Is it possible to prepare RoCE setup using Cisco catalyst 4506 or 3Com 3870 switch and servers with Mellanox ConnectX-5 NIC.
Please refer to the below article:
https://community.mellanox.com/docs/DOC-3062 Cisco switches. To enable ECN and PFC
https://community.mellanox.com/docs/DOC-2855 The main page to configure the ROCE end to end.
Please refer to the NIC part, and combine the Cisco switch config, then you would have a way to do achieve it.