Subject: [Diffserv] Assured Rate PDB

From: "Nabil Seddigh" <[email-masked]>
Date: Wed, 3 Jan 2001 17:29:28 -0500 (EST)

The Assured Rate PDB can now be found on the IETF site:

http://www.ietf.org/internet-drafts/draft-seddigh-pdb-ar-00.txt

The PDB is suitable for aggregates that require rate assurance
but do not require jitter or delay guarantees. 

Comments?

Best,
Nabil
-----

In message "[Diffserv] basic doubts about PHBs", Kathleen
Nichols writes:

>
>Actually, there WAS an unsubmitted draft from Nabil Seddigh, Biswajit
>Nandy,
>and Juha Heinanen on something called an AR PDB. (Assured Rate, I
>think). They sent us a url for it after the I-D deadline and we 
>encouraged them to submit it, but said it was too late for
>the San Diego IETF.
>
>	Kathie

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---

From: demir <[email-masked]>
Date: Thu, 4 Jan 2001 19:03:26 -0800 (PST)

1) "Bandwidth" and "Assured Rate" are used as comparable parameters. I
think "bandwidth" word  should not be used in the document at all to be
more clear.
I assume the main intuition of AR PDB is:
   "This PDB ensures that traffic conforming  to a committed information
   rate (CIR) will incur low drop probability."
2)
   "The traffic aggregate will also have the opportunity
   to obtain excess bandwidth beyond the assured rate."

This sentence is kind of confusing because excess bandwidth and assured
rate are related to each other. Result is "beyond the assured
rate". "assured rate" is not a deterministic metric. It is CIR that is
deterministic. I think "excess resources" would be a better choice.

3) "The  PDB is  applicable  for  a  one-to-one,  one-to-few as well as
   one-to-any types of service."

It is not clear what this sentence means. I assume these are services can
be based on from ingress to egress?

4) "The possibility of obtaining excess bandwidth allows  development  of
   various  novel  SLA  models.  e.g.  Excess  bandwidth is charged at a
   higher rate than assured bandwidth; Excess bandwidth is cheaper  than
   assured  bandwidth;  Excess  bandwith  is charged proportionally etc.
   Development and discussion of such service and  charging  models  are
   beyond the scope of this document."

I assume it is not possible to talk about excess bandwidth which might be
varying. This paragraph is kind of confusing. I think "excess
resources" would be a better choice. Excess bandwidth should be something
like "excess information rate" that is more than CIR (instead of assured
bandwidth).

5) "Regardless  of  the  traffic mix, the CIR for the aggregate will be
    assured."

This sentence is kind of confusing. What is "traffic mix"? is it aggregate
load? I assume traffic aggregate will have a assured rate. CIR is a
parameter.

6) "better treatment of individual short microflows within  an  aggregate"

What does that mean? is it TCP with short connection times?

7) "The grouping of microflows into the traffic  aggregate  can  be  done
   either  at  the  customer site or by the provider's ingress router on
   behalf of the customer."

What do you mean by grouping?

8)  "A committed information rate (CIR) that is assured with high
     probability."

Conforming packets are assured. Not CIR.

9) "In the case of one-to-any services, the PDB can be utilized to assure
   a  rate for a traffic aggregate that originates from one ingress node
   but whose individual five-tuple flows may exit the domain at  any  of
   the egress nodes."

   I am confused here. How do you define a "traffic aggregate"? Actually,
It is not clear what you mean by "one-to-any" services.

Alper K. Demir

---

From: demir <[email-masked]>
Date: Fri, 5 Jan 2001 16:41:30 -0800 (PST)

"6.0 Assumptions
   
   The assumption is that the network operator  monitors  the  level  of
   green  packets  in  the  selected  AF  class  on  all  links  and, if
   necessary, takes traffic engineering actions to keep  the  level  low
   enough  so that the likelyhood of green packets being dropped in case
   of congestion is very low."

Can this be more generalized as: The network is well-provisioned enough so
that the likelyhhod of green packets being dropped in case of congestion
is very low. If necessary, network operator takes traffic engineering
actions. One way of achieveing this is that network operator monitors the
level of green packets in the selected AF class on all links. Provisioning
of the network is out of scope of this draft.
Just a suggestion.

Alper K. Demir

---

From: Juha Heinanen <[email-masked]>
Date: Sat, 6 Jan 2001 09:48:24 +0200 (EET)

> of the network is out of scope of this draft.

fine with me, juha

---

From: Marcus Brunner <[email-masked]>
Date: Mon, 08 Jan 2001 14:38:29 +0100

Alper,

You are right, the mechanisms to achieve the low loss probability,
should be left open.
Traffic engineering with what ever means is one example, others could be
admission control,  network planning, or other management operations.

Marcus

-- 

Dr. Marcus Brunner
C&C Research Laboratories
NEC Europe Ltd.

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