Subject: WG last call: draft-ietf-tewg-diff-te-proto-03.txt

From: Jim Boyle <[email-masked]>
Date: Mon, 7 Apr 2003 23:56:11 -0400 (EDT)

http://www.ietf.org/internet-drafts/draft-ietf-tewg-diff-te-proto-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

---

From: Dimitry Haskin <[email-masked]>
Date: Fri, 11 Apr 2003 15:04:51 -0400

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:[email-masked]]
> Sent: Monday, April 07, 2003 11:56 PM
> To: [email-masked]
> Subject: WG last call: draft-ietf-tewg-diff-te-proto-03.txt
> 
> 
>

---

From: "Lai, Wai S (Waisum), ALABS" <[email-masked]>
Date: Mon, 21 Apr 2003 11:55:22 -0500

Francois,
   This message addresses Comment 2 in your message
http://ops.ietf.org/lists/te-wg/te-wg.2003/msg00228.html
as it relates to the DS-TE proto draft Last Call.

   Per your suggestion, I will add some clarification to my
draft.  Also, I think it would be good to resolve the issue
along with the comments of the following two messages:
http://ops.ietf.org/lists/te-wg/te-wg.2003/msg00224.html
http://ops.ietf.org/lists/te-wg/te-wg.2003/msg00128.html

Thanks, Wai Sum

-----Original Message-----
From: Jim Boyle [mailto:[email-masked]]
Sent: Monday, April 07, 2003 11:56 PM
To: [email-masked]
Subject: WG last call: draft-ietf-tewg-diff-te-proto-03.txt

thanks,

Jim Boyle

---

From: "Francois Le Faucheur (flefauch)" <[email-masked]>
Date: Fri, 25 Apr 2003 14:50:09 +0100

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.

BTW: any thoughts on the "SAM" name?

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).
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.

Thanks for your review.

Francois

>> From: Dimitry Haskin [mailto:[email-masked]] 
>> Sent: 11 April 2003 21:05
>> To: 'Jim Boyle'; [email-masked]
>> Subject: RE: WG last call: draft-ietf-tewg-diff-te-proto-03.txt
>> 
>> 
>> 
>> Section 5.1, page 10:
>>

---

From: Dimitry Haskin <[email-masked]>
Date: Fri, 25 Apr 2003 14:41:17 -0400

Francois,

See comments inline.

> From: Francois Le Faucheur (flefauch) [mailto:[email-masked]]
> Sent: Friday, April 25, 2003 9:50 AM
> To: Dimitry Haskin; [email-masked]

I have no problems with the proposed text.

> BTW: any thoughts on the "SAM" name?

No idea.

> 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
> made a little clearer on that. I will mention this to the authors (and

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? 

> below Max Reservable Bw, since Unreserved Bw will always be 

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.

> Francois

You are welcome,
  Dimitry

---

From: "Lai, Wai S (Waisum), ALABS" <[email-masked]>
Date: Fri, 25 Apr 2003 13:43:32 -0500

Francois,
  Since "Max Link Bw" is correct in the CAC formulas, where is
"Max Reservable Bw" used?
  Also, I agree with Dimitry's suggested replacement text below
for "Max Reservable Bw," which is more neutral and independent
of BC models.  I think the current text in the Proto draft is
slanted towards RDM.
  As discussed in
http://ops.ietf.org/lists/te-wg/te-wg.2003/msg00184.html
the current MAM definition in the Requirements draft allows
preemption across CTs.  Clarification as described in this
posting can be added to the MAM spec.  Thus, there is no
inconsistency in the Requirements draft.  We do not need a
new name for an old model.
Thanks, Wai Sum 

-----Original Message-----
From: Francois Le Faucheur (flefauch) [mailto:[email-masked]]
Sent: Friday, April 25, 2003 9:50 AM
To: Dimitry Haskin; [email-masked]
Subject: RE: WG last call: draft-ietf-tewg-diff-te-proto-03.txt

Dimitry,

Thanks for your review.

Francois