Interconnecting (or Stitching) Network Slice Subnets
draft-defoy-coms-subnet-interconnection-01
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| Authors | Xavier de Foy , Akbar Rahman , Alex Galis , Kiran Makhijani , Li Qiang | ||
| Last updated | 2017-10-30 | ||
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draft-defoy-coms-subnet-interconnection-01
none X. de Foy
Internet-Draft A. Rahman
Intended status: Informational InterDigital Inc.
Expires: May 3, 2018 A. Galis
University College London
K. Makhijani
L. Qiang
Huawei Technologies
October 30, 2017
Interconnecting (or Stitching) Network Slice Subnets
draft-defoy-coms-subnet-interconnection-01
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 May 3, 2018.
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to this document. Code Components extracted from this document must
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Interconnection Concepts . . . . . . . . . . . . . . . . . . 3
3. Information Model . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Representing Interconnections . . . . . . . . . . . . . . 5
3.2. Relation to NS Information Model . . . . . . . . . . . . 5
4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. Next Steps . . . . . . . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. Informative References . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Network Slicing enables deployment and management of services with
diverse requirements on end-to-end partitioned virtual networks,
including compute and storage resources, 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 universal form:
network slice subnet instances are similar to slice instances in most
ways but cannot be operated in isolation as a complete network slice.
They can be interconnected with other NS subnets to form a complete,
end-to-end network slice (i.e. interconnection and/or stitching of NS
subnets). To summarize: a NS subnet can be seen as a network slice
with unconnected links. The term "network slice segment" has also
occasionally been used to designate a NS subnet. 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. It includes also mapping services to an
ordered chain of network slice subnets instances.
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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.
1.1. Terminology
Network slicing related terminology used in this document should be
interpreted as described in [I-D.geng-coms-problem-statement].
"Network slice subnet" is a term defined in this draft. It is
comprised of groups of connectivity, compute and storage resources,
possibly together with network functions and network management
entities, forming a complete instantiated logical/physical network in
support of certain network and service characteristics but cannot be
activated in isolation as an overall network slice.
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.
This relative isolation will contribute to simplify and decentralize
management, as well as enabling operations such as substituting a
subnet with another, composing slice subnets of different domains,
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. For example, constraints on the interconnection (on
throughput, latency, etc.) may be programmed to trigger an alarm
that may be lead the NS operator to disable NS subnets, replace NS
subnets by others, etc. to maintain overall service performance.
o Describing the state of interconnection (once NS subnets are
interconnected).
3. Information Model
3.1. Representing Interconnections
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.
3.2. Relation to NS Information Model
The network slice information model defined in
[I-D.qiang-coms-netslicing-information-model] will be used as a base.
This model is itself based on the "ietf-network" model defined in
[I-D.ietf-i2rs-yang-network-topo]
Individual network slice data model instances ("network" attributes
of the "ietf-network" model) can represent network slice subnets. If
there is a need to tie multiple subnets together, a parent network
slice may be added to the model if necessary, but this is out of
scope of the present draft. A "network" attribute may also represent
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a full, end-to-end slice, in which case it does not need be
interconnected using the mechanisms described in the present draft.
Interconnection anchors are logical termination points (TP) included
in logical nodes. The base model can be augmented as described
below. Those new logical node and logical TP attributes will
typically be used only for nodes and termination points used as
interconnection anchors. Logical nodes should be as simple as
possible (e.g. should not include any compute or storage unit), so
that they can be abstracted away in underlying networks during the
interconnection operation, if needed.
module: ietf-network
+--rw networks
+--rw network* [network-id]
+--rw network-id
+--rw network-types
+--rw supporting-network* [network-ref]
| +--rw network-ref
+--rw node* [node-id]
| +--... (augmented with new attributes of logical nodes)
| +--rw nt:termination-point* [tp-id]
| | ... (augmented with new attributes of logical TP)
...
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.
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:
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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.
o Additionally, we can also further study NS composition mechanisms,
beyond the simple connect/disconnect mechanism in the present
draft.
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-17 (work in
progress), October 2017.
[I-D.qiang-coms-netslicing-information-model]
Qiang, L., Galis, A., 67, 4., kiran.makhijani@huawei.com,
k., Martinez-Julia, P., Flinck, H., and X. Foy,
"Technology Independent Information Model for Network
Slicing", draft-qiang-coms-netslicing-information-model-01
(work in progress), October 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>.
Authors' Addresses
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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
Alex Galis
University College London
Email: a.galis@ucl.ac.uk
Kiran Makhijani
Huawei Technologies
2890 Central Expressway
Santa Clara CA 95050
USA
Email: kiran.makhijani@huawei.com
Li Qiang
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing 100095
Email: qiangli3@huawei.com
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