Re: When does Linux drop UDP packets?

Hi,

* david@xxxxxxx <david@xxxxxxx> [2009-06-05 12:15:27-0700]:

On Fri, 5 Jun 2009, Alexander Clouter wrote:

* david@xxxxxxx <david@xxxxxxx> [2009-06-04 16:19:56-0700]:

On Thu, 4 Jun 2009, Alexander Clouter wrote:

It's dead easy to transmit and receive multicast traffic, broadcasting
network traffic is so 1980's :)

there is only a difference between multicast and broadcast traffic if you
are spanning subnets.

Well yes and no. Broadcast traffic is *always* handled by the kernel as
only the kernel can tell if it is interested in it or not. With
multicast the NIC is configured to only pass particular
Ethernet multicast packets up to the kernel.

By using broadcast traffic the load (okay, hardly a big problem
now-a-days) hits *all* the workstations on the subnet, with multicast,
only those interested in the traffic receive it.

true, but only for some NICs, and even those tend to have a fairly small
number of slots for the filters. past these limits the OS handles it all
just like broadcasts.

I *think* only the early ones have a naff non-hashing based to filter
multicast flows, could be wrong though.

Either way, as a packet pusher by day, I dream of the venduh's
discovering that multicast can be used for device discovery rather than
expecting everything to be on the same subnet :-/

In this day and age, using broadcast to do a job is just plain lazy and
braindead.

Cheers

--
Alexander Clouter
.sigmonster says: Misuse may cause suffocation.
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