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Re: [Bier] comments for draft-zhang-bier-bierin6-04.txt

IJsbrand Wijnands <ice@cisco.com> Tue, 17 March 2020 19:37 UTC

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From: IJsbrand Wijnands <ice@cisco.com>
In-Reply-To: <20200317163800.GA15016@faui48f.informatik.uni-erlangen.de>
Date: Tue, 17 Mar 2020 20:37:36 +0100
Cc: IJsbrand Wijnands <iwijnand@cisco.com>, Tony Przygienda <tonysietf@gmail.com>, "Nagendra Kumar Nainar (naikumar)" <naikumar@cisco.com>, BIER WG <bier@ietf.org>
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To: Toerless Eckert <tte@cs.fau.de>
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Subject: Re: [Bier] comments for draft-zhang-bier-bierin6-04.txt
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Toerless,

> would be easier to support longer bitstrings as needed. And the length
> of bitstrings is not nailed in stone forever like in IPv6, so
> different markets could evolve to support different (longer) length.

That is true, by overloading the IPv6 address the BM is fixed, but, it is way in front of the packet, so easy accessible for HW, so there will be a trade-off between more bits vs. performance penalty for longer masks. Longer masks will not come for free.

> The 256 is really todays lowest common denominator that we can
> support in all SP edge/core-routers.
> 
> With IPv6 via bitstrings in addresses (and correct me if you disagree),
> the main attraction was the ability of letting applications do BIER
> without having change APIs/host-stacks. That is cool short-term, but

Yes.

> the long-term benefit deteriorates as soon as someone does write
> a BIER SDK for linux and windows. And with that context in mind i
> found the long-term limitation of not being able to grow bitstrings
> in various markets to be too limiting.

We probably need to define what you consider short-term vs. long-term. Getting IGMPv3 supported in the host stack only took 10 years, is that long or short term?

Thx,

Ice.

> 
> Cheers
>    Toerless
> 
>> 
>> Thx,
>> 
>> Ice.

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