On Thursday, 01/22/2009 at 05:05 EST, "Harder, Pieter"
<[email protected]> wrote:
> You just lost me. LACP is on the trunk side of the VSWITCH. I am talking

> bonding on the port side of it. What exactly did you think of doing that
was
> solved by LACP?

Talk about a confusing conversation!

For those who left their scorecard at home today, LACP (Link Aggregation
Control Protocol) support in the VSWITCH is directed only at the physical
switch.  The guest-facing side of the VSWITCH does not support LACP.
(Let's avoid terms like "port side" and "trunk side".  When a guest is
using a virtual trunk, which side is the "trunk side"?)  LACP is the thing
that lets the host and switch coordinate traffic.

The only use of LACP that I've seen/heard about so far is for better error
toleration and recovery, better physical OSA management (dynamically
delete from group so you can put on microcode fixes, then re-add), and to
satisfy Management demand to "Stop wasting OSAs!  Why aren't both LEDs
flickering?!?  I'm not paying for LEDs that don't flicker!"  (FYI, IEEE
802.3ad spec lists 9 benefits of which increased bandwidth is only one.)

While you can have multiple vNICs on an aggregating VSWITCH, there's
nothing that will spray/deal queued frames across the vNICs since they
each have a unique MAC address.  But even if it did, you're doomed if the
buffer fill rate is higher than the consumption rate.  All you've done is
delay slightly the point at which all guest buffers are full.

Alan Altmark
z/VM Development
IBM Endicott

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