IPv6 end user addressing

Owen DeLong owen at delong.com
Tue Aug 9 07:25:52 UTC 2011


It's at least true of how some of the Cisco platforms cope with IPv6 access lists.

Owen

On Aug 8, 2011, at 11:54 PM, Joel Jaeggli wrote:

> 
> On Aug 8, 2011, at 5:14 PM, Owen DeLong wrote:
> 
>> I'm sure there will be platforms that end up on both sides of this question.
> 
> I know of no asic in a switch that claims to support ipv6 that does it this way... That would tend to place you at a competitive disadvantage to broadcom/marvell/fulcrum/juniper/cisco if you implemented it that way... it's easier I imagine to simply reduce the size of the fib...
> 
> given that switches routinely have to forward to neighbors on /126 or /127 prefix links I think that would be something of a mistake.
> 
>> YES: We made a less expensive box by cutting the width of the TCAM required in half
> 
>> NO: We spared no expense and passed the costs (and a nice profit margin) on to you so
>> 	that you can do whatever you like in IPv6 at wire speed.
>> 
>> I'm sure the market will chose products from both sides of the line for the same reasons.
>> 
>> Owen
>> 
>> On Aug 8, 2011, at 4:34 PM, Randy Carpenter wrote:
>> 
>>> 
>>> 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
>>>> =========================================================================
>>>> Address: Koloniestrasse 34         VAT Tax ID:      DE267268209
>>>>        D-13359                   Registration:    HRA 42834 B
>>>>        BERLIN                    Phone:
>>>>                  +31/(0)87-8747479
>>>>        Germany                   GSM:
>>>>                    +49/(0)152-26410799
>>>> RIPE:    CBSK1-RIPE                e-Mail:          sven at cb3rob.net
>>>> =========================================================================
>>>> <penpen> C3P0, der elektrische Westerwelle
>>>> http://www.facebook.com/cb3rob
>>>> =========================================================================
>>>> 
>>>> Confidential: Please be advised that the information contained in
>>>> this
>>>> email message, including all attached documents or files, is
>>>> privileged
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>>>> copying of this communication is strictly prohibited.
>>>> 
>>>> 
>>>> 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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