Re: [Isis-wg] Benoit Claise's No Objection on draft-ietf-isis-pcr-04: (with COMMENT)

[János Farkas <[e-mail]>]

Hi Benoit and Linda,

Thank you very much for the review!

RFC5305 and draft-ietf-isis-te-metric-extensions have been used as basis 
for draft-ietf-isis-pcr, both of them are included in the normative 
references. Section 4 lists RFC5305 and 
draft-ietf-isis-te-metric-extensions sub-IS-IS TLVs that may be used by 
IS-IS PCR including Bandwidth sub-TLVs; they are listed on page 8.

draft-ietf-isis-te-metric-extensions defines multiple Bandwidth sub-TLVs 
of exactly the same form (except for the different values of the Type 
parameter). These Bandwidth sub-TLVs have different purpose. (4.5.  
Unidirectional Residual Bandwidth Sub-TLV, 4.6. Unidirectional Available 
Bandwidth Sub-TLV, 4.7.  Unidirectional Utilized Bandwidth Sub-TLV) All 
these sub-TLVs are stored in the Traffic Engineering Database (TED).

The Bandwidth Constraint sub-TLV has a different purpose compared to the 
Bandwidth sub-TLVs of draft-ietf-isis-te-metric-extensions. Bandwidth 
Constraint sub-TLV specifies constraint for constrained routing. The 
Bandwidth Constraint sub-TLV is compared to the TED to decide whether or 
not the constraint is met. Furthermore, Bandwidth Constraint sub-TLV 
defines additional parameters (PCP, DEI), which are are needed but not 
provided by either of the isis-te-metric-extensions sub-TLVs. Thus, the 
new sub-TLV provides the new parameters and clear distinction in the 
purpose.

Consistency with isis-te-metric-extensions and RFC5305 is ensured 
because the Available Bandwidth parameter of the Bandwidth Constraint 
sub-TLV is encoded exactly the same way as the bandwidth parameter of 
the TLVs specified in isis-te-metric-extensions and RFC5305 . This is 
also necessary to be able to compare the parameter of the Bandwidth 
Constraint sub-TLV with the TED. (It is explained in  item g) of Section 
6.3 in draft-ietf-isis-pcr.)

Best regards,
Janos


On 1/7/2016 9:01 AM, Benoit Claise wrote:
> Benoit Claise has entered the following ballot position for
> draft-ietf-isis-pcr-04: No Objection
>
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> ----------------------------------------------------------------------
> COMMENT:
> ----------------------------------------------------------------------
>
> As mentioned by the Linda Dunbar in her OPS-DIR review:
> Minor issues:
>
> Why the Bandwidth Constraint sub-TLV is not same as the Bandwidth Sub-TLV
> defined by
> https://tools.ietf.org/html/draft-ietf-isis-te-metric-extensions-07#page-10?
>
> Need to make sure that the Bandwidth Sub-TLV (unidirectional available
> bandwidth, unidirectional utilized bandwidth sub-TLV, etc), of
> draft-ietf-isis-te-metric-extensions is consistent.
>
> Regards, Benoit
>
>
>
>