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

["Les Ginsberg (ginsberg)" <[e-mail]>]

Ron -

With respect, it is hard to read your email without feeling that it is disingenuous.

But, let's cover the relevant points nonetheless.

Point #1:

https://datatracker.ietf.org/doc/html/draft-ietf-lsr-flex-algo-17#section-12 states:

" 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]..."

As the new generic-metric is intended for use by flex-algo it needs to conform to this normative statement.

Point #2:

RFC 8919 and 8920 were written to address ambiguities associated with the use of multiple applications.
The Introduction sections of both documents discuss this in some detail.

The clear intent is to make use of ASLA going forward - not to restrict ASLA only to the set of link attributes defined at the time of the writing of the RFCs. Failure to do so would reintroduce the same set of issues that RFC 8919/8920 were written to address.
Your attempt to infer that because Generic-Metric was not defined at the time that RFC 8919/8920 were written that the RFCs don’t apply to it makes no sense.
ASLA is in fact a revision to the link attribute architecture and is meant to be used going forward.

The more appropriate question to ask is why we need to define a legacy style sub-TLV for new link attributes? Ketan has made this point in his post on this thread and I have sympathy with his position.

We do understand that legacy applications such as RSVP-TE may continue to be deployed in networks for some time to come. It is not reasonable to expect that legacy application implementations will be updated to use ASLA, which is why I do not object to defining a legacy style encoding for Generic Metric if folks believe that legacy applications may be enhanced to support new link attributes. 

I strongly disagree with your interpretation that ASLA is limited only to the code points defined in RFC 8919/8920.

   Les


> -----Original Message-----
> From: Ron Bonica <rbonica=[e-mail]>
> Sent: Thursday, July 22, 2021 10:28 AM
> To: Acee Lindem (acee) <[e-mail]>; Les Ginsberg (ginsberg)
> <[e-mail]>; Shraddha Hegde <[e-mail]>;
> [e-mail]; Peter Psenak (ppsenak) <[e-mail]>;
> [e-mail]
> Cc: [e-mail]
> Subject: RE: [Lsr] I-D Action: draft-ietf-lsr-flex-algo-bw-con-01.txt
> 
> 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 <[e-mail]> On Behalf Of Acee Lindem (acee)
> Sent: Tuesday, July 20, 2021 1:21 PM
> To: Les Ginsberg (ginsberg) <ginsberg=[e-mail]>;
> Shraddha Hegde <[e-mail]>; [e-mail];
> ppsenak=[e-mail]; [e-mail]
> Cc: [e-mail]
> 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
> 
>