[dat-discussions] RE: [openib-general] Re: iWARP emulationprotocol

[Kanevsky, Arkady]

But TCP connection do not need to pre-allocate recv buffers like RDMA
does.
If all RDMA connection attributes can be modified without
beraking a live connection, like RDMA read credits, then analogy
with TCP will work.
Arkady

Arkady Kanevsky                       email: arkady at netapp.com
Network Appliance                     phone: 781-768-5395
375 Totten Pond Rd.                  Fax: 781-895-1195
Waltham, MA 02451-2010          central phone: 781-768-5300
 


> -----Original Message-----
> From: Sean Hefty [mailto:mshefty at ichips.intel.com] 
> Sent: Wednesday, October 19, 2005 1:38 PM
> To: Kanevsky, Arkady
> Cc: Richard Frank; swg at infinibandta.org; 
> dat-discussions at yahoogroups.com; openib-general at openib.org; 
> Davis, Arlin R
> Subject: Re: [dat-discussions] RE: [openib-general] Re: iWARP 
> emulationprotocol
> 
> 
> Kanevsky, Arkady wrote:
> > if look at the proposal it shows 2 ways to address this.
> 
> I did notice this.
> 
> > 1. Have 2 protocols.
> > One just send SRC IP address and port, and provdie 64 bytes to ULP. 
> > Another one send both SRC and DEST info and leaves 48(+-) bytes of 
> > private data for ULP.
> 
> If the goal is to make the mapping from IP address to IB 
> address transparent, 
> then I think we want a single protocol.  Ideally, the 
> application shouldn't need 
> to know if they're connecting over iWarp, IB, or any other 
> RDMA NIC.  Any 
> solution that makes IB appear different than iWarp makes this 
> more difficult to 
> accomplish.
> 
> > 2. Have 2 protocols.
> > Split IPv4 and IPv6 methods.
> 
> Same issue as above.  This makes IB connections appear 
> differently than an iWarp 
> connection.  This is why I asked if the destination address 
> is required.  If it 
> is, then the applications need to make do with less private data.
> 
> > For IPv4 send SRC and DST addressing and 64 bytes of ULP 
> private data. 
> > For IPv6 we have several options. a. GID=IPv6 address
> 
> Unless an IP packet can be sent to a GID and be processed, I 
> don't consider a 
> GID equal to an IPv6 address.  I also don't think that we 
> should require system 
> administrators to add GIDs to IB ports just because they want 
> to add an IP 
> address to a system.
> 
> > b. use second CM frame to have carry ULP private data.
> 
> An application can make due with no private data.  They can 
> transfer whatever 
> data that need once the connection has been established, like all TCP 
> applications do.  Adding more CM messages to pass the same 
> data that should be 
> passed over the user's QP is the wrong approach.
> 
> In fact another alternative is to make all CM private data reserved.
> 
> - Sean
>