Implementation note there is an open question of who

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Implementation Note: There is an open question of who is allowed to modify certain attributes in a slice RSpec : a user assigned to the slice, a administrator of the organization that approved the slice, or some operator working on behalf of PLC. Today, for each RSpec attribute, the SA database maintains a record of the privilege level required to change the associated value; some can be changed by the user and some by PLC operator. For each slice, the SA maintains a state field that indicates several key proper- ties of the slice. The state is a combination of several independent values, each recording an aspect of the slice’s current mode of use. The first bit indicates 17
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whether the creation of VMs for the slice has been delegated to another service, or should be performed by the slice authority’s agent on each node (corresponding to value central ). The second bit indicates whether the slice is currently started or stopped —a slice may be stopped by either associated users or by PLC, for exam- ple, it the slice behaves in a manner that has adverse effects. The third bit indicates whether a slice is active or has been deleted ; for auditing purposes we retain all slice records in the database even after they have been deleted by their users. We explain the two ways of instantiating a slice in the next subsection. There are two ways to instantiate a slice on a set of nodes: directly or via delegation . Before either can be invoked, however, a record for the slice must exist in the SA database, and an RSpec must be initialized for the slice. This involves multiple calls on the SA: CreateSlice(auth, slice name) SetSliceAttr(auth, slice name, attribute) AddSlicePrincipal(auth, slice name, principals[ ]) AddSliceNode(auth, slice name, nodes[ ]) The first creates the slice in the SA database, multiple calls to the second fills out the RSpec for the slice, and the third and fourth operations associate a set of users and nodes with the slice, respectively. For all four operations (as well as those that follow), auth contains authorization information for the call. (See Section 5 for a description of the underlying security architecture.) One a complete slice record exists in the SA database, the user can enable slice instantiation by invoking: StartSlice(auth, slice name) This operation sets the slice’s state = central in the database, which means that this slice will be included in the set of slices to be created on the appropriate nodes when the SA is queried by the slice creation service on one of those nodes. As de- scribed in Section 4.5, the slice creation service running on any nodes that trust this particular slice authority calls the SA periodically, and creates the corresponding set of slices if they do not already exist on the node.
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  • Spring '10
  • CS
  • IP address, slice, Slice Authority

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