Hi Bruno,
On 12/05/2021 09:51, bruno.decra...@orange.com wrote:
Hi Xuesong,
Clarification question: are you talking about interoperability (between
two nodes) or compliancy (between an implementation and the RFC)?
I'm afraid the two are related. If we mandate the Prefix Attribute
Sub-TLV inside the Locator TLV, we would have to say that the Locator
TLV without the Prefix Attribute Sub-TLV MUST be ignored. As a result,
implementations that do not send the Prefix Attribute Sub-TLV would not
just be not compliant, but would also not interoperate with the ones
that follow the specification.
thanks,
Peter
If the former, could you please spell out the interop issue?
Thanks,
Best regards,
--Bruno
*From:*Lsr [mailto:lsr-boun...@ietf.org] *On Behalf Of *Gengxuesong
(Geng Xuesong)
*Sent:* Wednesday, May 12, 2021 9:16 AM
*To:* Les Ginsberg (ginsberg) <ginsb...@cisco.com>; Shraddha Hegde
<shraddha=40juniper....@dmarc.ietf.org>; Alvaro Retana
<aretana.i...@gmail.com>; Peter Psenak (ppsenak) <ppse...@cisco.com>;
lsr@ietf.org
*Cc:* cho...@chopps.org; draft-ietf-lsr-isis-srv6-extensi...@ietf.org;
Van De Velde, Gunter (Nokia - BE/Antwerp) <gunter.van_de_ve...@nokia.com>
*Subject:* Re: [Lsr] Last Call:
<draft-ietf-lsr-isis-srv6-extensions-14.txt> (IS-IS Extension to Support
Segment Routing over IPv6 Dataplane) to Proposed Standard
Hi Les,
Prefix Attributes sub-TLV is necessary when locator is leaked.
So we are not against Prefix Attribute sub-TLV implementation. We just
propose to keep it optional (“should” rather than “must”) for
interoperability.
Best
Xuesong
*From:*Les Ginsberg (ginsberg) [mailto:ginsb...@cisco.com]
*Sent:* Wednesday, May 12, 2021 6:29 AM
*To:* Shraddha Hegde <shraddha=40juniper....@dmarc.ietf.org
<mailto:shraddha=40juniper....@dmarc.ietf.org>>; Alvaro Retana
<aretana.i...@gmail.com <mailto:aretana.i...@gmail.com>>; Peter Psenak
(ppsenak) <ppse...@cisco.com <mailto:ppse...@cisco.com>>; lsr@ietf.org
<mailto:lsr@ietf.org>; Gengxuesong (Geng Xuesong)
<gengxues...@huawei.com <mailto:gengxues...@huawei.com>>
*Cc:* cho...@chopps.org <mailto:cho...@chopps.org>;
draft-ietf-lsr-isis-srv6-extensi...@ietf.org
<mailto:draft-ietf-lsr-isis-srv6-extensi...@ietf.org>; Van De Velde,
Gunter (Nokia - BE/Antwerp) <gunter.van_de_ve...@nokia.com
<mailto:gunter.van_de_ve...@nokia.com>>
*Subject:* RE: [Lsr] Last Call:
<draft-ietf-lsr-isis-srv6-extensions-14.txt> (IS-IS Extension to Support
Segment Routing over IPv6 Dataplane) to Proposed Standard
Shraddha/ Xuesong –
Since Prefix Attributes sub-TLV is required for correct operation when a
Locator is leaked, would it be safe to assume that your implementations
either do not leak Locators or you advise your customers not to deploy
this feature with multiple levels?
The problem with allowing the sub-TLV to be optional is that if the
sub-TLV is omitted you cannot tell whether the Locator has been leaked –
so you don’t know whether you have a problem or not.
The safest thing to do is require prefix-attributes sub-TLV always –
then you can guarantee that if the prefix is leaked the necessary
information will be present.
Anything else leaves us vulnerable.
We all appreciate interoperability considerations, but frankly this is a
gap that needs to be closed to support correct operation.
Les
*From:*Lsr <lsr-boun...@ietf.org <mailto:lsr-boun...@ietf.org>> *On
Behalf Of *Shraddha Hegde
*Sent:* Tuesday, May 11, 2021 8:21 AM
*To:* Alvaro Retana <aretana.i...@gmail.com
<mailto:aretana.i...@gmail.com>>; Peter Psenak (ppsenak)
<ppse...@cisco.com <mailto:ppse...@cisco.com>>; lsr@ietf.org
<mailto:lsr@ietf.org>
*Cc:* cho...@chopps.org <mailto:cho...@chopps.org>;
draft-ietf-lsr-isis-srv6-extensi...@ietf.org
<mailto:draft-ietf-lsr-isis-srv6-extensi...@ietf.org>; Van De Velde,
Gunter (Nokia - BE/Antwerp) <gunter.van_de_ve...@nokia.com
<mailto:gunter.van_de_ve...@nokia.com>>
*Subject:* Re: [Lsr] Last Call:
<draft-ietf-lsr-isis-srv6-extensions-14.txt> (IS-IS Extension to Support
Segment Routing over IPv6 Dataplane) to Proposed Standard
Juniper has an implementation of SRv6 that does not support Prefix
attributes sub-tlv in locator TLV.
We would prefer not to change the optional sub-TLV to MUST.
Rgds
Shraddha
Juniper Business Use Only
*From:*Lsr <lsr-boun...@ietf.org <mailto:lsr-boun...@ietf.org>> *On
Behalf Of *Alvaro Retana
*Sent:* Friday, May 7, 2021 7:23 PM
*To:* Peter Psenak <ppse...@cisco.com <mailto:ppse...@cisco.com>>;
lsr@ietf.org <mailto:lsr@ietf.org>
*Cc:* cho...@chopps.org <mailto:cho...@chopps.org>;
draft-ietf-lsr-isis-srv6-extensi...@ietf.org
<mailto:draft-ietf-lsr-isis-srv6-extensi...@ietf.org>; Van De Velde,
Gunter (Nokia - BE/Antwerp) <gunter.van_de_ve...@nokia.com
<mailto:gunter.van_de_ve...@nokia.com>>
*Subject:* Re: [Lsr] Last Call:
<draft-ietf-lsr-isis-srv6-extensions-14.txt> (IS-IS Extension to Support
Segment Routing over IPv6 Dataplane) to Proposed Standard
*[External Email. Be cautious of content]*
On May 3, 2021 at 5:17:58 AM, Peter Psenak wrote:
Technically I agree with you and if everybody agrees, I'm fine to
enforce the presence of the Prefix Attribute Flags TLV in the Locator TLV.
So...what does everyone else think?
We need to close on this point before the IESG evaluates the document.
I'm requesting it to be put on the May/20 telechat, which means that we
should have a resolution and updated draft by the end of next week.
Thanks!
Alvaro.
On May 3, 2021 at 5:17:58 AM, Peter Psenak (ppse...@cisco.com
<mailto:ppse...@cisco.com>) wrote:
Hi Gunter,
Prefix Attribute Flags Sub-TLV has been defined as an optional Sub-TLV.
The problem you describe is not specific to Locator TLV, same
applies to
regular IPv4/v6 prefixes (forget SR MPLS for a while) - if the Prefix
Attribute Flags TLV is not included, one can not tell whether the
prefix
has been propagated (L1->L2) or generated as a result of the local
interface attached on the originator. Same applies to redistribution
and
R-flag for IPv4 prefix TLVs.
SRv6 Locator TLV has been defined a while back and the Prefix Attribute
Flags Sub-TLV has always been an optional Sub-TLV of it. I'm not
sure we
can start to mandate the Prefix Attribute Flags TLV at this point.
Technically I agree with you and if everybody agrees, I'm fine to
enforce the presence of the Prefix Attribute Flags TLV in the
Locator TLV.
thanks,
Peter
On 03/05/2021 10:45, Van De Velde, Gunter (Nokia - BE/Antwerp) wrote:
> Hi Peter, All,
>
> Could we update to "draft-ietf-lsr-isis-srv6-extensions" that the prefix-attribute tlv is mandatory when a locator is redistributed?
>
> Why?
> *When calculating a LFA for an SRv6 End.SID we better know if the locator has been redistributed or not for a correct operation.
>
> Reasoning:
> * A locator has the D bit. This one is set when we redistribute from L2 to L1.
> ** So this end-sid will not be used as we know that it is redistributed.
>
> * In the other direction (L1-L2), we only know that a locator is redistributed from L1 to L2 if the prefix-attribute sub-tlv is advertised.
> ** This means if the operator does not configure advertisement of the prefix-attribute tlv, ISIS could potentially use an end-sid which does not terminate on the expected node.
>
> * Compared to sr-mpls, a prefix-sid has the R flag indicating it is redistributed.
> * We don't have that for locator end-sids.
>
> Relevant snip from " draft-ietf-lsr-isis-srv6-extensions"
>
> 7.1. SRv6 Locator TLV Format
>
> The SRv6 Locator TLV has the following format:
>
> 0 1 2 3
> 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> | Type | Length |R|R|R|R| MT ID |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
> Type: 27
>
> Length: variable.
>
> R bits: reserved for future use. They MUST be
> set to zero on transmission and MUST be ignored on receipt.
>
> MT ID: Multitopology Identifier as defined in [RFC5120].
> Note that the value 0 is legal.
>
> Followed by one or more locator entries of the form:
>
> 0 1 2 3
> 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> | Metric |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> | Flags | Algorithm |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> | Loc Size | Locator (variable)...
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> | Sub-TLV-len | Sub-TLVs (variable) . . . |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>
> Metric: 4 octets. As described in [RFC5305].
>
> Flags: 1 octet. The following flags are defined
>
> 0
> 0 1 2 3 4 5 6 7
> +-+-+-+-+-+-+-+-+
> |D| Reserved |
> +-+-+-+-+-+-+-+-+
>
> where:
> D-flag: Same as described in section 4.1. of [RFC5305].
>
>
> G/
>
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