nanog mailing list archives
Re: Extreme congestion (was Re: inter-domain link recovery)
From: "Alexander Harrowell" <a.harrowell () gmail com>
Date: Tue, 21 Aug 2007 18:24:49 +0100
This is what I eventually upshot.. http://www.telco2.net/blog/2007/08/variable_speed_limits_for_the.html On 8/19/07, Mikael Abrahamsson <swmike () swm pp se> wrote:
On Sun, 19 Aug 2007, Perry Lorier wrote:Many networking stacks have a "TCP_INFO" ioctl that can be used to queryformore accurate statistics on how the TCP connection is fairing (number of retransmits, TCP's current estimate of the RTT (and jitter), etc). I've always pondered if bittorrent clients made use of this to better choosewhichconnections to prefer and which ones to avoid. I'm unfortunately unsureifwindows has anything similar.Well, by design bittorrent will try to get everything as fast as possible from all peers, so any TCP session giving good performance (often low packet loss and low latency) will thus end up transmitting a lot of the data in the torrent, so by design bittorrent is kind of localised, at least in the sense that it will utilize fast peers more than slower ones and these are normally closer to you.One problem with having clients only getting told about clients that arenearto them is that the network starts forming "cliques". Each clique worksas aseparate network and you can end up with silly things like one cliquebeingfull of seeders, and another clique not even having any seeders at all. Obviously this means that a tracker has to send a handful of addressesofclients outside the "clique" network that the current client belongs to.The idea we pitched was that of the 50 addresses that the tracker returns to the client, 25 (if possible) should be from the same ASN as the client itself, or a nearby ASN (by some definition). If there are a lot of peers (more than 50) the tracker will return a random set of clients, we wanted this to be not random but 25 of them should be by network proximity (by some definition).You want to make hosts talk to people that are close to you, you want tomakesure that hosts don't form cliques, and you want something that atracker canvery quickly figure out from information that is easily available topeoplewho run trackers. My thought here was to sort all the IP addresses, andsendthe next 'n' IP addresses after the client IP as well as some randomones.If we assume that IP's are generally allocated in contiguous groups thenthismeans that clients should be generally at least told about peoplenearby, andhopefully that these hosts aren't too far apart (at least likely to bewithina LIR or RIR). This should be able to be done in O(log n) which shouldbefairly efficient.Yeah, we discussed that the list of IPs should be sorted (doing insertion sort) in the data structures in the tracker already, so what you're saying is one way of defining proximity that as you're saying, would probably be quite efficient. -- Mikael Abrahamsson email: swmike () swm pp se
Current thread:
- Re: Extreme congestion (was Re: inter-domain link recovery), (continued)
- Re: Extreme congestion (was Re: inter-domain link recovery) Hex Star (Aug 16)
- Re: Extreme congestion (was Re: inter-domain link recovery) Stephen Wilcox (Aug 17)
- Re: Extreme congestion (was Re: inter-domain link recovery) Patrick W. Gilmore (Aug 17)
- RE: Extreme congestion (was Re: inter-domain link recovery) Mikael Abrahamsson (Aug 16)
- Re: Extreme congestion (was Re: inter-domain link recovery) Deepak Jain (Aug 16)
- Re: Extreme congestion (was Re: inter-domain link recovery) Mikael Abrahamsson (Aug 16)
- Re: Extreme congestion (was Re: inter-domain link recovery) Fred Baker (Aug 16)
- Re: Extreme congestion (was Re: inter-domain link recovery) Mikael Abrahamsson (Aug 16)
- Re: Extreme congestion (was Re: inter-domain link recovery) Perry Lorier (Aug 18)
- Re: Extreme congestion (was Re: inter-domain link recovery) Mikael Abrahamsson (Aug 19)
- Re: Extreme congestion (was Re: inter-domain link recovery) Alexander Harrowell (Aug 21)
- Re: Extreme congestion (was Re: inter-domain link recovery) Mikael Abrahamsson (Aug 21)
- Re: Extreme congestion (was Re: inter-domain link recovery) Joe Provo (Aug 19)
- RE: Extreme congestion (was Re: inter-domain link recovery) michael.dillon (Aug 16)
- Re: Extreme congestion (was Re: inter-domain link recovery) Adrian Chadd (Aug 16)
- Re: Extreme congestion (was Re: inter-domain link recovery) Alexander Harrowell (Aug 17)
- Re: Extreme congestion (was Re: inter-domain link recovery) Stephen Wilcox (Aug 15)
- Re: Extreme congestion (was Re: inter-domain link recovery) ChiloƩ Temuco (Aug 15)
- RE: Extreme congestion (was Re: inter-domain link recovery) Rod Beck (Aug 15)
- Message not available
- Re: Extreme congestion (was Re: inter-domain link recovery) Stephen Wilcox (Aug 16)