Subject: mbone, atm, dec alpha's...

From: Markus Buchhorn <[email-masked]>
Date: Tue, 21 May 1996 15:51:25 +1000

G'day All

I've now successfully run most of the various mbone tools in unicast
mode on our ATM connected Alpha's (DU 3.2c). Now I'm getting cocky
and want to run multicast sessions :-). The problems are that (i) it's been
too long since I've last worked with this, and (ii) back then I wasn't totally
sure what I was doing anyway....<sigh>.... 

The scenario:

We have here 8 Alpha's, hooked up via ATM (DEC GIGASwitch/ATM)
using TCP/IP over ATM. One of them (dhpc01) also has an Ethernet interface to
connect everybody to the rest of the campus/world. The others have a 
default route to the ATM interface of dhpc01, and a 'net' route for
the group over the ATM interface of the localhost:

default          dhpc01             UG          2    11897  lis0
localhost        localhost          UH          6     8790  lo0
dhpcnet          dhpc02             U          28   965335  lis0

At this stage I want to create a session (with sdr), have it broadcast to the
other machines, and other sites connect as per usual in a multipoint
session.

Now - the switch don't do multicast, and I'm not clear that the interface
does either (although it does allow the 'allmulti' flag to be set). My
impression was that for the time being I would have to run an mrouted
on each host with a tunnel back to one machine, and it could have a tunnel
to the outside world as needed.

Q1: mrouted only runs when it has two vifs - is it redundant (and safe) to
   have duplication of paths by creating tunnels between each pair of
   machines ? (i.e. dhpc02 <-> dhpc03 and dhpc04, 3->2&4, 4->2&3). It 
   seems wrong, but I can't seem to get around it.... or can I create a
   fake tunnel ? (or set the metric very high ?)

For now I'm using two machines to start with, and after installing the ipm35
bundle for decalphas_osf I fired up mrouted (each had a spare tunnel to
another machine) and all appeared Ok - mrinfo showed the tunnel up between
the two working machines and down to the third:

dhpc02# ./mrinfo
127.0.0.1 (localhost) [version 3.8,prune,genid,mtrace]:
  150.203.192.12 -> 150.203.192.13 (dhpc03.anu.edu.au) [1/1/tunnel/leaf]
  150.203.192.12 -> 150.203.192.14 (dhpc04.anu.edu.au) [1/1/tunnel/down/leaf]

Then I tried sdr (and sd) and get IP_ADD_MEMBERSHIP errors, Network unreachable
and Can't Assign Requested Address. I tested it with 
(i) enabling the 'allmulti' switch on lis0 (the ATM interface) and
(ii) trying to disable the lis0 interface for mrouted (as per some suggestions
   on the list)

The latter stopped mrouted from starting:

'phyint lis0 disable' -> Invalid Interface name lis0
'phyint <ip-addr> disable' -> <ip-addr> is not a configured interface

Q2: What am I doing wrong in all of the above ?

In all of my twiddling I may have missed a particular combination of all
of the above, so I can't rule that out yet (I'm going to do myself
a table of options next..)

Q3: I don't have an mrouted on dhpc01 (yet - it's a server) - does the fact
that the default routes on dhpc02/03/04 point to it cause a problem here ?
(since packets from 2 going to 3 will try to go via 1 ?) Then again, isn't
that what a tunnel is all about (IP-in-IP) ?

I've scanned my mailing list archives, and the notes and man pages. I may
have missed something (spot the obvious disclaimer attempt :-) ).
Any help *greatly* appreciated ! Ultimately we will have several clusters like
this scattered around the country on an experimental long-haul broadband 
network, and I'd really like to be able to set up something like an mbone 
environment for it....

Thanks for any/all help/comments

Cheers,
	Markus

Markus Buchhorn,  Parallel Computing Research Facility   |  Ph: +61 6 2492930
email = [email-masked],  snail = CISR, I Block, | Fax: +61 6 2490747
Australian National University, Canberra 0200, Australia | Mobile: 017 970715

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From: Ajay Kachrani USG <[email-masked]>
Date: Tue, 21 May 1996 11:13:16 -0500 (EDT)

IP Multicast is not supported by DEC Alpha ATM yet.

--Ajay Kachrani