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Date: Fri, 29 Jun 2007 11:48:37 +0200 (CEST) From: Pierre Capillon <pierrecap@...oo.fr> To: netdev@...r.kernel.org Subject: Getting hopcount and dupacks from TCP CA module Hello, I'm a french IT engineering student and as part of my internship, I'm writing a congestion avoidance module based on research by my tutor. It aims at better efficiency and throughput on mobile adhoc networks. Basically, it is a sender-side modification that differentiates between losses due to network congestion or link failure, in which case I would need to get the new route properties for the current tcp socket. Is there a simple and generic way of knowing the route length (hopcount) from a TCP CA module, once RTO has occured? Currently, the paper states I should know the exact new route length to recompute the congestion window and RTO values. I guess I need to get that information from the routing layers, but is it event possible from the module? Or is it simpler to rework the algorithm to have the congestion window based on hop difference (using received TTL values from the remote end)? Either way, I would appreciate hints/pointers to structures and/or mechanics I would not have properly understood in congestion avoidance modules (especially how to get down to the received IP header for received TTL values or to the routing protocols). Regarding dupacks, after a full week of studying the code and another week of implementing most of the principles described in the said paper, I would like some confirmation : it seems like the field tp->sacked_out is accounting for them in a SACKless connection (in tcp_fastretrans_alert()). Can I without a doubt rely on it to adjust TCP's behavior? If so, can I check is the state is TCP_CA_Disorder and then the value of sacked_out in order to adjust my behavior once 3 duplicate acks have been received, or is there a better way to do it? I'm sorry if this sounds like a dumb question, but I want to make sure, as I'm no expert. Thanks a lot. Pierre Capillon ___________________________________________________________________________ Découvrez une nouvelle façon d'obtenir des réponses à toutes vos questions ! Profitez des connaissances, des opinions et des expériences des internautes sur Yahoo! Questions/Réponses http://fr.answers.yahoo.com - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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