RE: iFCP vs FCIP

[Joshua Tseng <jtseng@NishanSystems.com>]

Hi David,

> 
> I am no FCP expert so please correct me if I am wrong. In a pure
> FCP world, there is end-to-end traffic and there is traffic that is
> destined to go between AS's. The primary difference is that there
> is an explicit route to the border gateways in the latter 
> case. In both
> the proposals, within the FCP realm the addresses are FCP based until
> they hit an edge node.  In iFCP the destination is converted to an IP
> address that represents the end node address (which may actually be
> a gateway back into FCP on the other side), in FCIP the request is
> routed to the other AS's FC border gateway and this request is
> encapsulated
> in a TCP request. Given that we are moving between AS's (I 
> believe that
> is an assumption in FCIP) can we not use iFCP and instead of 
> specifying
> the IP address of the end node, specify the IP address of the 
> other AS's
> border gateway since FCP should already be doing some encapsulation
> to route between AS's?
> 
> 	-David

Up until recently with the creation of the DMP routing protocol, the
concept of AS's (Autonomous Systems, right?) was foreign to Fibre
Channel networking.  Most Fibre Channel networks are comprised of just
a handful of switches--the largest FC network I have ever heard of
being deployed is a 15 switch fabric.  Perhaps somewhere there are
some fabrics which are bigger, but probably not by much. 
(Architecturally, a single Fibre Channel fabric has a maximum capacity
of 239 switches)

FCIP does not do anything to improve the scalability limits of
the Fibre Channel fabric.  All it does is allow extension of the
FC fabric over distances using an IP network.  The FCIP gateway is
completely invisible and non-intrusive to the Fibre Channel switches
and does not change or improve the scalability or interoperability
limits of FC fabrics.

On the other hand, an iFCP gateway actively participates in
switching and routing traffic between FC fabrics and FC devices, by
mapping FC addresses to IP addresses and routing them using standard
IP routing protocols.  Using iFCP, a storage network has the same
scalability limits as any other IP network (e.g., IPv4 address space,
etc...).

Josh