Broadband expert John Navas of The Navas Group shares his top tips for keeping your connection up and running.

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Your broadband Internet connection (cable modem, DSL, and so on) is running poorly. You're experiencing frustrating delays and erratic performance. You tuned your computer, but that didn't help. Your provider's support hasn't solved your problem. ("Try rebooting your computer. Try again later.") Here's how to pin down the issue and get your connection back on track.

Preparation

  • The basics


    • Nodes
      Internet connections between you and a remote host (e.g. www.techtv.com) normally pass through a series of intermediate points ("nodes") where routers (special-purpose routing computers) send them on the proper link to the next node. Problems can result when routers or links get overloaded, or when routing information (the Internet "map") gets messed up, as sometimes happens.
    • Packets
      Data is transmitted over the Internet in packets (chunks of data). The TCP/IP Internet protocol is designed to detect and automatically correct packet transmission problems (if possible).

  • Two important things you can measure


    • Latency
      Latency is simply the round-trip time it takes for a packet to reach a remote point (node) and a response to get back to you, typically measured in thousandths of a second (milliseconds, or simply "ms"). When everything is working properly, the latency of consecutive measurements will be consistent and in a normal range (40 ms to 200 ms for cable modem or DSL, higher or lower for other forms or broadband). Erratic latency is a sign of trouble.
    • Packet loss
      When everything is working properly, each data packet should reach its destination. However, when there are problems with links or routers (e.g. overload), packets may be lost. It takes considerable time to detect and resend a lost packet, so performance drops dramatically with even a relatively small amount of packet loss. As a rule of thumb, packet loss should be less than 1 percent. Packet loss of more than 5 percent is serious.

  • Basic measurement tools (software that's probably already on your computer)

    • Traceroute
      Traces the path between you and the remote host as a series of nodes (and the links between them). Typically displays three latency measurements for each node and looks up node names (if available). Under Windows it's called "tracert," as in the examples below. If you use Linux, substitute "traceroute" for "tracert." Here's an example of a clean, fast DSL connection:
      tracert www.TechTV.com
      Tracing route to www.techtv.com [64.95.116.134] over a maximum of 30 hops:

      1 21 ms 17 ms 15 ms gateway.example.net
      2 18 ms 18 ms 21 ms internal.example.net
      3 19 ms 20 ms 17 ms border.example.net
      4 21 ms 19 ms 21 ms 500.Serial2-11.GW3.SFO4.ALTER.NET
      5 19 ms 20 ms 18 ms 129.ATM2-0.XR1.SFO4.ALTER.NET
      6 19 ms 20 ms 19 ms 191.ATM6-0.GW4.SFO4.ALTER.NET
      7 25 ms 25 ms 26 ms internap-gw.customer.alter.net
      8 24 ms 24 ms 26 ms border5.ge3-1-bbnet1.sfo.pnap.net
      9 26 ms 26 ms 26 ms techtv-1.border5.sfo.pnap.net
      10 28 ms 24 ms 25 ms 64.95.116.134
      Trace complete.

    • PING
      Sends a special packet designed to get a response back from a particular remote node, much like the echo of a sonar ping used to detect objects underwater. It's usually possible to send several (or even continuous) PINGs in succession, and the latency of each PING is commonly displayed. Since PING can be used in certain forms of Internet attacks, some nodes deliberately ignore PINGs as a security measure, so a complete failure to respond to PING is not necessarily bad. Note the consistent latency and lack of packet loss in this example of a clean, fast DSL connection (where "-n 10" is used to send 10 PINGs):
      ping -n 10 www.TechTV.com
      Pinging www.TechTV.com [64.95.116.134] with 32 bytes of data:
      Reply from 64.95.116.134: bytes=32 time=26 ms TTL=47
      Reply from 64.95.116.134: bytes=32 time=23 ms TTL=47
      Reply from 64.95.116.134: bytes=32 time=22 ms TTL=47
      Reply from 64.95.116.134: bytes=32 time=22 ms TTL=47
      Reply from 64.95.116.134: bytes=32 time=23 ms TTL=47
      Reply from 64.95.116.134: bytes=32 time=22 ms TTL=47
      Reply from 64.95.116.134: bytes=32 time=24 ms TTL=47
      Reply from 64.95.116.134: bytes=32 time=25 ms TTL=47
      Reply from 64.95.116.134: bytes=32 time=26 ms TTL=47
      Reply from 64.95.116.134: bytes=32 time=22 ms TTL=47
      PING statistics for 64.95.116.134:
      Packets: Sent = 10, Received = 10, Lost = 0 (0 percent loss),
      Approximate round-trip times in milliseconds:
      Minimum = 22 ms, Maximum = 26 ms, Average = 23 ms


  • More advanced tools


    • Sam Spade for Windows (freeware)
      Very good and comprehensive network tool, albeit somewhat eclectic.
    • VisualRoute (trialware $40)
      Greatly improved PING traceroute that can plot the geographic path of an Internet connection on a map. Here's a live online demo.
    • Ping Plotter (freeware or shareware $15)
      Excellent PING-traceroute tool for monitoring and displaying Internet performance over time.


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