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Motivaton

Based on discussion between ONAP and O-RAN-SC there is a need to provide a common model to µServices with respect to (network) topologies.

In previous proof-of concept and demonstrations several different topologies of different types were presented. Such use-case driven topologies have several "things" in common.  For multi topology networks based on virtual and physical network functions a view across technologies is required to optimize the network in terms of utilization and/or latency and other criteria's. 


Use case driven topology representations

Geographical Topology

Physical Topology

Ethernet Topology

PTP-Topology


Idea

The idea could be to define an ONAP topology model across all ONAP components and technologies and describe a kind of mapping to technology and/or use case specific topology models, such as:

  • PCEP
  • LLDP
  • IEEE 802.3
  • TAPI
  • OpenROADM
  • 3GPP-EP
  • IETF-Interfaces
  • ONF:LogicalTerminationPoints
  • OpenConfig
  • kubernetes (O-RAN O2?)
  • Cluster?
  • ...


Initial draft proposal


Principals and Terminology

Principals

Topology (both concept and service) is not:

  • The summation of all network configuration
  • A collection of inventory assets
  • Directly responsible for the provisioning/execution of changes in the network (It is not the part of the system that orders changes in the network)

Topology (both concept and service) is:

  • a representation of the arrangements (relationships, associations, etc.) among important entities
  • provides information that is shared in the context of an ONAP system by multiple to multiple applications, components, services
  • multi-domain: e.g.: technology and telecom domains (Optical, wireless;); management; organizational – a logical partitioning of important entities
  • multi-layer: Services (potentially recursive) using telecom resources using infrastructure resources – expressing client-server relationships
  • multi-vendor: Important entities may be provided by different vendors, the topology is agnostic to the vendor
  • multi-operator: Special case of multi-domain, brought out to cover shared telecom networks
  • dynamically extensible (@runtime) w.r.t views, topology entities and their relationships

Abstract properties (concepts):

  • Connectivity: to represent the arrangements among endpoint of important entities (networking objects) across a topological domain e.g. to allow traffic flow for control and data / user plane
  • Containment/Composition: to represent the way networking resources (physical, virtual, logical) are instantiated, deployed and organized/structured in the network TODO example
  • Topology Types: E.g.: (Services, Resources, Network (E.g.: Transport; RAN; Packet core; NFV Topology; ...); ...)
  • Grouping: E.g: Geographical area; vendor; ORD;

Abstract needs (how does the ATM cater for...):

  • Responsible manager/software service/Ownership: to represent the relationship with the software owners of a particular network asset (physical or virtual) for a given perspective

Abstract needs:

  • Topology variationsTopology variations/Types: Must enable the development of these variations. E.g.: Services, Resources, Network (E.g.: Transport; RAN; Packet core; NFV Topology; ...); ...
  • Grouping: to represent the way topology elements can be grouped in a topology E.g: Geographical area; vendor; ORD; ... 
  • State: topology entity states and their transitions. E.g. LCM (Feasible; Designed; provisioned)
  • Labels: Any meta-data or information that a client may wish to associate with a topology entity
  • Identity: Every important entity must be uniquely identifiable, and may have multiple identities.

Configuration <==> Topology (!GraphGraph) <==> Inventory

  • Topology is derived from inventory (subset of equipment and assets) and configuration (subset of network configuration)
  • Some limited replication of data as needed to provide valueInventory and configuration are data mastersvalue – This is needed to simply construct and maintain the topologies for the abstract needs above
  • Inventory (A&AI) and configuration (CPS) are data sources. Topology normally derived/updated based on master source state. (Normally does not consider planning/intent)

We should not re-invent the wheel! Beg, borrow, reuse, apply and extend where necessary.

Visualization

It is assumed that every topology model could be visualized. The visualization is basically a case-by-case mapping of topology-nodes and topology-edges and their properties to shapes, lines, sizes, widths and colors. Therefore the topology model itself must not take the requirements for visualization into account. In some cases a kind of profile of stylesheet could describe such mapping, but it would be outside of the topology itself.


Terms and Definitions

This chapter specifies the terms used for an abstract topology model.

Term
Topology
Node
Edge
Group
Domain
Association
Link
Point
Inventory
Network
Physical
Virtual
more....


Use cases

Network Slicing

  • Transport to RAN - RAN to Transport - RAN to Core , ....

Alarm Correlation

Multi Domain Concepts

Multi Layer

O-RU recovery (from O-RAN-SC)

The O-RAN SC (Software community) defined a closed loop use case. A trigger (Fault-Notification) by O-RU is send to SMO (ONAP components are used to build the SMO layer). A µService should listen to this trigger and will perform an configuration on the corresponding O-DU.

Please see further details of the use case description:

The µService needs to know the connectivity between O-DUs and O-RUs for layer "Management Plane" to send the right configuration to the the right O-DU and with the right identification of the O-RU on O-DU level. Here a complete topology of the RAN connections on ONAP level could support such use case. The use case can be easyl enhanced by adding active and passive transport components between O-RU and O-DUs.

Requirements

  1. Resource topology – Abstract Topology shall support the creation of a topology of network resources (VNF, VIM, NF, MF, etc.)
  2. Network topology – Abstract Topology shall support the creation of a topology of how resources are connected
  3. Service topology – Abstract Topology shall support the creation of a topology that represents how services use Network and Resource topologies
  4. Geographical location information aware
  5. Layering of topologies – client, server representation
  6. State model (optional, for selected topology entities)
  7. Allocation (usage, e.g. bandwidth allocation)
  8. Logical grouping (ORD)
  9. Technology grouping
  10. Dynamic
  11. Cater for unmanaged assets
  12. Ownership – Abstract Topology shall support association of a topology entity to the software that owns it for a given purpose (e.g.: LCM; Configuration)
  13. Labels, meta-data

Impact on ONAP components

Candidates:

  • AAI
  • CPS
  • SDC
  • CCSDK
  • DCAE