🚀 go-pugleaf

Will@cup.portal.com (Will E Estes) writes:

>I would like to get opinions on pros and cons for setting up an
>Internet.  The two setups are:

    You didn't say what sort of sites you're connecting, but from
    your mentioning connecting sites to a PDN, I'm thinking you've
    got clusters of machines, with the clusters connected by X.25
    over PDN...if that's a bad assumption, sorry.

>1) All sites on the internet have routers that attach to a public
>data network, like UUNET's Alternet, and use TCP/IP to communicate
>between nodes on the net.  To the extent that X.25 might be used
>underneath TCP between the routers, this is invisible to the
>applications.

>2) All sites on the internet connect directly to an X.25 network,
>and any client-server applications between two sites are written
>directly to an X.25 API or to some software abstraction that is
>written on top of X.25.

>What are the advantages to either approach?  Clearly 2) is going
>to be more efficient since you don't have the extra error-checking
>of TCP and you don't have the extra data bandwidth of the router
>headers being attached to each packet.  This advantage aside, are
>there any decisive advantages that argue for approach 1)?

    Approach 1 (TCP) buys you the flexibility of using a standard
    API (sockets, streams, etc.) while retaining the flexibility of 
    changing/adding to your underlying network technology as your network
    grows, changes shape, etc. and communications technology improves.
    You can mix/match non-X.25 network elements with your existing X.25
    parts, and your applications just keep working.

Steve Huston                        +1 508 620 2800 ext 3099
Huston@Relay.Prime.COM              Prime Computer, Inc.

The opinions expressed above are not necessarily those of Prime Computer.

In article <38836@cup.portal.com> Will@cup.portal.com (Will E Estes) writes:
>I would like to get opinions on pros and cons for setting up an
>Internet.  The two setups are:
>
>1) All sites on the internet have routers that attach to a public
>data network, like UUNET's Alternet, and use TCP/IP to communicate
>between nodes on the net.  To the extent that X.25 might be used
>underneath TCP between the routers, this is invisible to the
>applications.
>
>2) All sites on the internet connect directly to an X.25 network,
>and any client-server applications between two sites are written
>directly to an X.25 API or to some software abstraction that is
>written on top of X.25.
>
>What are the advantages to either approach?  Clearly 2) is going
>to be more efficient since you don't have the extra error-checking
>of TCP and you don't have the extra data bandwidth of the router
>headers being attached to each packet.  This advantage aside, are
>there any decisive advantages that argue for approach 1)?

Don't bet on approach #2 being automatically more efficient.  A router
can run a number of parallal X.25 connections and spread the traffic
across those.  (You may find some X.25 providers will constipate a
given X.25 virtual circuit well before you exhaust the interface
circuit bandwidth, so by using multiple VCs you can push more
packets.)

And I doubt that you will reach data rates over the typical X.25 (or
TCP or OSI over X.25) that will even begin to make the TCP/IP or OSI
checksumming, etc increase to a noticable level.  (This is not to say
that some networks may offer high performance X.25 service.  It's just
that most of the providers that I see don't.  If they did then your
overhead concern would begin to be meaningful.  But I suggest that you
might find that the burden of dealing with X.25, even at low data
rates, greatly exceeds the cost of TCP/IP or OSI connectionless
network and transport layer.)

Approach #1 will give you more portable code (assuming you are
programming to a fairly standard interface like "sockets".)

				--karl--

One question which I have not seen addressed is the cost of the media.  
X.25 lines are typically charged by the (X.25) packet.  Therefore, your
monthly cost can vary widely, depending on how much data is sent.  All
of the present IP network providers sell you a pipe of a given size,
say, 56k bits per second, for a flat rate regardless of actual usage.

	David Hayes