From: Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
To: Anuj Kalia <anujkaliaiitd-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
Subject: Re: Size of Infiniband packets
Date: Thu, 5 Dec 2013 16:53:34 -0700 [thread overview]
Message-ID: <20131205235334.GC20137@obsidianresearch.com> (raw)
In-Reply-To: <CADPSxAgSdWTkNBF=XEptKU0oVmqiXRVtd-m-c+ntnQyxMzDFNA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
On Thu, Dec 05, 2013 at 06:22:57PM -0500, Anuj Kalia wrote:
> I'm trying to do a back-of-the-hand calculation of the number of
> packets per second that can be transmitted over 40Gbps Infiniband. I
> need some information about the packet size to do this calculation.
>
> Suppose I do an 8 byte RDMA write over RC transport. What is the
> packet size that is transmitted on the wire? This should include
> Infiniband headers and the work request.
See page 257 (Figure 76) of IB Spec volume 1.
A RDMA write will contain:
LRH 8
BTH 12
RETH 16
data 8
ICRC 4
VCRC 2
Plus 2 bytes of framing is 52 bytes. IB is defined to sustain
continuous back-to-back packets, so
3200MB/sec / 52 bytes/packet = 615 million pkts/sec
--
Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> (780)4406067x832
Chief Technology Officer, Obsidian Research Corp Edmonton, Canada
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next prev parent reply other threads:[~2013-12-05 23:53 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-05 23:22 Size of Infiniband packets Anuj Kalia
[not found] ` <CADPSxAgSdWTkNBF=XEptKU0oVmqiXRVtd-m-c+ntnQyxMzDFNA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2013-12-05 23:53 ` Jason Gunthorpe [this message]
[not found] ` <20131205235334.GC20137-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2013-12-06 15:31 ` Suresh Shelvapille
[not found] ` <1AC3E3259C454E07A5DD2216E79F2EA8-+IkoAhRkys/CbFgIbBqbbjGjJy/sRE9J@public.gmane.org>
2013-12-06 23:08 ` Anuj Kalia
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