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Re: The Big Squeeze

  • From: Tony Barber
  • Date: Tue Mar 04 04:07:32 1997

Paul Ferguson wrote:
>
>At 10:30 PM 3/3/97 -0600, Sean Donelan wrote:
>
>>>From a single data point on my router, /24's currently account for 64% of
>>the routing table entries and for 65% of the flapping prefixes.  /16's
>>account for 12% of the routing table entries, and 10% of the flapping
>>prefixes.  It doesn't appear to me there is a significant difference
>>between flap behaivor of long prefixes and short prefixes.  There are
>>more long prefixes than short prefixes.  But as a group they both tend
>>to flap the same proportion of 2% of the routes within the group.
>
>Sorry, I'm not convinced this is the case. There is not enough
>empirical evidence.
>

To back Paul up here..
Tests we have run would indicate that this is not _generally_ the case.
I guess it depends on your point of viewing but we certainly see an
inordinate amount of oscillation in the longer prefix ranges.
(It also depends on the parameters you associate with certain prefixes of 
course ;-)
(Sorry - no facts and figures to back that up)

For instance, take this snapshot and note the /24 from within the 153.96 
network.  The flap column is the interesting one compared with other class Bs.
This is not representative but gives a flavour of what we have been seeing.

They are all from the same originator and it would not take a great amount 
of effort to apply a null0 tie down !


   Network          From            Flaps Duration Reuse    Path

*> 143.222.116.0/24 146.188.31.193  4     01:21:32          702 701 3407 
*d 146.1.0.0        146.188.31.193  10    00:32:21 00:23:20 702 701 3561 6196 6066 
 h 146.103.0.0      146.188.31.193  4     00:17:40          702 701 701 1239 4004 2611 
*> 147.110.0.0      146.188.31.193  2     00:19:12          702 701 1280 2914 2905 
*d 149.209.0.0      146.188.31.193  4     00:02:28 00:28:30 702 701 1800 1755 1273 5539 5430 
*  150.61.0.0       146.188.31.193  1     00:00:26          702 701 3561 2521 4678 
 h 153.96.11.0/24   146.188.31.193  11    02:34:44          702 701 701 1800 1755 517 5501 
 h 153.96.96.0/22   146.188.31.193  12    02:34:44          702 701 701 1800 1755 517 5501 
 h 153.96.101.0/24  146.188.31.193  11    02:34:44          702 701 701 1800 1755 517 5501 
 h 153.96.104.0/22  146.188.31.193  12    02:34:44          702 701 701 1800 1755 517 5501 
 h 153.96.110.0/24  146.188.31.193  11    02:34:44          702 701 701 1800 1755 517 5501 
 h 153.96.120.0/23  146.188.31.193  12    02:34:44          702 701 701 1800 1755 517 5501 
 h 153.96.149.0/24  146.188.31.193  11    02:34:44          702 701 701 1800 1755 517 5501 
 h 153.96.176.0/22  146.188.31.193  12    02:34:44          702 701 701 1800 1755 517 5501 
 h 153.96.236.0/22  146.188.31.193  12    02:34:51          702 701 701 1800 1755 517 5501 
 h 153.96.243.0/24  146.188.31.193  11    02:34:51          702 701 701 1800 1755 517 5501 
*> 155.141.0.0      146.188.31.193  3     00:14:46          702 701 1800 668 
*> 155.148.0.0      146.188.31.193  3     00:14:46          702 701 1800 668 
*> 156.6.0.0        146.188.31.193  3     00:14:48          702 701 1800 668 
*> 156.36.0.0       146.188.31.193  2     00:19:21          702 701 1280 2914 

--Tony       
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