RE: Differences between iSCSI Router (ex. CISCO RN5420) and iSCSI Switch (ex. SANRAD Switch 3000)

[Camden Ford <cford@Brocade.COM>]

Nike,

 

Please be careful about the difference between technical capabilities and Marketing fluff.  Cisco's iSCSI Router is simply a  bridge between FC and iSCSI.  It performs protocol conversion for SCSI commands encapsulated in iSCSI on TCP and SCSI commands encapsulated in FC.  This product also provides simplistic mapping between iSCSI devices and FC domains.

 

I am not familiar with the SANRAD switch, but I suspect that provides very similar capabilities.

 

If you were to compare either of these products to our notion of Switching and Routing in the IP/Ethernet world, these are neither Switches or Routers....but simple Bridges, much like the early Ethernet Bridges.

 

iSCSI switches are simple Ethernet Switches or any other switch that can switch or route TCP/IP.  Because iSCSI utilizes TCP/IP, the iSCSI protocol rides as a byte stream on top of TCP.  Therefore, most switches are unaware that the packets that they are switching or routing are actually iSCSI.  They simply appear as another TCP byte stream.  So if you think in terms of Layer X switching, a simple Layer 2 switch is a switch based in a transports like EThernet, a Layer 3 switch is a simple version of a router with IP forwarding inmplemented in HW.  A Layer 4 switch can prioritize traffic based on TCP connections.  In order to provide intelligence in a switch that recognizes iSCSI, it would be somewhere in Layer 5-7 depending on what you filter on.

 

I would imaging that in order for any product to be a Storage Router, there would have to be the notion of Global Addressing of storage elements....something which does not exist today.

 

Technically, FC switching is based on logical addressing, and not physical addresses, so it is most similar to Layer 3 switching in IP/EThernet....which some might call a router.

 

Camden ford

-----Original Message-----
From: Nike Chen [mailto:nikechen@ksts.seed.net.tw]
Sent: Tuesday, January 15, 2002 12:29 AM
To: ips@ece.cmu.edu
Subject: Differences between iSCSI Router (ex. CISCO RN5420) and iSCSI Switch (ex. SANRAD Switch 3000)

Hi All:

 

Would anybody tell me the function differences between iSCSI Router and Switch,

or just like performance difference in Layer 3 switch and Router?

When it say it is a iSCSI switch, what level do it operate, level 2, 3 or 4?

When it say it is a iSCSI Router, what level do it operate, or just a protocol

converting gateway?

Is there any definition for iSCSI Router or iSCSI switch?

 

Thanks,

Nike