On Sun, Mar 20, 2011 at 3:28 AM, Owen DeLong <owen@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 service. -- Jeff S Wheeler <jsw@inconcepts.biz> Sr Network Operator / Innovative Network Concepts