The Express datapath of the X4-series adapter does not support multicast replication between queues. However, replication is possible between a single Express datapath queue and multiple Enterprise datapath queues.
By default, the Express datapath of the X4-series adapter uses a dedicated queue for each application. This means that:
- The first application to attach to a given multicast stream on the Express datapath
is the only one that can do so.
The Express datapath delivers the multicast stream to the dedicated queue for that application.
- All other applications must attach to the multicast stream on the Enterprise
datapath.
The Enterprise datapath delivers the multicast stream to these applications using hardware replication.
If you instead want multiple applications to receive the same multicast stream on the Express datapath, you must configure Onload to use SHared Readable User Buffers (SHRUB). The multicast stream is then routed to a single shared buffer. A SHRUB controller is used to co-ordinate the super-buffer allocations for each queue. This allows each shared queue to operate seamlessly, when individual applications which access this shared queue start or stop.