Bionic Buffalo Tech Note #104: Summary of Pegasus/ISA versus DSM-CC Specification Coverage
Platform. DSM-CC doesn't specify any particular platform. Pegasus expects certain characteristics in
the client hardware and software.
Protocols. At the transport and presentation layer, DSM-CC defines several protocols, and defines
specializations on several others. DSM-CC is agnostic with regard to the network layer and beneath.
Pegasus specifies lower layer protocols, the specialization of a DSM-CC protocol (User-Network
Session), and creates a new protocol (LSCP) for controlling video-on-demand playback.
Interfaces and APIs. DSM-CC specifies the same API for the client and server, based on the
CORBA mapping of the IDL. Pegasus has one API for the client (based on the PowerTV
and another for the server (based on the CORBA IDL mapping). Although some of the interfaces have
the same names, there is not a single interface definition in common between Pegasus and DSM-CC.
Level of Abstraction. At the level of fudamental services (stream control, file access, and so on),
DSM-CC has a complete abstraction layer, where Pegasus is does not. At the higher application level,
DSM-CC is silent while Pegasus specifies several services (billing, asset management, and so on).
Motivation and Goals. One of the main goals of DSM-CC is to foster interoperability among a wide
variety of software components from diverse sources. Pegasus has a more specific purpose: to foster
interoperability among the products of suppliers to Time Warner.
Overlap and Separation
Instead of viewing Pegasus as “DSM-CC compliant”, or looking at the two architectures as having a
great deal in common, it is clear that they are largely disjoint. If we view the subject matter of the
architectures' definitions in the following way, the dissimilarity is clear. Consider the sets of
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