atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services T1's, CSU's and DSU's T1 reliability, do I need a backup?

Where I work we currently have 7 POTS lines and two crappy DSL connections (512/512K) (1.5M/128K).

We are in talks about obtaining a Dynamic 1.5M T1 service and connecting our phone system to that. I know very little about the reliability of T1's. Supposedly they are more reliable than POTS lines, but I find that hard to believe.

Anyone out there have real world experience with T1's? Are they more reliable than POTS lines or DSL lines?

Do you think spending $470/mo on a 1.5M T1 circuit and a $60 backup DSL line (1.5/128k) is necessary? Or even keeping an analog phone line?

As it stands switching to the T1 is going to cost us 9 to 14% more a month. So If I can ditch the $60 dsl line it puts us about par with our current setup. -3% to 1% more a month.

It really all depends. I have some customers that lose their service every time it rains and then there are some I never go back and see after installing their service. If your business can live without service (voice and data) for 24 hours or less, then dump the pots and dsl. If not, I suggest keeping a pots line that calls can be forwarded to and keeping the dsl or if you dont need a lot of bandwidth, go to an isdn back up.

Interesting thought. It does appear our firewall supports dial-up connections via serial cable in a wan-failover. So its conceivable.

Do you think ISDN would be better than dial-up?

The number one benefit of a T1 is that it is a direct, dedicated pipe into the Telco. Secondly in the case of pots, if they are true analog pots, an analog to digital conversion is eleiminated which helps thruput. Third, most of the T1 will be transported on fiber and the rest on copper. If your business is far away from the point where the fiber signal is converted to electrical a conventional T1 span will be used. This type of T1 seems to have more issues mainly because of the amount of copper used to connect componets. Newer technology T1s are used on shorter runs can eliminate points of failure because of less copper involved.

A channelized T1 one has twenty four 64kb/s cannels inside it. They may carry voice or data, the configuration is up to you. 12 voice, 12 data, 4 voice, 20 data or you can dynamically switch to any configuration your equipment can handle. Running data at midnight? 1 voice channel for a phone to the data room and 23 channels software connected together to run the data. Then in the morning switch it back to 12 voice and 12 data or whatever.

Many customers choose an ISDN prime T1 to connect from their equipment to the telco. This type of T1 has 23 64kb/s "bearer" channels that can carry voice or data and one 64kb/s "delta" signalling channel. 23B+D. The delta channel does all signaling and control functions for the 23B channels thus allowing the customer to have the full 64kb/s bandwidth availible. When not being used for signaling and control the D channel can be used for other functions.

If your POTs is not reliable chances are that your T-1 wil not be either. Our T-1's travel the last mile on the same crappy copper that makes our POTs stink. Verizon just is not maintaining copper at all in our area. The advantage POTs has over the T-1 is a cable problem only takes out 1 POTs line, the same 1 pair failure on a T-1 takes out all our phone and data.

We also found out after the huricane that most of our POTs and the T-1 come thru a vault that converts fiber to the last mile copper. The vault requires Utility Power to function and has 12 hour backup battery. Guess what happened at the 13th hour of the power failure, we lost all but 3 POTs lines and all the T-1s.

Conclusion is there is lo longer a method to provide reliable phone service anymore and no one at Verizon cares. I should also mention that this is a Fire Dept Dispatch Center and loosing phone service leaves our residents with no way to call for help.

FDTech said it best. There are absolutely zero guaranteed services anymore, regardless of the delivery method used. Gone are the days of five nines.

We either have to depend upon copper that isn't maintained properly or battery-powered substitutes that are a gamble at best. It is a no-win situation.

The last mile of copper has been and will always be the networks Achilles Heel. Until such time that the last mile is converted fiber, Fiber To The Prem, the problems will remain. In our area, not a Verizon, the telco is starting to replce copper cell tower feeds to fiber feeds. The rate of trouble and failure reports to those sites has dropped to almost zero. Hopefully, this trend will continue.

Whatever you do, keep one POTS line that the rest of the numbers can be forwarded to should the T-1 collapse...

You should look into how far you are from the CO, and also for some comparison shopping, all can be found on T-1 shopper website:

https://www.t1shopper.com/

Good luck.

Hm... This concerns me. I guess the goal I had in mind for switching to T1 was that our connection to the outside world would be stronger, not weaker. Both our DSL connections are plagued with high ping and packet loss. Our POTS lines seem to be pretty stable. I cant remember having any problems with them. One exception was the time someone cut a wire shoved it back in the box.

If our POTS are stable but our DSL is crappy do you think switching to a T1 service would make any difference? Sounds like it would make it worse if a T1 can be brought to its knees by 1 bad pair.

As stated earlier, all your eggs are in one basket with T-1. One or two pairs of wires (depending on how the LEC is bringing the circuit to you) carries 24 64 Kb/s channels, or in the case of an ISDN PRI, 23 bearer channels and one signalling channel (D channel). The upside is the LEC has to maintain the T-1 at 1.544 Mb/s. That's a standard. The whole shebang quits if that data rate is not maintained. This is good news for you as it will dramatically improve your data service. If the T-1 is provisioned properly and you use decent terminating equipment, your voice circuits should also improve.

The down side is one little copper fault and you lose it all. Our method of dealing with copper T-1 on a shaky span is to back up the T-1 with, at least, two POTS lines and in your case, 1 DSL for data. You could also use an ISDN BRI line which would give you one data line and one voice line. That would provide some savings.

Rcaman

"Both our DSL connections are plagued with high ping and packet loss"

The reason both your DSL connections are plagued with high ping rates and packet loss is because DSL is not a private line. It is a connection oriented connectionless serice. The rules state in the case of congestion in the network low class packets get discarded.

Remember DSL is an ACCESS method only. It doesn't gurantee delivery.

Have you considered a Fixed Wireless medium for backup? That would be a TRUE from of redundancy. Fixed Wireless can be configured to immediately operate as a fail-safe in the event of a DSL/Cable/T1 outage.

Btw, regarding T1s: absolutely yes they are more reliable than a POTS. Yes they do run over the same type of copper, but T1s use a 2 pair (4 wires). A T1 also includes an SLA (service level agreement), which means the carrier has to honor a certain level of uptime (usually 99%) + consistent throughput/latency.

T1 is a DEDICATED medium, not shared like DSL, Cable, or POTS. T1s have a mandatory mean-time-to-repair (MTTR). In other words, if your DSL or POTS line goes down, the telco will just 'get to it when they get to it'. However with T1, they are contractually obligated to get service back up and running ASAP, or you will have recourse. Which usually comes in the form of a service credit, or if it's a consistent problem, you may be able to terminate your contract. There's a HUGE difference in service quality between DSL and T1, hence the price difference. Feel free to contact me directly if you have any other questions.

Oh no they don't. HDSL has been the norm for at least five years, meaning one pair is being used to emulate a T1. With that being said, the risk of failure of a typical T1 over copper remains quite high.

Even if the telcos were using two pair delivery of T1 circuits, a failure of either pair would still render the circuit inoperable.

Ed is correct in saying that HDSL is the norm nowadays...

If the loop length from the CO is less than 6,000 ft, expect a single-pair HDSL using Adtran H2TUC/H2TUR cards.

Should the distance be longer, a 4-wire HDSL will be delivered, mostly on Adtran's H4TUC/H4TUR.

These are Verizon's guidelines for five boroughs of NYC - I'm sure that they vary by LEC and area served.

Where I agree with TeleServPro is the fact that response time for a T-1 (from the moment the circuit is reported down to dispatch in/out) is expected to be within a 4-hour window, which is a pipe dream for a POTS line and that includes DSL, which is serviced by POTS garages.

Once again, if you get a good deal on a T-1 go for it, but keep *at least* one POTS line as a backup...

I know that keeping a POTS line was common practice years ago ...... but with cell phones doesn't it make more sense to forward to a cell phone since you can have multiple calls forwarded at once?

True, but one could use the POTS line for sending/receiving faxes as well...if and when that T-1 bites the dust...maintaining *minimal* business presence...

Yes thank you for the clarification. I also realize transit via PairGain is used quite often these days. However I tend to work more in remote areas where a 2 pair is still the norm.

Quite high compared to what? I hardly ever experience T1 outage problems unless a backhoe has dug into the cabling- or VERY inclement weather conditions..

@TeleServPro:

You're likely working in area where the copper is still in fairly good shape. Some of us are not that lucky...

The bottom line is, if OP has reliability issues with his current setup because of less-than-pristine cable feeding his premise, he'll likely have issues with a T-1 if fed out of the same decrepit box...

We tend to have outside plant related problems when it rains around here. They have had to switch pairs a few times to get our T1s back up.

Same here, always worse in the summer when it rains more. Around here we always plan on at least 24 hours of outage a year. We have a few copper CO lines (mainly used for fax and modem otherwise) and a few SIP trunks. The SIP trunks are nice for backup as they are only a few bucks a month plus usage, which is non-existent unless there is a PRI outage.

Steve

We have a good mix of fiber T1s and copper, both HDSL and 4 wire. The MOST reliable, without question, is fiber. I have 60 T-1/T-3 on fiber and I have never had a service related problem with any of them. Getting them installed and working is a MAJOR headache, but I have never had a reliability issue with them. That said, I insist on, at least, one copper POTS as a backup. 911 calls have to complete, no matter what the circumstance.

The next most reliable is HDSL and I think that's only because their relatively close to the CO. Rain, snow, backhoes and birds with diarrhea will cause problems on copper T-1. Of course, a fiber T-1 doesn't stand a chance with a backhoe, either, but, around here, Verizon has well marked the fiber pathways so it's rare that I see a fiber outage.

Rcaman

A circuit that is guaranteed to work 99% of the time can be out of service one hour every 4 days. Doesn't sound reliable to me.

To clarify, actual verbiage is 99.99% in most cases. Does anyone guarantee 100%?

I can guarantee 100% 100% of the time you will be billed, as for service - thats negligible.