Subject: RE: [mobile-ip] New Internet Draft Notification - QoS requirement s for Mobile IP

From: "Bilgic, Murat" <[email-masked]>
Date: Mon, 11 Jun 2001 17:19:54 -0700

Hemant,

A number of questions on your draft:

1. If one uses a mobility protocol complementary to mobile IP, why would
additional QoS mechanisms in mobile IP be needed? I have difficulty in
parsing the following sentence from your draft "However, the QoS scheme MUST
have provisions to accomplish its tasks even if one or more of these
mobility protocols are not used." Does it mean that in case no
"complemantary" mobility protocol is used, ...?

2. What is so special about QoS that requires Mobile IP support? Why don't
other end-to-end procedures, for example end-to-end security, require mobile
IP support? I suspect it's because, end-to-end QoS requires the involvement
of intermediary nodes, but I'd like to confirm.

3. While I consider the desire to minimize QoS interruptions be minimized as
a noble cause, I also realize that this may be somewhat conflicting with
some of your "obvious" requirements such as scalability, conservation of
wireless bandwidth, low processing overhead, etc. Do you think some
prioritization among these requirements is necessary? Also do you think, if
the MN should be able to resolve such conflicts based on only local
knowledge or does it require the network's assistance while making that
decision? (As you may guess, I'm trying to state this as a requirement not
as some form of design parameter.)

4. How should I intrepret your requirement on heterogeneous end-to-end
packet paths? Does it mean that the MN has to be aware of the entire network
topology, e.g., where diffserv, intserv, MPLS or any other mechanism is used
and how and where it is interworked? Since I don't currently have to do that
for my non-mobile host, I wonder again why is this requirement imposed for
mobile hosts?

Thanks in advance for your answers,

Murat Bilgic   

> -----Original Message-----
> From:	Hemant Chaskar [SMTP:[email-masked]]
> Sent:	Monday, June 11, 2001 1:23 PM
> To:	[email-masked]
> Subject:	[mobile-ip] New Internet Draft Notification - QoS
> requirements for Mobile IP
> 
> Hi,
> 
> I am glad to notify that the discussions on the Mobile IP QoS requirements
> 
> mailing list have now converged. I have compiled them in the form of a 
> draft:
> 
> "Requirements of a QoS solution for Mobile IP"
> draft-chaskar-mobileip-qos-requirements-00.txt
> Edited by Hemant Chaskar
> 
> This draft now appears in the IETF I-D directory also. Please provide your
> 
> comments on it.
> 
> The idea behind this draft was to create an input document to NSIS working
> 
> group that may be formed soon. It was made clear that the draft will not
> go 
> into solution space, rather be focussed on the requirements aspects.
> 
> Thanks.
> 
> Hemant Chaskar
> Nokia
> _________________________________________________________________
> Get your FREE download of MSN Explorer at http://explorer.msn.com

---

From: "Hemant Chaskar" <[email-masked]>
Date: Tue, 12 Jun 2001 14:18:06

Hi Murat:

Here are some answers to your questions:

>From: "Bilgic, Murat" <[email-masked]>
>Reply-To: [email-masked]
>To: "[email-masked]'" <[email-masked]>
>Subject: RE: [mobile-ip] New Internet Draft Notification - QoS requirement 
>s for Mobile IP
>Date: Mon, 11 Jun 2001 17:19:54 -0700
>
>Hemant,
>

[HC] Yes, that is what it implies. I will reword the sentence to avoid any 
confusion.

>of intermediary nodes, but I'd like to confirm.

[HC] Yes, that is right.

>prioritization among these requirements is necessary?

[HC] I think of it as "trade off" rather than "conflict". It is not possible 
to prioratize the above requirements in a strict order, as they are 
difficult to quantify as well as all of them are perceived to be equally 
important. A solution designer must analyse his solution to justify that it 
gives "acceptable" performance in terms of these requirements. Afterall, 
trade off balancing is what engineering is about :-)

>Also do you think, if

[HC] So much of a detail tends to drive us into solution space and reduces 
the flexibility of solution design.

>for my non-mobile host, I wonder again why is this requirement imposed for

[HC] There is no QoS in Internet today, and that's why you do not have to do 
it for your non-mobile host.

Further, if you have a static host, it is possible to configure in it the 
QoS functions that the access network expects the host to perform and those 
functions are not going to change during the ongoing session. For example, 
the service provider can tell you that it uses DiffServ in access and can 
give you a configuration file that tells what port numbers to use for say EF 
traffic so that the network can classify that traffic. In the mobile case, 
the MN may move across differnt access networks.

Also, believe me that some knowledge about the end-to-end packet path is 
required for end-to-end QoS. The host may not have this knowledge but the 
network needs to have it. It could be by virtue of SLAs between DiffServ 
domains, or such knowledge can be acquired by RSVP signalling {RFC 2998) 
over a mix of IntServ and DiffServ networks.

>Thanks in advance for your answers,

[HC] I hope this clarifies some of your concerns. Thanks for your comments.

[Hemant]

---

From: "Bilgic, Murat" <[email-masked]>
Date: Tue, 12 Jun 2001 17:24:50 -0700

Hemant,

Some more follow-up on the draft and your answers inline.

> Sent:	Tuesday, June 12, 2001 7:18 AM
> Subject:	RE: [mobile-ip] New Internet Draft Notification - QoS
> requirement s for Mobile IP
> 
> Hi Murat:
> 
	[MB]  Thanks.

> >3. While I consider the desire to minimize QoS interruptions be minimized
> 
> >as
	[MB]  I agree "trade off" is a better term.

> the flexibility of solution design.
	[MB]  I disagree on this one. But probably I should clarify my
reasoning. I see the two ends of the spectrum of solutions  as follows:
	1. MN does not need any authorization prior to a mobility event for
QoS. Therefore, the network is (over-)provisioned to accommodate such
events. Obviously this does not mean that after the mobility event, the
network can't force a degradation in the provided QoS, but the application
demanding QoS has a much longer time to adopt itself. The benefit I see for
this end of the spectrum is potentially faster and simpler mobility. BTW,
this was what I was referring as "local knowledge".
	2. MN needs authorization, i.e., negotiation with the network prior
to a mobility event for QoS. Therefore, the network is provisioned just the
"right amount". However, the mobility mechanism is most likely more complex
and slower. In addition, the application has to react much faster to
degradation in the provided QoS. Again, this was what I was referring to as
"network assistance".

	In my opinion, there is a very big difference between these two
approaches. If you are saying the requirement is so broad such that any
solution within this spectrum would be acceptable, then I'd have difficulty
accepting the value of requirements development phase.

> over a mix of IntServ and DiffServ networks.
	[MB]  I don't dispute that end-to-end QoS requires some form of
capability to signal what you are looking for from the MN's side or what you
should use from the network side. However, as articulated quite convincingly
in RFC 2990, it's quite hard to imagine one framework, i.e., a holy grail to
solve this problem. If (at least as of today it's true) there is no unifying
QoS framework for Internet, then I'd say the argument for one for mobile
hosts is pretty weak. Instead, wouldn't it be better to put together a more
limited requirement stating that a network's QoS capabilities are used in
determining the mobility decision within the MN. In this case, there is no
reason for a "one-size fits all" QoS solution and MNs would still make
informed decisions. In addition end-to-end QoS mechanism(s) can be kept
entirely separate from mobile IP. What do you think?
> [HC] I hope this clarifies some of your concerns. Thanks for your
	[MB]  Thank you,

	Murat Bilgic