follow-on of maintenance survey

Zhen Wu zwu at
Thu Oct 7 22:26:52 UTC 2004

Several hours ago, I post a survey request on the list. First, if it 
disturb some people, please accept my sincere apology.

Second, I'd like to summarize the responses, because I think it might 
be interesting to some people. I got about 30 responses, which is not a 
big size. Most people said that they do the planned maintenance during 
weekday midnight. Two reasons for this. First, it's the time window 
that will cause the least interference of network usage; Second, it's a 
better time to get hold of other people (customers, vendors) than 
weekend if necessary. For some small or critical problems, people just 
fix it immediately. Some people also mentioned that they would like to 
major maintenance during weekend.

Third, I will explain our research (routing instability) and 
hypothesis, which motivate this email survey. Your sharing of insight 
will be very helpful and appreciated. Because it's pretty long, I put 
the description in the end.

Finally, we still warmly welcome your survey response. Thanks!


In the academic research society, some people argue that there is 
correlation between network usage and Internet routing instability (of 

A research done in 1996 revealed daily and weekly routing instability 
pattern. During the day time Internet exhibits significantly higher 
instability, while in the midnight we see much less instability 
activity. Similarly, during weekend there are much less routing 

We revisited this study, because we believe Internet has changed a lot 
since 1996. We use data from public BGP archives like Oregon 
RouteViews. Our new results still display pretty strong daily pattern, 
with higher instabilities during 6AM and 6PM (PST). However, we observe 
less obvious weekly pattern compared to 1996. Our visual comparisons 
are also confirmed by more rigorous statistics method: spectrum 
analysis (using Fourier Transform).

Meanwhile, Internet traffic still display strong weekly and diurnal 
patterns. So if we believe the correlation between network usage and 
routing instability, why we didn't see less instability during weekend?

That's why I send out previous survey email to see whether people do a 
lot of maintenance during weekend, which might contribute to some of 
the instabilities observed during weekend. From current survey, my 
hypothesis seems not to be true.

Any discussion, insight, or critique are extremely welcomed!

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