[USRP-users] USRP X310 Maximum frame size: 7972 bytes.

Marcus D. Leech patchvonbraun at gmail.com
Wed Feb 20 08:04:51 EST 2019


On 02/20/2019 07:50 AM, akin soysal via USRP-users wrote:
> Hello,
>
> In order to decrease the latency, I was playing around with the MTU 
> size setting it to 4000, 7000, 9000 and now a permanent error happens 
> in my server connected to USRP. I tried it with two different USRP 
> X310s and the problem happens in both. Where does the 7972 bytes come 
> from? Thanks. Regards, Akın
>
> /uhd/uhd/host/build$ uhd_usrp_probe
> [INFO] [UHD] linux; GNU C++ version 5.4.0 20160609; Boost_105800; 
> UHD_3.13.1.HEAD-0-gbbce3e45
> [INFO] [X300] X300 initialization sequence...
> [INFO] [X300] Maximum frame size: 7972 bytes.
> [INFO] [X300] Radio 1x clock: 200 MHz
> [WARNING] [X300] For this connection, UHD recommends a send frame size 
> of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [WARNING] [X300] For this connection, UHD recommends a receive frame 
> size of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [WARNING] [X300] For this connection, UHD recommends a send frame size 
> of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [WARNING] [X300] For this connection, UHD recommends a receive frame 
> size of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [INFO] [0/DmaFIFO_0] Initializing block control (NOC ID: 
> 0xF1F0D00000000000)
> [INFO] [0/DmaFIFO_0] BIST passed (Throughput: 1306 MB/s)
> [INFO] [0/DmaFIFO_0] BIST passed (Throughput: 1311 MB/s)
> [WARNING] [X300] For this connection, UHD recommends a send frame size 
> of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [WARNING] [X300] For this connection, UHD recommends a receive frame 
> size of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [WARNING] [X300] For this connection, UHD recommends a send frame size 
> of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [WARNING] [X300] For this connection, UHD recommends a receive frame 
> size of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [INFO] [0/Radio_0] Initializing block control (NOC ID: 0x12AD100000000001)
> [WARNING] [X300] For this connection, UHD recommends a send frame size 
> of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [WARNING] [X300] For this connection, UHD recommends a receive frame 
> size of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [WARNING] [X300] For this connection, UHD recommends a send frame size 
> of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [WARNING] [X300] For this connection, UHD recommends a receive frame 
> size of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [INFO] [0/Radio_1] Initializing block control (NOC ID: 0x12AD100000000001)
> [WARNING] [X300] For this connection, UHD recommends a send frame size 
> of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [WARNING] [X300] For this connection, UHD recommends a receive frame 
> size of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [WARNING] [X300] For this connection, UHD recommends a send frame size 
> of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [WARNING] [X300] For this connection, UHD recommends a receive frame 
> size of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [INFO] [0/DDC_0] Initializing block control (NOC ID: 0xDDC0000000000000)
> [WARNING] [X300] For this connection, UHD recommends a send frame size 
> of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [WARNING] [X300] For this connection, UHD recommends a receive frame 
> size of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [WARNING] [X300] For this connection, UHD recommends a send frame size 
> of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [WARNING] [X300] For this connection, UHD recommends a receive frame 
> size of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [INFO] [0/DDC_1] Initializing block control (NOC ID: 0xDDC0000000000000)
> [WARNING] [X300] For this connection, UHD recommends a send frame size 
> of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [WARNING] [X300] For this connection, UHD recommends a receive frame 
> size of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [INFO] [0/DUC_0] Initializing block control (NOC ID: 0xD0C0000000000000)
> [WARNING] [X300] For this connection, UHD recommends a send frame size 
> of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [WARNING] [X300] For this connection, UHD recommends a receive frame 
> size of at least 8000 for best
> performance, but your system's MTU will only allow 7972.This will 
> negatively impact your maximum achievable sample rate.
> [INFO] [0/DUC_1] Initializing block control (NOC ID: 0xD0C0000000000000)
Some network hardware will accept any MTU you give it, but only actually 
be able to deliver a much smaller MTU.  This may be the case here.





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