External Layer2 Connections (Stitching)

Chameleon provides support for sophisticated networking experiments by providing GENI-style stitching. This capability enables users to deploy networking experiments (layer 2 and layer 3) that span Chameleon and other facilities such as FABRIC. Users can create dedicated Chameleon networks directly connected to external facilities and configure custom subnets and routers for handling these external connections. This capability is essential to users interested in experimenting with wide-area networks in a controlled environment or lower-level wide-area protocols (e.g. BGP or other routing protocols) that are not typically configurable by experimenters.

Stitched Chameleon networks are connected to external facilities using one VLAN allocated from of a pool VLANs that are statically provisioned between Chameleon and the external facility. Users can allocate one of these VLANs by making a reservation using Blazar. Currently, externally stitched networks are created by Blazar when the reservation is started. There is a pool of VLANs (3300-3309) between the Chameleon CHI@UC racks to the FABRIC site at StarLight (Chicago). Connections between the TACC site and FABRIC are in development.

The remainder of this document describes how to stitch Chameleon experiments to external resources using FABRIC. In addition to creating the stitched networks, you will need to know how to configure subnets and routers on dynamic VLANs as described in the Isolated Network VLANs documentation.


Stitching to FABRIC with the Python API is shown this a Trovi Artifact

Configuring a Stitchable Network

Your first step will require creating a stitchable network. Unlike creating other networks on Chameleon, stitchable networks can only be created by first reserving a stitchable VLAN segment. Once you reserve a VLAN segment, your network will be created automatically. To reserve a segment on the appropriate external testbed make sure to include fabric as the stitch_provider in the resource_properties attribute. An example is provided below:

openstack reservation lease create --reservation \
resource_properties='["==","$stitch_provider","fabric"]' \
--start-date "2022-01-01 12:00" --end-date "2022-01-02 12:00" \

After your stitched VLAN network is created, you will be able to query for the network to get the specific VLAN that is used by your network. Openstack refers to the VLAN as the segmentation_id. The following command will display the VLAN.

openstack network show my-stitchable-network --format value -c provider:segmentation_id

At this point your Chameleon network is connected to a FABRIC facility port at layer 2. You can now create a FABRIC slice and specify the Chameleon segmentation_id to use. This is a layer 2 connection and you can configure higher-level protocols, such as IP, in any way you desire.

Connecting Stitchable Isolated Networks across Chameleon Sites

Coming soon! When FABRIC stitching is available at TACC, you will be able to directly connect your experiments that span UC and TACC Chameleon sites.