[OZAPRS] HF Gateways

Ray Wells vk2tv at exemail.com.au
Mon Jun 29 19:41:59 EST 2009


Excuse my ignorance of TTL and thank you for the explanation.

Re exponential backoff and ax25, I know that Linux has either 
exponential or linear as a user selectable option. It's a long time 
(1994) since I used JNOS but I "think" it also offered the option. I 
don't know about other implementations of ax25.

Ray vk2tv

James Cameron VK2LQZ wrote:
> On Mon, Jun 29, 2009 at 06:06:32PM +1000, Ray Wells wrote:
>> With numbered ax25 frames the "within reason" is determined by RETRY  
>> which is typically 10. Is the TCP/IP equivalent the TTL (Time To Live)  
>> parameter?
> No.  TTL determines how many times a single packet is repeated by
> internet routers and gateways before it is no longer repeated.
> The amount of time a TCP connection may be stalled doing retries is
> determined by (a) any keep-alive setting of the operating system or
> application, or (b) any timer in the application that eventually gives
> up and announces a timeout.
> TCP retries use an exponential backoff.  I'm not yet sure what AX.25
> uses.  Still learning AX.25.
> APRS uses "if it didn't get through, don't worry, we'll send another one
> soon."  ;-)

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