Re: [spring] About draft-ali-spring-srv6-oam-00

[Robert Raszuk]

Hi Loa,

Is there any known implementations you can show here which builds its IPv6
load balancing hash bases on the *variable length* IPv6 extension headers
content ? Or is your concern simply a speculation ? :)

As Zafar already indicated bunch of IETF work went into proposing to use
flow label which is part of base IPv6 header (fixed 40 bytes) - to name a
few RFC6437, RFC6438, RFC6294 etc ... for that very purpose.

So at min if someone indeed wants to expose himself and construct a hash
based on the variable length fields a knob should be provided to allow to
configure such network element to skip extension headers.

Regards,
Robert.


On Sat, Jun 2, 2018 at 10:21 AM, Loa Andersson  wrote:

> Zafar,
>
> My concern is that any load balancing tool might hash on the field where
> you have the O-bit, if it does OAM traffic and normal payload traffic
> will take different paths through the network.
>
> How do you guarantee  this this will not happen?
>
> /Loa
>
> On 2018-05-29 19:11, Zafar Ali (zali) wrote:
>
>> Hi Loa,
>>
>> Thanks for your question.
>>
>> O-bit "move" from SRH draft to this SRv6 OAM draft is part of a comment
>> received an agreement made during the LC of the SRH draft. Please review
>> the mail chain https://www.ietf.org/mail-arch
>> ive/web/ipv6/current/msg30131.html. There was never a suggestion or
>> agreement to "remove" O-bit or SRH.Flags field.
>>
>> Load balancing and ECMP in an SRv6 network are explained in
>> https://tools.ietf.org/html/draft-ietf-6man-segment-routing-
>> header-13#section-4.4. An implementation is expected to use the minimum
>> of (source, dest) address and flow label in the outer IPv6 header to
>> compute the hash. RFC6437 describes the use of flow labels to compute a
>> hash for IPv6 packets.
>>
>> Thanks
>>
>> Regards … Zafar
>>
>> *From: *Loa Andersson 
>> *Date: *Tuesday, May 29, 2018 at 9:48 AM
>> *To: *Huzhibo , "Zafar Ali (zali)" ,
>> "draft-ali-spring-srv6-...@ietf.org" ,
>> "spring@ietf.org" 
>> *Cc: *Lizhenbin , Yangang 
>> *Subject: *Re: [spring] About draft-ali-spring-srv6-oam-00
>>
>> Folks,
>>
>> I thought we had an agreement to remove the O-bit. As ZhiBo Hu points
>>
>> out other drafts drops it.
>>
>> The obvious reason to not use an O-bit is that if it ever is part of
>>
>> what an multipath functions hash on it will csue OAM traffic and
>>
>> "normal" traffic to use different paths. This defeats the idea with
>>
>> OAM traffic.
>>
>> /Loa
>>
>> On 2018-05-16 06:56, Huzhibo wrote:
>>
>> Hi,
>>
>> draft-ali-spring-srv6-oam-00 says The OAM packets are identified by
>>
>> setting the O-bit in SRH，But I Notice the latest
>>
>> I-D.6man-segment-routing-headerhas removed O-bit in the SRH extension
>>
>> header. I want to confirm that draft-ali-spring-srv6-oam-00 will also
>>
>> remove o-bit or keep the o-bit in the later version?
>>
>> Ths
>>
>> ZhiBo Hu
>>
>> ___
>>
>> spring mailing list
>>
>> spring@ietf.org
>>
>> https://www.ietf.org/mailman/listinfo/spring
>>
>> --
>>
>> Loa Anderssonemail: l...@pi.nu
>>
>> Senior MPLS Expert
>>
>> Bronze Dragon Consulting phone: +46 739 81 21 64
>>
>>
>>
>> ___
>> spring mailing list
>> spring@ietf.org
>> https://www.ietf.org/mailman/listinfo/spring
>>
>>
> --
>
>
> Loa Anderssonemail: l...@pi.nu
> Senior MPLS Expert
> Bronze Dragon Consulting phone: +46 739 81 21 64
>
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Re: [spring] About draft-ali-spring-srv6-oam-00

[Loa Andersson]

Zafar,

My concern is that any load balancing tool might hash on the field where
you have the O-bit, if it does OAM traffic and normal payload traffic
will take different paths through the network.

How do you guarantee  this this will not happen?

/Loa

On 2018-05-29 19:11, Zafar Ali (zali) wrote:

Hi Loa,

Thanks for your question.

O-bit "move" from SRH draft to this SRv6 OAM draft is part of a comment 
received an agreement made during the LC of the SRH draft. Please review 
the mail chain 
https://www.ietf.org/mail-archive/web/ipv6/current/msg30131.html. There 
was never a suggestion or agreement to "remove" O-bit or SRH.Flags field.


Load balancing and ECMP in an SRv6 network are explained in 
https://tools.ietf.org/html/draft-ietf-6man-segment-routing-header-13#section-4.4. 
An implementation is expected to use the minimum of (source, dest) 
address and flow label in the outer IPv6 header to compute the hash. 
RFC6437 describes the use of flow labels to compute a hash for IPv6 
packets.


Thanks

Regards … Zafar

*From: *Loa Andersson 
*Date: *Tuesday, May 29, 2018 at 9:48 AM
*To: *Huzhibo , "Zafar Ali (zali)" , 
"draft-ali-spring-srv6-...@ietf.org" 
, "spring@ietf.org" 

*Cc: *Lizhenbin , Yangang 
*Subject: *Re: [spring] About draft-ali-spring-srv6-oam-00

Folks,

I thought we had an agreement to remove the O-bit. As ZhiBo Hu points

out other drafts drops it.

The obvious reason to not use an O-bit is that if it ever is part of

what an multipath functions hash on it will csue OAM traffic and

"normal" traffic to use different paths. This defeats the idea with

OAM traffic.

/Loa

On 2018-05-16 06:56, Huzhibo wrote:

Hi,

draft-ali-spring-srv6-oam-00 says The OAM packets are identified by

setting the O-bit in SRH，But I Notice the latest

I-D.6man-segment-routing-headerhas removed O-bit in the SRH extension

header. I want to confirm that draft-ali-spring-srv6-oam-00 will also

remove o-bit or keep the o-bit in the later version?

Ths

ZhiBo Hu

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--

Loa Anderssonemail: l...@pi.nu

Senior MPLS Expert

Bronze Dragon Consulting phone: +46 739 81 21 64



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--


Loa Anderssonemail: l...@pi.nu
Senior MPLS Expert
Bronze Dragon Consulting phone: +46 739 81 21 64

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