fataldata

Just a curious question we've been bouncing around here. My suggestion was that a DS1 is a standard and a T1 is the product from the Phone Co. that fits the DS1 specification.

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Cephas

The answer to this depends on which way you came up. From my perspective (also the standard Lucent/Avaya perspective btw) DS1 is the actual 1.54Mbs data stream. You then organize that DS1 data stream according to either T1 (24*56k) or PRI (23b+1d) protocols.

In the Nortel Universe, the actual data stream is commonly referred to as the T1, which can optionally be enhanced with PRI protocol.

I find the Lucent version more logical, especially since a single b-channel is also known as a DS0, but hey that's the way I learned it :)

Cephas

PBXtech.info

 

pbxguy

i always thought DS1 23B+1D, and T1 is a straight pipe at 1.54Mbps
for example your pbx can have 1 DS1 - 23 channels and 1 signal channel
a T1 can let say connect a voicemail system at a different city...
......??????

Cephas

As I said, it depends on which way you came up. You've been taught a derivation of the standard Nortel/Bell viewpoint - identical except you're using the term DS1 (which most Nortel folks don't use at all) instead of PRI.

ISDN PRI is officially defined as 23b+d, usually the confusion comes in with T1 vs DS1. In the Lucent Avaya universe the DS1 is the 1.54Mbps pipe, and T1 protocol divides the bandwidth into 24 56k channels.

FYI you can use either T1 or PRI protocol to voice network two PBX's (depending on the PBX's of course). T1 will give you the one extra voice path, PRI will give you additional integration features (Qsig, H.450, etc)

Cephas

mforrence

I agree that it was how you were taught. My version is that a DS1 is the physical 1.544Meg pipe that can either be administered as a T1 or a PRI. The big difference in the voice world being that with T1 all of the call setup, connection and teardown signallling is done within the specific channel in question (i.e. if a call is being made on channel 7, then all signalling is done within channel 7.) With a PRI all of the signalling is done on the D channel - ususally channel 24, regardless of which channel will bear the call. Hence, if a call is to be made on channel 7, one end tells the other end all of the specifics via data packets on channel 24. That's how I teach my folks...

Mike

Cephas

Also my take. Always good to know that I'm not crazy ;)

Cephas

PBXtech.info

 

Relentless

I must add that terminology has always been a key part of technology. I have notice this also applies to the people who market technology. The marketing people copyright the terms they use to describe thier goods so that could explain why one company calls the glass half empty and the other half full.

bnkrptlsr

T-1 was the {GTE?} brand name for DS1 service.

Newton's 14th defines a DS1 as - Digital Service level 1.

I don't believe that there is any technical difference between a T1 and a DS1.

Cephas

Again depending on who you talk to. To most, a DS1 is simply a raw 1.544M data stream before you put any kind of protocol onto it. You then layer either T1 protocol (24*56k after bit robbing) or PRI protocol (23b+d) onto that stream in order to use it for voice.

The other camp argues that (since a DS1 stream with no protocol is useless for voice) it's birthed as a T1 and optionally converted to PRI - therefore they feel free to use the terms T1 and DS1 interchangebly.

Peter

mugambi

I view ds1 to imply digital signalling level one so it implies communication at 64kbits per second on a channel.T1 in my opinion implies a bit stream of 1.544Mb per second made 0f 23 b channels and an 8 Kb per second framing channel.
kind regards,
Mugambi.

MarkBellot

T1 is a DS1 on copper. If it comes in on copper it's a T1 and a DS1. If it comes in on fiber its a DS1.

oozenoz

Let me attempt to clean this up a bit - I used to work for one of the RBOCs and this has always been a source of confusion - even for people who worked there!

It does not matter if a carrier system is handling voice or data, or is being fractionalized at each end to carry a combination of the two, a T1 and a DS1 are the same thing - a physical transport facility carrying digital information at a 1.544 Mb/sec rate (when using framing - a T1 transports at 1.536 Mb/sec if no framing is used).

For a really good workup of the history of the T1, go here: http://www.dcbnet.com/notes/9611t1.html