Re: Is Fragmentation at IP layer even needed ?

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On 2/9/2016 12:47 PM, Phillip Hallam-Baker wrote:
> On Tue, Feb 9, 2016 at 3:27 PM, Joe Touch <touch@xxxxxxx> wrote:
>>
>>
>> On 2/8/2016 4:47 PM, Phillip Hallam-Baker wrote:
>> ...
>>> Problem is that most of us have ethernet hubs rather than true IP
>>> switches. If we had real IP everywhere we could deprecate MAC
>>> addresses.
>>
>> Except that we derive self-assigned IPv6 addresses from MAC addresses.
> 
> If we didn't need them to be MAC addresses we could go to EUI-64 and
> have 16 shiny new bits to play with.

*You* wouldn't get to play with them; MAC vendors would. How would that
help, given they're already intended to be unique?


> On Tue, Feb 9, 2016 at 3:24 PM, Joe Touch <touch@xxxxxxx> wrote:
>>
>>
>> On 2/8/2016 2:44 PM, Joel M. Halpern wrote:
>>> I would note that tunnel mechanisms either need a very good path "size"
>>> reporting mechanism or a way to fragment.
>>
>> If you don't have a way to fragment, you end up with a hard limit on the
>> amount of tunneling and tunnel overhead. Otherwise, at some point, you
>> end up with a "size" of zero.
> 
> By definition a tunnel has two ends. There is no reason why
> fragmentation in a tunnel should make use of IP fragmentation as
> opposed to an in-tunnel fragmentation scheme.

Reason #1: IP reassembly is already deployed. Yes, we could use other
protocols as a shim to support IP-in-IP (and we do), but that doesn't
mean that they necessarily won't end up with the same problem - assuming
*their* IP should be 1280.

So let me understand:

	- first, you claim IP fragmentation is a network problem
	because it obscures info you need at forwarding devices
	(because you're peeking at L4)

	- now you want that info even further obscured by another
	layer of encapsulation

There's simply no pleasing you ;-)

Joe




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