IPv6 end user addressing

Randy Carpenter rcarpen at network1.net
Mon Aug 8 18:34:50 CDT 2011


I heard at one time that hardware manufacturers were likely to route in hardware only down to a /64, and that any smaller subnets would be subject to the "slow path" as ASICs were being designed with 64-bit address tables. I have no idea of the validity of that claim. Does anyone have any concrete evidence for or against this argument?

If true, it would make /64s even more attractive.

-Randy


----- Original Message -----
> we assign /112 per "end user vlan (or server)" at this moment...
> works
> perfectly fine (and thats even "a bit too big").
> 
> - nobody wants to use dynamic ips on -servers- or -router links-
> anyway
> 
> i -really- can't see why people don't just use subnets with just the
> required number of addresses.
> 
> take one /64 (for /64's sake ;), split it up into subnets which each
> have
> the required number of addresses (lets say you have 2-4 addresses for
> each
> bgp/router link, so you simply split it up into subnets that size)
> 
> etc.
> 
> no need to use /64 for -everything- at all, just because it fits
> (ethernet) mac addresses (as if ethernet will be around longer than
> ipv6
> ha-ha, someone will come up with something faster tomorrow and then
> its
> bye bye ethernet, the 10ge variant is getting slow, and the 100ge
> variant
> is not even standardized yet, and trunking is a bottleneck ;)
> 
> we don't use /24's for -everything- on ipv4 now do we :P
> 
> (oh wait, there once was a time where we did.. due to another
> retarded
> semi-automatic configuration thingy, called RIP , which also only
> seemed
> to understand /24 or bigger ;)
> 
> --
> Greetings,
> 
> Sven Olaf Kamphuis,
> CB3ROB Ltd. & Co. KG
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> 
> On Mon, 8 Aug 2011, Owen DeLong wrote:
> 
> >
> > On Aug 7, 2011, at 4:26 PM, Jeff Wheeler wrote:
> >
> >> On Sun, Aug 7, 2011 at 6:58 PM, Mark Andrews <marka at isc.org>
> >> wrote:
> >>> So you want HE to force all their clients to renumber.
> >>
> >> No.  I am simply pointing out that Owen exaggerated when he stated
> >> that he implements the following three practices together on his
> >> own
> >> networks:
> >> * hierarchical addressing
> >> * nibble-aligned addressing
> >> * /48 per access customer
> >>
> >> You can simply read the last few messages in this thread to learn
> >> that
> >> his recommendations on this list are not even practical for his
> >> network today, because as Owen himself says, they are not yet able
> >> to
> >> obtain additional RIR allocations.  HE certainly operates a
> >> useful,
> >> high-profile tunnel-broker service which is IMO a very great asset
> >> to
> >> the Internet at-large; but if you spend a few minutes looking at
> >> the
> >> publicly available statistics on this service, they average only
> >> around 10,000 active tunnels across all their tunnel termination
> >> boxes
> >> combined.  They have not implemented the policies recommended by
> >> Owen
> >> because, as he states, a /32 is not enough.
> >>
> >> Do I think the position he advocates will cause the eventual
> >> exhaustion of IPv6?  Well, let's do an exercise:
> >>
> >> There has been some rather simplistic arithmetic posted today,
> >> 300m
> >> new subnets per year, etc. with zero consideration of
> >> address/subnet
> >> utilization efficiency within ISP networks and individual
> >> aggregation
> >> router pools.  That is foolish.  We can all pull out a calculator
> >> and
> >> figure that 2000::/3 has space for 35 trillion /48 networks.  That
> >> isn't how they will be assigned or routed.
> >>
> >> The effect of 2011-3 is that an out-sized ISP like AT&T has every
> >> justification for deciding to allocate 24 bits worth of subnet ID
> >> for
> >> their "largest POP," say, one that happens to terminate layer-3
> >> services for all customers in an entire state.  They then have
> >> policy
> >> support for allocating the same sized subnet for every other POP,
> >> no
> >> matter how small.  After all, the RIR policy permits them to
> >> obtain
> >> additional allocations as soon as one POP subnet has become full.
> >>
> >> So now you have a huge ISP with a few huge POPs, and a lot of
> >> small
> >> ones, justified in assigning the same size aggregate prefix,
> >> suitable
> >> for 2^24 subnets, to all those small POPs as well.  How many
> >> layer-3
> >> POPs might this huge ISP have?  Any number.  It could be every
> >> central
> >> office with some kind of layer-3 customer aggregation router.  It
> >> could even be every road-side hut for FTTH services.  Perhaps they
> >> will decide to address ten thousand POPs this way.
> >>
> >> Now the nibble-aligned language in the policy permits them to
> >> round up
> >> from 10,000 POPs to 16 bits worth of address space for "POP ID."
> >>  So
> >> AT&T is quite justified in requesting:
> >>    48 (customer subnet length) - 24 (largest POP subnet ID size) -
> >>    16
> >> (POP ID) == a /8 subnet for themselves.
> >>
> > Right up until you read:
> >
> > 6.5.3 (d):
> > If an LIR has already reached a /12 or more, ARIN will
> > allocate a single additional /12 rather than continue
> > expanding nibble boundaries.
> > As you can see, there is a safety valve in the policy at /12 for
> > just
> > this reason.
> >
> >
> >> Now you can see how this policy, and addressing scheme, is utterly
> >> brain-dead.  It really does put you (and me, and everyone else) in
> >> real danger of exhausting the IPv6 address space.  All it takes is
> >> a
> >> few out-sized ISPs, with one large POP each and a bunch of smaller
> >> ones, applying for the maximum amount of address space permitted
> >> them
> >> under 2011-3.
> >>
> >
> > Even by your calculations, it would take 256 such outsized ISPs
> > without
> > a safety valve. With the safety valve that is built into the policy
> > at /12,
> > it would take 4,096 such ISPs. I do not believe that there are more
> > than
> > about 20 such ISPs world wide at this time and would put the
> > foreseeable
> > likely maximum at less than 100 due to the need for customers to
> > support
> > such outsized ISPs and the limited base that would have to be
> > divided
> > among them.
> >
> > Owen
> >
> >
> 
> 
> 




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