NCast N-Way Server - Manual (Page 31)

NCast N-Way Reference Manual
But, and here is the difficulty, the N-Way Client at “B” will place the packet onto the LAN with the source address
of Telepresenter “A” and send it out with a TTL of 1. At this point Telepresenter “A” receives the packet, and the
N-Way Client inside “A” determines that a multicast packet with a current group address and a source address of
the local machine has arrived, and therefore should be forwarded up the tunnel to the server. We have now
created a cyclic feedback loop from “A” to the Server to “B” and back to “A”, and the only thing limiting packet flow
will be the maximum bandwidth in the links connecting the Server to the LAN of the Telepresenters.
6.6.N-W
AY
R
ESTRICTION
– M
ULTIPLE
H
OPS FROM THE
LAN
A final comment concerns limitations of traffic flow outside the local LAN. Packets arriving at the Server are
multicast on the local LAN with the source address of the originating machine. Because of rules determining how
multicast distribution networks are set up, this implementation does not allow these packets to flow to a native
multicast network if the Server is situated on one. Only machines connected to the Server’s local LAN will be able
to receive these broadcasts. Consequently, to reinforce this point, the Server sets the TTL of the packet to 1 to
make sure that no forwarding of any type will happen.
The same situation applies to multicast packets arriving at the N-Way Client. These packets cannot be natively
multicast beyond the local LAN, and therefore the TTL is set to 1 as a reinforcement of this condition.
NCast Corporation Revision 1.3
Page 31