# Packet size UHD vs libusrp2

**URL:** <https://www.ruby-forum.com/t/packet-size-uhd-vs-libusrp2/203276>\
**Category:** GNU Radio\
**Created:** [February 16, 2011, 10:03pm UTC](https://www.ruby-forum.com/t/packet-size-uhd-vs-libusrp2/203276 "2011-02-16T22:03:38Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![luislavena](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/0ea827/32.png) [@luislavena](https://www.ruby-forum.com/u/luislavena)\
**Post date:** [February 16, 2011, 10:03pm UTC](https://www.ruby-forum.com/t/packet-size-uhd-vs-libusrp2/203276/1 "2011-02-16T22:03:38Z")

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Hi,  
in libusrp2 samples are sent to device in packets of 370 samples,  
while in UHD now the max is 362,  
is there any way to have 370 in UHD as well ?

Regards  
Gaetano

–

> **[c++ today](http://cpp-today.blogspot.com)**
>
> "Almost" day by day thoughts on code inspected

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**Author:** ![Gaetano\_M](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/45deac/32.png) [@Gaetano\_M](https://www.ruby-forum.com/u/Gaetano_M)\
**Post date:** [February 16, 2011, 10:24pm UTC](https://www.ruby-forum.com/t/packet-size-uhd-vs-libusrp2/203276/2 "2011-02-16T22:24:20Z")

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On 02/16/2011 01:02 PM, Gaetano M. wrote:

> Hi,  
> in libusrp2 samples are sent to device in packets of 370 samples,  
> while in UHD now the max is 362,  
> is there any way to have 370 in UHD as well ?

Yes and maybe: The default recv\_frame\_size is the mtu of 1472 for a  
maximum length udp packet. The samples per packet is directly calculated  
from this number. You can increase this, however, your network card may  
or may not accept frames greater than 1500 bytes.

[http://www.ettus.com/uhd\_docs/manual/html/transport.html#transport-parameters](http://www.ettus.com/uhd_docs/manual/html/transport.html#transport-parameters)

-josh

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**Author:** ![Gaetano\_M](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/45deac/32.png) [@Gaetano\_M](https://www.ruby-forum.com/u/Gaetano_M)\
**Post date:** [February 16, 2011, 11:48pm UTC](https://www.ruby-forum.com/t/packet-size-uhd-vs-libusrp2/203276/3 "2011-02-16T23:48:20Z")

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On Wed, Feb 16, 2011 at 10:22 PM, Josh B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> or may not accept frames greater than 1500 bytes.
> 
> [http://www.ettus.com/uhd\_docs/manual/html/transport.html#transport-parameters](http://www.ettus.com/uhd_docs/manual/html/transport.html#transport-parameters)

So changing ups\_per\_fifo it should be possible, I will try it.

Regards  
Gaetano

–

> **[c++ today](http://cpp-today.blogspot.com)**
>
> "Almost" day by day thoughts on code inspected