5. Multicast > Overview
106
Tsi578 User Manual
June 6, 2016
Integrated Device Technology
www.idt.com
5.1.5
Multicast Behavior Overview
The multicast operation involves the following blocks:
•
Multicast Engine
•
Multicast Group Table
•
Multicast Work Queue
•
Broadcast Buffer for each egress port
•
ISF ingress arbitration algorithms for the Multicast Port
•
ISF egress arbitration algorithms for each egress port
The operation of the Work Queue and Broadcast Buffer is described in this section. For more
information ingress/egress arbitration algorithms, refer to
“Input Queuing Model for the Multicast
,
“Input Queuing Model for the Broadcast Buffer” on page 100
Queuing Model for Multicast” on page 100
Multicast packets received by an ingress port are routed to the Multicast Engine port based on the
destination ID and transaction type (TT) field of the packet. A packet arriving at the Tsi578 is directed
to the Multicast Engine (MCE) by the
multicast group table
on the packet’s ingress port. The multicast
work queue selects a multicast group for the packet, again based on the packet’s destination ID and TT
field. If the ingress port for the multicast packet is a part of the multicast group, the port is removed
from the multicast vector.
Once the multicast vector has been computed, the Work Queue transmits the original packet to the
Broadcast Buffers associated with the ports in the vector. Transmission between the multicast work
queue and the Broadcast Buffers uses a dedicated ISF path that is separate from those used to route
unicast traffic. Once the packet copies have been completely received by all of the broadcast buffers in
the multicast vector, each broadcast buffer arbitrates with its associated egress ports to accept the
packet copy. The broadcast buffer begins to transmit the packet copy to the egress port’s buffer when
the egress port signals that it is able to accept a packet.
Packets can cut-through from the ingress port to the multicast work queue and from the multicast work
queue to the broadcast buffers. However, a complete packet copy must be received by a broadcast
buffer before it attempts to forward the packet copy to the egress port.
Multicast packets are forwarded to the egress ports exactly as they were received. That is, the source
and destination IDs are not altered by the Multicast engine. This means that the replicated packets
emerge from the egress port with the same destination ID as the original packets.
The routing of unicast packets to a system-wide unique device ID is supported in a multicast
application because endpoints are expected to support two or more device IDs in order to differentiate
unicast from multicast packets.
System designers must be aware of this characteristic of multicast packets because of the
necessity that multiple endpoints own the same device ID in order to be able to accept
multicast packets.
Содержание Tsi578
Страница 1: ...IDT Tsi578 Serial RapidIO Switch User Manual June 6 2016 Titl ...
Страница 20: ...About this Document 20 Tsi578 User Manual June 6 2016 Integrated Device Technology www idt com ...
Страница 102: ...4 Internal Switching Fabric Packet Queuing 102 Tsi578 User Manual June 6 2016 Integrated Device Technology www idt com ...
Страница 228: ...11 Signals Pinlist and Ballmap 228 Tsi578 User Manual June 6 2016 Integrated Device Technology www idt com ...
Страница 504: ...B Clocking P_CLK Programming 504 Tsi578 User Manual June 6 2016 Integrated Device Technology www idt com ...
Страница 526: ...Index 526 Tsi578 User Manual June 6 2016 Integrated Device Technology www idt com ...