[HFC] pooling modems in layer2

Toney Mareo halflife4 at gmx.com
Tue Aug 12 14:23:38 UTC 2014


Hello

I think it's kind of an isp secret but I would be curious how do people distribute modems to pools before they would even reach the actual IP network so on layer2:

http://dl.packetstormsecurity.net/papers/evaluation/docsis/Service_Distribution.jpg


For this I would like to get some clarification because I do not work in the telco industry. As I can figure out of the docsis, cablelabs documents. The CMTS device is connected to the coax segments through fiber. Therefore one could say that the "modem facing" side is a fiber optic interface but it's not 1000 Base-FX, not a regular Ethernet over fiber. It sends signals through a broad range of frequencies.

So what I would like to accomplish to provide a different pool of dhcp servers, which provides different config file, tod server, router, dns etc. infos to the modems but to do all this in Layer2. 

I don't have hands on experience with CMTS-es but I would think that they are able to pool clients by MACs and able to send eg 500 clients to DHCP server1 and the other 1500 to DHCP server2 before they would even get an IP, so I talking of pure layer2 here!

Let's say if the CMTS device does not support this, what are the other options for routing layer2 traffic coming out of the CMTS? If I would know more about the device I would say that put a linuxbox after it (on the ISP facing nic) and mark the packets going out with arptables/ebtables then send them out of different nics to different dhcp servers. 

Any suggestions are welcome.


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