Some questions on Public data networks

Some questions on Public data networks

Post by Robert L Ullma » Sat, 07 Nov 1992 10:41:40




>  I have some questions on Public data networks for which comp.dcom.telecom
> [...]
>    *  Value added networks of common carriers (like AT&T) never cross paths
>       with their voice networks. ie traffic on one never use the other network.
>       Am i right?

If you mean in the sense of competing-on-demand for switched service, you
are right, with one significant exception. The facilities are not shared,
but they are often multiplexed onto different channels on things like
fiber trunks. (I.e. you will find the bits on the same fiber.)

The exception is interesting: carriers are offering a new type of leased
service that is actually implemented by a dialed call that is then held
up, rather than a fixed administrative ("nailed-up") circuit assignment.
The advantage for the telco is that when one of the legs of the circuit
fails, it is automatically taken out of service, and the leased circuit
automatically grabs another path.

I understand that this type of leased circuit is used for some paths
within PSDNS, and therefore (where the underlying service is ISDN/SS7)
will actually use paths used for voice traffic a moment before. But I
do not think anyone is doing this in dynamic response to offered load.

Quote:>    *  Public data networks (common carrier VANs, Tymnet, Telnet etc) are not
>       as extensive as plain old telephone networks. ie if someone in some
>       remote place in say oklahama wants a data connection , most probably he
>       will not get it. Is this right?

A PSDN connection is a nailed up circuit (telephone circuit) to a nearby
X.25 switch. You can get them anywhere you can get telephones, for varying
amounts of airmile charges. This even applies to some 3rd world countries,
not just the US. Oklahoma is no problem at all. (You can get access from
Sprint Intl in Moscow and a bunch of other Eastern European cities today.)

Quote:>    *  Internet, Bitnet 'et. al.' do not use any public data network - they have
>       their own infrastructure which is not shared with anyone. Is this right?

Almost all links in the Internet between organizations are leased circuits
run by Internet providers (JvNCnet, NEARnet, PSI, PIPEX, etc). Links within
organizations are of various flavors, including on-demand X.25.

Quote:>    *  Common carrier offerings like Frame Relay, SMDS do not use thieir plain
>       old voice infrastructure. I'am wrong. Right?

See answer to first question. :-)

Quote:>  thanks.
>  Sashidhar

You are welcome,
Rob

--

Quand Maigret poussa la porte du Tabac Fontaine, vers une heure et demie,
le patron du bar, qui venait de se lever, descendait lentement un escalier
en colima??on qui s'amor??ait dans l'arri?re-salle. ... Arriv? derri?re le
comptoir, il repousa le gar??on d'un geste n?gligent de la main, saisit
une bouteille de vin blanc, un verre, m?langea au vin de l'eau min?rale et,
la t?te renvers?e en arri?re, se gargarisa.  -- Simenon

 
 
 

1. Some Questions on Public Data Networks

I have some questions on Public data networks. Any response would be
greatly appreciated.

* Value added networks of common carriers (like AT&T) never cross
paths with their voice networks. ie traffic on one never uses the
other network.  Am I right?

* Public data networks (common carrier VANs, Tymnet, Telnet etc) are
not as extensive as plain old telephone networks. ie if someone in
some remote place in say Oklahama wants a data connection, most
probably he will not get it. Is this right?

* Internet, Bitnet 'et. al.' do not use any public data network - they
have their own infrastructure which is not shared with anyone. Is this
right?

* Common carrier offerings like Frame Relay, SMDS do not use their
plain old voice infrastructure. I'm wrong. Right?

If you think this is too trivial reply by mail. I will summarize.

Thanks.


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