Re: Low latency IP direct connection over ISDN

On Wed, 14 Nov 2012 00:37:55 +0100, Matthias-Christian Ott <[email protected]>  
wrote:

>
> On 2012-11-12 02:42, Birger Harzenetter wrote:
>> On Sun, 11 Nov 2012 19:20:07 +0100, Matthias-Christian Ott
>> <[email protected]> wrote:
>>
>>> I want to connect two sites in Germany with minimal latency under low
>>> bandwidth requirements. Both sides have numbers with the same area  
>>> code.
>>
>> Same area code only helps if it's the same telco, off course.
>
> It would be Deutsche Telekom I guess (at one location I can confirm
> this, at the other location would have to find out if they transitioned
> to an IP-based solution already or something similar), although I

In that case there would be no hope.Voxtream ISDN Parlay i4-CD Basic

> couldn't find any offerings for leased ISDN lines that I would have to
> configure an on-demand (dialled) connection or have to take a much more
> expensive 2 Mbit/s leased line which probably requires expensive
> equipment as well which is perhaps obsolete in a few years (I'm

ISDN is probably obsolete in a few years :-(


>>> Can latency be improved via ISDN (I've read contradicting statements
>>
>> Definitely.
>
> Do you have some exemplary numbers (you could save me several hours of
> work setting up two newly installed computers with old ISDN cards just
> to perform a short test)?

You're asking several years too late.


>> But even if the call takes the long way, the latency will be MUCH lower.
>
> Why (I'm not really familiar with how current telecommunication networks
> are built; you read contradicting things about this on the internet)
> shouldn't ISDN and IP be transferred over the same lines?

It's not so much about the distance than about protocols.
With all those layers on DSL you get a lot of (re)packetization.
Error correction gives very big latencies as well. (see interleave vs.  
fast path).
So if you use a dial-up connection you will skip some of these layers.
Or actually you didn't mention what kind of data transfer you need. If you  
don't need IP, you might skip them all together, just sending single  
octets without further delay.

   Greetings,
     WIMPy