> 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 really doubt you'll have any problems at that data rate. But It will be interesting to hear for sure! John > > 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 >> >> >> >> >> >> >> >> >> >> >
