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Vivek Kumar | 18 Aug 2012 13:45
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Question regarding MPLS reserved label with ECMP

Hi ,
  I have one question regarding whether MPLS reserved label should be used or skipped when Transit LSR is
doing hashing on full label stack which has some reserved label.

   RFC 6391 , section 7 , says " Note that, depending on the number of labels hashed by the LSR, the
   inclusion of the Router Alert label may cause the OAM packet to be
   load-balanced to a different path from that taken by the data packets
   with identical flow and PW labels".

  The above comment implies that reserved label is used by LSR when doing hashing for ECMP. 

  Is there any other RFC which states what should be the correct behavior. 

  The draft " draft-ietf-mpls-entropy-label-05" section 4.3 , says reserved label should not be used by LSR
when doing hashing on label stack.

Regards,
Vivek 

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Kireeti Kompella | 20 Aug 2012 20:10
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Re: Question regarding MPLS reserved label with ECMP

On Aug 18, 2012, at 4:45 , Vivek Kumar wrote:

> Hi ,
>  I have one question regarding whether MPLS reserved label should be used or skipped when Transit LSR is
doing hashing on full label stack which has some reserved label.

draft-ietf-mpls-entropy-label, section 4.3:

   If a transit LSR recognizes the ELI, it MAY choose to load balance
   solely on the following label (the EL); otherwise, it SHOULD use as
   much of the whole label stack as feasible as keys for the load
   balancing function, with the exception that reserved labels MUST NOT
   be used.

>   RFC 6391 , section 7 , says " Note that, depending on the number of labels hashed by the LSR, the
>   inclusion of the Router Alert label may cause the OAM packet to be
>   load-balanced to a different path from that taken by the data packets
>   with identical flow and PW labels".
>
>  The above comment implies that reserved label is used by LSR when doing hashing for ECMP.
>
>  Is there any other RFC which states what should be the correct behavior.
>
>  The draft " draft-ietf-mpls-entropy-label-05" section 4.3 , says reserved label should not be used by
LSR when doing hashing on label stack.
>
>
> Regards,
> Vivek
>
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Curtis Villamizar | 21 Aug 2012 15:52

Re: Question regarding MPLS reserved label with ECMP


In message <CE716035-DFC3-47A9-8C80-00A9B783680A <at> juniper.net>
Kireeti Kompella writes:

> On Aug 18, 2012, at 4:45 , Vivek Kumar wrote:
>  
> > Hi ,
> >  I have one question regarding whether MPLS reserved label should be used or skipped when Transit LSR is
doing hashing on full label stack which has some reserved label.
>  
> draft-ietf-mpls-entropy-label, section 4.3:
>  
>    If a transit LSR recognizes the ELI, it MAY choose to load balance
>    solely on the following label (the EL); otherwise, it SHOULD use as
>    much of the whole label stack as feasible as keys for the load
>    balancing function, with the exception that reserved labels MUST NOT
>    be used.
>  
> >   RFC 6391 , section 7 , says " Note that, depending on the number of labels hashed by the LSR, the
> >   inclusion of the Router Alert label may cause the OAM packet to be
> >   load-balanced to a different path from that taken by the data packets
> >   with identical flow and PW labels".
> >
> >  The above comment implies that reserved label is used by LSR when doing hashing for ECMP.
> >
> >  Is there any other RFC which states what should be the correct behavior.
> >
> >  The draft " draft-ietf-mpls-entropy-label-05" section 4.3 , says reserved label should not be used by
LSR when doing hashing on label stack.
> >
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Kireeti Kompella | 21 Aug 2012 22:27
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Re: Question regarding MPLS reserved label with ECMP

On Aug 21, 2012, at 6:52 , Curtis Villamizar wrote:

> In message <CE716035-DFC3-47A9-8C80-00A9B783680A <at> juniper.net>
> Kireeti Kompella writes:
> 
>> On Aug 18, 2012, at 4:45 , Vivek Kumar wrote:
>> 
>>> Hi ,
>>> I have one question regarding whether MPLS reserved label should be used or skipped when Transit LSR is
doing hashing on full label stack which has some reserved label.
>> 
>> draft-ietf-mpls-entropy-label, section 4.3:
>> 
>>   If a transit LSR recognizes the ELI, it MAY choose to load balance
>>   solely on the following label (the EL); otherwise, it SHOULD use as
>>   much of the whole label stack as feasible as keys for the load
>>   balancing function, with the exception that reserved labels MUST NOT
>>   be used.
>> 
>>>  RFC 6391 , section 7 , says " Note that, depending on the number of labels hashed by the LSR, the
>>>  inclusion of the Router Alert label may cause the OAM packet to be
>>>  load-balanced to a different path from that taken by the data packets
>>>  with identical flow and PW labels".
>>> 
>>> The above comment implies that reserved label is used by LSR when doing hashing for ECMP.
>>> 
>>> Is there any other RFC which states what should be the correct behavior.
>>> 
>>> The draft " draft-ietf-mpls-entropy-label-05" section 4.3 , says reserved label should not be used by
LSR when doing hashing on label stack.
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Bhargav Bhikkaji | 22 Aug 2012 01:55
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Re: Question regarding MPLS reserved label with ECMP

Hi Kireeti,

Liked the idea of having entropy label, something similar to having flow-label for load balancing in ipv6.
In case of transit LSR (transit is a different vendor to ingress LSR), where ELI is recognized and chooses
to load balance solely on label following EL. The ingress would create entropy label based on it's load
balancing function and the transit would use this label for it's hasing functions, as both
implementations are different and single hashing algorithm does not load balance equally for all types
of traffic, is there a possibility of un-equal loadbalancing observed in the transit ? 

Thanks
Bhargav
________________________________________
From: mpls-bounces <at> ietf.org [mpls-bounces <at> ietf.org] On Behalf Of Kireeti Kompella [kireeti <at> juniper.net]
Sent: Wednesday, August 22, 2012 1:57 AM
To: curtis <at> occnc.com
Cc: mpls <at> ietf.org; Vivek Kumar
Subject: Re: [mpls] Question regarding MPLS reserved label with ECMP

On Aug 21, 2012, at 6:52 , Curtis Villamizar wrote:

> In message <CE716035-DFC3-47A9-8C80-00A9B783680A <at> juniper.net>
> Kireeti Kompella writes:
>
>> On Aug 18, 2012, at 4:45 , Vivek Kumar wrote:
>>
>>> Hi ,
>>> I have one question regarding whether MPLS reserved label should be used or skipped when Transit LSR is
doing hashing on full label stack which has some reserved label.
>>
>> draft-ietf-mpls-entropy-label, section 4.3:
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