Re: [Lsr] draft-bashandy-isis-srv6-extensions: Locator Leaking

Peter Psenak <ppsenak@cisco.com> Fri, 18 January 2019 08:47 UTC

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To: "Chengli (Cheng Li)" <chengli13@huawei.com>, "draft-bashandy-isis-srv6-extensions@ietf.org" <draft-bashandy-isis-srv6-extensions@ietf.org>
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From: Peter Psenak <ppsenak@cisco.com>
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Date: Fri, 18 Jan 2019 09:47:17 +0100
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Subject: Re: [Lsr] draft-bashandy-isis-srv6-extensions: Locator Leaking
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Hi Cheng,

please see inline:


On 18/01/2019 04:53 , Chengli (Cheng Li) wrote:
> Hi Peter,
>
> Thanks to your reply. Please see my reply inline [Cheng].
>
> Thanks,
> Cheng
>
>
> -----Original Message-----
> From: Peter Psenak [mailto:ppsenak@cisco.com]
> Sent: Thursday, January 17, 2019 3:26 PM
> To: Chengli (Cheng Li) <chengli13@huawei.com>;; draft-bashandy-isis-srv6-extensions@ietf.org
> Cc: lsr@ietf.org
> Subject: Re: draft-bashandy-isis-srv6-extensions: Locator Leaking
>
> Hi Cheng,
>
> On 17/01/2019 03:07 , Chengli (Cheng Li) wrote:
>> Hi Authors,
>>
>>
>>
>> In chapter 6.1 of draft-bashandy-isis-srv6-extensions-04,  it mentions
>> that Locator TLV can be leaked from level-2 to level-1.(See D bit)
>>
>>
>>
>> I am wondering that
>>
>> 1: Can the Locator be imported from another protocol? Like OSPF?
>
> what do you mean by "imported"?
>
> [Cheng] For example, a locator A::/64 is learned via OSPF, can it be imported to IS-IS? Maybe it  is called "copy"? or "leak"? Not sure about the term.

it's called "redistribution". Sure, nobody stops you to redistribute 
locators between protocols. Please note that it is not something that is 
specified by the IETF, because it's an internal implementation detail. 
 From protocol perspective, there is nothing specific needed to support 
that.

>
>
>>
>> 2: Will SRv6 End SID sub-TLV be carried when the locator TLV is leaked
>> from level-2 to Level-1?
>
> yes.
>
> [Cheng]If SRv6 End SID sub-TLVs are carried when the locator TLV is leaked  from level-2 to Level-1, does it mean  the locator TLV can not be summary? (Route aggregation)?

When you leak the locator TLV, you leak it as it is, including END SIDs.

When you summarize multiple locators, you would advertise only the 
summary prefix - in IP reachability TLV I would think.

This is the same as with SR MPLS. If you leak a prefix, you include 
SIDs. If you summarize at the area border, no SIDs are advertised with 
the summary itself.


thanks,
Peter



>
> thanks,
> Peter
>
>>
>>
>>
>> Thanks,
>>
>> Cheng
>>
>>
>>
>>
>>
>
> .
>