[lustre-discuss] LNET ports and connections

[NeilBrown]

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
(LNET_ACCEPTOR_MIN_PORT to LNET_ACCEPTOR_MAX_PORT).

NeilBrown



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
>
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> lustre-discuss mailing list
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