I was tickled to see that expiring packets based on 'time in queue' was already a key design feature of the IPN, http://www.science20.com/interwebometry/lessons_nasa_can_learn_internet-84861 and the idea was suggested also independently in saturday's CACM article's comments... http://queue.acm.org/detail.cfm?id=2071893 Making decisions based on time in queue (TiQ), rather than length of queue, would seem to be a win, especially for wireless, but also for that does 'soft' traffic shaping with HTB-like qdiscs and sub qdiscs. Anything that is not running at GigE plus speeds would benefit. ... since basically what's been happening with bufferbloat is a too early implementation of the IPN, with detours between here and the moon! ... and so far I haven't seen any major theoretical holes in with TiQ, except for deciding as to how long is too long as to consider a packet as 'expired', (which can be measured in ms or 10s of ms), and having reasonably monotonic time. I just wish I (or someone) could come up with a way to implement it in Linux without multiple layer violations. skb->queuestamp has a nice ring to it, but when I look at this portion of the stack I freely admit quivering in ignorance and fear. I did a bit of work on a set of timestamping fifos, but realized that it was the entire queue's duration from entrance to exit (through multiple scheduling qdiscs) was what needed to be measured, and the drop/no drop decision needs to be made as late as possible - and preferably, the queue being pulled from needs the next packet pulled forward so as to inform the receiver that congestion is happening... And Eric dumazet also produced a preliminary patch a few weeks back that tied timestamping to before the head of a queue, but that tried to use a reserved field in the skb that appears from points A to Z is not guaranteed to be preserved. Thoughts? -- Dave Täht SKYPE: davetaht US Tel: 1-239-829-5608 FR Tel: 0638645374 http://www.bufferbloat.net -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
