[openib-general] IPoIB Loading and Starting

[Yaron Haviv]

> -----Original Message-----
> From: openib-general-bounces at openib.org 
> [mailto:openib-general-bounces at openib.org] On Behalf Of Roland Dreier
> Sent: Saturday, September 25, 2004 6:17 PM
> To: Michael Krause
> Cc: openib-general at openib.org
> Subject: Re: [openib-general] IPoIB Loading and Starting
> 
>     Michael> I would have thought this would be part of the IP over IB
>     Michael> driver.  Communicate with the SM to acquire the P_Key and
>     Michael> then use that to perform Arp / ND.  Strange to require a
>     Michael> command since this gets a bit cumbersome when there are
>     Michael> many nodes in the fabric.
> 
> That is a nice idea in theory but it falls down in practice.  
> First, the IPoIB driver is often loaded during the boot 
> process, and init scripts may want to configure IPoIB 
> interfaces before the SM has discovered the local node.  
> Also, a node may have many P_Keys assigned, only a few of 
> which are used for IP traffic.  Administrators don't like to 
> have to deal with 50+ network devices.


I tend to agree with Mike that a configuration here may be redundant 

IPoIB interfaces can pop up like USB devices when the P_Key table is
field (in a default DHCP client mode)
With one Interface per P_Key by default (unless configured otherwise)
Anyway a system/interface cannot be used if the Port is not initialized
by the SM so it is not critical to bring it up sooner

If the interface is configured with an IP + Mask + .. It should be saves
(associated with the right P_Key like in the VLAN case)
The next time the system will boot, when the P_Key is discovered it try
to match it with existing config if non found it is configured to use
DHCP

I don't see many partitions (if any) that don't have an IPoIB associated
with them
Any way user may also configure IPoIB to skip partitions i.e. not bring
up an IPoIB interface for a certain partition 
(it will also happen automatically, in case you don't want to have an
IPoIB interface for a certain partition, just choose one that doesn't
have any DHCP server listening on as well, it will result in a
non-active interface on that P_Key since no one will configure it)

The benefits are clear:
Zero configuration and P&P
No need for manual user intervention for the default (DHCP) case 
Limit configuration errors (e.g. conflicting parameters)
Works better in a utility computing type of environment or large
stateless clusters which are the sweet spot for IB

Yaron