1. Post IPv4 “completion” Making IPv6 incrementally deployable by making it backward compatible with IPv4. Alain Durand

2. Comcast As the largest cable operator in the United States, Comcast manages a large pool of IPv4 resources and is an active and responsible member of the Internet community. – We have been working within community-defined policies, maintaining effective utilization of resources. Comcast fully supports the community based, bottom-up, governance model of policy development to oversee those resources. – The Internet’s private-sector, self-regulatory governance model is a significant factor in the success of the whole Internet industry. – This model has proven responsive enough to meet the demands of a fast growing global industry.

3. Comcast IPv6 deployment Two phase approach: – 1) Infrastructures, Cable Modem management Done and/or in trial – 2) Connection to the home Planning & lab trials Lessons learned: – Early planning reduce cost – Networking is rather straightforward, code is mostly there – Software can be difficult to get from vendors – 3 rd party services are mostly non existent 3

4. IANA IPv4 completion is in front of us Uncertainty Today Completion of IPv4 resources will not be uniform: Large contiguous allocation requests might be denied by an RIR when fractioned space is still available. Small IPv4 allocation requests might be granted by an RIR long after completion of the IANA free pool. IPv4 will not stop working!

5. A broadband ISP must support continued, un-interrupted growth regardless of IPv4 address availability DISCLAIMER: Comcast has not made any decisions to deploy any of the following technologies.

6. Post IPv4 completion IPv4 resources alone will not provide a viable supply to the industry for the long term. The “Internet” edges will still be mostly IPv4: – Many hosts in the home (Win 9.x, XP,…) are IPv4-only. They will not function in an IPv6 only environment. Few of those hosts will upgrade to Windows Vista. – Content servers (web, Mail,…) hosted on the Internet by many different parties will take time to upgrade to support IPv6. 6

7. IPv4-onlydual stack provisioned dual stack *, IPv6-only provisioned device link router network Provisioning color code * devices with pure IPv6-only code are out of scope

8. Plan zero: dual-stack IPv4&IPv6 home gateway ISP Internet 192.168/16 legacy customer global v4 address home gateway NAT v4->v4 After IPv4 IANA completion, there will not be enough IPv4 addresses to sustain this model. Internet Today such deployments do not see much IPv6 traffic, mainly because there is little content reachable with IPv6.

9. Plan A: dual-stack core new customers are provisioned with IPv6-only but no IPv4 support IPv6 provisioned home gateway ISP Internet 192.168/16 lots of broken paths… 192.168/16 legacy customer global v4 address home gateway NAT v4->v4 impact on new customers: - legacy IPv4 devices can’t get out of the home. - new IPv6 devices can’t get to the IPv4 Internet.

10. Plan B: double NAT new customers are provisioned with overlays of RFC1918 private v4 address home gateway NAT v4->v4 Carrier grade NAT ISP Net 10 - two layers of NAT - no evolution to IPv6 - network gets increasingly complex to operate. - Intersections of Net 10 overlays are prone to failures. carrier-grade NAT 192.168/16 legacy customer global v4 address home gateway NAT v4->v4 Internet complex internal routing (source based?) to handle both legacy & RFC1918 customers on the same access router… private v4 address home gateway NAT v4->v4

11. Plan C: dual-stack lite new customers are provisioned with IPv6-only + IPv4 support IPv6 provisioned home gateway ISP Internet Carrier grade NAT 192.168/16 - simplifies network operation - provides an upgrade path to IPv6 carrier-grade NAT carrier-grade NAT legacy customer IPv4 provisioned home gateway NAT v4->v4 192.168/16 Dual-stack lite provides IPv4 support using an IPv4/IPv6 tunnel to a IPv4/IPv4 NAT.

12. Plan C’: New stand-alone devices are provisioned with IPv6-only + IPv4 support with dual-stack lite Dual-stack lite client: dual stack device IPv6-only provisioned no IPv4 address ISP carrier-grade NAT Stand-alone, dual-stack, IPv6-only provisioned devices can use dual-stack lite to reach the IPv4 Internet. Internet

13. Dual-stack lite makes IPv6 incrementally deployable