Hello
I have a major problem regarding implementing IP Multicast in an ADSL network. The diagram of our network is attached. In every Access Network , there is only IP DSLAMs which are connected via Metro ethernet links ( L2 links) to the main site. So there is no Router or Layer 3 Link to the main site. In the main site there is an Aggregator router which is an PPPOE server which terminates subscriber's PPPOE sessions. All the Access networks and subscribers are just connected to one Aggregator and they use that one as PPPOE server. It is an Cisco 3845 Router. Then the Aggregator is connected to Core network and behind the Core network is an Streaming server which streams in Multicast. IP Multicast Routing is configured in Spars-Dense mode in all routers in Core network and also the Aggregator and it is working properly. So the sucscribers are able to join the multicast stream and the very last router in the path toward the subscribers( which is the Aggregator) does the Multicast replications.
There are two problems we faced and need your help:
1- Since all the subscribers from different Access Network use the same Aggregator in the central site as PPPOE Server, all the connection are terminated on that router. The goal is to use the uplink bandwidth of the Access networks to the central site more efficiently and if e.g 20 subscribers watches the same channel, it just consumes as the amount of one channel due to doing IP Multicat.Now the problem is that when for example 2 subscribers of the same Access Network (in the same POP site) connect to the same stream, the amount of bandwidth used between the central site and the Access network is double. It happens because the aggregator activates IGMP on every virtual-access lines for every PPPOE subscribers who wants to joint the stream. So it can not recognized these two subscribers are from the same Access network. Therefore, the result is that although it is doing Multicast, it does not save the bandwidth because it activates IGMP group on every subscriber's virtual access line for his PPPOE connection. So is there any solution to this problem? Something came to my mind that we need to implement a separate aggregator for every Access network which means that we have to place a router for every access site and it will be expensive for us. But I think in that case every local aggregator can do IP Multicat routing and it saves the bandwidth definately. But do you have a better solution that may solve our problem using the same topology?
2- Another problem is that when the subscriber's CPE are configured in bridge mode and subscribers set-up a PPPOE connection on their PCs, they are able to join the multicast stream properly. But when they put their CPE in router mode and have their ADSL modems as PPPOE client, they are not able to join the Multicast stream. i.e the ADSL modem is doing NAT and routing and it connects to PPPOE server using username/password credentials. I also tried a feature in ADSL modems called "IGMP support" when I wanted to create the WAN settings. But it did not work. I am not sure but I think that we need "IGMP Proxy" feature on subscriber's CPE. Do you have any idea what might be the source of this problem and how I can solve it? is it due to lack of IGMP Proxy on these CPEs or is it because of something else?
Thank you guys
Regards,
Masih
