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Re: DirecPC Protocols
This is AFAIK _not_ what DirectPC does, but have you taken a look at RFC3077 and the UDLR draft http://www.ietf.org/internet-drafts/draft-ietf-udlr-experiments-00.txt ? This covers the complications of doing IP over very assymetric links as part of the IP, including both multicast and TCP issues. Regards Marshall Eubanks Crist J. Clark wrote:
I've been looking for some technical descriptions on how DirecPC works from a TCP/IP point of view. Does anyone out there have some references? I have not been able to find anything too detailed, and from what I have been told, they are not too forthcoming when contacted directly. I know the rough outline. The customer sends out traffic over a normal PPP link (since the customer has no uplink to the DirecPC satellite) to a separate ISP. The traffic has a spoofed source address set to some DirecPC server at their ground site(s). Thus, the third-party target's response goes to DirecPC who send it over their satellite link back to the customer using the wide satellite pipe instead of the narrow PPP pipe. But I'm curious about the details. First things first, anyone know how the DirecPC link is established? That is, how the customer tells DirecPC what his IP address is? I assume this must all happen over the PPP-link, or at least the two-way PPP-link is used for bootstrapping. Now once things are going, what kind of predictive ACKing games does DirecPC play? The reason I am curious is that I'm trying to figure out what kinds of things ISPs, or any Internet access provider (say the user is dialing into a corporate RAS), can do to break or accomodate DirecPC. The obvious things that come to mind are egress filtering and NAT. In addition to any technical information that can help me figure this out for myself, experience others have had with these same problems would also be helpful. Thanks a lot for any help.
-- T.M. Eubanks Multicast Technologies, Inc 10301 Democracy Lane, Suite 410 Fairfax, Virginia 22030 Phone : 703-293-9624 Fax : 703-293-9609 e-mail : firstname.lastname@example.org http://www.multicasttech.com Test your network for multicast : http://www.multicasttech.com/mt/ Status of Multicast on the Web : http://www.multicasttech.com/status/index.html