[evla-sw-discuss] Multicast addresses

[James Robnett]

   A couple of comments on Hichem's email below (thanks
for the email btw Hichem).

1) Using different port numbers instead of different
mcast groups is fine if listeners always want all the
data and the ports are merely used to differentiate it.

     If a user just wants 'archive' or just wants
'alert', 'observe', 'CMP/IG' or 'CMP/MW' that's not a great idea.

    Delivery of the packets to a subscriber is a function
of mcast group so somebody who just wants alert will get the
other 4 and then throw them away.  If all 5 were on
their own mcast group a system could subscribe to just
those that it wanted.

    I don't know enough about what's desired to say if
it's right/wrong.

2) Telcal uses a semi-inappropriate mcast group. Only
the low order 23 bits are used to make the MAC addr
so 224.0.0.1 and 225.0.0.1 map to the same MAC addr
and so does 230.0.0.1 (anything of the form x.0.0.1
or x.128.0.1 results in the same MAC as 224.0.0.1).

   All machines on the same network (VLAN) as the transmitter
will see that traffic,  machines on remote VLANS
will only see it if they registered.  IE, igloo transmits
and checker, scred, miranda etc all see it since they're
on that network.  On remote networks only those hosts
that register for it (eg mchost) see it.

   I'd suggest avoiding any group that starts with 224 or
has a '0' or 128 in the 2nd octet) in it, hard to go wrong
that way.

3) I suspect changing the MIB's would be a royal pain so I'd
make them the 'base' and suggest changing the others to conform.
239 = NM, 192 = EVLA, so all EVLA mcast groups would be 239.192.x.y
then we just twiddle those last two octets avoiding '0'.

    If changing any of them are a royal pain so be
it, since it 'appears' to be working.

James

Hichem Ben Frej wrote:
> Hi James,
> To my knowledge, these are the multicast addresses used for the EVLA 
> including the CMP and the executor.
> 
> Thanks,
> 
> EVLA
> ====
> archive: 239.192.0.1 port 20010
> alert: 239.192.0.1 port 20011
> observe: 239.192.0.1 port 20013
> mib_log: 239.192.2.1 port 20000
> 
> CMP
> ===
> IG: 239.192.0.1 port 20016
> MW: 239.192.0.1 port 20015
> 
> 
> IDCAF
> 231.0.1.1 port 20020, 20021, 20022, 20023
> 
> Telcal:
> 230.0.0.1 port 30002, 30012, 30022, 30042
>