Hi.
We had an interesting discussion the other day at work. We were speculating on how many DFZ IPv4 routes there would be at peak in the future before it starts to decline again due to less IPv4 usage. The current number is around 350k, and my personal estimation is that it would grow by at least 100k more due to the the last 5 /8s being carved up at around /22 meaning each /8 ending up with 16k routes, plus the last allocations being seen in the remaining RIR "normal allocations" would be smaller than before plus de-aggregation of space as people "sell" or "lease" subspace of their allocations.
My guess therefore is a peak around 450-500k IPv4 DFZ routes and that this would happen in around 3-5 years. I wanted to record this for posterity.
What is your guess, any why?
i am more of a pessimist. i suspect that there will be enough v4-only
destinations out there that multi-homed enterprises fronting onto
dual-stack backbones will announce teenie bits of v4 so they can nat64.
randy
Five million.
Assuming the /24 boundary holds (this is likely) and we're only
carrying global unicast and anycast routes (1. to 223. excluding
RFC1918, 127, etc) the theoretical maximum number of possible IPv4
prefixes is around 28M. (2**24)*0.8~=14M /24's. Plus 7M /23s, 4M
/22's, etc.
However, practical issues will prevent excessive numbers of fully
covered prefixes... So we won't generally see both /24's under a /23.
We might see a /24 and a covering /23 but if we do we won't generally
see the other /24. This drops us to an upper bound of 14M.
There will also be a significant number of prefixes where there's just
no gain from breaking them up. You're using the entire /20 at your
site and you only have one /24 that you want routed differently than
"normal." This will pull it down still further, cutting it somewhere
between half and a third of the 14M upper bound.
It'll take 10 to 20 years to get there. If we're actually able to
start retiring IPv4 in 10 years then it'll peak lower. But if IPv4
sticks around, I think the global IPv4 BGP table will reach a steady
state somewhere around 5 million prefixes.
Regards,
Bill Herrin
I think it'll end up around the same range, mostly due to hardware with built-in route limits. Some providers will be stuck with this for ~5-7 years due to equipment lifecycle depreciation.
- jared
You have ignored the probability of disaggregation due to IP trading markets, especially
given the wild-west nature of the APNIC transfer policy.
Many of the legacy blocks will get dramatically disaggregated in the likely market which
could take the DFZ well beyond 500k routes.
It will be very interesting to watch.
Owen
Strange, had this exact conversation with a boutique ISP owner I know
earlier today...
My hope is that things peak around 510k and that routers that can
handle about a million routes now can handle all of IPv4Peak and IPv6
growth for their economic lifetimes.
Disaggregation and leasing of space (or whatever) could easily spike
that significantly, but aren't likely to further increase the rate of
new announcements, merely how long we keep going with them.
I predict that we can't really predict this yet; IPv6 actual adoption
isn't far enough along to tell how bad that will end up being.
If it's five years before it dominates things, we're screwed on IPv4
tables. People who need smallish but routeable blocks will be able to
find them and pry them loose via enough funds and announce them. 5
more years of that, and current routers go "poof". Many go "poof"
sooner.
I'll take this one a little further.
I suspect that as we reach exhaustion, more people will be
forced to break space out of their provider's v4 aggregates, and
announce them, and an unfiltered DFZ may well approach the 'million'
entries some vendors now claim to support.
Conveniently, we've given them enough ASes to do so, with
four byte support. At least if our vendors get that working
correctly.
If we get there, or even close (anything beyond 0.5M), I
expect we'll see some of the native dual stack networks actually
acquire transport specifically for v6 and start running parallel
4/6 networks to deal with hardware forwarding limitations, particularly
those involving v6.
Of course, I'd really, really, really love to be wrong here.
It'd be great if v4 traffic fell off quickly enough people wouldn't
deagg for TE purposes, or v4 growth fell off, and a widespread
forwarding problem could be avoided.
--msa
No, I haven't ignored it. I'm just more optimistic about IPv6 deployment and that there will be a lot less de-aggregation due to trading than others are.
btw, this discussion should not forget that the load on routers is churn
and number of paths, not just prefix count.
randy
From: Randy Bush
Sent: Tuesday, March 08, 2011 7:44 PM
To: Mikael Abrahamsson
Cc: nanog@nanog.org
Subject: Re: estimation of number of DFZ IPv4 routes at peak in the
future
i am more of a pessimist. i suspect that there will be enough v4-only
destinations out there that multi-homed enterprises fronting onto
dual-stack backbones will announce teenie bits of v4 so they can
nat64.
randy
I suspect people will get varying experiences with that. That they will
attempt to multi-home with teenie bits of v4 I don't disagree with but
that teenie bit better be part of a larger aggregate that can reach at
least one of their runs home. There will likely be considerable
filtration once there is enough dual-stack pressure put on gear, and v6
being where the growth is it will get priority. Dual-homing to their
ISP might be a compromise solution seen more often with v4 in that
scenario.
i am more of a pessimist. i suspect that there will be enough
v4-only destinations out there that multi-homed enterprises fronting
onto dual-stack backbones will announce teenie bits of v4 so they can
nat64.
that teenie bit better be part of a larger aggregate that can reach at
least one of their runs home.
the last serious satainc phylters died in 2001. sales&marketing
pressure. when eyecandy.com is behind a /27, or your s&m folk
sell to weenie.foo who wants you to announce their /26, it will be
the end of the /24 barrier.
v6 being where the growth is it will get priority.
we wish. wanna start a pool on the growth of v6 announcements vs
new multi-homed v4 announcements?
randy
i am more of a pessimist. i suspect that there will be enough
v4-only destinations out there that multi-homed enterprises fronting
onto dual-stack backbones will announce teenie bits of v4 so they can
nat64.
that teenie bit better be part of a larger aggregate that can reach at
least one of their runs home.
the last serious satainc phylters died in 2001. sales&marketing
pressure. when eyecandy.com is behind a /27, or your s&m folk
sell to weenie.foo who wants you to announce their /26, it will be
the end of the /24 barrier.
v6 being where the growth is it will get priority.
we wish. wanna start a pool on the growth of v6 announcements vs
new multi-homed v4 announcements?
one of these curves is steeper than the other.
http://www.cidr-report.org/cgi-bin/plota?file=%2Fvar%2Fdata%2Fbgp%2Fv6%2Fas2.0%2Fbgp-active.txt&descr=Active%20BGP%20entries%20(FIB)&ylabel=Active%20BGP%20entries%20(FIB)&with=step
http://www.cidr-report.org/cgi-bin/plota?file=%2Fvar%2Fdata%2Fbgp%2Fas2.0%2Fbgp-active.txt&descr=Active%20BGP%20entries%20(FIB)&ylabel=Active%20BGP%20entries%20(FIB)&with=step
If the slope on the second stays within some reasonable bounds of it's
current trajactory then everything's cool, you buy new routers on
schedule and the world moves on. The first one however will eventually
kill us.
The long run is a misleading guide to current affairs. In the long run
we are all dead - John Maynard Keynes
one of these curves is steeper than the other.
AS2.0 BGP Table Statistics
AS2.0 BGP Table Statistics
hey geoff, would you put on same graph 
A valid comparison really needs to use the same vertical scale. That first is only 2300 new entries in the last 12 months. The other is 35000 new entries in the same period.
Antonio Querubin
e-mail/xmpp: tony@lava.net
one of these curves is steeper than the other.
That's what we wanted for the first one.
AS2.0 BGP Table Statistics
AS2.0 BGP Table Statistics
If the slope on the second stays within some reasonable bounds of it's
current trajactory then everything's cool, you buy new routers on
schedule and the world moves on. The first one however will eventually
kill us.
It won't, it will take an "S" shape eventually. Possibly around 120k prefixes, then it will follow the normal growth of the Internet as v4 did.
The long run is a misleading guide to current affairs. In the long run
we are all dead - John Maynard Keynes
randy
-as
This matches my personal view (and could be viewed as
"success" compared to the 5M estimate of Mr. Herrin...)
/John
one of these curves is steeper than the other.
AS2.0 BGP Table Statistics
http://www.cidr-report.org/cgi-bin/plota?file=%2Fvar%2Fdata%2Fbgp%2Fas2.0%2Fbgp-active.txt&descr=Active%20BGP%20entries%20(FIB)&ylabel=Active%20BGP%20entries%20(FIB)&with=step
If the slope on the second stays within some reasonable bounds of it's
current trajactory then everything's cool, you buy new routers on
schedule and the world moves on. The first one however will eventually
kill us.
A valid comparison really needs to use the same vertical scale. That
first is only 2300 new entries in the last 12 months. The other is
35000 new entries in the same period.
No it doesn't. I'm more concerned about the percentage rather than
absolute numbers and one of these things is doubling annually. I'll go
out on a limb and say I need 150k ipv6 routes in gear that's supposed to
last to 2016.
joel
the last serious satainc phylters died in 2001. sales&marketing
pressure. when eyecandy.com is behind a /27, or your s&m folk
sell to weenie.foo who wants you to announce their /26, it will be
the end of the /24 barrier.
Sure, you can sell to someone who wants to announce a /26 and you can
carry the route, but you can't force your peers or your peers' peers to
take it. That's what I meant by the experience possibly varying. It
might work, it might not from some locations.
> v6 being where the growth is it will get priority.
we wish. wanna start a pool on the growth of v6 announcements vs
new multi-homed v4 announcements?
I meant growth in traffic, not routing table. If traffic is growing on
v6 and a network with dual-stacked routers comes under routing table
pressure, v6 might win in the filtering decision.
I think it will grow a lot slower than IPv4 because with rational planning, few organizations should need to add more
prefixes annually, the way they had to in IPv4 due to scarcity based allocation policies.
Owen
...which was, ultimately, a large part of the point of going to 128
bits. The most important one for networks.