* [ECOS] Ymodem error checking
@ 2005-07-03 14:39 Øyvind Harboe
2005-07-03 15:18 ` Gary Thomas
0 siblings, 1 reply; 3+ messages in thread
From: Øyvind Harboe @ 2005-07-03 14:39 UTC (permalink / raw)
To: ecos-discuss
How certain can I be that Ymodem will either:
a) report a failure
b) receive the file correctly
Is adding a layer on top of Ymodem to check that the file was received
correctly ill-informed paranoia?
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Øyvind Harboe
http://www.zylin.com
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [ECOS] Ymodem error checking
2005-07-03 14:39 [ECOS] Ymodem error checking Øyvind Harboe
@ 2005-07-03 15:18 ` Gary Thomas
2005-07-03 15:56 ` Øyvind Harboe
0 siblings, 1 reply; 3+ messages in thread
From: Gary Thomas @ 2005-07-03 15:18 UTC (permalink / raw)
To: Øyvind Harboe; +Cc: eCos Discussion
On Sun, 2005-07-03 at 16:40 +0200, Øyvind Harboe wrote:
> How certain can I be that Ymodem will either:
>
> a) report a failure
> b) receive the file correctly
>
>
> Is adding a layer on top of Ymodem to check that the file was received
> correctly ill-informed paranoia?
Each [relatively small] record in the Y-modem protocol contains
a simple checksum. This must match for the packet to be ACK'd
Also, packets are numbered and will only be accepted in the proper
order. This level of checking is sufficient (at least 99% of the
time IMHO)
You could always generate a binary checksum on the data and then
validate that using the 'cksum' command in RedBoot. In this way,
you could verify that everything was transfered correctly, a step
above checking all the little pieces. The tricky part with this
is that some files which are downloaded have holes in them and you'd
need to make sure that both checksums assume the same value for
the hole.
--
------------------------------------------------------------
Gary Thomas | Consulting for the
MLB Associates | Embedded world
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [ECOS] Ymodem error checking
2005-07-03 15:18 ` Gary Thomas
@ 2005-07-03 15:56 ` Øyvind Harboe
0 siblings, 0 replies; 3+ messages in thread
From: Øyvind Harboe @ 2005-07-03 15:56 UTC (permalink / raw)
To: Gary Thomas; +Cc: eCos Discussion
> Each [relatively small] record in the Y-modem protocol contains
> a simple checksum. This must match for the packet to be ACK'd
> Also, packets are numbered and will only be accepted in the proper
> order. This level of checking is sufficient (at least 99% of the
> time IMHO)
OK. Thanks.
It seems to me that there are many other things to worry about before
false successes from Ymodem uploads show up on the radar.
--
Øyvind Harboe
http://www.zylin.com
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2005-07-03 14:39 [ECOS] Ymodem error checking Øyvind Harboe
2005-07-03 15:18 ` Gary Thomas
2005-07-03 15:56 ` Øyvind Harboe
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