Comcast's 6to4 Relays

Owen DeLong owen at
Wed Apr 20 19:32:50 UTC 2011

1.	Yes.
2.	Perhaps, but, it's minimal internal risk and the risk it poses to others
	can be mitigated by those others installing appropriate services
	on their own networks.
3.	We agree here as well.


On Apr 20, 2011, at 9:33 AM, Bhoomi Jain wrote:

> Mr. Delong,
> I am simply trying to explain that running a 6to4 on your network is a good idea, however advertising the anycast prefix to other networks has some risk, especially if you're experiencing problems with your Internet peerings.  Hopefully Comcast will upgrade its capacity soon.  I appreciate Mr. John's continued leadership and contribution to the IPv6.
> Sincerely,
> Bhoomi Jain
> At 20 Apr 2011 14:51:48 +0200 (CEST) from Owen DeLong <owen at>:
>> The better solution to that problem is to get additional 6to4 relays deployed closer to India. Perhaps encouraging Tata to take some leadership in that area, for example.
>> I do not believe that the opening of the Comcast relays will harm BGP best path selection for the 6to4 prefix except in rather broken and/or pathological cases of BGP best path selection. Those cases should be relatively easy to identify and correct locally without preventing Comcast from significantly improving the 6to4 situation for the areas they serve by opening their relays.
>> I applaud John for his leadership in this area and I think the IPv6 work being done by Comcast sets a good example for the community. As a Comcast customer, praising Comcast does not come easy to me, but, in this area, they are doing excellent things and should be commended.
>> Owen
>> Sent from my iPad
>> On Apr 19, 2011, at 10:26 PM, Bhoomi Jain <bhoomij at> wrote:
>>> Mr. John,
>>> I thank you for asking the advice of the community.
>>> As our colleagues suggest, having 6to4 relays inside the network helps to reduce the latency.  Opening up your generous services to a larger Internet community by advertising the BGP prefix outside the network could have extreme and unintended consequences.
>>> To give you an idea, a lot of the Internet in India depends on the service of the Tata companies, with international routing coming from Tata Communications AS 6453.  Announcing to 6453 as a customer, I would worry about its treatment as BGP best-path, in place of closer 6to4 relays.  As you understand, these circuits are very far away, and also very full.  This is not something I would recommend.
>>> Sincerely,
>>> Bhoomi Jain
>>> At 19 Apr 2011 22:51:24 +0200 (CEST) from "Brzozowski, John" <[email protected][]>:
>>>> Folks,
>>>> Since deploying our 6to4 relays, Comcast has observed a substantial
>>>> reduction in the latency associated with the use of 6to4. As such we are
>>>> contemplating further opening our relays for use by others. The
>>>> availability of our 6to4 relays should improve the experience of others
>>>> using 6to4 as a means to access content and services over IPv6.
>>>> We have been open about our IPv6 activities and wanted to follow suit by
>>>> reaching out to the community and soliciting feedback before moving
>>>> forward. As always we wish to continue to advocate and support the
>>>> universal deployment of IPv6.
>>>> Please send any comments or questions to the list or if you wish to me
>>>> directly.
>>>> John
>>>> =========================================
>>>> John Jason Brzozowski
>>>> Comcast Cable
>>>> e) mailto:[email protected][[]]
>>>> o) 609-377-6594
>>>> m) 484-962-0060
>>>> w) [[]]
>>>> =========================================

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