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1994-07-15
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Date: Wed, 15 Jun 94 11:01:02 CDT
From: bacameron@amoco.com (B. Cameron)
Message-Id: <9406151601.AA12481@psc1.chi.amoco.com>
To: nexus-chicago@mcs.com
Subject: Re: T1 and T3 connections
Here is a discussion about exactly *what* T1 & T3 connections are. I thought
it might be useful for people who don't know what these terms mean. I grabbed
this from alt.internet.access.wanted.
yippi
Brian
bacameron@amoco.com
In article 1p0@netcom.com, brettf@netcom.com (Brett Frankenberger) writes:
>yue@heron.Stanford.EDU (Kenneth C. Yue) writes:
>
>>I've heard about the terms T1 and T3 somewhere, but what exactly are
>>these connections? Is there a T2 connection? :-) Just curious.
>
>T1 = 1.544 MBps (Million bits per second, in this context, Million is
>10^6 (as opposed to 2^20)). But some of those bits are used for
>framing, so you only get 1.536MBps of actual data throughput on a
>normal circuit.
>
>T3 = 28 T1's ... so the data rate would be 1.536M * 28 ... the T1
>framing is claso carried, plus some additional T3 framing, so the
>actual bit rate would be 1.544M * 28 + <some_additional_overhead).
>
>There is a T2 ... it is 4 T1's ... actually, a T3 is 7 T2's ... but T2
>is rarely used ... I suppose in the 'old days', they had one
>multiplexer that took 4 T1's and made a T2, and then another that took
>7 T2's and made a T3 ... but nowadays, it is usually one box that takes
>28 T1's and makes a T3 ... (unless, of course, you are actually using
>the T3 as a data pipe, in which case thre is no T1 -> T3 multiplexer)
>....
>
>>I dial in to my school using a 14.4k modem, sometimes for a terminal
>>emulating session, sometimes for a SLIP session. However, I found
>>SLIP to be unbearably slow, especially when I run MacX. I am just
>>wondering if there exists any connection from home to Internet that
>>runs as fast as ethernet (maybe T1 or T3?) if money isn't a problem.
>
>Sure ... T3 would be difficult ... but T1 is very doable (it's not quite
>Ethernet - about 1/6th of an ethernet (or 1/3rd if you have heavy
>traffic both ways at the same time) ... but it's quite fast for most
>stuff) ... T1 is run over twisted pair, so you could have one to your
>house if you wanted ...
>
>>Let me emphasize that "I am just wondering"; I don't have the money
>>nor does my school support it if such "fast connection from home"
>>exists. Yeah, I know about ISDN, but it is still too slow. A related
>>question: can I connect to the Internet backbone directly with
>>ethernet from home (again assuming money isn't a problem)?
>
>We can save the debate of whether or not there really is a 'internet
>backbone' for another time ... but to answer your question ... must
>connections into the internet are via a 56Kbps circuit or a T1 circuit
>.... and it doesn't cost millions ... a few hundred a month to the telco
>for the leased T1 circuit, plus maybe a grand or two installation ...
>they don't lay new cable - they just use the existing twisted pair,
>although they have to install repeaters along it if you are too far
>from the central office.
>
>> Maybe I
>>have to spend millions just to install the cables? :-) Is this
>>technically possible, or is this just a question of cost? Hmm, come
>>to think of it, what is the Internet backbone? I always think that my
>>school (Stanford U.) is part of the Internet backbone because it is
>>the main location of BARRNET, which, I think is part of the Internet
>>backbone.
>
>There really is no backbone, although some would argue that the NSFNet
>T3 network is the backbone, since it is the fastest network ...
>
>All you have now is many networks that are interconnected ... some are
>larger than others ... my company has a T1 connection into 'the
>internet' so technically we are just as much a part of the internet as
>anyone else, except that we don't exchange routing information and we
>don't sell connections to anyone else ... what is generally though of
>as the backbone is BARRNet, CIX, NSFNet, etc., that are large networks,
>and they interconnect with each other, excchange routing information,
>etc. Then you have the intermediates like NetCom, UUNet, PSI ... that
>are really getting as big as the traditional backbone sites ...
>
>> Now some of you maybe able to explain to me how all the
>>LANs of Internet connected together; they can't be all hooked up using
>>ethernet, can they? Maybe using T1 and T3 (which I still don't know
>>what they are and if they have higher bandwidth than ethernet's
>>10Mbps)?
>
>Most connections are T1 ... sometimes multiple paraller T1s are used
>.... NSFNet uses a T3 backbone ... some other providers may also have T3
>now ... I don't know ... (SprintLink comes to mind - sprint would
>certainly have the bandwidth available) ...
>
>>BTW, I always wonder why people call a 14.4k modem a high
>>speed (only 0.0144Mbps) modem. :-) I don't understand why some people
>>are excited about the V.34 standard (28.8K = 0.0288Mbps, with V.42bis
>>compression 115.2K = 0.1152Mbps which is only 1% of ethernet speed)
>>either.
>
>It's all relative ... it's pretty damn fast compared to 300bps :)
>
>> Last question: does information superhighway mean ethernet
>>speed (or above) connection to each home? :-) Or am I just dreaming?
>>Again, is this technically possible or a question of cost?
>
>The information superhighway is a meaningless buzzword thrown around by
>politicians.
>--
>
> - Brett (brettf@netcom.com)
>
>------------------------------------------------------------------------------
> ... Coming soon to a | Brett Frankenberger
>..sig near you ... a Humorous Quote ... | brettf@netcom.com
>