenario 3
3. Considerations about Hierarchical Network Slice Realization
To support the realization of hierarchical network slices, there will
be specific requirements on the technologies used in each network
plane. In this section, the requirements of hierarchical network
slicing on the forwarding plane network resource partitioning, the
data plane encapsulations, the control plane protocols and the
management plane are analyzed.
3.1. Forwarding Plane Network Resource Partitioning
For the realization of IETF network slices, the network resources in
the underlying forwarding plane needs to be partitioned into
different network resource partitions (NRPs), each NRP is used as the
underlay network construct to support one or a group of IETF network
slice services. In order to support hierarchical network slices, the
forwarding plane network resources needs to be able to be partitioned
in a hierarchical manner. Taking a two-level hierarchical network
slice as an example, the bandwidth resource of a physical interface
needs to be partitioned in two levels. There can be different
options in modeling the interface resources of network resource
partition.
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The first option is to treat the network resources in the first-level
NRPs as a set of layer-3 sub-interfaces, each with dedicated link
bandwidth, and the second-level NRPs are represented as virtual data
channels under the layer-3 sub-interfaces, as shown in the figure
below:
+----------------------+
| +----------------+ |
| | +------------+ | |
| | |Data Channel| | |
| | +------------+ | |
| | ... | |
| | +------------+ | |
| | |Data Channel| | |
| | +------------+ | |
| +----------------+ |
| layer-3 subinterface |
| |
| . . . |
| +----------------+ |
| | +------------+ | |
| | |Data Channel| | |
| | +------------+ | |
| | ... | |
| | +------------+ | |
| | |Data Channel| | |
| | +------------+ | |
| +----------------+ |
| layer-3 subinterface |
+----------------------+
Physical Interface
Figure 4. Modeling of Network Resource Partition on Interface: Option 1
The second option is to treat the first-level NRPs as layer-2 sub-
interface of the layer-3 interface, and the second-level NRPs are
represented as virtual data channels under the layer-2 sub-interface,
as shown in the figure below:
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+----------------------+
| +----------------+ |
| | +------------+ | |
| | |Data Channel| | |
| | +------------+ | |
| | ... | |
| | +------------+ | |
| | |Data Channel| | |
| | +------------+ | |
| +----------------+ |
| layer-2 subinterface |
| |
| . . . |
| +----------------+ |
| | +------------+ | |
| | |Data Channel| | |
| | +------------+ | |
| | ... | |
| | +------------+ | |
| | |Data Channel| | |
| | +------------+ | |
| +----------------+ |
| layer-2 subinterface |
+----------------------+
Layer-3 Physical Interface
Figure 5. Modeling of Network Resource Partition on Interface, Option 2
The options of the network resource partition modeling may have
different impact to the control plane in terms of the number of
control protocol sessions to be maintained, and the amount and types
of information to be distributed in the control plane. Depends on
the network deployment requirements, different resource partition
modeling options may be used.
3.2. Data Plane Identifiers
Traffic of IETF network slices can be steered into the corresponding
underlay network construct based on one or multiple fields in the
data packet, so that the corresponding NRPs are used for processing
and forwarding the packet. On the edge nodes of an IETF network
slice, traffic flows can be classified and mapped to IETF network
slices using flexible matching rules based on operators' local
policy. While on the intermediate network nodes, a dedicated data
plane NRP Identifier [I-D.dong-teas-nrp-scalability] can facilitate
the identification of the NRP and the set of network resources
allocated on the network nodes for packet processing.
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For hierarchical IETF network slices, such data plane identifiers may
need to be able to identify both the first-level NRP and the second-
level NRP. There are several options in the design of the data plane
NRP identifier for hierarchical network slices.
The first option is to use a unified data plane identifier for both
the first-level NRP and the second-level NRP. In this case, the
first-level NRPs and the second-level NRPs are identified using
distinct identifier values.
+-----------------------------------------+
| Unified NRP ID for different levels |
+-----------------------------------------+
Figure 6. Unified NRP ID
The second option is to use a hierarchical identifiers for the first-
level NRP and the second-level NRP. In this case, the first part of
the identifier is used to identify the first-level NRP, and the
second part of the identifier is used to identify the second-level
NRP. Depends on the data plane technologies used, the hierarchical
NRP may be encapsulated in a continuous field in the packet, or may
be positioned in separate fields.
+--------------------+--------------------+
| Level-1 NRP ID | Level-2 NRP ID |
+--------------------+--------------------+
Figure 7. Hierarchical NRP IDs
3.3. Control Plane
The control plane may be used for the distribution of the attributes
and states of the hierarchical NRPs and the associated data plane
identifiers among network nodes in the NRP and also to the network
controller. With different NRP modeling, the information may be
advertised as either layer-3 or layer-2 network information, which
may have different scalability implications to the control plane.
And as the number of hierarchical network slices increases, some
control plane optimization mechanisms may be needed to adopt to the
amount of information advertised.
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3.4. Management Plane
For the management hierarchical network slices, the management system
of network operator needs to provide life-cycle management to both
the first-level network slices and the second-level network slices.
It should allow to manage the first-level and second-level network
slices separately, while the relationship between the first-level and
second-level network slices also need to be maintained in the
management system. The management system may need to support
additional functions and procedures for the management of
hierarchical network slices. Further analysis about the requirement
on the management plane is for further study.
4. Security Considerations
TBD
5. IANA Considerations
This document makes no request of IANA.
6. Contributors
Zhibo Hu
Email: huzhibo@huawei.com
7. Acknowledgments
The authors would like to thank Yawei Zhang for the review and
discussion of this document.
8. References
8.1. Normative References
[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-08, 6 March 2022,
<https://www.ietf.org/archive/id/draft-ietf-teas-ietf-
network-slices-08.txt>.
8.2. Informative References
[I-D.dong-teas-nrp-scalability]
Dong, J., Li, Z., Gong, L., Yang, G., Guichard, J. N.,
Mishra, G., Qin, F., Saad, T., and V. P. Beeram,
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"Scalability Considerations for Network Resource
Partition", Work in Progress, Internet-Draft, draft-dong-
teas-nrp-scalability-01, 7 February 2022,
<https://www.ietf.org/archive/id/draft-dong-teas-nrp-
scalability-01.txt>.
[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+)
Services", Work in Progress, Internet-Draft, draft-ietf-
teas-enhanced-vpn-09, 25 October 2021,
<https://www.ietf.org/archive/id/draft-ietf-teas-enhanced-
vpn-09.txt>.
Authors' Addresses
Jie Dong
Huawei Technologies
Huawei Campus, No. 156 Beiqing Road
Beijing
100095
China
Email: jie.dong@huawei.com
Zhenbin Li
Huawei Technologies
Huawei Campus, No. 156 Beiqing Road
Beijing
100095
China
Email: lizhenbin@huawei.com
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