[Ofa_boardplus] Draft Mission Statement
grun at cray.com
Tue Mar 20 15:00:10 PDT 2018
All true. But doesn't 'accelerated' capture the spirit of it?
>From: Atchley, Scott [mailto:atchleyes at ornl.gov]
>Sent: Tuesday, March 20, 2018 2:40 PM
>To: Paul Grun <grun at cray.com>
>Cc: ofa_boardplus at lists.openfabrics.org, <ofa_boardplus at lists.openfabrics.org>
>Subject: Re: [Ofa_boardplus] Draft Mission Statement
>> On Mar 20, 2018, at 5:08 PM, Paul Grun <grun at cray.com> wrote:
>> Part 1: What do we call these things we work on? And are they networks or
>> From Doug L:
>>> So, I had originally suggested we use "RDMA enabled networks" and
>>> that got shot down because there is an existing assumption, right or
>>> wrong, that RDMA equates to IB. The term advanced networks was
>>> really meant to encompass any network setup that enables what we
>>> would traditionally think of as common RDMA functionality. So, for
>>> instance, IB and OPA are certainly in there, but we can also run RDMA
>>> functionality over standard Ethernet using iWARP, or RoCE with a
>>> lossless Ethernet, or RoCE with ECN enabled on the Ethernet. But any
>>> of these Ethernet solutions require additional software/hardware to
>>> make them work (a soft RoCE or soft iWARP driver, or actual
>>> RoCE/iWARP hardware, and in some cases specific abilities in the
>>> switches), so that's what earns them the moniker "advanced networks",
>>> because they *are* more advanced than a garden variety Ethernet
>>> deployment. But it was also meant to encompass any new fabrics that might
>come around in the future assuming they are a good fit for the OFA stacks.
>>> This then brings up the point, "What is a good fit for the OFA stacks?"
>>> I've tried to pin down the essence of this. After a lot of thought,
>>> I think the core, defining element of what is a good fit for the OFA
>>> stacks is any technology that enables application direct network I/O
>>> (ADNIO I guess?). You can't say "it must be RDMA capable" because
>>> not everything we support is truly RDMA (USNic for one, but even just
>>> the verbs API has non-RDMA components in that post_send/recv are not
>>> truly RDMA operations, but instead are merely application direct
>>> I/O). (snip)
>> (snipped for brevity)
>> Whether the pipes are queue pairs, or fabric endpoints, or a virtual
>> NIC with our
>>> own MAC address so that all packets to our MAC come directly to us,
>>> that's all implementation details. The core feature is Application Direct
>> From Eddie Wai:
>> Although I understand the use of the broader term "Application Direct Network
>I/O enabled networks", but it seems to be invading the DPDK territory.
>> From Sean Hefty:
>> I too prefer something like application direct I/O over the term RDMA.
>> Paul's Comment:
>> Doug has the essence of why the words 'Advanced Networks' were chosen -
>clearly, our charter does not (currently) include garden variety sockets.
>> One issue I have with Doug's statement is this: "...assuming they are a good fit
>for the OFA stacks." I want to caution us not to limit our thinking to current
>verbs-based stacks, but to also include other stacks e.g. libfabrics, and whatever
>may come in the future. I'm not sure if that's what Doug had in mind or not.
>> Personally, I strongly prefer that we not invent a new term in the midst of the
>missions statement, so I would advocate against Application Direct Network I/O
>enabled networks, or even application direct I/O. Can we agree on 'accelerated'
>with no loss of generality?
>> As for the word 'Networks' versus 'Fabrics' - no matter what, we are bound to
>please roughly 1/2 the people at any given time. Early on in the process we had
>settled on 'fabrics' because it differentiates us from various networking standards
>bodies, and because 'fabrics' seems to suggest a smaller diameter fabrics than a
>classical 'network' (e.g. IP is a network) might encompass. Note that there is an
>implication here that the OFA doesn't focus on WANs, even though we have done
>a lot of work in the past on extending IB over the WAN.
>> I suggest we zero in on 'Accelerated Fabrics’.
>We used to use the term “kernel-bypass” to indicate user-space application direct
>access of hardware. :-)
>The “bad” things about Berkeley sockets is the file/pipe semantic which requires
>buffering on send and again on receive. Data must be copied from the application
>buffer before sending and copied to the user buffer after receiving. OFA’s
>umbrella covers non-socket interfaces (Verbs, PSM, libfabric) that allow direct
>access from/placement in tagged/untagged user buffers as well as memory
>operations (i.e. atomics).
>It is these additional semantics that make these interfaces so beneficial (i.e.
>lower latency, higher bandwidth, better semantic match to the application’s
>needs). OFA supports more than simply accelerating communication. We support
>more semantically rich communication.
>Unfortunately, I do not have a catchy phrase that captures that.
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