Thanks for pointing out that the spec differed from the catalog description I had read. I think I'm going to go with a Cisco SG200-26. It has a 4MB shared buffer for 24+2 mini-GBIC gigabit ports. This is the largest shared buffer I've seen for ~24 ports. It supports frame sizes up to 10kbytes
Will let you know if I have problems. I believe you and others are making the point that the data will be synchronous from all 16 boards and therefore the data rate will be high for brief blips rather than a continuous average. But I would have to hope that 1.2Mbytes/sec couldn't overpower a gigabit switch even if it arrived all at once (I have some discretion in how often the packets are generated). I think/hope that the larger problem will be on the linux side buffering for which I will try Jason's suggestions. Thanks to all for the help. Tom On Tue, Jun 21, 2011 at 1:52 AM, Jean Borsenberger <[email protected]> wrote: > On Mon, 2011-06-20 at 12:54 -0700, [email protected] > wrote: > Hello, > >> 0.5 mbyte buffer per port > > I read in the spec: Buffer memory: 512 KB embedded memory per unit > > seems global for a switch. > > That resemble to what I am used to. Usually on chip port buffers are > at most 17KB. > > These devices are tuned for a traffic which is mainly TCP, and UDP with > data integrity control delegated to clients. > > Basically they drop a lot of packets, which is of little importance in > usual > use, as those packets are requested by the listener and re-emitted. > Of course in contention situations this behaviour may impact badly > things > like voice transportation. > > In your design, many lines converge to one. Hope the time statistic is > fair. The time to be considered to examine this is: > buffer_size/effecive_line_speed > Be carefull that not all of the buffer memory may be available for one > port, depending on the policy adopted in the switching strategy. > > > Jean > > > > > > > > > >
