Interesting talk - thank you!<div><br></div><div>-Matt R</div><div><br><br><div class="gmail_quote">On Sun, Jan 15, 2012 at 7:40 AM, JD <span dir="ltr"><<a href="mailto:jdp@algoloma.com">jdp@algoloma.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">A Cisco DOCSIS guy, Biran Wilson, gives talks at the hacker-cons periodically.<br>
Find the OuterZ0ne videos if you're interested in more detailed, organized<br>
information. DOCSIS3 lets channels be mixed for digital cable video and data. It<br>
also allows channel bonding.<br>
<br>
See the Brian Wilson talk - Docsis Coolness<br>
2010: <a href="http://www.archive.org/details/Outerz0ne2010Videos" target="_blank">http://www.archive.org/details/Outerz0ne2010Videos</a><br>
<br>
I had both residential and business comcast service through 2 different lines to<br>
the house. It was weird calling for business ISP support during multi-hour<br>
outages using VoIP connected to the residential line not seeing any issues at all.<br>
<br>
I love it when my neighbors talk about how DSL doesn't share bandwidth so it is<br>
better. That means they aren't on my cable line. The fact that DSL is usually<br>
3x slower ALL-THE-TIME for the same price doesn't matter, it is still "better."<br>
ADSL2+ is changing the performance difference a little, but still has other issues.<br>
<br>
There is enough hate for telecom and cable companies to go around. They have<br>
most of us by the balls.<br>
<br>
<br>
<br>
On 01/14/2012 10:17 PM, Matt Rutherford wrote:<br>
> Trying not to run on to much but here is an overview of how DOCSIS does dynamic<br>
> bandwidth. I'll leave out the more detailed guts of it. An in-depth of this<br>
> subject is way too OT here.<br>
><br>
> DOCSIS has a feature that allows for burst speed provisioning within a specified<br>
> range when there is bandwidth availability on the server. This can be applied to<br>
> a set amount of a specific transaction, ie: 5MB, 10MB, 20MB, etc. This provides<br>
> the nice bump in initial download/buffer speed on large videos (see Youtube,<br>
> Netflix, etc) and also is quite noticeable on speed test sites since they are<br>
> file-transfer speed based. Also looks great for marketing and advertising in<br>
> comparison to the speeds offered on DSL. This is all handled by the CMTS.<br>
><br>
> Typically the burst speed will be set to the around the same level as your<br>
> provisioned speed, though this is not always true. IE: a 22mbps connection will<br>
> burst speeds up to 44mbps (down) for a pre-determined amount of upwards or<br>
> downwards transfer. Since cable speeds are non-synchronous, you may have a 5mbps<br>
> upstream with bursts up to 10mbps. This cannot be relied on however, hence the<br>
> careful use of 'up to (X)mbps' in advertising.<br>
><br>
> Peak usage hours for residential areas for cable internet bandwidth run<br>
> 5pm-midnight as Kirsa said, so I'd add a +1 to the congestion theory. There are<br>
> other causes as well, but tech support should be checking for those symptoms<br>
> anytime you call in (SNR, bad RX/TX, and high levels of error correction to<br>
> packets from the modem).<br>
><br>
> During heavy usage if there is saturation of the bandwidth availability to below<br>
> a specified threshold, protocols kick in to limit users to speeds lower than<br>
> their 'provisioned' default. This is done dynamically since each CMTS has<br>
> multiple RF cards separated into upstream and downstream. You may have a<br>
> non-saturated upstream but a saturated or congested downstream as far as<br>
> bandwidth goes - we rarely saw upstream problems except for military barracks,<br>
> college towns, and other edge cases. There are other layers of bandwidth<br>
> management and bottlenecks that impact speeds which can exist at the node or<br>
> network level, but outside of RF issues the most typical and noticeable change<br>
> in speeds comes from this type of congestion.<br>
><br>
> -Matt R<br>
><br>
><br>
> On Sat, Jan 14, 2012 at 8:48 PM, Jim Kinney <<a href="mailto:jim.kinney@gmail.com">jim.kinney@gmail.com</a><br>
> <mailto:<a href="mailto:jim.kinney@gmail.com">jim.kinney@gmail.com</a>>> wrote:<br>
><br>
> All ISPs know the speedtest sites. Comcast is known to privide priority routing.<br>
><br>
> On Jan 14, 2012 7:53 PM, "Drifter" <<a href="mailto:drifter@oppositelock.org">drifter@oppositelock.org</a><br>
> <mailto:<a href="mailto:drifter@oppositelock.org">drifter@oppositelock.org</a>>> wrote:<br>
><br>
> On Saturday, January 14, 2012 05:36:53 pm Kirsa wrote:<br>
> > I would not be surprised if you experienced a similar speed issue next<br>
> > Friday though... On almost any residential cable node Friday 5-12pm is<br>
> > peak time and has the most utilization of the entire week. So that you<br>
> > were down to 4mbit/s on Friday evening and 2mbit/s by Friday night<br>
> > sounds suspiciously like congestion to me, despite the faulty<br>
> > equipment.<br>
> [Rest trimmed for brevity.]<br>
><br>
> I had the same speed issues at 9 am Saturday morning. Snail-slow download<br>
> speeds continued all day Saturday until I replaced the defective hub.<br>
> Then: BINGO! full speed returned. In fact, a speed about 19:45 Saturday<br>
> (Speakeasy's test) returned the rather unbelievable download speed of<br>
> 40.59 mbs! The upload speed was only 4.16. Obviously some sort of burst<br>
> speed. Does Comcast have some way to know when I access a speed test site<br>
> and goose the speed for a few seconds?<br>
><br>
> Sean<br>
> ______________<br>
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</blockquote></div><br></div>