Subject: Re: [Softwires] BGP TE attr last call by softwires WG

From: David Ward <[email-masked]>
Date: Tue, 12 Aug 2008 23:48:40 -0500

The softwire WG has LC'ed

http://www.ietf.org/internet-drafts/draft-ietf-softwire-bgp-te- 
attribute-01.txt

We will keep open an additional two-week period for wider review  
before moving forward in the publication process. Please have any  
comments to the authors and softwires WG by Aug 26, 2008.

-DWard, Alain Durand

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From: David Ward <[email-masked]>
Date: Tue, 12 Aug 2008 23:42:32 -0500

-DWard, Alain Durand

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From: "Samita Chakrabarti" <[email-masked]>
Date: Fri, 15 Aug 2008 16:28:22 -0700

Hi David, Alain and the authors:

I have read the draft a few times, and I am still trying to understand the
applicability of this draft from implementation point of view.

In introduction, it refers to BGP-based auto-discovery for L1VPN as one
possible case. 
But, it'll be very helpful to the implementors community if this draft has a
section on applicability and a few sentences on possible deployment
scenarios where this TE extension is useful.

Best regards,
-Samita

>-----Original Message-----
>From: [email-masked] [mailto:[email-masked]] On
>Behalf Of David Ward
>Sent: Tuesday, August 12, 2008 9:43 PM
>To: idr; [email-masked]; [email-masked]; [email-masked]; isis mailing list;
>[email-masked]; OSPF List; [email-masked]; Yakov Rekhter; Don Fedyk;
>Hamid Ould-Brahim
>Cc: Alain Durand
>Subject: [Softwires] BGP TE attr last call by softwires WG
>

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From: "Don Fedyk" <[email-masked]>
Date: Thu, 21 Aug 2008 17:39:47 -0400

Hi Samita

Sorry about the delayed response. Please see below. 

> From: Samita Chakrabarti [mailto:[email-masked]] 
> 

As Authors we did discuss this aspect. In principle we chose not to
limit the applicability, it applies where BGP auto discovery applies.
(I'll answer Adrian's point in another email.)  The basic idea behind
BGP Auto discovery is to give you an IP address with a metric.  BGP AD +
TE gives you an IP address with relevant TE attributes + the metric. 

The spec describes one possible deployment scenario (L1VPN) where this
TE extension _is_ useful and it is a non-goal
of this spec to list all possible deployment scenarios where this TE
extension may be useful. 

This is why we did not list other BGP AD applications. 

Regards,
Don

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From: "Samita Chakrabarti" <[email-masked]>
Date: Thu, 21 Aug 2008 15:13:57 -0700

Hi Don,

Thanks for the consideration of my comment and reply. Please see in-line.

>TE gives you an IP address with relevant TE attributes + the metric.
[SC>] 
      I agree that the I-D should not limit applicability of the usage to
certain scenarios and leave it open for any possible implementations and
usage as it comes along in the future.

But, my point was that as a reader/implementor of this I-D, one has to
understand the basic usage on the draft. The one line reference to L1VPN
does not clarify that in the current draft. 

So, I'd request that this I-D discuss some of the example scenarios in
either in the body of the draft or at the Appendix; this will help in
adoption of the draft in terms of implementation and deployment. The I-D can
clearly state that the usages are not limited to these scenarios but it can
be applicable whenever TE information should be carried over BGP.

>of this spec to list all possible deployment scenarios where this TE
[SC>]  The current reference to L1VPN example is unclear; please add a few
lines to it as you did above.  Also, I'll wait for your response to Adrian's
comments; I thought those were valid points that should be clarified.
Actually his scenario descriptions clarified some of my questions on this
draft.

Best regards,
-Samita

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From: Yakov Rekhter <[email-masked]>
Date: Mon, 25 Aug 2008 13:26:50 -0700

Samita,

> Thanks for the consideration of my comment and reply. Please see in-line.

see in-line...

> be applicable whenever TE information should be carried over BGP.

"The one line reference to L1VPN" that you mentioned above does clarify 
possible usage, as Section 4 of bgp-auto-discovery has the following:
  
    In addition to reachability information, the auto-discovery mechanism 
    may carry Traffic Engineering information used for the purpose of 
    egress path selection. For example a PE may learn the switching 
    capability and the maximum LSP bandwidth of remote L1VPN interfaces 
    from the remote PEs. 
  
If you think it would be useful, we could add the following after the 2nd
paragraph of Section 2 of the TE spec:
  
    Section 4 of [L1VPN] describes one possible usage of this 
    attribute.

Yakov.