Category: Uncategorized

Should anyone ask, I really do love my neighbours…

… but not when they start impacting my WIFI calls. First some background. I run 2 open access points that regularly have multiple neighbours associated. I don’t mind them piggybacking and have everything locked down and traffic on my ADSL link heavily prioritised so they don’t impact my latency sensitive applications. Today one of them started using Google Earth intensively. I noticed this because I was on a sip call that started breaking up.

A quick bit of tcpdump’ing showed this application was chewing up all my wireless bandwidth. Incidentally I only have limited wireless bandwidth since there are about 12 access points tripping over each other’s frequencies from outside my window.
I have put them back in their box with this simple script. It prioritises all traffic leaving my wireless VLAN which connects to the 2 access points. Traffic is in 3 classes – my E61 address, my wireless laptop and finally “all other traffic”

Alternatively I could always re-enable imagiImageflip mode again.

the script:

WIRELESSDEV=vlan4
# first delete everything
tc -s qdisc del dev $WIRELESSDEV root
tc qdisc add dev $WIRELESSDEV root handle 2: htb default 30
tc class add dev $WIRELESSDEV parent 2: classid 2:1 htb rate 10mbit burst 15k

tc class add dev $WIRELESSDEV parent 2:1 classid 2:10 htb rate 1mbit burst 15k
tc class add dev $WIRELESSDEV parent 2:1 classid 2:20 htb rate 1mbit burst 15k
tc class add dev $WIRELESSDEV parent 2:1 classid 2:30 htb rate 1mbit burst 15k

tc qdisc add dev $WIRELESSDEV parent 2:10 handle 10: sfq perturb 10
tc qdisc add dev $WIRELESSDEV parent 2:20 handle 20: sfq perturb 10
tc qdisc add dev $WIRELESSDEV parent 2:30 handle 30: sfq perturb 10

# control outbound
tc filter add dev vlan4 parent 2: protocol ip prio 16 u32 match ip dst 10.15.11.8 flowid 2:10 # mobile
tc filter add dev vlan4 parent 2: protocol ip prio 16 u32 match ip dst 10.15.11.7 flowid 2:20 # laptop wireless
tc filter add dev vlan4 parent 2: protocol ip prio 16 u32 match ip dst 10.15.11.2 flowid 2:20 # switch maintenance
tc filter add dev vlan4 parent 2: protocol ip prio 16 u32 match ip dst 10.15.11.3 flowid 2:20 # switch maintenance
# all other traffic goes here since we set the default class to 2:30

Should anyone ask, I really do love my neighbours…

… but not when they start impacting my WIFI calls. First some background. I run 2 open access points that regularly have multiple neighbours associated. I don’t mind them piggybacking and have everything locked down and traffic on my ADSL link heavily prioritised so they don’t impact my latency sensitive applications. Today one of them started using Google Earth intensively. I noticed this because I was on a sip call that started breaking up.

A quick bit of tcpdump’ing showed this application was chewing up all my wireless bandwidth. Incidentally I only have limited wireless bandwidth since there are about 12 access points tripping over each other’s frequencies from outside my window.
I have put them back in their box with this simple script. It prioritises all traffic leaving my wireless VLAN which connects to the 2 access points. Traffic is in 3 classes – my E61 address, my wireless laptop and finally “all other traffic”

Alternatively I could always re-enable imagiImageflip mode again.

the script:

WIRELESSDEV=vlan4
# first delete everything
tc -s qdisc del dev $WIRELESSDEV root
tc qdisc add dev $WIRELESSDEV root handle 2: htb default 30
tc class add dev $WIRELESSDEV parent 2: classid 2:1 htb rate 10mbit burst 15k

tc class add dev $WIRELESSDEV parent 2:1 classid 2:10 htb rate 1mbit burst 15k
tc class add dev $WIRELESSDEV parent 2:1 classid 2:20 htb rate 1mbit burst 15k
tc class add dev $WIRELESSDEV parent 2:1 classid 2:30 htb rate 1mbit burst 15k

tc qdisc add dev $WIRELESSDEV parent 2:10 handle 10: sfq perturb 10
tc qdisc add dev $WIRELESSDEV parent 2:20 handle 20: sfq perturb 10
tc qdisc add dev $WIRELESSDEV parent 2:30 handle 30: sfq perturb 10

# control outbound
tc filter add dev vlan4 parent 2: protocol ip prio 16 u32 match ip dst 10.15.11.8 flowid 2:10 # mobile
tc filter add dev vlan4 parent 2: protocol ip prio 16 u32 match ip dst 10.15.11.7 flowid 2:20 # laptop wireless
tc filter add dev vlan4 parent 2: protocol ip prio 16 u32 match ip dst 10.15.11.2 flowid 2:20 # switch maintenance
tc filter add dev vlan4 parent 2: protocol ip prio 16 u32 match ip dst 10.15.11.3 flowid 2:20 # switch maintenance
# all other traffic goes here since we set the default class to 2:30

Should anyone ask, one can learn a great deal from the TV show “24”

Only loosers become system administrators through on the job training. Here’s what I learnt from 5 hours of “24” when sitting on the train back from Berlin. But first a minor rant:

Why does the film and TV industry keep shooting themselves in the foot? I was watching a legally acquired 8 DVD set but was unable to view one of the episodes due to them using the ARccOS copy protection system which makes some sectors look bad. But this was a paid for DVD set. Also, I have never understood why it’s necessary to advertise (and further piss off) the evils of piracy to people who have legally acquired your product. Why stick a 2 minute ad at the start of a film in the cinema? The 24 DVD was accompanied by a long, and un-fastforward-able advert about the evils of piracy. Seems a little patronising when the customer has just spent 50 Euro on your product and you have screwed up the disk enough that he cannot even watch one of the episodes.

But I digress. Here are my tips for working in the CTU (Counter Terrorism Unit for those not addicted to the show) as a sysadmin.

  • Wake up early. The first attack happens before 8am. This is no job for your normal sys-admin – you need to be in the office before lunch.
  • Engineering gets its own subnet. This came up in two episodes. I’m pleased they use a segmented network and have prescribed similar topologies on previous gigs. Alas, they always seem to be able to skip from one subnet to another so they should probably examine ACLs on on their (no doubt Cisco – see following point) routers more carefully.
  • CTU uses a VOIP infrastructure from Cisco. I was pleased to see multiple Cisco 7960G VOIP handsets deployed around the CTU office. Would love the have the firmware hack for the nice logo they have managed to get them to display. The real question is whether they have the SCCP or the SIP firmware loaded?
  • Pinging phones via GPRS. This was neat, and if I ran a CTU infrastructure, I would probably set my infrastructure up to run Smokeping against all my field agents phones. Lets hope they have a carrier that gives them real IP addresses when they open that GPRS channel. Fear the latency. I do.
  • CTU uses FVWM. I still do too, but could never work with that bitchface of a boss.
  • CTU didn’t pay their lighting bill. That or they are all haxors. I have never seen such a dark office environment.
  • Terrorists should switch from quadrule ROT13 and use PGP. No, really.
  • Mobile phones have very good batteries. Jack manages to run around all day with the same phone glued to his ear. I want a hydrogen cell batter that can last that long too.
  • The daughter of the secretary of defence runs a tcpdump window on her screen. I would date her in a second and help her with some of her libpcap syntax. What a babe.
  • Microsoft managed to get at least someone to buy their tablet computing solution. Even if it was just a government department that can’t afford to pay their electricity bill.
  • Data still makes a noise when being written to a screen. Are they using accoustic couplers or something. Why is it that in the “we can’t afford to pay our lighting bill” bunker, all data when being written to a screen still makes a high pitched noise for each character written.
  • Deleting files does not work. Even a DOS junkie will tell you this.
  • Using “more” or “less” is so old school. Hexdump is common. Alas didn’t see the Secretary of Defence’s daughter using it
  • Jack thinks that he cannot access files when their ownership is rwxr-xr-x. ‘nuff said.

Should anyone ask, one can learn a great deal from the TV show “24”

Only loosers become system administrators through on the job training. Here’s what I learnt from 5 hours of “24” when sitting on the train back from Berlin. But first a minor rant:

Why does the film and TV industry keep shooting themselves in the foot? I was watching a legally acquired 8 DVD set but was unable to view one of the episodes due to them using the ARccOS copy protection system which makes some sectors look bad. But this was a paid for DVD set. Also, I have never understood why it’s necessary to advertise (and further piss off) the evils of piracy to people who have legally acquired your product. Why stick a 2 minute ad at the start of a film in the cinema? The 24 DVD was accompanied by a long, and un-fastforward-able advert about the evils of piracy. Seems a little patronising when the customer has just spent 50 Euro on your product and you have screwed up the disk enough that he cannot even watch one of the episodes.

But I digress. Here are my tips for working in the CTU (Counter Terrorism Unit for those not addicted to the show) as a sysadmin.

  • Wake up early. The first attack happens before 8am. This is no job for your normal sys-admin – you need to be in the office before lunch.
  • Engineering gets its own subnet. This came up in two episodes. I’m pleased they use a segmented network and have prescribed similar topologies on previous gigs. Alas, they always seem to be able to skip from one subnet to another so they should probably examine ACLs on on their (no doubt Cisco – see following point) routers more carefully.
  • CTU uses a VOIP infrastructure from Cisco. I was pleased to see multiple Cisco 7960G VOIP handsets deployed around the CTU office. Would love the have the firmware hack for the nice logo they have managed to get them to display. The real question is whether they have the SCCP or the SIP firmware loaded?
  • Pinging phones via GPRS. This was neat, and if I ran a CTU infrastructure, I would probably set my infrastructure up to run Smokeping against all my field agents phones. Lets hope they have a carrier that gives them real IP addresses when they open that GPRS channel. Fear the latency. I do.
  • CTU uses FVWM. I still do too, but could never work with that bitchface of a boss.
  • CTU didn’t pay their lighting bill. That or they are all haxors. I have never seen such a dark office environment.
  • Terrorists should switch from quadrule ROT13 and use PGP. No, really.
  • Mobile phones have very good batteries. Jack manages to run around all day with the same phone glued to his ear. I want a hydrogen cell batter that can last that long too.
  • The daughter of the secretary of defence runs a tcpdump window on her screen. I would date her in a second and help her with some of her libpcap syntax. What a babe.
  • Microsoft managed to get at least someone to buy their tablet computing solution. Even if it was just a government department that can’t afford to pay their electricity bill.
  • Data still makes a noise when being written to a screen. Are they using accoustic couplers or something. Why is it that in the “we can’t afford to pay our lighting bill” bunker, all data when being written to a screen still makes a high pitched noise for each character written.
  • Deleting files does not work. Even a DOS junkie will tell you this.
  • Using “more” or “less” is so old school. Hexdump is common. Alas didn’t see the Secretary of Defence’s daughter using it
  • Jack thinks that he cannot access files when their ownership is rwxr-xr-x. ‘nuff said.

Should anyone ask, something about drills

Found an interesting quote last night carved into a wall in a Berlin toilet wall:

“People don’t want to buy a quarter-inch drill, they want a quarter-inch hole" 

As I think about building software and websites, it’s a nice thought to bear in mind.   Guess someone else working in Berlin was also thinking about customer focus. I looked it up and the quote is by someone called Theodore Levitt.  It beats some of the other quotes that I have seen on the streets here like:

"The eye of the shit bird is watching you" 

Only in Berlin.

Should anyone ask, something about drills

Found an interesting quote last night carved into a wall in a Berlin toilet wall:

“People don’t want to buy a quarter-inch drill, they want a quarter-inch hole" 

As I think about building software and websites, it’s a nice thought to bear in mind.   Guess someone else working in Berlin was also thinking about customer focus. I looked it up and the quote is by someone called Theodore Levitt.  It beats some of the other quotes that I have seen on the streets here like:

"The eye of the shit bird is watching you" 

Only in Berlin.