Re: Is Fragmentation at IP layer even needed ?

[Fernando Gont <[e-mail]>]

On 02/09/2016 04:10 PM, Phillip Hallam-Baker wrote:
> On Tue, Feb 9, 2016 at 10:59 AM, Warren Kumari <[e-mail]> wrote:
> 
>> <rant>
>> There seems to be a fair amount of discussion requiring knowledge of the
>> host stack, or understanding of the capabilities of a specific network (e.g:
>> all the hosts support [reassembly of "large" fragments | TCP fast open], all
>> the routers in my network support looking deep into EH, all my devices set
>> flow labels, etc.).
>>
>> This feels deeply flawed to me - applications shouldn't need to have deep
>> knowledge of the network or end system stack behavior, and relying on
>> specific behavior of a system / network makes the application brittle and
>> non-portable[0].
> 
> Absolutely. And I see similar issues when people try to get me to use
> HTTP features in Web Services.
> 
> I know all about said HTTP features. I wrote some of them. But when I
> am running a Web Service over HTTP, HTTP is a lower level protocol
> layer and I don't want my application to depend on any feature at that
> level unless there is a clean separation of concerns.
> 
> 
>> Until a behavior is supported by the lowest common denominator / (almost)
>> everything, it probably makes sense to avoid it[1].
> 
> Probably. But there is another option: Put all the wood behind one arrow.
> 
> The IETF is architected as a research lab rather than a standards
> body. That has good points and bad points. One of the bad points is
> that we don't end up with one consistent and coherent way to achieve
> an outcome, we end up with multiple options and a hope that 'the
> market' will come to a decision. And then people are upset when the
> market decides that it is quite happy where it is.
> 
> The other problem is that as Warren points out, the process doesn't
> really produce proposals that are fully interchangeable. For years
> people were trying to persuade people to move to DNSSEC and IPv6 with
> what I call the 'boat anchor' strategy of forcing other specs to build
> on them as a platform requirement. I once sat through a BOF where a
> group of people who claimed to be doing 'home automation' (what we
> called IoT before) who started off by mandating IPv6.
> 
> If you are writing an application protocol and it mandates IP let
> alone a specific version then you are doing it wrong.

FWIW, part of that has to do with using low-level APIs in apps.

If you think about it, an app tipically has to be DNS-aware, know about
ports, etc., rather than "get_me_a_connection()".

Thanks,
-- 
Fernando Gont
SI6 Networks
e-mail: [e-mail]
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