[lustre-discuss] LNET ports and connections

NeilBrown neilb at suse.com
Mon Feb 17 20:41:58 PST 2020

LNet is a peer-to-peer protocol, it has no concept of client and server.
If one host needs to send a message to another but doesn't already have
a connection, it creates a new connection.
I don't yet know enough specifics of the lustre protocol to be certain
of the circumstances when a lustre server will need to initiate a message
to a client, but I imagine that recalling a lock might be one.

I think you should assume that any LNet node might receive a connection
from any other LNet node (for which they share an LNet network), and
that the connection could come from any port between 512 and 1023


On Mon, Feb 17 2020, Degremont, Aurelien wrote:

> Hi all,
> From what I've understood so far, LNET listens on port 988 by default and peers connect to it using 1021-1023 TCP ports as source ports.
> At Lustre level, servers listen on 988 and clients connect to them using the same source ports 1021-1023.
> So only accepting connections to port 988 on server side sounded pretty safe to me. However, I've seen connections from 1021-1023 to 988, from server hosts to client hosts sometimes.
> I can't understand what mechanism could trigger these connections. Did I miss something?
> Thanks
> Aurélien
> _______________________________________________
> lustre-discuss mailing list
> lustre-discuss at lists.lustre.org
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