[hpsdr] Packet Length and Fragmentation

[Chris Albertson]

On Sep 21, 2010, at 5:05 AM, Thierbach, Ed wrote:

> ***** High Performance Software Defined Radio Discussion List *****
> 
> Hi, Jeremy -- what happens in the case where 2 systems on the same network segment are set to different MTUs?  Will they simply not communicate?
> 
> For example, if I have 2 Linux machines, and on one I issue 'ifconfig eth0 mtu 750' and on the other 'ifconfig eth0 mtu 1500', will the receiving PC just generate RX errors and discard the packets?
> 

It will work find.  Systems can accept and process any incoming packet length and in normal use see many that are shorter than the maximum.  The MTU sets only the maximum lenth.  The only reason you'd set it small is because (1) your router connects to a network that uses short ppackets or (2) connects to a very unreliable network and must do many re-tries on such networks packets fail in proportion to their length.  As this is a ham list, I'm thinking of HF or VHF digital links of an example of networks where you might want a shorter MTU.

Ethernet controllers and IP software can handle small packets just find and as I said above see smallers packets routinly


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