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Dramatic bandwith impact when chaining multiple LS1021ATSN devkits

Question asked by Sebastien Merle on Dec 14, 2018
Latest reply on Jan 3, 2019 by alexander.yakovlev

For our prototype we are required to daisy chain multiple LS1021ATSN routers.

We are measuring the bandwidth by downloading a very large file over HTTP either directly between the client and the server or passing through different configuration of routers (numbered from 1 to 3):


|Direct | 112,00 MB/s (stable)       |
|1      |  52,80 MB/s to  98,00 MB/s |
|2      | 112,00 MB/s (stable)       |
|3      | 112,00 MB/s (stable)       |
|1+2    |  22,60 MB/s to  54,00 MB/s |
|1+3    |  19,00 MB/s to  69,30 MB/s |
|2+3    |  23,80 MB/s to  73,2 MB/s  |
|1+2+3  |   2,89 MB/s to   2,95 MB/s |


First we can see that router number 1 is acting strangely. this is the same router we keep having issue with when updating the configuration. It seems that router 1 is defective in some ways.


Second the drop of bandwidth when chaining multiple routers seems quite exaggerated. Even considering the configuration that include router 1 that is probably defective, the configuration with only router 2 and 3 chained shows a drop of 35 to 80 percent of bandwidth.


And finally, the measures were done downloading a 10 GB files and the average bandwidth swings wildly from one measure to the other. This could be related to the TCP congestion algorithm and the packet drops, but it still looks like too much variations to me.


Is there a way to reduce this dramatic lost of bandwidth ?


Attached are the configuration of the routers when chained together.


Thank you for your support.