Re: [ofa-general] [PATCH v3] iw_cxgb3: Support"iwarp-only"interfacesto avoid 4-tuple conflicts.

[Steve Wise <swise@opengridcomputing.com>]

Kanevsky, Arkady wrote:
> Sean,
> IB aside,
> it looks like an ULP which is capable of being both RDMA aware and RDMA
> not-aware,
> like iSER and iSCSI, NFS-RDMA and NFS, SDP and sockets, 
> will be treated as two separete ULPs.
> Each has its own IP address, since there is a different IP address for
> iWARP
> port and "regular" Ethernet port. So it falls on the users of ULPs to
> "handle" it
> via DNS or some other services.
> Is this "acceptable" to users? I doubt it.
> 
> Recall that ULPs are going in opposite directions by having a different
> port number for RDMA aware and RDMA unaware versions of the ULP.
> This way, ULP "connection manager" handles RDMA-ness under the covers,
> while users plug an IP address for a server to connect to.
> Thanks,

Arkady, I'm confused about how this proposed design changes the behavior 
of the ULPs that run on TCP and iWARP.  I don't see much difference from 
the point of view of the ULPs.

The NFS-RDMA server, for example, will not need to change since it binds 
to address 0.0.0.0 which will translate into a bind/listen on the 
specific iwarp address for each iwarp device on the rdma side, and 
address 0.0.0.0 for the TCP side.

Am I missing your point?

The real pain, IMO, with this solution is that it FORCES the admins to 
use 2 subnets when 1 is sufficient if the net maintainers would unify 
the port space...

Steve.



> 
> Arkady Kanevsky                       email: arkady@netapp.com
> Network Appliance Inc.               phone: 781-768-5395
> 1601 Trapelo Rd. - Suite 16.        Fax: 781-895-1195
> Waltham, MA 02451                   central phone: 781-768-5300
>  
> 
>> -----Original Message-----
>> From: Sean Hefty [mailto:sean.hefty@intel.com] 
>> Sent: Thursday, September 27, 2007 3:12 PM
>> To: Kanevsky, Arkady; Sean Hefty; Steve Wise
>> Cc: netdev@vger.kernel.org; rdreier@cisco.com; 
>> linux-kernel@vger.kernel.org; general@lists.openfabrics.org
>> Subject: RE: [ofa-general] [PATCH v3] iw_cxgb3: 
>> Support"iwarp-only"interfacesto avoid 4-tuple conflicts.
>>
>>> What is the model on how client connects, say for iSCSI, when client 
>>> and server both support, iWARP and 10GbE or 1GbE, and would like to 
>>> setup "most" performant "connection" for ULP?
>> For the "most" performance connection, the ULP would use IB, 
>> and all these problems go away.  :)
>>
>> This proposal is for each iwarp interface to have its own IP 
>> address.  Clients would need an iwarp usable address of the 
>> server and would connect using rdma_connect().  If that call 
>> (or rdma_resolve_addr/route) fails, the client could try 
>> connecting using sockets, aoi, or some other interface.  I 
>> don't see that Steve's proposal changes anything from the 
>> client's perspective.
>>
>> - Sean
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