[stgt] iSER over iWARP

Or Gerlitz ogerlitz at mellanox.com
Sun Oct 6 07:33:49 CEST 2013

On 04/10/2013 02:20, Sushma R wrote:
> I experimented around a bit and here are my observations:
> 1. tgtd (Version 1.0.24) which comes with CentOS 6.4 distribution
> doesn't have iSER support. Configured targets as iscsi/tcp. Initiator
> is able to discover the target and login successfully.
> 2. Compiled latest code from git tree (Version 1.0.39) in iSCSI mode
> and configured targets as iscsi/tcp. Initiator is still able to
> discover targets and login successfully.
> 3. Compiled code from git tree (Version 1.0.39) for iSER support and
> configured targets as iscsi/tcp. Initiator fails to discover targets.
> Same is the case when the targets are configured as iser.

Oh, I think I got it.. when you enable iser we open an RDMA listerner on 
the RDMA equivalent of the iSCSI TCP port (say 3260),
but the iSCSI TCP part of TGT does this too. You might end up with a 
mess, I guess.

With IB and RoCE the problem doesn't exist, only with iWARP, since it 
uses TCP under the RDMA cover. its called
the "port space" problem, a solution to solve that was recently 
submitted upstream but has some way to go before
merged and available to use.

> 1542.231217 -> iSCSI Login Command
> 1542.231271 -> TCP iscsi-target > 53665 [ACK] Seq=1 Ack=49 Win=262096 Len=0 TSV=1890672 TSER=2186863
> 1542.231287 -> TCP iscsi-target > 53665 [ACK] Seq=1 Ack=293 Win=261848 Len=0 TSV=1890672 TSER=2186863
> 1542.231295 -> TCP iscsi-target > 53665 [RST, ACK] Seq=1 Ack=293 Win=0 Len=0
> 1543.231575 -> TCP 53666 > iscsi-target [SYN] Seq=0 Win=14600 Len=0 MSS=1460 TSV=2187863 TSER=0 WS=7
> 1543.231670 -> TCP iscsi-target > 53666 [SYN, ACK] Seq=0 Ack=1 Win=65535 Len=0 MSS=1460 WS=3 TSV=1891339 TSER=2187863
> 1543.231688 -> TCP 53666 > iscsi-target [ACK] Seq=1 Ack=1 Win=14720 Len=0 TSV=2187864 TSER=1891339
> 1543.231753 -> TCP [TCP segment of a reassembled PDU]

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