RE: link capacity and reservable

[Dimitry Haskin <dhaskin@axiowave.com>]

Waisum, Jerry,

IMO, both yours and Francois' formulas for the aggregate reservation
constrain would achieve identical results. Note that max reservable b/w
constraint is simply applied to the sum of reservations at each CT which
already account for individual overbooking factors at each CT. However with
the formula that you are proposing we would completely shut the door for
other uses of the max link b/w TLV, for instance as a constraint on the max
LSP b/w. Since we have already a parameter that was explicitly defined as
the aggregate reservation constrain, there is no need to close door for a
different use of the max link b/w parameter at this point.

Regards,
  Dimitry  

> -----Original Message-----
> From: Lai, Wai S (Waisum), ALABS [mailto:wlai@att.com]
> Sent: Monday, May 19, 2003 4:47 PM
> To: te-wg@ops.ietf.org
> Cc: Dimitry Haskin; Francois Le Faucheur (flefauch); Ash, Gerald R
> (Jerry), ALABS
> Subject: link capacity and reservable
> 
> 
> This is in response to the discussion of maximum reservable
> bandwidth in
> http://ops.ietf.org/lists/te-wg/te-wg.2003/msg00264.html
> http://ops.ietf.org/lists/te-wg/te-wg.2003/msg00265.html
> As the issue is not restricted solely to MAM, and has impact on
> RDM and in fact all BC models, I am talking about it in a more
> general context.
> 
> Current TE extension in IGP deals with aggregate traffic.
> There is thus a simple average-overall relationship:
> max link bandwidth = max reservable bandwidth/overbooking.
> As a result, whether "max link bandwidth" is supported or
> commonly used or not is immaterial.
> 
> In DS-TE, there is per-CT bandwidth contstraint and per-CT
> overbooking.  Max reservable bandwidth should accordingly be
> treated as a vector quantity.  Reflecting this view, the
> following definition for MAM in <tewg-diff-te-reqts> is
> adequate:
>   for each value of b in the range 0 <= b <= 7:
>     Reserved (CTb) <= BCb
> (with some clarification in MAM spec regarding overbooking)
> 
> Also, the following additional condition for MAM definition as
> proposed in the second message quoted above is both unneccsary
> and incorrect:
>   SUM (Reserved (CTc)) <= Max Reservable Bandwidth
>     for all "c" in the range 0 <= c <= (MaxCT-1)
> 
> This is like when I have 15 dollars and 10 euros in my pocket,
> then my max reserve is 25 (of what unit).
> 
> The "max link bandwidth," being a normalized quantity, is more
> meaningful.  For admission control under MAM, in addition to
> the observing the bandwidth constraints as specified in the
> above deinition, something like the following may be used:
>   SUM (Reserved (CTc)/overbooking(CTc)) <= Max Link Bandwidth
>     for all "c" in the range 0 <= c <= (MaxCT-1)
> (with some tweaks to account for priorities)
> 
> Thanks, Wai Sum
>