Comcast enables 6to4 relays

Bill Fehring lists at
Mon Aug 30 21:57:22 UTC 2010

On Sat, Aug 28, 2010 at 10:49, John Jason Brzozowski
<john_brzozowski at> wrote:

> As we started our IPv6 trials, we began to observe an increase in 6to4 relay
> traffic. 6to4 is a transition mechanism built into some operating systems
> and home gateways. While it is not a transition technology that Comcast
> planned to invest in due to limitations related to performance, we did
> observe poor performance when 6to4 was used by our customers. In many cases,
> these customers were not even aware that 6to4 was enabled by default or that
> their device or operating system was attempting to use 6to4 to communicate
> with IPv6 resources on the Internet.
> In most cases, we observed that 6to4-enabled operating systems and devices
> were attempting to use a 6to4 relay infrastructure hosted by a midwestern
> university. In order to improve the Internet experience for Comcast
> customers who are using 6to4, whether knowingly or not, we have decided to
> operate 6to4 relays on a temporary, trial basis.
> Comcast has decided to deploy 6to4 relays in five locations around our
> network to improve performance and predictability, as compared to operating
> relays from a single location. These 6to4 relays are available via the
> standard 6to4 Anycast IP address, according to RFC 3068, which is
> Devices attempting to use 6to4 within our network should
> automatically discover and utilize these new 6to4 relays, without end user
> intervention or configuration.
> The first pair of these relays was activated today. We plan to activate the
> remaining three within the next seven to ten days. We plan to monitor the
> performance of the 6to4 relays, to measure any beneficial effects resulting
> from adding these elements to our network. As our IPv6 trials evolve and we
> develop our plans for 2011 and beyond, we will assess our plans to support
> 6to4 moving forward.

Hi John,

First of all, that's great news -- I think it will help a lot.

Have you also considered deploying Teredo relays? I'm guessing that
there are quite a few Windows Vista+ systems that could benefit from
having a few closer Teredo relays and it's probably a similar amount
of traffic that you're seeing compared to 6to4 tunnels.


Bill Fehring

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