On Wed, Jun 25, 2014 at 10:35:38PM +1200, Alexander Neilson wrote:
I am looking to see what others experiences are with transit providers.
Mainly I am wondering about IPv6 Support and MTU Sizes
From talking to my upstream providers it appears that 1500MTU is the limit I have access
to, and one of my two upstreams doesn?t provide IPv6 for transit.
This leads my to a few logical questions:
* How many transit providers provide MTU above 1500 Bytes?
* How many transit providers do not provide IPv6 transit?
* How do others handle EDNS?
I was doing some looking around our systems a while back and I found a default setting in
the Bind9 version we were running that set EDNS to 4096 Bytes. Now all of our transit is
limited it seems to 1500 Bytes, so I set the config to limit the announced support down
into the usable range by us and saw a reduction in the need for DNS retries.
Do other people just have better handling of fragmentation? Do you find any issues having
EDNS announcing support for sizes above your transit? do you just have transit that
supports MTU over 1500 Bytes?
I'm not a big fan of TCP/IP DNS .. and so I just keep DNS answers small. So I cannot
say anything about that sorry.
Internet Transit over 1500 bytes is not really doable. Even if you managed to get over
1500 MTU, where are you going to get it to? A lot of the time MTU path discovery
doesn't work nearly as well as preferable, so if you have a server with a large MTU
you pretty much have to use MSS clamping to fit traffic for 1500 MTU.
You may have better luck if you want a larger tunnel between two locations. But the
internet in general isn't likely to shift any time soon, as much as I'd like to
There's also a question of whether large MTU's are even a good thing. On a 10
megabit DSL connection, 1500 MTU means that packets take over 1 msec, to send, and having
in the queue means you're going to add jitter. If you want to prioritise VOIP traffic
or minimise latency in general, then serialisation delay becomes a concern. It's not
bad now that connections are starting to increase in speed, but I don't really see it
being a good idea until you get to gigabit speeds, where the benefits of conserving
hardly matter. And modern ethernet cards deal well with lots of smaller packets.
And a big issue in my opinion is the lack of IPv6
support from transit providers. I am not sure about other providers but it will be one
deciding factor when purchasing transit going forward.
I'd rather uptake of IPv6 was controlled and functional myself. If you take a look
around the current IPv6 Network most people haven't even configured reverse DNS. The
cases where IPv6 is beneficial is in situations like Skype, where clients on shared
networks want to create direct connections to each other. Any Skype still doesn't
AFAIK. The benefits of web servers, and email servers having concurrent IPv6 and IPv4 is
mostly as a kind of proof-of-concept.
I wouldn't say it's necessarily a bad idea to choose providers based on being able
to offer IPv6, but using it at the moment doesn't really hold any benefit - and
that's probably one
of the reasons that uptake is so low in New Zealand. Peering is often worse for things
like Akamai, and other CDN's. Facebook had a sustained outage that hit (some) IPv6
and not IPv4 users.
Happy to receive information off list if people don?t
want to name on here.
Neilson Productions Limited
021 329 681
022 456 2326
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