[j-nsp] SRLGs in Inter-Area LSPs

[Łukasz Dudziński]

Hi,

I do not have an experience in multi-area MPLS techniques, so I'm not 
able to help you too much in that matter. But I'm sure that typically 
MPLS Traffic Engineering is restricted to single area of IGP protocol. 
If I understood your mail correctly you try to create a CSPF-based RSVP 
LSP between different IGP areas, which is not possible "just like that". 
That is because MPLS TE relies on IGP TE database, which (like the link 
state database) is restricted to single IGP area. TE-DB is an extension 
of link state DB. Such information like Admin Groups, SRLG membership or 
BW reservation are stored in TE database. If size of your network force 
you to use IGP hierarchy I suggest you to take a look on such things 
like LDP-over-RSVP, Seamless MPLS or BGP Labelled Unicast.

Lukasz


On 2012-05-18 09:17, Caillin Bathern wrote:
> Hi All,
>
>
>
> I posted this to the J-Net forums but no luck.
>
>
>
> Just wondering if SRLGs are carried through between IGP areas, both for
> OSPF and for IS-IS?
>
>
>
> The scenario for this would be passing a cspf routed RSVP LSP from PE1
> in Area 1 through to PE2 in Area 2. We would maintain a secondary
> standby LSP path for this traffic with exclude-srlg enabled.
>
> Assuming that the primary path takes the IGP routed path PE1 - ABR1 -
> ABR3 - PE2 then the secondary path will take the path PE1 - ABR2 -
> where?
>
> If SRLGs are carried through by the IGP then then the path should go PE1
> - ABR2 - ABR4 - PE2, however if the SRLGs are not carried through then
> the IGP could in make the secondary path PE1 - ABR2 - ABR3 - PE2 which
> obviously is not a great standby secondary path...
>
>
>
>          /--- ABR1 ---| |--- ABR3 ---\
>
> PE1 (Area1) | Area 0 | (Area2) PE2
>
>          \--- ABR2 ---| |--- ABR4 ---/
>
>
>
>
>
> If anybody knows this scenario and can shed some insight it would be
> greatly appreciated.
>
> Cheers,
>
> Caillin
>
>
>
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