[bogomipz]

I am having trouble understanding this passage. I'm wondering is someone could help me understand this as it seems like an important design detail:

>"Another benefit to using UDP is that the source port can be filled in with a per-connection hash so that they are flow within the datacenter over different paths (where ECMP is used within the datacenter), and received on different RX queues on the proxy server’s NIC (which similarly use a hash of TCP/IP header fields)."

A source port in the UDP header still needs to be be just that a port number no? Or are they actually stuffing a hash value in to that UDP header field? How would the receiving IP stack no how to understand a value other than a port number in that field?

[gbrayut]

Just a guess, but by using UDP transport for the encapsulated data and configuring the module on the proxy to accept UDP on a wide range of ports, you can pick any port you want (not just the destination port of the TCP stream in the encapsulated packet). And if you are using ECMP with a known hashing algorithm you can then use that UDP port to explicitly spread packets across the RX queues on the proxy servers (gaining better performance).

[bogomipz]

Thanks I think that might be what they mean - hash the source port for better distribution across the RX queues on the destination proxy. Cheers.