Re: [Bier] Questions on draft-eckert-bier-te-arch-01

Antoni Przygienda <antoni.przygienda@ericsson.com> Mon, 12 October 2015 20:55 UTC

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From: Antoni Przygienda <antoni.przygienda@ericsson.com>
To: Caitlin Bestler <caitlin.bestler@nexenta.com>, Eric C Rosen <erosen@juniper.net>, "bier@ietf.org" <bier@ietf.org>
Thread-Topic: [Bier] Questions on draft-eckert-bier-te-arch-01
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Date: Mon, 12 Oct 2015 20:55:42 +0000
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Subject: Re: [Bier] Questions on draft-eckert-bier-te-arch-01
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> 
> On 10/12/15 1:38 PM, Antoni Przygienda wrote:
> >   [Tony saiz:]  I would whole-heartedly agree here. Sub-domains are
> > really here to separate bigger-grain concepts like services or
> > different router sets running BIER, think source/destination ports in a sense.
> > Orthogonally, SI gives a transparent solution to the fact that we
> > can't realistically carry 32KB receiver bitmasks in each packet, in a
> > sense equivalent to IP fragmentation solving  the problem of limited media
> MTU.
> >
> > --- tony
> 
> The issue is that you are complicating the user interface to BIER for the benefit
> of an implementation detail that you are not describing in the architecture, and I
> believe is officially not-in-scope.

 [Tony saiz:]  hmm, both SI and subdomain concepts are explained extensively in the architecture documents. 

> 
> Would it be appropriate to add language to the effect that each Sub-Domain
> SHOULD/MAY map to a different routing underlay?

[Tony saiz:] sigh, no, in most generic sense the same routing underlay carries all sub-domains in the normal case. 

I am tad baffled by your seemingly unique interpretation of the architecture @ this point in time. We had tons of people looking @ it by now and no'one tried to replace SI with sub-domains or felt that the concepts are the same.

I utterly fail to see how the UI towards bier is being complicated given what you need, as I said, if your SDK towards BIER on your platform does not need  MT or sub-domains, just don't expose it and use 0,0 for everything. SI is hidden in the BIER layer itself. All you need really then is two (three) calls: 

Socketopt(my_BSL);   // set bitstring length if not default 
recv_on_bier(my_bfer_bit_nr);  // you can even skip the bit_nr given you're a leaf and frame arriving means it's for you as BFER 
send_to_bier(bfer_dst_bitmask);   // that will replicate/SI in the driver

the rest is lower layer/driver stuff. 

all done, forget all the other stuff like overlays/underlays/subdomains/MTs/BSL translations/unicast tunnels and anything else in the architecture that seems superfluous for your needs ... 

thanks 

--- tony