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Members of the RAH,
It is interesting that a thread with subject "minutes of the RAH meeting"
is still circulating on the RPR-WG mailing list, but no one actually bothered
to take any minutes for the 3/26 meeting!
Could some one please summarize what happened.
Thanks, Siamack
John Lemon wrote:
Devendra, In
order to do this, one would have to have a *very* trusted client,
which has not been an assumption in past MAC standards. I would argue that
either clients are completely trustworthy and you allow them to flow control
and rate shape all traffic, or clients are not completely trustworthy and
you never allow them to touch a packet not destined for them. I don't see
any point in-between. Frankly, while allowing clients to interact with
the transit path is intriguing from an engineering point of view, I doubt
it would be acceptable to many people. jl
----- Original Message -----
Sent: Wednesday, March 27, 2002 5:22
PM
Subject: RE: [RPRWG] RAH: Re: Minutes
of Rate Ad Hoc meeting
Hi
team,Looks
if my response to Mike's earlier mail was not noticed as everyone is talking
about the deciding the buffer size to guarantee a loss less ring. I would
like to repeat the option I suggested in that mail. Basically
the packets which can not be delivered by MAC within a certain time for
a given priority could be sent to upper layer as "packets in waiting".
Since MAC can not be expected to maintains flows, and out of order packets
have to be avoided, once a packet of a certain priority goes on the path
of "packets in waiting", the MAC will have to keep on sending all packets
of that priority to upper layer till "Waiting Queue Empty" indication comes
from upper layer. Also, as I mentioned in previous mail, it would be possible
for a MAC to emulate the behavior of this upper layer by having suitable
size of buffer or allow for loss, but then it would be implementation detail
and standard would not have to worry about it.The
buffer size option is not scalable one and it will be very contentious
issue (at least for a MAC).Regards,
Devendra Tripathi
CoVisible Solutions, Inc
(In India: VidyaWeb (India) Pvt Ltd)
90 Great Oaks Blvd #206
San Jose, Ca 95119
Tel: (408)226-6800,
Fax: (408)226-6862
Harry, I
am not suggesting a lossy ring. I requested one, but most of you convincedme
that will never happen in RPR. So, I am moving on with an assumption ofa
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 thana
certain size of LPTB buffer must designed in. Obviously the size of thisLPTB
depends on the levels of HP traffic and the RTT. Everything has aconsequence
- there is no freee lunch !So,
the corollary, that if the LPTB size is fixed on the ring than for a givenring
circumference only a certain level of HP traffic, with absolute guarantees on
jitter, can be provided. This implies that carriers would have to predictthe
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 inversionthan
one must AVOID situations that creates a scenario to pick oneover
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 toin
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 tohave
a loss less ring, no priority inversion and a single 2 MTU TB. I would
thinkthe
a single TB with ability to buffer 2 packets cries out for some methodto
AVOID a situation that will force priority inversion to honor a loss less
ringrequirement.
I must be missing something !The
real issue is that I am not fixated on preserving any implementation atthe
cost of having an absurd standard. On the other hand, I am tolerant to
thebig
guns who want to do this I think we need to ensure that the RPR WGdo
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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