FTP and window scaling

FTP and window scaling

Post by Manish Jai » Fri, 06 Jul 2001 09:17:33



Hello,

On window scaling option in TCP header, RFC 1323 says the following :-

This option [ window scaling ] may be sent in an initial <SYN> segment
( i.e. , a segment with the SYN bit ON and ACK bit OFF ).
It may also be sent in <SYN,ACK> segment, but only if a Window Scale
option was received in the initial <SYN> segment.

Now in FTP protocol , the FTP client does a passive open for data
connection, sends the data port to server using PORT command and FPT
server does the active open  to this port.

Since the FTP server is sending the <SYN> segment and if it does not
set the window scaling option [even though the kernel supports it],
then I think the FTP client can in no way use the window scaling option.

A possible solution to it might be :
TCP implementation must set ( zero/non zero depending on use ) the
window scale option in <SYN> packet if the kernel supports it.

In this way , the end receiving the <SYN> packet has the option
of either using the window scale option.

Any comments,

Manish Jain

 
 
 

FTP and window scaling

Post by Maarten Wiltin » Fri, 06 Jul 2001 19:46:28



>Hello,

>On window scaling option in TCP header, RFC 1323 says the following :-

>This option [ window scaling ] may be sent in an initial <SYN> segment
>( i.e. , a segment with the SYN bit ON and ACK bit OFF ).
>It may also be sent in <SYN,ACK> segment, but only if a Window Scale
>option was received in the initial <SYN> segment.

>Now in FTP protocol , the FTP client does a passive open for data
>connection, sends the data port to server using PORT command and FPT
>server does the active open  to this port.

>Since the FTP server is sending the <SYN> segment and if it does not
>set the window scaling option [even though the kernel supports it],
>then I think the FTP client can in no way use the window scaling option.

>A possible solution to it might be :
>TCP implementation must set ( zero/non zero depending on use ) the
>window scale option in <SYN> packet if the kernel supports it.

>In this way , the end receiving the <SYN> packet has the option
>of either using the window scale option.

>Any comments,

FTP will let you connect in the other direction, too.

Groetjes,
Maarten Wiltink

 
 
 

FTP and window scaling

Post by Barry Margoli » Fri, 06 Jul 2001 23:07:31



Quote:>A possible solution to it might be :
>TCP implementation must set ( zero/non zero depending on use ) the
>window scale option in <SYN> packet if the kernel supports it.

>In this way , the end receiving the <SYN> packet has the option
>of either using the window scale option.

Yes.  I haven't checked, but I suspect that most TCP implementations
already do this.  RFC 1323 specifically says:

      Thus, a TCP that is prepared to scale windows should send the option,
      even if its own scale factor is 1.

--

Genuity, Burlington, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.

 
 
 

1. Scaled bitmaps vs. scaled outlines

Question:  is it possible (either directly or through the xfs) to make
X use the bitmapped fonts when they DON'T need to be scaled, but then use
scalable Type1 fonts when there are no prescaled fonts available?  I.E.,
right now, if I use like 12 pt or 14 pt times, it looks good because it is
a pre-scaled bitmap, but if I try like 40 pt times, instead of using the
Type1 times font that I have installed, it scales up the bitmap font to 40
pt size and it looks blocky and like crap.  However, if I put the Type1 dir.
before the 75dpi dir in my fontpath, the 75dpi fonts are all but ignored, and
the Type1 times font scaled to 12 or 14 points looks crappy.

So you see the dilemma?  How do I solve this one?

-----------------------------------------------------------------------------

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