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Packet loss at backbone

SOLVED
Posted by
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Member Since: ‎05-05-2013
Posts: 8
Message 1 of 4 (950 Views)

Packet loss at backbone

I have a dedicated server located in Chicago, and it seems a lot of people on the east coast are experiencing tremendous lag and packet loss to our server.  I ran a pingplot last night and determind it was located at 173.167.57.126 (as4436.350ecermak.il.ibone.comcast.net).  I woke up to a couple hundred users upset that they are still having issues on our server, so I ran another test and the exact same result is showing up, a full 18 hours later.

 

Here is a screenshot of the packet loss over the last 30 minutes from my home outside of Boston, to the server in Chicago.  These results are consistent to those I took last night, over the course of an hour.

 

http://i.imgur.com/kBEQQxH.png

1 ACCEPTED SOLUTION
Posted by
Bronze Problem Solver

Member Since: ‎05-12-2006
Posts: 3,364
Message 4 of 4 (911 Views)

Re: Packet loss at backbone


rannmann wrote:

I have a dedicated server located in Chicago, and it seems a lot of people on the east coast are experiencing tremendous lag and packet loss to our server.  I ran a pingplot last night and determind it was located at 173.167.57.126 (as4436.350ecermak.il.ibone.comcast.net).  I woke up to a couple hundred users upset that they are still having issues on our server, so I ran another test and the exact same result is showing up, a full 18 hours later.

 

Here is a screenshot of the packet loss over the last 30 minutes from my home outside of Boston, to the server in Chicago.  These results are consistent to those I took last night, over the course of an hour.

 

http://i.imgur.com/kBEQQxH.png


That doesn't show what you think it shows. It looks like Pingplotter did a bunch of traceroutes to the destination address, and if that's the case, your data show that there were *no* "lost packets" when the packet had a high enough TTL to reach the destination site. To understand what such tools are showing you, you should do some research on exactly how traceroute works. In this case the router at 173.167.57.126 didn't "lose" any packets, it just didn't respond with the TTL_Exceeded message that traceroute relies on for some of the packets. Sending those TTL_Exceeded responses is a low priority for a router, and whether or not a router sends those responses has nothing to do with whether or not it's doing its basic job of sending packets along.

 

Same is true if Pingplotter was sending a bunch of pings to the hops it discovered via doing a traceroute. Responding to pings has a low priority.

 

A very high response time could indicate a problem, but the lack of a response doesn't really mean anything... especially when, as is the case here, the subsequent hops indicate no problem.

3 REPLIES
Posted by
Edited on
‎05-06-2013 11:31 AM

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Member Since: ‎05-05-2013
Posts: 8
Message 2 of 4 (911 Views)

Re: Packet loss at backbone

[ Edited ]

-

Posted by
Edited on
‎05-05-2013 07:25 PM

Cable Expert

Member Since: ‎03-02-2007
Posts: 17,040
Message 3 of 4 (908 Views)

Re: Packet loss at backbone

[ Edited ]

You should be posting on the Comcast business class forum here.  The business forum has Comcast employees answering questions, where this forum is a user to user forum for residential service without much help from Comcast employees and nothing about business class service.

 

 

Posted by
Bronze Problem Solver

Member Since: ‎05-12-2006
Posts: 3,364
Message 4 of 4 (912 Views)

Re: Packet loss at backbone


rannmann wrote:

I have a dedicated server located in Chicago, and it seems a lot of people on the east coast are experiencing tremendous lag and packet loss to our server.  I ran a pingplot last night and determind it was located at 173.167.57.126 (as4436.350ecermak.il.ibone.comcast.net).  I woke up to a couple hundred users upset that they are still having issues on our server, so I ran another test and the exact same result is showing up, a full 18 hours later.

 

Here is a screenshot of the packet loss over the last 30 minutes from my home outside of Boston, to the server in Chicago.  These results are consistent to those I took last night, over the course of an hour.

 

http://i.imgur.com/kBEQQxH.png


That doesn't show what you think it shows. It looks like Pingplotter did a bunch of traceroutes to the destination address, and if that's the case, your data show that there were *no* "lost packets" when the packet had a high enough TTL to reach the destination site. To understand what such tools are showing you, you should do some research on exactly how traceroute works. In this case the router at 173.167.57.126 didn't "lose" any packets, it just didn't respond with the TTL_Exceeded message that traceroute relies on for some of the packets. Sending those TTL_Exceeded responses is a low priority for a router, and whether or not a router sends those responses has nothing to do with whether or not it's doing its basic job of sending packets along.

 

Same is true if Pingplotter was sending a bunch of pings to the hops it discovered via doing a traceroute. Responding to pings has a low priority.

 

A very high response time could indicate a problem, but the lack of a response doesn't really mean anything... especially when, as is the case here, the subsequent hops indicate no problem.