[j-nsp] SRLGs in Inter-Area LSPs

[Łukasz Dudziński]

Hi,

I didn't know that option before. It seems, it can be very useful in 
hierarchic networks. It's a pity that it is poor documented. But it 
should be possible to use SRLG since ERO extension is calculated by the 
ABR and the ABR has access to TED in both areas. Please, share your lab 
results.

Lukasz

On 2012-05-20 08:10, Caillin Bathern wrote:
> Hi Lukasz,
>
> Thanks for your response.
>
> I agree that the TED is restricted to an ospf area for CSPF calculation however using the expand-loose-hop option on the ABRs should enable a cspf LSP to be set up to the remote area assuming that the ABRs are loose hops.  The problem I am having is I am not yet sure if the CSPF conditions (admin groups, SRLGs, etc) will be applied when that loose-hop expansion (cspf calculation by the ABR to reach the next ABR) is made by the ABR.
>
> BGP-LU and the use of NHS attribute for scaling beyond a single area are definitely in play for multi-point VPNs however for any point-to-point L2VPNs we feel it would be much easier to generate an end-to-end dynamic LSP instead.
>
> I am hoping to try this in the lab soon but I was hoping for any insight list members might have for this.
>
> Cheers,
> Caillin
>
> -----Original Message-----
> From: juniper-nsp-bounces at puck.nether.net [mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of Lukasz Dudzinski
> Sent: Sunday, 20 May 2012 7:22 AM
> To: juniper-nsp at puck.nether.net
> Subject: Re: [j-nsp] SRLGs in Inter-Area LSPs
>
> 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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