As revised 2006.05.04
Bionic Buffalo Tech Note #55
8. GIOP RPC (“UserUser”) Protocol
CORBA defines the general interORB protocol (GIOP) for use among ORBs. Within the messages,
certain fields are userextensible. DSMCC uses these extensible fields to define a dialect of GIOP. The
fundamental structure of GIOP is not altered. DSMCC IIOP retains the same message syntax as
CORBA GIOP, with additional semantics. The protocol state machines for DSMCC GIOP and CORBA
GIOP are the same.
A standard CORBA ORB which supports the portable interceptor (PI) interface can support DSMCC
GIOP if the application includes handlers for the necessary extensions.
The DSMCC specification does not in fact describe how GIOP works: it describes only the extensions
for DSMCC. For that reason, and also because GIOP is well described elsewhere, this discussion will
omit a detailed description of GIOP. Instead, this discussion will focus on the primary extensions
defined for GIOP by DSMCC.
A critical element of GIOP is the interoperable object reference, or IOR. An IOR is used to identify an
object uniquely, at the same time providing information necessary to locate the object. The information
needed to use a given protocol to access the object is contained within a profile, within the IOR.
In a simple network, there might be one profile within an object's IOR. For example, the IOR for an
object in a simple internet application might include the IP address, port number, and a unique
identifying key to distinguish the object from other objects at the same port and address.
In a more complex system, there might be more than one way to access the same object. For instance, in
a DSMCC environment, the object might be accessible through the internet, by way of an MPEG
stream, and also on a carousel broadcast on some channel. In the case of a
which encapsulates video or audio content, the content itself might be accessed using a high speed
MPEG stream, while playback control (pause, play, rewind, and so on) might best be done using a lower
speed IP connection. Multiple protocols can share a profile, or there might be one profile for each
protocol. (A single protocol is not permitted to use more than one profile.)
In addition to the basic addressing information, each profile might contain additional information used
to access the object. Known as components, these extra profile data provide protocol parameters;
security, transaction processing, and routing mechanisms, policies, and parameters; and other useful
DSMCC defines a structure
which contains connection information for various types of
connection. An instance of
contains four members:
the tap identifier, which is used to identify or number the tap
the tap use, which says how the connection is employed (such as MPEG transport downstream,
Copyright 2006 Bionic Buffalo. All rights reserved.
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