[arin-ppml] A challenge to the assumption that a big DFZ is a problem
warren at wholesaleinternet.com
Mon Dec 14 14:33:04 EST 2009
The routing table growing like crazy effectively forces providers to replace
critical pieces of hardware or find themselves out of business. There is
more to consider besides the cost of the router. There is man power,
down-time etc and depending on your particular circumstance, this can be
Furthermore, just because router manufacturers can throw in faster hardware
doesn't mean they'll do it for free or for incremental increase in cost. I
reckon the transition out of v4 to v6 is going to favor those with pockets
deep enough to absorb the conversion costs and/or the intermittent
transition costs. Consequently, the best thing the world can do to keep the
little guys up and going is agree upon policy that minimizes transition
From: arin-ppml-bounces at arin.net [mailto:arin-ppml-bounces at arin.net] On
Behalf Of Scott Leibrand
Sent: Monday, December 14, 2009 1:20 PM
To: arin-ppml at arin.net
Subject: Re: [arin-ppml] A challenge to the assumption that a big DFZ is a
Your analysis does apply, to some extent, to the lower end of the router
market. However, there are a number of higher-end routers (including pretty
much anything that's more than 2U high and has more than a handful of 10G
ports) where the limitation is in the custom TCAM used by the FIB. Moore's
law definitely applies there, but it's an entirely different architecture
than general-purpose CPUs.
That said, most newer hardware currently supports about a million IPv4
routes (or 1/4 as many IPv6 routes). For those of us who only have to carry
the DFZ table, that means we'll be OK for at least a few more years, and by
then Moore's law should result in better faster cheaper replacements to
handle the growth. There are, however, networks out there that also inject
a whole bunch of internal routes into their table, and they're a lot closer
to the edge.
My own personal opinion is that we'll be fine as long as prefix growth
continues at about the same rate it has recently. But if we make a drastic
change that results in a dramatic increase in the growth rate, that could
On 12/14/2009 11:07 AM, Ted Mittelstaedt wrote:
> One of the fundamental assumptions that we all seem to accept many
> times is the "Ballooning BGP table/DFZ" Much policy discussion seems
> to be centered around the idea that if the DFZ gets bigger it's going
> to cost bazillions of dollars for every ISP to upgrade equipment,
> yadda yadda yadda.
> I have to ask, however, is this assumption really technically
> Today I can walk into the store and purchase a PC that has a CPU in it
> that runs at a clock speed of at least 10 times of most routers, and
> has at least 10 times the amount of ram, for a quarter of the cost of
> the annual service contract for most DFZ routers (let alone the
> hardware cost)
> Now, I think anyone who studies router hardware would probably agree
> that the reason routers have historically been so underpowered is that
> router vendors use older, less expensive, and more tried, technology
> AND there isn't a NEED for faster tech. Why put a super powerful CPU
> or ASIC in the router when the purchaser only cares if the router can
> route at wire speed - and the wires consists of a few DS3's and 10/100
> ethernet ports? Older, cheaper tech can do those speeds while not
> even breaking a sweat.
> I have to ask, if the PURCHASERS of new router hardware were to tell
> the router vendors that they aren't gonna bother buying a router that
> cannot handle a half-million table entries in the BGP table, that the
> router vendors might just possibly see a need for the faster silicon -
> and step up to the plate and supply it? God knows they charge enough
> money for the OLD tech they are supplying now. Anyone heard of
> Moore's Law?
> I just have a hard time believing that when I can walk into a pizza
> place and drop a credit card down for payment - which carries just one
> of a billion or so possible numbers out there - and get an approval
> on it in less than a second at the register, that the silicon and
> software doesn't exist that could handle a DFZ that's an order of
> magnitude larger than what we have now.
> Just a random thought....
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