Harry,
I am not suggesting a lossy ring. I requested
one, but most of you convinced
me that will never happen in RPR. So, I am
moving on with an assumption of
a loss less RPR ring and I request you do
too.
However, if I were to uphold the argument
for a loss less ring while absolutely
guaranteeing no priority inversion
than
a certain size of LPTB buffer must
designed in. Obviously the size of this
LPTB depends on the levels of HP traffic and
the RTT. Everything has a
consequence - there is no freee lunch
!
So, the corollary, that if the
LPTB size is fixed on the ring than for a given
ring circumference only a certain
level of HP traffic, with absolute guarantees
on jitter, can be provided. This implies that
carriers would have to predict
the levels of HP traffic in the network before
they procure their equipment.
The one way to resolve this problem is to be
able to "add" more LPTB
to the RPR MAC to sustain higher levels of HP
traffic on the ring. Unfortunately,
at 10 gbps speeds off-chip TB schemes will have
significant penalties.
Anyway, you missed my statement I made in the
original email.
I said that if one were to prevent packet loss
and avoid priority inversion
than one must AVOID situations that creates a
scenario to pick one
over the other. Somehow, that seems like a
simple logic to me. So,
my argument was not for supporting a lossy ring
but what you need to
in order to have a loss less ring and avoid
priority inversion.
In fact, I wonder why you don't think similar
since your requirement is to
have a loss less ring, no priority inversion
and a single 2 MTU TB. I would think
the a single TB with ability to buffer 2
packets cries out for some method
to AVOID a situation that will force priority
inversion to honor a loss less ring
requirement. I must be missing something
!
The real issue is that I am not fixated on
preserving any implementation at
the cost of having an absurd standard. On the
other hand, I am tolerant to the
big guns who want to do this I think we need to
ensure that the RPR WG
do diligence.
raj
Raj:
There are really two issues
one is vendor box issues when interworking:
1) utilization versus implementation to achieve the desired
packet delivery behavior.
The 1 TB and 2 TB design fall with in this category
Once reserved BW is allocated globally
or at link level, you think your box provide
better ring BW utilization. All the power to
you.
2) Lossy ring
This is an 802.17 issue.
Lossless
behavior is a must. You are arguing for lossy.
Regards,
Harry
-----Original Message-----
From: Leon Bruckman [mailto:leonb@xxxxxxxxxxxxx]
Sent: Tuesday, March 26, 2002 1:59 AM
To: 'Raj Sharma'
Cc:
stds-802-17@xxxxxxxx
Subject: RE: [RPRWG] RAH:
Re: Minutes of Rate Ad Hoc meeting
For the 2 transit buffer scheme there is another
way:
Have a LPTB that is deep enough. The LPTB
depth to avoid both: "on transit"
LP traffic
discard and reduced HP priority, can be calculated using the
formula in:
http://grouper.ieee.org/groups/802/17/documents/presentations/jan2002/vk_dwd
el_02.pdf
This formula can be
modified for the case of links with different reserved
rates also.
Leon
-----Original Message-----
From: Raj Sharma [mailto:raj@xxxxxxxxxxxx]
Sent: Tuesday, March 26, 2002 3:43 AM
To: 'Sanjay K. Agrawal'; Li Mo; stds-802-17@xxxxxxxx;
Nader Vijeh
Subject: RE: [RPRWG] RAH: Re:
Minutes of Rate Ad Hoc meeting
The only way to guarantee HP traffic and have no
packet loss
is to be able to AVOID situations
that will reduce the priority
of HP traffic to
satisfy a loss less ring.
There are two ways to avoid:
1. Provision the low priority to ramp-up very slowly -
this
will result in low link
utilization.
2. Constantly, provide each node
the ability to determine
what conditions would
lead to congestion.
raj
> -----Original Message-----
> From: Sanjay K. Agrawal [mailto:sagrawal@xxxxxxxxxxxxxxxxxx]
> Sent: Monday, March 25, 2002 5:03 PM
> To: Li Mo; stds-802-17@xxxxxxxx; Nader
Vijeh
> Subject: Re: [RPRWG] RAH: Re:
Minutes of Rate Ad Hoc meeting
>
>
>
> For me 2 is very important otherwise I
have very limited
> spatial reuse .
On
> the other hand, allowing the packet
loss on the ring, will
> limit the
scope
> of this technology to TCP/IP
networks. I think somehow we have to
>
accommodate both.
>
> -Sanjay K. Agrawal
>
>
> -----
Original Message -----
> From: "Li Mo"
<limo01@xxxxxxxxx>
> To:
<stds-802-17@xxxxxxxx>; "Nader Vijeh"
<nader@xxxxxxxxxxxxxx>
> Sent:
Friday, March 22, 2002 11:04 AM
> Subject:
RE: [RPRWG] RAH: Re: Minutes of Rate Ad Hoc meeting
>
>
>
>
> I agree with
the comments made by previous authers. I used to
> think one of
> the key
characteristics of RPR is "no packet loss" once it is
> in transport.
> But, with the
different reservation rate possible on
>
different spans (unless
> a very
sophasticated fairness algorithm has been used which
> is unknow at
> this time, this
characteristics may be unattendable. Hence
> we have a choice
> to be
made:
>
> 1.
allow the packet loss on the ring
> 2.
allow different reserved rate on different span
>
> For those, I would like to
see the first one unless somebody
>
developed a
> fairness algorithm which
achieves both.
>
> Li...
>
> -----Original Message-----
>
From: owner-stds-802-17@xxxxxxxxxxxxxxxxxx
> [mailto:owner-stds-802-17@xxxxxxxxxxxxxxxxxx]On
Behalf Of Nader Vijeh
> Sent: Friday, March
22, 2002 12:12 PM
> To:
stds-802-17@xxxxxxxx
> Subject: RE: [RPRWG]
RAH: Re: Minutes of Rate Ad Hoc meeting
>
>
>
> We have customers that find loosing
packets in the transport
> side of
the
> network unacceptable. One of the
reasons we hear is the "multi-tier"
>
environment, where the transport and the service side may be
> "logically"
>
separate and belong to different business entities. Another item
to
> consider is that RPR is competing with
SONET for the data transport
>
infrastructure and SONET does not loose packets in transit.
>
> Nader
>
> -----Original
Message-----
> From: Mike Takefman [mailto:tak@xxxxxxxxx]
> Sent: Friday, March 22, 2002 7:44 AM
> To: Italo.Busi@xxxxxxxxxx
> Cc:
jalemon@xxxxxxxxx; pazy@xxxxxxxxxxxx; stds-802-17@xxxxxxxx
> Subject: Re: [RPRWG] RAH: Re: Minutes of Rate Ad
Hoc meeting
>
>
>
> I beg to
differ. We had presentations by Sprint at the working
> group that it is really important where packets get
lost.
>
> Losing
packet on the media is not acceptable to them.
>
> As I said previously, routers
or switches tend to have
> buffers that are
orders of magnitude larger than any
>
buffer we are considering for the MAC. Therefore,
> loss probability is low at that level and they can
engineer
> their network, (just like they
would engineer the media)
> to get the loss
statistics where they want them.
>
> cheers,
>
> mike
>
> Italo.Busi@xxxxxxxxxx wrote:
> >
> > See my
comment in line
> >
> > Italo
> >
> > > -----Original Message-----
> > > From: pazy@xxxxxxxxxxxx [mailto:pazy@xxxxxxxxxxxx]
> > > Sent: Tuesday, March 19, 2002 3:55
PM
> > > To: jalemon@xxxxxxxxx
> > > Cc: pazy@xxxxxxxxxxxx;
stds-802-17@xxxxxxxx
> > > Subject:
RE: [RPRWG] RAH: Re: Minutes of Rate Ad Hoc meeting
> > >
> > >
> >
> >
...
> >
>
> >
> > > Furthermore, if a
user traffic is rejected at the ingress
>
point, the
> > > user gets an
immediate feedback. Assuming such a feedback is
> > > useful, how
> >
> would a network do it if a given packet was dropped not
> at the ingress
> > > but rather somewhere on the ring, say on the 5th
node in a
> > > 10-node path.
> > >
>
>
> > As far as I know, metro netwoks
are tipically made by many
> >
interconnected rings (SBC made a good presentation in
> September about
> > this
assumption).
> > This implies that you
are loosing packets in the metro
> network
so the
> > issue is not completely
solved.
> > From the customer point of
view there is no difference
> between
loosing
> > packets on the ring or in
the routers/bridges interconnecting rings.
> > The big difference is made by the amount of packets
that
> the customer
> > sees as lost at end-to-end perspective ...
> >
> > >
Again, I hope that I've managed to clarify my views, but
> I am not sure
> > > if we "violently agree" or still have some
differences.
> > >
> > > Offer Pazy
> >
>
> > > Burlington, MA
> > > Tel: (781)359-9099 x1907
> > >
> >
>
> > > -----Original
Message-----
> > > From: John Lemon
[mailto:jalemon@xxxxxxxxx]
> > > Sent: Monday, March 18, 2002 8:43
PM
> > > To: pazy@xxxxxxxxxxxx
> > > Cc: stds-802-17@xxxxxxxx
> > > Subject: Re: [RPRWG] RAH: Re: Minutes
of Rate Ad Hoc meeting
> > >
> > > Offer,
>
> >
> > > As I mentioned in the
Ad Hoc, and as Harry and Yiming
> have
reiterated,
> > > there
> > > are trade offs between utilization,
delay/jitter, and
> loss. You can
> > > choose
>
> > at most 2 of the 3. I believe there is a general clear
> preference for
> > > lowest
> > >
loss most, then for lowest delay/jitter next, and then for
highest
> > > utilization of the
available bandwidth last.
> >
>
> > > But Yiming's suggestion of
allowing this to be configurable is
> >
> intriguing.
> > > While I
believe we would always have the order I list above as the
> > > default,
>
> > I could imagine a customer wanting to change it away from
> the default.
>
> > If it
> > > were an option
that they didn't have to configure, those that
> > > wanted to
> > >
change from the default would be accommodated; and those
> that didn't
>
> > want to
> > > be bothered
with configing yet another parameter could safely
> > > ignore it.
> >
>
> > > John Lemon
> > > ----- Original Message -----
> > > From: "Offer pazy"
<pazy@xxxxxxxxxxxx>
> > > To:
"'Mike Takefman'" <tak@xxxxxxxxx>; "'Yiming Yao'"
> > > <YYao@xxxxxxxxxxxx>
> > > Cc:
<hans-j.reumerman@xxxxxxxxxxx>;
<stds-802-17@xxxxxxxx>
> > >
Sent: Monday, March 18, 2002 2:44 PM
> >
> Subject: RE: [RPRWG] RAH: Re: Minutes of Rate Ad Hoc
meeting
> > >
> > >
> > >
> > > I fully concur with Mike's response.
We have to be
> extremely careful
> > > about adding optional behavior (and
variety) to the
> standard. In my
> > > opinion, we already have far too many
options (for this
> early stage of
> > > the standard development). Options are
a nightmare (and
> if someone can
> > > help me with a stronger word, please
do :-) for users (carriers),
> > >
testers, general audience, and finally to ourselves as we
> will have to
>
> > work much harder to make all these options work together,
are
> > > consistent, and that all
combinations are covered.
> Additionally,
there
> > > is the important issue of
interoperability which is made
>
exponentially
> > > more complex with
each additional option.
> > >
> > > >From my experience, developers
often tend to "be nice to
> users"
by
> > > offering every options
possible, just to later be
> rejected by
the end
> > > users who don't have
the infrastructure, the personnel, and the
> > > knowledge to sort out the options, to decide, to
manage and
> > > to maintain
> > > their many network nodes.
> > >
> >
>
> > > Specifically, please note
that the packet loss we are
> considering
here
> > > (or considering not
allowing) is at the very low level of
> the
physical
> > > level. Look at it as
the property of the wire. And at some
>
> > point we must
> > >
establish a common model for this "wire" to be able to
> build the upper
> > > layers. This has nothing to do with the
legitimate topic
> that is being
> > > discussed of policing traffic on the
ingress points to
> the network.
> > > There of course, there are many
tradeoffs that are better
> > > left
of to the
> > > operators, and these
tradeoffs are much more relevant to
> >
> jitter, latency
> > > and the
such.
> > >
> > > Offer Pazy
> >
>
> > > Burlington, MA
> > > Tel: (781)359-9099 x1907
> > >
> >
>
> > > -----Original
Message-----
> > > From:
owner-stds-802-17@xxxxxxxxxxxxxxxxxx
> >
> [mailto:owner-stds-802-17@xxxxxxxxxxxxxxxxxx]
On Behalf Of
> > > Mike
Takefman
> > > Sent: Monday, March
18, 2002 3:37 PM
> > > To: Yiming
Yao
> > > Cc:
'hans-j.reumerman@xxxxxxxxxxx'; stds-802-17@xxxxxxxx
> > > Subject: Re: [RPRWG] RAH: Re: Minutes of Rate Ad
Hoc meeting
> > >
> > >
> > >
Yiming,
> > >
> > > speaking as a technical expert,
> > >
> > > while I
understand your desire to have LP packets
>
dropped, be aware
> > > that 802 has
never had a MAC that drops packets from the medium
> > > except due to a CRC errors.
> > >
> > > >From
a compliance testing perspective, the issue of packet drops
> > > would make it difficult (if not
impossible) to provide a test
> > >
that proved compliance if packet drops were allowed. Remember,
> > > if you can't test for compliance, it
is not a standard.
> > >
> > > I believe that proper use of reserved
BW will remove any need to
> > > drop
packets. I look forward to seeing the simulation results
> > > that show problems as a part of the
RAH.
> > >
> > >
> > >
mike
> > >
> > >
> > > >
Yiming Yao wrote:
> > > >
> > > > Hans,
> > > >
> > > >
The current draft of the RPR standard tries to achieve several
> > > objectives: high link
utilization,
> > > > guaranteed
minimum jitter for reserved HP traffic, no
> packet loss on
> > > the
ring, etc, and these
> > > >
objectives are conflicting to each other sometimes. One
> customer may
>
> > want to disallow any LP
> >
> > packet drop on the ring even this means high jitter for the
HP
> > > traffic; another may want
to
> > > > guarantee minimum
jitter to HP traffic (carrying TDM) at risk of
> > > occasionally dropping some LP
> > > > packets.
> >
> >
> > > > My suggestion is
that RPR provide a choice for the
>
customer to make
> > > his/her
decision in conflict
> > > >
resolution.
> > > >
> > > > I didn't assume the operator
wants to adjust the total
> > >
load/throughput. Maybe this can be done
>
> > > more easily if the above choice is provided.
> > > >
> >
> > Regards,
> > > >
> > > > Yiming
> > > >
> > >
> -----Original Message-----
> > > >
From: hans-j.reumerman@xxxxxxxxxxx
> >
> [mailto:hans-j.reumerman@xxxxxxxxxxx]
> > > >
Sent: Friday, March 15, 2002 1:35 AM
> >
> > To:
stds-802-17@xxxxxxxx
> > >
> Subject: [RPRWG] RAH: Re: Minutes
of Rate Ad Hoc meeting
> > >
>
> > >
> > Yiming Yao: allow customer to
choose between loss,
> > > jitter,
and
> > > utilization
> > > >
> >
> > Is the underlying assumption
that the operator of the ring
> > >
(=customer?) wants to
> > >
> adjust the total
load/throughput? Would this be for
>
> > loadbalancing purposes?
> >
> >
> > >
> regards,
> > > > Hans
> > > >
> >
> >
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > >
Hans-Jürgen Reumerman
> > >
>
Hans-J.Reumerman@xxxxxxxxxxx
> > >
> Digital Communications &
networking
> > >
pww.pfa.research.philips.com/dc/
> >
> > Philips Research
Laboratories
> > > Phone: +49 241
6003 629
> > >
> Weisshausstr.2, 52066 Aachen,
Germany
> Fax: +49 241
> > > 6003 519
> > >
>
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > >
> > >
--
> > > Michael
Takefman
tak@xxxxxxxxx
> > > Manager of
Engineering, Cisco Systems
> > > Chair IEEE 802.17 Stds WG
> > > 2000 Innovation Dr, Ottawa, Canada,
K2K 3E8
> > > voice:
613-254-3399 fax:
613-254-4867
> > >
> > >
> > >
> > >
>
>
> >
>
--------------------------------------------------------------
> --------------
>
------------------------
>
>
Name: WINMAIL.DAT
> >
WINMAIL.DAT Type: application/ms-tnef
>
>
Encoding: base64
>
> --
> Michael
Takefman
tak@xxxxxxxxx
> Manager of
Engineering, Cisco Systems
> Chair IEEE 802.17 Stds WG
> 2000 Innovation Dr, Ottawa, Canada, K2K 3E8
> voice:
613-254-3399 fax:
613-254-4867
>
>
>
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