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ForwardingConstruct.md

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ForwardingDomain, ForwardingConstruct and ForwardingConstructPort

ForwardingDomain

The ForwardingDomain (FD) represents a potential for Forwarding.
Forwarding is typically supported on multiple layers inside networks and devices.
That's why the ControlConstruct class holds a list of ForwardingDomains.

A ForwardingDomain usually holds a list of references to interfaces between which connections of a certain layer could be configured, as well as a list of connections (ForrwardingConstruct) that belong to the same layer and are already configured.

In case of the applications of the MW SDN domain, a potential for Forwarding is only expressed on the Operation layer.
An explicit listing of references to all the OperationServers and OperationClients is not included.
Just a list of ForwardingConstructs is comprised.

The ForwardingDomain comprises the following attributes:

  • uuid: Identifier that is unique within the entire MW SDN application layer. Details can be found in Structure of UUIDs.
  • forwardingConstruct: List of connections that are configured within this ForwardingDomain.

ForwardingConstruct

The ForwardingConstruct (FC) represents the actually configured Forwarding.
It can be used to represent a wide range of forwarding behaviors, from simple packet forwarding to complex traffic engineering and policy-based routing.
Since multiple Forwardings can typically exist in parallel between the interfaces of the same logical layer, the ForwardingDomain contains a list of ForwardingConstruct.

In case of the applications of the MW SDN domain, the ForwardingConstruct describes an event-reaction-relationship on the Operation layer.
This means the relationship between receiving a request at a specific OperationServer (event) and sending requests through one or more OperationClients (reaction).

The ForwardingConstruct comprises the following attributes:

  • uuid: Identifier that is unique within the entire MW SDN application layer. Details can be found in Structure of UUIDs.
  • name: List of two instances of a composed datatype that holds a valueName and a value attribute. The name attribute is basically some backdoor for adding additional attributes to the ONF Core modelling.
  • name::valueName: Name of the attribute that shall be added to the modelling. The following entries shall be made into two separate instances 'ForwardingKind' and 'ForwardingName'.
  • name::value: Value of the attribute that shall be added to the modelling.
  • name::value if valueName==ForwardingKind: In this case, the value of the value attribute is to be chosen from:
    • core-model-1-4:FORWARDING_KIND_TYPE_INVARIANT_PROCESS_SNIPPET: Number of FcPorts is invariant.
    • core-model-1-4:FORWARDING_KIND_TYPE_SUBSCRIPTION: Number of FcPorts is variant, but they get all activated by every event.
    • core-model-1-4:FORWARDING_KIND_TYPE_PROCESS_SNIPPET: Number of FcPorts is invariant. A sophisticated logic implements the Forwarding based on case by case decisions. This might involve variable subsets of Outputs to be activated dependent on the characteristics of the individual event.
  • name::value if valueName==ForwardingName: Name of the forwarding as already defined in the ForwardingList.
  • fcPort: List of references to LogicalTerminationPoints that are part of the Forwarding.

ForwardingConstructPort

The ForwardingConstructPort (FcPort) describes the reference to an interface that is part of an actually configured Forwarding.
In principle, the interfaces could also have been referenced from within the ForwardingConstruct itself, but the ForwardingConstructPort as an intermediate element allows adding attributes to the reference.
This is of particular importance, if the interfaces that are belonging to the same Forwarding distinguish roles like e.g. ingress and egress.

In case of the applications of the MW SDN domain, ForwardingConstructPorts are exclusively referencing OperationServers and OperationClients.

The ForwardingConstructPort comprises the following attributes:

  • localId: Identifier that is unique just within the residing ForwardingConstruct.
  • portDirection: Role of the referenced OperationClient or OperationServer inside the Forwarding.
    • core-model-1-4:PORT_DIRECTION_TYPE_MANAGEMENT: FcPorts of this type are always referencing an OperationServer that influences the creation, deletion or modification of FcPorts of type Output inside the same ForwardingConstruct. A ForwardingConstruct may have zero to n Managements. A common case of managing a ForwardingConstruct comprises a specific OperationServer for subscribing to a kind of notifications and a generic OperationServer for unsubscribing.
    • core-model-1-4:PORT_DIRECTION_TYPE_INPUT: FcPorts of this type are always referencing an OperationServer. Receiving a request at such OperationServer leads to sending requests via one or several Outputs of the same ForwardingConstruct. A ForwardingConstruct may have one to n Inputs. In rare cases, Outputs get activated based on a cyclic process inside the application, but not an individual event at an Input. In such case, the OperationServer that servers as Management for starting the cyclic process shall be listed as an Input, too.
    • core-model-1-4:PORT_DIRECTION_TYPE_OUTPUT: FcPorts of this type are always referencing an OperationClient. A ForwardingConstruct may have one to n Outputs. Depending on the type of Forwarding, one or several Outputs get activated at a time.
  • logicalTerminationPoint: UUID of the referenced OperationClient or OperationServer.