SCP protocol question and outstanding requests in SFTP

Chris Rapier rapier at
Sat Oct 13 01:20:06 EST 2007

Damien Miller wrote:

> Just to be clear, I have zero interest in making any feature additions
> to scp and I think most of the developers feel the same way. It is a
> difficult protocol to extend,

Could you explain this in more detail or point out some resources that 
might explain some of the nuances?

The reason why I ask is that *many* of our users would like more 
functionality in scp. I do try to point them to sftp but they're 
generally unwilling due to perceived difficulties using SFTP in scripted 
situations (which has led me to think about patching SFTP to understand 
SCP style arguments eg sftp blah user at foo:~/bar but that is, at best, 
far down the line in things I want to work on).

Also, just as a point of curiosity, was the number of default 
outstanding messages in SFTP increased in 4.7? I ask because the default 
window size was increased to 1MB outstanding but the previous default of 
16 32KB messages would actually restrict the effective outstanding data 
size to 512KB in SFTP.

It looks like its still at 16 but I haven't dug deep enough to see if 
this disparity was addressed in some other way.


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