RE: IPv4 Directed Broadcast

On Tue, 3 Dec 2002, Rosenstock, Hal wrote:

> Hi Vivek,
>
> That takes care of net directed and all subnet directed broadcast. Is the
> same true of
> subnet directed broadcast ? Are these also on the same broadcast group with
> the
> hosts filtering them if they do not match the subnet ? I presume that is how
> it needs to
> work based on your statement that all IP broadcasts use the broadcast group.

Yes, that is correct. The underlying reason is that any IP broadcast,
whether limited or directed (net, subnet, or all-subnets) are broadcast
on the local link, and therefore use the link-layer broadcast address.

Vivek

>
> Thanks.
>
> -- Hal
>
> -----Original Message-----
> From: Vivek Kashyap [mailto:vivk <at> us.ibm.com]
> Sent: Tuesday, December 03, 2002 1:24 PM
> To: Rosenstock, Hal
> Cc: ipoverib <at> ietf.org; ipoverib-admin <at> ietf.org
> Subject: Re: [Ipoverib] IPv4 Directed Broadcast
>
>
>
>
>
>
> Hal,
>
> The broadcast-group is a link-layer broadcast address (the equivalent of
> all 1's ethernet address). The broadcast group is used for any kind of IP
> broadcast. The rest of the mapping is for IP  multicast addresses only.
>
> For example:
>       10.255.255.255 or 255.255.255.255 are both broadcasts and should map
> to the Broadcast group -> FF12:401B:<P_Key>::255.255.255.255
>
>       But:
>       Multicast address 225.0.0.1 will map to the GID derived as per the
> rules in the draft t -> FF12:401B:<P_Key>::1.0.0.1
>
> Vivek
> --
> Vivek Kashyap
> Linux Technology Center, IBM
> vivk <at> us.ibm.com
> kashyapv <at> us.ibm.com
> Ph: 503 578 3422 T/L: 775 3422
>
>
>
>
>
>                       "Rosenstock, Hal"
>
>                       <hal <at> pacelinesyst        To:       ipoverib <at> ietf.org
>
>                       ems.com>                 cc:
>
>                       Sent by:                 Subject:  [Ipoverib] IPv4
> Directed Broadcast
>                       ipoverib-admin <at> ie
>
>                       tf.org
>
>
>
>
>
>                       12/03/2002 05:28
>
>                       AM
>
>
>
>
>
>
>
>
> > Hi,
> >
> > In IPv4, there are two forms of directed broadcast (net directed and
> > subnet directed). In draft-ietf-ipoib-link-multicast-02.txt, section 7 on
> > The IPoIB Broadcast Group states "The broadcast group for IPv4 will serve
> > to provide a broadcast service for protocol like ARP to use.." Is it
> > correct to assume that this also includes (IPv4) directed broadcasts as
> > well (rather than forming additional IB multicast groups out of the low
> 28
> > bits of the IP address for this purpose) ? If so, should this be added to
> > clarify the spec ?
> >
> > Thanks.
> >
> > -- Hal
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>

__

Vivek Kashyap
Linux Technology Center, IBM