T1 short-haul vs. long-haul

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1

I'm having a few questions about T1 line support in the US because I have to procure
some Router/Network hardware for US branches of a company (I am from Europe).

Normally in Europe when you order an E1 (G.703) connection the Telco delivers a
NTU (Network termination Unit) which normally is a (S)HDSL modem converting from
two-wire DSL to four-wire E1 electrical. The cable between the NTU and the Router
is normally very short, a few feet/meters.

o How is this normally done in the US by the Telcos for T1 lines?

o I assume the difference between T1 short-haul and long-haul is the cable length.
   But what is it used for? Is it still common to have long-haul T1 connections
   either within buildings or towards the central office of the Telco? Would I be
   fine with buying short-haul-only interfaces in any common scenario?

o What is "Wet T1 Capable"? What is it used for and who needs this?

o What else is important in dealings with US Telcos when ordering and using T1
   leased-line services?

Thanks for any input.

2

I'm having a few questions about T1 line support in the US because I have to procure
some Router/Network hardware for US branches of a company (I am from Europe).

Normally in Europe when you order an E1 (G.703) connection the Telco delivers a
NTU (Network termination Unit) which normally is a (S)HDSL modem converting from
two-wire DSL to four-wire E1 electrical. The cable between the NTU and the Router
is normally very short, a few feet/meters.

FYI I'm in the UK, this is not normal in all europe i guess.. they usually
present as unbalanced g703.

I dont know the answers to the below as I've never had a T1 in the US.. but I
think its important particularly when ordering in a market your not familiar
with to request the telco gives you a specification.

Even if you get the answers to the questions, dont assume this applies to all
circuits from all telcos in NA.. get the spec and confirm with your supplier
that you are getting what you expect. If you order the wrong thing it will cost
money..

Steve

3

Normally in Europe when you order an E1 (G.703) connection the Telco delivers a
NTU (Network termination Unit) which normally is a (S)HDSL modem converting from
two-wire DSL to four-wire E1 electrical. The cable between the NTU and the Router
is normally very short, a few feet/meters.

You can travel up to 655 ft. with a T1 cable from the NTU which the phone company will drop at your site. According to the letter of the specs, you are supposed to use "T1 cable" two 22AWG pairs individually shielded to prevent cross-talk. In practice, we have extended DMarcs up to 200-300 feet with regular Cat 3/4/5/6 cable and have never had any problems or out of spec. cross-talk as a result.

o How is this normally done in the US by the Telcos for T1 lines?

Same basic procedure, the telco will drop off a T1 smartjack (NTU) and you will plug your equipment into this box.

o I assume the difference between T1 short-haul and long-haul is the cable length.
  But what is it used for? Is it still common to have long-haul T1 connections
  either within buildings or towards the central office of the Telco? Would I be
  fine with buying short-haul-only interfaces in any common scenario?

Most modern equipment allows you to set the tx/rx gain on the DSU. We use mostly Cisco WIC-1DSU-T1 cards which fit into any 1600/1700/2600/3600/3700 router and provide better diagnostic capabilities than older standalone DSUs. It is also nice to have a single box rather than two power cables and a serial cable to worry about at a remote site.

o What is "Wet T1 Capable"? What is it used for and who needs this?

This is one of the "features" of the new WIC-1DSU-T1-V2. It seems that some DSUs can be powered by the telco remotely. In 15 years of working in communications, I've never seen this, but that doesn't mean it isn't used by some remote telco using old style T1 without HDSL or HDSL2 running over the line.

In almost all cases today, the T1 spam itself will be powered from the CO and the smartjack will convert 2 HDSL pairs or one HDSL2 pair to a T1 signal with distinct TX/RX pairs.

Does anyone else have more/better info?

o What else is important in dealings with US Telcos when ordering and using T1
  leased-line services?

If the service is available in your office areas, make sure to specify ESF framing and B8ZS encoding when you order the line. AMI is robbed bit signaling and will give you 24 56k channels instead of the 24 64k channels of B8ZS. The biggest problem is keeping after the carrier to actually install the circuit.

-Robert

Tellurian Networks - The Ultimate Internet Connection
http://www.tellurian.com | 888-TELLURIAN | 973-300-9211
"Good will, like a good name, is got by many actions, and lost by one." - Francis Jeffrey

4

This is a pretty good site that will answer most of your questions.

http://www.dcbnet.com/notes/9611t1.html

5

Robert Boyle wrote:

You can travel up to 655 ft. with a T1 cable from the NTU which the phone company will drop at your site. According to the letter of the specs, you are supposed to use "T1 cable" two 22AWG pairs individually shielded to prevent cross-talk. In practice, we have extended DMarcs up to 200-300 feet with regular Cat 3/4/5/6 cable and have never had any problems or out of spec. cross-talk as a result.

Kentrox used to have a white paper regarding demarcation extensions. They indicated that regular Cat 3/5 cable could likely be used to 1000-2000 feet, and individually-shielded twisted pair cable could go 6000 feet. As noted above, crosstalk is normally the critical factor in the distance "game".

pt

6

Robert Boyle wrote:

o What is "Wet T1 Capable"? What is it used for and who needs this?

This is one of the "features" of the new WIC-1DSU-T1-V2. It seems that some DSUs can be powered by the telco remotely. In 15 years of working in communications, I've never seen this, but that doesn't mean it isn't used by some remote telco using old style T1 without HDSL or HDSL2 running over the line.

In almost all cases today, the T1 spam itself will be powered from the CO and the smartjack will convert 2 HDSL pairs or one HDSL2 pair to a T1 signal with distinct TX/RX pairs.

Does anyone else have more/better info?

I found something on Cisco's website. However this seems only to be relevant
for 'long-haul' T1 connection when there is a four-wire going directly to the
central office (and possibly through repeaters).

Enabling Wetting Current on the WIC-1DSU-T1-V2 Card

  The WIC-1DSU-T1-V2 card supports wetting current. Wetting current is a small
  amount of electrical current (60 to 140 milliamps) sent from the central office
  to the card to prevent the corrosion of electrical contacts in the card's network
  connection.

  Wetting current may be enabled or disabled by the user. It is controlled by the
  placement of a jumper on connector J2 on the card. Figure5-6 shows the J2 connector
  and the jumper.

  The feature is enabled by connecting pins 1 and 2 of the J2 connector with a jumper.
  It is disabled either by removing the jumper or by connecting pins 2 and 3 of the
  J2 connector.

  The card is shipped with the jumper connecting pins 2 and 3 on the J2 connector,
  which disables the wetting current.

7

Ok, thanks for all the responses so far!

To summarize what I've gathered from the answers and reading through the
pointed out websites. For ordering T1 leased-line services I want the
following:

  o Router port with integrated CSU/DSU (instead of going T1->X.21->Router)
    [this was clear to me from the beginning]

  o Linecode B8ZS (because this gives clear channels with 64k rate)

  o Framing ESF (because this supports line diagnostics)

  o SmartJack with demarcation point in the office (or same floor) instead
    of the building entrance point

  o For lines that come with a SmartJack (aka HDSL2) I only need 'short-haul'
    T1 line (<655 feet, called DSX-1)

If I am unlucky the T1 gets delivered either directly or via repeaters as
four-wire service from the central office which makes it 'long-haul' T1 with
line segment lenth of up to 6,000 feet between repeaters (called DS-1).

The remaining question I have is how common are the two types of DSX-1
(short-haul with SmartJack) vs. DS-1 (long-haul directly to CO) lines?
Anyone with experience how this is being handled by the various Telcos?
Maybe percentages one type versus the other?

Are there major Telcos which clearly do not support the above settings?
To know who to avoid when procuring services.

8

Robert Boyle wrote:

Does anyone else have more/better info?

I've found this to be useful:

9

o SmartJack with demarcation point in the office (or same floor) instead
   of the building entrance point

You are not likely going to be able to control that,
it depends on how the install tech's day is going.
Strictly speaking, I believe they are supposed to put
it at the MPOE.

If I am unlucky the T1 gets delivered either directly or via repeaters as

You are worrying about this too much.

Order the T1 (ESF, B8ZS). As you order the circuit specify where you
want it to end up ("server room, 2nd floor") and that you want an extended
demarc (will cost extra).

AT install time, make sure someone is around to cajole the installer
into getting the NIU as close as you can to where your router will be.
The installer should test from the extended demarc (make sure they do).

Get a standard built-in T1 dsu like as been mentioned in previous posts.
Plug it into the extended demarc with an ethernet patch cable.

Now, even though I say to not worry, it is important to remember the
#1 lesson when dealing with telephone companies. I figure it is the
same all over the world, but just in case it isn't, I'll repeat it here:

  The telco is not your friend.

-mark

10

Andre:

If your distance for the short-haul is less than 10 miles or so (line-of-sight), I would go wireless. Reasons:
   a) you can get 10-30MBps on wireless vs. 1.4Mbps for T1.
   b) if you already have an antenna or other high-point, you can own the wireless network for about what the Telco would charge for a T-1 over about a year.

If you really want a wire circuit, for long-haul or short-haul, consider multiple xDSL connections. For example, under the current pricing we are seeing, we can install 8 ADSL circuits for about what one T-1 would cost. With 8 ADSLs, you would be getting >10 Mbps inbound and 2.8Mbps outbound -- equivalent to 8 inbound T-1s and 2 outbound T-1s for the same price as a single T-1.

Just some thoughts.

Jon Kibler

11

One word of caution on that - we had a customer who got 4 separate
1M/1.5M ADSL circuits - all to the same DSLAM. Ended up that the telco
had only provisioned that DSLAM with a single T1, and was apparently
unable to upgrade that, negating any advantage to the multiple DSL's.
It was a remote DSLAM, not in a CO, btw.

If you don't have a point to point circuit, make sure the upstream has
sufficient bandwidth to support what you are ordering.

** Reply to message from "Jon R. Kibler" <Jon.Kibler@aset.com> on Wed,
21 Jul 2004 12:44:46 -0400

12

Something to be careful on with ADSL is repair times. For example, with
Qwest there is a 4 hour guarenteed dispatch (24x7x365) on T1 circuits, and a
23 business hour dispatch on ADSL. YMMV with other telcos.

13

Jon R. Kibler wrote:

Andre:

If your distance for the short-haul is less than 10 miles or so

> (line-of-sight), I would go wireless. Reasons:

   a) you can get 10-30MBps on wireless vs. 1.4Mbps for T1.
   b) if you already have an antenna or other high-point, you can

> own the wireless network for about what the Telco would charge for

a T-1 over about a year.

If you really want a wire circuit, for long-haul or short-haul,

> consider multiple xDSL connections. For example, under the current

pricing we are seeing, we can install 8 ADSL circuits for about what
one T-1 would cost. With 8 ADSLs, you would be getting >10 Mbps inbound
and 2.8Mbps outbound -- equivalent to 8 inbound T-1s and 2 outbound T-1s
for the same price as a single T-1.

Sorry, I meant "short-haul" and "long-haul" in the electrical sense
for the length of the cable line between two devices speaking the T1
line format (B8ZS). Some documentation I have read refers the to the
two T1 types DSX-1 and DS-1 as short- and long-haul.

Going Wireless is not an option since the distance will be the same as
between major US cities. Going ADSL is not an option because of
reliablility issues and its 'hackish' implementation.

14

Another drawback is that, by their nature, ADSL circuits have a higher
latency than standard T1 service. So if this is something thats really
important, a "propper" T1 might be a better option.

Then there's that little problem of maintaining routing over 8
parallel links, etc.

15

I don't think standard ethernet pinouts are correct. You want a cable
with pins 1&2 on one twisted pair and 4&5 on another (7&8 for DDS 56K).

Correct has nothing to do with it.
Any straight-through cable will work just fine. It's just from the
jack to the equipment... and it's already been specified that the
extended demarc has been made to the place specified by the customer
(i.e., near the router).

If you're only going 14 feet (up a wall, across a ladder, down a rack)
then you can use silver satin, or just about any straight-through cable
you find on the floor or under the tiles or in the trunk of your car.

-mark

16

Yes, this is built around category 3 wiring, not 5. The specs are a
little more forgiving. Just grab any 'ole ethernet patch cord and hook
it up. Works flawlessly. Unless you're running between DSX pannels or
into another MUX, you never need to roll pairs on a T1 installation so
just wire straight through.

17

Order the T1 (ESF, B8ZS). As you order the circuit specify where you
want it to end up ("server room, 2nd floor") and that you want an extended
demarc (will cost extra).

AT install time, make sure someone is around to cajole the installer
into getting the NIU as close as you can to where your router will be.
The installer should test from the extended demarc (make sure they do).

I have had LEC's tell me that the extended DMARC is only warranted for 3
months after install. Any work to the extended DMARC will cost you after
that if the trouble is within the extended DMARC. I have had telco techs on
site flat out refuse to repair an extended DMARC or tell you that it has to
be scheduled and will take a week to schedule. Occasionally a friendly tech
will just fix it for you without charge so, YMMV.

Get a standard built-in T1 dsu like as been mentioned in previous posts.
Plug it into the extended demarc with an ethernet patch cable.

Now, even though I say to not worry, it is important to remember the
#1 lesson when dealing with telephone companies. I figure it is the
same all over the world, but just in case it isn't, I'll repeat it here:

  The telco is not your friend.

Indeed. But be nice to the techs, save the anger for their management.

John Bittenbender

P.S. Welcome to the States (at least virtually)

18

Date: Thu, 22 Jul 2004 00:43:59 -0400
From: John Bittenbender

From: Mark Kent

> The telco is not your friend.

Indeed. But be nice to the techs, save the anger for their
management.

Depending on the telco, craft may well be your friend. Although
SBC [mis]management has often made me seethe with anger, craft
has _always_ been very helpful and truthful.

Rule of thumb: The people who need a strong butt-chewing will
hide from you, shielded by subordinates and "meetings". The
visible people want to help; keep in mind what can happen when
they like you better than their own management.

YMMV, of course.

Eddy