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<DIV><SPAN class=896424205-26072007><FONT face="Palatino Linotype"
color=#0000ff><STRONG>I propose that when there is no MTU in the partition
policy file OpenSM use a </STRONG></FONT></SPAN></DIV>
<DIV><SPAN class=896424205-26072007><FONT face="Palatino Linotype"
color=#0000ff><STRONG>configurable default from: </STRONG></FONT></SPAN><SPAN
class=896424205-26072007><STRONG><FONT face="Palatino Linotype"
color=#0000ff>/etc/cache/opensm/opensm.opt.</FONT></STRONG></SPAN></DIV>
<DIV><SPAN class=896424205-26072007><STRONG><FONT face="Palatino Linotype"
color=#0000ff>Something like:</FONT></STRONG></SPAN></DIV>
<DIV><SPAN class=896424205-26072007><STRONG><FONT face="Palatino Linotype"
color=#0000ff># The default MTU to be used for IPoIB and other MCGs when the
partition-policy </FONT></STRONG></SPAN></DIV>
<DIV><SPAN class=896424205-26072007><STRONG><FONT face="Palatino Linotype"
color=#0000ff># does not provide exact value. The default is the lowest possible
MTU</FONT></STRONG></SPAN></DIV>
<DIV><SPAN class=896424205-26072007><STRONG><FONT face="Palatino Linotype"
color=#0000ff>mcg_default_mtu 1</DIV></FONT></STRONG></SPAN>
<DIV><SPAN class=896424205-26072007><STRONG><FONT face="Palatino Linotype"
color=#0000ff></FONT></STRONG></SPAN> </DIV>
<DIV><SPAN lang=en-gb><B><I><FONT face="Monotype Corsiva" color=#0000ff
size=6>Eitan Zahavi</FONT></I></B><I></I></SPAN> <BR><SPAN lang=en-gb><FONT
face=Tahoma size=2>Senior Engineering Director, Software Architect</FONT></SPAN>
<BR><SPAN lang=en-gb><FONT face=Tahoma size=2>Mellanox Technologies
LTD</FONT></SPAN> <BR><SPAN lang=en-gb><FONT face=Tahoma
size=2>Tel:+972-4-9097208<BR>Fax:+972-4-9593245</FONT></SPAN> <BR><SPAN
lang=en-gb><FONT face=Tahoma size=2>P.O. Box 586 Yokneam 20692
ISRAEL</FONT></SPAN> </DIV>
<DIV> </DIV><BR>
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<FONT face=Tahoma size=2><B>From:</B> Shirley Ma [mailto:xma@us.ibm.com]
<BR><B>Sent:</B> Wednesday, July 25, 2007 10:45 PM<BR><B>To:</B> Eitan
Zahavi<BR><B>Cc:</B> general@lists.openfabrics.org; Hal
Rosenstock<BR><B>Subject:</B> RE: [ofa-general] Re: openSM: Different IB
MTUs<BR></FONT><BR></DIV>
<DIV></DIV>
<P>Hello Eitan, Hal,<BR><BR>Thanks. It's good openSM has the configuration
option to set up these attributes in MC. Is this a good idea to add below to
openSM: When there is no MTU defined in the configuration file, SM can pick up
the smallest link MTU in the fabrics by default? MTU is unlikely rate, slower
rate might indicate the cablling problem. So using the smallest link MTU in
the fabrics might not be a bad choice for MC by default. The reason I request
here is to create IP multicast group, MTU is not an attribute of the group.
When mapping IP multicast to IB multicast, IB muliticast might fail because of
different IB link MTU size in the group, but IP multicast group will be
successful without knowing the failure. If admin sets MTU in configuration
file, admin would know this failure. Otherwise, admin/users could spend too
much time on debugging their broken multicasting
applications.<BR><BR>Thanks<BR>Shirley Ma<BR><BR><IMG height=16
alt='Inactive hide details for "Eitan Zahavi" <eitan@mellanox.co.il>'
src="cid:896424205@26072007-1411" width=16 border=0>"Eitan Zahavi"
<eitan@mellanox.co.il><BR><BR><BR>
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<UL>
<UL>
<UL><B><FONT size=2>"Eitan Zahavi"
<eitan@mellanox.co.il></FONT></B><FONT size=2> </FONT>
<P><FONT size=2>07/25/07 12:25 PM</FONT></P></UL></UL></UL></UL></TD>
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<DIV align=right><FONT size=2>To</FONT></DIV></TD>
<TD width="100%"><IMG height=1 alt=""
src="cid:896424205@26072007-1418" width=1 border=0><BR><FONT
size=2>"Hal Rosenstock" <hal.rosenstock@gmail.com>, Shirley
Ma/Beaverton/IBM@IBMUS</FONT></TD></TR>
<TR vAlign=top>
<TD width="1%"><IMG height=1 alt=""
src="cid:896424205@26072007-1418" width=58 border=0><BR>
<DIV align=right><FONT size=2>cc</FONT></DIV></TD>
<TD width="100%"><IMG height=1 alt=""
src="cid:896424205@26072007-1418" width=1 border=0><BR><FONT
size=2><general@lists.openfabrics.org></FONT></TD></TR>
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<TD width="1%"><IMG height=1 alt=""
src="cid:896424205@26072007-1418" width=58 border=0><BR>
<DIV align=right><FONT size=2>Subject</FONT></DIV></TD>
<TD width="100%"><IMG height=1 alt=""
src="cid:896424205@26072007-1418" width=1 border=0><BR><FONT
size=2>RE: [ofa-general] Re: openSM: Different IB
MTUs</FONT></TD></TR></TBODY></TABLE>
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<TR vAlign=top>
<TD width=58><IMG height=1 alt=""
src="cid:896424205@26072007-1418" width=1 border=0></TD>
<TD width=336><IMG height=1 alt=""
src="cid:896424205@26072007-1418" width=1
border=0></TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE><BR><B><FONT
color=#0000ff size=4>Hi Shirley,</FONT></B><BR><FONT
size=4></FONT><BR><B><FONT color=#0000ff size=4>I think I understand where
your question comes from...</FONT></B><BR><B><FONT color=#0000ff size=4>Many
have issue with heterogonous fabrics where not all nodes have same MTU or
Speed.</FONT></B><BR><B><FONT color=#0000ff size=4>Especially when IPoIB
relies on all nodes joining the broadcast group.</FONT></B><BR><FONT
size=4></FONT><BR><B><FONT color=#0000ff size=4>The term "join" for multicast
groups is a little overloaded.</FONT></B><BR><B><FONT color=#0000ff size=4>If
a node joins an existing MC group it has to have a rate (speed * width) >
MCG.rate and support MTU > MCG.MTU otherwise it is
denied.</FONT></B><BR><B><FONT color=#0000ff size=4>If the join is actually a
"create" the node has to provide the rate and MTU which define the MCG
values.</FONT></B><BR><FONT size=4></FONT><BR><B><FONT color=#0000ff size=4>To
allow for administrator to control the IPoIB MCGs MTU and rate OpenSM provides
the means to control these</FONT></B><BR><B><FONT color=#0000ff size=4>values
per partition. See the doc/partition-config.doc</FONT></B><FONT size=4>
</FONT><BR><B><FONT color=#0000ff size=4>Still the administrator should know
what would be the lowest MTU and rate the nodes expected to join the IPoIB
subnet have.</FONT></B><BR><B><FONT color=#0000ff size=4>The tradeoff is in
the hands of the administrator who can set a value that will prevent slow
nodes from joining the group, </FONT></B><BR><B><FONT color=#0000ff size=4>or
assign a low value that will fit all nodes but slow down communication
...</FONT></B><BR><FONT size=4></FONT><BR><B><FONT color=#0000ff
size=4>EZ</FONT></B>
<P><B><I><FONT color=#0000ff size=7>Eitan Zahavi</FONT></I></B><FONT size=4>
</FONT><BR>Senior Engineering Director, Software Architect<FONT size=4>
</FONT><BR>Mellanox Technologies LTD<FONT size=4>
</FONT><BR>Tel:+972-4-9097208<BR>Fax:+972-4-9593245<FONT size=4>
</FONT><BR>P.O. Box 586 Yokneam 20692 ISRAEL<FONT size=4> </FONT>
<P><FONT size=4></FONT><BR><BR>
<HR align=left width="100%" SIZE=2>
<B>From:</B> general-bounces@lists.openfabrics.org [<A
href="mailto:general-bounces@lists.openfabrics.org">mailto:general-bounces@lists.openfabrics.org</A>]
<B>On Behalf Of </B>Hal Rosenstock<B><BR>Sent:</B> Wednesday, July 25, 2007
10:01 PM<B><BR>To:</B> Shirley Ma<B><BR>Cc:</B>
general@lists.openfabrics.org<B><BR>Subject:</B> [ofa-general] Re: openSM:
Different IB MTUs<FONT size=4><BR></FONT><BR><FONT
size=4>Shirley,<BR></FONT><BR><FONT size=4>On 7/25/07, </FONT><B><FONT
size=4>Shirley Ma</FONT></B><FONT size=4> <</FONT><A
href="mailto:xma@us.ibm.com"><U><FONT color=#0000ff
size=4>xma@us.ibm.com</FONT></U></A><FONT size=4>> wrote: </FONT>
<UL><FONT size=4>Hal,<BR><BR>Thanks for your prompt reply. I am asking for
how openSM handle different link MTUs in SA MCMemberRecord MTU. For example,
if we have some links MTU as 2K, some links MTU as 1K. Then when enabling
IPoIB, how does SM decide IPoIB broadcast group MCMemberRecord MTU size?
When creating an IB multicast group from a 2K MTU node first, which PMTU
value is attaching to this IB multicast group MCMemberRecord MTU?
</FONT></UL><BR><FONT size=4></FONT><BR><FONT size=4>MCMemberRecord MTU gets
the group MTU (when created). This is either this first joiner with sufficient
components or preconfigured (and MTU can be set in the config). If a joiner
has insufficient MTU for the group, it is denied. </FONT><BR><FONT
size=4></FONT><BR><FONT size=4>-- Hal</FONT><BR><FONT size=4></FONT><BR>
<UL><FONT size=4>Thanks<BR>Shirley Ma<BR><BR></FONT><IMG height=16
alt='Inactive hide details for "Hal Rosenstock" <hal.rosenstock@gmail.com>'
src="cid:896424205@26072007-141F" width=16><FONT size=4>"Hal Rosenstock"
< </FONT><A href="mailto:hal.rosenstock@gmail.com" target=_blank><U><FONT
color=#0000ff size=4>hal.rosenstock@gmail.com</FONT></U></A><FONT
size=4>><BR><BR></FONT>
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<UL>
<UL><B>"Hal Rosenstock" <</B><A
href="mailto:hal.rosenstock@gmail.com"
target=_blank><B><U><FONT
color=#0000ff>hal.rosenstock@gmail.com</FONT></U></B></A><B>></B>
<P>07/25/07 10:57 AM</P></UL></UL></UL></UL></UL></UL></UL></UL></TD>
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<TD width="22%"><IMG height=1 src="cid:896424205@26072007-1426"
width=58>
<DIV align=right>To</DIV></TD>
<TD width="78%"><IMG height=1 src="cid:896424205@26072007-1426"
width=1><BR>Shirley Ma/Beaverton/IBM@IBMUS</TD></TR>
<TR vAlign=top>
<TD width="22%"><IMG height=1 src="cid:896424205@26072007-1426"
width=58>
<DIV align=right>cc</DIV></TD>
<TD width="78%"><IMG height=1 src="cid:896424205@26072007-1426"
width=1><U><FONT color=#0000ff><BR></FONT></U><A
href="mailto:general@lists.openfabrics.org"
target=_blank><U><FONT
color=#0000ff>general@lists.openfabrics.org</FONT></U></A></TD></TR>
<TR vAlign=top>
<TD width="22%"><IMG height=1 src="cid:896424205@26072007-1426"
width=58>
<DIV align=right>Subject</DIV></TD>
<TD width="78%"><IMG height=1 src="cid:896424205@26072007-1426"
width=1><BR>Re: openSM: Different IB MTUs</TD></TR></TBODY></TABLE>
<TABLE cellSpacing=0 cellPadding=0 width="100%" border=0>
<TBODY>
<TR vAlign=top>
<TD width="15%"><IMG height=1 src="cid:896424205@26072007-1426"
width=1></TD>
<TD width="85%"><IMG height=1 src="cid:896424205@26072007-1426"
width=1></TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE><FONT
size=5><BR>Shirley,</FONT><FONT size=4><BR></FONT><FONT size=5><BR>On
7/25/07, </FONT><B><FONT size=5>Shirley Ma</FONT></B><FONT size=5>
<</FONT><A href="mailto:xma@us.ibm.com" target=_blank><U><FONT
color=#0000ff size=4> </FONT></U><U><FONT color=#0000ff
size=5>xma@us.ibm.com</FONT></U></A><FONT size=5>> wrote: </FONT>
<UL>
<UL><FONT size=5>Hello Hal,<BR><BR>How does openSM handle CAs with
different MTUs in the same subnet? For example, IPoIB broadcast group
MTU, IB multicast group PMTU? Does openSM pick up the smallest MTU in
the subnet? </FONT></UL></UL><FONT size=4><BR></FONT><FONT size=5><BR>Are
you asking about link MTU, SA PathRecord/MultiPathRecord MTU, SA
MCMemberRecord MTU, or all of these ?</FONT><FONT size=4><BR></FONT><FONT
size=5><BR>-- Hal </FONT>
<UL>
<UL><FONT size=5>Thanks<BR>Shirley
Ma</FONT></UL></UL><BR></UL><BR></BLOCKQUOTE></BODY></HTML>