IPv6 day and tunnels

Mon Jun 4 22:08:02 UTC 2012

On Jun 4, 2012, at 2:26 PM, Joe Maimon wrote:

> 
> 
> Jeroen Massar wrote:
> 
>> 
>> Tunnels therefor only should exist at the edge where native IPv6 cannot
>> be made possible without significant investments in hardware and or
>> other resources. Of course every tunnel should at one point in time be
>> replaced by native where possible, thus hopefully the folks planning
>> expenses and hardware upgrades have finally realized that they cannot
>> get around it any more and have put this "ipv6" feature on the list for
>> the next round of upgrades.
> 
> 
> IPv4 is pretty mature. Are there more or less tunnels on it?
> 

There are dramatically fewer IPv4 tunnels than IPv6 tunnels to the best of my knowledge.

> Why do you think a maturing IPv6 means less tunnels as opposed to more?
> 

Because a maturing IPv6 eliminates many of the present day needs for IPv6 tunnels which
is to span IPv4-only areas of the network when connecting IPv6 end points.

> Does IPv6 contain elegant solutions to all the issues one would resort to tunnels with IPv4?

Many of the issues I would resort to tunnels for involve working around NAT, so, yes, IPv6
provides a much more elegant solution -- End-to-end addressing.

However, for some of the other cases, no, tunnels will remain valuable in IPv6. However, as
IPv6 end-to-end native connectivity becomes more prevalent, much of the current need for
IPv6 over IPv4 tunnels will become deprecated.

> Does successful IPv6 deployment require obsoleting tunneling?

No, it does not, but, it will naturally obsolete many of the tunnels which exist today.

> Fail.
> 

What, exactly are you saying is a failure? The single word here even in context is
very ambiguous.

> Today, most people cant even get IPv6 without tunnels.

Anyone can get IPv6 without a tunnel if they are willing to bring a circuit to the right place.
As IPv6 gets more ubiquitously deployed, the number of right places will grow and the cost
of getting a circuit to one of them will thus decrease.

> And tunnels are far from the only cause of MTU lower than what has become the only valid MTU of 1500, thanks in no small part to people who refuse to acknowledge operational reality and are quite satisfied with the state of things once they find a "them" to blame it on.

Meh... Sour grapes really don't add anything useful to the discussion.

Breaking PMTU-D is bad. People should stop doing so.

Blocking PTB messages is bad in IPv4 and worse in IPv6.

This has been well known for many years. If you're breaking PMTU-D, then stop that. If not, then you're not part of them.

If you have a useful alternative solution to propose, put it forth and let's discuss the merits.

> I just want to know if we can expect IPv6 to devolve into 1280 standard mtu and at what gigabit rates.

I hope not. I hope that IPv6 will cause people to actually re-evaluate their behavior WRT PMTU-D and correct the actual problem. Working PMTU-D allows not only 1500, but also 1280, and 9000 and >9000 octet datagrams to be possible and segments that support <1500 work almost as well as segments that support jumbo frames. Where jumbo frames offer an end-to-end advantage, that advantage can be realized. Where there is a segment with a 1280 MTU, that can also work with a relatively small performance penalty.

Where PMTU-D is broken, nothing works unless the MTU end-to-end happens to coincide with the smallest MTU.

For links that carry tunnels and clear traffic, life gets interesting if one of them is the one with the smallest MTU regardless of the MTU value chosen.

Owen

> 
> 
> Joe