On 3/23/06, Mark Butler <[EMAIL PROTECTED]> wrote: > I understand that timed intervals between individual packets is not > realistic in general. What I have in mind is a fixed granularity > transmission timer, where packets are assigned to buckets, and > transmitted one bucket per timer expiration.
Why is it not realistic? > > >From a protocol design point of view, the main question is which is > more expensive, rate based timer expiration, or generating ACKs at a > high enough rate to self clock. With 1 Gb/sec reliable transport > protocol, every other packet ACK generation, and Ethernet MTU size > packets, ACKs are generated every 30 usec on average. With Van Jacobsen > style pre-queuing a large percentage of them are wasted overhead, > because a long series of them accumulate in the prequeue before the > receiving thread is activated. Various others look at doing things like certain number of ACKs per RTT rather than per packet or fixed number of packets. For both using interpacket intervals and differing ACK strategies have a look at TFRC: http://www.icir.org/tfrc/ This seems to work quite well for me in all the testing I've done although I have only tested up to 100 Mbits - but this tested OK on 500 MHz machines so newer machines should handle faster rates well. Ian -- Ian McDonald Web: http://wand.net.nz/~iam4 Blog: http://imcdnzl.blogspot.com WAND Network Research Group Department of Computer Science University of Waikato New Zealand - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
