“Slice description” refers to the need of describing the tesbed slices, so that researchers can run experiments over them. A slice is not only characterized by the resources it is composed of, but also by the connection between them and link characteristics. It is essential for the CONFINE testbed that the slice description mechanism considers the following parameters:
There are several factors that influence which are the details (about the slice) needed to be present when describing it:
To conclude, the main points to evaluate the different solutions seem to be:
There are several information models that could be used as mechanism to represent the CONFINE slices. The ones considered most relevant are discussed below.
The Common Information Model (CIM) is an open standard for representing managed elements on an IT environment and the relationships between them. The CIM schema is split in several areas, among which the ones more relevant for the “Slice Description” requirement are:
CIM is a very complete schema, which considers almost anything imaginable on the IT subject, however, it goes too much on the detail, making it a hard to use schema. For instance the representation of a DiskDrive is the following:
Network Description Language (NDL) is a network description schema being developed by the University Van Amsterdam. NDL goal is to model the network as functional elements based on ITU-T G.805 and describe them afterwards in a compact syntax. NDL is divided in six schemas (1) Topology, (2) Layer, (3) Capability, (4) Domain, (5) Physical and (6) Technology. Among them, the ones relevant for the Slice Description requirement are:
To summarize, NDL is a simpler schema than CIM and the connectivity between components can be described in a easier way, however it is too much focused on network, without taking into account the IT components as storage or computing power, as we require.
Virtual private eXecution infrastructure Description Language (VXDL) is a language that allows the description of a Virtual Private eXecution Infrastructure (ViPXi), which is a time-limited aggregation of computing and communication resources. VXDL main component is the VirtualInfrastructure (VI), which is similar to the Slice concept in our project. A VI consist on a set of virtual resources, its topology and a timeline which defines the period of time the VI is valid. VXDL covers most of our requirements regarding the slice description and it is simpler than CIM. Some of its componets will have no use in the slice description though (like the route or routingTable concepts). What is missing in this model is on the description of the vNode, a mean of describing its Operative System and which layers can be accessed.
PlanetLab RSpec is used to allocate virtual machines to slices. The PlanetLab RSpec describes a request as a list of slivers already allocated on a physical node. As a list of slivers it does not take into account the topology among the nodes selected, but the cpu_share, disk_max and net_max_rate values can be set for each sliver. Details about the operative system cannot be set though.
VINI RSpec extends PlanetLab's by adding network information support, therefore links and virtual links (vlinks) can be defined between sites and nodes. A virtual link is defined by its endpoints between involved nodes and optionally by its bandwidth in kbps.
The more appropriate solution seems to be opting either the VINI Rspec or VXDL, since they are the information models more aligned with our requirements for the slice description, and opposed to CIM, their complexity is reasonable and can be tackled. However, since they do not contain all the necessary elements, they should be expanded as needed.