Cable Modem Primetime Slowdown - Myth or Reality?

The Llama King asks: "SBC (SWBell, Pacbell, etc.) is whacking away at Time Warner cable in our area, running DSL ads that make fun of prime-time cable modem slowdown. And Time Warner-Houston/RoadRunner does seem to be having a problem in the past month with nasty ping times between 8 pm - midnight Central time (traces submitted to internal RoadRunner news groups show the problem appears to be a pair of routers at the gateway to one of several backbones). While this problem is recent, it begs the question - are prime-time cable slowdowns real or a myth? Can a well-configured cable modem network avoid the congestion SBC pokes fun at in their commercials, or is it inevitable? What are Slashdot users seeing?"

I don't notice much slowdown

[vrt3]

My ISP is Telenet/Pandora in Belgium. In primetime, net use seems to be slower compared to less busy times, but the bottle neck doesn't seem to be on the ISP's cable network. Downloads from the ISP's mirrors are always fast, even in primetime.

Comcast/Planetcable -- Mercersburg, PA

[TufelKinder]

FWIW, I have not noticed slow "times" of the day in my area. However, Planetcable was forced to stop accepting subscribers until Comcast had upgraded their infrastructure to support the additional traffic, so this could be an atypical situation.

In general though, I have noticed a substantial variation in the quality of service from day to day, and month to month. Some days or weeks at a time it's fine, and other times it's horrible (high ping/high packet loss) for months.

Little bit of each

[clark625]

Ameritech is running the same types of ads here in Ohio as well. What the ads don't say clearly is that you need to live next door to the central office if you want the maximum DSL bandwidth. For me, where I live nearly 3 miles from the CO, the best they claim for me is 128Mbps either direction. All that for $50 a month.

By contrast, the cable can handle huge amounts of bandwidth down and I'm pretty much assured a minimum of 128Kbps up. But, the cable bandwidth is shared among all my neighbors. It's important to realize, though, that all my neighbors aren't sharing 1.5Mbps down and 128Kbps up. It's more like 10.5Mbps down and 512Kpbs up. Business customers can get a dedicated line that gives them the entire bandwidth. Heck, Road Runner Columbus [rrcol.com] even offers what they call a "direct connection" to the internet at up to 45Mbps symetric.

Back to this topic, have I ever experienced a slow-down during peak hours? Nope. But I now live in a subdivision that I am certain isn't abusing the cable network. When I lived near Ohio State, however, I did find at times I was limited in bandwidth and Time Warner had troubles with their DHCP server getting overloaded. The worst data rate I ever was able to receive was somewhere near 500Kbps. That's many times better than most DSL lines. And at $45 a month (new price "adjustment"), it's easily the better choice.

Re:Little bit of each

[AtrN]

the best they claim for me is 128Mbps either direction. All that for $50 a month

Damm, there's that "post from the future" bug again.

Re:Little bit of each

[legoboy]

All that I know about cable slowdown is that at 6pm PDT last night, I was downloading a 40MB file at in excess of 700 kB/s (according to Netscape). I pay $40.00 Canadian each month for this.

DSL is the same price, with a optimal maximum download speed of 768 kb/s. If I lose 3/4 of my cable performance, I'm still downloading way the hell faster than I would be on DSL. Additionally, with Shaw, the upload speed isn't capped (or rather, if it is, it's capped at a high enough level not to inconvenience any who aren't trying to be an Akamai peer.

I do think that I'll be forgetting DSL, when my downloads with cable peak out at double the speed of a dedicated T1. Obviously the bandwidth restrictions aren't at my ISP's end.

Re:Little bit of each

[geekoid]

Actually, you need to be closer then 3 mile to there repeater(they don't call it a repeater, but I forget its name)
I lived outside DSL's range, then one day, I saw the telco guys working about 50 feet from my door. After they had been there all day, I went and asked them if I should expecet a loss of telephone service(I knew I wouldn't but I was fishing)
they told me there were installing hardware to get DSL to the people who where currently out of range.
The next day I ordered DSL, 768/128 39.95. that was sweet.
then the telco decided they could provide the service for more money and get all the customers simple by jacking the line rate up for all the DSL providers.
After which I went to cable. I was the only one on my node, and I was getting 9Mbp. I miss that.

Re:Little bit of each

[Prior Restraint]

Ameritech is running the same types of ads here in Ohio as well.

Since Ameritech is owned by SBC, they're probably the exact same ads.

Charter In Auburn, MA

[haplo21112]

Charter Cable here in Auburn Worcester Area has "ever changing pings". For sometime now I have never been able to get anything even resembling a consistent ping time or download rate. Somedays the connection flys the next its barely faster than a 56K modem. During the whole "Code Red" thing it was just sad, the light on my linksys router, for activity was just solid didn't blink at all. I called them several times and asked them to look into the reasons why their network was in such a state. I telecomute into my compant from time to time so this period was esspecially annoying. I am still monitoring several Code Red, Nimda, and related virus'es a day knowcking on the door. I guess in the end the moral of this story, the network only as good as those who run it, and even less good if they never listen to the users of the network who try to tell them whats wrong.

@Home in Canada

[alman]

One pipe for all people paying.
yeah it does get slow, really slow.
there are times in the summer where having a dial up will be faster (I'm not joking!)
over all it's not that bad though

Not slow, but bursty...

[nneul]

I'm on a pretty idle cable node on a fiber loop with 512/512 service. Unfortunately, the connection appears very bursty, and actually never seems to get the rated speed. It appears that it transfers in a very quick burst for about 1/10th of a second, and then just sleeps/idles for about a second, then another burst. Problem is - overall, those delays really add up.

TWC/RR Orlando FL

[ers81239]

I have Road Runner in Orlando, and have monitored it pretty consistently (that is because it was always going down, and I had to be able to tell them when it was going down. Turned out to be some borked signal amplifier down the street).

Like most people here my ping times varied greatly. My set of test pings to local ISPs and to internic.net would go from 15ms to 300ms and back in a matter of 10 minutes. I actually see the worst performance during the business day.

The techs said that this big AT+T building next door was using RR for business purposes so maybe that was the cause.

I've never had 'poor' performance, I've always been happy with it. I've certainly never seen it slow down to near-dialup speeds like some have mentioned.

Cable slowdown....not entire myth but not all true

[Chanc_Gorkon]

Well, mine stays the same most of the time and lately it's been better. Yes, during the evenings it's slower, but not that slow. My slowdown is usually caused by the DNS being a bit on the slow side. Once the address is resolved, it pops up fairly quick. That's most of it. A few times I can definitely say it was excess traffic in our neighborhood. New Years Eve was one where the network slowed to a crawl if it worked at all and this weekend, after the attacks happened, it seemed to be VERY slow and not fast until sometime Monday Morning. I get INCESSANT hits on the firewall since Code Red and Nimda. For a while, my activity light was lit solid for DAYS on end. I used to get 100-200 hits on the firewall per hour. Now, I still get too many hits and they are all coming from local IP's, but only about 10-20 an hour. I get VERY few hits on the firewall from IP's outside of road runner. It's all local traffic. Some of it seems to be pings from the provider as well. I think most of the hits seem to be Road Runner scanning the network looking for unpatched IIS boxes or unauthorized servers (it is in the agreement(no servers)folks and they have every right to do it no matter how stupid we think it is....).

I agree with the other person about the DSL ads and the fact that you have to be practically ontop of the CO to get the high speeds. I am only 1 mile away and I couldn't even get 128 K a while ago. Now I can get it, but it's all slower then and more expensive then my cable modem. Lately, Road Runner has been REAL attentavie to outages even. I remember one time I was out for a whole day and I didn't even call techsup and I had a credit on my bill the next month. That's cool. They KNOW when these outages happen. You should not have to call and bitch to get a credit. I do know that they are starting to be more attentive to customers, although their network issue page is usually out of date. At least they are updating the equipment gradually. I used to have a legacy modem, but after one REAL long outage, they gave me a new DOCSIS modem. Plus I think that some cable providers are loosening the IP restricitons and not hassling people who want to share their connection with other machines. Cable Modems are getting better. They have to or they are going to really loose it when the local phone companies get a clue about DSL and reduce price and make it competitive and make it so you don't have to live over the CO to get a high speed connection.

It's real

[Trak]

I've got Adelphia Powerlink here in South Florida. I run an infinite ping and a looped traceroute process from my home machine to my counter-strike server at the office. The mid-day 80ms xport times jump to a whopping 400-1200ms at 6:30pm on the nose every weeknight and stay there until well after midnight.

Not bandwidth, DNS

[mckwant]

The problem I've seen in our local area (Austin, TX) is that their DNS seems to drop every so often. They're not long outages, just 5 minutes or so, but when you're expecting a 24/7 connection, it's a little surprising.

I, personally, have not noticed a slowdown during peak hours, and I'm in a neighborhood where it should matter.

If you're trying to decide on whether to go DSL or not, consider that RR (at least around me) won't do static IP (not even one). There are some vague workarounds that'll let me ID and use my IP for something that talks to the outside world, but that's not really the route I want to take.

Re:Not bandwidth, DNS

[Cheeze]

dns shouldn't be an issue, since that is a variable that you should be able to change. most operating systems allow you to specify dns settings, even if you get your ip information by DHCP. check your documentation on your operating system to find out how.

note: you can use any DNS server. the closer ones are usually faster, but if they are unstable, change them

Re:Not bandwidth, DNS

[toast0]

i wouldn't use just any dns server...

#1, even if it works now, they may update their configuration to exclude people who are not users of their network from running queries on the internet at large with their servers. Its not that hard to configure it that way, and its an easy way to reduce network usage.

#2, if there is any problem with that server, it may be difficult to resolve

an easier/more reliable step to take is make your own caching server that will go ahead and hit the root-servers for pointers if your isp's aren't working

Re:Not bandwidth, DNS

[mckwant]

Yes, I COULD use a static DNS server, but it's not something I care to deal with or apply a DIY approach to.

Just as an FYI, RR doesn't use static DNS, but dynamic on their side, so maybe that's part of it. Personally, you start talking networking, and I'm already asleep.

I'll second that

[gruntvald]

I get great service, blazing quick from RR in Orange County, SOCAL. I measured it as being 30 times faster than our office T1 at one point, which, even with the 50 or so users, was an eye opener. However, their DNS servers are down regularly. They switched from NT DNS to W2K DNS and just can't seem to keep 'em running. The only other issue I've had is whenever I get a TV outlet installed, the cable guy jacks up my connection. Remember folks - it's 1 Y only from the pole - 1 connection goes to your cable modem, (or router if you have a business package like me), the other to EVERY OTHER TV IN YOUR HOUSE. The cable guy always gets here, sees the single Y and turns it into a triple, and down we go....

Any internet technology can be oversubscribed

[hamjudo]

With DSL only the very first hop is dedicated to a single customer. Once your bits get to the central office, they share a pipe with other customers. If that pipe has less bandwidth than the sum total bandwidth of the individual customers, that pipe is oversubscribed. Likewise for all of the upstream pipes.

With a cable modem, the only difference is that the very first hop might also be oversubscribed.

A cable has a lot of bandwidth. That bandwidth is divided up into channels (on an NTSC analog system, channels are all 6Mhz wide, your channels may vary). Each internet cable box is assigned a channel (or set of channels, if channels only come in one size). Your next door neighbor's cable box might use a different channel, and thus not be in the same neighborhood.

Logically, a cable system is a tree, or set of trees, with the root of each tree at the cable company office, and the customers are the leaves. The thicker branches may run on fiber, they support more channels, and therefore more neighborhoods.

A wee tiny cable company may have a single T1 (1.5Mbps) line connecting to the greater internet, a large company might have several OC48 (2.5Gbps). The same is true for DSL providers.

ISP's either charge premium rates or they oversubscribe the service, or both. I don't see a primetime slowdown on my $180/month, 384K DSL line.

Re:Any internet technology can be oversubscribed

[Baloo Ursidae]

Almost right, but...
Your first hop is always your headend. From the headend it switches off the cable system onto a larger pipe than cable. The prime-time slowdown is no different in nature than DSL.

DSL, from my experiance, suffers much larger slowdowns due to chronic oversubscription and bandwidth caps to the customer. Unlike DSL, the cable company can slap a headend in pretty much anywhere they can get permission to slap in a box the size of a shrubbery, and can put more than one node in the same physical connection if they've got fat pipes (larger than cable) going to the outlying headends.

The first hop is always just one customer.

Not for me.

[NetJunkie]

I have RoadRunner in Raleigh, NC and never see slowdowns. I always get the full 2Mb/sec when downloading with DAP. It's been this way for a long time since I first got it. They seem to do a very good job of subnetting people up.

But, all bandwidth can be oversold, not just cable. My friend had DSL in Texas and the telco oversold the local bandwidth and his pings went to 500ms just to his first hop at the ISP. At some point ALL bandwidth is shared, it just happens that DSL users have a piece of wire to the CO...but at the CO it all comes together, just like a loop on a cable modem.\

Marketing hype....

It's true

[mjoconnor81]

because you are sharing a databus with your neighbor and everyone else who happens to be on your local loop, congestion can lead to slowdowns. With a dsl, the local loop is dedicated, but you can still have congestion from the local loop through the rest of the network.

You can run into congestion no matter what type of access you use, the disadvantage of a cable inet access is you can also have congestion problems on the local loop.

Why doesn't this discussion show up on home page?

[_Neurotic]

I wouldn't even know it existed if not for it showing up for me in metamod. And no, "the Internet" is not blocked in my preferences.

Re:Why doesn't this discussion show up on home pag

[unitron]

Go into your preferences and enable the "Ask Slashdot" box. A lot of interesting "Ask Slashdot" stories never make it to the main page.

Cable sweetness in older neighborhood

[rjamestaylor]

I live in an old neighborhood - Lakewood, CA - and have ATT Broadband (was Mediaone). At the office, in Irvine, CA, we have PacHell DSL.

I work from home as much as possible to enjoy a stable, fast Internet connection. At the office, we experience service outages every day (when you're ssh'ed into a remote server, you notice EVERY interruption, dammit) and frequent unexplainable slowdowns (can't blame Napster!).

DSL doesn't share between the CO and the home/office, but it does share SOMEWHERE. Today, for example, I downloaded StarOffice for Windows and Linux from Sun. The first Windows download was corrupted (?) and I had to download it again. Then, stupid me, I realized I downloaded 5.2, so I wen back and downloaded 6.0beta of Windows and Linux. These are ~100 each. So, in less than two hours, while working in the foreground, I downloaded over 400MB from Sun. My sustained transfer rate was over 180Kbps. I would never, ever, attempt such a thing during working hours at the office (on the DSL line). Ever. Downloading Windows patches is painfull enough, believe me.

Ping times are incredible on my cable modem. When I had home DSL I was happy to be able to ping 'nearby' IP addresses in 75ms. Same sites for cable are 10ms usually.

At home I run a linux server and have set up an emergency backup of our production and demo sites incase our dedi-hosted sites go down. I would never have thought of trying that with the office PacBell DSL.

I was a subscriber of Metricom's Ricochet until it died. I used my Ricochet modem at the office, rather than subject myself to the horrors of PacBell DSL.

It could be that my older neighboors don't stress the cable system as a younger demographic would. That could explain why I have NEVER detected a "slow time". And I'm on my connection constantly (ask my poor wife!).

Given the choice, I'll choose cable everytime.

UPDATE - Cable modem slowdown

[The Llama King]

Last night (10/9), RoadRunner-Houston apparently did some tweaking/up-beefing to the router that was causing pain. About mid-evening, the effect was sudden & dramatic - ping to it went from the high 200s to the 20s-50s. Online gaming was suddenly possible, where it had not been before. We'll see if it holds...

ATT cable is great, just don't use email

[magarity]

I have ATT cable in Colorado and as long as you don't use their flaky email service, it's great. Sure, in the evenings it slows down a little, but never so much that I'd complain it was slow.

It's 10AM local time on a weekday, where's a pair of concurrent downloads during what is probably "fast time" for home cable and "slow time" for business DSL...

Over ATT cable:
ftp> mget patch-2.4.11.gz
local: patch-2.4.11.gz remote: patch-2.4.11.gz
200 PORT command successful.
150 Opening BINARY mode data connection for patch-2.4.11.gz (941101 bytes).
226 Transfer complete.
941101 bytes received in 2.21 secs (4.2e+02 Kbytes/sec)
ftp>

And at the same time on another machine (at another business) connected to the best local DSL provider on a 512/512 connection (ain't ssh from work great?!):
ftp> mget patch-2.4.11.gz
local: patch-2.4.11.gz remote: patch-2.4.11.gz
200 PORT command successful.
150 Opening BINARY mode data connection for patch-2.4.11.gz (941101 bytes).
226 Transfer complete.
941101 bytes received in 23 secs (40 Kbytes/sec)
ftp>

I can re-run these tonight around 7pm local time and post the evening cable "busy time" results. Not completely scientific, but it should be revealing.

I notice it here (Cambridge, MA)

[The Pim]

I log into my home machine (via ssh) from work, mostly to read my mail with mutt. I usually have no problems during the day, but in the evening, the latency often gets really bad--like a second or five to show the next message. Occasionally, the connection dies. But it's intermittant.

I don't know much about how to diagnose the problem, but my net connection at work is fine, and I don't notice anything funny when I list connections with netstat or watch total traffic with /proc/net/dev. So I assume it's just overloading of my provider's network.

My situation may be anomalous because I care more about outbound traffic, which is more limited with cable. I've never noticed any problem at home--but then again, I don't usually use my computer at home in the evening, and when I do it's web browsing rather than interactive remote logins.

My service is AT&T Broadband (formerly MediaOne) in 02140.

The reality of the situation is...

[Jennifer Ever]

... $50/mo isn't going to get you a 24/7 2MB/s connection to the internet.

Sigifigant speed differences

[masteroveride]

A while back a few friends and I had setup a hotline server that was on one of my friend's cablevision cable connection. Even from my earthlink DSL, download speeds would go from 50k/s in the late afternoon, to 25k/s in the early evening. And at 10:00 pm EST every night the speed skyrocked from 25k/s to approx 125k/s. Even now i don't bother to download anything from and IP of 24.***.***.*** untill later at night.

Rogers@Home

[grimmy]

When I was liveing in Toronto, On (Canada) the only time it ever got slow was when the DNS servers chocked.

Some of that might have been my modem's fault though as I had to power cycle about once a week. But the cable lines in my area wheren't the best, and there was a filter on the line before I ordered basic cable so that could be it too.

My DSL experience on the other hand is a joke. I called up Sympatico (Bell Canada) and ordered their "high speed" service. Setup kit showed up about a week later via Fedex, and they shipped me *two* install kits. So I unpacked one, set it up, ad installed their software (pppoe). And it didn't work. I call tech support after an hour of playing with it, and I get a french rep that *barely* spoke english and ended up hanging up on me.

I ended up useing my dialup account and calling longdistance to my old isp and downloaded winpoet or something like that and got it working.

My average download speed was roughly 40-60kps (bytes), cable it was alway around 200kps. And my average ping when i fired up TFC or Q3 was NEVER below 100-110, cable 20-35 =P

And between 5pm and 1am DSL was always noticeably slower, ohh and did I forget to mention that the CO was 6 blocks away? and it was a brand new phoneline? Ohh and cable, I was on the router of a city that was 20-25 minutes away =P

So I guess I've had the total opposite experience of most people. Ohhh and Rogers@home was 3mbit down/320kbps up. Sympatico is like 967kbps up/128kbps down.

I doubt it has anything to do with primetime

[GoatPigSheep]

the internet in general is slower when lots of people are logged on, and 8-12pm is a popular time... I remember when I used dial-up, I used to get the most busy signals then and the worst connections.

Slowdowns in Wichita, KS

[jayhawk88]

I don't have any evidence to back this up, but it seems to me that my cable modem does take a hit during "peak hours". Between 5-10, I generally get around 80-100 ping on most of my favorite TFC servers. On some occasions when I take a day off...errr, stay home sick, I can usually pull 50-70 ping on the same servers. The servers are usually always full, too, so I don't think it's just a busy server.

Of course, lately most of the slowdowns I've seen have been cause by Code Red, etc. I swear, that little activity light never stops blinking.

The problem isn't slowdown for me

[drinkypoo]

The problem is outages. I have excite@home via mediacom, and lately it's been blowing up a lot.

With a DOCSIS cable modem setup, each user has their own downstream frequency range. This range can be used to provide each user (5,000 - 20,000 of which can be on a single MC16 line card, four line cards to a cisco 7246 uBR, I don't know about other manufacturers) with 45 Mbps of downstream bandwidth. Since no one is doing video on demand with them yet, most people are limited to 1.5 or 2.5 Mbps.

Now, the upstream is limited to something like 11 Mbps per upstream channel; When I worked for Cisco they had MC11 line cards with one upstream and one downstream, and MC16 line cards with six upstreams and one downstream. So between 5 and 20 thousand subscribers could be sharing between 11 and 66 Mbps of (theoretical) upstream bandwidth. That could be a bit crowded, but upstream isn't where the emphasis is, anyway.

So what this tells us is that with modern equipment, the problem is not the number of people on your block using the service, though certainly a great deal of legacy cable modem hardware exists. Those markets which just got CM access in the last year or so will probably almost all be DOCSIS installations. The problem is the pipe, and any provider can suffer that, broadband or no. As other posters have noted, that's a problem of oversubscription.