> -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Bob Woodruff > Sent: Friday, November 04, 2005 10:58 AM > To: 'Fab Tillier'; 'Sean Hefty'; Rick Frank > Cc: [email protected] > Subject: RE: [openib-general] [ANNOUNCE] > ContributeRDS(ReliableDatagramSockets) to OpenIB > > Fab wrote, > >There is not a 1:1 relationship between a UDP application > socket and an > >IB > QP, > >rather there is a single IB connection between systems over which > >traffic > from > >multiple UDP sockets flows. > > >- Fab > > That would probably provide better scalability, since there > would not be a 1:1 mapping between UDP sockets and IB > connections, however for large clusters there may still be a > scalability issue if every node needs to have a connection to > every other node. > If you implemented it on top of datagrams instead, then each > node would only need one QP, rather than one for every node > in the cluster. >
But then the application would have to take responsibility for congestion control and retries after network packet losses. RDS allows an application all the benefits of a reliable connection without the overhead, except for per connection back-pressure. Many applications do not need pre-connection back-pressure since they already have session-wide flow control policies in place. Going from one connection for each pair of application endpoints to one connection for each pair of hosts is a major improvement. For most applications going down to a single QP after that is not sufficiently valuable to add the complexity of working over a totally unreliable protocol. _______________________________________________ openib-general mailing list [email protected] http://openib.org/mailman/listinfo/openib-general To unsubscribe, please visit http://openib.org/mailman/listinfo/openib-general
