SP's and v4 block assignments

Jeff Wheeler jsw at inconcepts.biz
Sun Mar 20 13:18:54 CDT 2011

On Sun, Mar 20, 2011 at 3:28 AM, Owen DeLong <owen at delong.com> wrote:
> This assumes an HFC network and not a PON or DSL topology
> where it is not an issue.

It assumes that the access network topology does not employ any kind
of triangular routing to terminate the subscriber's layer-3 traffic on
a desired access router, as opposed to one dictated by where the
subscriber's layer-1 facility terminates.

It's really not an issue of HFC or DSL, and I guess I should have
spelled it out since several folks failed to understand that -- it's
an issue of carrying routes for customer static IPs in your IGP or
being able to steer their sessions to a certain device.

I'm sure we all remember the days when ordinary dial-up subscribers
could get a static IP address from nation-wide dial-up ISPs, and the
network took care of routing that static IP to whatever box was
receiving the modem call.  The problems with scaling up static IPs for
fixed-line services are much less troublesome than a nation-wide
switched access service like dial-up; but the same basic constraints
apply -- you need triangular routing, or a bigger routing table, when
users' static IPs are not bound to an aggregate pool for their layer-3
access router.

"Almost Static IPs," which remain unchanged until your ISP has some
need to reorganize their access network and move you into a different
IP address pool, are a good compromise that are okay for many
end-users.  That eliminates all the technical challenges (from the ISP
perspective) and yet there are many ISPs that offer this product only
to "business" customers, not ordinary residential subscribers -- which
means you're still left with the issue that they simply don't want to
offer anything like a static IP to the lowest-margin customers, as
they hope it will force some subscribers to upgrade to a higher-cost

Jeff S Wheeler <jsw at inconcepts.biz>
Sr Network Operator  /  Innovative Network Concepts

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