Topic 'DNS issues.' in forum 'Comcast HSI' - dslreports.com

Re: DNS issues.

Tue, 22 Jan 2013 20:06:18 EDT

bradyr posted : When I mentioned that comcast dns servers do ICMP rate limiting, that means that they may not respond to ping requests and may also show timeout blips on traceroutes.

again, try using dig or nslookup to verify if you are having DNS issues.

traceroute and ping blips to 75.75.75.75 or 75.75.76.76 prove absolutely nothing due to their ICMP rate limiting. I will get the same "packet loss" that you do and I can guarantee you that my internet connection is having zero issues.

Edit: In case anyone was wondering what a typical dig response at 75.75.75.75 would look like:

ryan@skynet:~$ dig @75.75.75.75 google.com ; <<>> DiG 9.8.1-P1 <<>> @75.75.75.75 google.com; (1 server found);; global options: +cmd;; Got answer:;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 10620;; flags: qr rd ra; QUERY: 1, ANSWER: 11, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION:;google.com.                    IN      A ;; ANSWER SECTION:google.com.             211     IN      A       74.125.224.39google.com.             211     IN      A       74.125.224.37google.com.             211     IN      A       74.125.224.32google.com.             211     IN      A       74.125.224.34google.com.             211     IN      A       74.125.224.33google.com.             211     IN      A       74.125.224.46google.com.             211     IN      A       74.125.224.41google.com.             211     IN      A       74.125.224.36google.com.             211     IN      A       74.125.224.40google.com.             211     IN      A       74.125.224.35google.com.             211     IN      A       74.125.224.38 ;; Query time: 19 msec;; SERVER: 75.75.75.75#53(75.75.75.75);; WHEN: Tue Jan 22 17:16:18 2013;; MSG SIZE  rcvd: 204

and here's a nslookup against 75.75.75.75:

ryan@skynet:~$ nslookup google.com 75.75.75.75Server:         75.75.75.75Address:        75.75.75.75#53 Non-authoritative answer:Name:   google.comAddress: 74.125.224.39Name:   google.comAddress: 74.125.224.37Name:   google.comAddress: 74.125.224.32Name:   google.comAddress: 74.125.224.34Name:   google.comAddress: 74.125.224.33Name:   google.comAddress: 74.125.224.46Name:   google.comAddress: 74.125.224.41Name:   google.comAddress: 74.125.224.36Name:   google.comAddress: 74.125.224.40Name:   google.comAddress: 74.125.224.35Name:   google.comAddress: 74.125.224.38

Re: DNS issues.

Tue, 22 Jan 2013 20:06:14 EDT

pflog posted :

said by thataboi:

Typical dslreports critcism. Well did you use a dsnlookup tool?? Wow really? What is a dsntool going to tell me that I don't already know hen I am sitting in front of a screen with half the internet loading text?? So I did a simple tracert to the server as this was happening and it ended with packet loss. So are you going to insult me some more?

8 14 ms * 15 ms cdns01.comcast.net [75.75.75.75]

latency (typically gauged by a ping or traceroute) to a server that rate limits or drops ICMP and even udp traceroute packets is not a good way to check the response time of a DNS server.

The actual time it takes for a response is:

RTT (latency)
+
Lookup time (which may involve querying authoritative servers, or doing a recursive lookup, etc)

So even if a DNS server didn't rate limit ICMP, ping alone will not tell you the whole story.
--
"I drank what?" -Socrates

Re: DNS issues.

Tue, 22 Jan 2013 19:56:37 EDT

thataboi posted : Typical dslreports critcism. Well did you use a dsnlookup tool?? Wow really? What is a dsntool going to tell me that I don't already know hen I am sitting in front of a screen with half the internet loading text?? So I did a simple tracert to the server as this was happening and it ended with packet loss. So are you going to insult me some more?

8 14 ms * 15 ms cdns01.comcast.net [75.75.75.75]

Re: DNS issues.

Tue, 22 Jan 2013 16:38:14 EDT

egeek84 posted : LOL!!!!!!!

Re: DNS issues.

Tue, 22 Jan 2013 13:58:11 EDT

JigglyWiggly posted : If you want to test dns
use dnsbenchmark
»www.grc.com/dns/benchmark.htm

Re: DNS issues.

Tue, 22 Jan 2013 08:26:58 EDT

jlivingood posted :

said by bradyr:

Delayed ninja edit: Comcast most likely rate-limits ICMP packets on their dns servers. ping and traceroute are not the best way to judge DNS server performance. use tools like nslookup and dig to see how your dns performance is.

In response to the delayed ninja edit... Ninja bonus points for correctness and style. Bonus 2 throwing stars.

--
JL
Comcast

Re: DNS issues.

Tue, 22 Jan 2013 06:34:56 EDT

RR Conductor posted : I haven't seen any problems up here in Northwestern California (Mendocino County).
--

Re: DNS issues.

Tue, 22 Jan 2013 00:29:12 EDT

bradyr posted : 75.75.75.75 and 75.75.76.76 crappy? just because they aren't responding to pings means they are crappy, I forward to 75.75.75.75 since i'm on the west coast and i've had zero problems with DNS resolution. very snappy on every lookup.

Delayed ninja edit: Comcast most likely rate-limits ICMP packets on their dns servers. ping and traceroute are not the best way to judge DNS server performance. use tools like nslookup and dig to see how your dns performance is. I choose comcast's servers because they are only a couple hops from me and they perform lookups just as fast as google's dns servers.

DNS issues.

Tue, 22 Jan 2013 00:20:56 EDT

thataboi posted : Anyone else out West coast having Comcast DNS issues? Sometimes regular common websites such as google.com won't even load or load only text. I then run tracert and pings etc and find that 75.75.75.75 and 75.75.76.76 I are having packet loss. Anybody know of other dns servers out here we can use besides these two crappy ones and without compromising dnssec??