Tacker & networking-sfc Integration


This specification describes an SFC driver for Tacker that will interface with the port-chain API of the Neutron networking-sfc project. The Tacker API provides for the management of Service VNFs and with [1], provides support for the creation of VNF Forwarding Graphs (VNFFG).

A VNFFG is a graph of VNFs logically connected, by which Network Forwarding Paths (NFPs) create paths through the graph. The port-chain API can be used to build one or more NFPs through the graph.

Problem description

Tacker VNFFG and Neutron networking-sfc operate on two different levels of abstraction. While Neutron networking-sfc constructs a service chain via stitching together a list of Neutron ports, and is generally service agnostic, Tacker VNFFG operates on service instance or even higher service type constructs (such as ‘load-balancer’, ‘firewall’…etc).

In order to be able to render the NFPs of a VNFFG, networking-sfc is required to provide the ability to create SFCs and Classifiers for Tacker.

Proposed changes

The new networking-sfc driver for Tacker will map from the high-level abstract description of a VNFFG to a Neutron port description of a VNFFG, namely a port-chain. The diagram below shows the networking-sfc driver integrated with the Tacker NFVO plugin and the Tacker VNF Manager (VNFM) plugin in the Tacker Server.

The NFVO extension has a dependency on the VNFM extension.

|              Client Application             |
            | Tacker VNFFG API    | Tacker VNFM API
|           v                     v           |
|  +-----------------+    +----------------+  |
|  |      Tacker     |    |    Tacker      |  |
|  |  NFVO Extension |<-->| VNFM Extension |  |
|  |   Plugin/DB     |    |   Plugin       |  |
|  +------------+----+    +----------------+  |
|               |                             |
|               v                             |
|         +==========================+        |
|         |     networking-sfc       |        |
|         |     Port Chain Driver    |        |
|         +==========================+        |
| Tacker Server        |                      |
                       | Port Chain API
| Neutron Server       v                      |
|            +-------------------+            |
|            | networking-sfc    |            |
|            | Port Chain Plugin |            |
|            +-------------------+            |

The NFVO plugin will pass the VNFFG CRUD operations to the networking-sfc driver. The driver will map the VNFFG CRUD operations to port-chain CRUD operations and call the port-chain API of the networking-sfc Port Chain plugin.

The NFVO plugin also interfaces with the Tacker VNFM to retrieve VNF instances and their ingress/egress interfaces in the case where the VNFFG is specified in terms of abstract VNF types.

The NFVO plugin sends a query to the VNFM with a filter that specifies the abstract VNF type and additional type-specific metadata. The VNFM may indicate that there is no matching VNF instance available to support the desired abstract VNF type specified in the query. The VNFM may return one or more VNF instances that are able to support the desired VNF type.

Although scaling is a future Tacker enhancement, VNF scaling is currently supported by networking-sfc. If the VNFM returns multiple VNF instances the NFVO plugin may select one VNF instance to create a port-pair-group with a single port-pair. When the NFVO plugin does support scaling, it may alternatively create a port-pair-group that includes all the VNF instances returned by the VNFM.

The networking-sfc driver will include the following functionality:

  • Map a VNFFG chain definition to a networking-sfc port-chain definition.

  • The driver will format port-chain CRUD operations and call the port-chain API.

  • If a VNFFG is specified as symmetrical, the driver will set ‘symmetric’ to true in the chain parameters atrribute.

  • Map the VNFFG classifier to a flow-classifier for the port chain. As the flow-classifier defined in Tacker VNFFG currently contains more matching fields — those that aren’t supported by networking-sfc would simply be resulting in unimplemented exception.

  • The default driver of Tacker VNFFG will be ‘networking-sfc’

The current Tacker NFVO workflow to stage and deploy a VNFFG is as follows

tacker vnffg-create --name myvnffg --vnfm_mapping VNF1:testVNF2,VNF2:testVNF1
                    --symmetrical True

networking-sfc follows the following workflow:

neutron port-pair-create --ingress <port-id> --egress <port-id>

neutron port-pair-group-create --port-pairs <port-pair-id>

neutron flow-classifier-create --protocol tcp --destination-port 80:80

neutron port-chain-create --port-pair-group <port-pair-group-id>
                          --flow-classifier <classifier-id> <name>

a port-chain can be created without flow-classifier, but the network plumbing would be configured after the port-chain-create command.

The mapping of Tacker VNFFG APIs to Neutron networking-sfc client calls:

|   Tacker VNFFG API          |   networking-sfc client CLI           |
|                             |                                       |
|       vnffg-create          |   neutron port-pair-create            |
|                             |       --ingress [Neutron port]        |
|                             |       --egress [Neutron port]         |
|                             |                                       |
|                             |   neutron port-pair-group-create      |
|                             |       --port-pairs [port pair id]     |
|                             |                                       |
|                             |   neutron flow-classifier-create      |
|                             |       [parameters]                    |
|                             |                                       |
|                             |   neutron port-chain-create           |
|                             |       --port-pair-group <id>          |
|                             |       --flow-classifier <fc-id>       |
|                             |                                       |



Data model impact


REST API impact


Security impact


Notifications impact


Other end user impact


Performance Impact


Other deployer impact

User would need to specify the backend driver for networking-sfc via Neutron config file. By default it will be OVS driver.

Developer impact




Work Items

  1. Add new driver ‘networking-sfc’ for Tacker NFVO extension.

    • Add mapping from VNFFG chain definition to port-chain.

    • Add mapping from VNFFG classifier to port-chain flow-classifier.

    • Add mapping from NFVO plugin to networking-sfc API.

  2. Add unit tests for all of the above.

  3. Integrate with networking-sfc port-chain.

  4. devstack config to include networking-sfc.



Unit tests and function tests will be added.

Documentation Impact



[1] https://github.com/openstack/tacker-specs/blob/master/specs/newton/tacker-vnffg.rst