Hello, I have been examing some of the topologies of the IDC network at Internet2 and others more closely and I have encountered some things that we may want to look at. One of the things that I would not know how to describe exactly in NML is the following example: A domain has a port on one of its devices. This port has an inter-domain connection. Through this port there are two possible connections to other domains, by means of separate VLAN labels. For example VLANs 1000-2000 go to one domain and 3000-4000 go to another. There are different ways of solving this at the moment. You do have to describe this somewhere as a single port, because of the limitations on the capacity of this port. I came up with three possible solutions, all with their own disadvantages: - Describe a single port with two links attached to it. This means breaks the assumption that a port can have at most one bi-directional link attached to it. - Describe a single port with two virtual ports each with its separate link. This breaks the assumption that a port is always connected by a Link (either a cross-connect or an external link), and we introduce a new concept of a virtual port. Are there other cases that would warrant this introduction? - Describe a single port that is connected to a "virtual" node where the connection is split into two. This makes the description more complex, and also seems to allow a direct connection between the two inter-domain connections without using the original port. Any other ideas? Jeroen.