TELECOM Digest OnLine - Sorted: Re: VOIP and Telnet

Re: VOIP and Telnet

Hank Karl (
Sat, 30 Oct 2004 13:49:32 -0400

On 27 Oct 2004 13:04:43 -0700, wrote:

> It is possible to have VOIP and be able to connect to machines that
> have modems and use telnet?

I'm not sure what effect telnet will have. You will generally need to
get four UDP sessions connected plus a session for the signaling to
have a VoIP conversation.

Another factor is the modem speed and codec used. You will probably
have to use G.729A or G.723.1 or some other low bitrate codec. So you
can use VoIP over a modem and it can sound OK (I've done this using
Windows Messenger to a colleague in England who only had a "56K" dial
up line, and he sounded ok (It wasn't toll-quality, but I knew who was
talking and what he said).

Codecs use more bandwidth on the Internet than their nominal rate
implies. For example, G.729A (8KHz) generally uses 20 bytes of data
per sampling interval, the RTP header is 12 bytes, and the UDP/IP
header is 28 bytes. If you use G.723.1 at 5.3 KHz, you will have a
smaller data packet, but you don't reduce the rest of the payload. If
you put two or more data packets in a UDP/IP message, you get better
link utilization, but the delay (end-to-end and roundtrip) suffer.

If your system can use header compression, things will go a lot

If you're interested in more details on bandwidth, see

If you'd like to hear what low-bitrate codecs sound like, check out
There are audio files that have been compressed and decompressed for
codecs ranging from 1.2K to G.799A (8K)

On 28 Oct 2004 09:45:56 -0700, (kansasman) wrote:

> wrote in message
> news:<>:

>> It is possible to have VOIP and be able to connect to machines that
>> have modems and use telnet?

>> [TELECOM Digest Editor's Note: If I understand it correctly, VOIP --
>> or at least Vonage -- can do everything a telephone can do. PAT]

> In my experience, in order to have VoIP, you need to have DSL or
> Digital Cable with Broadband. I hope this is helpful!

> I was curious about this too -- and I found this site to be helpful in
> answering some of my basic questions:


Or you could try and see if it works.

> Good Luck!

> [TELECOM Digest Editor's Note: Maybe also the man has not only broad
> band and a fast local area network like myself (and most of you) but
> he also has (built in by default) 'Dial Up Networking' and he now and
> then uses that instead of the broadband, (as I do when I wish to call
> some small BBS type thing.) He wonders if *his modem* will work with
> his Vonage phone on his broadband line. PAT]

On Thu, 28 Oct 2004 14:16:41 GMT, Rick Merrill
<> wrote:

> wrote:

>> It is possible to have VOIP and be able to connect to machines that
>> have modems and use telnet?

> Yes, of course: it is a telephone. But WHY would you want to because
> VoIP requires that you already have broadband or equivalent.

Broadband isn't available everywhere yet. Some people are stuck with
analog modems.

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