Subject: [mpls] poll on draft-decraene-mpls-ldp-interarea-04.txt as wg document

From: Loa Andersson <[email-masked]>
Date: Tue, 22 May 2007 19:10:08 +0200

Working Group,

the authors of draft-decraene-mpls-ldp-interarea-04.txt has
requested that the draft is made a working group document.

Send your comments (pros or cons) to the working group
mailing list, or directly to the working group co-chairs.

Loa and George

-- 
Loa Andersson

Principal Networking Architect
Acreo AB                           phone:  +46 8 632 77 14
Isafjordsgatan 22                  mobile: +46 739 81 21 64
Kista, Sweden                      email:  [email-masked]
                                           [email-masked]

_______________________________________________
mpls mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/mpls

---

From: "Prashant Desai" <[email-masked]>
Date: Wed, 23 May 2007 10:20:04 -0400

Im in favor of this draft. I belive the draft addresses real
deployment/scale issues. 

Prashant

-----Original Message-----
From: Loa Andersson [mailto:[email-masked]] 
Sent: Tuesday, May 22, 2007 1:10 PM
To: [email-masked]
Cc: Ross Callon; David Ward
Subject: [mpls] poll on draft-decraene-mpls-ldp-interarea-04.txt as
wgdocument

Working Group,

the authors of draft-decraene-mpls-ldp-interarea-04.txt has requested
that the draft is made a working group document.

Send your comments (pros or cons) to the working group mailing list, or
directly to the working group co-chairs.

Loa and George

--
Loa Andersson

---

From: Cao Wei <[email-masked]>
Date: Thu, 24 May 2007 14:36:32 +0800

Support.

---

From: Loa Andersson <[email-masked]>
Date: Thu, 24 May 2007 16:27:32 +0200

the poll will end June 5

/Loa

-- 
Loa Andersson

---

From: George Swallow <[email-masked]>
Date: Thu, 24 May 2007 11:05:00 -0400

[Chair hat off]

I still believe that this won't drastically reduce state or processing.
One of the points in support of this was reduction of compute time for
dijkstas.  Much of this could be gotten by noting what prefixes are
advertised by the set of ABRs and caching the result of just one.  (If
implementations aren't already doing this).  

I remain unenthusiastic.  

...George

========================================================================
George Swallow             Cisco Systems                  (978) 936-1398
                           1414 Massachusetts Avenue
                           Boxborough, MA 01719

---

From: "Thomas D. Nadeau" <[email-masked]>
Date: Thu, 24 May 2007 11:41:55 -0400

I agree with George here. I have a few other
concerns about this approach. First, I am concerned
that it might actually increase convergence
times.  The document itself even leaves the door open
to this:

7.2.     Impact on routing convergence time

    In case of an egress LER failure, performing IP route aggregation on
    ABRs will change the routing convergence behavior. The IGP will not
    propagate the notification of the egress LER failure outside of the
    egress area and failure notification will rely on LDP signaling
    through the end-to-end propagation of the LDP withdraw message. This
    failure notification may be faster or slower depending on the
    implementations, the IGP timers used and the network topology
    (network diameter).

    For failure of links and other nodes (Ps, ABRs), the failure
    notification and the convergence is unchanged. The convergence time
    may be improved because the RIB has fewer entries to update.

	Second, there is a note in the document that acknowledges
that the use of LDP to bind labels to routes not installed by
the IGP is explicitly prohibited by RFC3036. I believe this
architectural decision was made for a good reason. Changing this
not only leaves the potential for routing to be messed up,
but it also will require some significant changes to the
way in which implementations realize LDP and its interaction with
the FIB. In my opinion, the benefits of such a significant change are
probably outweighed by the negative aspects given the marginal  
improvement
this results in.

	--Tom

---

From: Ina Minei <[email-masked]>
Date: Thu, 24 May 2007 09:12:47 -0700 (PDT)

George,

 	The main reason for this was to avoid leaking PE loopback 
addresses across areas. This reduces the state maintained in the IGP.

 				Ina

---

From: "LE ROUX Jean-Louis RD-CORE-LAN" <[email-masked]>
Date: Thu, 24 May 2007 18:19:35 +0200

Hi George,

Yes, as pointed out by Ina, the main goal is not to reduce spf time, but rather to avoid overloading the IGP with reachability info.

Advertising all /32 prefixes significantly diminishes the 
benefits of deploying a multi-area IGP.

Best Regards,

JL

> -----Message d'origine-----
> De : Ina Minei [mailto:[email-masked]] 
> Envoyé : jeudi 24 mai 2007 18:13
> À : George Swallow
> Cc : [email-masked]
> Objet : Re: [mpls] poll on 
> draft-decraene-mpls-ldp-interarea-04.txt as wgdocument 
> 
> 
>  	George,
> 
>  	The main reason for this was to avoid leaking PE 
> loopback addresses across areas. This reduces the state 
> maintained in the IGP.
> 
>  				Ina
>

---

From: Ina Minei <[email-masked]>
Date: Thu, 24 May 2007 09:21:41 -0700 (PDT)

Tom,

 	Please see inline below, ###.
> times.

### The concern you are raising is that we now rely on the 
propagation of label withdrawals, rather than on reaction to IGP 
changes. This is the price one has to pay to maintain the small IGP state 
and the cleanliness of the network design. It is up to the provider to 
decide if this tradeoff is acceptable. The behavior described in the 
draft is enabled via configuration. On a side note, the diameter of 
each area is typically only a few hops, so the propagation of withdrawl 
messages should not be a concern. Besides, IGP messages don't propagate by 
magic either, they also need to travel in the network :-)

> architectural decision was made for a good reason.

### According to the authors of 3036, the reason was that it was the 
easiest to ensure no loops.

Changing this
> not only leaves the potential for routing to be messed up,

### So far nobody has come up with a good scenario on how this can happen.

> the FIB.

### Implementation details are vendor-specific.

 			Ina

In my opinion, the benefits of such a significant change are
> probably outweighed by the negative aspects given the marginal improvement
> this results in.

---

From: "DECRAENE Bruno RD-CORE-ISS" <[email-masked]>
Date: Thu, 24 May 2007 20:15:53 +0200

Thomas,

> that it might actually increase convergence

For all links failures, the convergence behaviour is unchanged.

For all Ps and ABRs nodes failures, the convergence behaviour is
unchanged.

For PE failure, the convergence behaviour is indeed changed as indicated
in the draft.
However, this does not mean that it will necessary be longer. Remember
that to propagate PE failure, the IGP will need three *consecutive*
convergences. One per area (egrees, backbone, ingress). Besides, as
indicated by Ina IGP messages also need to be propagated hop by hop. 

> The document itself even leaves the door open to this:
> 

Could you please elaborate on these reasons?

> > implementations aren't already doing this).
======================================================================
> > ==

---

From: "Prashant Desai" <[email-masked]>
Date: Thu, 24 May 2007 14:28:18 -0400

I very much agree with Ina...
1) Let the operator/provider decide on his/her "state vs convergence"
trade-offs. Tom's point sounds analogus to the IETF dictating "one
cannot have more then 'n' routers in an IGP area as it affects
convergence". 
2) Pl. provide concrete examples on routing issues.
3) LDP/FIB interaction is strictly a vendor/implementation issue. I can
at least say that we (ECI/Laurel) have this draft implemented on our
routers without any complications.

Thanks
Prashant

-----Original Message-----
From: Ina Minei [mailto:[email-masked]] 
Sent: Thursday, May 24, 2007 12:22 PM
To: Thomas D. Nadeau
Cc: [email-masked]
Subject: Re: [mpls] poll on draft-decraene-mpls-ldp-interarea-04.txt as
wgdocument 

 	Tom,

>
> 	I agree with George here. I have a few other concerns about this

> approach. First, I am concerned that it might actually increase 
> convergence times.

### The concern you are raising is that we now rely on the propagation
of label withdrawals, rather than on reaction to IGP changes. This is
the price one has to pay to maintain the small IGP state and the
cleanliness of the network design. It is up to the provider to decide if
this tradeoff is acceptable. The behavior described in the draft is
enabled via configuration. On a side note, the diameter of each area is
typically only a few hops, so the propagation of withdrawl messages
should not be a concern. Besides, IGP messages don't propagate by magic
either, they also need to travel in the network :-)

>
> 	Second, there is a note in the document that acknowledges that
the 
> use of LDP to bind labels to routes not installed by the IGP is 
> explicitly prohibited by RFC3036. I believe this architectural 
> decision was made for a good reason.

Changing this
> not only leaves the potential for routing to be messed up,

### So far nobody has come up with a good scenario on how this can
happen.

> but it also will require some significant changes to the way in which 
> implementations realize LDP and its interaction with the FIB.

 			Ina

> improvement this results in.

>> One of the points in support of this was reduction of compute time 
>> for dijkstas.  Much of this could be gotten by noting what prefixes 
>> are advertised by the set of ABRs and caching the result of just one.

>> (If implementations aren't already doing this).
>> 
>> I remain unenthusiastic.
>> 
>> ...George
>> 
>>

---

From: "JACQUENET Christian RD-DDEV-REN" <[email-masked]>
Date: Wed, 23 May 2007 08:47:42 +0200

Dear all,

I support this draft as a WG document.

Cheers,

Christian. 

-----Message d'origine-----
De : Loa Andersson [mailto:[email-masked]] 
Envoyé : mardi 22 mai 2007 19:10
À : [email-masked]
Cc : Ross Callon; David Ward
Objet : [mpls] poll on draft-decraene-mpls-ldp-interarea-04.txt as wgdocument

Working Group,

the authors of draft-decraene-mpls-ldp-interarea-04.txt has requested that the draft is made a working group document.

Send your comments (pros or cons) to the working group mailing list, or directly to the working group co-chairs.

Loa and George

--
Loa Andersson

---

From: Yakov Rekhter <[email-masked]>
Date: Thu, 24 May 2007 19:07:58 -0700

Loa,

> mailing list, or directly to the working group co-chairs.

I support making this draft an MPLS WG document.

Yakov.

---

From: Thomas Morin <[email-masked]>
Date: Fri, 25 May 2007 11:38:05 +0200

There definitely is an operational requirement to address, and this
approach appears as the best solution to it. 

In favor!

-Thomas

---

From: "Bob Thomas \(rhthomas\)" <[email-masked]>
Date: Fri, 25 May 2007 08:40:04 -0400

Support,
Bob 

> Subject: [mpls] poll on

---

From: Eric Rosen <[email-masked]>
Date: Fri, 25 May 2007 11:50:45 -0400

I am against the WG adopting this  draft, for reasons which I detailed in my
message of 12/14/06 to this list. 

The part of the problem that is actually real can be solved more simply with
techniques that are already deployed.

---

From: Luca Martini <[email-masked]>
Date: Fri, 25 May 2007 09:52:42 -0600

Loa,

I am in favor of this draft becoming a wg document. Here are some 
editorial comments that should probably be fixed in the next revision:

- Add an index.
- In the convergence discussion section it might be simple to also say 
that this will converge with the same characteristics as LDP ordered mode.
- It might be nice to explain the impact of a non compliant LSR as a P 
node in the middle of an MPLS network. The result is simply that the end 
to end LSP will not be established with no further adverse effect.

Thanks.
Luca

---

From: "DECRAENE Bruno RD-CORE-ISS" <[email-masked]>
Date: Fri, 25 May 2007 19:30:43 +0200

Eric,

> message of 12/14/06 to this list.

I answered your comments in my message of 01/04/07 to this list.
As you didn't send additional comments since then, we updated the draft
to detail the interactions between LDP and the IGP as you requested.
Then we presented these updates in Prague. 
 
> techniques that are already deployed.

Thanks on agreeing on the problem. Regarding the best solution, what is
called simple or not is really a matter of opinion and point of view.
>From a service provider perspective, using MPLS hierarchy with BGP
labelled addresses -as described in RFC 3107- introduce significant
constraints on the BGP engineering. It also requires BGP on all PEs and
ABRs which may not be possible or desirable (eg for L2 VPN PEs). In all
cases, it requires adding new MP-iBGP sessions on all deployed PE of the
AS. Not that simple in my opinion.

Regards,
Bruno

---

From: Kireeti Kompella <[email-masked]>
Date: Fri, 25 May 2007 13:28:14 -0700 (PDT)

> requested that the draft is made a working group document.

In favour.

> mailing list, or directly to the working group co-chairs.

Kireeti.
-------

---

From: raymond zhang <[email-masked]>
Date: Tue, 29 May 2007 07:18:11 -0700

Hi Loa,

> > requested that the draft is made a working group document.

In favor...

Regards,
Raymond

---

From: "JOUNAY Frederic RD-RESA-LAN" <[email-masked]>
Date: Tue, 29 May 2007 16:36:11 +0200

Loa,

In favor to adopt this draft as a WG document
It becomes particularly useful in case MPLS is extending to the access

Regards,
F. Jounay   

-----Message d'origine-----
De : Loa Andersson [mailto:[email-masked]] 
Envoyé : mardi 22 mai 2007 19:10
À : [email-masked]
Cc : Ross Callon; David Ward
Objet : [mpls] poll on draft-decraene-mpls-ldp-interarea-04.txt as wgdocument

Working Group,

Loa and George

--
Loa Andersson