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SUMMARY OF DACS VENDOR RESPONSES:
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Original Message:
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We are considering using Digital Access Cross Connect units (DACS)
to split T1 local loops into fractional T channels. Given that
our current knowledge of DACS does not extend significantly beyond
the ability to spell the acronym, I am soliciting advice from the
network group for recommended hardware vendors. Cost is not an
object, we are primarily concerned with choosing the 'industry
standard' manufacturer with the highest reliability and knowledgeable
technical support. Please share your experiences (positive or
negative) with DACS equipment. In an effort to minimize traffic on
the NANOG list, I request that responses be sent to my e-mail address
and I will submit a summary when all the votes are in. The vendors
under consideration now are Adtran, Eastern Research, StarDAX, and
Fisher Price (we have some reservations about the latter product).
We will be splitting T1's into 128's, 256's, ... (not 56Kb lines
because the lower bandwidth lines have 56Kb local loops). The T1
lines would typically be split into a maximum of eight various
speed ports (128-512, occasionally 56, but not typically). I am
assuming that products exist to split directly into a 256Kb without
requiring that multiple 56's to be bundled, but this may not be the
case (I would appreciate clarification on this point). We may
subsequently use it for 56K lines, so a chassis that supports both
8-way and 24-way cards is helpful. Approximately 50 T1's are currently
candidates for splitting to lower bandwidth. Our preference is to use
multiple small capacity DACS rather than larger 'megaDACs' to minimize
the impact of a chassis failure. We will have at least one unpopulated
hot spare in each location.
Response Summary:
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Much to my surprise, there does not appear to be a single dominant DACS
vendor. It seems that DACS manufacturers can do no wrong because nearly
all respondents were quite satisfied with the product they had selected.
The most popular device appears to be the Alcatel (formerly DCS) product,
followed closely by the Tellabs Titan series DACS. There was a series
of other choices, listed in approximate order of popularity, including
NewBridge, Adtran, Lucent, Fujitsu, and Nortel. The only universally
maligned product was the Fisher Price unit mentioned in my original
message. Buddy Venne provided some keen insight into the issues and
concerns with this vendor:
btw, I would give up on FP also, the rumor is that they are
about to be bought by Mattel and that will dilute the value
of their networking hardware, especially the pool equipment.
Aled Morris suggested using Cisco's Lightstream 1010 to channelize lower
bandwidth lines through a single T1 line. This is an excellent solution
when Cisco routers are deployed and all interfaces are contained within
a single router. We have begun experimenting with this option in our
newer Cisco interfaces; however, we still need a DACS solution for the
older interfaces that span multiple routers.
Peter Helmenstine provided the most succinct summary, repeated verbatim
below:
FCC requires the Bells to use multiple vendors like: Fujitsu, Lucent,
Nortel, Alcatel, TelLabs and a few others. In my experience:
USWest uses all above
Level3 uses Alcatel(DS1s)
NextLink uses Nortel(DS3s) and Tellabs(DS1s)
Bell Atlantic primarily uses Fujitsu
Bell South primarily uses Lucent
PacBell primarily uses Nortel
TCG/AT&T uses Lucent
MFS/MCIWorldCom uses Fujisu
This following book has a section describing features of different
vendors:
Sonet : A Guide to Synchronous Optical Network by Walter J. Goralski
http://www.amazon.com/exec/obidos/ASIN/0070245630/o/qid=938033335/sr=8-2/002-7812377-7313452
One respondent cleverly constructed a cross connect unit out of ATM
switches using circuit emulation cards. I don't feel quite up to this
task even though I believe I once saw MacGyver perform a similar feat
(though, if memory serves, MacGyver was blindfolded and had to construct
the emulation cards out of chewing gum and a discarded paper clip).
Final Selection:
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We will evaluate three products - Alcatel, Tellabs, and Adtran. The
first two are selected because they are the most popular, if not
dominant, products. The Adtran is attractive for our specific
environment because we have used their products extensively for many
years and have been satisfied with both the products and the vendor.
I would like to thank the following for their extremely helpful
input (hopefully I haven't left anyone out):
Erik Montemer <[email protected]>
Tim Hodges, Triangle Tele Coop Assoc. <[email protected]>:
Joe Abley <[email protected]>:
Kevin Cappis <[email protected]>:
Don Pace <[email protected]>
Venne, Buddy <[email protected]>
Chad Skidmore <[email protected]>
Richard Newcomb <[email protected]>
Peter Helmenstine <[email protected]>
Paul E. Erkkila <[email protected]>
Wilson, Chris <[email protected]>
Rob Russo <[email protected]>
Aled Morris <[email protected]>
Dave Cooper <[email protected]>
Andy Ellifson <[email protected]>
Administrator <[email protected]>
Ron Buchalski <[email protected]>
Peter Polasek <[email protected]>
Gant, Patrick <[email protected]>
Alex Rubenstein <[email protected]>
Jim Hart <[email protected]>
I have included relevant excerpts from all responses below for the
enthusiastic reader.
Thanks,
Peter Polasek
[email protected]
<--- begin included responses --->
From: "Erik Montemer" <[email protected]>
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I'm not a telco DACS backbone guru. My experiences with Tellabs, has been
pretty positive, the ease of use when doing frame cuts, made for less
downtime, and less work. The Tellabs 1/0 DACS also was easy to configure
for circuit simulation when testing different types of scenarios before
deploying various services. I've only had experience with Tellabs 1/0 (ds-1
to ds-0) DACS, and Tellabs 3/1 DACS (DS-3 to DS-1).
As far as industry standardization is concerned, most vendors should be
compliant with ITU, ANSI T1 standards, as well as their accompanying
signalling standards. I honestly don't think there's one specific DACS used
as an exemplary standard. It all depends on who's purchasing the DACS, how
convincing the sales rep is, and/or if upper management considers bottom
line over delivering quality service. I would say a majority of telcos use
Tellabs, or Adtran, but I could be wrong. Hope this helps.
From: "Tim Hodges, Triangle Tele Coop Assoc." <[email protected]>:
-------------------------------------------------------------------
I work at a independent rural telephone company. We replaced our
CO DACS last year with one made by DCS. They have since been
bought out by Alcatel.
The general terminology for DACS are like 3/1/0 for a box that will
take DS3/T-1's/DS0 for example. The one we bought is a 3/1.
We have been pretty happy with it, but it is a pricey product.
From: Joe Abley <[email protected]>:
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We build a digital cross connect out of a Stratacom BPX ATM switch
using circuit emulation cards. We found that we could build a unit with
equal capacity to that available on our previous DCC for much, much less
money (plus we get a useful box to play with once all the legacy
circuit-based services are finally banished). Just something you might
like to think about (it worked for us).
From: Kevin Cappis <[email protected]>:
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Check out Newbridge if cost is not a factor. They have been around for
quite awhile, and have a good reputation. For something a little cheaper
(less features), but good and reliable, look into Alcatel. They have a
nice 1/0 mux that's not that expensive.
From: Don Pace <[email protected]>
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Take a serious look at the tellabs DACS equipment . It is being used by
many a phone company. They sell a real nice 8 port T1 unit that uses
the same cards as some of their larger units. They have units that
that grow as big as you want them. The craft guys around here love
them.
From: "Venne, Buddy" <[email protected]>
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I would greatly appreciate seeing the final summary, I may need to DACS some
T1's for fault-tolerance reasons, if one T1 were to go down, a back up line
can be moved in place. As well, I could use the lines as test lines during
non-production hours.
btw I would give up on FP also, the rumor is that they are about to be
bought by Mattel and that will dilute the value of their networking
hardware, especially the pool equipment.
From: Chad Skidmore <[email protected]>
---------------------------------------------
One of the recognized leaders in DACS equipment is Tellabs. Take a look at
their Titan 532 at http://www.tellabs.com if you are just looking for 1/0
DACSing.
From: Richard Newcomb <[email protected]>
--------------------------------------------
However both Newbridge and Alcatel offer this product, with
Alcatel having a wide variety of options.
From: Peter Helmenstine <[email protected]>
-------------------------------------------
This book has a section describing features of different vendors:
Sonet : A Guide to Synchronous Optical Network by Walter J. Goralski
http://www.amazon.com/exec/obidos/ASIN/0070245630/o/qid=938033335/sr=8-2/002-7812377-7313452
FCC require the Bells to use multiple vendors like: Fujitsu, Lucent,
Nortel, Alcatel, TelLabs and a few others...
In my experience:
USWest uses all above
Level3 uses Alcatel(DS1s)
NextLink uses Nortel(DS3s) and Tellabs(DS1s)
Bell Atlantic primarily uses Fujitsu
Bell South primarily uses Lucent
PacBell primarily uses Nortel
TCG/AT&T uses Lucent
MFS/MCIWorldCom uses Fujisu
From: "Paul E. Erkkila" <[email protected]>
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Titan. 0-1 for ds1->frac 3-1 for DS3->ds1. We've got hundreds of them
in place.
From: "Wilson, Chris" <[email protected]>
--------------------------------------------------
The telco industry generally standardizes on Alcatel, Lucent, and Tellabs.
I've heard more and more negative feedback about the Tellabs products
laterly. I'd say of the three, Alcatel is the way to go.
From: "Rob Russo" <[email protected]>
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Adtran is one of the better ones... have you checked out CAC (Carrier Access
Corp)? I am not sure if they have this, but they have other device with
built DACS....
From: Aled Morris <[email protected]>
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The Cisco Lightstream 1010 can do this using the T1 channel cards.
(I assume you want a T1 trunk split into two or more T1 tribs with N
timeslots cross connected, if you want V.35 presentation of the tribs then
ignore this message!)
Although it isn't strictly a DACCS, you might feel more comfortable
supporting a Cisco device depending on what else you have in your network.
From: Dave Cooper <[email protected]>
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Depending on what kind of capacity you are talking about, the industry
standard for 1/0 DACS' is the Alcatel. however, for the smaller/less
volume, i have heard that the newer StarDAX's are pretty nice.
From: Andy Ellifson <[email protected]>
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AT&T Local Services uses the Lucent product for DS0 DACS.
From: Administrator <[email protected]>
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I have had excellent luck with the Adtran Atlas 800 product in several
sites over the past year. It has just the right mix of port density
and flexibility for our current needs and has some very slick PRI
switching capabilities as well. Uptime has been 100% for ~8 months
now (single PSU, 120 VAC) other than when we were upgrading software
images. Speaking of that, whenever you load a new image (to the main
unit or a module) you can schedule the reboot for a later time--allowing
you to do the upgrade while you're in the office and have it restart
at 0200 for example.
The user interface is intuitive and well-crafted--wish I could say
the same about some of our other vendors' interfaces. The tech support
comes from a special group dedicated to/trained on the Atlas line and
they have always answered my calls or returned them within an hour.
They even got us a custom SW load to deal with a new ISDN parameter
in less than a week. I'd gladly buy (and plan to) more of them.
From: "Ron Buchalski" <[email protected]>
--------------------------------------------
A simpler solution which would require less space, power, money, wire pairs,
and administration for your group:
1) Provision a few Channelized DS3s into your LEC network
2) Install Channelized DS3 into your router
3) Let the LEC be responsible for owning/managing the DACS, and provisioning
the FT1s/T1s onto the T1s within the channelized DS3s.
You'll save the space and power normally required for banks of T1 CSUs and
the DACS, and you won't need to manage the crossconnects for the DACS.
Circuit-wise, it should cost you less to provision your T1s into your
facility via a few DS3s rather than fifty T1s, and you won't eat up your
incoming telco wire facilities quickly.
From: Peter Polasek <[email protected]>
From: "Gant, Patrick" <[email protected]>
----------------------------------------------
Look into the Adtran ATLAS 800 product.
From: Alex Rubenstein <[email protected]>
------------------------------------
TadIran is making some really nice, yet inexpensive stuff.
Also, TelInc is making one that is really cheap, but only handles four
DS3's; perfect for the remote pop. I'm thinking of getting one of those.
Something like $12k for a 3xds3, 30xds1 system.
From: "Jim Hart" <[email protected]>
------------------------------------
You might want to consider the DACS-II from Lucent the AX/4 or AX/11 (4 and
11 Slots models). We have a need for doing something similar and this seems
that it would more than fit the bill.
http://www.lucent.com/dns/products/dacs.html
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