docs/docs_E2E_network_slicing.rst

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.. _docs_E2E_network_slicing:


E2E Network Slicing Use Case
============================

Overall Blueprint
-----------------
The objective of this use case is to realize **End-to-End 5G Network
Slicing** using ONAP. An End-to-End Network Slice consists of RAN (Radio
Access Network), Transport Network (TN) and Core Network (CN) slice
sub-nets. This use case intends to demonstrate the modeling,
orchestration (life cycle and resources) and assurance of a network
slice which are implemented in alignment with relevant standards. The
key highlights of this use case include:

-  Modular architecture providing building blocks and flexibility under
   various deployment scenarios

-  Functionality aligned with 3GPP and other relevant standards such as
   ETSI and IETF

-  Interfaces and APIs aligned with relevant standards (3GPP, IETF,
   ETSI, TM Forum, etc.) while enabling easy customization through use
   of appropriate plug-ins. This would enable easier interoperability of
   slice management functions realized within ONAP with 3\ :sup:`rd`
   party slice management functions, as well as northbound and
   southbound systems.

-  Taking a step-by-step approach to realizing different architectural
   options in an extendable manner.

-  Providing flexibility in network slice selection by providing an
   option of manual intervention, as well as abstracting the network
   internals as needed.

-  The use case implementation team is composed of service providers,
   software and hardware vendors, solution providers and system
   integrators thereby taking into consideration different perspectives
   and requirements.

This use case is a multi-release effort in ONAP with the first steps
taken in Frankfurt release. It will continue to expand in scope both in
breadth and depth, and along the journey it shall also align with
updates to the relevant standards which are also currently evolving.
This use case shall also collaborate with SDOs such as
O-RAN and ETSI to enable wider adoption and use.

See the `Use Case Description and Blueprint wiki page <https://wiki.onap.org/display/DW/Use+Case+Description+and+Blueprint>`_


Abbreviations
-------------

+---------------+--------------------------------------------+
|  Abbreviation |                   Meaning                  |
+===============+============================================+
| CSMF          | Communication Service Management Function  |
+---------------+--------------------------------------------+
| CSI           | Communication Service Instance             |
+---------------+--------------------------------------------+
| CST           | Communication Service Template             |
+---------------+--------------------------------------------+
| NSI           | Network Slice Instance                     |
+---------------+--------------------------------------------+
| NSMF          | Network Slice Management Function          |
+---------------+--------------------------------------------+
| NSSI          | Network Slice Sub-net Instance             |
+---------------+--------------------------------------------+
| NSSMF         | Network Slice Sub-net Management Function  |
+---------------+--------------------------------------------+
| NST           | Network Slice Template                     |
+---------------+--------------------------------------------+
| NSST          | Network Slice Sub-net Template             |
+---------------+--------------------------------------------+


Recap of Frankfurt functionality
--------------------------------
In Frankfurt release, CSMF and NSMF within ONAP was implemented, while connecting to an external Core NSSMF.
From the NSI Life Cycle perspective, the scope for Frankfurt included NSI design and pre-provision, NSI instantiation
and configuration, and NSI activation and deactivation. In particular:

- CSMF: Functions of slice service creation, slice service activation and deactivation were implemented.

- NSMF: Functions of NSI instantiation, NSI activation and deactivation were implemented. In addition, manual
  intervention is also provided in NSMF slice task management portal to ensure the selected NSI/NSSI as well as
  Service Profile and Slice Profile are OK or need adjustment.

- Design of CST, NST and onboarding NSST that are required to support the run-time orchestration functions

- To connect to the external (core) NSSMF, an adaptor was implemented to provide interface between ONAP and 3rd party
  core NSSMF.

To support the above functions, code impacts in U-UI, SO, OOF and ExtAPI components, and schema change in A&AI
were implemented. See the `Proposed Functions for R6 and Impacted Modules wiki page <https://wiki.onap.org/display/DW/Proposed+Functions+for+R6+and+Impacted+Modules>`_ for details.

As part of Frankfurt release work, we supported the minimum-scope installation of ONAP to reduce the resource requirements.
From the module perspective, 5G E2E Slicing use case involves SDC, SO, A&AI, UUI, EXT-API, OOF and Policy modules of ONAP.
So we will configure these required modules along with the mandatory common modules such as DMaaP. Further, for each module,
the use case also does not use all of the charts，so we removed the not needed Charts under those modules to optimize the
resources required for setting up the use case. This approach will help to install a minimum-scope version ONAP for the
E2E Slicing use case.

Further details of the installation steps are available at: `Install Minimum Scope ONAP for 5G Network Slicing wiki page
<https://wiki.onap.org/display/DW/Install+Minimum+Scope+ONAP+for+5G+Network+Slicing>`_

Recap of Guilin functionality
-----------------------------
From the architecture point of view, in Guilin release, besides the continuation of NSMF which was implemented in
Frankfurt release, the RAN NSSMF, TN NSSMF, CORE NSSMF have been implemented within ONAP, apart from interacting with
ezternal RAN NSSMF and external CORE NSSMF.

The following provides an overview of the enhancements done in Guilin release:

- **Enhancements in NSMF**: Service Profile decomposition into Slice Profiles for 3 domains, NSI selection enhancement,
  E2E slice instance creation including RAN, TN and CN slice sub-net instance creation/reuse, activation/deactivation
  of E2E slice, and deciding whether to terminate E2E slice or not.

- **RAN NSSMF, TN NSSMF, CN NSSMF within ONAP**: Basic logic for all 3 NSSMFs to support NSSI allocation, activation,
  deactivation, deletion and modification (in case of reuse of NSSI).

- **Enable NSMF interaction with RAN NSSMF, TN NSSMF, CN NSSMF**: Implement generic NSSMF adaptor for three domain NSSMFs,
  alignment with standard intefaces (3GPP, IETF), enable the connection to external RAN NSSMF.

- **Design of RAN NSST, TN NSST, CN NSST and Slice Profiles, TN information models**: Basic E2E Slicing model was provided
  all the related templates designed from SDC, TN related information models.

- **TMF 641 support**: Extension of the TMF 641 based interface from NB of ExtAPI to support service activation,
  deactivation and termination.

- **RAN and CN NFs set up and initial configurations**: CN NF simulators was developed: AMF, SMF, UPF and configure the
  S-NSSAI on CN NFs; RAN NF Simulator was enhanced for PM data reporting, CU and Near-RT RIC configuration.

- **KPI monitoring**: Implementation to request details of a KPI via UUI to ONAP DCAE. Providing the requested data to UUI
  by DCAE using a new microservice (Data Exposure Service - DES). Enhancements in PM-Mapper to do KPI computation is
  in progress, and will be completed in Honolulu release.

- **Closed Loop**: First steps to realizing a simple Closed Loop in the RAN using PM data collected from the RAN was
  implemented - update the allowed throughput for a S-NSSAI per Near-RT RIC coverage area based on DL/UL PRB for data
  traffic that was reported from the RAN. The analysis of the PM data was done using a new Slice Analysis MS in DCAE,
  and the Policy-based Control Loop framework was applied to trigger the updates in the RAN.

- **Intelligent Slicing**: First steps to realizing a simple ML-based Closed Loop action in the RAN using PM data collected
  from the RAN was implemented - update the maxNumberofConns for a S-NSSAI in each cell based on PDU session related
  PM data that was reported from the RAN (PDU sessions requested, successfully setup and failed to be set up). The
  training was done offline, and the ML model is onboarded as a micro-service to ONAP for demo purpose alone (it is
  not part of ONAP code/repos). The ML model provides updates to the Slice Analysis MS, which then uses the
  Policy-based Control Loop framework to trigger the updates in the RAN.

- **Modeling enhancements**: Necessary modeling enhancements to support all the above functionalities.

The base use case page for Guilin release is `E2E Network Slicing Use Case in R7 Guilin <https://wiki.onap.org/display/DW/E2E+Network+Slicing+Use+Case+in+R7+Guilin>`_.

The child wiki pages of the above page contains details of the assumptions, flows and other relevant details.

Honolulu release updates
------------------------
In Honolulu release, the following aspects were realized: 

- **Modeling Enhancements** were made, details can be found at:
  `Modeling enhancements in Honolulu <https://wiki.onap.org/display/DW/Modeling+enhancements+in+Honolulu>`_.

- **Functional Enhancements**

  (a) Minor enhancements in NSMF and NSSMFs including NST Selection, Shared slices, coverageArea to
      coverageAreaTAList mapping, etc.
  (b) Enhancements related to endpoints for stitching together an end-to-end network slice
  (c) Use of CPS (instead of Config DB) to determine the list of Tracking Areas corresponding to a given
      Coverage Area (input by user). For the remaining RAN configuration data, we continue to use Config DB.
  (d) RRM Policy update by SDN-R to RAN NFs during RAN NSSI creation/reuse

- **Integration Testing**
  Continuing with integration tests deferred in Guilin release, and associated bug-fixing

Important Remarks
~~~~~~~~~~~~~~~~~
(a) 2 deployment scenarios for RAN NSSI are supported. In the first scenario, the RAN NSSI comprises also of
    TN Fronthaul (FH) and TN Midhaul (FH) NSSIs, and RAN NSSMF shall trigger TN NSSMF for TN FH and MH NSSI
    related actions. In the second scenario, the RAN NSSI comprises only of RAN NFs. TN NSSMF shall be triggered by
    NSMF for TN FH and MH NSSI related actions. This part is not yet implemented in NSMF within ONAP.

(b) Details of the modeling aspects, flows and other relevant info about the use case are available in:
    `R8 E2E Network Slicing Use Case <https://wiki.onap.org/display/DW/R8+E2E+Network+Slicing+use+case>`_ and its child wiki pages.


Impacted Modules for Honolulu
-----------------------------
The code-impacted modules of E2E Network Slicing in Honolulu release are:

- **UUI**: The enhancements done include:

  (a) The coverageArea The coverageArea number param is added in CSMF creation UI. Users could input
      the grid numbers to specify the area where they want the slicing service to cover.
  (b) The relation link image of AN/TN/CN has been added. Users can see the links and related params
      of the three domains.
  (c) The TN’s connection link with AN/CN has been added in NS Task management GUI.

- **AAI**: Schema changes were introduced. We added some new parameters in 2 nodes:

  (a) ‘Connectivity’ is used to store IETF/ACTN ETH service parameters. New attributes added in order
      to support the CCVPN network configuration operations on multi-domain (2+) interconnections.
  (b) ‘Vpn-binding’is used to store ACTN OTN Tunnel model’s parameters.

- **OOF**: Updates include:
  
  (a) NST selection is enhanced by fetching the templates from SDC directly.
  (b) coverageArea to coverageAreaTAList mapping is done by OOF (as part of Slice Profile generation)
      by accessing CPS.
  (c) Bug-fixes

- **SO**: Main updates include support of NSI shared scenarios by enhancing the interaction with OOF, AAI and
  UUI. Apart from this some updates/fixes have been made in NSMF, RAN/Core/TN NSSMF functionality in SO, for
  example:

  (a) *NSMF*: Update NSI selection process support shared NSI and add sst parameter
  (b) *AN NSSMF*: Activation flow for SDN-R interactions, allocate flow & added timeDelay in QueryJobStatus,
      support of Option 1 for topmost RAN NSSI
  (c) *CN NSSMF*: Non-shared allocate flow
  (d) *TN NSSMF*: Modify TN NSSI operation

- **CPS**: 2 APIs required for the use case are supported. The remaining yang models are also onboarded,
  however, the API work as well as further enhancements to CPS Core, NF Proxy and Template-Based Data
  Model Transformer Service shall continue beyond Honolulu.

- **SDN-R**: RRMP Policy updates, enhancements for updating the RAN configuration during slice reuse,
  closed loop and intelligent slicing.

- **DCAE**:

  (a) *KPI Computation MS*: This MS was introduced newly for computation of slice related KPIs. In this release,
      it supports basic KPI computation based on formula specified via Policy. Further details about this MS is
      available at `KPI Computation MS <https://wiki.onap.org/display/DW/DCAE+R8+KPI-Computation+ms>`_
  (b) *Slice Analysis MS*: Minor updates were done.

Apart from the above, Policy and SDC had test-only impact for this use case.

In addition:

- **Config DB** was updated to handle bugs and gaps found during testing. This is not an official ONAP component, and
  its functionality is expected to be performed fully by the Configuration Persistence Service (CPS) in future ONAP
  release (beyond Honolulu).

- **Core NF simulator** and *ACTN simulator* were also updated and checked into ONAP simulator repo.

- **RAN-Sim** has been updated to fix bugs found during testing, and also checked into ONAP simulator repo.


Functional Test Cases
---------------------
The functional testing of this use case shall cover CSMF/NSMF, the 3 NSSMFs and Closed Loop functionality. We classify the
test cases into 5 tracks: CSMF/NSMF, RAN NSSMF, Core NSSMF, TN NSSMF and Closed Loop.
Details of the test cases can be found at:
`Integration Test details for Honolulu <https://wiki.onap.org/display/DW/Integration+Test+details+for+Honolulu>`_ and its child wiki pages.


Operation Guidance
------------------
The Honolulu release setup details for the E2E Network Slicing use case will be available at the following page and its
sub-pages:
`User Operation Guide for Honolulu release <https://wiki.onap.org/display/DW/User+Operation+Guide+for+Honolulu+release>`_


Known Issues and Resolutions
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Details of manual configurations, work-arounds and known issues will be documented in the child wiki pages of:
`User Operation Guide for Honolulu release <https://wiki.onap.org/display/DW/User+Operation+Guide+for+Honolulu+release>`_