Re: [coldsync-hackers] Regression testing / scripting POSE

[Andrew Arensburger <arensb+CSHackers@ooblick.com>]

On Wed, Feb 28, 2001 at 11:29:47AM -0800, Michael Hope wrote:
> Yip, have done, but this and all the other documentation I can find out 
> there is missing a few key parts.  I've been unable to find _any_ 
> documentation on PADP or DLP on the Palm site.  They do describe SLP, but 
> under a different name.

	FWIW, there's some discussion of SLP at
http://www.palmos.com/dev/tech/docs/palmos/SerialCommunication.html
In particular, it says that the XID is not used by SLP; it's solely
for the benefit of higher-level protocols (PADP).

	Unfortunately, you appear to be correct: I wasn't able to find
any documentation on PADP, and precious little about SLP.

> Both pilot-link and coldsync handle last fragment loss 
> differently.  pilot-link will stop transmitting the current packet even if 
> it is half way through if it gets a unexpected data packet.  coldsync will 
> ack and drop the incoming data fragment, then begin retransmitting its 
> packet from the start with a new XID.

	Flynn's article on PADP implies that the XID is used for an
entire PADP (or is it DLP?) exchange. Thus, if PADP breaks a packet up
into ten fragments, it'll send each fragment out in sequence, and
receive an ACK for each one. All ten fragments, and all ten ACKs, will
have the same XID.
	This is what ColdSync does. The only exception is when it
receives a data packet when it was expecting an ACK. Then it picks a
new XID, one different from the XID on the packet it just received.

> Both use the same XID for all fragments in a packet.  Interestingly enough, 
> a real Palm handles the XID changing for each fragment fine.

	That just means that PalmOS is robust (or that it doesn't do
enough error-checking :-) ). It doesn't answer the question of what
the correct behavior is.

-- 
Andrew Arensburger                      This message *does* represent the
arensb@ooblick.com                      views of ooblick.com
	       Indecision is the basis of flexibility.

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