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thataboi

join:2004-03-09
Springfield, OR
reply to jlivingood

Re: DNS issues.

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]



pflog
Bueller? Bueller?
Premium,MVM
join:2001-09-01
El Dorado Hills, CA
kudos:3

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


bradyr
Columbia College IT
Premium
join:2008-10-27
Sonora, CA

1 edit
reply to thataboi

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       74.125.224.39
google.com.             211     IN      A       74.125.224.37
google.com.             211     IN      A       74.125.224.32
google.com.             211     IN      A       74.125.224.34
google.com.             211     IN      A       74.125.224.33
google.com.             211     IN      A       74.125.224.46
google.com.             211     IN      A       74.125.224.41
google.com.             211     IN      A       74.125.224.36
google.com.             211     IN      A       74.125.224.40
google.com.             211     IN      A       74.125.224.35
google.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 75.75.75.75
Server:         75.75.75.75
Address:        75.75.75.75#53
 
Non-authoritative answer:
Name:   google.com
Address: 74.125.224.39
Name:   google.com
Address: 74.125.224.37
Name:   google.com
Address: 74.125.224.32
Name:   google.com
Address: 74.125.224.34
Name:   google.com
Address: 74.125.224.33
Name:   google.com
Address: 74.125.224.46
Name:   google.com
Address: 74.125.224.41
Name:   google.com
Address: 74.125.224.36
Name:   google.com
Address: 74.125.224.40
Name:   google.com
Address: 74.125.224.35
Name:   google.com
Address: 74.125.224.38