FYI - thought this would be of interest to some of you, there will be more
news on this front shortly.
http://www.comcast6.net/
6to4 Relays Activated
Tuesday, August 17, 2010
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
192.88.99.1. 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.
John
These are good news.
However, if Comcast provides native IPv6 to their customers, then the IPv6 native customers don't need these 6to4 relays?
Airport Extreme, Linksys and other user equipment, enable IPv6 by doing 6to4 tunnels, so what this press release says, is that there are many users who are already on IPv6 via Comcast network but not native? Providing relays close to them, is a good transition move. Alternatively, the measurement of this 6to4 bandwidth on IPv4 may give you an idea of the demand for IPv6 from your customers? May be you detected a non null number here?
I'm just trying to understand more IPv6 by the examples.
I'm personally using 6to4 at home, and experiencing some MTU issues, which seems related to some PTB packets suppressed on the way between some end points, and that can depend on which 6to4 relay I'm using. Still trying to debug this (I'm not too fanatic about it, but work on it when I have a bit of time). I thought I would mention that.
The WAND people have done some good studies: http://www.ripe.net/ripe/meetings/ripe-60/presentations/Stasiewicz-Measurements_of_IPv6_Path_MTU_Discovery_Behaviour.pdf
At the office, I have a more classical tunnel with he.net and do not have any issue there.
Before that they used our (Tele2) 6to4 relays in Amsterdam and Paris. I think this was discussed here 1-2 years back.
I couldn't find it, but <http://gpshead.blogspot.com/2009/01/consumer-router-ipv6-firewall-fail.html> says the same thing.
I urge more people to look up what 6to4 relays you're using and set up your own if needed. People *are* using it and you not doing it is making things worse for your customers. Yes, 6to4 is generally bad but it's out there. Everybody needs to think about it.
Franck,
As you know 6to4 is enabled by default in many cases and is used perhaps
more than folks realize. Because of this and other observations we decided
to deploy our own relays.
This does not alter our plans for our native dual stack trials, in fact, I
hope to have more news on this front soon.
It is true that 6to4 has challenges, some of these may be related to how
6to4 relays have been deployed. Others may be related to the protocol
itself. Either way, by deploying our own we observed an improvement, we
hope others have as well.
John
Mikael,
I agree with your points and echoed them in my earlier reply. 6to4 is out
there and is likely not to go away any time soon. Folks should definitely
see what 6to4 relay they default to, you might be surprised (or not).
FWIW - I updated ARIN's wiki for 6to4 relay deployment with some generic
updates. I will add some more text shortly that folks may find useful if
they decide to deploy their own 6to4 relays.
John
John Jason Brzozowski <john_brzozowski@cable.comcast.com> writes:
This does not alter our plans for our native dual stack trials, in fact, I
hope to have more news on this front soon.
comcast native dual stack is working fine at my house.
"traceroute6 -q1 mol.redbarn.org" shows details.
Franck,
As you know 6to4 is enabled by default in many cases and is used perhaps
more than folks realize. Because of this and other observations we decided
to deploy our own relays.
Right prior to this the nearest 6to4 relay router from the vantage-point
of comcast customers was at AMSIX. It's a given that you're going to
have path asymmetry, in this case however it was frequently worse in one
direction than in the other.
This ought greatly improve the performance of existing devices located
at comcast's customers.
Before we turned up our own relays the closest 6to4 relay was a single relay
hosted by a mid-western university. Regardless where the next closest
relays are located deploying our own resulted in improvements (as you
pointed out below).
John
As the 6to4 is an "default" option on Apple Airport Extreme to enable ipv6, I would have thought that Apple would have provided a few gateways? Same for Microsoft that has it in its OS?
Reminds me of the ntp servers issue built in on some devices...
Is there a list of 6to4 relays?
I'm curious.
Also, I'm also curious to know if ISPs in Europe (which are more advanced in IPv6 deployment) have experienced the same issues?
Franck Martin wrote:
Is there a list of 6to4 relays?
I'm curious.
Also, I'm also curious to know if ISPs in Europe (which are more advanced in IPv6 deployment) have experienced the same issues?
Sprint has one which is absolutely horrible (or was a year or two ago). I'd recommend any and every ISP to setup a 6to4, even if it runs over a v6 tunnel to HE. Accidentally getting one from someone else can give you exceptionally broken 6to4 connectivity. Being anycast, I'd say routeviews might be a good place to check for some, but often times they are hidden within the networks they serve.
That being said, 6to4 itself is often horrible. It works fine if you are talking 6to4 direct to the remote site (vs using a relay), but relays often break and are hard to troubleshoot due to their nature.
In the last year, my 6to4 tunnel has peaked at 6.44mb/s (1day average) but more common peaks are 150-250kb/s (5min average).
My tunnel to he.net was running 4-8 times that including the 6to4 relay serving all my customers + native traffic for 15 hosts and 2 servers. It's hard to get accurate on recent traffic loads as much of my v6 traffic shifted to dual stacked peers and I don't have a method of separating the v4/v6 traffic in the graphs (me thinks it's time to test ipv6 over mpls).
Jack
found it:
http://www.bgpmon.net/6to4.php?week=4
Not what I call a big list, considering...
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
In a message written on Tue, Aug 31, 2010 at 09:47:14AM +1200, Franck Martin wrote:
found it:
http://www.bgpmon.net/6to4.php?week=4
Not what I call a big list, considering...
Note that these are people willing to provide a 6to4 relay free to
the entire Internet.
There are plenty of people who offer 6to4 inside their own network
for their own customers, but never advertise the prefix to world+dog.
The Comcast 6to4 relays are not on this list, perhaps this is a list of open
ones?
John
Well I found my 6to4 gateway:
traceroute to 192.88.99.1 (192.88.99.1), 30 hops max, 40 byte packets
10 te3-3.ccr01.ind01.atlas.cogentco.com (154.54.3.30) [AS174] 244.965 ms 244.964 ms 244.952 ms
11 38.20.52.226 (38.20.52.226) [AS174] 244.336 ms 38.20.52.222 (38.20.52.222) [AS174] 244.300 ms 266.250 ms
12 38.104.214.6 (38.104.214.6) [AS174] 326.141 ms 326.139 ms 376.926 ms
13 ge-7-0-0.103.rtr.ictc.indiana.gigapop.net (149.165.254.142) [AS10680] 612.357 ms 612.367 ms 612.358 ms
14 rtr3.ul.indiana.gigapop.net (149.165.255.129) [AS10680] 376.777 ms 319.641 ms *
and I have so much issues with 6to4 that I have decided to disable it at home (airport extreme). I found out PTB was not transmitted and using scamper and the help of Matthew Luckie there is an odd MTU of 1422 from Internet to me. I suspect the 6to4 relay did not put the MTU to 1280 to be on the safe side... (I saw a recommendation like that on the net).
I have seen that the new hardware of the airport extreme has a new firmware that does more IPv6 magic, but old hardware are not yet benefiting this new firmware... Once a new firmware comes I'll re-enable and see...
PS: I found scamper to be a very good troubleshooting tool (once you know what to do) and wish it would be on all OS, like traceroute and now tracepath is...
Franck Martin wrote:
Well I found my 6to4 gateway:
<snip trace>
and I have so much issues with 6to4 that I have decided to disable it at home (airport extreme). I found out PTB was not transmitted and using scamper and the help of Matthew Luckie there is an odd MTU of 1422 from Internet to me. I suspect the 6to4 relay did not put the MTU to 1280 to be on the safe side... (I saw a recommendation like that on the net).
Actually, their MTU won't matter. 6to4 is EXTREMELY asymmetric when using relays. The return traffic to you will be via the first router than can support 6to4, not the relay you sent packets to. This is why troubleshooting 6to4 is such a PITA. If your airport supports static tunnels, set one up at tunnel brokers and be done with it.
Jack
Yes this is the list of visible relays as seen from the BGP backbone monitoring...
If you don't offer your relays to the rest of the world, they won't show up there...
I actually agree with the below. Using whatever you learn "today" via BGP
does not appear to be a good plan. 6to4 in particular becomes very
unpredictable and does in fact contribute to brokenness. I am not saying
deploying your own will make 6to4 good or great, it will however, help to
make it less broken and more controllable.
If operators deployed their own it would likely be beneficial to their
subscribers, particularly if there is a lot of 6to4.
I would also go out on a limb and say that absent and poorly deployed 6to4
relays collectively play hugely into the perception of brokenness.
There was a noticeable difference deploying our own 6to4 relays compared to
using the next or first available. I am not saying the other relay was
poorly run, just saying it is different having one on-net versus off-net.
John
Hey Bill,
No plans for Teredo at this time.
John