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RE: WG last call: draft-ietf-tewg-diff-te-proto-03.txt
Francois,
See comments inline.
> -----Original Message-----
> From: Francois Le Faucheur (flefauch) [mailto:flefauch@cisco.com]
> Sent: Friday, April 25, 2003 9:50 AM
> To: Dimitry Haskin; te-wg@ops.ietf.org
> Subject: RE: WG last call: draft-ietf-tewg-diff-te-proto-03.txt
>
>
> Dimitry,
>
> Please check the draft text I proposed in message titled "Reflecting
> new-MAM/SAM definition in diff-te drafts" (assuming the enhancement to
> MAM definition). This should address your comments on section 5.1.
I have no problems with the proposed text.
>
> BTW: any thoughts on the "SAM" name?
No idea.
>
> Regarding your other comment, I actually think that "Max Link Bw" is
> correct in the CAC formulas.
> draft-ietf-isis-traffic-xx says:
> "This sub-TLV contains the maximum bandwidth that can be used on this
> link in this direction (from the system originating the LSP to its
> neighbors). This is useful for traffic engineering."
> I believe the intent is that one given TE-tunnel can not
> exceed the max link Bw. I believe this check is commonly implemented by
multiple
> implementations. Perhaps the text of draft-ietf-isis-traffic could be
> made a little clearer on that. I will mention this to the authors (and
> same for OSPF draft).
I have to disagree. The quoted text refer to the bandwidth that can be
*used*. The disputed text in the proto draft talks about the admission
rules, i.e. bandwidth that can be admitted. There is a clear difference
between how much Bw can be used and how mach can be admitted. Otherwise,
what would be intended difference between "Max Link Bw" and "Maximum
Reservable Bw"? Furthermore, the same draft (draft-ietf-isis-traffic)
defines the max reservable link Bw as "maximum amount of bandwidth that can
be reserved in this direction on this link" which is clearly applicable to
the traffic admission rules.
BTW, the OSPF TE draft (draft-katz-yeung-ospf-traffic-09.txt) make it
somewhat clearer by adding a sentence to the definition of the max link Bw:
"The Maximum Bandwidth sub-TLV specifies the maximum bandwidth that
can be used on this link in this direction (from the system
originating the LSA to its neighbor), in IEEE floating point format.
This is the true link capacity."
By any chance, are you confusing the "Max Link Bw" for the "Max LSP
Bandwidth" that is defined in draft-ietf-isis-gmpls-extensions-16?
> Also, it wouldn't make much sense to me to check separately that B is
> below Max Reservable Bw, since Unreserved Bw will always be
> smaller than
> Max Reservable bw.
If you're doing a path computation then checking only against the advertised
Unreserved Bw should be sufficient since the max reservable limit should
have already been taken in consideration when the advertised Unreserved Bw
was computed. However the disputed text talks about traffic admission not
path computation rules.
>
> Thanks for your review.
>
> Francois
You are welcome,
Dimitry
>
> >> -----Original Message-----
> >> From: Dimitry Haskin [mailto:dhaskin@axiowave.com]
> >> Sent: 11 April 2003 21:05
> >> To: 'Jim Boyle'; te-wg@ops.ietf.org
> >> Subject: RE: WG last call: draft-ietf-tewg-diff-te-proto-03.txt
> >>
> >>
> >>
> >> Section 5.1, page 10:
> >>
> >> "With DS-TE, the existing "Maximum Reservable Bw" sub-TLV
> >> is retained
> >> with a generalized semantic so that it MUST now be
> interpreted as
> >> Bandwidth Constraint 0 (BC0)."
> >>
> >> also Section 5.1, page 10:
> >>
> >> "A DS-TE LSR which does advertise Bandwidth Constraints,
> MAY also
> >> include the existing "Maximum Reservable Bw" sub-TLV.
> This may be
> >> useful in migration situations where some LSRs in the
> >> network are not
> >> DS-TE capable (see Appendix C) and thus do not
> understand the new
> >> "Bandwidth Constraints" sub-TLV. In that case, the DS-TE
> >> LSR MUST set
> >> the value of the "Maximum Reservable Bw" sub-TLV to the
> >> same value as
> >> the one for BC0 encoded in the "Bandwidth Constraints" sub-TLV.
> >>
> >> A DS-TE LSR receiving both the old "Maximum Reservable
> Bw" sub-TLV
> >> and the new "Bandwidth Constraints" sub-TLV for a given link MAY
> >> ignore the "Maximum Reservable Bw" sub-TLV."
> >>
> >> The above statements are implying that the "Maximum
> >> Reservable Bw" sub-TLV
> >> is redundant in the presence of Bandwidth Constraints.
> >> Furthermore, they
> >> indicate that BC0 has semantics of the maximum reservable
> >> bandwidth. This
> >> could be true for the RD model. However it is clearly not
> >> true for other
> >> models. Therefore these statements should be removed from
> >> the specification
> >> or, even better, replaced with something along the following lines:
> >>
> >> The "Maximum Reservable Bw" sub-TLV represents the
> >> aggregate bandwidth
> >> constraint of the link and as such complements the
> >> advertised Bandwidth
> >> Constraints.
> >>
> >>
> >> Section 10.2, page 20:
> >>
> >> "A DS-TE LSR MUST support the following admission control rule:
> >>
> >> Regardless of how the admission control algorithm actually
> >> computes
> >> the unreserved bandwidth for TE-Class[i] for one of its
> >> local link,
> >> an LSP of bandwidth B, of set-up preemption priority p and
> >> of Class-
> >> Type CTc is admissible on that link iff:
> >>
> >> B <= unreserved bandwidth for TE-Class[i], AND
> >> B <= Max Link Bandwidth
> >>
> >> Where
> >>
> >> - TE-Class [i] maps to < CTc , p > in the LSR's
> >> configured TE-
> >> Class mapping
> >> - Max Link Bandwidth is the maximum link bandwidth
> >> configured
> >> on the link and advertised in IGP."
> >>
> >>
> >> "Max Link Bandwidth" should be replaced with "Maximum
> >> Reservable Bandwidth".
> >>
> >>
> >> Section 10.3.4, page 22
> >>
> >> "Regardless of how the admission control algorithm
> >> actually computes
> >> the unreserved bandwidth for TE-Class[i] for one of its
> >> local link,
> >> an LSP of bandwidth B, of set-up preemption priority p and
> >> of Class-
> >> Type CTc is admissible on that link iff:
> >>
> >> (i) B <= unreserved bandwidth for TE-Class[i], AND
> >> (ii) B <= Max Link Bandwidth
> >>
> >> Where
> >>
> >> - TE-Class [i] maps to < CTc , p > in the LSR's
> >> configured TE-
> >> Class mapping
> >> - Max Link Bandwidth is the maximum link bandwidth
> >> configured
> >> on the link and advertised in IGP."
> >>
> >> "Max Link Bandwidth" should be replaced with "Maximum
> >> Reservable Bandwidth".
> >>
> >>
> >> Dimitry
> >>
> >>
> >>
> >> > -----Original Message-----
> >> > From: Jim Boyle [mailto:jboyle@pdnets.com]
> >> > Sent: Monday, April 07, 2003 11:56 PM
> >> > To: te-wg@ops.ietf.org
> >> > Subject: WG last call: draft-ietf-tewg-diff-te-proto-03.txt
> >> >
> >> >
> >> >
> >> > http://www.ietf.org/internet-drafts/draft-ietf-tewg-diff-te-pr
> >> > oto-03.txt
> >> >
> >> > This is WG last call for this draft to be advanced
> standards track.
> >> > Since notice was sent to other WGs for review, we will
> >> take 3 weeks.
> >> >
> >> > Last call for this draft closes 4/28.
> >> >
> >> > thanks,
> >> >
> >> > Jim Boyle
> >> >
> >> >
> >> >
> >>
> >>
>