Monthly Archives: September 2011

29 Sep

Completed IPv6 Certification from Hurricane Electric

Just now completed IPv6 certification with Hurricane Electric. It was very much fun!

 

IPv6 Certification Badge for anuragbhatia

 

 

Starting was pretty much simple and basic, followed by email server running on v6 – which also I was doing already. I was stuck at most unexpected part – when I had to setup IPv6 based DNS servers. My first reaction was – that’s so simple….later on realized that system was just not accepting my entry and kept on giving error with AAAA records. Then suddenly I realized that I missed creating AAAA at DNS servers, but created only glue records which was causing issue. Created AAAA and that also went smoothly + glue helped me in final test too.

 

So finally I am an IPv6 expert now! 🙂

 

 

 

 

26 Sep

openDNS performing better in India now!

Hello everyone!

 

Seems like Tata Communications routing table is changed (call it fixed) to route traffic for openDNS to Singapore. It’s not going to London anymore and I see very good latency from BSNL too (which uses Tata Comm for most of it’s International traffic).

 

Here’s latest routing from BSNL to openDNS: 

 

HOST: laptop                                                                 Loss%   Snt   Last   Avg  Best  Wrst StDev
  1. router2                                                                        0.0%    50    2.0   1.7   1.5   2.2   0.2
  2. 117.207.48.1                                                             2.0%    50   25.4  26.2  24.5  36.1   1.6
  3. 218.248.173.38                                                        0.0%    50   26.1  31.2  25.0 125.5  17.8
  4. 121.244.68.114.static-lvsb.vsnl.net.in               2.0%    50   70.1  72.2  69.4  97.8   6.0
  5. 172.31.61.210                                                            0.0%    50   92.9  94.8  92.9 109.0   2.2
  6. ix-4-2.tcore1.CXR-Chennai.as6453.net            0.0%    50   94.3  98.4  93.1 154.6  12.6
  7. if-5-2.tcore1.SVW-Singapore.as6453.net          0.0%    50  127.2 130.6 125.8 165.5   8.5
  8. if-2-2.tcore2.SVW-Singapore.as6453.net         0.0%    50  126.8 128.6 124.4 178.2   8.3
  9. Vlan1807.icore1.SVQ-Singapore.as6453.net   2.0%    50  135.4 132.3 126.1 140.4   4.4
 10. 203.208.186.101                                                      0.0%    50  202.4 163.6 156.9 256.5  17.5
 11. 203.208.153.110                                                       0.0%    50  159.1 166.8 157.0 272.4  23.6
 12. 203.208.190.166                                                      2.0%    50  160.3 160.6 158.6 191.9   4.6
 13. resolver1.opendns.com                                           2.0%    50  159.0 158.3 156.9 162.4   1.0

 

Overall I am getting latency from 160ms which seems OK considering 25-30ms latency for DSL, adding 60-90ms for route till South India followed by 30-40ms latency between Chennai and Singapore and eventually destination openDNS node on ASN 36692. 

 

Oh and btw I was lucky enough to meet DNS godfather David Ulevitch at openDNS HQ in San Francisco during last US trip. A very impressive personality!

 

Well that’s all for now. Will be posting a couple more updates soon. Have a good week ahead!

07 Sep

Dots in a hostname

Yesterday I had a very interesting discussion with our senior administrator.

I was configuring reverse DNS records for our /24 block and I decided to use format – IP.static.domain.com

thus if for IP 1.2.3.4, I pointed reverse DNS (PTR) to 1.2.3.4.static.domain.com

 

When I got chance to show my work to my senior administrator, he said – It’s wrong to use 1.2.3.4.static.domain.com in a hostname. Too many dots will make DNS resolution very slow (forward – reverse – again forward). And I should have used 1-2-3-4.static.domain.com

 

A very interesting point (and indeed a confusion!)

 

At first instance I was totally stunned myself and was thinking same as he said. He is senior admin and knows over a million more things then me and such feelings usually pushes you in case when you believe in someone without checking on facts.

(Disclaimer: No offence to my senior admin. He is a very smart person, and a good friend too).

 

After a while, I gave it a DEEP thought and discussed with a couple of more friends. I got clear idea about it. 

 

Let’s understand how 1.2.3.4.static.domain.com will be resolved. 

Here, first of all dns resolver will query com (root) servers for getting NS delegation of domain.com. Now as domain.com will reply with some NS (let’s call them ns1 & ns2). Next, DNS resolver will query ns1 for 1.2.3.4.static.domain.com and done – it will get back reply with A record – 1.2.3.4 (game over!).  🙂

Same thing happens even if we use 1-2-3-4.static.domain.com

 

So what “could have” caused slowdown?

There can be a significant slowdown IF for say in 1.2.3.4.static.domain.com

4.static.domain.com acts as a separate DNS zone rather then acting as nothing (when we create A record for 1.2.3.4.static.domain.com). If 4.static.domain.com has separate NS, and assume 3.4.static.domain.com is a further sub zone defined by some other NS …the one which are different then parent nameservers.

 But in our case 4.static.domain.com or 3.4.static.domain.com or 2.3.4.static.domain.com is just nothing. The only thing was 1.2.3.4.static.domain.com which was simply an A record on parent domain name.

Hence 1.2.3.4.static.domain.com is same as 1-2-3-4.static.domain.com and I assume it’s rather an issue of convention admins prefer rather then any technical reason behind it.

 

Oh and btw I am back at blogging!