Re: [Isis-wg] New Version Notification for draft-ginsberg-isis-prefix-attributes-00.txt

["Les Ginsberg (ginsberg)" <[e-mail]>]

Xiaohu -

You asked

"Would you please further point to the exact
> > > place of the referenced SR draft (draft-
> > > ietf-isis-segment-routing-extensions-02) where it said that it's
> > > useful to know whether an advertised prefix is directly connected to
> > > the advertising router or not"

I believe that question has been answered.

Using the functionality defined in the prefix-attributes draft note the following:

  o If the N flag is set and the R and X flags are NOT set then the advertisement is for a directly connected address local to the advertising router - there is no need to also include the source Router ID - which allows a more efficient encoding in these cases. 
  o In cases where the prefix has been leaked from one level to another, the presence of the source Router ID is also required. 
  o The use of Reachability TLVs to carry this information also allows topology specific node addresses to be advertised if desired.
  o Once prefix attribute support has been deployed there is no need for the P-flag - this can be deprecated.

It is true that draft-xu-isis-routable-ip-address-01 defines another way to advertise the source of a directly connected advertisement, but it is not as flexible nor as efficient in its encoding (in some cases) as the definition in the prefix-attributes draft. 

   Les

> -----Original Message-----
> From: Xuxiaohu [mailto:[e-mail]]
> Sent: Friday, October 10, 2014 8:45 PM
> To: Les Ginsberg (ginsberg); [e-mail]
> Subject: RE: New Version Notification for draft-ginsberg-isis-prefix-
> attributes-00.txt
> 
> Hi Les,
> 
> If I understand the P-flag correctly, it is specific to those sub-TLVs which is
> used for label/index advertisements, rather than to the reachability TLVs.
> As for how to determine whether a given node is a penultimate hop, it has
> been well addressed by the routable IP address sub-TLVs as defined in
> (https://tools.ietf.org/html/draft-xu-isis-routable-ip-address-01). Don't you
> think so?
> 
> Best regards,
> Xiaohu
> 
> > -----Original Message-----
> > From: Les Ginsberg (ginsberg) [mailto:[e-mail]]
> > Sent: Thursday, October 09, 2014 9:51 PM
> > To: Xuxiaohu; [e-mail]
> > Subject: RE: New Version Notification for
> > draft-ginsberg-isis-prefix-attributes-00.txt
> >
> > Xiaohu -
> >
> > Please read the description of the P-flag in Sections 2.1 and 2.1.1 of
> > http://www.ietf.org/id/draft-ietf-isis-segment-routing-extensions-02.txt
> 
> >    Les
> >
> >
> > > -----Original Message-----
> > > From: Xuxiaohu [mailto:[e-mail]]
> > > Sent: Wednesday, October 08, 2014 1:08 AM
> > > To: Les Ginsberg (ginsberg); [e-mail]
> > > Subject: RE: New Version Notification for draft-ginsberg-isis-prefix-
> > > attributes-00.txt
> > >
> > > Hi Les,
> > >
> > > I have read this draft and felt that the description of the use cases
> > > is not much clear. For instance, it said "There are existing use cases
> > > in which knowing additional attributes of a prefix is useful.  For
> > > example, it is useful to know whether an advertised prefix is directly
> > > connected to the advertising router or not.  In the case of [SR]
> > > knowing whether a prefix is directly connected or not determines what
> > > action should be taken as regards processing of labels associated with
> > > an incoming packet..."  Would you please further point to the exact
> > > place of the referenced SR draft (draft-
> > > ietf-isis-segment-routing-extensions-02) where it said that it's
> > > useful to know whether an advertised prefix is directly connected to
> > > the advertising router or not. Similarly, it would be better if you
> > > could give a more concrete use case where it is useful to know the
> > > source of a prefix advertisement when the advertisement has been
> leaked to
> > another level.
> > >
> > > Best regards,
> > > Xiaohu
> > >
> > >
> > >
> > > > -----Original Message-----
> > > > From: Isis-wg [mailto:[e-mail]] On Behalf Of Les
> > > Ginsberg
> > > > (ginsberg)
> > > > Sent: Tuesday, October 07, 2014 7:46 AM
> > > > To: [e-mail]
> > > > Subject: [Isis-wg] FW: New Version Notification for
> > > > draft-ginsberg-isis-prefix-attributes-00.txt
> > > >
> > > > This draft should be of interest to the WG.
> > > >
> > > >    Les
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: [e-mail] [mailto:[e-mail]]
> > > > Sent: Monday, October 06, 2014 4:45 PM
> > > > To: Stefano Previdi (sprevidi); Bruno Decraene; Clarence Filsfils;
> > > > Les
> > > Ginsberg
> > > > (ginsberg); Bruno Decraene; Stephane Litkowski; Clarence Filsfils;
> > > > Stefano Previdi (sprevidi); Les Ginsberg (ginsberg); Stephane
> > > > Litkowski
> > > > Subject: New Version Notification for
> > > > draft-ginsberg-isis-prefix-attributes-
> > > 00.txt
> > > >
> > > >
> > > > A new version of I-D, draft-ginsberg-isis-prefix-attributes-00.txt
> > > > has been successfully submitted by Les Ginsberg and posted to the
> > > > IETF repository.
> > > >
> > > > Name:		draft-ginsberg-isis-prefix-attributes
> > > > Revision:	00
> > > > Title:		IS-IS Prefix Attributes for Extended IP and IPv6
> Reachability
> > > > Document date:	2014-10-06
> > > > Group:		Individual Submission
> > > > Pages:		7
> > > > URL:
> > > > http://www.ietf.org/internet-drafts/draft-ginsberg-isis-prefix-attri
> > > > butes-
> > > 00.txt
> > > > Status:
> > > > https://datatracker.ietf.org/doc/draft-ginsberg-isis-prefix-attribut
> > > > es/
> > > > Htmlized:
> > > > http://tools.ietf.org/html/draft-ginsberg-isis-prefix-attributes-00
> > > >
> > > >
> > > > Abstract:
> > > >    This document introduces new sub-TLVs to support advertisement of
> > > >    prefix attribute flags and the source router id of the router which
> > > >    originated a prefix advertisement.
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > Please note that it may take a couple of minutes from the time of
> > > submission
> > > > until the htmlized version and diff are available at tools.ietf.org.
> > > >
> > > > The IETF Secretariat
> > > >
> > > > _______________________________________________
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> > > > [e-mail]
> > > > https://www.ietf.org/mailman/listinfo/isis-wg