Wikipedia:Reference desk/Archives/Computing/2018 April 25

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April 25

Having trouble accessing Forbes

When I try to access the website on my iPad via safari,all I get is a blank welcoming page: https://www.forbes.com/forbes/welcome/?toURL=https://www.forbes.com/sites/forbesagencycouncil/2018/02/08/three-best-practices-to-manage-your-online-identity/&refURL=https://www.google.ca/&referrer=https://www.google.ca/. I tried fixing the URL but it still does the same thing.

Try disabling all browser extensions and just use this URL: https://www.forbes.com/sites/forbesagencycouncil/2018/02/08/three-best-practices-to-manage-your-online-identity If that doesn't work, try a different web browser, such as Chrome or Firefox. TheMrP (talk) 00:26, 25 April 2018 (UTC)

Why two telephony networks, landline and cell-phone

Isn't the existence of a mobile and landline telephony network a waste of resources? Or does the cell tower connect to/need the landline network and cell-phones are just a kind of long range cordless phones? Are governments planning to deprecate landlines or, at least, not expand the network? --Hofhof (talk) 13:07, 25 April 2018 (UTC)

Land lines still work when there's a power outage; they're also usually much less expensive than cell packages. Matt Deres (talk) 13:15, 25 April 2018 (UTC)

Land lines work because there's a massive room full of lead-acid batteries in the telephone exchange. And that's there because regulators made the phone company have resilience during power outages (as the landline phones were an emergency lifeline service). This story discusses the regulatory environment in the US cellphone segment regarding power-fail resilience for mobile comms, now that cellular phones make the majority of emergency calls. These days, if a cell fails due to a power outage, that's a failure of regulation and infrastructure maintenance, not a real technical advantage of landlines. -- Finlay McWalter··–·Talk 13:54, 25 April 2018 (UTC)

And Matt's "expensive" is about cost to the end user, not necessarily the cost to install and maintain the network, which as Finlay says may be required by law. --69.159.62.113 (talk) 00:15, 26 April 2018 (UTC)

• You might be interested by reading more on leapfrogging - in developing countries, landlines and wired internet networks are mostly inexistant, and likely to remain so, because cell phone technology has taken over. I have no good reference to suggest, but at a first glance "The distributional effects of leapfrogging in mobile phones" by J James looks like a good article. Tigraan^{Click here to contact me} 14:26, 25 April 2018 (UTC)

Readers used to reliable cell phone service availability everywhere they go might want to look at the map at https://www.telstra.com.au/coverage-networks/our-coverage . It shows how much of my country, Australia, is covered by cell phone service. Many people in those more remote areas (the gray bits) still depend on landlines. HiLo48 (talk) 01:12, 26 April 2018 (UTC)

Yes it is a waste of resources. The second network was car phone network which was very low capacity. The third and fourth networks 1G and satellite terminals started around the same time. 1G made car phones obsolete so there are three telephony networks now. CT2 worked like a cordless phone when you were at home and you could make only outgoing calls away from your basestation at home.
Sleigh (talk) 08:42, 26 April 2018 (UTC)

There's the matter of sunk costs. Building a landline network requires a large investment, but as most of the cables of the current network were already in place before the breakthrough of mobile telephony (about 20 years ago), that investment is irrelevant in western countries (but not in developing countries). But wired networks are still being rolled out in western countries, in the form of fibre to the premises. Whether it's because it can use optical frequencies, whereas wireless is stuck to radio, or because there are fewer devices per cable than there are devices per base station in wireless systems, wired has higher capacity than wireless. PiusImpavidus (talk) 09:17, 26 April 2018 (UTC)

Landlines almost never fail. In my county a few years ago, two people died stuck in a home elevator. They were unable to call for help. A landline is good for that use. With other things, you could be at risk if the power goes out, the internet is down, there is an error with the router, etc. Bubba73 ^{You talkin' to me?} 19:23, 26 April 2018 (UTC)

When I worked in the telecom industry in the early 2000's, pretty much everything past the MTSO (where the cell towers connected to) was on the same network as the landlines. I'm not sure how true that still is today though, since I've been hearing about mobile networks migrating to VOIP over the last few years. Random character sequence (talk) 21:00, 26 April 2018 (UTC)

• There are three [sic] networks, now migrating to one.

Originally there was one (voice phone) network, the PSTN (Public switched telephone network). There were several other networks too (one older) covering things like telegraphy, telex, leased lines, whole private voice networks for large companies and government. In the 1960s, the first real data network began with PSS, a packet-switched network. For a decade or two, this distinction barely mattered. There was no network for car phones (pre-cellular), same as there was no network for fax machines - they were just instruments switched through the PSTN like any other phone (a few business radio networks used leased lines too).

In the late '70s / early '80s, the PSTN was converting its large trunks to digital multiplexing, to fit more calls down one piece of copper (this had been done for years with analogue multiplexing).

In the mid-'80s the first cellular phone networks appeared (car and handset are identical). These ran on a mixture of the PSTN between the MSC [sic] (a telephone exchange for mobiles) and dedicated connections to the base stations. With the development of GSM, such dedicated connections were developed to the A_bis standard, which allowed a series of BTS (base stations) to be daisy-chained onto a single BSC (Base station controller). As BTS are often remote (and remote stations are low-traffic, which permits more of them on a single A_bis) then these could use point-to-point microwave links (why rural cellphone towers may also have horizontal drum antennae visible). So the connection from the radio to the MSC by the A and A_bis interfaces is "cellphone network" and this includes the switching of a moving phone between cells, but the long-haul links around the country are still the same PSTN.

In the '90s, the internet becomes important. Data is now moving around a single cloud-like internet, not just dedicated point-to-point links. As telephony is also digital (anywhere beyond the local telephone exchange) then these signals start to get mixed on the high-bandwidth trunk routes. It's significant here that it's cost-effective to lay a new (expensive) trunk cable, provided that there's traffic to justify it. However it's very expensive to lay the huge number of local loop cables from the exchange to each telephone, and each of these only generates a small revenue. In developing nations (notably South Africa and South East Asia), there's a 'leapfrogging' effect where mobile networks are built as the first widespread phone service, often linked by microwave (facilitated by long distances and low call volumes). The traditional model of copper cables to houses and local exchanges just doesn't happen - customers go straight to mobile phones as their first phones.

From 2000, the web drives huge volumes in internet volume, and in local customer internet use. Some countries (notably Germany) go for ISDN, which puts a digital connection into the home. By 2010 though we see broadband and huge demands for bandwidth. The internet between large data centres is carried by the same multiplexed trunk cables as are carrying the PSTN voice traffic, but there's a logical distinction between them.

We now have three major public networks: PSTN, internet data and mobile (A and A_bis), yet these are largely logical networks and they share much of the trunk network. However there is some duplication, and more importantly it's carrying packet-switched data over what grew out of a voice circuit-switched network. So operators like BT are moving to their 21CN architecture. This is primarily a data network, carrying internet traffic by the TCP/IPv6 protocols, and any circuit-switched voice traffic is carried on top of this. It's the high volume data (pr0n and Netflix) which defines the architecture of this next generation, no longer voice calls over landline phones. Andy Dingley (talk) 23:12, 26 April 2018 (UTC)

So, to summarize. The traditional telephone networks now largely survive as the last mile (local loop) between the customer and the station. However they are still important as they can provide provide reliable broadband services with data rates up to 100 Mbits/s over the twisted pair land line (ADSL/VDSL). This is impossible to achieve with any wireless technology. The only conceivable replacement is Fiber to the Home. This is actually a reason while developed nations have better and faster home internet connections. Ruslik_Zero 08:19, 28 April 2018 (UTC)

I wonder how long the lead-acid storage batteries at a phone exchange could keep the system working without AC power. I was in charge of connecting new power cables into a telephone exchange years ago. It had the aforementioned batteries, as well as a generator which would run when the utility power was shut down for the work, but the phone company brought in a second backup generator, and said that if their regular generator failed the batteries would not maintain operation "very long." Edison (talk) 02:00, 29 April 2018 (UTC)

This is likely to vary a lot from country to country. In NZ, it isn't uncommon that exchanges will have a generator on site [1] [2] (some of the discussion in the second link may be of particular interest to anyone wanting to know about these things). It seems to be implied this means the battery backup tended to not last so long. According go the second discussion, exchanges without generators may be up to 4 days. They are designed so portable generators will be used if needed, although this may be difficult in a large scale emergency. (Although there may also be other problems with the network then.) Also mentioned there and in the other sources is that the generators are supposed to be tested frequently so they are unlikely to fail. (However I'd imagine if it's expected an important site is going to be on generator power for a long time, it's possible another generator will be brought on site just in case especially since regular testing and maintenance could still miss problems particularly those which may only arise with extended use.)

Note as sort of hinted at there, a large part of NZ is no longer using the exchange but cabinets. These obviously don't have fixed generators. They are also designed for portable generators. This source claims battery backup on cabinets can be as little as 2 hours [3] but that sounds a little low to me. The 24 to 36 hours sounds a bit more plausible although possibly also a little high. (You can find other reports like [4] which mention short time frames but it's difficult to know if those are due to battery backups running out of power or other factors. Ditto unless the person checked, it's difficult to know if a cabinet 'lasting' for a longer time was solely from battery or also from a portable generator.)

According to [5], 8 hours is required for Ultra-Fast Broadband i.e. fibre to the home facilities. Of course since UFB does not provide power to the CPE, the CPE needs to also have some sort of backup. It was decided not to require any, so most people don't have any. An additional complication is that while the UFB ONT does have provision for a phone line, not all providers use it, some using their own SIP VOIP service provided for by the router or direct to digital phones. So these devices need backup too. And I've seen many question how likely is that many providers are likely to be at being able to provide a service if there is significant problems, especially given that many of these services aren't seen as that important. Of course one of the reasons why it wasn't required is that some felt the mobile network was a more likely backup since at least then most people don't need any 'backup' on the customer side in the short term since their mobile phone uses a battery for power. And these providers at least normally are much more experienced in handling outages.

This source claims cell sites are typically 4 to 12 hours [6]. All these suggest to me 2 hours or less for cabinets sounds a little short so may not be true.

BTW, I probably should mention that some people, although connected to a cabinet and using it for their xDSL service, are using the older POTS system in the exchange for their phone line. (For the avoidance of doubt, it's delivered over the same line to the customer.) This service is called baseband copper [7]. I don't quite understand if this service still works if the cabinet has no power but the exchange does. I would have thought no but this seems to suggest it does [8] but it could simply be misleading. There is some brief discussion of the issue here [9] but I wouldn't say it confirms that the implication is true.

Nil Einne (talk) 16:21, 29 April 2018 (UTC)

My home in Southern California has DSL and landline service, and every time we've had a power outage the landline has stayed active. Granted, I can't tell you how the cabinet is hooked up or whether it lost power. --47.146.63.87 (talk) 07:15, 30 April 2018 (UTC)