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Ratio of ISDN Connections

ayottey
ayottey asked
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We need to set up ISDN connections from the main office to multiple branches.  The main office will have fewer ISDN connections than the number of branches.  This is because branches do not need constant connections.

Each branch will be able to dial up, go through a hunt group at the phone company, and connect to the main office router via ISDN.

How can I determine the optimal ratio of ISDN lines at the branches to ISDN lines at the main office?
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BRONZE EXPERT
Top Expert 2007

Commented:
Thisis going to be based solely on the amount of traffic generated.

Trial and error will be your best frinds here.

If you have any networking in place, start using a network monitor to gather statistics.

If this is fresh, then start with 1 , 128 K line for every 10 people, unless you are doing high volume traffic, video or other net intensive tasks.

I hope this helps !

Commented:
a,

I don't think going with the metered isdn service is good solution
Go with a full time dsl connection in the main office and a dial up connection in the remote offices. You can then go with any number of vpn solutions to connect the sites, or you can simply map a drive. There are also dial up dsl connections available.

Good Luck!

Commented:
a,

I don't think going with the metered isdn service is good solution
Go with a full time dsl connection in the main office and a dial up connection in the remote offices. You can then go with any number of vpn solutions to connect the sites, or you can simply map a drive. There are also dial up dsl connections available.

Good Luck!

Commented:
Your ratio will depend on many variables. Are all branches in the same time zone? What is the estimated duration of connection for each branch? How often will they connect?
You will probably have to go with intuition for your answers. In my situation, I have a 12:1 (branch:main)ratio, and sometimes the remote sites have to wait for a line to free up.

Hope this helps.
Commented:
jwc02026,
Your comment:
"I don't think going with the metered isdn service is good solution"

Based on the fact that there was no background given as to why an ISDN solution was chosen, what are you basing this comment on?  Since I don't see any reason in the question to have come to this conclusion, are you suggesting that all of the carriers in the world shut down their ISDN switches and call it a day?  

So you know, in many countries ISDN is one of the only viable network solutions available.  Even in the states DSL service is not available everywhere.  This combined with the fact that CLECs claim chapter 11 almost daily, you get no SLA, and you have to implement VPN technology (most of the time) for site to site connections, do not make DSL an optimal solution in many cases.  However, it is good for many solutions, such as home use, small office use, etc.  ISDN for site backup is the solution of choice for many reasons in my mind, although not every time.

My end point here is that it is good to come up with alternate solutions, but suggestions need to come from an informed point of view, rather than an arbitrary one.  My suggestion is that before telling someone that they are making a poor decision, make sure you have gathered all of the facts first.

I'll get off my soapbox now.

In response to the question, I agree with bsadlick, but there are other things to consider.  How often do the primary lines go down?  Do you need to use both channels as a backup, or can you get by with one channel, allowing more simultaneous connections at the main site over less lines.  One thing to not get trapped by is thinking that ISDN is 64k or 128k (1 channel or 2 channels).  This is pure data throughput with no overhead.  No other technology out there is rated like that.  If you have a 128k frame line, you really probably only have about a 100-105k line due to the overhead.  However, since all ISDN overhead happens outside the B channels, you actually have a larger pipe than you think.
I don't think there is any hard-and-fast ratio guidelines to go by.  My feeling is that you just need to figure out your situation and it will be a best guess from there.

Hope that helps.

Commented:
Scriag,

I understand your point and it is valid overall, however, I say this from personal experience as I have used ISDN in the past. In a cost analysis of the simple meter charge, not the lease cost, v/s the cost of DSL, DSL comes out the winner every time. This in conjunction the greater line speed of DSL makes DSL the clear choice.
In fact, in my analysis, ISDN was 3 times more costly overall than DSL.
As long as Avoitty chose a DSL provider that owned their lines rather than leased the lines, the likely hood of the provider going out of business is slight, especially now with the holes left in the industry.
I'm sure Avoitty will find out the hard way, once one person does not shutdown their connection, and he receives a $1200+ phone bill for that month, that DSL may not have the correct choice.
While limiting the access time for such connections is an answer, this solution only inhibits productive employees as they will no longer be able to do much of their jobs after hours, which, of course, will only lead to missed deadlines.
Given the context of the question, it is clear that Avoitty is something of a novice in this area, and deserves all the information he can get.
I do not make such comments lightly.

Anyway
Peace

Commented:
Hmmm, so basically what you're telling me is that regardless of the situation, cost is the only factor.  Therefore, it doesn't matter where he lives or the availability of DSL.  It doesn't matter what protocols need to go over the lines, or the nature of those protocols.  It doesn't matter what his experience level is for implementing a truly secure VPN is.  As long as its cheap, it doesn't matter.  

So if none of that matters, why does ISDN exist?  Why do people buy Frame or leased lines smaller than the maximum available DSL line?  Why are DSL providers going out of business daily?

ISDN may be more expensive in his scenario, but that may not be the driving factor.  I have used both extensively, and can tell you that DSL has a number of short-comings even when it is available.  For example, for web based protocols its great, but have fun with anything latency sensitive such as terminal server traffic - and when it goes down, those 24 hour SLAs are really comforting.  However, it is cheap so you don't care.

I am not saying that ISDN doesn't have problems - and you mention some good points.  But having a one size fits all mentality doesn't constitute good advice.  You confirmed my very point - that you told him what he should do while knowing nothing about his situation.  Would you be telling him the same thing if he told you he was in Singapore?  Heck, I live in the Midwest where it was originally installed and can't get it to my house because I'm too far from the CO - and I'm only 20 miles from downtown.

One last thing - you mention that ayottey is a novice in this area.  Now what are you basing that on?  Last I checked, he didn't even ask for recommendations on topology.  He asked a provisioning question on the topology he has chosen and it seemed like an intelligent enough question to me.  

Anyway, its a free board - you can say what you want and let whoever judge for themselves.  I'm certainly not the watchdog for this site.

Commented:
scraig

if in reading the question you cant understand why i recomeneded such a solution, then perhaps you should break your soap box.

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