5. Multicast > Overview
105
Tsi578 User Manual
June 6, 2016
Integrated Device Technology
www.idt.com
For systems that use multiple Tsi57x switches, the multicast engine (MCE) in each switch can be used
provided that multicast packets are not sent between the switches. This can be accomplished by having
the multicast source program the MCE in the switch it is directly connected to (see step 1 in
and then initiate an additional unicast transaction to the MCE in the other switch (see step 2).
Figure 21: Multicast Operation – Option 2
5.1.4
Multicast Terminology
The following table contains the terms used to describe the multicast functionality.
Table 12: Multicast Terminology
Term
Definition
Multicast Group
A multicast group is a set of ports that must all receive a copy of a packet. A system can
support multiple multicast groups, each of which is completely independent of the other (a
group can have all, some, or no ports in common with another group). A multicast group is
associated with a unique destinationID and TT of a packet.
Note: A packet is never multicast back out of the port that it is received on, regardless of
whether or not this port is included in the multicast group.
Multicast Mask
The set of egress ports in a multicast group.
Multicast Vector
The set of ports in a multicast group that will receive the multicast packets. The vector is
used to control which broadcast buffers are loaded with the packet to be multicast.
Original Packet
A single multicast packet that arrives at a switch and gets replicated and sent to multiple
egress ports according to the multicast mask.
Packet Copy
A copy of an original packet. The copies are sent out on the egress ports.
Multicast Traffic
Packets which are sent to the multicast engine from ingress ports, and packets which are
received from the multicast engine by egress ports.
Unicast Traffic
All packets which are not sent to or received from the multicast engine.
EP
Tsi57x
MCE
Tsi57x
Unicast
Packets
Multicast
Packets
Multicast
Packets
Multicast
Packets
Multicast
Packet
Source
Multicast
Packet
Source
Multicast
Packets
EP
EP
EP
EP
EP
MCE
EP
EP
1
1
2
2