[asterisk-users] Where is the Digium DS3 card?

[Steve Totaro]

On Mon, Apr 7, 2008 at 2:46 AM, Alex Balashov <abalashov at evaristesys.com> wrote:
> Steve Totaro wrote:
>
>  > A T3 MUXed into 28 T1 PRIs in one, or a few trunk groups inherently
>  > has redundancy.  If a box dies, the calls are dropped (unless you are
>  > doing reinvite) and any call backs go right to the
>  > Ts that are not in alarm.
>
>  True - and if you're simply using CT3 as an economical method of getting
>  say, a dozen T1s into a gateway, that is probably an advantage.  But if
>  that's the case, it would not be cost-effective to shell out extra money
>  for additional PCs with quad T1 cards just to provide failover in the
>  event that the primaries fail.  80/20 rule and all that.

7 HP DL320s, RAID 1 with Quad Sangoma.  Not a dozen but more than
twice that, 28 T1s.  What is your cheaper solution?  Also, have two
cold spares in the rack.  DL 320s are cheap and "rarely fail" using
1.2.X.  I actually cannot remember a single failure over years of
operation.

I have no idea what you mean "if the primary fails".  Are we using
Windows NT, does the secondary domain controller take over?

>
>  The point is that most people that want a DS3 interface really do want
>  to pump in a DS3's worth of calls, more or less, in which case they
>  really can't afford to have those DS1s going spare just for redundancy's
>  sake.  And if you are doing substantially less than a DS3's worth of
>  calls, you probably shouldn't be looking at a DS3 interface to begin
>  with unless that's just an incredibly lucrative way to get channelised
>  PRIs in from a vendor - and with typical the cost of UNE DS3 loops vs
>  T1s, that's not necessarily so.

I don't think you have much experience with DS3s, correct me if I am wrong.

While pricing many solutions, it is either 14 or 16 T1s where a DS3
becomes about the same cost for the loop, that is a lot of wiggle
room.  Would you pay for 16 of something you need or take 28 of
something you surely will need down the road.

>
>  Secondly, an industrial-grade ISDN media gateway designed for telco
>  environments (like a Cisco AS, say) isn't going to go down frequently
>  enough to merit this kind of concern.  Don't get me wrong, I am the last
>  to go on record saying that Cisco voice equipment (or any other) doesn't
>  fail from time to time -- ha.  But, again, 80/20 rule.  A PC is much
>  more likely to fail within the same MTBF.
>
>  So yes, a single gateway handling a DS3 can go down.  But so can an M13
>  mux.  You've got single points of failure either way.

Read the specs on the Adtran 2800 MX13.  I don't think it is going to
fail unless you smash it or pour coffee on it.  Google it and RTFM
before you spout off about a product you obviously have no knowledge
of.

>
>  If one is in the sort of environment where such high availability really
>  is a concern (typically a telco setting), one probably needs to invest
>  in a big DACS and redundant, protection-switched DS3 paths (and
>  protection line cards for them on the DACS side) as well as redundant
>  gateways, or at least redundant DS3 line cards in the chassis.  At that
>  point of stringent availability, this discussion becomes a wee bit moot
>  because most likely you would not be using Asterisk and PCs in such a
>  setting anyway.

We are talking DS3 here, not OC12.  Talk about overkill.

>
>
>  > Running stripped down Linux OS boxen with quad port T1 cards and four
>  > or five lines in extensions.conf, no unneeded modules or software
>  > loaded, asterisk 1.2, entries for zaptel and zapata, and a couple
>  > entries in sip.conf builds a worry free solution.  Asterisk uptime 2
>  > years, system uptime two years and twenty minutes.
>
>  Yes, but total cost of ownership goes up because you need someone to do
>  all that, and even so, despite the impressive uptime you mention, PCs do
>  need a lot more maintenance, upkeep and worry.

Original setup takes a little time, reviewing the logs a couple of
times a weeks takes a minimal amount of time.  Rotating logs should be
automatic, what else is there?

>
>  With dedicated media gateways, you just plug in, set up and it works.
>

They are essentially small servers, some with solid state and flash,
others with real hard drives.  Ever open one up?  I would prefer to
pop a case and replace a T Card, memory, hardrive, powersupply, fan,
then waiting on an RMA.  Especially when your call center is losing
$26k an hour.

Thanks,
Steve

PS, all I know is what works well for a 15k-20k calls a day center
with the average call lasting fifteen minutes and EVERY second of
every call being recorded.  Maybe I am a newb.