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Networking The Internet

Ask Slashdot: What Is an Acceptable Broadband Latency? 396

holmedog writes "A simple question with a lot of answers (I hope). I recently had issues with my DSL broadband at home, and after a month of no resolution, I was told 300ms latency (to their test servers) was the acceptable range for Centurylink 10.0Mbps. This got a shocked reaction out of me to say the least. I would think anything over 125ms to be in the unacceptable range. So, I have come to you to ask: What do you consider to be acceptable broadband latency and why?"
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Ask Slashdot: What Is an Acceptable Broadband Latency?

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  • by Anonymous Coward on Tuesday March 06, 2012 @01:31PM (#39263109)

    ...of the broadband wars. All consumers really seem to care about is faster download speeds, so networks offer it - by munging up their network so much that latency is measured in seconds. With the death of the network engineer, people just aren't educated enough to realize that part of the whole broadband experience is getting your packets sent and received fast, not just your GET or retrieve request getting all the data it asked for quickly. If you have to wait more than a second or two for your requests to even get there, then most people are gonna give up and try somewhere else.

  • by DoofusOfDeath ( 636671 ) on Tuesday March 06, 2012 @01:33PM (#39263139)

    We can't really tell you what's "acceptable". That ultimately depends on what you're using it for.

    Maybe the right question is, are you getting a worse ratio-vs.-price situation than is found in most markets in your country?

    Or are you asking whether or not the provided is in breach of the law because they're offering something so bad that their advertising is deceptive?

  • by Bookwyrm ( 3535 ) on Tuesday March 06, 2012 @01:34PM (#39263177)

    Just where exactly are these 'test servers' in relation to you? What, exactly, was this 'test'? This seems a bit of a worthless test. It's entirely possible your DSL has less than 100 ms latency, but the delay is on the server end or the links in between. This is too vague a scenario to comment on.

    My feelings about 'acceptable' latency depend on how much I am paying for it, at what bandwidth, with what level of SLA, and for what purpose.

  • by Above ( 100351 ) on Tuesday March 06, 2012 @01:37PM (#39263239)

    When you say the word "latency" most tech-savvy folks think about the propagation speed of the technology (e.g. electricity in copper, or light in fiber), and thus assume it's basically proportional to distance.

    However, latency comes from other things as well. Serialization delay adds latency, and the lower the symbol speed the more it adds. Multiaccess media adds latency while waiting to transit. Multiplexing anything adds a small amount of latency looking for a time slot.

    The biggest culprit? Bufferbloat. This is a term that has been coined to describe the fact that many networking devices have entirely too much buffer. In the best case someone has sized the buffer for the max line rate that device may see (perhaps 25Mbps for your DSL modem, when your link is only 10Mbps), in the worst some misguided engineer thought "more == better" when figuring out how much to buffer, or just didn't care. There are a number of efforts to try and fix this poor situation, http://www.bufferbloat.net/ is the place to start. Basically buffers add latency. A small amount of buffering increases throughput, but beyond that it does nothing but increase latency and generally make the user experience crappy. When the link is full you need to drop packets _quickly_, because that's the signal to TCP to back off. Packet loss is a _good_ thing on a full link.

    Try running ICSI's Netalyzr (http://netalyzr.icsi.berkeley.edu/) which will attempt to estimate your uplink and downlink buffering. If you have a "router" in front of your DSL modem it may have some tuning, or "QoS rate shaping" that will help. If it's a device provided by your service provider you may not have access to the settings, and it may simply be configured wrong. With some vendors asking for a different model of device may help, with others, you may be screwed.

    The technologies involved should deliver 20ms latencies if properly configured. You should absolutely expect that, but getting them to acknowledge a problem may take latencies over 50ms. If your service provider thinks 300ms is normal, you need to escalate or move to a different provider.

  • by localman57 ( 1340533 ) on Tuesday March 06, 2012 @01:40PM (#39263327)
    How about a car analogy? All people care about is Horsepower. It's a single number that advertisers can sell. Transmissions, rear ends, torque curves, who cares?
  • Re:Latency (Score:5, Insightful)

    by Joce640k ( 829181 ) on Tuesday March 06, 2012 @01:42PM (#39263359) Homepage

    PS: Talking of hops, tracert will show you how many hops are between you and their "test servers". Finding that out would be a good starting point.

  • Filter (Score:4, Insightful)

    by SuperTechnoNerd ( 964528 ) on Tuesday March 06, 2012 @02:21PM (#39264113)
    I had a client with a similar issue. Turned out there was a phone in the basement he had forgotten about and did not have a filter. Installed the filter and he got between 60 - 100ms to his default gateway where before it was 250+ ms
  • Re:Latency (Score:4, Insightful)

    by JWSmythe ( 446288 ) <jwsmythe@jws[ ]he.com ['myt' in gap]> on Tuesday March 06, 2012 @03:05PM (#39264905) Homepage Journal

        You shouldn't have posted AC, you're actually right on the money.

        300ms could be that he has the line saturated with bittorrent traffic, or malware that he doesn't even know is there. It could be that his wireless connection is compromised, and the neighbor kid is downloading porn day and night. 300ms isn't acceptable, but likely isn't the provider's fault.

        Why, oh why, don't more people monitor their bandwidth? Maybe I'm a statistical whore, but I always have some sort of bandwidth graphing up.

Never worry about theory as long as the machinery does what it's supposed to do. -- R. A. Heinlein