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RE : RE : [mpls] draft-vasseur-ccamp-te-router-info-00.txt clarificationneeded.
Hi Dillikar,
E = 1, so both trees are valid.
Regards,
JL
>-----Message d'origine-----
>De : Dillikar Satyanarayana-G19471 [mailto:satya@motorola.com]
>Envoyé : vendredi 8 octobre 2004 16:09
>À : LE ROUX Jean-Louis RD-CORE-LAN; mpls@ietf.org; mpls-ops@mplsrc.com
>Cc : ccamp@ops.ietf.org
>Objet : RE: RE : [mpls]
>draft-vasseur-ccamp-te-router-info-00.txt clarificationneeded.
>
>
>Hi JL,
> Thanks for your explanation. As the hardware data-plane
>branch capability is not known to CSPF
>Path-Computation-Engine(PCE). PCE only has to rely on E-bit
>and B-bit of the nodes.
> PCE computing trees T1 and T2 based on given R3 bit status.
>Please tell us which tree is valid and which tree is not
>valid and why?
>
>Tree T1: Ingress = R1 Egresses = R2,R3
>
> R1
> |
> R2--R3
>
>R3(E=1, B=0)
>
>
>Tree T2: Ingress = R1 Egresses = R2,R3
>
> R1
> |
> R2--R3
>
>R3(E=1, B=1)
>
>TIA,
>Satya
>
>> -----Original Message-----
>> From: mpls-bounces@lists.ietf.org
>> [mailto:mpls-bounces@lists.ietf.org] On Behalf Of LE ROUX
>> Jean-Louis RD-CORE-LAN
>> Sent: Friday, October 08, 2004 3:57 AM
>> To: Satyanarayana Dillikar; mpls@ietf.org; mpls-ops@mplsrc.com
>> Cc: ccamp@ops.ietf.org
>> Subject: RE : [mpls]
>> draft-vasseur-ccamp-te-router-info-00.txt clarificationneeded.
>>
>>
>> Hi Dillikar,
>>
>> Sorry for this delayed answer.
>> Thanks for these useful comments, that will help clarifying
>> this spec. Please see inline. Regards,
>>
>> JL
>>
>> PS: I'm copying ccamp
>>
>> >-----Message d'origine-----
>> >De : mpls-bounces@lists.ietf.org
>[mailto:mpls-bounces@lists.ietf.org]
>> >De la part de Satyanarayana Dillikar
>> >Envoyé : mercredi 6 octobre 2004 10:38
>> >À : mpls@ietf.org; mpls-ops@mplsrc.com
>> >Objet : [mpls] draft-vasseur-ccamp-te-router-info-00.txt
>> >clarificationneeded.
>> >
>> >
>> >Hi,
>> > We have some confusion in understanding the Data
>> >Plane Capability Flags (B-bit & E-bit) from
>> >draft-vasseur-ccamp-te-router-info-00.txt
>> >
>> >(a) Does E-bit ON implies B-bit ON always ? (assuming
>> >ON = set and OFF = unset).
>>
>> Basically bud (transit + Egress) capability requires some
>> branching in the data plane so in general E ON will imply B
>> ON, but note that these capabilities does not necessarily
>> reflect real hardware capabilities as they may be
>> activated/deactivated by the operator for various reasons. We
>> will clarify this point in next revision.
>>
>>
>> >(b) E-bit = ON & B-bit = OFF, is it a valid
>> >combination.
>>
>> Yes see above, there may be cases where the operator want to
>> deactivate branch capability on a node (He does't want that
>> the node act as a branch LSR), even if its data plane is
>> physically branch capable, but he allows the node to act as a
>> bud-LSR (transit + egress). This gives more operational flexibility.
>>
>> >(c) Please tell us the E-bit and B-bit status for a
>> >node which is a destination node but does not have
>> >branch capability.
>>
>> If its data plane is not branch capable then it will also
>> probably not be bud capable so
>> E = 0 and B = 0
>>
>> In return, if its data plane is branch capable but branch LSR
>> capability has been deactivated by configuration and bud-LSR
>> capability is activated, then E = 1 and B = 0
>>
>> >
>> >
>> >We are also curious to know
>> >(1)The idea behind combing two things (egress status & transit
>> >status) in a single E-bit. rather than making use of B-bit(branch)
>> >and having E-bit just for egress status.
>>
>> Remind that these capabilities are used for tree computation
>> purpose, and the egress is an entry
>> of the computation. So, IMHO it does't really make any sense
>> to advertise egress capability only.
>>
>> >(2) Why the TE Node Capability Descriptor TLV should
>> >have E-bit & how it should be used in CSPF path
>> >computation.
>>
>> This allows advertising if an LSR can be transit and egress.
>> This is particulary useful for steiner tree topologies.
>> See the following example:
>> Tree T: Ingress = R1 Egresses = R2, R3, R4
>>
>> R1
>> |
>> R2--R3---R4
>>
>> Such tree can be setup only if R3 has Egress + Transit capability.
>>
>>
>> Regards,
>>
>> JL
>>
>>
>>
>> >
>> >Thanks
>> >Satya
>> >
>> >
>> >
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