On 28 May 2016 at 10:31, Adam Vitkovsky <[email protected]> wrote: > Alright then so indeed nodes participating in echo mode have to do more work > as nodes participating in non-echo mode. That's why assume it performs slower > (comparing performance of both modes in SW). > > To do list of one of the nodes in non-echo mode: > Tx at a given rate. > Reset dead timer if hello from remote node received. > > To do list of one of the nodes in non-echo mode: > Tx at a given rate. > Reset dead timer if own hello received.
>> > Loop partner's hellos at a given rate. << This last item is a bit of a misnomer. This isn't an extra feature the CPU has to do. The CPU on has to perform the first two action, which are the same (more or less) in both echo and non-echo modes. In echo mode the sending host sets its own MAC as the source MAC and the receiving node MAC as the destination MAC within the Ethernet headers. In the IP headers the source and destination IP are both the sending node's IP. So the receiving node receives the BFD packet because it has the destination MAC, but it see's the destination IP is the sending node, so this should be forwarded in hardware like any other L3 packet, so in echo mode the remote node that received the echo frame is unaware it is forwarding BFD packets for the node that send the echo packet. So there is no additional action for nodes running echo mode. So going back to your "to do" list: > To do list of one of the nodes in non-echo mode: > Tx at a given rate. > Reset dead timer if hello from remote node received. In this mode the remote nodes packet with the local node IP as the destination IP causing the packets to the punted. > To do list of one of the nodes in echo mode: > Tx at a given rate. > Reset dead timer if own hello received. In this mode the local node sends packets with the destination IP as its own IP since they are looped back, they will be punted upon return arrival. So in both cases what I expect to be happening is that the originating of BFD packets and checking of the received packet be they locally originated or remotely originated (echo more or non-echo mode respectively) is offloaded to the ASIC. So since we are doing more or less the same amount of work in ASIC, I'm not sure why echo mode is not support on the ME3600X/ME3800X/7600 LAN & CFC cards in hardware but non-echo mode is? Whatever the answer way we have reliably lab tested that 50ms x3 works in ME3600X/ME3800X and something like 500ms x3 works fine on 7600 LAN cards (that could probably go lower for 7600s tbh!) but some official word from Cisco would be nice. Cheers, James. _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
