Date: Sat, 17 Apr 1999 22:52:31 -0400 (EDT) From: "John T. Farmer" <jfarmer@goldsword.com> To: bill@bilver.magicnet.net, chuckr@picnic.mat.net Cc: freebsd-isp@FreeBSD.ORG, jfarmer@goldsword.com Subject: Re: cheapo 56k hardware Message-ID: <199904180252.WAA17151@rapier.goldsword.com> In-Reply-To: <Pine.BSF.4.10.9904171710010.15061-100000@picnic.mat.net>
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On Sat, 17 Apr 1999 17:11:21 Chuck Robey said:
> On Sat, 17 Apr 1999, Bill Vermillion wrote:
> > The problem you have is that any digital modem at 56K as the ISP is
> > going to require a PRI (most probably) and a device that
> > interfaces.
> >
> > 56K modems can't be used at the ISP because 56K to 56K is limited
> > to 33.3K
> >
> > > If this is a multithousand buck answer, it's not gooing to be
> > > really practical, so please don't make gold plated suggestions
> > > without awfully good reasons behind it (better than just enhanced
> > > reliability).
> >
> > 56K requires a digital link from the ISP through telco, to
> > destination so there is no D/A conversion. The home to ISP
> > is analog and therefore requires a D/A at the home and an A/D at
> > the ISP. Doing two AtoD and DtoA conversions limits you to 33.3.
> >
> > It's not going to be cheapo. You can find all sorts of devices on
> > the used marked below 56K - but the last time I looked the 56K
> > devices were still pretty expensive in comparison.
>
> Ahh. The ISP in question has a 128K frame relay line, but that would be
> a drop in the bucket. So he has to go buy the service from the telco?
> Or he has to have a T1 from the telco, those are the alternatives?
>
> Yecch!
No the line that they have in for their _backbone_ Internet has _nothing_
to do with what's required to offer 56k service.
I'm assuming that they currently have POTS lines either into rack modems
or individual modems (here after referred to as POTS modems). The POTS
modems are served by the existing terminal server.
Two approaches are possible. The USR/3com way or the Ascend way. (I've
tried both...) Each approach is also available for either BRI (2B+D)
ISDN circuits or PRI (23B+D) circuits. The key is that the dialup POTS
lines _have_ to be replaced by digital circuits of some sort.
The USR method (using BRI circuits) involves:
1. Find an MP/8I or 16I modem bank (new, they're $2800 to $3900.
Used you might be able to grab one $2k. They go fast on
the used market.)
2. Order 4 or 8 BRI ISDN circuits from the telco in a hunt group.
3. Replace the POTS modems with the MP/8(16)-I box, configure the
ports for 115k (or 230k if possible), set all the SPIDs, etc.
and turn the customers loose.
The MP/8-I bank handles 8 incoming analog calls, x2 or v.90. The
MP/16-I handles 16. Either will serve 64k ISDN dial-in. They don't
really handle 128k ISDN very well. You can use the Courier I-modems in
place of the MP boxes at the cost of 1/2 the available channels.
If you want or have to go with a PRI solution, then the cheapest 3com
approach is to find a used Total Control chassis with 1 or 2
PRI interfaces and 24/48 v.90 modems (the newer DSP ones preferred).
This replaces both the terminal server and the POTS modems. Used,
this box is in the $6k to $7k range. (We won't get into the Netserver
vs. HyperArc fiasco... or the cost of software updates...)
The Ascend approach for either BRI or PRI lines also replaces the existing
terminal server & POTS modems with a new box. For BRIs, the Max1800 with
1 or 2 Series56 digital modem cards is the call. Used it runs $2k for the
base unit & $1k to $2k for the digital card(s). Handles upto 8 BRIs,
serves up 64k or 128k ISDN cleanly, serves up 56k (k56 or v.90) upto the
number of modem ports (8, 12, or 16). For PRI service, the boxes to look
at are the MAX2012, MAX2024, MAX40xx, or MAX60xx. They use the same modem
cards as the 1800.
The MAX 20xx boxes are the same basic unit as the MAX1800 with the BRI
interfaces replaced with 1 PRI port. The MAX40xx boxes have 2 or 4 PRI
interfaces (older boxes have 4 interfaces but not enough cpu housepower
to handle a full load of modems). The MAX4 series have been "end of
lifed" by Ascend & soon won't run the newest versions of TOS. The
MAX60xx will handle a full load of 96 modems (4 PRIs) and is still in
full production.
The MAX20xx boxes can be found used with 12 or 24 modems for $3k to $4k.
The 40xx boxes can be found used with 24 or 48 modems for $6k to $7.5k.
The MAX60xx starts at $10k and can cost upto $30k.
The approach that I would choose would depend on what they're comfortable
with (brands, etc.), the availablity of lines, their total budget, and
the number of clients they're attempting to serve. For example, in
Bell$outh land, BRIs are ~$100/mo. and no distance-based line charge.
PRIs are ~$1200/mo. and are delivered via a T-1 span that you can
figure on paying ~$500/mo for. If you're lucky enough to be served
by a decent ISP-centric CLEC, then you could get PRIs in the range of
$300 to $500/mo. and rack space for ~$300 to ~$500/mo. YMMV.
John
----------------------------------------------------------------------
John T. Farmer Owner & CTO GoldSword Systems
jfarmer@goldsword.com 423-691-6498 Knoxville TN
Internet Services & Servers, Network Design, Consulting
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