swinog July 2009

swinog@lists.swinog.ch

47 participants
26 discussions

Google Safe Browsing vs DNS TCP reply
by Guy Baconniere 09 Jul '09

09 Jul '09

Hello, safebrowsing-cache.google.com is checked from both Google Toolbar included by default in Firefox 3 and on Google Chrome Navigator. Google Toolbar is also available on IE, etc. When the query reaches the DNS of the ISP it will reply with a DNS TCP reply if minimal-responses is no (default on Bind9) or with a small UDP DSN reply if minimal-responses is yes. I recommend that all ISP use minimal-responses yes or equivalent on their DNS server. This will save bandwidth and avoid DNS TCP reply to be blocked in a Firewall in the path. Best Regards, Guy Baconniere http://www.divideandconquer.se/2009/06/25/firefox-30-freezes-waiting-to-res… Add “minimal-responses yes;” in your bind9 configuration or ask your ISP to do so. /etc/bind/named.conf.options options { // … // only add records to the authority and additional data sections when required minimal-responses yes; }; By doing this Google’s safebrowsing-cache.google.com will fit in a standard UDP DNS packet otherwise with additional section it will be TCP DNS packet. check the result with or without minimal-responses of dig safebrowsing-cache.google.com With minimal-responses no (default on Bind9) IP (tos 0×0, ttl 64, id 40627, offset 0, flags [none], proto UDP (17), length 75) 127.0.0.1.49553 > 127.0.0.1.53: [bad udp cksum 6429!] 40815+ A? safebrowsing-cache.google.com. (47) IP (tos 0×0, ttl 64, id 40628, offset 0, flags [none], proto UDP (17), length 526) 127.0.0.1.53 > 127.0.0.1.49553: 40815| q: A? safebrowsing-cache.google.com. 25/2/0 safebrowsing-cache.google.com.[|domain] IP (tos 0×0, ttl 64, id 4337, offset 0, flags [DF], proto TCP (6), length 60) 127.0.0.1.57552 > 127.0.0.1.53: S, cksum 0×30e4 (correct), 272739230:272739230(0) win 32792 IP (tos 0×0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 60) 127.0.0.1.53 > 127.0.0.1.57552: S, cksum 0×6453 (correct), 281541131:281541131(0) ack 272739231 win 32768 IP (tos 0×0, ttl 64, id 4338, offset 0, flags [DF], proto TCP (6), length 52) 127.0.0.1.57552 > 127.0.0.1.53: ., cksum 0×4b76 (correct), 1:1(0) ack 1 win 513 IP (tos 0×0, ttl 64, id 4339, offset 0, flags [DF], proto TCP (6), length 101) 127.0.0.1.57552 > 127.0.0.1.53: P 1:50(49) ack 1 win 513 5198+[|domain] IP (tos 0×0, ttl 64, id 16739, offset 0, flags [DF], proto TCP (6), length 52) 127.0.0.1.53 > 127.0.0.1.57552: ., cksum 0×4b46 (correct), 1:1(0) ack 50 win 512 14:44:32.883449 IP (tos 0×0, ttl 64, id 16740, offset 0, flags [DF], proto TCP (6), length 632) 127.0.0.1.53 > 127.0.0.1.57552: P 1:581(580) ack 50 win 512 5198 q:[|domain] IP (tos 0×0, ttl 64, id 4340, offset 0, flags [DF], proto TCP (6), length 52) 127.0.0.1.57552 > 127.0.0.1.53: ., cksum 0×48ef (correct), 50:50(0) ack 581 win 531 IP (tos 0×0, ttl 64, id 4341, offset 0, flags [DF], proto TCP (6), length 52) 127.0.0.1.57552 > 127.0.0.1.53: F, cksum 0×48ee (correct), 50:50(0) ack 581 win 531 IP (tos 0×0, ttl 64, id 16741, offset 0, flags [DF], proto TCP (6), length 52) 127.0.0.1.53 > 127.0.0.1.57552: F, cksum 0×4900 (correct), 581:581(0) ack 51 win 512 IP (tos 0×0, ttl 64, id 4342, offset 0, flags [DF], proto TCP (6), length 52) 127.0.0.1.57552 > 127.0.0.1.53: ., cksum 0×48ed (correct), 51:51(0) ack 582 win 531 With minimal-responses yes IP (tos 0×0, ttl 64, id 40623, offset 0, flags [none], proto UDP (17), length 75) 127.0.0.1.40215 > 127.0.0.1.53: [bad udp cksum 8a13!] 55747+ A? safebrowsing-cache.google.com. (47) IP (tos 0×0, ttl 64, id 40624, offset 0, flags [none], proto UDP (17), length 494) 127.0.0.1.53 > 127.0.0.1.40215: 55747 q: A? safebrowsing-cache.google.com. 25/0/0 safebrowsing-cache.google.com.[|domain] Best Regards, Guy Baconniere

3 4

Bluewin MX caching problem
by Mathias Schrem 08 Jul '09

08 Jul '09

Hi everybody Can a Bluewin postmaster contact me off-list please? Cheers Mathias

1 0

looking for dslam
by Reza Kordi 07 Jul '09

07 Jul '09

Hi Guys I am looking for a DSLAM with a small footprint that is supported and tested with Cisco cpe's appreciate any hints. Cheers, Reza

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OT: network connection 500 - 1000m
by Daniel Kamm 07 Jul '09

07 Jul '09

Dear networkers, I have an off-topic network problem, but some ppl here might help me. I need to build an IP network line from the middle of a construction site to an internet connection place for a one-time event. The distance is around 500 - 1000m. No line of sight and therefore directed WLAN will not work without several relays. At the moment I'm thinking of using a copper line and some old fashioned 1MBit lease line modems. Do you have other ideas of getting this to work or may have any parts which you can lend? The event will happen at the end of July on a single week day. Thank you for your help. Cheerz, - Dan

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ID4214468 C-A-N-A-D-l-A-N P-H-A-R-M-A-C-Y
by swinog-list 06 Jul '09

06 Jul '09

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Request for school presentation on "the internet"
by Norbert Bollow 02 Jul '09

02 Jul '09

Hi, my 13 year old son will be giving a talk tomorrow in school about "the internet". He has decided to focus in the talk on the technical side, like fundamental principles of how DNS resolution works. He has asked me if I could help him find some datacenter-type equipment that he can show off to the other students in his class. For example some rackmount device and a bit of optical fibre, if possible. There is no need for the stuff to be in working order. Since the talk is tomorrow, we'd need to pick the stuff up today in the afternoon or evening; I'd be happy to do this anywhere is the Zurich or Zurich highlands (Zürcher Oberland) area. We'll bring it back tomorrow in the afternoon after the talk. We'd be very grateful if someone would help us with this! Greetings, Norbert

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swinog July 2009