Re: [OSPF] WG Adoption Call for "OSPF Stub Neighbors"

Anton Smirnov <asmirnov@cisco.com> Sun, 31 January 2016 20:14 UTC

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Date: Sun, 31 Jan 2016 21:14:15 +0100
From: Anton Smirnov <asmirnov@cisco.com>
Organization: Cisco Systems
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To: "Acee Lindem (acee)" <acee@cisco.com>, OSPF WG List <ospf@ietf.org>
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Subject: Re: [OSPF] WG Adoption Call for "OSPF Stub Neighbors"
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    Hello,
    Hub-and-Spoke topology is a known topology where OSPF traditionally 
performed poorly and in my opinion work in this area is very important.
    On the other hand, I have number of concerns regarding usability of 
approach chosen in this draft and I think in its current state the draft 
is not ready for WG adoption.
    I have big concerns regarding implementation simplicity and solution 
applicability (i.e. hub-and-spoke networks where proposed solution 
doesn't work). But first of all I want to make a comment on the text as 
it is.
    Some hub-and-spoke topologies are point-to-multipoint networks. 10 
years ago it was a fraction of all hub-and-spoke WAN, nowadays it is a 
majority. Draft doesn't consider multipoint operations (at least it 
doesn't have word 'multipoint' in it). But multipoint has very big 
implications on having multiple spoofed Router LSAs and their filtering 
- since all stub neighbors are on the same interface, one can't use 
per-interface filtering (which is tightly related to per-interface 
flooding). Spoofed Router LSA will have a new type of flooding behavior 
- per-neighbor. This is doable but it is not specified anywhere and is 
not coded by any implementation I am aware of (i.e. existing filtering 
mechanisms are between different interfaces, not between neighbors on 
the same multipoint interface).
    So the draft needs to define new LSA flooding scope - per-neighbor 
flooding scope, much like interface-scope flooding had to be devised for 
Opaque LSAs.
    This is not all for implementation complexity not covered in the 
draft but it will be a good start.

Anton


On 01/26/2016 05:39 PM, Acee Lindem (acee) wrote:
> This draft was has gone through some refinements after being presented in
> Hawaii and in Yokohama there was some support of this protocol extension.
> Here is a URL for you convenience.
>
> https://datatracker.ietf.org/doc/draft-raza-ospf-stub-neighbor/
>
> Please indicate your support (or concerns) for adopting this as a WG
> Document. The WG Adoption call will end in 2 weeks.
>
> Thanks,
> Acee
>
>
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