Comcast enables 6to4 relays

John Jason Brzozowski john_brzozowski at
Mon Aug 30 22:18:27 UTC 2010

Hey Bill,

No plans for Teredo at this time.


On 8/30/10 5:57 PM, "Bill Fehring" <lists at> wrote:

> 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.
> Best,
> Bill Fehring

John Jason Brzozowski
Comcast Cable
e) mailto:john_brzozowski at
o) 609-377-6594
m) 484-962-0060

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