FCC now planning "all-IP" phone transition [Telecom]

If you thought that the digital TV transition, with its billion-dollar coupon program for converter boxes, was a migration nightmare, wait until it's time for the phone system to dump its legacy circuit-switched system and move to an all-IP communications network. That day could be coming sooner than you think; the Federal Communications Commission has just requested comment on its planning for the transition.

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John

Reply to
John Mayson
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What would be costs of such a transition? How much conversion would be required in the local loop plant, especially in older areas? How much in central offices such as in the cable vault to convert analog loop lines to IP digital?

FIOS requires every subscriber to provide their own power and have a battery backup. Right there is an additional cost to the subscriber.

While I'd say the number of traditional Western Electric sets (ie

2500, 2554) out there aren't too many, there is a huge number of more modern analog sets that are not compatible with IP.

Unlike broadcast television, where most subscribers were already using cable TV delivery, not over the air, far more people will require converters. Further, conversion will be a nuisance since commercial power would be needed.

Who is gonna pay for all that?

After that is done, what will the benefits be and who will be the beneficiaries.

I can't help but suspect, given tech history, ordinary subscribers will pay more and get less. Specialized subscribers who will benefit will lobby hard for this.

Reply to
hancock4

Recently AT&T asked the FCC to set a date to transition completely off traditional "switched technology" telephone networking, in favor of packet switched (internet-style) networking. [AT&T claimed that] maintaining two parallel networks that accomplish essentially the same thing was wasteful and uneconomical, and this has caused quite a bit of posts, especially between collectors and users of 'old telephone technology' such as me.

At the time I read about AT&T's request I did not realize the petition was for the technology in and between central offices, and not a bid to remove all copper twisted pair out to consumer's premises. However with the ever-increasing amount of fiber either to premises or to centralized communication near the end users, my [concerns] remain the same.

Right now I have home [phone] service [from] my CATV provider, and they give me an RJ11 "dial tone source" jack, that I merely connected into my existing house IW wiring after lifting the IWs from my landline protector at the side of my house. So if the outside plant copper were to go away, or even the CO switch located a block from my house were to change, big deal. I'm already not using them (at least, not for my local loop.)

Also, as far as I can tell, POTS stuff is pretty much copper ONLY from the last CO to the houses, and in many cases not all that way either as fiber is pushed closer and closer to the customer premises, or directly into them in some cases. So if switched technology were to be phased out, AT&T would beef up their internet backbones, surplus dozens of backbone ESS switches and probably hundreds of local CO switches, and start to recover enough copper strung throughout the country to probably defray most of the transition costs.

And as it is now for me, over CATV Coax on the same feed that gives me my home internet network and cable tv transmissions, things work fine, right up to and including running it to my 555xbrd as it's one and only "trunk". So changing from 'switched technology' to 'packet based technology' does NOT mean the end of grandfathered analog (switched) telecommunications gear.

Those who have actually built their own outside plant may have another story (unless they get IP access way down the road where their "feed" interfaces with existing POTS cabling.)

The real losses:

  1. Transmission quality - MAYBE ...although quite frankly my home line is working as well (if not better) over CATV coax as it did w/traditional T&R copper back to the CO.

  1. Service during power outages and/or other disasters. Even if the future continues to have battery plants backed up by diesal generators in central offices, it won't be of much use to those who are wired up like me. BUT, even if they are backed up well in the central offices, how about the fiber feeds to local distribution units in the field? How much battery backup do those end-of-the-fiber boxes have with them? 6 hours? 12? Two years ago a transformer blew during a 110-115F heatwave, and it took the local power company 5 days to replace it and restore power to my house. If I had still been on T&R copper from the central office my home phones would have worked because (at least some of them) do not depend on local power. As it was, since I was off CATV coax and had a very small UPS to back it up, my home phone was dead about 3 hours into the commercial power outage. Fortunately it was not a wide area power grid disruption, so my cell phone still worked...

In a major earthquake, we'll be back [to] depending on ham radio operators, as I strongly doubt all those cell towers will remain operational...

Paul H.

Reply to
Paul Hoffman

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First they came for the NTSC televisions, and I did not speak out - because I was not an antique television collector.

They can have my analog phones when they take them from my cold, dead hands.

-- Dave Haber Massapequa Telephone, part of the global C*NET System C*NET 1-798-7619

Reply to
Dave Haber

Where does Verizon fit in all of this? Isn't today's at&t a relatively small company?

There are several issues in play here, some transparent to the home subscriber, some possibly of import.

First, today's telephone network is almost all digital even though most telephone sets are analog. Shortly after your analog signal leaves your telephone set the telephone company converts it to digital. This may be done at a line concentrator on a pole, at a converter box within or near your home (such as with VOIP), or at the central office.

The question then becomes what kind of digital format will be used to transmit the signal through the network. Again, that probably will be transparent to the user. The phone company can choose to make that signal very high fidelity if it wants, though it will most likely keep it at the 4 KHz it has been for years for land line and whatever miserly bandwidth it gives up for cell phones.

That is, if the phone company were to use a new kind packet switching, it could make it high fidelity or crap, but it could do so now with its existing transmission.

Second, we must remember the real difference between fibre and copper (and coax) is capacity. If they replace your copper line with coax or fibre there is no reason your home telephone set _has_ to change.

As far as I know, other than Touch Tone and fancy features, a telephone set today is functionally exactly the same as a 1938 telephone set (300 set with F handset). A 1938 set works fine today and a modern set would work fine on the 1938 network (except for Touch Tone and some sets offer pulse as an switchable option).

To me, a big change _may_ come where the subscriber's individual telephone set will do the analog-digital conversion and so emit digital signals. It likely will use a new carrier-signal and ringing current instead of the 48V DC and 90V AC 20 Hz used now. But at that point almost all telephone sets will be obsolete. Subscribers may have to buy adapters just as rabit ear TV owners had to do. (I suppose some business sets are digital now.)

As electronics have gotten so cheap, conversion to a uniform standard isn't as important as it once was. For instance, Amtrak's Northeast Corridor is powered by ancient 25 Hz current. Years ago there was consideration to convert this to modern 60 Hz current but it isn't as big an issue as in the past, certainly not one to justify the cost of conversion. They're upgrading the power supply but keeping it at 25 Hz.

I'm not sure the at&t claim (it's lower case now, right?) of parallel networks being a pain is correct. It's digital signals using a protocol. When we make a telephone call, we do not get dedicated use of a given digital line between two points. Rather, our digital stream is multiplexed with lots of other digital streams over a high- bandwidth high capacity trunk. Obviously the terminal equipment has to be able to separate down individual calls, but that's what computers do.

I'm not sure the above is accurate. Reclaiming copper is labor intensive, and copper can multiplex now. Going to fibre is irrelevent to the switching technology.

I'm not sure there is a separate _physical_ "internet backbone" from the switched network and the private line network. To make good use of economies of scale, they simply electronically divide up various high-volume trunks as needed for various services. That is, it's a _logical_ division. I strongly doubt it's something like the public network runs along old US 1 while the internet backbone runs along I-95.

If i'm not getting this correctly perhaps someone could correct me in layman's terms.

Since you're using a "new" technology of CATV, it damned better be a superior transmission and service quality than what you had before. (Several cable users have complained to me about service qualtiy, though. However, they like the lower price.)

"Competition" has been the big mantra driving public policy before and after Divesture. But competition works in multiple ways and not necessarily in the public interest. For instance, in the regulated world, telephone and power utilities generally had very strong networks and recovery labor forces since the rate base had no choice but to pay for it and the PUCs encouraged it.

But with competition, consumers have fled from high cost to low cost, not worrying about recovery during troubles. In the advent of power competition, many electric companies have become too lean and needed much longer time to repair storm damage, plus had less redundancy and would fail more easily. (Retire power people told me they were very glad to get out since the modern world is skimpy and ugly).

That has already happened to the landline telephone business. Support is harder to get; repairs take longer. I'm afraid those expensive C.O. diesel generators will be scrapped because the baby bells will figure, "Hey, the other guys are stealing our customers by lower price, so we have to become lean, too". I strongly doubt the cable companies have diesel generators and huge batteries in their terminal rooms.

[public replies, please]
Reply to
hancock4

AT&T: Current assets $265 *Billion* 2008 gross revenues $124 *Billion*. (operating expenses $100 Billion) 2008 gross profit (revenues less expenses) $24 Billion

Doesn't sound like a 'small' company to me. Others may have a different opinion.

False to fact.

One _does_ get dedicated use of a given digital 'circuit' between the two points. This is what the 'connection set-up' when a call is placed establishes It may well be time-division-multiplexed (e.g. a DS-0 in a DS-1) on a common physical connection, but the full capacity of that circuit *IS* dedicated for your use, regardless of how much, or how little, use you actually make of it during the call. That connection is _yours_, for your exclusive use, until the 'connection tear-down' at the end of the call.

This is why the telco backbone _is_ referenced as a 'circuit-switched' architecture, not a 'packet-switched' one.

Reply to
Robert Bonomi

On Tue, 05 Jan 2010 22:01:37 -0600, Robert Bonomi wrote: .......

In Australia, the major telco has been using VoIP as a backbone for business voice traffic for quite a while now. No one has noticed much difference.

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-- Regards, David.

David Clayton Melbourne, Victoria, Australia. Knowledge is a measure of how many answers you have, intelligence is a measure of how many questions you have.

Reply to
David Clayton

The question was _relative_ to other carriers, such as Verizon. And isn't it properly spelled as "at&t"?

Nope. It's true to life.

Actually, certain multiplexing techniques, such as on an underseas cable, do NOT dedicate the full capacity of an assigned channel.

You snipped some key explanations in my earlier post.

The "full capacity of a 'circuit'" these days is enormous, far more than one needs for a voice telephone conversation. That's why we have 'multiplexing' which is a way for multiple conversations to share an individual circuit.

There are many different ways to multiplex multiple telephone conversations or data streams on an individual circuit. The particular technique chosen does not normally matter to the individual caller. What matters is the assigned bandwidth--that determines the quality of the connection.

When an audio sound is digitized for transmission, it could be a high or low quality. (Will it sound like a telephone voice or CD voice?) Certain telephone users need higher bandwidth and pay more to get it. For instance, a radio show transmitted over phones needs a higher quality sound so a better connection is provided. Television needs a much higher bandwidth for the video signal and better sound, so an even bigger connection is provided. (Not as much TV and radio use the phone network these days; this is just to show an example to illustrate the point.)

"Packet switching" is just another multiplex method; a way to stuff multiple conversations or data streams through a single big pipe. Once again, when an audio sound is digitized for transmission, it could be a high or low quality. They can make packet switching very high quality or very low quality as they deem fit.

Another poster describes good quality packet switching in Australia.

What will matter is how the packets are defined, just as the digital sampling rate varies.

***** Moderator's Note *****

This is a complicated subject: let's try to shed more light than heat, OK?

Bill Horne Moderator

Reply to
hancock4

The A-D conversion can be done by digital loop carrier, but I've never seen a DLC small enough to be mounted on a pole. Do the such things exist?

As for doing it in a "converter box within or near your home," the old question remains: how do you power it? With VOIP, the customer understands that he/she must provide the power, including battery backup power if desired. But if the telco provides the conversion, who provides the power?

Except that somebody -- either the subscriber or the telco -- still has to provide the operating power for the phone, possibly including backup batteries. How do you propose to power it?

True, including the requirement that the copper pair that connects it to the network also provides operating power. > A 1938 set works fine today and a modern set would work fine > on the 1938 network (except for Touch Tone and some sets offer > pulse as an switchable option).

They even require the same kind of power to function.

What kind of adapter? A D-A converter that includes a power supply and a ring generator?

They are. They operate on local power and may or may not have backup batteries. Numerous small business systems are digital, but if you dial 9 to get an outside line, you get an analog subscriber line. It's usually ground start, as opposed to loop start, but it's still an analog loop. DC voltage and ringing voltage are superimposed on the loop for signaling purposes, but the customer's phone system itself is powered locally.

Hoffman continued:

Or the last DLC.

AT&T could recover pole-mounted cables relatively easily (so could scavengers). Recovering buried cables, particularly in urban neighborhoods, would be far more expensive. I suspect the cost of recovering it would exceed its value, even at today's copper prices.

Diesel generators, yes; huge batteries, no. Most of the headend equipment that cable companies use is powered from 115 VAC, not -48 VDC, so DC is not needed for normal operations. Batteries are needed only in UPSs that keep essential equipment running until the generator fires up.

Neal McLain

Reply to
Neal McLain

Sure. A decade ago the local telco had pole mounted boxes that broke out a T1 into 24 POTS circuits. They were line powered, so the POTS voltages were somewhat lower than normal. Their engineer told me that he wanted to avoid equipment outside the CO that needed its own power.

I haven't checked to see what they do now, but since they offer DSL to nearly everyone, it must be something else.

R's, John

Reply to
John Levine

Good question.

For decades consumers just assumed the phone company would power their home telephones. Business telephone systems* usually needed commercial power, although some basic call ability continued with CO power if a direct line could be established.

But in the last decade cordless phones became very popular and consumers have to plug them in and depend on commercial power for them to work. Consumers were advised to keep at least one traditional wired phone for power failures. Likewise, consumers realize that cell phones have to be recharged with commercial power.

So, the idea of using commercial power to run a telephone isn't a strange idea to consumers anymore; they're used to it.

Consumers still will need to be educated that a backup battery is absolutely required for modern telephones. I believe Verizon's FIOS installation includes such a battery backup.

There is of course a slight cost in electricity consumers must pay for these phones; but I don't think it's something consumers think about. But all the rechargeable devices and modern electronic always-on devices do eat power that adds up.

I would expect new phones to come with power cords just as answering machines and cordless phones do now. FIOS devices may have a dedicated power source. Historically, business key systems plugged into an 120V outlet that was mounted for that purpose in the utility closet. (Older Princess and Trimline phones used an AC incandescent dial lamp and those required a plug and transformer; newer models used LEDs powered by the phone line. Interesting how we're going backward.)

True. If someone had a cordless phone and went back in time to 1938, they would plug it into a nearby 120V wall outlet (that most homes had) and would be in business. I don't think cordless phones use much current.

Probably.

Cable companies actually have diesel (or other fueled) generators? Those units are big and heavy, plus there is the fuel storage, and maintenance.

As an aside, these units need frequent testing. I've seen a lot of mission critical places go dark when they were testing their generators--the control circuitry failed to make a proper transition.

*Old PBXs sometimes had a hand crank to run the ringing signal in the event of a power failure having used one, they're not that easy to turn and get tiring pretty quickly. An alternative was just connecting extensions to outside lines directly as done for night connections.
Reply to
hancock4

Well, AT&T revenues are roughly -30% smaller than Verizon, Inc. and assets are $-63 billion smaller. and that's after Verizon acquired GTE and AlTel.

FALSE TO FACT.

Extra compression is applied, such that the bandwidth demand for a 'voice channel' is smaller, *BUT* that (reduced) channel bandwidth _is_ reserved for the exclusive use of that voice channel.

This is an absolute necessity given the design requirement that _every_ 'established' call be able to actually _use_ their 'voice channel' at all times while the call is 'connected'.

To misquote Clinton, "that depends on what you mean by 'circuit'".

With the possible exception of the proverbial "last mile" every physical circuit contains a large number of 'logical' circuits.

*EVERY* such 'logical circuit' has certain resources assigned for it's _exclusive_ use.

Even on an OC-192, each (logical) DS-0 is guaranteed it's particular stream of bits.

There are a surprisingly _small_ number of ways to do multiplexing. Time-division Frequency-division and 'statistical' about cover it.

Time-division and frequency division are both 'synchronous' techniques, except for a small (fixed!) amount of additional latency, the recovered signal is an exact duplicate of the original.

Statistical multiplexing (of which packet-switching is a special-case subset) is an asynchronous methodology. The bits will come back out in the same order, but that's the extent of the 'guarantee' On any given 'channel' one data block may have had much more (or less) latency than the previous block. There's no way to know, nor to predict in advance, when this happens, nor 'how bad it will be' when it does happen. The advantage of 'stat muxing' is that you _can_ 'over-subscribe' the capacity of the composite circuit -- e.g. put 16

9600 baud terminals on a single 19,200 baud trunk. As long as they are _lightly_ used, it works fine. BUT if they're all beating up on the connection, they're each only going to see about 1200 baud performance. And it will be 'bursty', a bunch of data will come in fast, then there will be a long pause until the next burst of data.

It -can- matter a great deal if one is trying to do something other than 'talk' on the line. Modems, Fax machines, TDD devices, voice-recognition systems (e.g., IVR) even Touch-Tone(r) control of remote devices -- these can all be adversely affected by the use of an 'asynchronous' multiplexing technique.

'Audio quality' of the connection is irrelevant to the _guaranteed_ availability_, END-TO-END, of the bandwidth (and other resources) required to handle the particular connection.,

To have a _guaranteed_ end-to-end bandwidth, 'circuit switched' technology is required. You have to build a 'virtual circuit' (a locked-down routing decision at every decision point) from end to end, with a committed circuit information rate on every link, and through every switching device.

If one does -not- do that, one cannot guarantee that the resources required by the connection (phone call) will be available at all times during the call.

Every device, and every path segment, does have a fixed upper bound on the amount of traffic it can handle. Any attempt (regardless of whether it is packet-switched, or circuit-switched, technology) to force 'n+1' things through a resource that can only handle 'n' is doomed to failure.

The _critical_ difference between packet-switching, and circuit-switching, in *that* regard is that a circuit-switched network can tell you _at_ _call_ _initiation_ (aka 'call set-up') that the required resources are not presently available (e.g. a 'fast busy'). Also -- assuming the set-up phase completes successfully -- a circuit-switched network _guarantees_ the availability of that level of resources for your use until call completion (aka circuit tear-down time).

A packet-switched network has no 'set up' and 'tear down' phases, and, therefore cannot tell you whether or not any particular _level_ of resources is available at the time you start sending. Nor can it guarantee that the necessary level of resources will be available for the entire duration of the 'call'.

FALSE TO FACT.

"Packet switching" means that the 'routing' for each/every data block is determined _as_ _that_ _data_ _block_ _is_ _processed_. There is no guarantee that successive blocks between the same source and destination will take the same path at any point. And, as a result, there is no guarantee that the blocks will arrive in the same order as sent. There is also no guarantee that there will be 'room' for those blocks on any given physical carrier segment when those blocks arrive.

In contrast, 'circuit switching' figures out all the routing decisions at the time of call set-up; it _is_ guaranteed that all packets will traverse the same path, and will arrive in the same order as sent (if they arrive at all, that is). It is also guaranteed that there _is_ space available on each physical link between the source and destination for every packet that is sent as part of the call.

These are the _critical_ differences between 'circuit switched' and 'packet switched' technology -

'Circuit swished' technology:

  • 'Sets up' a connection (on demand) and allocates resources to it, _before_ it can be used. * Releases those allocated resources _only_ on call tear-down. * _All_ the routing decisions are made at call set-up time. *guaranteeing* a (fixed) path is available, and that all blocks of data between the two endpoints will take that _specific_ path. * Required bandwidth is _reserved_ for that 'virtual circuit', =until. the virtual circuit is 'torn down', at call completion. + These last two points, incidentally, guarantee a constant transit time, a fixed amount of latency, fixed 'jitter', as well as _stable_ values for a number of other 'important' communications parameters. * "Lost' data blocks are immediately detectable -- arrival of any block without the arrival of the preceeding bloc is proof that the preceeding block was lost.

'Packet-switched' technology:

  • Has no concept of a 'connection' within the network. Endpoints may agree among themselves, that certain blocks of data are to be treated as part of a common stream, but it is _only_ the end-points that are aware of that relationship between those data blocks. * Never 'reserves' any resources for the specific use of any particular connection. Thus, cannot 'guarantee' availability for anyone, at any given time. * Therefore, never needs to 'release' any resources. * _All_ routing decisions are made _at_the_time_ =each= data block arrives at each routing point. There is no guarantee that subsequent data blocks will be routed the same way at _any_ routing decision point. * There is *NO* guarantee that any path between the endpoints _is_ available at the time any data block is sent. * There is no guarantee that the path that was available for the prior data block is _still_ available for the current data block. * There is no way for any intermediate point to *autonomously* notify _either_ end-point that a required link in the path is 'full', has errors, or has completely stopped working. * There is no guarantee that the data blocks will arrive at the destination in the same sequence that they left the origin. * Detecting data blocs that have actually gotten "lost" in route, as opposed to merely 'delayed' is virtually impossible.`

Some_ of the characteristics of a circuit-switched technology CAN be built, and relatively easily, on top of a packet-switched one. Some of the more critical ones -- end-to-end _guaranteed_ bandwidth for the lifetime of the 'connection', timely detection of 'lost' data, and autonomous notification to the endpoints -- are *very* difficult to add.

Again, quality of the 'audio signal' is irrelevant, and IMMATERIAL, to the quality of the communications _network_. Network 'quality' is based on primary considerations of the reliability, and consistency of behavior of the infrastructure, not the quality of '[what] passes through it'.

One can have a 'high quality' network, carrying a very low quality audio signal, and one can try to push 'high quality audio' across a low quality network.

Reply to
Robert Bonomi

In a message dated 1/7/2010 6:20:17 PM Central Standard Time, snipped-for-privacy@bbs.cpcn.com writes

TV stations are warning with the sub-Zero cold expected to take your cell phone car charger with you if you go out.

Telcos used to run them, usually every Wednesday at 8 a.m. amd actually transfer the power and run on auziliary power for an hour so to make suwre the generator is working and so is the transer. I wonder if they still do. Wes Leatherock snipped-for-privacy@aol.com snipped-for-privacy@yahoo.com

Reply to
wesrock

I was charged with designing the power redundancy for the Central Voter Registration System here in RI. I specified an APC Symmetra with a minimum of 15 minute backup time (Reality gave us 45 minutes), backed up by a 125kW natural gas fired generator that spooled up within 10 seconds. It had normal exercise routines that it would do, and once every quarter we'd do a full scale test. That involved going to the transfer panel, holding down a button for a set interval and you'd see everything transition to the generator.

Reply to
T

Verizon is trying to sell off their land-line operations. Up here in the Northwest they're planning on getting Frontier to take it all over.

Reply to
jmeissen
+--------------- | wrote: | > Actually, certain multiplexing techniques, such as on an underseas | > cable, do NOT dedicate the full capacity of an assigned channel. | | FALSE TO FACT. | | Extra compression is applied, such that the bandwidth demand for a | 'voice channel' is smaller, *BUT* that (reduced) channel bandwidth | _is_ reserved for the exclusive use of that voice channel. | | This is an absolute necessity given the design requirement that | _every_ 'established' call be able to actually _use_ their 'voice | channel' at all times while the call is 'connected'. +---------------

(*sigh*) How quickly they forget... :-(

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...time-assignment speech interpolation (TASI) is an analog technique used on certain long transmission links to increase voice-transmission capacity.

TASI works by switching additional users onto any channel temporarily idled because an original user has stopped speaking. When the original user resumes speaking, that user will, in turn, be switched to any channel that happens to be idle. The speech detector function is called voice activity detection. ... TASI was invented by Bell Labs in the 1960s to increase the capacity of Transatlantic telephone cables. It was one of their first applications requiring electronic switching of voice circuits.

Later Digital Circuit Multiplication Equipment included TASI as a feature, not as distinct hardware. ...

Other sources note that the TASI plan was actually first published in 1959 [Bullington K, Fraser JM, "Engineering Aspects of TASI", BSTJ, 38:353-364 (1950)], not "in the 1960s", but that's a minor detail.

In any case, stealing bandwidth from putatively "circuit-switched" voice calls is now more than a half-century old, and is still used in applications where the available bit-rate is constrained (e.g. VSATs).

-Rob

----- Rob Warnock

627 26th Avenue San Mateo, CA 94403 (650)572-2607
Reply to
Rob Warnock

Nonsense. The original packet-switched networks were all connection-oriented.

Again, nonsense. Numerous mechanisms exist, and have been deployed, for resource reservation on packet networks.

False.

You seem to be confusing the service you can buy from your consumer-grade ISP for $39.95 a month with the definition of what a packet-switched network is. It isn't so.

Complete malarkey. Even your consumer-grade ISP can and does do that.

Some network technologies provide such guarantees; others don't. Take off your telco blinders, please.

-GAWollman

Reply to
Garrett Wollman

The last 2 times that Verizon sold land line to other companies they crashed, stay tuned for another crash. At least the Northwest is in pretty good shape, but will Verizon leave enough money in the company to survive?

Reply to
Steven

I suggest Robert Bonomi also understand the difference between a datagram and and a virtual circuit as applied to packet switched networks.

David

Reply to
David

I saw a TASI installation in the underground AT&T Long Lines building in San Luis Obispo, CA in the 1970s. This was the mainland end of an undersea coaxial cable to Hawaii. The cable had vacuum tube amplifiers at the bottom of the ocean. TASI does seem to be a sort of analog packet switching and may suffer from the "pipe is full" problems of other packet switched or statistical multiplexed systems. I wonder how much it increased the capacity of the cable and how much capacity they had to hold in reserve to keep from cutting people off. I imagine a max increase is 100%.

Harold

Reply to
harold

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