Chapter 11: AWS Directory Service, Cloud Directory

May 12, 2017

"Name or Number please?"

So the 1st telephones systems were point to point, and then hub and spoke. You rang the local exchange, asked to talk to Auntie Jill and the "operator" (think the Matrix) would ring Auntie Jill's phone and connect you (literally with a patch cord) once Auntie Jill had answered. If you wanted to talk to someone not on the local network the operator would call another operator (how did they know which one?) and ask to them to connect and you would eventually get patched through. This was even more fun if you wanted to ring someone overseas, as you would hear the patchwork of operators, some speaking foreign languages (what fun), the the sounds getting fainter and weirder (lots of clicks, "undersea" sound effects like talking down a tube, echos, etc) until finally you heard Auntie Jill's voice saying "hello?" and you could talk to them (which was expensive, and the operators would sometimes break in and say "that's another dollar total $30 etc"). You could even make collect calls where they asked the person you were calling if they would pay for the call before connecting you.

At some point numbers took over names, so you had to know the number you wanted to call (including country and area codes), or being able to look up the number in a phone directory (which was only local, you could go down the local post office and they would have a bigger range of phone directories if you needed to ring someone in another city). But typically you could ring the operator and given them a number, or if you didn't have it, ask for a number.

The special operator was called a "Directory service", they would ask for the name and city/country and address and give you the number or connect you directly.

http://blog.dialpad.com/blog/the-life-of-a-call-part-one-the-historical-telephone

The telephone operators song!

With trunks and toll and telegrams
and all exchanges too,
just telephone
and we will put you through.
Ring ABErcorn or ARChway.
Ring MAYfair, HOP or SLOane.
Ring anywhere:
we're waiting on your phone.
Do you want a little warning
to make you get up in the morning?
Is your house on fire?
Do you want to send a wire?
Just lift up the receiver.
That's all you've got to do
to telephone
and we will put you through.

With dial phones came dial signals.

Here's how to use a new fangled dial phone in the 1950's!

And this.

Before valves, transistors or integrated circuits came relays. Relays are electromechanical devices that were used for computers and telephone exchanges.

The use of relays for the logical control of complex switching systems like telephone exchanges was studied by Claude Shannon, who formalized the application of Boolean algebra to relay circuit design in A Symbolic Analysis of Relay and Switching Circuits. Relays can perform the basic operations of Boolean combinatorial logic. For example, the boolean AND function is realised by connecting normally open relay contacts in series, the OR function by connecting normally open contacts in parallel. Inversion of a logical input can be done with a normally closed contact.

They made a cool "clickety click" noise.

Auckland university has a nice page on electromechanical computing.

When I was a teenager I lived in a small country town in New Zealand. We still have "party lines" and an operator to connect calls. Our number was 334s and we had to listen carefully to make sure the morse code ring was "s" not another letter which other parties had on the same line (e.g. 334w). To make a call you had to pick up the phone and check that no one was talking and then dial (how did we dial the alphabetic part? Maybe you had to call the operator call the time).

In the late 1970's they upgraded the telephone exchange from party lines and operators to fully automatic dialling and disposed of all the boxes and boxes and relays.

This quote explains:

The End of Electromechanical Switching

By the 1970s it was clear that the days of the electromechanical switch were numbered, because in 1965 AT&T had installed the first electronic switch, the #1 ESS (Electronic Switching System) in a local exchange in Succasunna, New Jersey. (The #1 ESS was an analog electronic switch; digital telephone switches came later.) Because its operations involved no mechanical motions, electronic switches were faster and easier to maintain. And because electronic switches were essentially special purpose computers, they were more flexible, and could allow for advanced features such as call waiting. But through its long history, automatic electromechanical switches, by reducing costs, decreasing labor requirements, and increasing efficiency played a major role in making the telephone a wide spread, almost ubiquitous technology.

Somehow I had heard that they were getting rid of the relays and asked for them to be delivered to my house. They were dumped off in our driveway one day (without my parents knowledge). There was a lot of them, and they weighed about a tonne. I arranged for them to be delivered to my high school science lab where I started doing experiments to see if I could build simple computer circuits (e.g. flip flops) using them. I could, but when I worked out many I would need to do something useful (e.g. add 2 x 4 bit numbers) and how much power this would need I gave up. I have no idea what happened to them :-) I can't even find a photo of similar relays, there were about 20 in a long metal box. This is close but not actually them.

So back to directory services via operators and telephone exchange relays. I actually had/have no idea what directory services are in the context of software systems so needed to work out what I knew before I could work out what I didn't know. I do know about service registries, for service publication and discovery (E.g. UDDI etc). Are they similar?

I'm guessing that based on the telephone background however, that a directory service is a service (broker) for finding out something that you don't know. Or for getting connected to something that you can't connect to? But what, why and how? How does information get published into it? Looked up? Managed? Secured (e.g. silent numbers, secret operators - this is how hacking the telephone system started in the 1960's! Hackers worked out "hidden" area codes and rang numbers at random until they found the secret government operators who would assume you were supposed to be there and would connect you to anyone - the president? certainly sir). This was originally called Phreaking (but became known as Hacking).

AWS Directory Service supports multiple different services. Here's the documentation to choose which:

Amazon Cloud Directory is a cloud-native directory that can store hundreds of millions of application-specific objects with multiple relationships and schemas.

When to use

Amazon Cloud Directory is a great choice when you need to build application directories such as device registries, catalogs, social networks, organization structures , and network topologies. For more information, see Amazon Cloud Directory.

Amazon Cognito is a user directory that adds sign-up and sign-in to your mobile app or web application using Amazon Cognito User Pools.

When to use

You can also use Amazon Cognito when you need to create custom registration fields and store that metadata in your user directory. This fully managed service scales to support hundreds of millions of users. For more information, see Creating and Managing User Pools.

AWS Directory Service for Microsoft Active Directory (Enterprise Edition) is a managed Microsoft Active Directory hosted on the AWS cloud. It provides much of the functionality offered by Microsoft Active Directory plus integration with AWS applications. With the additional Active Directory functionality, you can, for example, easily set up trust relationships with your existing Active Directory domains to extend those directories to AWS services.

If you are in the Frankfurt region, you can use Microsoft AD to enable multi-factor authentication by integrating with your existing RADIUS-based MFA infrastructure to provide an additional layer of security when users access AWS applications. For more information, see Enable Multi-Factor Authentication for AD Connector.

AWS Directory Service for Microsoft Active Directory (Enterprise Edition) does not support fine-grained password polices.

When to use

Microsoft AD is your best choice if you have more than 5,000 users and need a trust relationship set up between an AWS hosted directory and your on-premises directories. For more information, see Microsoft Active Directory.

AD Connector is a proxy service for connecting your on-premises Microsoft Active Directory to the AWS cloud without requiring complex directory synchronization or the cost and complexity of hosting a federation infrastructure.

AD Connector forwards sign-in requests to your Active Directory domain controllers for authentication and provides the ability for applications to query the directory for data. After setup, your users can use their existing corporate credentials to log on to AWS applications, such as Amazon WorkSpaces, Amazon WorkDocs, or Amazon WorkMail. With the proper IAM permissions, they can also access the AWS Management Console and manage AWS resources such as Amazon EC2 instances or Amazon S3 buckets. You can also use AD Connector to enable multi-factor authentication by integrating with your existing RADIUS-based MFA infrastructure to provide an additional layer of security when users access AWS applications.

With AD Connector, you continue to manage your Active Directory as usual. For example, adding new users, adding new groups or updating passwords is all accomplished using standard directory administration tools with your on-premises directory. Thus, in addition to providing a streamlined experience for your users, AD Connector enables consistent enforcement of your existing security policies, such as password expiration, password history, and account lockouts, whether users are accessing resources on premises or in the AWS cloud.

When to use

AD Connector is your best choice when you want to use your existing on-premises directory with AWS services. For more information, see Active Directory Connector.

Simple AD is a Microsoft Active Directory–compatible directory from AWS Directory Service that is powered by Samba 4. Simple AD supports commonly used Active Directory features such as user accounts, group memberships, domain-joining Amazon Elastic Compute Cloud (Amazon EC2) instances running Linux and Microsoft Windows, Kerberos-based single sign-on (SSO), and group policies. This makes it even easier to manage Amazon EC2 instances running Linux and Windows, and deploy Windows applications in the AWS cloud.

Many of the applications and tools you use today that require Microsoft Active Directory support can be used with Simple AD. User accounts in Simple AD can also access AWS applications, such as Amazon WorkSpaces, Amazon WorkDocs, or Amazon WorkMail. They can also use AWS Identity and Access Management roles to access the AWS Management Console and manage AWS resources. Finally, Simple AD provides daily automated snapshots to enable point-in-time recovery.

Note that you cannot set up trust relationships between Simple AD and other Active Directory domains. Other common features not supported today by Simple AD include DNS dynamic update, schema extensions, multi-factor authentication, communication over LDAPS, PowerShell AD cmdlets, and the transfer of FSMO roles. Please ensure that any required applications or features installed with Simple AD are fully compatible with Samba 4. For more information, see https://www.samba.org.

When to use

In most cases, Simple AD is the least expensive option and your best choice if you have 5,000 or less users and don’t need the more advanced Microsoft Active Directory features. For more information, see Simple Active Directory.

For information about the AWS Directory Service API, see the AWS Directory Service API Reference.

What sort of data can be stored in them? How do you access it and why? How is this different to say a graph database???

An intro to Directory Services.

Which points out that DNS is a directory service, so I do know about at least one already.
And on UNIX they were called Network Information Services or name services rather than directory services.

A blog on AWS Cloud Directory

Directory services look like things that System Admins need to know about, which is probably (fortunately) why I don't ;-)

But Cloud Directory actually looks more generally useful.

What are core use cases for Cloud Directory?

Customers can use Cloud Directory to build applications such as IoT device registries, social networks, network configurations, and user directories. Each of these use cases typically needs to organize data hierarchically, perform high-volume and low-latency lookups, and scale to hundreds of millions of objects with global availability.

So I guess it's more like a general purpose NoSQL database for hierarchical classification problems.
I.e. The schema is extensible like NoSQL databases.

A deep dive webinar with some examples.

It handles multiple hierarchies per directory (I guess that's good, I've never liked one taxonomy for everything).

We've come full circle again with database history, as hierarchical databases were the 1st databases invented.

PS
Forgot about Phone Books! No, not books about phones, but books of names and number in order to use phones, i.e. just phone directories. See videos about for their first introduction along with auto dialing phones. You looked up a name and found the number to dial (before contacts on your mobile). Public phone boxes used to have them chained up. More recently public phone boxes in the UK have become popup libraries for normal books,

What are phone books still useful for? Monitor stands (tick), physics experiments? Yep. Can you pull two interleaved phone books apart? Depends on what's pulling them. Hint: Try Tanks. See MythBusters, part 1 and part 2 (tanks!) It takes 3.6 tonnes of force, not bad.

And don't forgot tricks of manliness (sorry, personliness!). But surely you can't tear a phone book in half with your bare hands?!