PDiffs are still useful //at 03:26 //by abe

… probably just not as default.

I do agree with Richi and with Michael that disabling PDiffs by default gives the big majority of Debian Testing or Unstable users a speedier package list update.

I’m though not sure, if disabling PDiffs by default would

• also have an performance impact on our mirrors — it surely would have a traffic impact on the mirrors;
• really bring a benefit for Debian Stable users as Debian Stable changes seldomly and hence there are not that many PDiffs to download and apply — at least I can’t remember being annoyed by PDiffs anywhere else than on Debian Testing and Debian Unstable. Even the repositories with security updates don’t change that often.

Additionally I want to remind you that PDiffs per se are nothing bad and should be continued to be supported:

• Because there are still areas, even in “civilized” countries, where only small bandwidth is available and where using PDiffs reduces the download time a lot. Yes, also in Germany. BTDT. Only until recently there was no Fibre, no DSL, very bad UTMS reception and otherwise just EDGE at my parents’ home. (LTE was available far too expensive until recently.) And I was very happy about not having to download 30 MB or such just for seeing if there are updates at all, because 25 kB/s was the fastest download rate I could get (peaks, not average).
• Because it seems to be in fashion with big ISP near-to-monoplists, especially in Germany, to cut off your nice bandwidth if you transfer too many Megabytes. Keyword “Drosselkom”. If you happen to be a customer of such a shitty ISP, you may be happy to reduce your traffic amount by using PDiffs instead of downloading the full package list every time.

So yes, disabling PDiffs by default is probably ok, but the feature must be kept available for those who haven’t 100 MBit/s fibre connection into their homes or are sitting just one hop away from the next Debian mirror (like me at work :-).

Oh, and btw., for the very same reasons I’m also a big fan of debdelta which is approximately the same as PDiffs, just not for package lists but for binary packages. Using debdelta I was able to speed up my download rates over EDGE to up to virtual 100 kB/s, i.e. by factor four (depending on the packages). Just imagine a LibreOffice minor update at 15 kB/s average download rate. ;-)

And all these experiences were not made with a high-performance CPU but with the approximately 5 year old Intel Atom processor of my ASUS EeePC 900A. So I used PDiffs and debdelta even despite having a slight performance penalty on applying the diffs and deltas.

Debian and GPRS with the Nokia E51 //at 01:33 //by abe

A while ago I wanted to have internet over GPRS (either EDGE or UMTS) via my Nokia E51 working before I leave for the weekend. But whatever I tried, I always got an ERROR if I sent any AT command. Even ATZ and ATH resulted in errors. So started googling for all components: I found AT commands which are said to work with the Nokia E51, I found AT commands which are said to work with Swisscom GPRS and I found many sites describing how to setup a bluetooth modem.

But since the even those AT commands which should work with both, Swisscom GPRS and Nokia E51 didn’t work at all, I noticed that all the Nokia E51 howtos were using the USB cable. So I tried that, too, and it worked immediately. It looks very strange to me that the set of AT commands is dependend on which way you connect to the phone. :-/

So here’s my working PPP config:

hide-password
noauth
connect "/usr/sbin/chat -e -f /etc/chatscripts/swisscom-gprs"
/dev/ttyACM0
460800
defaultroute
crtscts
user "guest"
usepeerdns
noccp
bsdcomp 0,0
lcp-echo-failure 10000
lcp-echo-interval 1000
asyncmap 0
novj
nomagic

TIMEOUT 5
ABORT BUSY
ABORT 'NO CARRIER'
ABORT VOICE
ABORT 'NO DIALTONE'
ABORT 'NO ANSWER'
ABORT DELAYED
ABORT ERROR
'' \nAT
TIMEOUT 12
OK ATH
OK ATE1
OK 'AT+CGDCONT=1,"IP","gprs.swisscom.ch"'
OK ATD*99#
CONNECT ""

So I have now four levels of mobile computing available:

• Nokia E51 with T9 and phone keyboard (for short texts)
• Nokia E51 with Nokia SU-8W bluetooth keyboard (for longer texts and emergencies, see photo on the right)
• ASUS EeePC (7", 630 MHz Celeron, 2GB RAM, 4GB SSD) with Nokia E51 as modem (complete computer, but still small, portable and nearly always with me)
• Lenovo ThinkPad T61 (14" wide screen, 2.2 GHz Core2Duo, 4GB RAM, 160 GB SATA Disk) with Nokia E51 as modem (complete computer with power and disk space)

Should suffice in nearly all situations. ;-)