[Rdma-developers] Re: [openib-general] OpenIB and OpenRDMA: Convergence on common RDMA APIs and ULPs for Linux

[Caitlin Bestler]

________________________________

	From: rdma-developers-admin at lists.sourceforge.net
[mailto:rdma-developers-admin at lists.sourceforge.net] On Behalf Of
Michael Krause
	Sent: Friday, May 27, 2005 7:25 AM
	To: Sukanta ganguly
	Cc: openib-general at openib.org;
rdma-developers at lists.sourceforge.net
	Subject: Re: [Rdma-developers] Re: [openib-general] OpenIB and
OpenRDMA: Convergence on common RDMA APIs and ULPs for Linux
	
	
	At 06:40 AM 5/27/2005, Sukanta ganguly wrote:
	

		Venkata,
		   How will that work? If the RNIC offloads RDMA and
		TCP completely from the Operating System and does not
		share any state information then the application
		running on the host will never be in the position to
		utilize the socket interface to use the communication
		logic to send and receive data between the remote node
		and itself. Some information needs to be shared. How
		much of it and what exactly needs to be shared is the
		question.


	Ok.  It all depends upon what level of integration / interaction
a TOE and thus a RNIC will have with the host network stack.  For
example, if a customer wants to have TCP and IP stats kept for the
off-loaded stack even if it is just being using for RDMA, then there
needs to be a method defined to consolidate these stats back into the
host network stack tool chain.  Similarly, if one wants to maintain a
single routing table to manage, etc. on the host, then the RNIC needs to
access / update that information accordingly.  One can progress through
other aspects of integration, e.g. connection management, security
interactions (e.g. DOS protection), and so forth.  What is exposed again
depends upon the level of integration and how customers want to manage
their services.  This problem also exists for IB but most people have
not thought about this from a customer perspective and how to integrate
the IB semantics into the way customers manage their infrastructures, do
billing, etc.  For some environments, they simply do not care but if IB
is to be used in the enterprise space, then some thought will be
required here since most IT don't see anything as being "free" or
self-managed.
	
	Again, Sockets is an application API and not how one
communicates to a TOE or RDMA component.  The RNIC PI has been proposed
as an interface to the RDMA functionality.  The PI supports all of the
iWARP and IB v 1.2 verbs.  
	
	Mike
	 
	 

I'd like to add that RNIC-PI is planning on explicitly defining some of
these "obvious" dependencies 
between the RDMA stack and the primary IP stack. For example, the RDMA
stack cannot maintain
any connection in a state that contradicts current IP stack routing. It
has to adapt or break the connection.
We can't have an RNIC that has its own ARP table that is not in sync
with the host's ARP table.
 
An iWarp RDMA stack gains the benefit of many pre-existing network
services (such as DNS, ARP
and routing). But that also carries with it the need to not contradict
those exisiting services. So it is
both a benefit and a restriction -- and a major divergence from an IB
RDMA stack.
 
  
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