The MPLS-OPS Archive

["HariKishan" <harikishan.desineni@ericsson.com>]

Eric,
	The LDP RFC3036 NH.2 states that label should be removed
from forwarding/switching use when a change in FEC next hop
is detected.

But "draft-ietf-mpls-ldp-state-04" state machine seems to
operate in a different way. The LDP state machine retains
the label till the local/global repair completes/fails. This
behavior is different from the described NH algorithm in RFC 3036.

I think the state machine behavior should strictly follow whatever
is stated in RFC3036!!! Is it really a bug in the draft or did I 
miss something!!

thanks,
Kishan
---------------------------------
HariKishan Desineni,
Ericsson Inc,
Santabarbara,
California - 93117
Office:(805) 562 6419
Home:(805) 562 8841



> -----Original Message-----
> From: owner-mpls@UU.NET [mailto:owner-mpls@UU.NET]On Behalf 
> Of Eric Gray
> Sent: Monday, September 10, 2001 6:43 AM
> To: Hemant P. Kelkar
> Cc: mpls-ops@mplsrc.com; mpls@UU.NET
> Subject: Re: Next hop Change
> 
> 
> Hemant,
> 
>     This is an implementation detail.  :-)
> 
>     When an LSP is established, the local LSR is able to 
> determine whether
> or not it can (or should) detect a change in optimal next 
> hop.  If the LSP is
> pinned, or the next hop is a strict hop that is not an 
> abstract node (i.e. - an
> AS or address prefix), then the LSR cannot and should not 
> attempt to find
> a better next hop for the life of the LSP.  Otherwise, the 
> LSR needs to do
> whatever implementation specific trick is required in order 
> to ensure that
> it is notified by the appropriate software entity (e.g. - 
> routing) when the
> 'best path' to the LSP next hop (not necessarily the same 
> as a routing next
> hop, for instance), or LSP destination, changes.
> 
>     This is not hard to do.
> 
> --
> Eric Gray
> 
> You wrote:
> 
> > Hi Everybody,
> > This is regarding the Next Hop change in the LDP state Machine.
> > "draft-ietf-mpls-ldp-state-04" states that, the LSR can 
> be configured as
> > either "local repair" or "global repair". How does the 
> LSR detects new
> > better next hops ? Which mechanism does it employ to 
> discover new paths,
> > other than LDP advertaisements ?
> >
> > Regards,
> > Hemant
> 
> 

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