Khaled,
I aggree with Offer. As we made our way, over a year, in
becoming a working
group in IEEE to define a MAC we
have picked up a lot of information
on various
approaches for a RPR based system. What stood out as wide
difference are system level issues like fairness and congestion
control
contrasted with how similar each of the MAC
header definition was.
The reality was that each RPR
system dealt with different services at the
box
level.
What happened during the study group phase
was a testimony of
existence of a common shared
ring, multi-node, spatial reuse paradigm
by
describing "system" level features of each type of box that could sit
on an RPR ring. Now we are in the role of defining a MAC.
We need take the
value of this education but move
forward and go define the basic
element - the
MAC.
Although, it is inconceivable of an RPR box without features
to
address congestion on the ring it is not within
the usual realm of MAC
definitions. MAC's decide
WHEN to put ANY packet GIVEN to it by the
system on
its client interface on the INDICATED media interface and not
necessarily decide WHICH packet. MAC's can indicate
to the client indicate when
it is ready for the next
packet giving the client the flexibility in either
deffering transmission or giving the MAC a certain type of
packet.
A MAC's role in a networking system is to
predictably deliver a packet given
on its client
interface to the physical layer. Both the assurance of
the packet being delivered accurately over the physical layer and
keeping a tab
on which MAC is putting more or less
traffic is usually not a MAC layer issue.
Some
networking MACs made this their business and died a vey young death
on
their way to adoption (ATM's ABR). Hence I view
fairness on rings a system
level issue and not a MAC
issue. Further, we need an official position in the working
group of this kind of jurisdictional issue as Offer pointed
out.
I agree, that one must define a MAC by understanding common
types of congestion and
fairness schemes that exist.
However, the actual definition of a particular
congestion or fairness scheme is to narrow, rigid and will fail to
provide
flexibility and differentiation in products
that adopt RPR as a technology.
It has been very intriguing to me that while you are taking
a straw (amended
words) poll on the type of traffic
(TCP or raw) I wonder if you will find
any different
answers than the rest of this world has already found in terms
of what types of congestion mechanisms work for
these types of end-to-end
flows when they travel
across a series switches. Even if you do find a different
flow control mechanism or congestion algorithm this would not give
RPR an edge
over ethernet switches in a ring since
at the MAC layer you will only be able
to control
aggregate flows (a combination of TCP and raw). It would be
instructional
for us to review how ethernet decided
to deal with this with the option of
using pause
frames (sort of an XON/XOFF scheme) in Ethernet. What algorithm triggers a
PAUSE frame is certainly not part of the Ethernet
standard. The point I am making
is we must be
able to focus ourselves to the MAC and not get side tracked by
system level issues.
let us try to work what is relevant to MAC and not spend
time on developing a new
fairness alogirthm or a
congestion mechanisms - we will never get the standard
done in time to rally support in the industry that RPR is a promising
technology as seen
by steady progress toward
standardization by gaining confidence through the
widespread commonality
Raj Sharma
-----Original Message-----
From:
Khaled Amer [mailto:khaledamer@xxxxxxx]
Sent: Tuesday, January 30, 2001 7:01 PM
To: pazy@xxxxxxxxxxxxxxxxxx
Cc: 'Reflector
RPRSG'
Subject: Re: RPR perf: Regarding the
vote
Offer,
Thanks for the input.
You're right.
That's why I carefully worded it as a straw poll vote.
You're also right about cautioning about the need to
carefully define what
needs to be done and what is
meant by terms like fairness, ...etc.
Since we need so much more time to handle these issues, we
formed a separate
adhoc for that activity with all
the experts invited to participate and help
out with
this effort. Only getting an hour or two as part of the mainstream
discussion won't cut it. Also, seeing that we have so much
more to do, we
had to postpone starting the
simulation efforts till next meeting. In the
meantime, we hope to continue to hold productive, fruitful
discussions on
the reflector so that we can make
significant progress in March. Also, as I
indicated
in January, I'm requesting that we get about 8 hours in March to
plow through all these issues after working on them as much
as possible on
the reflector. Hopefully this will
help us make good progress in March, and
also
proceed properly to ensure that we're on the right track.
Your input is very welcome, and any other input is
appreciated. This helps
make sure that we're on the
right track.
Thanks again for the input.
Khaled Amer
Chairman, RPR
Performance Modeling adhoc Committee
President,
AmerNet Inc.
Architecture Analysis and Performance
Modeling Specialists
Address: 13711 Solitaire Way, Irvine, CA
92620
Phone:
(949)552-1114
Fax: (949)552-1116
e-mail:
khaledamer@xxxxxxx
Web:
www.performancemodeling.com
----- Original Message -----
From:
Offer Pazy <pazy@xxxxxxxxxxxxxxxxxx>
To:
'Khaled Amer' <khaledamer@xxxxxxx>; 'Donghui Xie'
<dxie@xxxxxxxxx>
Cc: 'Reflector RPRSG'
<stds-802-rprsg@xxxxxxxx>
Sent: Tuesday,
January 30, 2001 6:19 PM
Subject: RE: RPR perf:
Regarding the vote
> Hi all,
>
> I hate to be the "procedure" cup, but I have to remind everybody
that we
are
> not in a
position to take any "formal votes" yet. Also, we should not
treat
> previous SG decisions as
binding and worry about "reopening" decisions.
The
> first time we can officially vote is
in March. This is not just a
> theoretical issue
or one which concerns the perf. ad-hoc only. I suspect
> that the performance work will take a significant amount of the
time and
> resources of the entire WG and
therefore the decision of what to do and
how
> much needs to be taken carefully.
>
> I realize that a lot of preparatory
work is needed in order to bootstrap
the
> simulation work and the earlier we do it the better.
On the other hand, we
> cannot let the simulation
work shape the outcome of what the MAC will look
> like. I read a lot of references to fairness, congestion
control, and
other
>
features which 1) are far from being properly (and consensus-ly)
defined,
> and 2) have not been formally voted as
being part of the requirements.
>
> I plead for caution and patience. Trying to rush
things will only hurt us
> later on in the
process when consensus will be hard to achieve.
>
>
> Offer
Pazy
> Sr. Product Manager
> Native Networks
> 15 Gonen St.
> Petah Tikva 49170
>
Israel
> Tel: +972 3 921-0010 Ext. 229
> Fax: +972 3 921-0080
>
pazy@xxxxxxxxxxxxxxxxxx <mailto:pazy@xxxxxxxxxxxxxxxxxx>
> http://www.nativenetworks.com
>
> The Native Way = Ethernet
Simplicity + SONET Reliability
>
>
> -----Original Message-----
> From: owner-stds-802-rprsg@xxxxxxxx
[mailto:owner-stds-802-rprsg@xxxxxxxx]On
> Behalf Of Khaled Amer
>
Sent: Tuesday, January 30, 2001 22:24
> To:
Donghui Xie
> Cc: Reflector RPRSG
> Subject: Re: RPR perf: Regarding the vote
>
>
>
> All,
>
> Please put:
> RPR perf: vote
> in the e-mail subject field.
>
> and select one of the options:
> - TCP
> - raw packets
> - Abstain
>
> This will help me a lot.
>
You can add comments following that if you want.
>
> Thanks.
>
> Khaled Amer
> President, AmerNet Inc.
>
Architecture Analysis and Performance Modeling Specialists
> Address: 13711 Solitaire Way, Irvine, CA
92620
>
Phone:
(949)552-1114
Fax: (949)552-1116
>
e-mail:
khaledamer@xxxxxxx
>
Web:
www.performancemodeling.com
>
>
>
> -----
Original Message -----
> From: Donghui Xie
<dxie@xxxxxxxxx>
> To: Khaled Amer
<khaledamer@xxxxxxx>
> Cc: Reflector RPRSG
<stds-802-rprsg@xxxxxxxx>
> Sent: Tuesday,
January 30, 2001 11:02 AM
> Subject: Re: RPR
perf: My thoughts
>
>
> >
>
> Hi All,
> >
>
> TCP traffic performance over RPR is definitely the most important
part
of
> > RPR MAC
evaluation. However, I don't think TCP traffic performance over
> RPR
> > should be the
first step. What we need here is to establish a clean and
> > simplistic RPR MAC performance baseline in a timely manner.
TCP network
> > behavior can be pathological
due to many reasons ranging from
application,
> > RTT estimation factors to TCP simulation models.
By just specifying a
> Tahoe
> > or any other flavor of TCP would not bring consensus to TCP
traffic
> > generation specification any time
sooner.
> >
> >
Using raw UDP traffic will never produce a definitive performance
> > conclusion for RRP MAC, but it does allow us to
focus on RPR MAC
> > performance baseline. RPR
MAC performance evaluation should be a
> >
progressive advancing process, from simple to complex and from
partial
to
> >
complete. Any shortcut may well be counter productive and time
consuming.
> >
> > I support raw UDP traffic as step #1
simulation.
> >
>
> Best Regards,
> > Donghui Xie
> >
> >
> > At 10:22 AM 1/30/01 -0800, Khaled Amer
wrote:
> >
> >
>All,
> > >
>
> >I'd like to suggest that we avoid involving ourselves in heavy
duty
> traffic
> >
>characterization problems (whether traffic is self-similar or not,
and
> all
> >
>of that). As we know, this is an active area of research, and we
can
spin
> > >our
wheels trying to resolve this. There are so many schools of thought
> on
> > >this. I don't
believe that it will have a dramatic effect on what we're
> > >trying to accomplish here.
>
> >
> > >Now, on another related
point, in August, we had arrived to the
>
conclusion
> > >that we'll start step#1 of
the simulations using raw traffic with no
> >
>protocols involved, and make the runs with TCP and UDP (and mixes)
as
> step
> >
>#2. We voted on this and agreed among ourselves to do so. I looked
at
my
> > >records
and found that the Luminous guys didn't attend that meeting
when
> we
>
> >made that decision. Apparently they had to leave.
> > >
> > >I'm seeing that
there are a lot of discussions on the reflector going
> back
> > >to this point. Even
though I don't want to take a step back on
decisions
> > >that were already
made and voted on, so that we continue to make
>
progress, I
> > >guess we need to reopen
this one and make a decision again.
> >
>
> > >I'll open it up for an electronic
straw poll vote.
> > >
> > >Here is what we'll be voting on:
> > >
> > >As the first
step in running the simulations, we should use traffic
> streams
> > >that:
> > >1) use TCP streams as step #1 in the
simulations, and not just raw
data.
> Raw
> > >data and other
protocols (like UDP) will follow immediately afterwards
as
> > >step #2.
> > >2) use raw packets with no protocols as step #1 in the
simulations.
TCP
>
and
> > >UDP protocols (as well as mixes)
will follow immediately afterwards as
>
step
> > >#2.
>
> >
> > >Please vote by selecting one
of the following choices:
> > >
> > >- TCP
> > >-
raw packets
> > >- Abstain
> > >
> > >Please remember
that this vote is just for the first set of
simulations.
> > >Just trying to
narrow down the number of runs to a manageable subset
for
> the
>
> >first batch of simulations. We all agree that we're going to be
doing
all
> of
> > >the other steps in the presentation that I
gave as step #2.
> > >
> > >Please cast your vote by Friday (2/1). I'll post the
results that
evening
>
or
> > >over the weekend.
> > >
> > >Please
put:
> > > RPR
perf: vote
> > >in the e-mail subject
field.
> > >
>
> >In either case, we're going to decide on some simple traffic
input
> process
> >
>that we can use as a starting point too. We can get into more
elaborate
> ones
>
> >later, if we see that it would be appropriate and productive for
this
> group
> >
>to use (and if it doesn't get us all into a black hole!)
> > >
> >
>Waiting for your vote.
> > >Best
regards.
> > >
>
> >Khaled Amer
> > >Chairman, RPR
Performance Modeling adhoc Committee
> >
>President, AmerNet Inc.
> >
>Architecture Analysis and Performance Modeling Specialists
> > >Address: 13711
Solitaire Way, Irvine, CA 92620
> >
>Phone:
(949)552-1114
Fax: (949)552-1116
> >
>e-mail:
khaledamer@xxxxxxx
> >
>Web:
www.performancemodeling.com
> >
>