Here's a few downstream/upstream numbers and ratios: ADSL2+: 24/1.5 = 16:1 (sans Annex.M) DOCSIS 1.1: 38/9 = 4.2:1 (best case up and downstream modulations and carrier widths) BPON: 622/155 = 4:1 GPON: 2488/1244 = 2:1 Only the first is non-shared, so that even though the ratio is poor, a person can fill their upstream pipe up without impacting their neighbors. It's an interesting question to ask how much engineering decisions have led to the point where we are today with bandwidth-throttling products, or if that would have happened in an entirely symmetrical environment. DOCSIS 2.0 adds support for higher levels of modulation on the upstream, plus wider bandwidth (http://i.cmpnet.com/commsdesign/csd/2002/jun02/imedia-fig1.gif), but still not enough to compensate for the higher downstreams possible with channel bonding in DOCSIS 3.0. Frank -----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of Jack Bates Sent: Monday, October 22, 2007 12:35 PM To: Bora Akyol Cc: Sean Donelan; nanog@merit.edu Subject: Re: Can P2P applications learn to play fair on networks? Bora Akyol wrote:
1) Legal Liability due to the content being swapped. This is not a technical matter IMHO.
Instead of sending an icmp host unreachable, they are closing the connection via spoofing. I think it's kinder than just dropping the packets all together.
2) The breakdown of network engineering assumptions that are made when network operators are designing networks.
I think network operators that are using boxes like the Sandvine box are doing this due to (2). This is because P2P traffic hits them where it hurts, aka the pocketbook. I am sure there are some altruistic network operators out there, but I would be sincerely surprised if anyone else was concerned about "fairness"
As has been pointed out a few times, there are issues with CMTS systems, including maximum upstream bandwidth allotted versus maximum downstream bandwidth. I agree that there is an engineering problem, but it is not on the part of network operators. DSL fits in it's own little world, but until VDSL2 was designed, there were hard caps set to down speed versus up speed. This has been how many last mile systems were designed, even in shared bandwidth mediums. More downstream capacity will be needed than upstream. As traffic patterns have changed, the equipment and the standards it is built upon have become antiquated. As a tactical response, many companies do not support the operation of servers for last mile, which has been defined to include p2p seeding. This is their right, and it allows them to protect the precious upstream bandwidth until technology can adapt to a high capacity upstream as well as downstream for the last mile. Currently I show an average 2.5:1-4:1 ratio at each of my pops. Luckily, I run a DSL network. I waste a lot of upstream bandwidth on my backbone. Most downstream/upstream ratios I see on last mile standards and equipment derived from such standards isn't even close to 4:1. I'd expect such ratio's if I filtered out the p2p traffic on my network. If I ran a shared bandwidth last mile system, I'd definitely be filtering unless my overall customer base was small enough to not care about maximums on the CMTS. Fixed downstream/upstream ratios must die in all standards and implementations. It seems a few newer CMTS are moving that direction (though I note one I quickly found mentions it's flexible ratio as beyond DOCSIS 3.0 features which implies the standard is still fixed ratio), but I suspect it will be years before networks can adapt. Jack Bates