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

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...