Hi Eliot,

You wrote:

>>      Eliot's suggestion (as I understand it) to exclude
>>      larger end-user networks from the (presumably)
>>      renumbering based solution for smaller networks
>>      would still leave many "smaller" networks way too
>>      big for "routine" renumbering.
> 
> Again, let's separate the problem from the solution.  To put it another
> way, home and SMB networks really don't even have an option today to be
> multihomed (at least not at the network layer), and so whatever growth
> we're seeing today in the routing table is strictly that of larger
> institutions, and related traffic engineering and (to a lesser extent)
> disaggregation to protect large prefixes.

I agree - and I think we all agree - that most of the growth in the
DFZ routing table, currently doubling every 4 years, is from end-user
networks doing as you say.  The remainder is ISP growth - which I
think we accept as a natural, proper and generally sustainable load
for the BGP system to handle.

However my understanding of the RRG charter is not just to find a
scalable routing and addressing solution for existing PI end-user
networks - to eliminate some or all of the burden they will place on
the DFZ - but to also provide a scalable solution to the multihoming
and portability needs of millions (hundreds of millions or billions?)
of smaller networks.  These are networks which don't exist yet, or if
they do exist, don't have PI space and would generally be unable to
get it.

"Portability" is my word, since I think keeping one's address space
while choosing another ISP is the only reliable, acceptable, approach.

However, I agree that if the network only has a single IPv4 address -
such as a SOHO running from a cable modem, fibre or DSL service - it
is probably not too hard to renumber it.  If it was IPv6, I guess this
would be a /64 - or perhaps a /48.  For multihoming, the network would
have two /64s, such as one from the DSL service and one from the cable
modem service.

Still, as Bill Herrin wrote:

  http://www.irtf.org/pipermail/rrg/2008-October/000079.html

     No matter how I manage my network, I only control half that
     process.  When the agency I'm contracting for wants my source
     IP address to put in their firewall, I don't have the luxury
     of saying, "Gee, I really don't manage my network that way."

this supposed ease of renumbering a "small" network ignores wherever
the addresses turn up in other systems, such as ACLs as Bill
mentioned, or perhaps in DNS systems not directly controlled by the
network administrator.

Let's say I run a web server from my home network for the local
Neighbourhood Watch - then every time I get a new ISP, with new
address space, I need to get someone else to change the IP address in
the Neighbourhood Watch's DNS.  (Maybe I am mistaken - is there
another way of doing this?)

Also, with IPv6, I could in principle have a bazillion servers at
home, each with their own public IP address.  Changing over all the
DNS settings for those would be error-prone and painful, especially if
the DNS system was not something I ran on my own server.

With SHIM6 and IPv6, I need two ISPs - so changing ISPs is arguably
going to happen twice as often as with IPv4 portability only (no
multihoming), where I only need one ISP at a time.


> If one solution can fit all, all the better.  One is better than two,
> all other things being equal.  Whether they are or not is a fair question.

I agree.

 - Robin

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