[Xorp-users] IGMP and Multicast question

[admin galerie]

Le 5 févr. 08, à 19:07, Pavlin Radoslavov a écrit :

>>>> We are trying to make the following work, as a test platform for 
>>>> now, but
>>> then
>>>> it will be needed in a real case operation :
>>>>
>>>> mcast source-------Linux smcroute---------LinuxXORP-------mcast 
>>>> receiver
>>>>           ^                             ^        ^       ^
>>>>           |                             |        |       |
>>>>       192.168.1.1                      eth0     eth1     192.168.3.4
>>>>                                   192.168.2.3  192.168.3.3
>>>
>>> Linux smcroute and LinuxXorp are different systems, right?
>> Yes, indeed. We used smcroute only for the test, because it is quick 
>> to
>> configure.
>>>
>>> Question: why don't you enable IGMP on the eth0 interface?
>> In my understanding, activating an interface for igmp in Xorp means 
>> "listen for
>> potential receivers on this interface". And I know we have receivers 
>> only on
>> eth1. Am I wrong ? By the way, in a first configuration I in fact had 
>> configured
>> eth0 for igmp also, with no difference in behaviour.
>>>
>>> I don't see how you can make this work, AFAIK Xorp cannot act as an
>>> IGMP proxy (RFC4605?) and if you are working with two routers you 
>>> need
>>> to have PIM in both sides (i.e. in the Linux smcroute and LinuxXorp).
>>>
>>> Actually, you are not simulating properly the Juniper case by just
>>> adding a Linux system with smcroute. You need to have a PIM-enabled
>>> daemon in that side, to simulate multicast routing amongst routers.
>> See below my comments about a "two PIM routers" configuration.
>>
>>>> Our understanding of what should occur is probably wrong, but we 
>>>> thought
>>> that
>>>> the IGMP report received from the MC receiver should be enough for 
>>>> the XORP
>>>> router to have the necessary information to be able to forward the 
>>>> stream
>>>> received on eth0 to eth1. What is not correct in this assumption ?
>>>
>>> No, from my limited understanding (I'm not a multicast guru, but hey)
>>> the Xorp router has to "find" which multicast routers are available
>>> (through PIM) and then, when it sees, the IGMP repo from a MC 
>>> receiver
>>> on its side it will "subscribe" to the multicast group with its main
>>> multicast router. In your environment there is only one multicast
>>> router (i.e. Xorp) so it does not know who to contact to get the 
>>> group
>>>  230.1.1.1 requested by the client.
>>>
>>> That being said, I'm not sure if it will work if you add eth0 to the
>>> IGMP definition, as smcroute will just forward (if properly
>>> configured) the multicast traffic from the server "as is". Did you 
>>> try
>>> that?
>> Yes, we tried and saw no difference. We also tried to have a Xorp Pim 
>> daemon
>> running instead of  smcroute, and it did work, the receiver had the 
>> MC flow
>> directed to him (it ?), but in the real world case, there will not be 
>> a PIM
>> router on the Juniper (AFAIK as of today).
>
> Juniper has PIM-SM so is there any reason not to configure/use it?
> If Juniper won't be running PIM how are you going to get that box
> forward the multicast traffic? Are you planning to have it running
> IGMP proxy?
> If this is the case then XORP needs to run PIM-SM with little
> special configuration. I can provide that info to you once I
> know what are you going to do on the Juniper side.
>
The Juniper side is not our responsibility, so we can't make choices 
for the people who are going to configure it. Between the Juniper and 
our Xorp router, there is a satellite network, and cypher/decypher 
devices, where it is necessary to configure security associations for 
each flow you intend to transmit (unicast and multicast). That is the 
main reason why we try not to have PIM signalling between the Juniper 
and us. I asked the person in charge of the Juniper how it was going to 
forward the multicast traffic, and he answered there was a simple 
static configuration, the kind "all MC traffic from interface A shall 
be directed to interface B". Does it make sense ?

To resolve my problem, which seems to be a RFC4605 (thanks Javier) test 
case, couldn't I start two instances of Xorp on my Xorp router ?

Thanks again for helping me (I confess I'm kind of a newbie in routing 
magic...)

best regards,

Vincent