Grass Valley iControl V.4.43 - Manual (Page 50)

Getting Started with iControl
Multicasting vs. Unicasting
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Multicasting vs. Unicasting
When a client application (e.g. iC Navigator) is opened, one of the first things it does is to
search for a lookup service that has a registry of devices and services available for monitoring
and/or control. There are two ways it can perform this search: multicast and unicast.
A multicast search is a general broadcast on a TCP/IP subnet—the applet is basically saying
“Are there any lookup servers out there?”. Any lookup servers on the same subnet will reply to
the multicast, making their registries available to the applet.
A unicast search is a request directed to a specific IP address. In this case, the applet is saying
“Attention server X, are you running a lookup service?”. If the answer is yes, the server will
make its registry available to the applet
By default, an iControl applet starts by performing a multicast search on its own subnet
(i.e. the subnet to which the client PC is connected), followed by a unicast search on the
Application Server from which it is launched. This behavior can be modified by editing the
lookup locations list on the Application Server, as shown in the following examples.
Figure 2-9: Example — Default Multicast/Unicast
Service And Alarm Discovery locations on 10.10.81.10
Connections made by iC Navigator opened from 10.10.81.10
No entry here means that applets
launched from this Application
Server will use default
multicast/unicast behavior
Default multicast finds four
Application Servers running
lookup services on the client
PC’s subnet
Default unicast finds lookup
service on the Application
Server from which iC Navigator
was opened
Bold text indicates a
connection to a lookup
service