Q

Reduce echo on dialup VoIP service

How do I reduce echo and delay over a 56K dialup VoIP service? Unfortunately a dialup line is not ideally suited to provide high quality VoIP (at least with today's technologies.) Of course if you would normally pay a fortune to long distance service (either because you have a long distance relationship, call your parents all the time or make calls to a country with very high rates) you are probably willing to accept some degradation...

to save a lot of money. If it turns out your dialup connection does not have very good throughput and you need better quality, then you should really consider DSL, cable modem or some other type of broadband connection to run VoIP.

There are some simple things to check:

  • Throughput of your dialup connection. Are you really getting 56k bit/sec? When I dialup from home, the connection is pretty bad resulting in very low throughput (about 20k bit/sec. when I'm lucky). You may want to test your dialup line to see what your real throughput is. There are a number of Web based tests you can use - you should try several of these tests and compare the results:

    http://dslr.net/faq/3702
    You need to remember that there are a couple of things that can affect your dialup throughput - mainly the throughput of your analog dialup connection to your ISP or the performance of your ISP to Internet. These tests will not tell you what is the problem but they will tell you your throughput. If you are getting much less that 56k bit/sec. you will have sporadic VoIP problems.

  • Throughput of your analog dialup connection (from your modem to the modem at your ISP). I would expect that this is 90% of your problem. One way to confirm this is ping the default gateway of your ISP. If you use Windows, open a DOS prompt and type "ipconfig" to get the IP address of your ISP's default gateway. Then type "ping" followed by the IP address you just found. If you get high latencies with wide variations, then this will confirm that your analog connection is the biggest culprit to your performance problems.
  • Performance of your ISP beyond your analog dialup connection. Sometimes the ISP you are using significantly oversubscribes their network. If it looks like your throughput over your dialup is good, then your ISP may oversubscribe too much or just have a poor connection to a large Internet backbone provider. This happens less frequently than in the mid-90s but some ISPs still have this problem. Pinging different destinations beyond your default gateway will confirm whether this is a problem. Try pinging the Web site of a big company headquartered in your city.
  • Are you running other applications while using VoIP? If so, stop it. Your dialup connection isn't smart enough to prioritize VoIP so your VoIP session will suffer if you are sending/receiving Web traffic (or anything else) at the same time.
  • Are you running VoIP directly between two computers? Remember that if the person at the other end has a poor connection then the VoIP call will be impaired even if you have great connectivity and throughput.
  • This was first published in January 2003

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