Re: few comments on draft-ietf-tewg-interas-mpls-te-req-01.txt

[raymond zhang <zhangr@info.net>]

Hi Yakov,

At 07:20 PM 12/6/2003 -0800, Yakov Rekhter wrote:
> Raymond,
>
> >  > > > >    The solution SHOULD provide an option for the Head-End LSRs to
> > control
> > > > > > >    if re-optimizing or not should there exist a more optimal 
> path
> > > between
> > > > > > >    the Head-End and the Tail-End LSRs.
> > > > > >
> > > > > > Good point on the option of traversing the same path...   So we
> > > will make
> > > > > > our original point as a
> > > > > > special case to your proposed wording above by adding the 
> following:
> > > > > >
> > > > > > "In the case of an identical set of traversed path, the 
> solution SHOU
> LD
> > > > > > provide an option for the Head-End LSRs to control if
> > > > > > re-optimizing or not should there exist a more optimal path in one
> > > of the
> > > > > > transit ASes along the inter-AS TE LSP path."
> > > > >
> > > > >Why do you need this "special case" ? In other words, why the text I
> > > > >proposed is not enough ?
> > > >
> > > > Well, in your proposed text, it is not specified if this HE LSR/TE 
> LSP is
> > > > the HE/TE of the inter-AS LSP or just
> > > > a segment of the inter-AS LSP.  Our requirement is to have the HE 
> LSR of
> > > > the inter-AS TE LSP, not just the mid point LSR of
> > > > segment LSP to have the control if re-opt or not in the case that 
> inter-A
> S
> > > > TE LSP needs to traverse along the same AS path.
> > >
> > >Are you saying that your requirement applies only when the new and the
> > >old path traverse the same set of ASs ?
> >
> > Oh no,,, this is just one of the applicable cases.
>
> I still don't quite understand what it adds...

I should probably clarify this a bit then...  Looking at the following 
diagram (example):

                                <--------- AS2 
----------->              <------ AS3--------->
PE1 - P1 - P2 - ASBR12 <----> ASBR21- ...- ASBR23 <--------> ASBR32 - P3...-PE4
           |            |                                          | 
|
           P3 -------ASBR14 <-----> ASBR41-...- ASBR43 <---------> ASBR34 
---
<------ AS1 ------------------>          <--------- AS4 
---------->               <------ AS3------->

If the original inter-AS TE LSP is built along AS1 - (via ASBR21) AS2 - 
AS3, then my thinking is that there maybe two cases where a more optimal 
path is available to the HE LSR of the inter-AS TE LSP:

Case 1. Still follows AS1/AS2/AS3 but a more optimal path is available 
between ASBR21 and ASBR23 ( or a different ASBR from ASBR21 or ASBR23 in 
the same AS2, (not shown in the diagram though))
Case 2. A more optimal path is available along AS1/AS4/AS3  (different path 
from the original).

So in either of above cases, we would like to provide an option (SHOULD) 
for PE1 in AS1 (HE of the inter-AS TE LSP) to control if re-opt or not.

Your proposed wording would cover case 2, however I don't think it is 
adequate or explicit enough to address requirement for case 1.  So I'd like 
to have a more explicit statement which is in my proposed wording as a 2nd 
paragraph.

Regards,
Raymond


> > If so, I would like to post -03 to reflect what we've discussed up until
> > now by this weekend so that I can get the last call process started...
> >
> > Thanks once again for your input.
> > Raymond
> >
> > >Yakov.
> >
> >