Re: [RRG] Future mapping DB size, small micronets/EIDs

[Robin Whittle <rw@firstpr.com.au>]

Hi Brian,

Regarding maximum length of LISP EID prefixes, you wrote:

> I think we've had that conversation (at least, I was having it
> with Tony). My conclusion is that the longest prefix is
> undoubtedly /32 or /128, but that doesn't answer the important
> question of how many prefixes need to be mapped, which depends
> on how many sites need to be mapped and what is their size
> distribution.

While I understand the mapping data format for LISP will enable a
/32 IPv4 to be specified, I wonder whether it makes sense to have
ITRs all over the world tying to divide the IPv6 address space any
finer then /64.

To allow for /128 in the data format rather than limiting it to /64
adds another 8 bytes to every EID record, although it is going to be
very long anyway, since there will be multiple 128 bit RLOC
addresses for the ETRs.

I also think that allowing /128s will complicate the design of every
ITR, or at least bloat it or slow it down if someone really uses a
/128 EID prefix.

I am interested to know how the key LISP-ALT people envisage their
system being used.  Their notion of the end-users the system serves
isn't in the IDs, but I infer from some of what they write on the
list that their vision is a lot more like current PI space end-users
than the broad range of end-users, including non-technical
individuals with cellphones and laptops, I and a few other people
are envisaging.


>> Also, given the answer to that question, how many EIDs do you
>> think - as an outside but not unrealistic estimate - a LISP
>> scheme would ever have to support, say in 2015, 2020, 2030, 2040
>> and 2050?

> And to that question we've had answers in the 10^7 to 10^9 range,
> depending on a lot of assumptions which are economic and
> sociological as much as they are technical.

But what do you and the LISP-ALT folks think about mobility?  I
don't see how mobility could be provided by ALT, NERD, APT or TRRP.
I can see how it could be provided by Ivip.

Mobility between provider networks (eg. operators of different radio
networks) could add tens or hundreds of billions of dollars of value
to the Net and IP-centric cellphones, by enabling each one to have
its own micronet / EID, no matter where it is in the world.

To do this, you need fast push of some kind, and since push to every
ITR in the world (NERD) doesn't scale to these cellphone scenarios,
the only scalable approach seems to be hybrid push-pull like APT or
Ivip.  However APT currently does slow push via flooding the mapping
data around the world in a new BGP instance.  That leaves Ivip or
some other fast hybrid push-pull system.

Without mobility, I could imagine that maybe, one day, we might have
10^7 end-users who want number portability (I know people wince at
this term, but that is what people quite reasonably want and
arguably need) for their home and business networks.  Maybe 10^8 if
it became the common way of running a business to have at least one
IPv4 address which was genuinely stable, or with IPv6, a /64.

But without mobility for laptops/cellphones/video-players (whatever
these things develop into), how could the 10^9 or 10^10 figures be
credible?

In short, ALT or TRRP could handle unlimited numbers of EIDs, but
since they can't provide mobility, the demand will never be more
than a few tens of millions.

A few tens of millions of relatively static mapping information is
easy for NERD or APT to handle, so the primary (only?) argument for
ALT or TRRP goes away.  NERD or APT are better because the don't
delay any initial packets.

But NERD can be improved by allowing some ITRs to be caching ITRs,
querying a local query server wherever there is a full push ITR.  I
suggested this series of improvements on 22 January:

  ALT + NERD is inelegant & inefficient, compared to APT or Ivip
  http://psg.com/lists/rrg/2008/msg00176.html

No-one ever debated my argument in detail.

The first step of upgrading NERD makes it a hybrid push-pull system
like APT or Ivip.  Then we make it fast push rather than slow, which
enables the mapping data to be a single IP address, and removes the
reachability and multihoming service restoration decision functions
from the ITRs . . . and the system can support mobility and looks a
lot more like Ivip.

While a hybrid push-pull system can scale larger than a pure push
system, neither system copes well with end-users changing their
mapping very frequently, *unless* they have to pay a small fee for
each change.  That fee will naturally be set by market forces so it
pays for as much of the push network as needs to be paid for by the
end-users (ISPs will pay for the final stages as they run their own
Replicators to fan the mapping data around inside their networks).

Then, the more efficient the global push system, the lower the
prices and the more end-users will want to have micronets - and the
more they will be happy to change their mapping.

The physical mobility of cellphones is an immensely valuable thing.

Perhaps it is an anomaly in Australia, but the cost of making a
cell-phone typically exceeds the rate at which people can earn money
before tax.  (There are many freebie and discount plans, but many
folks need ordinary plans in which they are charged a cent a second.
 That is USD$33 an hour.)

I reckon a global fast push system can be largely funded by a fee
per update which in practical terms in general physically mobile use
is a lot cheaper than what people are paying for cell-phone calls today.

 - Robin


--
to unsubscribe send a message to rrg-request@psg.com with the
word 'unsubscribe' in a single line as the message text body.
archive: <http://psg.com/lists/rrg/> & ftp://psg.com/pub/lists/rrg