Subject: RE: [Ipoverib] recharter consideration

From: Michael Krause <[email-masked]>
Date: Thu, 17 Oct 2002 09:29:24 -0700

At 11:26 AM 10/17/2002 -0400, Rosenstock, Hal wrote:
>Hi,
>
>I would like to elaborate on other causes of dropping (loss) in an IB subnet
>in the face of congestion. Aside from the CRC errors, when either Head of
>Queue lifetime or switch lifetime are exceeded in IB switches these packets
>are also dropped and need to be included in the discussion of loss. This
>brings in the notion of traffic patterns.
>
>Wouldn't RC have benefit in such highly utilized fabrics and UC might not as
>entire messages would need to be retransmitted rather than an individual
>segment of a message ?

The drop times for HOL blocking in an individual switch element can be 
quite large, i.e. measured in seconds if desired.  In general, this type of 
drop will not occur if all components are acting well, i.e. leaf 
destination endnodes are consuming packets and returning flow control.

I will also note that if the fabric is this congested, then adding in the 
additional packets for RC acknowledgement only makes things worse not 
better.  As the IBTA works out congestion control and QoS, it is quite 
likely that this type of drop will become even rarer as the injection rates 
and event notification will present to prevent such occurrences.

Mike

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https://www1.ietf.org/mailman/listinfo/ipoverib

---

From: "Bill Strahm" <[email-masked]>
Date: Thu, 17 Oct 2002 10:19:04 -0700

<WG Chair Hat on>
We seem to have a difference of opinions here, some people prefering UC,
some RC.  While this is a VERY interesting conversation, I am not sure
that it needs to happen under the auspects of a recharter.  Could we get
rough concensus that we want to discuss alternative L2 (from the IP
stacks perspective) encodings in the charter, and then under the guise
of providing that encoding discuss which IB L4 to encode in (possibly
both and let a bake-off/interop determine which has better performance).
Keep up the discussion of encapsulations, lets just put it under a
different thread heading that doesn't tie it to the WG recharter.

Also something that I would like to see added to the charter is pushing
the encapsulation drafts up the standards track.  To do this we need to
get our first RFC, wait 6 months, then have interop/bakeoffs to get some
field experience with the protocols.  I am interested in knowing which
entities might be ready for a first bakeoff in the April/May timeframe,
and possibly again 3-6 months later.  I would also like to know who
might be willing to host such a meeting, writeup proposed test plans,
etc. etc. etc.  I am trying to ask this WAY early because I know that
budgets are down and this is something that many participants will need
to budget for in their 2003 budgets.
<WG Chair Hat off>

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf
Of Michael Krause
Sent: Thursday, October 17, 2002 9:29 AM
To: Rosenstock, Hal; Vivek Kashyap
Cc: [email-masked]; [email-masked]
Subject: RE: [Ipoverib] recharter consideration

At 11:26 AM 10/17/2002 -0400, Rosenstock, Hal wrote:
>Hi,
>
>I would like to elaborate on other causes of dropping (loss) in an IB 
>subnet in the face of congestion. Aside from the CRC errors, when 
>either Head of Queue lifetime or switch lifetime are exceeded in IB 
>switches these packets are also dropped and need to be included in the 
>discussion of loss. This brings in the notion of traffic patterns.
>
>Wouldn't RC have benefit in such highly utilized fabrics and UC might 
>not as entire messages would need to be retransmitted rather than an 
>individual segment of a message ?

The drop times for HOL blocking in an individual switch element can be 
quite large, i.e. measured in seconds if desired.  In general, this type
of 
drop will not occur if all components are acting well, i.e. leaf 
destination endnodes are consuming packets and returning flow control.

I will also note that if the fabric is this congested, then adding in
the 
additional packets for RC acknowledgement only makes things worse not 
better.  As the IBTA works out congestion control and QoS, it is quite 
likely that this type of drop will become even rarer as the injection
rates 
and event notification will present to prevent such occurrences.

Mike

_______________________________________________
IPoverIB mailing list
[email-masked] https://www1.ietf.org/mailman/listinfo/ipoverib

---

From: "Bill Strahm" <[email-masked]>
Date: Thu, 17 Oct 2002 10:19:04 -0700

<WG Chair Hat on>

-----Original Message-----

Mike

---

From: Michael Krause <[email-masked]>
Date: Thu, 17 Oct 2002 11:19:40 -0700

>different thread heading that doesn't tie it to the WG recharter.

Fine by me.

Mike

---

From: Michael Krause <[email-masked]>
Date: Thu, 17 Oct 2002 11:19:40 -0700

Fine by me.

Mike