IPv6 Routing table will be bloated?

Owen DeLong owen at delong.com
Tue Oct 26 16:23:28 UTC 2010


On Oct 26, 2010, at 7:06 AM, TJ wrote:

> Quick comment:
> IGP bloat != BGP bloat.  Your customers cannot announce the space you gave
> them externally - unless ~/32s, i.e.  forced aggregation.
> 
He's talking about the bloat that comes from ISPs getting slow-started and then
only being able to increase their network in increments of 2x each time, so,
effectively ISP gets:

1	x	/32		Initial
Fills that up, gets
1	x	/32		First subsequent
Then
1	x	/31
then
1	x	/30
etc.

Probably not quite as bad as IPv4, but, potentially close.

> Also, your customers shouldn't need to come back for more very often and
> ideally you have some reservations for them a well :).
> 
Consider the scenario where you're dealing with an ISP that provides
services to other ISPs as his downstream customers and the above
statement doesn't hold true like you think it should.

Owen

> /TJ
> PS - apologies for top posting.
> On Oct 26, 2010 9:59 AM, "Jack Bates" <jbates at brightok.net> wrote:
>> So, the best that I can tell (still not through debating with RIR), the
>> IPv6 routing table will see lots of bloat. Here's my reasoning so far:
>> 
>> 1) RIR (ARIN in this case, don't know other RIR interpretations) only
>> does initial assignments to barely cover the minimum. If you need more
>> due to routing, you'll need to provide every pop, counts per pop, etc,
>> to show how v6 will require more than just the minimums (full routing
>> plan and customer counts to justify routing plan). HD-Ratio has NO
>> bearing on initial allocation, and while policy dictates that it doesn't
>> matter how an ISP assigns to customer so long as HD-Ratio is met, that
>> is not the case when providing justification for the initial allocation.
>> 
>> 2) Subsequent requests only double in size according to policy (so just
>> keep going back over and over since HD is met immediately due to the
>> minimalist initial assignment?)
>> 
>> So I conclude that since I get a bare minimum, I can only assign a bare
>> minimum. Since everything is quickly maxed out, I must request more (but
>> only double), which in turn I can assign, but my customer assignments
>> (Telcos/ISPs in this case) will be non-contiguous due to the limited
>> available space I have to hand out. This will lead to IGP bloat, and in
>> cases of multi-homed customers whom I provide address space for, BGP
> bloat.
>> 
>> I'm small, so my bloat factor is small, but I can quickly see this
>> developing exactly as my v4 network did (if it was years ago when I
>> first got my v4 allocation, growing to today, for each allocation I got
>> for v4, I'd expect similar out of v6). Sure, the end user gets loads of
>> space with those nice /48's, but the space within ISPs and their ISP
>> customers is force limited by initial allocations which will create
>> fragmentation of address space. This is brought about due to the dual
>> standard of initial vs subsequent allocations (just enough to cover
>> existing vs HD Ratio).
>> 
>> As an example, Using HD-Ratios as an initial assignment metric can
>> warrant a /27, whereas the minimalist approach may only warrant a
>> heavily utilized /30. 3 bits doesn't seem like much, but it's a huge
>> difference in growth room. Bare minimums, as provided by me, only
>> included the /24 IPv4 DHCP pools converted with a raw conversion as /32
>> IPv4 = /48 IPv6 network
>> 
>> Am I missing something, or is this minimalist approach going to cause
>> issues in BGP the same as v4 did?
>> 
>> 
>> Jack
>> 





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