Re: [OSPF] OSPFv2 SR draft

Peter Psenak <ppsenak@cisco.com> Mon, 22 August 2016 07:32 UTC

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Date: Mon, 22 Aug 2016 09:31:57 +0200
From: Peter Psenak <ppsenak@cisco.com>
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To: Chris Bowers <cbowers@juniper.net>, OSPF List <ospf@ietf.org>
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Subject: Re: [OSPF] OSPFv2 SR draft
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Chris,

what about this to be added in the Section 3.1:


"A router receiving a Prefix-SID (defined in section 5) from a remote 
node and with an SR algorithm value that such remote node has not 
advertised in the SR-Algorithm sub-TLV MUST ignore the Prefix-SID sub-TLV."

thanks,
Peter


On 19/08/16 23:33 , Chris Bowers wrote:
> Peter,
>
> Please share the updated text that you plan to use with the WG, since this is a reasonably significant clarification.
>
> Thanks,
> Chris
>
> -----Original Message-----
> From: Peter Psenak [mailto:ppsenak@cisco.com]
> Sent: Tuesday, August 16, 2016 10:02 AM
> To: Chris Bowers <cbowers@juniper.net>; OSPF List <ospf@ietf.org>
> Subject: Re: [OSPF] OSPFv2 SR draft
>
> Hi Chris,
>
> I'll update the draft along those lines.
>
> thanks,
> Peter
>
>
> On 16/08/16 16:02 , Chris Bowers wrote:
>> Peter,
>>
>> I suggest changing the paragraph to read as below to make this clearer.
>>
>> =====
>>      The SR-Algorithm Sub-TLV is optional.  It MAY only be advertised once
>>      in the Router Information Opaque LSA.  If the SID/Label Range TLV, as
>>      defined in Section 3.2, is advertised, then the SR-Algorithm TLV MUST
>>      also be advertised.  If a router C advertises a Prefix-SID sub-TLV for algorithm X
>>      but does not advertise the SR-Algorithm Sub-TLV with algorithm X, then
>>      a router receiving that advertisement MUST ignore the Prefix-SID
>>      advertisement from router C.  If router B does not advertise the
>>      SR-Algorithm TLV for algorithm X, then other routers should not
>>      forward traffic destined for a prefix-SID for algorithm X advertised by
>>      some router D using a path that would require router B to forward traffic using
>>      algorithm X.
>> =====
>>
>> Thanks,
>> Chris
>>
>>
>>
>> -----Original Message-----
>> From: Peter Psenak [mailto:ppsenak@cisco.com]
>> Sent: Monday, August 15, 2016 6:40 AM
>> To: Chris Bowers <cbowers@juniper.net>; OSPF List <ospf@ietf.org>
>> Subject: Re: [OSPF] OSPFv2 SR draft
>>
>> Hi Chris,
>>
>> sorry for the delay, I was on PTO during last two weeks.
>> Please see inline:
>>
>> On 03/08/16 16:45 , Chris Bowers wrote:
>>> Peter,
>>>
>>> Taking a looking at the whole paragraph into this sentence was added,
>>> I am not sure how to interpret it.
>>>
>>>       The SR-Algorithm Sub-TLV is optional.  It MAY only be advertised once
>>>       in the Router Information Opaque LSA.  If the SID/Label Range TLV, as
>>>       defined in Section 3.2, is advertised, then the SR-Algorithm TLV MUST
>>>       also be advertised.  If the SR-Algorithm TLV is not advertised by the
>>>       node, such node is considered as not being segment routing capable.
>>>
>>> Is this sentence intended to imply that if a router does not
>>> advertise the SR-Algorithm TLV including algorithm X, then any
>>> prefix-SIDs for algorithm X advertised by that router will be ignored by other routers?
>>
>> in OSPF we do not have the SR capability TLV. We use SR-Algorithm TLV
>> for that purpose. So if a router does not advertise the SR-Algorithm
>> TLV for algorithm X, other routers should not send any SR traffic
>> using SIDs that were advertised for algorithm X.
>>
>> If the router does not advertise any SR Algorithm TLV, then the node
>> is not SR capable and no SR traffic should be forwarded to such a node.
>>
>> thanks,
>> Peter
>>
>>
>>>
>>> If this is the intention, then it would be better to state is more explicitly.
>>>
>>> If not, then the intended meaning should be clarified.
>>>
>>> Thanks,
>>> Chris
>>>
>>>
>>> -----Original Message-----
>>> From: OSPF [mailto:ospf-bounces@ietf.org] On Behalf Of Peter Psenak
>>> Sent: Friday, July 22, 2016 3:30 AM
>>> To: OSPF List <ospf@ietf.org>
>>> Subject: [OSPF] OSPFv2 SR draft
>>>
>>> Hi All,
>>>
>>> following text has been added in the latest revision of the OSPFv2 SR
>>> draft, section 3.1.
>>>
>>> "If the SR-Algorithm TLV is not advertised by node, such node is
>>> considered as not being segment routing capable."
>>>
>>> Please let us know if there are any concerns regarding this addition.
>>>
>>> thanks,
>>> Peter
>>>
>>> _______________________________________________
>>> OSPF mailing list
>>> OSPF@ietf.org
>>> https://www.ietf.org/mailman/listinfo/ospf
>>> .
>>>
>>
>> .
>>
>
> .
>