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At 03:55 PM 2/13/2007, Sean Hefty wrote:<br>
<blockquote type=cite class=cite cite="">>A LID is subnet local on
that we can all agree. The CM Req contains<br>
>either the LID of a local subnet CA or the LID a local router which
will<br>
>move the packet to the next hop to the destination.
12.7.11 is basically<br>
>saying that the remote LID is the router's LID of the local subnet's
router<br>
>Port. 12.7.21 also refers to the remote LID but in each
subnet that is<br>
>either the router Port's LID or the destination CA.<br><br>
This isn't my interpretation.<br><br>
12.7.11 Local Port LID: When local and remote ports are on
different subnets,<br>
this field must be the LID of the router that the *passive* side will
target for<br>
the return path.<br><br>
The CM REQ carries the LIDs for the remote (passive side) subnet.
This is what<br>
the passive side needs to configure the QP, not the active side LID
information.<br>
(See address vector information for 11.2.4.2 - page 574.)<br><br>
So, the CM REQ is _sent_ to either the LID of the local subnet CA or the
LID of<br>
a local router port, but _contains_ the LIDs from the remote
subnet.</blockquote><br>
In volume 1, version 1.2, page 574 it states:<br><br>
<img src="cid:.0" width=540 height=136 alt="Emacs!"><br><br>
12.7.11 <br>
<img src="cid:.1" width=438 height=98 alt="Emacs!"><br>
Both of these statements refer to the local subnet's LID for the router
port being used by the local CA to communicate to a remote
subnet. The IB architecture is built upon the concept that no
subnet local information knowledge is required beyond the subnet itself
to establish communication across subnets. Perhaps the
various wordings are a bit confusing but the CM protocol should not be
concerned with a remote subnet's LID or any validation of such remote
subnet information. All it needs to do is communicate what is
global so that a remote endnode can respond correctly. It is up to
the router and the associated router protocol to perform any global to
subnet local mapping which includes the LID and LRH
generation. The router must work with each subnet's SM / SA
to provide the necessary global to subnet local mappings which are then
queried by the CM agent to find the appropriate router Port.
There is no requirement in the specification to ever communicate across a
subnet anything that is strictly subnet local. LID is a strictly
subnet local value and is not shared. Again, the passive here
refers to the subnet local router LID and not the remote subnet's
LID. <br><br>
Mike</body>
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