Considerations about Hierarchical IETF Network Slices
draft-dong-teas-hierarchical-ietf-network-slice-00
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| Authors | Jie Dong , Zhenbin Li | ||
| Last updated | 2021-10-25 | ||
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draft-dong-teas-hierarchical-ietf-network-slice-00
TEAS Working Group J. Dong
Internet-Draft Z. Li
Intended status: Informational Huawei Technologies
Expires: 28 April 2022 25 October 2021
Considerations about Hierarchical IETF Network Slices
draft-dong-teas-hierarchical-ietf-network-slice-00
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). The framework of IETF network slice can support
hierarchical network slicing. And in some network scenarios, there
may be requirements for the deployment of hierarchical network
slices.
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 support hierarchical
network slicing.
Status of This Memo
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This Internet-Draft will expire on 28 April 2022.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
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license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
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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 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 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. However, there is no detailed description
about hierarchical IETF network slices scenarios and requirements.
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 support hierarchical network slicing.
2. Scenarios of Hierarchical IETF Network Slices
In this section, several 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 requirement
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, it is
expected that 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 resource partitioning,
the data plane encapsulations, the control plane protocols and the
management plane are analyzed.
3.1. Forwarding Resource Partitioning
For the realization of IETF network slices, the network resources in
the underlying forwarding plane needs to be partitioned into
different subsets, each subset is used to build the underlay
construct to support one or a group of IETF network slice services.
In order to support hierarchical network slices, the forwarding plane
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 the
modeling the interface bandwidth resource partitioning.
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The first option is to treat the first-level network resource
partitions as a set of layer-3 interfaces or sub-interfaces with
dedicated network resources, and the second-level network resource
partitions are represented as virtual layer-2 data channels, 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 Interface Resource Partition: Option 1
The second option is to treat the first-level network resource
partitions as a virtual layer-2 sub-interface of the layer-3
interface, and the second-level network resource partition is
represented as a virtual data channel under the virtual 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 Interface Resource Parition, Option 2
The options of the resource partition modeling may have impact to the
amount 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
virtual underlay construct based on one or multiple fields in the
data packet, so that the set of network resources are used for
processing and forwarding the packet. On the network edge nodes,
traffic flows can be classified and mapped to IETF network slices
based on the matching rules according to operators' local policy.
While on the intermediate nodes, a dedicated data plane identifier
can facilitate the identification of the set of network resources
associated with the virtual underlay on the network nodes for packet
processing.
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For hierarchical network slices, such data plane identifiers may need
to be able to identify both the first-level resource partition and
the second-level resource partition. There are several options for
the data plane resource identifier for hierarchical network slices.
The first option is to use a unified identifier for both the first-
level resource partition and the second-level resource partition. In
this case, the first-level resource partitions and the second-level
resource partitions are identified by distinct identifier values.
+-----------------------------------------+
| Unified Resource ID for different levels|
+-----------------------------------------+
Figure 6. Unified Resource ID
The second option is to use a hierarchical identifier for the first-
level resource partition and the second level resource partition. In
this case, the first part of the Resource ID is used to identify the
first-level resource partition, and the second part of the resource
ID is used to identify the second-level resource partition. Depends
on the data plane technologies used, the hierarchical resource
identifier may be positioned in a continuous field in the packet, or
maybe positioned in separate fields.
+--------------------+--------------------+
| Level-1 Resource ID| Level-2 Resource ID|
+--------------------+--------------------+
Figure 7. Hierarchical Resource ID
3.3. Control Plane
The control plane may be used for the distribution of the resource
partition information and the associated data plane identifiers among
the network nodes and to the network controller. With different
resource partition modeling, the information may be advertised as
either layer-3 or layer-2 network information, which can have
different scalability implications to the control plane. As the
number of both the level-1 network slices and level-2 network slices
increases, some control plane mechanisms may be needed to adopt to
the amount of network slice information to be advertised.
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3.4. Management Plane
Depends on the scenarios of hierarchical network slicing, the
management system of network operator may need to support additional
functions and procedures for the life-cycle management of
hierarchical network slices. The detailed analysis about the
requirement on 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 XXX for the review and discussion of
this document.
8. References
8.1. Normative References
[I-D.ietf-teas-ietf-network-slices]
Farrel, A., Gray, E., 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-04, 23
August 2021, <https://www.ietf.org/archive/id/draft-ietf-
teas-ietf-network-slices-04.txt>.
8.2. Informative References
[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-08, 12 July 2021,
<https://www.ietf.org/archive/id/draft-ietf-teas-enhanced-
vpn-08.txt>.
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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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