ethernet and switches, was Re: [rescue] Mozilla Firefox

Scotty Logan swl at
Sat Apr 24 15:48:00 CDT 2004

On Apr 23, 2004, at 10:09 PM, ghub005 wrote:
> If on the other hand you're wondering why I used an older loop based 
> name
> like 'FC-AL' to refer to a switched SAN topology

I've heard from various sources that switched FC actually preceded 
FC-AL, but I think FC-AL may have been standardized by ANSI first.

Now, for the pedantry:

> every link between the switch and the HBA is a loop.

Most links between HBAs and switches are actually point-to-point, with 
the HBA port acting as an N_Port (node) and the switch port acting as 
an F_Port (fabric).  If the link was a loop, the HBA would be an 
NL_Port and the switch port would be an FL_Port.

> The terms 'fibre channel switch' and 'FC-AL switch' are the same thing.

Not necessarily, since not all switches support FC-AL.  FL_Port (fabric 
loop) switch ports can support loop devices (such as older FC tape 
drives); F_Port (fabric mode) switch ports only support point-to-point 
connections.  Most switches will automatically detect loop devices and 
change the port to FL_Port, but some (like McData's Intrepid 6064) do 
not support FL_Port, so an intermediary switch or gateway is required.


Scotty Logan <scotty at>
Never take life seriously - Nobody gets out alive anyway

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