[crossbow-discuss] ?: shared vs. exclusive network stacks

[Steffen Weiberle]

Erik Nordmark wrote On 09/11/06 17:12,:
> Steffen Weiberle wrote:
> 
>> With crossbow's network virtualization, as I understand it each VNIC 
>> gets its own stack. Is it possible to have multiple VNICs share a 
>> stack? I'm not sure what benefit there would be of having multiple 
>> VNICs share a stack, except that there will be less stacks. If a 
>> single zone has multiple VNICs assigned, across multiple NICs, it may 
>> be sufficient to only have one stack.
> 
> It's a bit different.
> Each VNIC gets some network resources; a separate squeue.

OK, separate from the squeue per CPU without crossbow, as I understand it.

> 
> But the relationship between (V)NICs and stack/IP instances is a bit 
> different.
> When a zone is configured to be an exclusive IP zone, it is assigned one 
> or more datalink names. Those datalinks could be NICs (e.g., bge0) VLANs 
> (e.g., bge33000) or VNICs.

So the 'exclusive' keyword' assigns a separate stack?

> Thus each zone can have multiple VNICs; this might make sense when the 
> VNICs are on different NICs.
> 
> Note that the VLAN part doesn't work with bge at the moment. We need to 
> have a /dev/bge33000 to do that.
> 
>> Similarly, will all non-VNIC interfaces share the single default stack?
> 
> No. See above.

If the 'exclusive' keyword is never used, is there only one stack? So, 
thinking about why I'm even asking, there are several reasons.

Different MTUs (but that should be per NIC, unless newer NICs allow it 
per 'partition'.

Routing (and where IP makes decisions)

ndd settings (will separate stacks now allow different default 
settings for things like TCP parameters and default buffer sizes?)

Some of my questions and confusion comes from Sunay's presentation 
referred to in section 9 of his Aug 24 blog entry, especially page 12.
http://blogs.sun.com/sunay

While IP QoS will be a nice feature, I am trying to understand how 
crossbow addresses a lot of the thing we have dealt with over the 
years where configuring the stack for a specific application need 
tended to affect the whole system. And, of course, how it addresses 
the routing issues with zones.

Thanks,
Steffen

> 
>     Erik