If we don't ignore, then we
are not really mandating it.
thanks,
Peter
Thanks for the discussion,
--Bruno
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:[email protected]] *On Behalf Of *Gengxuesong
(Geng Xuesong)
*Sent:* Wednesday, May 12, 2021 9:16 AM
*To:* Les Ginsberg (ginsberg) <[email protected]>; Shraddha Hegde
<[email protected]>; Alvaro Retana
<[email protected]>; Peter Psenak (ppsenak)
<[email protected]>;
[email protected]
*Cc:* [email protected]; [email protected];
Van De Velde, Gunter (Nokia - BE/Antwerp)
<[email protected]>
*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:[email protected]]
*Sent:* Wednesday, May 12, 2021 6:29 AM
*To:* Shraddha Hegde <[email protected]
<mailto:[email protected]>>; Alvaro Retana
<[email protected] <mailto:[email protected]>>; Peter
Psenak
(ppsenak) <[email protected] <mailto:[email protected]>>;
[email protected]
<mailto:[email protected]>; Gengxuesong (Geng Xuesong)
<[email protected] <mailto:[email protected]>>
*Cc:* [email protected] <mailto:[email protected]>;
[email protected]
<mailto:[email protected]>; Van De Velde,
Gunter (Nokia - BE/Antwerp) <[email protected]
<mailto:[email protected]>>
*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 <[email protected] <mailto:[email protected]>> *On
Behalf Of *Shraddha Hegde
*Sent:* Tuesday, May 11, 2021 8:21 AM
*To:* Alvaro Retana <[email protected]
<mailto:[email protected]>>; Peter Psenak (ppsenak)
<[email protected] <mailto:[email protected]>>; [email protected]
<mailto:[email protected]>
*Cc:* [email protected] <mailto:[email protected]>;
[email protected]
<mailto:[email protected]>; Van De Velde,
Gunter (Nokia - BE/Antwerp) <[email protected]
<mailto:[email protected]>>
*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 <[email protected] <mailto:[email protected]>> *On
Behalf Of *Alvaro Retana
*Sent:* Friday, May 7, 2021 7:23 PM
*To:* Peter Psenak <[email protected]
<mailto:[email protected]>>;
[email protected] <mailto:[email protected]>
*Cc:* [email protected] <mailto:[email protected]>;
[email protected]
<mailto:[email protected]>; Van De Velde,
Gunter (Nokia - BE/Antwerp) <[email protected]
<mailto:[email protected]>>
*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 ([email protected]
<mailto:[email protected]>) 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/
>
__________________________________________________________
__________________________________________________________
_____
Ce message et ses pieces jointes peuvent contenir des informations
confidentielles ou privilegiees et ne doivent donc
pas etre diffuses, exploites ou copies sans autorisation. Si vous avez recu
ce
message par erreur, veuillez le signaler
a l'expediteur et le detruire ainsi que les pieces jointes. Les messages
electroniques etant susceptibles d'alteration,
Orange decline toute responsabilite si ce message a ete altere, deforme
ou
falsifie. Merci.
This message and its attachments may contain confidential or privileged
information that may be protected by law;
they should not be distributed, used or copied without authorisation.
If you have received this email in error, please notify the sender and
delete
this message and its attachments.
As emails may be altered, Orange is not liable for messages that have
been
modified, changed or falsified.
Thank you.
__________________________________________________________
__________________________________________________________
_____
Ce message et ses pieces jointes peuvent contenir des informations
confidentielles ou privilegiees et ne doivent donc
pas etre diffuses, exploites ou copies sans autorisation. Si vous avez recu ce
message par erreur, veuillez le signaler
a l'expediteur et le detruire ainsi que les pieces jointes. Les messages
electroniques etant susceptibles d'alteration,
Orange decline toute responsabilite si ce message a ete altere, deforme ou
falsifie. Merci.
This message and its attachments may contain confidential or privileged
information that may be protected by law;
they should not be distributed, used or copied without authorisation.
If you have received this email in error, please notify the sender and delete
this message and its attachments.
As emails may be altered, Orange is not liable for messages that have been
modified, changed or falsified.
Thank you.
