Re: Is Fragmentation at IP layer even needed ?

[Phillip Hallam-Baker <[e-mail]>]

On Tue, Feb 9, 2016 at 6:17 PM, Joe Touch <[e-mail]> wrote:
>
>
> On 2/9/2016 3:09 PM, Phillip Hallam-Baker wrote:

>> Lots of things are already deployed. You presented a corner case. I
>> pointed out that there is no need to handle that corner case in the IP
>> layer.
>
> That's very NIMBY of you.

Not really. A tunneling layer is going to have to deal with
fragmentation under your model.

[Since Joe doesn't seem to be responding to the argument I made, I'll
not flog that horse further]


>>>         - now you want that info even further obscured by another
>>>         layer of encapsulation
>>
>> No, you raised the tunnel in tunnel corner case. I didn't suggest
>> requiring anything of the sort.
>>
>> If your tunnel can't fit the input packet on a 64K clean pipe, then it
>> should have the responsibility to figure out how to fragment.
>
> As long as it doesn't use "your" protocol to do it (IP)? Why?


Because the Internet architecture says to keep the core as simple as
possible. IP fragmentation introduces complexity that should be kept
out of the core. That is why.

We needed that feature in the Inter-network in 1980. We do not need
that feature int the core today. So it SHOULD NOT be an IP feature. It
can be a higher layer feature, it can be a feature that can still be
used at the network level.

Tunneling, encapsulation, VPNs, IP-in-IP are all network activities.
They shouldn't ever occur on the Inter-Network by definition.


> Someone has to support tunneling somewhere. IP is intended to be the
> universal interoperability layer - which means that it ought to be the
> layer to support it.

No, IP is the Inter-network Protocol.

The universal interop layers are UDP and TCP.