Verizon DSL moving to CGN

Mon Apr 8 14:23:03 UTC 2013

On 4/8/2013 7:20 AM, Tore Anderson wrote:
> BTW. It is AIUI quite possible with MAP to provision a "whole" IPv4
> address or even a prefix to the subscriber, thus also taking away the
> need for [srcport-restricted] NAPT44 in the CPE.

The problem is NAPT44 in the CPE isn't enough. We are reaching the point 
that 1 IPv4 Address per customer won't accommodate user bases.

The larger issue I think with MAP is CPE support requirements. There are 
ISP layouts that use bridging instead of CPE routers (which was a long 
term design to support IPv6 without CPE replacements years later). CGN 
will handle the IPv4 issues in this setup just fine. Then there are 
those who have already deployed IPv6 capable CPEs with PPP or DHCP in a 
router configuration which does not have MAP support. Given the variety 
of CPE vendors that end up getting deployed over a longer period of 
time, it is easier and more cost effective to deploy CGN than try and 
replace all the CPEs.

Given US$35/CPE, cost for replacements (not including deployment costs) 
for 20k users is US$700k. CGN gear suddenly doesn't seem so costly.

The only way I see it justifiable is if you haven't had IPv6 deployment 
in mind yet and you are having to replace every CPE for IPv6 support 
anyways, you might go with a MAPS/IPv6 aware CPE which the customer pays 
for if they wish IPv6 connectivity(or during whatever slow trickle 
replacement methods you utilize). While waiting for the slow rollout, 
CGN would be an interim cost that would be acceptable. I'm not sure 
there is a reason for MAPS if you've already deployed CGN, though.

I am sure Verizon did a lot of cost analysis.

Jack