My math shows a necessary rate of about 79.4 Mbps, just for the data. You'll also need to account for both packet and framing overhead. Without knowing the typical packet's MTU, unable to calculate overhead but if the packet MTU is typical full size Ethernet (1500), you should be able to fit within 100 Mbps assuming you're not also sending other data across the same links concurrently.
I'm unfamilar with Omnicast, but from what I read, it appears to use its own protocol, MFTP, on top of UDP. It also appears it might offer a send rate specification and MTU size to use. Likely you'll want to use the largest MTU supported by your network. As to transmission speed, you'll need to find out whether the application clocks at data rate or physical rate. If the former, setting a data rate for 80 Mbps might be okay. Faster also might be okay if the server's sending interface is set for 100 Mbps.
Something to verify, is whether real multicast is being used. Again, from what I've been reading the application seems to support real multicast, but it might also support a pseudo-multicast, the latter where it sends to multiple receivers concurrently using unicast. Also insure your MPLS vendor accepts true multicast. Some now do but as an extra cost option.
