computers

Port 25

South Korea is reportedly preparing to block TCP port 25 and force all mail traffic through "official mail servers", whatever that means. The BBC article isn't much on technical details. I'm still on the fence about blocking port 25. Fundamentally, I'm opposed to blocking ports outright. If somebody is shown to abuse a service, I'm fine with restrictions. I'm not excited about the prospect of requiring all mail to go through a central server, whether it's mine or someone else's.

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World IPv6 Day Wrap-up

Looks like World IPv6 Day was a good success. I saw a lot of traffic on NANOG announcing various issues people had seen, and many people declaring success. My own little fiefdom experienced relatively few problems. My Linux laptop had no issues with Google, Facebook and the other sites I could find. I reset my traffic counters this morning so I could watch it:

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NAT

If you've ever thought to yourself, "self, I'm going to borrow these public IP addresses which aren't mine and use them for my internal, natted network", well then let me set you straight. Don't do it. Disaster will strike at some point and the consequences will not be good. But if you do it anyway, don't expect me to feel sorry for you either.

Also, NAT sucks.

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UTOSC 2010 Day 2: Exploring The Radio Frequency Spectrum

I attended Robert Bolton's presentation on amateur (aka ham) radio. I was excited about this one for two reasons. First, radio is radio and I hope that in learning amateur radio I'll better understand the digital radios I use at work. Second, I've had a desire to be a ham ever since I was exposed to it as a wee little Boy Scout. I'll be taking my test in the next couple weeks, if everything goes according to plan (doesn't it always?). The one thing that came out of this presentation and excited me more than anything was that Asterisk has a radio interface (app_rpt) which you can use to create a phone patch system. I realize it's not exceptionally useful, but it does sound like a great project.

Miscellaneous Notes:

  • modulation analog: AM, SSB, FM. digital: PSK, FSK, ASK, QAM. spread spectrum: DSSS, FHSS
  • ke7zea
  • packet radio built into linux kernel
  • very slow speeds
  • gordon west book on radio theory
  • gpredict - satellite tracker
  • aprs - gps-based location reporting
  • software radio - gnu radio, universal software radio peripheral
  • asterisk app_rpt
  • ddwrt - can use more power w/ amateur license. call sign as ssid. no encryption.
  • echolink - windows based software
  • irlp - internet repeater link project

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UTOSC 2010 Day 2: Custom Puppet Facts

After a delicious trip to Pirate O's for lunch, it was back for a presentation by Joseph Hall on custom Puppet facts. Even ignoring the fact that I came in late, a lot of this was way over my head. It reminded me that I would do well to invest some more time into my Puppet system as there are many many more things I could do with it. If anybody has some free time I could borrow, please let me know.

Miscellaneous Notes:

  • manage fstab
  • hosts
  • require "facter"
  • Facter.add
  • external node classifier. use any language as long as output is yaml
  • classifier runs on puppetmaster
  • custom facts run on client
  • http://docs.puppetlabs.com/guides/external_nodes.html
  • subscribe/notify

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UTOSC 2010 Day 2: Advanced Git

Git has become my favorite version control of late, so I was very excited about this presentation. With that, I attended Tim Harper's presentation on Advanced Git. We got started 30 minutes late, he had some technical issues with his content, and we ended up with only 15 minutes of class time. That was a real disappointment. I did learn about gitk, a repository visualizer. I think I have a somewhat better idea on how to browse around my branches.

Miscellaneous Notes:

  • rebase
  • clean commits
  • bisect
  • always review before you commit
  • git add -p - yes/no before it adds
  • gitk - repository visualizer. gitk --all
  • tig - console visualizer
  • git log branch1...branch2 - show changes that are same in both branches
  • git reflog
  • lose your head

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UTOSC 2010 Day 1: Twisted

Last presentation for the day was from Gabe Gunderson. We were all a little concerned that Gabe would show up. Turned out due to a miscommunication he thought the presentation started half an hour later. Oh, well. Life goes on.

Gabe gave us an introduction to Twisted which is an event driven networking framework. Sounds like a nice way to abstract away the details of a network application. I was particularly interested in this since I'm using Zenoss, which is Python based. So far I can't see quite how this will fit into anything I'm doing.

Miscellaneous Notes:

  • event driven network framework for python
  • MIT license
  • protocols and transports separated
  • network and gui share event paradigm
  • event driven means debugging is a pain
  • events means you have to save context
  • "deferreds" are returned by functions that run asynchronously
  • common classes: reactor, protocol
  • protocol.Protocol - wire protocol (pop3, etc or write your own)
  • protocol.ClientFactory - creates instances of class for each connections
  • perspective broker

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UTOSC 2010 Day 1: TORQUE

Second class I unfortunately came in a little late, so I missed a few things (including a seat!), which is sad because it was a good presentation. Scott McQuay showed us TORQUE. It's a cluster resource manager, which is a fancy way to say that it handles distributing jobs to a cluster of computers. Overall I was impressed with it. The only weak point appears to be the scheduler where the default scheduler is naive and a more advanced one is proprietary only. And unfortunately I can't see anywhere that I could actually use this software, but it's a good one to keep in mind.

Miscellaneous Notes:

  • resource manager
  • pbs_mom - per-node daemon
  • pbs_server - master
  • qstat
  • pbs_sched - basic fifo scheduler
  • moab - commercial scheduler with more brains
  • set number of cpus per back-end
  • jobs can be wall time limited
  • dancer shell w/ public keys

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UTOSC 2010 Day 1: VMLB IP Load Balancer

First session of the day was about VMLB IP Load Balancer, presented by Clint Tinsley of Inductys. It's a formerly proprietary application whose development stopped in 2006. They're now looking to relaunch development and build it as Open Source. Overall sounds like an interesting project which could turn into something if the project works out. At this point it's not something I could actually use, unfortunately. I'll have to keep an eye on it.

Miscellaneous Notes:

  • project dormant since 2006
  • persistent connections to real server
  • designed for 2 interfaces
  • supports 4 interfaces
  • no vlan support
  • no snat support
  • mgmg ip separate from lb ip
  • layer 7 content type awareness
  • redundant controllers
  • support for ssl processor cards
  • http/https/ftp/imap/pop/ldap/smtp
  • roundrobin/weighted/least conn/src dst hash/expected delay/never queue
  • service checks
  • redhat/centos 3.0
  • uses ultra monkey - stopped dev in 2005 - or not?
  • snort built-in
  • built-in help system
  • und.cgi - management web app
  • ssl proxy for back-end http
  • real-time monitoring is missing
  • code release next week
  • source going in github (ossvmlb)
  • release on sourceforge
  • custom health checks? does basic alive (ping?). adding new ones might be hard.

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