The MPLS WG Archive

[Shahram Davari <Shahram_Davari@pmc-sierra.com>]

SE is for BW sharing. I could send 2 labels to H in SE mode.

-Shahram

> -----Original Message-----
> From: Sundara Murugan [mailto:smurugan@riverstonenet.com]
> Sent: Monday, August 12, 2002 3:02 PM
> To: Shahram Davari; mpls@UU.net
> Subject: RE: fast-reroute merging
> 
> 
> Shahram,
> 
> Let us assume that detours from B and C don't merge at H. But 
> these two LSPs share the same link between H-I. The at I 
> there will be 2 detour LSP (B to D and another from C to E). 
> 
> If the detour LSPs use SE filter, then the RESV message from 
> I to H can specify only one filter (Session + sender of all 
> the detours will be the same) and only one Label. Which label 
> does I select?
> 
> -sundara
> 
> -----Original Message-----
> From: Shahram Davari [mailto:Shahram_Davari@pmc-sierra.com]
> Sent: Monday, August 12, 2002 11:45 AM
> To: Sundara Murugan; mpls@UU.net
> Subject: RE: fast-reroute merging
> 
> 
> Sundara,
> 
> I think the shortest ERO is only a suggested example. and not 
> a standard rule.
> 
> 
> 
>                 G----H----I--\
>                 |    |    |   \
>            A----B----C----D----E---F
> 
> 
> I think no merging should happen in the G, H and I LSRs. The 
> reason is that
> may be B has calculated the route B-G-H-I-D-E-F assuming some 
> BW restrictions, etc.
> We don't want H to change that to B-G-H-I-E-F.
> 
> Also since each PLR does an independent ERO calculation, it 
> is quite possible 
> for C to compute computes the path as being 
> C-H-I-D-J-K-M-N-... Clearly C's detour should
> not be merged with B's detour here.
> 
> If we have rule changed to "for merging the path messages 
> should have the same ERO",
> then we won't have such a problem.
> 
> 
> -Shahram
> 
> > -----Original Message-----
> > From: Sundara Murugan [mailto:smurugan@riverstonenet.com]
> > Sent: Monday, August 12, 2002 2:22 PM
> > To: Shahram Davari; mpls@UU.net
> > Subject: RE: fast-reroute merging
> > 
> > 
> > Shahram,
> > 
> > Section 5.3.1 says that the MP selects the shorter ERO path 
> > length. This may not be correct.
> > 
> > If there are other routers between I and E, then the ERO 
> > lenght of the detour from C could be more than the ERO lenght 
> > of the detour from B. If you go by the rule, then H will 
> > merge the detours from B & C and establish a detour to D. 
> > Then the detour from C will not avoid its next-hop D. So 
> > there won't be a detour from C.
> > 
> > So the MP has to select the detour which merges with the main 
> > LSP that is closer to the egress router.
> > 
> > -sundara 
> > 
> > 
> > -----Original Message-----
> > From: Shahram Davari [mailto:Shahram_Davari@pmc-sierra.com]
> > Sent: Monday, August 12, 2002 10:57 AM
> > To: Sundara Murugan; mpls@UU.net
> > Subject: RE: fast-reroute merging
> > 
> > 
> > Sundara,
> > 
> > This is exactly the same question that I asked in another email:
> > 
> > "Since as stated in section 7, each PLR has option to apply 
> > its own constraints, then each PLR  may reach to a different 
> > backup-path ERO for the same flow. Assuming that the EROs 
> > have a single link (the downstream link of an MP LSP) in 
> > common, isn't it wrong for an MP LSR to merge those Path messages?"
> > 
> > 
> > I think the solution is to require the same ERO for merging.
> > 
> > Yours,
> > -Shahram
> > 
> > 
> > 
> > 
> > > -----Original Message-----
> > > From: Sundara Murugan [mailto:smurugan@riverstonenet.com]
> > > Sent: Monday, August 12, 2002 1:36 PM
> > > To: mpls@UU.net
> > > Subject: fast-reroute merging
> > > 
> > > 
> > > Section 5.3.1 in draft-ietf-mpls-rsvp-lsp-fastreroute-00.txt  
> > > explains merging procedure. In the fig below if there is a 
> > > link between I and F then D will have a detour D-I-F. In this 
> > > case how router I (the MP) handles detour LSPs from B, C and D?
> > > 
> > > -sundara
> > > 
> > > ------
> > > 
> > > 5.3.1. An Example on Path Message Merging
> > > 
> > > Consider the following example:
> > > 
> > > 
> > >                 G----H----I--\
> > >                 |    |    |   \
> > >            A----B----C----D----E---F
> > > 
> > > 
> > >    The protected LSP is A-B-C-D-E-F. After running CSPF, let 
> > > the detour
> > >    ERO from B be B-G-H-I-D-E-F, and the detour ERO from C be 
> > > C-H-I-E-F.
> > > 
> > >    H will receive Path messages that have the same SESSION and
> > > 
> > > 
> > > 
> > 
>