[routing-wg] IPv6 Routing Recommendations

On 03/05/2010 08:39, "Randy Bush" <randy at psg.com> wrote:

>> I think, in order to come up with a normal figure, we need to
>> normalise the data as best we can. Taking the average number of
>> deaggregates per v4 allocation size should give us an idea of how much
>> people may want to deaggregate their v6 allocation (which in this
>> region is likely to be /32),
>> 
>> Am in full acceptance of the fact that some people deaggregate for
>> either other TE reasons (e.g high localpref and lack of community
>> support by expensive upstream) or no good reason at all (i.e ignorance
>> / assumptions about the way the internet works)
> 
> you may find an upcoming JSAC paper somewhat interesting
> 
>     http://archive.psg.com/jsac-deag.pdf

Interesting paper indeed. To sum this up for people who haven't read, the
conclusion states

 "According to our results, there is no trend towards more aggressive prefix
deaggregation or traffic engineering over time",
does this mean we shouldn't bother?

I did a quick check against the RIPE allocations file for created route
objects per allocation which are not the same size (i.e smaller) and
summarised based on the CIDR bits of the allocation, here are the results
for those that are interested:

Bits    Average (mean) Deaggs
------------------------
9:      16
10:     14
11:     24
12:     73
13:     43
14:     31
15:     40
16:     19
17:     19
18:     12
19:     8   <--- Modal average alloc size
20:     6
21:     3

Method was simply to query the database for each allocation and look for
smaller routes, take the mean and round down. As you can see, the mean is
skewed as the number of bits decreases (and the number of smaller bit
allocations is of course reduced due to the number of organisations able to
justify that size)

The modal average of allocation size is /19 according to the file (followed
closely by /20), I guess this tells me that, on average, people are
allocated /19s and when they deagg, they create on average 8 deaggregated
route objects... (so would likely do so in a uniform fashion with /37s)

What it certainly does say is that /36 would be too harsh a limit to impose
based on what people appear to be doing now, assuming the deaggs happen as a
result of sites (i.e multihoming)


Dave.



> 
> randy


------------------------------------------------
David Freedman 
Group Network Engineering
Claranet Limited
http://www.clara.net