Category Archives: Australian Telco

NBN where there are no roads?

Recently I took a week off work and went hiking around the Hawkesbury river in NSW.

This did not mean I stopped thinking about telecom.

There’s a lot of beautiful bushland and some fancy houses nestled into the area, a good chunk of which are not accessible by road at all, with the only way to access them being by boat or a long hike along a bush track.

So how on earth do they have NBN FTTH connections?

The answer, is submarine cables.

No fancy erbium-doped fiber amplifiers here though, just regular GPON laid on the riverbed.

Telstra / Telecom had previously laid a copper 100 pair (seemingly just regular gel filled cable directly on the riverbed without any protection) to service the area, and then aerial distribution along the tracks connecting the homes.

NBNco it seems opted for a slightly safer approach and used Protectorshell articulated pipe to protect the cables in the water / on the beaches.

Strange tree roots – NBN Articulated pipe on the left with the old copper 100 pair on the right

Once the cables land it’s back to regular NBN Aerial fiber runs, with DPUs on the power poles.

Apart from a few interesting catenary runs, and the fact there are no roads, once the fibre lands it’s very much a standard aerial NBN deployment.

There’s some great pics below from the supplier websites and local news site:

The role of the telecom Pillar & Cabinet in the Australian copper network

The gray telecom cabinets and pillars can be seen in suburbs across Australia, along rail corridors and even overseas.

But what do they do? What’s the difference between a pillar and a cabinet? Are they still used today? What’s inside? Why are they such an important part of the network?

What are they?

In a nutshell, they’re weatherproof (if properly cared for) enclosures for cross connecting (jumpering) cables.

This means that rather than doing the jumpering / cross connecting services in a dirty pit, a cabinet can be opened and the connection made quickly, in a clean, easily accessed, above ground housing.

They utilise a really clever design, that was the result of a competitive design process in the 1950s.

The schrader valve (bike valve) at the top allows the units to remain pressurized, this means in areas subject to flooding or for pressurised cables, the pillar remains water tight ( although the practice of sealing them again with air isn’t very common anymore).

When the aluminum top plate is unlocked and spun off the threaded fitting, the linesworker can unscrew the big nut on top, and lift up the cover, which locks open at the top, revealing the terminal units (either solder tag blocks or Krone blocks) inside the unit.

Jumpering a service is just a matter of opening up the cabinet, finding the A side and the B side, and running jumper wire through the built in cable management loops from one side to the other.

Each of the Terminal Units is a pre-terminated strip with a few meters of tail, which is fed through the base of the pillar to a nearby pit where they can join 1 to 1, out onto the underground cables, this means the units can be upgraded for additional capacity as needed.

While pressurised they are IP67 rated, but this only goes so far, check out this Telstra photo from Queensland Floods in 2010 from Taroom.
While pressurised they are IP67 rated, but this only goes so far, check out this Telstra photo from Queensland Floods in 2010 from Taroom.

Why were they needed?

  • Cables are expensive. We want to minimize excess unused pairs and use the existing pairs with maximum flexibility and efficacy
  • Opening joints costs time, money, and risks disturbing other services. We want to avoid opening joints
  • Troubleshooting is also time consuming and costly. A convenient test point is needed for isolating where in a cable a fault lies. (Main Cable, Distribution Cable, etc)
  • Easily use gas/air filled cables, without having to constantly open and reseal cables them to splice in new joins / jumpers

Cabinet vs Pillar

Cabinets and Pillars look the same, but the hints as to their purpose are in their location and what’s sprayed on them in faded paint.

Pillars are used for cross-connecting main cables (“M” Pair from the exchange) with distribution cables (to subscribers “O” pairs which run down the street to the pit in the front of your house).

Pillars are generally stenciled with a “P” and an number, or just the DA (Distribution Area) number.

Cabinet are a more flexible setup where you can connect cables between Pillars, akin to a root & branch approach.

Cabinets cross connect Main Cables (“M” pair to the exchange), with Branch Cables (“B” Pair from the Cabinet to Pillar) and Distribution cables (“O” pair to the customer).

Cabinets are stenciled with the prefix “CA” and a number, and exist in the 900 and 1800 pair variants, where one is just taller than the other.

The blue example is direct from the Main Cable to the Pillar, while Cabinets are used in the black example.

This means the distribution can go via a Cabinet to the Pillar to the Customer, as shown in the top /grey lines in the diagram.

  1. Exchange Main Cables (Main Cables / M-Pairs) go to Cabinets
  2. Cabinets connect to Pillars (Branch Cables / B-Pairs)
  3. Pillars connect (Distribution Cables / O-Pairs) that run through the pits outside houses
  4. Inside the Openable Joint in the pit is used to connect the lead in cable from a subscriber’s premises

Alternatively, the Cabinet may be bypassed and a direct cable goes between the Exchange and the Pillar, in that scenario it looks like the one show in blue lines on the diagram.

  1. Exchange Main Cables (Main Cables / M-Pairs) go to Pillar
  2. Pillars connect (Distribution Cables / O-Pairs) that run through the pits outside houses
  3. Inside the Openable Joint in the pit is used to connect the lead in cable from a subscriber’s premises
Display of 300, 900 and 1800 pair pillars and cabinets at the former Telstra Museum in Hawthorn

The Cabinet to Pillar model fell out of favor due to its increased complexity.
While it was cheaper to deploy the network using cabinets that cascaded down to feed pillars (you would only have to install enough cable for the “here and now” and could add additional Main & Branch cables as needed in a targeted manner) the move to outsourced lineswork for Telecom found that any increased complexity, led to additional operational cost that outweighed the capital savings

Use in the “Modern” Copper Customer Access Network

Pillars are still used in areas of Australia where NBNco have deployed Fibre to the Node.

NBN adds a row of X-Pairs (VDSL) and C-Pairs (Channel) to the pillar, which connect into the FTTN nodes themselves.

This means a customer with a traditional POTS line (M-Pair from the Exchange, C-Pair from the Cabinet to the Pillar, O-Pair from the Pillar to the Pit, and then the lead-in into their property) has the O-Pair and C-Pair buzzed out on the pillar, and then routed through the X-Pair and the C-Pair on the Node.

This puts the DSLAM in the Alcatel ISAM inline with the customer’s existing copper loop to the Exchange. The main cable comes from the exchange onto the M-Pair blocks in the Pillar, is jumpered onto the X-Pairs which go through the DSLAM, and come out as C-Pairs back onto the pillar. The C-Pair is then jumpered back to the Customer’s O-Pair and bingo, the FTTN cabinet is inline with the copper loop.

However as the PSTN services get dropped, the Main / M-Pair to the exchange can eventually be removed and the cables removed, meaning the connection just goes from the C pair for VDSL out into the O pair to the customer.

As part of the NBN migration some pillars were upgraded to include IDC / Punch Down blocks, and a rectangular version of the pillar was introduced.

NBN pillar

Oddly, these rectangular covers, do not have rectangular units inside, but rather cylindrical ones, just like the pillars of old.

This does fix the missing lids issue – The lid is captive, but I’m not sure what other design improvements this introduces – if anyone has the insight I’d be keen to hear it!

Information overload on NBN FTTH

At long last, more and more Australians are going to have access to fibre based access to the NBN, and this seemed like as good an excuse than any to take a deep dive into how NBN’s GPON based fibre services are delivered to homes.

We’ve looked at NBN FTTN architecture, and NBN FTTC architecture and Skymuster Satellite architecture, so now let’s talk about how FTTH actually looks.

Let’s start in your local exchange where you’ll likely find a Nokia (Well, probably Alcatel-Lucent branded) 7210 SAS-R access aggregation switch, which is where NBN’s transmission network ends, and the access network begins.

It in turn spits out a 10 gig interface to feed the Optical Line Terminal (OLT), which provides the GPON services, each port on the OLT is split out and can feed 32 subscribers.

In NBN’s case, Nokia (Alcatel-Lucent) 7302, and rather than calling it an OLT, they call it a “FAN” or “Fibre Access Node” – Seemingly because they like the word node.

Each of the Nokia 7302s has at least one NGLT-A line card, which has 8 GPON ports. Each of the 8 ports on these cards can service 32 customers, and is fed by 2x 10Gbps uplinks to two 7210 SAS-R aggregation switches.

The chassis supports up to 16 cards, 8 ports each, 32 subs per port, giving us 4096 subscribers per FAN.

In some areas, FANs/OLTs aren’t located in an exchange but rather in a street cabinet, called a Temporary Fibre Access Node – Although it seems they’re very permanent.

To support Greenfields sites where a FAN site has not yet been established a cabinetised OLT solution is deployed, known as a Temporary FAN (TFAN).

In reality, each port on the OLT/FAN goes out Distribution Fibre Network or DFN which links the ports on the OLTs to a distribution cabinet in the street, known as as a Fibre Distribution Hub, or FDH.

If you look in FTTH areas, you’ll see the FDH cabinets.
The FDH is essentially a roadside optical distribution frame, used to cross connect cables from the Distribution Fibre Network (DFN) to the Local Fibre Network (LFN), and in a way, you can think of it as the GPON equivalent of a pillar, except this is where we have our optical splitters.

Remember when we were talking about the FAN/OLT how one port could serve 32 subscribers? We do that with a splitter, that takes one fibre from the DFN that runs to the FAN, and gives us 32 fibres we can could connect to an ONT onto to get service.

The FDH cabinets are made by Corning (OptiTect 576 fibre pad mounted cabinets) and you can see in the top right the Aqua cables go to the Distribution Fibre Network, and hanging below it on the right are the optical splitters themselves, which split the one fibre to the FAN into 32 fibres each on SC connectors.

These are then patched to the Local Fibre Network on the left hand side of the cabinet, where there’s up to 576 ports running across the suburb, and a “Parking” panel at the bottom where the unused ports from the splitter can be left until you patch the to the DFN ports above.

The FDH cabinets also offer “passthrough” allowing a fibre to from the FAN to be patched through to the DFN without passing through the GPON splitter, although I’m not clear if NBN uses this capability to deliver the NBN Business services.

But having each port in the FDH going to one home would be too simple; you’d have to bring 576 individually sheathed cables to the FDH and you’d lose too much flexibility in how the cable plant can be structured, so instead we’ve got a few more joints to go before we make it to your house.

From the FDH cabinet we go out into the Local Fibre Network, but NBN has two variants of LFN – LFN and Skinny LFN.
The traditional LFN uses high-density ribbon fibres, which offer a higher fibre count but is a bit tricker to splice/work with.
The Skinny LFN uses lower fibre count cables with stranded fibres, and is the current preferred option.

The original LFN cables are ribbon fibres and range from 72 to 288 fibre counts, but I believe 144 is the most common.

These LFN cables run down streets and close to homes, but not directly to lead in cables and customer houses.

These run to “Transition Closures” (Older NBN) or “Flexibility Joint Locations” (FJLs – Newer NBN)

While researching this I saw references to “Breakout Joint Locations” (BJLs) which are used in FTTC deployments, and are a Tenio B6 enclosure for 2x 12 Fibers and 4x 1 Fibers with a 1×4 splitter.

The FJLs are TE Systems’ (Now Commscope) Tenio range of fibre splice closures, and they’re use to splice the high fibre count cable from from the FDH cabinets into smaller 12 fibre count cables that run to multiple “Splitter Multi Ports” or “SMPs” in pits outside houses, and can contain splitters factory installed.

The splitters, referred to as “Multiports” or “SMPs” are Corning’s OptiSheath MultiPort Terminals, and they’re designed and laid out in such a way that the tech can activate a service, without needing to use a fusion splicer.

Due to the difficulty/cost in splicing fibre in pits for a service activation, NBNco opted to go from the FJL to the SMPs, where a field tech can just screw in a weatherproof fibre connector lead in to the customer’s premises.

During installation / activation callouts, the tech is assigned an SMP in the pit near the customer’s house, and a port on it. This in turn goes to the FJL and onto FDH cabinet as we just covered, but that patching/splicing for that is already done, so the tech doesn’t need to worry about that.

The tech just plugs in a pre-terminated lead in cable with a weatherproof fibre end, and screws it into the allocated port on the SMP, then hauls the other end of the lead in cable to the Premises Connection Device (Made by Madison or Tyco), located on the wall of the customer’s house.

The customer end of the lead in cable may be a pre terminated SC connector, or may get mechanically spliced onto a premade SC pigtail. In either case, they both terminate onto an SC male connector, which goes into an SC-SC female coupler inside the PCD.

Next is the customer’s internal wiring, again, preterm cable is used, to run between the PCD and the First Fibre Wall Outlet inside the house. This preterm cable join the lead in cable inside the PCD on the SC-SC female coupler, to join to the lead in.

Inside the house we have the “Network Termination Device” (NTD), which is a GPON ONT, is where the fibre from the street terminates and is turned into an Ethernet handoff to the customer. NBN has been through a few models of NTD, but the majority support 2x ATA ports for analog phones, and the option for an external battery backup unit to keep the device powered if mains power is lost.

Phew! That’s what I’ve been able to piece together from publicly available documentation, some of this may be out of date, and I can see there’s been several revisions to the LFN / DFN architectures over the years, if there’s anything I have incorrect here, please let me know!

Australia’s secret underground telephone exchanges

A few years ago, I was out with a friend (who knows telecom history like no one else) who pointed at a patch of grass and some concrete and said “There’s an underground exchange under there”.

Being the telecommunications nerd that I am, I had a lot of follow up questions, and a very strong desire to see inside, but first, I’m going to bore you with some history.

I’ve written about RIMs – Remote Integrated Multiplexers before, but here’s the summary:

In the early ’90s, Australia was growing. Areas that had been agricultural or farmland were now being converted into housing estates and industrial parks, and they all wanted phone lines.
While the planners at Telecom Australia had generally been able to cater for growth, suddenly plonking 400 homes in what once was a paddock presented a problem.

There were traditional ways to solve this of course; expanding the capacity at the exchange in the nearest town, trenching larger conduits, running 600 pair cables from the exchange to the housing estate, and distributing this around the estate, but this was the go-go-nineties, and Alcatel had a solution, the Remote Integrated Multiplexer, or RIM.

A RIM is essentially a stack of line cards in a cabinet by the side of the road, typically fed by one or more E1 circuits. Now Telecom Australia didn’t need to upgrade exchanges, trench new conduits or lay vast quantities of costly copper – Instead they could meet this demand with a green cabinet on the nature strip.

This was a practical and quick solution to increase capacity in these areas, and this actually worked quite well; RIMs served many Australian housing estates until the copper switch off, many having been upgraded with “top-hats” to provide DSLAM services for these subscribers as well, or CMUX being the evolved version. There’s still RIMs that are alive in the CAN today, in areas serviced by NBN’s Fixed Wireless product, it’s not uncommon to see them still whirring away.

File:Telstra roadside cabinet housing a RIM and CMUX.jpg
A typical RIM cabinet

But in some areas planning engineers realised some locations may not be suitable for a big green cabinet, for this they developed the “Underground CAN Equipment Housing” (UCEH). Designed as a solution for sensitive areas or locations where above ground housing of RIMs would not be suitable – which translated to areas council would not them put their big green boxes on their nature strips.

So in Narre Warren in Melbourne’s outer suburbs Telecom Research Labs staff built the first underground bunker to house the exchange equipment, line cards, a distribution frame and batteries – a scaled down exchange capable of serving 480 lines, built underground.

Naturally, an underground enclosure faced some issues, cooling and humidity being the big two.

The AC systems used to address this were kind of clunky, and while the underground exchanges were not as visually noisy as a street cabinet, they were audibly noisy, to the point you probably wouldn’t want to live next to one.

Sadly, for underground exchange enthusiasts such as myself, by 1996, OH&S classified these spaces as “Confined Spaces”, which made accessing them onerous, and it was decided that new facilities like this one would only be dug if there were no other options.

This wasn’t Telecom Australia’s first foray into underground equipment shelters, some of the Microwave sites in the desert built by telecom put the active equipment in underground enclosures covered over by a sea freight container with all the passive gear.

In the US the L-Carrier system used underground enclosures for the repeaters, and I have a vague memory of the Sydney-Melbourne Coax link doing the same.

Some of these sites still exist today, and I was lucky enough to see inside one, and let’s face it, if you’ve read this far you want to see what it looks like!

A large steel plate sunk into a concrete plinth doesn’t give away what sits below it.

A gentle pull and the door lifts open with a satisfying “woosh” – assisted by hydraulics that still seem to be working.

The power to the site has clearly been off for some time, but the sealed underground exchange is in surprisingly good condition, except for the musky smell of old electronics, which to be honest goes for any network site.

There’s an exhaust fan with a vent hose that hogs a good chunk of the ladder space, which feels very much like an afterthought.

Inside is pretty dark, to be expected I guess what with being underground, and not powered.

Inside is the power system (well, the rectifiers – the batteries were housed in a pit at the end of the UECH entrance hatch, so inside there are no batteries), a distribution frame (MDF / IDF), and the Alcatel cabinets that are the heart of the RIM.

From the log books it appeared no one had accessed this in a very long time, but no water had leaked in, and all the equipment was still there, albeit powered off.

I’ve no idea how many time capsules like this still exist in the network today, but keep your eyes peeled and you might just spot one yourself!

Logging DSL Line Rate & SNR on a Draytek Modem

I am connected on a VDSL line, not by choice, but here we are.
DSL is many things, but consistent it not one of them, so I thought it’d be interesting to graph out the SNR and the line rate of the connection.

This is an NBN FTTN circuit, I run Mikrotiks for the routing, but I have a Draytek Vigor 130 that acts as a dumb modem and connects to the Tik.

Draytek exposes this info via SNMP, but the OIDs / MIBs are not part of the standard Prometheus snmp_exporter, so I’ve added them into snmp_exporter.yaml and restarted the snmp_exporter service.

  - name: Draytek_dsl_LineRate
    type: gauge
    help: adslAtucCurrAttainableRate

  - name: Draytek_dsl_Linerate_Down
    type: gauge
    help: Draytek_dsl_Linerate_Down

  - name: Draytek_dsl_Linerate_Up
    type: gauge
    help: Draytek_dsl_Linerate_Up

  - name: Draytek_dsl_SNR
    type: gauge
    help: adslAturCurrSnrMgn

Then I added this as a target in Prometheus:

  - job_name: Draytek Logger
    scrape_interval: 1m
    scrape_timeout: 30s
          - targets: ['']  # My modem

    metrics_path: /snmp
      module: ['draytek']
      - source_labels: [__address__]
        target_label: __param_target
      - source_labels: [__param_target]
        target_label: instance
      - target_label: __address__
        replacement: localhost:9116  # SNMP exporter address

And then from Grafana I can quantify exactly how bad my line is over time!

Only two dropouts today!

Australia’s East-West Microwave Link of the 1970s

On July 9, 1970 a $10 million dollar program to link Australia from East to West via Microwave was officially opened.
Spanning over 2,400 kilometres, it connected Northam (to the east of Perth) to Port Pirie (north of Adelaide) and thus connected the automated telephone networks of Australia’s Eastern States and Western States together, to enable users to dial each other and share video live, across the country, for the first time.

In 1877, long before road and rail lines, the first telegraph line – a single iron wire, was spanned across the Nullabor to link Australia’s Eastern states with Western Australia.

By 1930 an open-wire voice link had been established between the two sides of the continent.
This was open-wire circuit was upgraded a rebuilt several times, to finally top out at 140 channels, but by the 1960s Australian Post Office (APO) engineers knew a higher bandwidth (broadband carrier) system was required if ever Standard Trunk Dialling (STD) was to be implemented so someone in Perth could dial someone in Sydney without going via an operator.

A few years earlier Melbourne and Sydney were linked via a 600 kilometre long coaxial cable route, so API engineers spent months in the Nullarbor desert surveying the soil conditions and came to the conclusion that a coaxial cable (like the recently opened Melbourne to Sydney Coaxial cable) was possible, but would be very difficult to achieve.

Instead, in 1966, Alan Hume, the Postmaster-General, announced that the decision had been made to construct a network of Microwave relay stations to span from South Australia to Western Australia.

In the 1930s microwave communications had spanned the English channel, by 1951 AT&T’s Long Lines microwave network had opened, spanning the continental United States. So by the 1960’s Microwave transmission networks were commonplace throughout Europe and the US and was thought to be fairly well understood.

But soon APO engineers soon realised that the unique terrain of the desert and the weather conditions of the Nullabor, had significant impacts on the transmission of Radio Waves. Again Research Labs staff went back to spend months in the desert measuring signal strength between test sites to better understand how the harsh desert environment would impact the transmission in order to overcome these impediments.

The length of the link was one of the longest ever attempted, longer than the distance from London to Moscow,

In the end it was decided that 59 towers with heights from 22 meters to 76 meters were to be built, topped off with 3.6m tall microwave dishes for relaying the messages between towers.

The towers themselves were to be built in a zig-zag pattern, to prevent overshooting microwave signals from interfering with signals for the next station in the chain.

Due to the remote nature of the repeater sites, for 43 of the 59 repeater sites had to be fully self sufficient in terms of power.

Initial planning saw the power requirements of the repeater sites to be limited to 500 watts, APO engineers looked at the available wind patterns and determined that combined with batteries, wind generators could keep these sites online year round, without the need for additional power sources. Unfortunately this 500 watt power consumption target quickly tripled, and diesel generators were added to make up any shortfall on calm days.

The addition of the Diesel gensets did not in any way reduce the need to conserve power – the more Diesel consumed, the more trips across the desert to refuel the diesel generators would be required, so the constant need to keep power to a minimum was one of the key restraints in the project.

The designs of these huts were reused after the project for extreme temperature equipment housings, including one reused by Broadcast Australia seen in Marble Barr – The hottest town in Australia.

Active cooling systems (Like Air Conditioning) were out of the question due to being too power hungry. APO engineers knew that the more efficient equipment they could use, the less heat they would produce, and the more efficient the system would be, so solid state (transistorised devices) were selected for the 2Ghz transmission equipment, instead of valves which would have been more power-hungry and produced more heat.

The reduced power requirement of the fully transistorized radio equipment meant that wind-supplied driven generators could provide satisfactory amounts of power provided that the wind characteristics of the site were suitable.


So forced to use passive cooling methods, the engineers on the project designed the repeater huts to cleverly utilize ventilation and the orientation of the huts to keep them as cool as possible.

Construction was rough, but in just under 2 years the teams had constructed all 59 towers and the associated equipment huts to span the desert.

When the system first opened for service in July 1970, live TV programs could be simulcast on both sides of the country, for the first time, and someone in Perth could pick up the phone and call someone in Melbourne directly (previously this would have gone through an operator).

PMG Engineers designed a case to transport the fragile equipment spares – That resided in the back of a Falcon XR Station Wagon

The system offered 1+1 redundancy, and capacity for 600 circuits, split across up to 6 radio bearers, and a bearer could be dedicated at times to support TV transmissions, carried on 5 watt (2 watt when modulated) carriers, operating at 1.9 to 2.3Ghz.

By linking the two sides of Australia, Telecom opened up the ability to have a single time source distributed across the country, the station in Lyndhurst in Victoria, created the 100 “microseconds” signal generated by a VNG, that was carrier across the link.

Looking down one of the towers

Unlike AT&T’s Long Lines network, which lasted until after MCI, deregulation and the breakup off the Bell System, the East-West link didn’t last all that long.

By 1981, Telecom Australia (No longer APO) had installed their first experimental optic fibre cable between Clayton and Springvale, and fibre quickly became the preferred method for broadband carrier circuits between exchanges.

By 1987, Melbourne and Sydney were linked by fibre, and the benefits of fibre were starting to be seen more broadly, and by 1989, just under 20 years since the original East-West Microwave system opened, Telecom Australia completed a 2373 kilometre long / 14 fibre cable from Perth to Adelaide, and Optus followed in 1993.

This effectively made the microwave system redundant. Fibre provided a higher bandwidth, more reliable service, that was far cheaper to operate due to decreased power requirements. And so piece by piece microwave hops were replaced with fibre optic cables.

I’m not clear on which was the last link to be switched off (If you do know please leave a comment or drop me a message), but eventually at some point in the late 1980s or early 1990s, the system was decommissioned.

Many of the towers still stand today and carry microwave equipment on them, but it is a far cry from what was installed in the late 1960s.

Advertisement from Andrew Antennas


East-west microwave link opening (Press Release)

Walkabout.Vol. 35 No. 6 (1 June 1969) – Communications Across the Nullabor

$8 Million Trans-continental link

ABC Goldfields-Esperance – Australia’s first live national television broadcast

APO – Newsletter ‘New East-West Trunks System’ 50 years since Project Australia

Whirlpool Post

TJA Article on spur to Lenora

Improving WiFi Calling quality for WiFi Operators

I had a question recently on LinkedIn regarding how to preference Voice over WiFi traffic so that a network engineer operating the WiFi network can ensure the best quality of experience for Voice over WiFi.

Voice over WiFi is underpinned by the ePDG – Evolved Packet Data Gateway (this is a fancy IPsec tunnel we authenticate to using the SIM to drop our traffic into the P-CSCF over an unsecured connection). To someone operating a WiFi network, the question is how do we prioritise the traffic to the ePDGs and profile it?

ePDGs can be easily discovered through a simple DNS lookup, once you know the Mobile Network Code and Mobile Country code of the operators you want to prioritise, you can find the IPs really easily.

ePDG addresses take the form so let’s look at finding the IPs for each of these for the operators in a country:

The first step is nailing down the mobile network code and mobile country codes of the operators you want to target, Wikipedia is a great source for this information.
Here in Australia we have the Mobile Country Code 505 and the big 3 operators all support Voice over WiFi, so let’s look at how we’d find the IPs for each.
Telstra has mobile network code (MNC) 01, in 3GPP DNS we always pad network codes to 3 digits, so that’ll be 001, and the mobile country code (MCC) for Australia is 505.
So to find the IPs for Telstra we’d run an nslookup for – The list of IPs that are returned, are the IPs you’ll see Voice over WiFi traffic going to, and the IPs you should provide higher priority to:

For the other big operators in Australia will get you Optus and will get you VHA.

The same rules apply in other countries, you’d just need to update the MNC/MCC to match the operators in your country, do an nslookup and prioritise those IPs.

Generally these IPs are pretty static, but there will need to be a certain level of maintenance required to keep this list up to date by rechecking.

Happy WiFi Calling!

Number Pads – Calculator or Phone?

If you’re typing on a full size keyboard there’s a good chance that to your right, there’s a number pad.

The number 5 is in the middle – That’s to be expected, but is 1 in the top left or bottom left?

Being derived from an adding machine keypad, the number pad on a keyboard has a 1 will be in the bottom left, however in the 1950s when telephone keypads were being introduced, only folks who worked in accounting had adding machines.

So when it came time to work out the best layout, the result we have today was a determined through a stack of research and testing by Human Factors Engineering Department of Bell Labs who studied the most efficient layout of keys, and tested focus groups to find the layout that provided the best level of speed and accuracy.

That landed with the 1 in the top left, and that’s what we still have today.

Oddly ATM and Card terminals opted to use the telephone layout, rather than the adding machine layout, while number pads use the adding machine layout.

A few exceptions to this exist, for example the Telecom ComputerPhone (Aka the Merlin Tonto in the UK, or the New Zealand Post Office Computerphone, or the ICL One Per Desk) which is the keyboard as envisioned by the telephone company.

NBNco’s FTTN – What’s in the box?

Note: All information contained here is sourced from: Photos provided by NBNco’s press pages, Googling part numbers from these photos, and public costing information.

This post covers the specifics and capabilities of NBNco’s FTTN solution, and is the result of some internet sleuthing.

If some of the info in here is now out of date, I’d love to know, let me know in the comments or drop me an email and I’ll update it.

FTTN in Numbers

A total of 24,544 nodes have been deployed upon completion of roll out. Each node is provisioned with 384 subscriber ports.

The hardware has 10Gbps shared between the 384 subscriber lines, equating to 208Mbps per subscriber.

Construction costs were $2.311 billion and hardware costs were $1.513 billion,

For the hardware this equates to $61,644 per node or $160 per subscriber line connected (each node is provisioned with 384 ports)

Full cost for node including hardware, construction and provisioning is $244,150 per node, which is $635 per port.

To operate the FTTN infrastructure costs $709 million per year (Made up of costs such as power, equipment servicing and spares). This equates to $28k per node per annum, or $75 per subscriber. (This does not take into account other costs such as access to the copper, transmission network, etc, just the costs to have the unit powered on the footpath.)


Inside the FTTN cabinets is a Alcatel Lucent (now Nokia) ISAM 7330 cabinet mounted on it’s side,

On the inside left of the door is a optic fibre tray where the transmission links come into the cabinet,

On the extreme left is a custom panel. It contains I/Os that are fed to the 7330, such as door open sensor, battery monitoring, AC power in, SPD and breaker.

Connection to subscriber lines happens on a frame at the end of the cabinet.

Alcatel Lucent ISAM 7330 FTTN

NBN co’s nodes are made up of Alcatel Lucent (Now Nokia) ISAM (Intelligent Services Access Manager) 7330 FTTN rack mounted it’s side.

1GFC (General Facilities Card)Power and alarm management
2NT Slot (NANT-E Card)Main processing and transmission
3NTIO Slot (NDPS-C Card)VDSL vectoring number-crunching
4NT Slot (Free)Optional (Unused) backup Main processing and transmission
5-12LT (NDLT-F)48 Port VDSL Subscriber DSLAM Interfaces
Slot numbering is just counting L to R, ALU documentation has different numbering

First up is the GFC (General Facilities Card) which handles alarm input / output, and power distribution. This connects to the custom IO panel on the far left of the cabinet, meaning the on-board IO ports aren’t all populated as it’s handled by the IO panel. (More on that later)

Next up is the first NT slot, there are two on the 7330, but in NBN’s case, only one is used; the second can be used for redundancy if one of the cards were to fail, but it seems this option has not been selected. In the first and only populated NT slot is an NANT-E Card (Combined NT Unit E) which handles transmission and main processing.

All the ISAM NANT cards support support RIPv2! But only the NANT-E card also supports BGP – Interestingly they don’t have BGP on all the NANT cards?

To the right of that is the NTIO slot, which has a NDPS-C card, which handles the vector processing for VDSL.

Brief overview of Vectoring: By adding vectoring to DSL signals allows noise on subscriber loops to be modeled, and then cancelled out with an integrated anti-phase signal matching that of the noise.

The vectoring in VDSL relies on pretty complex number crunching as the DSLAM has to constantly process the vectoring coefficients which are different for each line and can change based on the conditions of the subscriber loop etc. To do this the NDPS-C has two roles;
The NDPS-C’s Vectoring Control Entity performs non-real time calculations of vectoring coefficients and handles joining and leaving of vectored VDSL2 lines.
While the NDPS-C’s Vectoring Processor performs the real time matrix calculations based on crosstalk correction samples for the VDSL symbols collected from the subscriber lines.
The NDPS-C has a Twinax connection to every second LT Card.

After the NTIO slot is the unused NT slot.

Finally we have the 8 LT slots for line cards, which for FTTN is using the NDLT-F are 48 port line cards.

The 8 card slots allows 384 subscriber lines per node.

These are the cards which the actual subscriber lines ultimately connect to. With 10Gbps available from the NT to the LTs, means each LT card with 48 subs so 208 Mbps per subscriber max theoretical throughput.

POTS overlay is supported, this allowed VF services coexisted on the same copper during the rollout. M / X pairs are no longer added inline on new connections. (More on that on cabling).

Power & Environment

The 7330 has a 40 amp draw at -48v would mean the unit consumes 1920w

The -48v supply is provided by 2x Eltek Flatpack2 rectifiers, each providing 1Kw each.

These can be configured to provide 1Kw with redundancy to protect against the failure of one of the Flatpack2 units, or 2Kw with no redundancy, which is what is used here.

On the extreme left is a custom panel. It contains alarm I/Os that are fed to the 7330, such as door open sensor, battery monitoring, etc.

It also is the input for AC power in, surge protection device and breakers.

I did have some additional information on the batteries used and the power calculations, however NBNco’s security team have asked that this be removed.


Incoming transmission fiber comes in on NBNco’s green ribbon fibre, which terminates on a break out tray on the left hand side wall of the cabinet. Spliced inside the tray is a duplex LC pigtail for connecting the SMF to the 7330. I don’t have the specifics on the optics used.

Subscriber lines come in via an IDC distribution frame (Quante IDS) on the right hand side end of the cabinet, accessed through a seperate door.

This frame is referred to as the CCF – Cross Connect Frame.

There are two sets of blocks on the CCF, termination of ‘X’ and ‘C’ Pairs.

‘X’ Pairs are the VF Pairs (PSTN lines) connecting to the pillar where they are jumpered back to the ‘M’ pairs back to the serving exchange,

‘C’ Pairs are the pairs containing combined VDSL & VF services to to the pillar where they are jumpered to the ‘O’ pairs which run out to the customer’s premises,

Tiny Pillars in the CAN

On the rare occasions I’m not tied to my desk, I’m out for a long run along some back roads somewhere.

Every now and then I come across these tiny telecom pillars for cross-connection (and don’t shoot at them) – I mostly find them around the edges of distribution areas.
I had some recollection that these were originally for trunk lines between exchanges (maybe there was some truth to this?), but some digging in old docs show these were just for interconnecting main or branch cables with distribution cables, in areas where the 600 and 1200 pair pillars / cabinets would be overkill.

They’re built like the 900/1800 pair cabinets, but just scaled down versions, supporting 1x 100 pair main cable, 1x 100 pair distribution cables and 2x 50 pair distribution cables.

It seems like these were largely decomed when NBN took over, leaving most with a big X sprayed on them.

While I was looking through the docs I also found reference to a 180 pair pillar, which looked very similar, but I’ve yet to see any of them left in the wild. Better keep running ’till I find one!

Charging problem on Fluke 990 CopperPro

I have a bit of a thing for Test Sets

Arguably, the most capable (toolbox-carryable) test set out there is the Fluke 990 CopperPro, combined TDR, Butt Set, Toner, RFL, Noise meter, etc, etc, it’s a really cool gizmo (And probably worthy of a blog post in itself someday).

Alas mine had stopped taking much of a charge, you’d plug it into the charger, and after 20 minutes of use, it’d report low power and shut down.

Sitting on the charger the Fluke would show the red charging light for about 20 minutes, then the charging light would turn off.

If I unplugged and replugged the charger I’d get red charging light for another few minutes, then turn off again.

Naively, I ruled it to be an issue with the battery (Which is close to 10 years old), and ordered a new one.

But with the new battery in hand, the same issue.

Stupidly, it turns out I was using a 15v charger, technically the unit supports a 15v charger, but it seems after a period, the internal voltage regulator overheats and shuts off, meaning the battery never got a good charge.

Swapping it with a 12v charger and I’m charging without issues.

But not before I ended up ordering a new battery, so now with the new battery I’m getting 15 hours of runtime out of a charge, and still squeezing 7 out of 8 year old battery it originally came with.

Dumb mistake but hopefully an easy fix for anyone with the same issue.

Australia’s fake Phone Numbers

For TV, Books, Movies, etc, ACMA have allocated a series of fake phone numbers that can be used, that will not connect,

Check out this great Tom Scott video on the topic of fake phone numbers, for the why.

In Australia they are:

  • Premium Rate Number 1900 654 321
  • Central East (covering NSW and ACT) / (02) 5550 xxxx and (02) 7010 xxxx
  • South East (covering VIC and TAS) / (03) 5550 xxxx and (03) 7010 xxxx
  • North East (covering QLD) / (07) 5550 xxxx and (07) 7010 xxxx
  • Central West (covering SA, WA and NT) / (08) 5550 xxxx and (08) 7010 xxxx
  • Some (but not all) mobile starting with 0491 570 xxx
  • Some (but not all) Freephone / Local rate starting with 1800 975 xxx

More info on ACMA Website

Telecom Pillars – Resistance to Rifle Fire?

The 900 and 1800 pair telecom distribution pillars (aka cabinets) are still a familiar sight almost everywhere in Australia where copper networks are still used, however prior to the early 1970s they were only deployed in metropolitan areas, and apparently one of the concerns of deploying them in rural areas was that they’d be shot at.

June 1966 issue of the Telecommunications Journal of Australia (TJA) has an article titled “Aluminum Distribution Cabinets – Resistance to Rifle Fire” is below, click to get the image full size.

At the short range, the vandal is expected to have either sufficient common sense or hard earned experience to realise the danger of ricochet.

I like big Butts and I cannot lie.

In other parts of the world it’s known as a telephone test set, lineman’s handset, test phone, etc, but to me it’s a butt / butt set / buttinski.

They’re essentially ruggedized, portable telephones, often with an ability to monitor a line without looping it / going off hook, and used by techs and lineys throughout phone networks everywhere.

I carry Fluke TS52 Pro in my toolbox, it’s got a built in voltmeter, waterproof, backlit display and lots of memory storage options.

It’s a really beautiful bit of kit, (only thing missing is a TDR which the next model up has) but I very rarely use it.

The butt set is in my mind the quintessential piece of test gear, and I’ve got a few from various time periods.

The Telecom Ruggabut was launched in 1994/1995 and was standard issue prior to privatization, and was designed in Australia for the Australian market,

As such it features some uniquely Australian features such as detection for 12kHz Subscriber Pulse Metering (used in Payphones), while the “TLB” Button is tone-loop-break, a 100ms pause in dialling,

Prior to the Ruggabutt there was the Versadial and Versadial Mk2. Lightweight, tough and with a handy RJ12 jack for testing subscriber handpieces, these were made in huge numbers, by PMG and then Telecom.

And as far back as my “collection” goes is the Australian Post Office (APO) Telephone Test Handset No. 4, which lives on the Step exchange in my office, and is a simple rotary dial plus speaker, mic, switch and Neon light to denote ringing.

My 2021 Telco Reading List for the Holidays

Here’s the list of books I’ve got for the holiday period:

5G Core Networks: Powering Digitalization

A good technical overview of the 5GC architecture, covering the actual elements and their interfaces / reference points, without any talk of robotic surgery.

Clear Across Australia (A history of Telecommunications)

Ann Moyal

This one is an actual hardback book that came in the mail, not just delivered to my ebook reader!

It covers the history of telecommunications in Australia, right from Charles Todd’s Overland Telegraph Line, to the first talk of “Integrated Digital Network” (Later ISDN).

Sonet / SDH Demystified

Steven Shepard

An overview of SDH/PDH networks, for the somewhat beginner.

The Idea Factory

Jon Gertner

A history of Bell Labs and it’s many, many, many achievements.

AS/CA S009:2020 Key Changes for Cablers

Recently, ACMA / Communications Alliance updated the rules defining cabling – S009 – “Installation requirements for customer cabling” aka the “Wiring Rules” or “Cabling Bible”.

I don’t talk much about cabling on this blog – but I’m still a registered cabler so need to keep up to date on the changes, and quite a lot has changed since the last update in 2013 – Authority to Alter (A2A) has moved from Telstra to NBNco, PayTV over HFC is far less common, and the NBN rollout is “finished”.

So what are the key changes I need to know about? I had a read and compared to S009 / 2013, and here are they are:

“Supervised” Definition

In order to gain cabling registration you need 360 hours of supervised cabling experience. The specification has been updated to define exactly what supervised means,

4.2.59 instructed person
a person instructed or supervised by a Skilled Person as to energy sources and who can responsibly use equipment safeguards and precautionary safeguards with respect to those energy sources.
Note: Supervised, as used in the definition, means having the direction and oversight of the performance of others.

ES3 (Electrical energy source class 3 (ES3)) Definition & Rules

Reverse power feed, used in NBN FTTC tech, as well as higher voltages used for EWIS and PA systems, has led to the introduction of a new classification – ES3, for cabling that exceeds the ES2 limits,

a metallic circuit utilised for communications or Power Feeding, or both, that—
(a) exceeds the ES2 voltage and touch current limits;
(b) does not exceed 400 V d.c. between conductors; and
(c) does not exceed current as specified in AS/NZS 11801.1 or ISO/IEC 11801-1.

4.2.45 ES3 generic circuit

ES3 falls into two categories, which specific whether it can be carried over generic cabling or not,

(a) over Generic Cabling, in this Standard, are based on—
(i) circuit voltage not exceeding 400 V d.c. between conductors; and
(ii) circuit current not exceeding that specified in AS/NZS 11801.1 or ISO/IEC 11801-1.
Where voltages and currents exceed these limits, then Special Application Cabling, as classified in Item F.2(b), should be used.
(b) over Special Application Cabling in this Standard, are based on a voltage limit and current limit set by Cable manufacturer for the specific Cable and its installation requirements


So if part a is exceeded, Special Application cabling is required;

  • the cabling must meet a higher standard defined for ES3
  • must be identified by it’s sheath colour and markings at regular intervals
  • cabling has to be separated from other services (sub-ducted or separated by a barrier or more than 150mm)
  • must carry a warning label wherever the conductive part of the circuit is exposed (frames / joints) stating it is an ES3 service
  • service may not be terminated on a plug if the plug may have exposed contacts (requires a plug / socket with shutters)

RFT (Remote feeding telecommunication circuit) Definition

an equipment circuit within the ICT Network not connected to Mains power, intended to supply or receive DC power at voltages exceeding the limits of ES2, and on which transient overvoltages or overcurrents may occur.


Examples are PoE, ring current, USB-C / USB3, etc.

RFT circuits are classified as ES3 circuits and subject to the same conditions.

New Conductor Size / Temperature Recommendations

S009 / 2013 did not specific recommended (not mandated) size & temperature rating for generic cabling / jumpering.

It comes down to:

“have a maximum conductor resistance of 0.0938 Ω/m at 20° C “
“the cable should not be installed in a manner that may cause the maximum operating temperature rating of the Cable to be exceeded.”


Plug Terminated Cabling Requirements

Moveable cabling / plug terminated cabling must not be used unless:

the Plug is an integral part of a device that is fastened to a
wall, floor or ceiling or other permanent building element; or
(b) the Plug is not fixed and—
(i) the Plug terminates a section of Movable Cabling;
(ii) the Plug is to mate with a Port on an item of fixed Customer Equipment; and
(iii) in every position to which it may be moved when the Plug is not mated with the Port, every part of the section of Movable Cabling is either out of Arm’s Reach or housed in a Secure Enclosure that is fastened to a wall, floor or ceiling or other permanent building element.


Network Boundary Definition Update

A new Appendix (J) has been added with updated (informative only) definitions of Network Boundaries with examples, to support all the new network boundary definitions introduced with the access technology mix(fibre, HFC and wireless terminations).

FTTC Deployment Information (Informative)

A new Appendix (O) has been added providing information in regards to FTTC and it’s requirement to isolate the first socket from the rest of the cabling – Something that in practice seems to be a rarity.

Labelling & Safety Rules for Fibre Optic Cabling

A new requirement has been added to 11.1 in regards to Fibre Optic cabling must:

  • Have a Warning of potential hazardous laser levels
  • Have a warning regarding Access to emitted radiation
  • Types of laser warning markings
  • Laser warning marking style
  • Laser explanatory label wording
  • Marking durability of labels
  • Fibre outlets in work areas are except
  • Groups of optical fibre connectors may be marked as a group
  • Multiple markings – ie one inside the container one outside
  • Unused optical fibre connectors and adaptors must be covered

Of course, this is all just a summary of the changes I thought were key, but you can get the latest version of S009 from the Comms Alliance website.

Do your records!

NBN Skymuster Satellite Technical Overview

I’m a bit of a radio nerd & I’ve worked Satellites before, so the Skymuster / LTSS program had me curious. So here’s some nitty-gritty details on NBNCo’s Skymuster Satellite service.

The Payload

NBNco called the LTSS (Long Term Satellite service) but before launch they re-branded as “Skymuster”.

NBNco provided an Interim service called ISS (Interim Satellite Service). before the launch. IPSTAR satellite (Formerly ABG) and Optus services delivered this. Both of these had limited bandwidth and has since been largely replaced by the Skymuster / LTSS.

NBNCo contracted Space Systems / Loral, a US based satellite manufacturer to design and build the payloads. It’s based on the SSL 1300 platform.

When deployed, the payload itself measures 26 metres long, 9 metres tall and 12 metres wide, and weighs in at 6400Kg. Before deployment, in the satellite’s compressed form it fits within a 5-meter launch-vehicle fairing.

Communication to earth is via Ka-band frequencies which allows for greater density of spot beams and frequency reuse. However, capacity improvement through higher frequencies does come with some tradeoffs. Ka-band frequencies, are more susceptible to weather related conditions compared to Ku-band frequencies. Directional accuracy becomes way more important when aligning the customer dishes in Ka band also.

SSL provided image of SL-1300
DirectionMin FreqMax Freq
Earth to Satellite27Ghz31Ghz
Satellite to Earth17.7Ghz22Ghz

These emissions are within the range of the higher end software defined radio receivers. I’m curious to see what’s being transmitted, but that’s a topic for another day.

The downlink uses RH and LH circular polarisation.

The Journey

SSL assembled the satelite in California.

SSL staff packed it into a crate and loaded into the belly of an Antinov An-124 which is flown to the launch site.

There are two Skymuster Satellites, NBN-Co 1A & 1B. 1B provides infill / capacity layer for 1A but both are identical. If the 1A satellite was lost during launch / deployment, 1B could be sent up in it’s place. This is still a real risk when launching anything.

NBN-Co 1A was the first launched, riding on a Ariane-5ECA from Guiana Space Centre in French Guiana, South America. 1A launched on 30.09.2015 and 1B launched 05.10.2016 in the same configuration.

After launch to a transit orbit, the satellites had to navigate up into a geostationary orbit at ~36,000Km. This was done using it’s 4 × SPT-100 plasma thrusters, which are exactly as cool as they sound. The final navigation process took up 40% of the fuel in the satellite. Fuel is the determining factor for the expected ~15 year lifetime of the two satellites.

SPT-100 – Source: NASA

Once in final position SSL performed 2 months worth of tests referred to as “In Orbit Testing”. SSL then handed over operational Telemetry, Tracking and Command (TT&C) to Optus Satellite (Singtel). Optus are tasked with keeping it in it’s current position.

Customer Hardware

Ericsson manage the installation, and subcontract to Hills and Skybridge for the actual work.

Out Door Unit (ODU)

There are currently 3 Satellite Antenna options that are available for
installation, 80cm, 1.2m & 1.8m.

NBNco’s Test Setup

Narrower Ka-Band signals drops off more rapidly than Ku-Band signals. This means that aligning the Ka-Band antenna within the degrees of usable Azimuth within the Line of Sight maximises the antenna gain.

Required accuracy for each of the antennas:

  • 80 cm: 1.4 degrees,
  • 120 cm: 1.0 degrees
  • 180 cm: 0.7 degrees

The below graph shows being off by 1 degree from the required accuracy, leads to -30dB drop. This translates to a power ratio of 1000, or 1/1000 of the power if correctly aligned.

The alignment process is done by the installer pointing the dish in the correct azimuth / elevation. This is based on compass / inclinometer readings, or smart phone apps. Once a rough alignment has been set, a tone-generator on the TIRA is used to align the dish.

This process requires a 16 digit installation key.

The key containing the frequency used in the installation, beam Assignment & TRIA Polarisation (The 6w version has automatic (Polarisation).

That’s entered into the installation setup page at:

TIRA’s has a built in Tone Generator which is used to “Point and Peak” the dish from the roof. The tones are:

  • Heartbeat 3KHz
  • Pointing Tones 2.5 – 3.1KHz
  • Peaking Tones 2.5, 2.95, 3.1 and 3.3KHz

ViaSat have videos on how the alignment process is performed.

IDU (Modem) / NTD

The modem itself is manufactured by ViaSat. I can’t find any specifics it seems to be in the RM511x line of Satellite modems.

There were some issues with a firmware update on these in 2018, that saw firmware getting rolled back.

The modems / IDU / NTDs for the ISS are not compatible with the LTSS.

There’s some nice teardown photos of a similar ViaSat modem here.

TRIA (Transmit/Receive Integrated Assembly )

The TRIA is the equivalent of a feed horn, an all in one Tx/Rx assembly. They are available in 3w and 6w variants, based on the estimated signal levels of the installation location. That’s determined by factors like high rain areas or if the subscriber is on the edge of a beam.

3W Version

The 6W version has an extra F-Connector for the required DC power injection. The 6w version also has a two F-Connector gang-plate / wallplate when installed for the second RG6 run to power it.

Interestingly there’s a minimum length of cable run (8m) specified for these installations. Anything less than 8m leads to lower resistance and possible overheating.

There is a minimum length of 8m for the cable run this is very
important as it provides the right amount of cable resistance so
the modem does not get hot and over heat. Max cable run is 50m.


Transparent Performance Enhancing Proxy (TPEP)

TPEP aka Web Acceleration, is a service offered by NBNco to spoof TCP replies, to make the handshake more efficient. It can, unsurprisingly, lead to headaches accessing services, particularly those that employ TLS.

Web Interface
user name = ADMIN and the password = operator (lower case)

Beam Selection

The installer key sets the beam, and his can be remotely changed by NBNco MAC / NOC team.

BIRRAUS have a good article explaining the spot beams available.

Educational Port

Like the other NBNco NTDs, there are multiple UNI-D ports available on the Skymuster modem allowing segregation of services.

One option that seems to be gaining traction is a dedicated port on the modem for educational use, on one of the UNI-D ports on the modem.

Educational Ports are configured to allow access for remote / distance education students.

The local state government sets pricing, speeds and data usages.

Ground Stations

There are 9 active and one standby ground stations, geographically spread across Australia, with a standby in Wolumna, NSW. The standby is capable of assuming control for any of the other ground stations.

ViaSat built the equipment and services different spot beams.

Again, BIRRAUS have this covered in their article, but here’s an extract they’ve made listing the ground stations and beams serviced.

Wolumla ground station


Solar Transit

Solar transits happen twice yearly when the satellite is aligned directly between the sun and Australia.

The immense solar radiation from the sun overloads the transceivers on the ground, as they’re positioned at the satelite, with the sun behind it overloading the signals.

This lasts for about 6 minutes twice yearly, and affects different ground stations and each of the satellites at different times.

Copper Cutoff

Currently the copper decommissioning does not apply to Skymuster services. This means customers with a copper POTS line, can keep it indefinitely.

This has lead to headaches with incumbent providers who had intended to decommission / sell off remote exchanges, but will be required under Universal Service Obligation to keep them active.

3rd Satellite

Due to unexpectedly large uptake of Skymuster services, NBNco had floated the possibility of launching a 3rd Satelite in 2020:

Scenario 3: Third satellite – This scenario assumes that NBN Co constructs and launches a third satellite at the end of CY20. This mitigates the need to build some fixed wireless base stations and FTTN distribution areas. The capacity of this satellite will only be partially required to meet NBN Co’s needs

Scenario 4: Third satellite in partnership – This scenario mirrors Scenario 3, but assumes that NBN Co enters into a partnership with an external party to access only the required capacity on a third satellite rather than building and owning it outright.

Source – NBNco Fixed Wireless & Satellite Review

Portable Services

Apart from spot-beam migration, there are no technical limitations preventing portable Skymuster services from becoming a service offered.

Qantas are using this to power the in-flight WiFi on their domestic fleet of 80 Boeing 737 and Airbus A330s. Though it seems that may no longer be the case.

The NBNco launched a fleet of “Road Muster” 4WDs for promotion of the services. They drive from town to town, spruiking the benefits of Skymuster.

On the roof of the 4WD is a Satellite ODU, which seems to be self / remote positioning.

Online sleuthing reveals it’s a EXPLORER 8120 manufactured by Cobham. It featuring auto-acquire, drive-away antenna system using Dynamic Pointing Correction technology. At $32k USD, it’s rather pricey, and outside the range of most grey-nomads and campers.

If a user wanted to manually position the dish, they could using a service like or Wolfram Alpha.  This would give a rough alignment and then the tone generator “Point and Peak” for the fine adjustment.

Layer 3 Services

Skymuster services are setup as L2 services.

NBNCo has highlighted from day 1, the option of using Layer 3 for deliver to enable deep packet inspection.

This would allow them to prioritise traffic more easily / efficiently.


Please let me know in the comments if I’ve got anything here wrong.

Final Selectors in a ATE50 Step by Step Telephone Exchange

1938 ATE PAX50 Step By Step Exchange

Steel Switchboard & Switchgear

That’s all the description said.

The blurry photo didn’t make anything that much clearer, but they looked like two motion switches, and being a big fan of really old telco hardware, I found myself driving to an auction selling things very much unrelated to telephone exchanges to bid on what I thought might have been a step-by-step exchange.

Photo from listing

$50 later I am now the proud owner of an Automatic Telephone & Electric Co (ATE) Liverpool works 50 line PAX (Private Automatic Exchange).

The switch

My office now has less room, a big burly battery eliminator and ring machine take up the space on my desk, but I couldn’t be happier with it.


Of the 5 final selectors I’ve got two somehow worked “out of the box”, while the other 3 all need some serious adjustment, but she clicks and she’s mostly complete, so should be a good summer holiday project!

I’ll post some video up when she’s fully functional.

NBNCo Transit Demystified

There’s always a lot of talk and opinion about the technologies the NBN employs, it’s effectiveness, etc.

I’ve made a conscious decision to steer clear of opinion in this blog, but there’s often talk and blame shifting between NBNco and RSPs, so I thought I’d cover how the business model works.

Because of this I thought it’d be interesting to write about how the network actually works between carriers (RSPs) and NBNco.

Physical Structure

Last Mile

The last mile in US terms, CAN in Australian Telecom lingo, is connecting the subscriber edge to the network.

NBNCo employs a few different technologies for this, depending on a number of factors;

NBNco Backhaul

All these last mile services get consolidated and eventually end up at a local PoI – Point of Interconnect, (typically called a POP if you’re any other telco).

These are typically hosted inside exchanges, but not every exchange is an NBNco PoI, if it’s not it uses NBN Backhaul to get to the nearest PoI.

NBNco currently operates 121 PoI sites.

NBNco don’t exclusively use TEBA sites, some are hosted in NBNco “Depots”, there’s currently 10 sites not in TEBA footprints.

At the PoI

Retail Service Providers (RSPs) have to have racks inside the PoI locations, and essentially setup layer 2 cross-connects to the NBNco racks.

Once the traffic is on the RSP network, it’s the RSP’s responsibility to carry it where it needs to go, via their own network / backhaul.

Billing and Metering

Of course, if NBNco is handing off the pipes of customer traffic off to each RSP they need a way to charge the RSPs for this, this is handled by two elements – CVCs equating to the bandwidth at the PoI and AVCs equating to a fixed standing charge per connection monthly.

CVC – Connectivity Virtual Circuit

At the PoI the connection between the NBNco rack and the RSP rack is metered over a CVC – Connectivity Virtual Circuit.

This is shared across all users of that RSP at that PoI.

Let’s say I’m an RSP and I’ve purchased a 1Mbps CVC shared across my 1,000 customers at that PoI, the customers aren’t going to have a good experience.

Of course, CVC bandwidth isn’t free, previously NBNco charged on average $15.25/Mbps.

This had the effect of ensuring each RSP had just enough CVC bandwidth for their customers, but this led to some customers having a poor experience on switching to NBNco as they found their speeds dropped due to not enough CVC bandwidth at the PoI for that RSP.

In June 2017 NBNco announced a change to the pricing structure to try and encourage RSPs to buy more CVC bandwidth to ensure customers speeds weren’t bottlenecked at the CVC.

The new pricing structure makes it more financially attractive to buy more CVC bandwidth based on how many active connections (AVCs) an RSP has in place.

NBNco now charges $17.50 per symmetrical Mbps for each traffic class. (More on traffic classes later)

This means at each PoI the RSP must have a pool of CVC bandwidth large enough to meet the needs of all the customers connections (AVCs) bandwidth needs at that PoI.

AVC – Access Virtual Circuit

NBNco charges AVC fees based on the speed tier the end user will have and the traffic class (QoS) the service has applied.

(This speed tier is regardless of if the RSP has the CVC bandwidth to support this)

Pricing of TC4 (Best Effort) AVCs

Introducing NNIs

NBNco acknolged in Jul 2018 that for some carriers (RSPs) having presence in 121 sites puts up a large barrier to entry.

To counteract this they introduced Network-Network Interface (NNI).

Imagine you’re operating an RSP with a footprint in capital cities and PoI / CVCs in populated areas, you can’t serve customers in remote areas without having a presence at their local NBNco PoI location and buying CVC bandwidth for that location – It just wouldn’t stack up financially.

NBNco introduced the NNI product to essentially backhaul the traffic from these customers to the nearest PoI their RSP is at and share the CVC bandwidth at that PoI.

Making use of Australian Elevation Data in Forsk Atoll

The Australian Government publishes elevation data online that’s freely available for anyone to use. There’s a catch – If you’re using Forsk Atoll, it won’t import without a fair bit of monkeying around with the data…

The data is published on a a system called ELVIS – Elevation – Foundation Spatial Data.

You draw around the area you want to download, enter your email address and you’re linked to a download of the dataset you’ve selected.

So now we download the data from the link, unzip it and we’re provided with a .tiff image with the elevation data in the pixel colour and geocoded with the positional information.

Problem is, this won’t import into Atoll – Unsupported depth.

Forsk Atoll - Unsupported Depth when importing

I found a tool called VTBuilder – A tool for messing with terrain data.

I fired it up, and imported the elevation tiff file we’d downloaded.

Selected “Elevation” waited a few seconds and presto!

We can export from here in the PNG 16 bit grayscale format Atoll takes, but there’s a catch, negative elevation values and blank data will show up as giant spikes which will totally mess with your propagation modeling.

So I found an option to remove elevation data from a set range, but it won’t deal with negative values…

So I found another option in the elevation menu to offset elevation vertically, I added 100 ft (It’s all in ft for some reason) to everything which meant my elevation data that was previously negative was now just under 100.

So if an area was -1ft before it was now 99ft.

Now I was able to use the remove range for anything from 0 100 ft (previously sea level)

Now my map only shows data above sea level

Now I offset the elevation vertically again and remove 100ft so we get back to real values

Now I was able to export the elevation data from the Elevation -> Export to menu

Atoll seems to like PNG 16 bit greyscale so that’s what we’ll feed it.

In Atoll we’ll select File -> Import and open the PNG we just generated.

Data type will be Altitude, Pixel size is 5m (as denoted in email / dataset metadata).

Next question is offset, which took me a while to work out…

The email has the Lat & Long but Atoll deals in WGS co-ordinates,

Luckily the GeoPlanner website allows you to enter the lat & long of the top corner and get the equivalent West and North values for the UTM dataum.

Enter these values as your coordinates and you’re sorted.

I can even able a Map layer and confirm it lines up: