Re: iSCSI and jumbo frames

[BERTRAND Joël <joel.bertrand%systella.fr@localhost>]

Michael van Elst a écrit :
> joel.bertrand%systella.fr@localhost (=?UTF-8?Q?BERTRAND_Jo=c3=abl?=) writes:
> 
>> 	Of course, I have reconfigured all interfaces, and wm0's mtu is set to
>> 9000 :
>> legendre# ifconfig wm0
>> wm0: flags=0x8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 9000
>> ...
> 
>> 	On qNAP, I have set also mtu to 9000. But iSCSI packets are not greater
>> than 1448 bytes :
> 
>> 23:38:56.260255 IP legendre.systella.fr.65516 >
>> euclide.systella.fr.iscsi-target: Flags [.], seq 936737888:936739336,
>> ack 4553905, win 4197, options [nop,nop,TS val 92106 ecr 887624208],
>> length 1448
> 
> 
> iscsi isn't any more special than other protocols. It just uses TCP
> connections.
> 
> TCP segment size is calculated from the route MTU which is based on
> the interface MTU when the connection is started. The segment size
> is also adjusted (reduced) when errors are reported.

	I haven't seen any error.

> Did you reconnect iSCSI after the changes ?

	If I remember, I have rebooted.

> Is there a route MTU (netstat -r will tell, a "-" means to inherit from
> interface) ?

legendre# netstat -r | grep 192.168.12
192.168.12/24      link#1             UC          -        -      -  wm0

> Is there anything between both machines (switch, router) that does not
> support jumbo frames ?

	There is no equipment between wm0 and NAS.

	I will try to restart iscsid but I'm pretty sure this system was
rebooted with new mtu in /etc/ifconfig.wm0.

	Best regards,

	JKB