Interconnecting Network Slice Subnets
draft-defoy-coms-subnet-interconnection-00
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| Authors | Xavier de Foy , Akbar Rahman | ||
| Last updated | 2017-10-03 | ||
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draft-defoy-coms-subnet-interconnection-00
none X. de Foy
Internet-Draft A. Rahman
Intended status: Informational InterDigital Inc.
Expires: April 6, 2018 October 3, 2017
Interconnecting Network Slice Subnets
draft-defoy-coms-subnet-interconnection-00
Abstract
This document aims to define a network slice subnet as a general
concept, and to augment a baseline network slice model with
attributes that describe interconnections between network slice
subnets.
Status of This Memo
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This Internet-Draft will expire on April 6, 2018.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Interconnection Concepts . . . . . . . . . . . . . . . . . . 3
3. Information Model . . . . . . . . . . . . . . . . . . . . . . 5
4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. Next Steps . . . . . . . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8. Informative References . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Network Slicing enables creating end-to-end partitioned virtual
networks, including compute and storage resources, to deploy services
with diverse requirements over the same infrastructure.
[I-D.geng-coms-problem-statement] describes a problem statement for
supervised heterogeneous network slicing, enabling users to deploy
network slices including connectivity, computing and storage
components.
Nevertheless, defining and managing a network slice (NS) end-to-end
does not always have to be done directly: it may be convenient to
define and manage subsets of NS components. The concept of network
slice subnet is defined originally in [NGMN_Network_Slicing], though
we only need to retain its definition in the most general form:
network slice subnet instances are comprised of network, compute and
storage resources, but cannot be operated in isolation as a complete
network slice. They must be interconnected with other NS subnets to
form a complete, end-to-end network slice. To summarize: a NS subnet
can be seen as a network slice with unconnected links. The term
network slice segments has also occasionally been used to designate
NS subnets. Use cases for using NS subnets include managing multi-
domain network slices, or even within one domain, isolate management
and maintenance of different portions of a network slice.
A model for network slicing is currently being defined in
[I-D.qiang-coms-netslicing-information-model]. One question we would
like to address is how to augment this base model to describe
interconnections between NS subnets. The base model is not
technology specific, and therefore the description of
interconnections should not be either. Moreover, such an
augmentation should both enable describing the intent for
interconnection, as well as describing actual interconnections once
NS subnets have been stitched together.
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1.1. Terminology
Network slicing related terminology used in this document should be
interpreted as described in [I-D.geng-coms-problem-statement].
Note: in this text we refer to termination points, as defined in
[I-D.ietf-i2rs-yang-network-topo], while a similar concept is called
"port" in [I-D.qiang-coms-netslicing-information-model]. Terminology
will be adjusted as needed later on.
2. Interconnection Concepts
The general goal of an interconnection between 2 NS subnets is to
have links established between nodes from both subnets. A secondary
goal is to keep NS subnet descriptions isolated from each other (to
some extent that is still to be defined). This relative isolation
will contribute to simplify and decentralize management, as well as
enabling operations such as substituting a subnet with another, etc.
As described in Figure 1, we can represent a network slice subnet as
a network slice that also has one or more logical nodes, which
terminate (at logical termination points) links that need to be
interconnected with external nodes (cross-subnet links).
During a stitching operation, logical termination points from both NS
subnets can be paired together into an interconnection point. When
implemented at the infrastructure layer, this interconnection point
may be either implemented as a gateway, or abstracted away, in which
case nodes from both NS subnets end up being directly interconnected
between each other. In any cases, interconnected links will need to
have compatible QoS attributes.
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Slice Provider
|
+---------------------------------v---------------------------------+
| Slice Manager |
| |
| +---------------------------------------------------------------+ |
| | Data model: network slice composed of NS subnet 1 and 2 | |
| | | |
| | Network Slice Subnet 1 Network Slice Subnet 2 | |
| | +---------------------------+ +----------------------------+ | |
| | | cross-subnet link | | cross-subnet | | |
| | | +----------------+ | | link +------+ | | |
| | | | | | | +--------o node | | | |
| | | | |Interconnection| +---o--+ | | |
| | |+---o--+ +-------|-----+--+------|------+ | | | |
| | || node | | | | | | | | | | |
| | |+---o--+ | +-----|---+ | | +----|----+ | | | | |
| | | | | | | | | | | | | | | | | |
| | | | | | o - - - - - - - o | | | | | |
| | | | | | | | | | | | | | | |
| | | | | | logical | | | | logical | | | | | |
| | | | | | node | | | | node | | | | | |
| | | | | | | | | | | | +---+ | | |
| | | | | | o - - - - - - - o | | | | | |
| | | | | | | | | | | | | | | | | |
| | | | | +-----|---+ | | +----|----+ | +---o--+ | | |
| | | | | | | | | | | node | | | |
| | | | +-------|-----+--+------|------+ +---o--+ | | |
| | | | +------+ | | | | | | | |
| | | +-o node o-------+ | | +----------------+ | | |
| | | +------+ cross-subnet| | cross-subnet | | |
| | | link | | link | | |
| | +---------------------------+ +----------------------------+ | |
| +---------------------------------------------------------------+ |
+--------------------------------+----------------------------------+
|
v
Network Infrastructure
Figure 1: Network Slice Subnets Interconnection
Network slice interconnection information in data models can be used
for different related purposes:
o Anchoring interconnections at logical termination points: a NS
subnet model should specify which link termination points are the
"network slice subnet boundaries" that need to be interconnected.
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o Programming interconnections: a NS provider may set attributes in
a NS subnet model to configure the interconnection with another NS
subnet.
o Describing the state of interconnection (once NS subnets are
interconnected).
3. Information Model
A fairly minimal way to represent an interconnection is:
o To represent an interconnection anchor in a subnet: a logical
termination point in this subnet.
o To program or represent an interconnection between subnets: a pair
of logical termination points, one in each subnet.
Some form of grouping of logical termination points (for example, in
logical nodes) may tell the NS manager to treat those termination
points as a single unit for placement, implementation, etc.
Additional information may be useful to complement the description of
an interconnections. Some attributes may be useful to describe an
interconnection point anchor, while others may be useful to program
or represent the state of an interconnection. For example, logical
termination points may be associated with information that
facilitates placement or stitching operations. Future work should
determine what type of information would be useful to specify or
represent a NS interconnection.
4. Operations
Stitching may occur when network slice subnets are initially
instantiated, or later after instantiation.
5. Security Considerations
Access control mechanisms for managing network slices can likely be
reused for network slice subnets, since their models should be
similar to each other.
Stitching 2 NS subnets together may be subject to some form of
authorization by a NS tenant.
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6. Next Steps
The present draft investigates one aspect of a non-technology
specific representation of a network slice. It may therefore be part
of the larger discussion on the need for such a representation.
Beyond this, next steps can include the following:
o Discussing the definition and need for NS subnets. Is "NS with
unconnected links" an adequate simple definition? Is there an
agreement on the use cases? Should NS subnet interconnection be
standardized?
o Assuming there is some interest in this, further work is needed to
better understand what attributes and operations are needed, and
how to integrate them in a baseline NS model.
7. IANA Considerations
This document has no actions for IANA.
8. Informative References
[I-D.geng-coms-problem-statement]
67, 4., Slawomir, S., Qiang, L., Matsushima, S., Galis,
A., and L. Contreras, "Problem Statement of Supervised
Heterogeneous Network Slicing", draft-geng-coms-problem-
statement-00 (work in progress), September 2017.
[I-D.ietf-i2rs-yang-network-topo]
Clemm, A., Medved, J., Varga, R., Bahadur, N.,
Ananthakrishnan, H., and X. Liu, "A Data Model for Network
Topologies", draft-ietf-i2rs-yang-network-topo-16 (work in
progress), September 2017.
[I-D.qiang-coms-netslicing-information-model]
Qiang, L., Galis, A., 67, 4., kiran.makhijani@huawei.com,
k., Martinez-Julia, P., and H. Flinck, "Technology
Independent Information Model for Network Slicing", draft-
qiang-coms-netslicing-information-model-00 (work in
progress), September 2017.
[NGMN_Network_Slicing]
NGMN, "Description of Network Slicing Concept", 10 2016,
<https://www.ngmn.org/uploads/
media/161010_NGMN_Network_Slicing_framework_v1.0.8.pdf>.
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Authors' Addresses
Xavier de Foy
InterDigital Inc.
1000 Sherbrooke West
Montreal
Canada
Email: Xavier.Defoy@InterDigital.com
Akbar Rahman
InterDigital Inc.
1000 Sherbrooke West
Montreal
Canada
Email: Akbar.Rahman@InterDigital.com
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