Mac Forum / General / Networking / August 2007

With reference to the article elsewhere in this thread:
http://docs.info.apple.com/article.html?artnum=305420

The 1.5 MB limit for AFP file transfer to work kicked in with the
10.4.9 system update on my G5 iMac, so it isn't just a problem
with OS X Server.

Since I had a USB card in the classic Mac, I ended up just using
a USB key to transfer the files I wanted, so I haven't tried the
fix suggested. I don't suppose you have an external burner, and
a suitable version of Toast on the classic Mac?

In Fetch, you can get it to get/put the files as .hqx, but you may have
to tweak the preference settings to get it to apply that to all files.
It's been a while since I had to transfer files between OS 8/9 and OS X
boxen that way, so unfortunately I don't remember the precise details.

The link that was posted here earlier

http://docs.info.apple.com/article.html?artnum=305420

resonated with me as there have been similar weirdnesses with the latest
LINUX kernel releases.

I can't say that the following is an exact description of the issues,
but its right in general terms.

Essentially the rise in everyones bandwidth has led to usage of some
slightly arcane areas of the TCP/IP specification, mostly around the
area of the window size..the amount of data in packets that will be sent
before the sending machine expects an acknowledgement.

This is supposed to be negotiated by the sending and receiving machine,
but machines in between (typically routers) also can interject and
request smaller sizes.

It seems that many older implementations on older machines and routers
do not work correctly with the modern kernels: The workaround is to
reconfigure the TCP/IP packet sizes to limit their size..whilst this
results in a performance hit on gigabit Ethernet and the like, it
normally has little impact on normal usage.

The symptoms are generically timed out connections during large sized
transfers..

Use of the netstat and ifconfig tools will normally show unusually high
packet loss.

The posted link shows that by adjusting the apple file protocol tunings,
some gains are to be had..this is NOT the same was what I have been
describing, but its very similar.
In practice depending on what you are connecting to, if any data
overruns a buffer, you will get strange effects like those noted..and
experience shows that even a different hub or switch may make things
work better.

I went through a long process when I first migrated to OS X. All Macs
were PPC. After the dust settled, some older Macs are mountable on OS X
ones, and some seem not to be. I do not know why.

In one case, I cloned the entire system folder from one that worked to
one that did not -- and it still did not.

I have never seen a failure when mounting an OS X shared folder on an
older OS Mac.

In one case, in order to make things work, I used VNC to control a
remote Mac using OS 8.6. Remotely controlling the older Mac, I mounted
the OS X Mac (the one I was running the VNC client on) on the 8.6 one,
and then successfully transferred files whenever I needed to.

Isaac