[clug] Um... Is there CLUG tonight?

Seamus clug at seamusmurray.com
Sun May 28 09:26:11 UTC 2017


Here are the sample traceroute outputs that I presented. 

Idealistic traceroute (for reference)

10 ms
20 ms
30 ms
40 ms
50 ms
60 ms
70 ms
80 ms
90 ms



Latency that the only present for some of the intermediary routers. Multiple potential causes, including..
Router control plane delays
1 or more long/slow return paths from 1 or more intermediary routers

10 ms  
20 ms  
30 ms  
200 ms  
210 ms  
220 ms  
230 ms  
240 ms  
90 ms  


Packet loss that the only present for some of the intermediary routers. Multiple potential causes, including..
Router control plane no generating the ICMP Time exceeded messages
1 or more return paths from 1 or more intermediary routers causing packet loss
    
10 ms  
20 ms  
30 ms  
*      
*      
*      
*      
80 ms  
90 ms  



In-line latency that continues all the way to the remote destination host

10 ms  
20 ms  
30 ms  
200 ms  
210 ms  
220 ms  
230 ms  
240 ms  
250 ms  


MPLS    ( I'll leave this for those who are interested to investigate them selves )
10 ms    
20 ms    
30 ms    
90 ms    
90 ms    
90 ms    
90 ms    
90 ms    
90 ms    


Multiple potential causes, including..
Firewall on the remote destination host    
Your local firewall/NAT dropping the returned traffic

10 ms  
20 ms  
30 ms  
*      
*      
*      
*      
*      
*      

CheersSeamus Murray      From: Bob Edwards via linux <linux at lists.samba.org>
 To: linux at lists.samba.org 
 Sent: Friday, 26 May 2017, 9:59
 Subject: Re: [clug] Um... Is there CLUG tonight?
   
On 26/05/17 07:28, Mike Carden via linux wrote:
> On Fri, May 26, 2017 at 6:29 AM, George at Clug via linux <
> linux at lists.samba.org> wrote:
>
>>    Well I missed another meeting.
>>
>> The days, weeks and months are travelling way too fast for me.
>>
>> Was it a good night, what was discussed ?
>>
>
> The bit I saw before I had to go and be a taxi was very good. Seamus was
> digging into traceroute and what it does and doesn't tell you about what an
> IP network is doing.
>
> I hope that the resources from his talk are online somewhere because I
> really wish I hadn't missed the rest.
>

+1 - Seamus did a great job and his animated diagrams of how traceroute
output can represent many different scenarios were excellent.

Alas, his "slides" (9000 images, apparently, and around 8GB) are not
yet ready to be put on the web.

A huge thanks to him for travelling all the way from Sydney just to
present this talk for us.

One interesting point, early on in his presentation, was around 7
very different traceroute outputs for the same (hypothetical)
destination that were all good and one that may have been good or
bad - this brought home his point quite well, I thought.

He mentioned to me, after dinner, that DigitalOcean and Linode both
have tutorials on traceroute that are worth a read, although the one
I found on DigitalOcean seemed to be making some opposite (and naive)
points to Seamus's talk. For example, Seamus talked down the use of
mtr (My TraceRoute), but the DigitalOcean tutorial talks it up, etc.

cheers,

Bob Edwards.

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