[afripv6-discuss] Large US ISP (Comcast) Starts IPv6 Trial

Borg virtual.borg at gmail.com
Mon Feb 8 07:45:46 SAST 2010

Comcast sees end of IPv4 tunnel, beginning IPv6 trial
By Iljitsch van Beijnum </author/iljitsch-van-beijnum/> | Last updated January
29, 2010 6:34 AM

Comcast is asking for volunteers to participate in its upcoming IPv6 trials.
The cable ISP has been participating in IPv6 circles for a long time and
with its huge subscriber base, it is experiencing the IPv4 address scarcity
first-hand. So far, it has been able to get addresses for its customers—but
not for those customers' cable modems and set-top-boxes. These also need
addresses to function or to be managed. No problem, right? Just use private
IPv4 addresses, such as the 10 network, which holds 16.8 million addresses.
But with 25 million TV, 15 million ISP, and 6 million Comcast Digital Voice
subscribers, 16.8 million private addresses isn't enough for a regular
management system in which a management station can directly connect to each
managed device. So Comcast needs IPv6 just to run its internal network
effectively *now*.

We're also running out of IPv4
so at some point in the future, Comcast will be unable to obtain additional
addresses to connect new customers. So Comcast also needs to provide IPv6
service to its customers at some point and is looking for willing subjects
to give it a try.

Comcast plans four trials. The first one will use a transition technique
that is still under development, called 6RD. 6RD is similar to the 6to4
automatic tunneling mechanism that is available in Windows (it's enabled
automatically when the system has a public IPv4 address under Windows 7 and
Vista). The difference is that 6RD only tunnels IPv6 packets across an
IPv4-only part of the service provider's network, while 6to4 can tunnel
across large parts of the Internet, possibly incurring slowdowns.

The second trial will be with native IPv6. Here, IPv6 packets are
transmitted across the infrastructure without encapsulating them in IPv4
packets. IPv4 remains available, creating a "dual stack" deployment.
"Native, dual-stack is central to our IPv6 strategy and we expect that the
native dual-stack solution will be a significant part of the IPv6
transition, enabling IPv6 technology to evolve globally while still being
able to provide seamless services to the traditional IPv4 Internet," says

The third trial will basically be the opposite of the first: rather than
encapsulate IPv6 packets in IPv4 packets in order to traverse IPv4-only
network sections, IPv4 is now encapsulated in IPv6 to get across IPv6-only
parts of the service provider network. The technique for this will be "Dual
Stack Lite," a protocol that is being developed in the IETF Softwires
working group, which is co-chaired by Comcast's Alain Durand. In Dual Stack
Lite, the IPv4 hosts use private IPv4 addresses. A home router encapsulates
those in IPv6 packets, and a "carrier grade NAT" both decapsulates the
packets and performs Network Address Translation so that a lot of DS-Lite
clients can share a single IPv4 address.

The fourth trial will evaluate how to provide IPv6 to business class
customers. The first two trials are scheduled for the second quarter of
2010, the other two for the third quarter. At this time the details on what
participating in each trial will encompass are unclear, and signing up
doesn't necessarily guarantee participation.

Borg le Chevalier
"Common sense tells us the world is flat"
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