Re: [Lsr] Flooding Path Direction

How is it impossible that A may flood to B, but B does not flood to A ?
How does it follow that if A floods to B, then B must also flood to A ?

Uni-directional flooding allows a more efficient flooding topology to be built.
Suppose you had to build a flooding topology with the rule: 2 incoming and 2 outgoing floods.
With bidirectional flooding, the incoming are the same as the outgoing,
so any incoming flood can only be propagated on one interface.
With uni-directional, any incoming can go out two interfaces.
To achieve 2 out with bidirectional, you need 3 in, 3 out, because the ins and outs are the same.

Regards,
Jakob.

-----Original Message-----
From: Peter Psenak <ppsenak@cisco.com> 
Sent: Thursday, April 4, 2019 12:28 AM
To: Jakob Heitz (jheitz) <jheitz@cisco.com>; tony.li@tony.li
Cc: lsr@ietf.org
Subject: Re: [Lsr] Flooding Path Direction

Jakob,

given that there is a single flooding topology calculated for an area, I 
don't see how this can be unidirectional, considering that flooding 
topology is used to flood in any direction.

thanks,
Peter

On 04/04/2019 08:26 , Jakob Heitz (jheitz) wrote:
> I mean flooding in one direction only, not unidirectional forwarding.
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> Regards,
>
> Jakob.
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> *From:* Tony Li <tony1athome@gmail.com> *On Behalf Of *tony.li@tony.li
> *Sent:* Wednesday, April 3, 2019 11:19 PM
> *To:* Jakob Heitz (jheitz) <jheitz@cisco.com>
> *Cc:* lsr@ietf.org
> *Subject:* Re: [Lsr] Flooding Path Direction
>
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>     I think this is too restrictive.
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>     We should not exclude algorithms that can build a flooding topology
>     with unidirectional links.
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> Well, right now, the protocol doesn't really support unidirectional
> links. At all.
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>
> Tony
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