[e2e] QoS vs Bandwidth Overprovisioning
demir at usc.edu
Tue Apr 24 19:01:00 PDT 2001
I agree with below points. The whole claim will depend on
"expectation"; resulting with how we define QoS and how we defined the QoS
architecture. "Expectations" are limited/constrained by demanding
"taffic" and available "capacity". I think "Best Effort". "Intserv" and
"Diffserv" architectures emerged with these constraints in mind ("scale"
and "granularity"/""volume" factors were chosen accordingly in each
architecture). Currently, the spectrum of "best effort", "intserv" and
"diffserv" can be defined as a "triangle". To me, the whole spectrum is a
"circle". As a result, I don't see any reason why "QoS vs Bandwidth
Overprovisioning" is in question. Whenever, "demanding traffic" and
"available capacity" don't match with "expectations" (I think this will be
an infinite process), QoS architectures will be in
place. "Bandwidth overprovisioning" is a " capacity constraint" for a
"QoS" architecture and I suspect that it is not a solution
itself. "expectation" is a point in the "circled spectrum" constrained by
"demanding traffic" and "available capacity".
Alper K. Demir
University of Southern California, PhD student
Los Angeles, CA
On Tue, 24 Apr 2001, Alhussein Abouzeid wrote:
> Sure- bandwidth overprovisioning may work in some transitional stage, as
> long as TCP is there to limit http and short transfer goodputs to mediocre
> values, as long as the last mile technology remains so much in a lag, and as
> long as clients are limited by "agreements" with the ISP not to consume
> "too much" bandwidth!
> The 133MHz processor 4 years ago was a blasting speed.
> 1.3 Ghz processors are now available.
> Seen anybody satisfied, or saying enough ?
> Talk about overprovisioning beyond human capacity?
> Define infinity.
> On Tue, 24 Apr 2001, RJ Atkinson wrote:
> > It isn't clear to me that it is more expensive
> > to over-provision bandwidth in a backbone than to deploy
> > QoS in that backbone. Some folks here seem to be asserting
> > that it is generally cheaper to deploy QoS.
> > Many ISP folks believe that it is cheaper to over deploy
> > capacity, else there would not be so many ISPs that are
> > doing so. Most (maybe all) of the Tier-1 ISPs  indicate
> > that they over-provision their network and generally engineer
> > it such that they don't lose packets inside their own backbone
> > (though some packets get lost at the handoff between backbones,
> > in my personal experience; pardon the purely anecdotal interjection).
> > For many big providers, the recurring operations costs
> > (e.g. NOC staff, deployment staff, troubleshooting staff,
> > more generally: hiring and retaining clue) are believed to dwarf
> > the capital costs of building a network -- iff one already has
> > dark fibre facilities in place. This belief might relate to the
> > current lack of widely deployed QoS in large backbone networks.
> > As to the costs of over-provisioning, once one has access
> > to dark fibre, it is not particularly more expensive (in capital
> > costs) to light it with Gigabit Ethernet than 10baseF or 100baseFX
> > (or sundry fibre-optic extenders). Similarly it isn't really
> > that much more expensive to light up a segment with OC-48 than
> > OC-12 or OC-3. My guess is that within 12 months time, lighting
> > at OC-192/10 GigE won't be hugely more expensive than OC-48 was
> > last year. It seems more common that big providers have
> > access to dark fibre than the smaller providers, so this might
> > mean that smaller providers have more incentive to deploy QoS;
> > I'm not sure.
> > As a sidebar, I note that the cost of dark fibre facilities
> > trans-continent has dropped dramatically in North America in the
> > past few years. Similar cost drops appear to be starting in Europe
> > as well. Trans-Atlantic capacity has dropped substantially in cost;
> > trans-pacific capacity appears poised to have a similar cost
> > drop.
> > So it just isn't clear to me that the marketplace is
> > going to drive the facilities-based providers to deploy end-to-end
> > QoS anytime particularly soon. Maybe I'm totally wrong.
> > Kindly note well that this is a set of observations about
> > what appears to be happening, not a set of assertions about
> > my personal druthers if I had a magic wand.
> > Ran
> > rja at inet.org
> >  A market definition of "Tier-1 ISP" might be the set of
> > folks, including UUnet, who don't pay money to UUnet to exchange
> > traffic. A more technical definition (slightly different set
> > of providers, btw) might be based on having at least dual OC-48
> > capacity cross-continent and a presence in all of the major 10-20
> > metro areas. For the purpose of this note, the precise definition
> > isn't so important as the general concept...
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