Re: [Lsr] draft-ietf-lsr-flex-algo-17 (was: I-D Action: draft-ietf-lsr-flex-algo-bw-con-01.txt)

Robert Raszuk <robert@raszuk.net> Tue, 27 July 2021 19:05 UTC

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From: Robert Raszuk <robert@raszuk.net>
Date: Tue, 27 Jul 2021 21:04:57 +0200
Message-ID: <CAOj+MMEDGKXa4WFDExzD=f=CUc0QGp_zM222_UU_+oYax5HAAQ@mail.gmail.com>
To: Ron Bonica <rbonica=40juniper.net@dmarc.ietf.org>
Cc: Peter Psenak <ppsenak@cisco.com>, "Acee Lindem (acee)" <acee=40cisco.com@dmarc.ietf.org>, "Les Ginsberg (ginsberg)" <ginsberg@cisco.com>, Shraddha Hegde <shraddha@juniper.net>, "gregory.mirsky@ztetx.com" <gregory.mirsky@ztetx.com>, "lsr@ietf.org" <lsr@ietf.org>, "draft-ietf-lsr-flex-algo-bw-con.authors@ietf.org" <draft-ietf-lsr-flex-algo-bw-con.authors@ietf.org>
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Subject: Re: [Lsr] draft-ietf-lsr-flex-algo-17 (was: I-D Action: draft-ietf-lsr-flex-algo-bw-con-01.txt)
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Hi Ron,

I think you are not taking into consideration the full picture here and
instead you are only focusing only on signaling.

So let's take your example of "link's total physical bandwidth" Yes physics
wise it is generic, by nature.

And that claim is true too: "It will always be the same for all
applications."

But how do you know which applications should use it in the computation of
their topology and which do not ?

Are you saying it would be obligatory/mandatory to all applications because
you defined it to be generic ? What if I do not want to use it for
flex-algo topo 25 ?

Remember signalling by itself is useless till it allows network wide
**consistent** use in topology computation. And if your answer would be:
"Oh it would be configuration dependent node by node" then I am afraid this
would melt lots of networks pretty badly.

Cheers,
Robert
.









On Tue, Jul 27, 2021 at 7:32 PM Ron Bonica <rbonica=
40juniper.net@dmarc.ietf.org> wrote:

> Peter,
>
> I agree that we will need to update the flexago draft. But before we do
> that, can you explain why we need to maintain mandatory use of ASLA?
>
> AFAIKS, by their nature, some attributes are generic while others are
> application specific. For example, a link's total physical bandwidth is
> generic, by nature. It will always be the same for all applications. By
> contrast, the amount of bandwidth available to a specific application is
> application specific, by nature. It can be different for each application.
>
>                                                           Ron
>
>
>
>
> Juniper Business Use Only
>
> -----Original Message-----
> From: Peter Psenak <ppsenak@cisco.com>
> Sent: Monday, July 26, 2021 2:45 PM
> To: Ron Bonica <rbonica@juniper.net>et>; Acee Lindem (acee) <acee=
> 40cisco.com@dmarc.ietf.org>gt;; Les Ginsberg (ginsberg) <ginsberg@cisco.com>om>;
> Shraddha Hegde <shraddha@juniper.net>et>; gregory.mirsky@ztetx.com;
> lsr@ietf.org
> Cc: draft-ietf-lsr-flex-algo-bw-con.authors@ietf.org
> Subject: Re: draft-ietf-lsr-flex-algo-17 (was: [Lsr] I-D Action:
> draft-ietf-lsr-flex-algo-bw-con-01.txt)
>
> [External Email. Be cautious of content]
>
>
> Hi Ron,
>
> On 26/07/2021 20:30, Ron Bonica wrote:
> > Peter,
> >
> > I think that we are using the term "link attribute" differently. IMO, a
> link attribute is any attribute of a link, regardless of whether it is
> advertised in the fixed portion of a link advertisement or in a TLV.
> >
> > Are you assuming otherwise? If so, why?
>
> when we are talking about the advertisement of the link attributes, we are
> talking about something that is advertised separately and optionally, not
> something that is part of the fixed portion of the link advertisement.
>
> If that is not clear, I can make that statement in the flex-algo draft,
> but that would not remove the mandatory usage of the ASLA for the
> (optional) attributes.
>
>
> thanks,
> Peter
>
> >
> >                                                             Ron
> >
> >
> >
> > Juniper Business Use Only
> >
> > -----Original Message-----
> > From: Peter Psenak <ppsenak@cisco.com>
> > Sent: Monday, July 26, 2021 1:31 PM
> > To: Ron Bonica <rbonica@juniper.net>et>; Acee Lindem (acee)
> > <acee=40cisco.com@dmarc.ietf.org>rg>; Les Ginsberg (ginsberg)
> > <ginsberg@cisco.com>om>; Shraddha Hegde <shraddha@juniper.net>et>;
> > gregory.mirsky@ztetx.com; lsr@ietf.org
> > Cc: draft-ietf-lsr-flex-algo-bw-con.authors@ietf.org
> > Subject: Re: draft-ietf-lsr-flex-algo-17 (was: [Lsr] I-D Action:
> > draft-ietf-lsr-flex-algo-bw-con-01.txt)
> >
> > [External Email. Be cautious of content]
> >
> >
> > Hi Ron,
> >
> > On 26/07/2021 18:36, Ron Bonica wrote:
> >> Acee,
> >>
> >> We may also need to clean up an inconsistency in
> draft-ietf-lsr-flex-algo-17. Section 12 of that document says:
> >>
> >> "   Link attribute advertisements that are to be used during Flex-
> >>      Algorithm calculation MUST use the Application-Specific Link
> >>      Attribute (ASLA) advertisements defined in [RFC8919] or [RFC8920],
> >>      unless, in the case of IS-IS, the L-Flag is set in the ASLA
> >>      advertisement.  If the L-Flag is set, as defined in [RFC8919]
> >>      Section 4.2 subject to the constraints discussed in Section 6 of
> the
> >>      [[RFC8919], then legacy advertisements are to be used instead. "
> >>
> >> However, Flex-Algorithm calculations include the IGP metric.
> >
> >
> > IGP metric is not advertised as a link attribute, it is part of the
> fixed portion of the link advertisement. So the above text is not affecting
> the usage if the IGP metric.
> >
> > thanks,
> > Peter
> >
> >
> >>
> >>
> >> Ron
> >>
> >>
> >>
> >> Juniper Business Use Only
> >>
> >> -----Original Message-----
> >> From: Acee Lindem (acee) <acee=40cisco.com@dmarc.ietf.org>
> >> Sent: Friday, July 23, 2021 10:13 AM
> >> To: Ron Bonica <rbonica@juniper.net>et>; Les Ginsberg (ginsberg)
> >> <ginsberg@cisco.com>om>; Shraddha Hegde <shraddha@juniper.net>et>;
> >> gregory.mirsky@ztetx.com; Peter Psenak (ppsenak) <ppsenak@cisco.com>om>;
> >> lsr@ietf.org
> >> Cc: draft-ietf-lsr-flex-algo-bw-con.authors@ietf.org
> >> Subject: Re: [Lsr] I-D Action: draft-ietf-lsr-flex-algo-bw-con-01.txt
> >>
> >> [External Email. Be cautious of content]
> >>
> >>
> >> Hi Ron,
> >>
> >> So perhaps, generic metric is not a legacy advertisement as strictly
> defined. However, we don't want to go down the path of treating new
> attributes in the same manner as legacy attributes. It seems the discussion
> is progressing and hopefully we will have a resolution.
> >>
> >> Thanks,
> >> Acee
> >>
> >> On 7/22/21, 1:28 PM, "Ron Bonica" <rbonica=40juniper.net@dmarc.ietf.org>
> wrote:
> >>
> >>       Acee,
> >>
> >>       I don't think that draft-ietf-lsr-flex-algo-bw-con violates RFC
> 8919.
> >>
> >>       Section 6.1 of RFC 8919 says:
> >>
> >>       " New applications that future documents define to make use of the
> >>          advertisements defined in this document MUST NOT make use of
> legacy
> >>          advertisements.  This simplifies deployment of new
> applications by
> >>          eliminating the need to support multiple ways to advertise
> attributes
> >>          for the new applications."
> >>
> >>       Section 3 of RFC 8919 defines legacy advertisements. The
> definition of legacy
> >>       advertisements does not include new attributes such as
> >>       generic metric. Therefore draft-ietf-lsr-flex-algo-bw-con does not
> >>       violate RFC 8919
> >>
> >>       Relevant text from Section 3 of RFC 8919 is included below for
> convenience.
> >>
> >>
> >> Ron
> >>
> >>
> >>       RFC 8919, Section 3
> >>       ---------------------------
> >>       3.  Legacy Advertisements
> >>
> >>
> >>       Existing advertisements used in support of RSVP-TE include
> sub-TLVs
> >>          for TLVs 22, 23, 25, 141, 222, and 223 and TLVs for Shared
> Risk Link
> >>          Group (SRLG) advertisement.
> >>
> >>          Sub-TLV values are defined in the "Sub-TLVs for TLVs 22, 23,
> 25, 141,
> >>          222, and 223" registry.
> >>
> >>          TLVs are defined in the "TLV Codepoints Registry".
> >>
> >>       3.1.  Legacy Sub-TLVs
> >>
> >>          +======+====================================+
> >>          | Type | Description                        |
> >>          +======+====================================+
> >>          | 3    | Administrative group (color)       |
> >>          +------+------------------------------------+
> >>          | 9    | Maximum link bandwidth             |
> >>          +------+------------------------------------+
> >>          | 10   | Maximum reservable link bandwidth  |
> >>          +------+------------------------------------+
> >>          | 11   | Unreserved bandwidth               |
> >>          +------+------------------------------------+
> >>          | 14   | Extended Administrative Group      |
> >>          +------+------------------------------------+
> >>          | 18   | TE Default Metric                  |
> >>          +------+------------------------------------+
> >>          | 33   | Unidirectional Link Delay          |
> >>          +------+------------------------------------+
> >>          | 34   | Min/Max Unidirectional Link Delay  |
> >>          +------+------------------------------------+
> >>          | 35   | Unidirectional Delay Variation     |
> >>          +------+------------------------------------+
> >>          | 36   | Unidirectional Link Loss           |
> >>          +------+------------------------------------+
> >>          | 37   | Unidirectional Residual Bandwidth  |
> >>          +------+------------------------------------+
> >>          | 38   | Unidirectional Available Bandwidth |
> >>          +------+------------------------------------+
> >>          | 39   | Unidirectional Utilized Bandwidth  |
> >>          +------+------------------------------------+
> >>
> >>              Table 1: Sub-TLVs for TLVs 22, 23, 25,
> >>                        141, 222, and 223
> >>
> >
> >>
> >>
> >>       Juniper Business Use Only
> >>
> >>       -----Original Message-----
> >>       From: Lsr <lsr-bounces@ietf.org> On Behalf Of Acee Lindem (acee)
> >>       Sent: Tuesday, July 20, 2021 1:21 PM
> >>       To: Les Ginsberg (ginsberg) <ginsberg=40cisco.com@dmarc.ietf.org>rg>;
> Shraddha Hegde <shraddha@juniper.net>et>; gregory.mirsky@ztetx.com; ppsenak=
> 40cisco.com@dmarc.ietf.org; lsr@ietf.org
> >>       Cc: draft-ietf-lsr-flex-algo-bw-con.authors@ietf.org
> >>       Subject: Re: [Lsr] I-D Action:
> >> draft-ietf-lsr-flex-algo-bw-con-01.txt
> >>
> >>       [External Email. Be cautious of content]
> >>
> >>
> >>       Speaking as WG member:
> >>
> >>       I agree with Les. The Generic Metric MUST be advertised as an
> ASLA for usage in Flex Algorithm. Additionally, it may be advertised as a
> sub-TLV in IS-IS link TLVs. However, the latter encoding really shouldn't
> be used for new applications (at least that is my reading of RFC 8919).
> >>
> >>       For OSPF, I'd certainly hope one wouldn't originate additional
> LSAs when an ASLA can support the legacy applications with the ASLA mask.
> >>
> >>       Thanks,
> >>       Acee
> >>
> >>
> >>
> >>
> >
> >
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