>
Hi there,
This is not a "broadcast", but also, a kind of ping.
I have an entry at http://bugzilla.xensource.com/bugzilla/
show_bug.cgi?id=1140 , and maybe some of you could be interested.
It follows:
------------------------------------
Hi,
I made some tests about ethernet padding ( an expected
behavior from
ethernet 10/100 on-wire, that needs at least 60 bytes of data to be
able to
CRC. NIC chipset has the job of fullfill the packet if it is smaller
than this
- also called "padding" ) and I notice a behavior that is not
expected (at
least for me).
>>> Ethernet Padding Sender / Receiver Matrix <<<
\RECEIVER | Dom0_vif |FullV_DomU_2|ParaV_DomU_2|SMP_ParaV_DomU_2
SENDER/
Dom0_vif#######| No (OK) | Yes (OK) | No (NOK) | No (NOK)
FullV_DomU#####| No (NOK) | Yes (OK) | No (NOK) | No (NOK)
ParaV_DomU####| No (NOK) | Yes (OK) | No (NOK) | No (NOK)
SMP_ParaV_DomU| No (NOK) | Yes (OK) | No (NOK) | No (NOK)
My setup is a Centos 5.1 (2.6.18-53.1.4.el5xen) / Xen (3.0.3
or 3.1, as I hear) in a
bridge network configuration.
The results shows that only FullVirtualization do padding,
and only when
receives a packet (not when send it).
You could ask "why padding if you dont have a physical
transport?". If
you are playing with some L2 protocol (like AoE), this behavior do
impact.
A direct related problem: it''s not possible to export AoE
disks from
Dom0 and other Paravirtualized guests (AoE blade server verifies if
the packet
has a minimal size - 60 bytes) to any local VM. I do not known if
another
layer2 protocols has the same problem, but I think that is a expected
feature
that a virtual NIC works as a physical one.
Best Regards
Marcelo Messa
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