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Bionic Buffalo Tech Note #104: Summary of Pegasus/ISA versus DSM-CC Specification Coverage
Bionic Buffalo Tech Note #104
Summary of Pegasus/ISA versus DSM-CC Specification Coverage
last revised Thursday 2003.04.17
©2003 Bionic Buffalo Corporation. All Rights Reserved.
Tatanka and TOAD are trademarks of Bionic Buffalo Corporation
Pegasus and ISA are Not DSM-CC
There is a misconception among some that the Time-Warner Pegasus architecture, which includes the
Pegasus Interactive Services Architecture (ISA), is a form of DSM-CC. In fact, although there is some
overlap and there are a few similarities, the two specifications are quite different. In fact, for the most
part, they don't even cover the same problem space. The problem is compounded by their use in some
instances of the same names for different things.
What is DSM-CC?
DSM-CC, or Digital Storage Media Command and Control, is one of the MPEG-2 family of
specifications. Formally designated as ISO/IEC 13818-6, the DSM-CC specification is owned by the
International Organization for Standardization (ISO) and the International Electrotechnical Commision
(IEC). (The other MPEG-2 specifications are designated 13818-1, 13818-2, and so on. DSM-CC is part
6 of 10 parts.)
Revision 1 of the draft specification is dated November 1995.
In its own words, DSM-CC “consists of a modular set of protocols that may be combined or used
individually to provide a wide range of functionality which may be used to support emerging
mulitmedia technologies... The concepts and protocols of DSM-CC provide the general capability to
browse, select, download, and control a variety of bit stream types. DSM-CC also provides a
mechanism to manage network and application resources...”. There is also an abstraction layer, so that
“a suite of uniform interfaces are visible to the application, shielding it from the details of inter-
working among heterogeneous networks... a server may simultaneously and uniformly interact through
a single network interface with clients connected to different network types, without requiring a
separate network interface to each client.” (Quoted from the Introduction of the DSM-CC
In other words, DSM-CC is a set of protocols and interfaces (APIs), and is equally focused on servers
and on clients.
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