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Are Cable ISPs Sharing Fairly?

Members of the ISP-Tech list discuss the difference between dialup and cable network architectures. In either case, the real source of network problems is oversubscription.

[January 2, 2002]

On the ISP-Tech list in December, TH queried,

"Over the last three days, my cable access has been slowing down. Tech support had me clear out my Temporary Internet Files, and my speeds went right back up. If my browser accesses my Temporary Internet Files to load pages faster, why were they having the reverse effect? Is this a problem with my computer, or with the cable company?"

JE claimed that these are simply the usual frustrations that many customers have with cable access:

"Ah, the nature of cable Internet! You're experiencing the inherent flaws in the over-subscription of a network not meant for data transport. Slap about 250 users on a 10BaseT hub in a local LAN environment, get about 50 percent of those users sharing files at the same time, and that's cable. What's going on is the result of an over-subscribed, poorly managed cable op."

[ed. note: 10BaseT = 10 Mbps before Ethernet overhead, divided by 250 users = 40 Kbps before Ethernet overhead, slower than good dialup. Note that in this scenario, a 100 Mbps hub would give c. 400 Kbps to each user, which would be fine.]

Others disagreed, saying that most cable access should work just fine:

[MS countered] "On my cable connection, I always have better speeds than our DS3 here at the office."

[JM added] "In the six months that I've had cable access, I've had a positive experience. Yes, it's a shared connection, so performance varies depending on the overall load on the system, but I usually get faster download speeds than I do over our office T1. Still, I'm sure some broadband providers are better than others, and some do badly over-subscribe their capacity."

Still others noted that the Internet cache can easily slow a system down:

[BG observed] "If your Internet cache was full, your system was probably spending more time on the read/writes than on the actual connection."

[LC explained] "When you have 10 or 20 MB of cache directory scattered all over a badly fragmented disk, the browser can spend a lot of time futzing around with the browser cache. Some caching is good and welcome, but while heavy caching on a fragmented disk is still good for traffic reduction, it can be bad for the user experience."

[MS added] "And a box can get fragmented in a few days."

Others recommended turning off the Internet cache altogether:

[JB offered] "If you are on a fast connection, like cable or DSL, I don't see the need for caching. It doesn't make that much of a difference."

[JW agreed] "I turned off the caching in my browser, and was amazed at the speed difference. I'm going to recommend this to a few of my customers to see if they see a speed difference as well. If so, I'll advise all my customers to turn off caching."

—End