Re: [OSPF] Advertising S-BFD discriminators in OSPF

Michael Barnes <> Fri, 26 September 2014 06:24 UTC

Return-Path: <>
Received: from localhost ( []) by (Postfix) with ESMTP id C2A9C1A1A37 for <>; Thu, 25 Sep 2014 23:24:07 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -15.287
X-Spam-Status: No, score=-15.287 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_HI=-5, RP_MATCHES_RCVD=-0.786, SPF_PASS=-0.001, USER_IN_DEF_DKIM_WL=-7.5] autolearn=ham
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id DXVX09mI7L3m for <>; Thu, 25 Sep 2014 23:24:06 -0700 (PDT)
Received: from ( []) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 484051A1A1E for <>; Thu, 25 Sep 2014 23:24:06 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple;;; l=2987; q=dns/txt; s=iport; t=1411712646; x=1412922246; h=message-id:date:from:mime-version:to:cc:subject: references:in-reply-to:content-transfer-encoding; bh=j36BYhtwuJeuSAXMh1DALspQNph8sTOqBQmk9PN7rro=; b=ejlS8QGH4uFf2Mozu7ZV+8Qu2sFY9oNreEGnuIP9sgZ0Z+x9ofaMxyku mqdWWyFjIkgL1KFniED6dK22Fq1CuQa8bLmFZp9qqxZTdY/csYJY0s36s i1CRkmI1ezJY0VPCIZq8v9oiG5ojYHlTfQkM2FN8iM9TCE+acnsIQeDsm U=;
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-AV: E=Sophos;i="5.04,603,1406592000"; d="scan'208";a="358383359"
Received: from ([]) by with ESMTP; 26 Sep 2014 06:23:52 +0000
Received: from [] ( []) by (8.14.5/8.14.5) with ESMTP id s8Q6NpP2018790 (version=TLSv1/SSLv3 cipher=DHE-RSA-CAMELLIA256-SHA bits=256 verify=NO); Fri, 26 Sep 2014 06:23:52 GMT
Message-ID: <>
Date: Thu, 25 Sep 2014 23:23:51 -0700
From: Michael Barnes <>
User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130110 Thunderbird/17.0.2
MIME-Version: 1.0
To: Manav Bhatia <>
References: <> <> <>
In-Reply-To: <>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Cc: OSPF - OSPF WG List <>
Subject: Re: [OSPF] Advertising S-BFD discriminators in OSPF
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: The Official IETF OSPG WG Mailing List <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Fri, 26 Sep 2014 06:24:07 -0000

Hi Manav,

That's a pretty funny analogy. I've got another one for you.

Say the RI LSA is like a corporate learjet for a tool company. When it 
gets flown around it's never full so you decide to use it to ship 
wrenches on it along with the executives. You're proud of your wrenches 
and want everyone to know how great they are, but do you really want to 
ship them that way? Maybe it's better to put the wrenches in their own 

So to be a little more serious, if the router wants to proudly proclaim 
its S-BFD capability then it deserves its own special LSA rather than 
being packed into one used for other things.


On 09/25/2014 06:27 PM, Manav Bhatia wrote:
> Hi Michael,
> Very interesting.
> I think there is a disconnect because of our interpretation of what an
> RI LSA is envisioned to carry. I assume its meant to advertise
> "optional router capabilities" while you believe its to be used solely
> for advertising "optional OSPF router capabilities". IMO, limiting the
> scope of RI to just OSPF is like using a humvee with all its bells and
> whistles to distribute balloons to the children in your friendly
> neighborhood park! We wanted a mechanism wherein each router could
> proudly tell the world that it was an S-BFD capable node and along
> with it also advertise the unique discriminator that the others would
> use to reach it. RI we felt, was the perfect tool that we could use
> for this purpose.
> And btw we're not the first ones to use RI for advertising a router
> capability that isnt pertinent to OSPF per se (RFC 5088).
> Cheers, Manav
> On Fri, Sep 26, 2014 at 12:47 AM, Michael Barnes <> wrote:
>> Hi Manav,
>> Perhaps I missed some earlier discussion, on why you decided to add the
>> S-BFD Discriminator TLV to the RI LSA, but I would prefer it not be in that
>> LSA. I would like to leave the RI LSA with only information pertinent to
>> OSPF rather than pollute it with information for which OSPF has no interest.
>> If you're concerned with a trend of creating a new Opaque type for every
>> application which might want OSPF to carry information for it, then I would
>> suggest we create a generic Application Information LSA.
>> Regards,
>> Michael
>> On 05/30/2014 01:47 AM, Manav Bhatia wrote:
>>> Hi,
>>> We had submitted the following draft a couple of weeks ago.
>>> This draft introduces a new OSPF RI TLV that allows OSPF routers to
>>> flood the S-BFD discriminator values in the routing domain.
>>> S-BFD is a new charter item (will be approved very soon) in the BFD WG.
>>> Would appreciate comments on this.
>>> Cheers, Manav
>>> _______________________________________________
>>> OSPF mailing list
> .