RE: When IBoE will be merged to upstream?

Liran Liss
2010-06-25T08:04:28Z

VLANs are part of L2 in Ethernet -- when you resolve a destination L3 address to an L2 address, you get the outgoing interface, which also determines the VLAN.
I think this approach has an advantage over an RDMA device per VLAN in that you keep the standard OS VLAN management (vconfig).

I wouldn't judge the RoCE spec so quickly --- it guarantees that rdma application binaries could run on any network.
What do you gain by exposing Eth-specific L2 params in the address handle?
--Liran

-----Original Message-----
From: Jason Gunthorpe [mailto:jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org]
Sent: Thursday, June 24, 2010 11:37 PM
To: Liran Liss
Cc: Hefty, Sean; Roland Dreier; Aleksey Senin; linux-rdma; monis-smomgflXvOZWk0Htik3J/w@public.gmane.org; alekseys-smomgflXvOZWk0Htik3J/w@public.gmane.org; yiftahs-smomgflXvOZWk0Htik3J/w@public.gmane.org; Tziporet Koren; alexr-smomgflXvOZWk0Htik3J/w@public.gmane.org
Subject: Re: When IBoE will be merged to upstream?

> The current behavior of ibv_create_ah() requires that the caller
> provide the L2, and if needed, L3 addressing. Any translation between
> the L3 and L2 addressing must be done before the call is made. E.g.
> ibv_create_ah does not use the GID to query the SA to obtain LIDs.
> Why doesn't IBoE follow this same model?
>
> LL: because of the RoCE spec, which states that only GID addressing is
> used at the Verbs level. The address handle fields are unchanged, and
> the L2 fields (e.g., lid) are reserved. Note that in Ethernet, you
> normally don't specify L2 addresses at the transport level (i.e.,
> sockets).

We do not have to lavishly follow the IBTA spec in the Linux implementation, especially if it makes no sense.

I think Sean is on the right track here, the AH should take the L2 as input just like for IB, and the resolution is done in librdmacm, or somehow manually.

The verbs layer is not really analogous to sockets anyhow, the librdmacm is much closer to a socket like interface, and it having a GID go into rdmacm and a full AH with L2/L3 info come out seems entirely reasonable.

BTW, what ever was decided about vlans tagging? Is that part of the AH or do you use seperate RDMA devices per vlan? Seems like a point worth considering now.

Jason