IT for Radio Engineers


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As engineers, part of your role is to find creative methods to achieve a certain result. You do this for the most part because there is not a commercially viable solution available, or maybe there is a solution but the budget doesn't allow it. For myself, and most of the engineers I knew back in the day, this was the stuff we lived for, making the impossible happen and actually having it work. Give us the roll of solder, a few components, wire, a metal box and voilà: a fix for a problem!

We have all been in the situation where you start working for a new station and come across the myriad of home-made devices that seem out of place, but obviously address a particular problem. We have always had a toolbox of tricks and solutions that could be whipped together. Today, many of the clunky boxes that served us so well in the past have been replaced by networked hardware and software systems, which, while providing a far more powerful and compact platform to fill the operational needs of a facility, now take the form of black-boxes and software files. (The tools you use no longer came from a metal cabinet.)

There are libraries of software designed to address many situations, most of it free or for a small charge. You can also write your own applications, but before you take on such a task, it might be helpful to have a better understanding of how data is transported in a networked environment, what to expect in the future, a more reliable way to connect over the network, and maybe throw in a few tips and tools along the way.

Net Tool Series II from Fluke

Ethernet testers, such as the Net Tool Series II from Fluke, are the modern handheld test tool in an IT-based facility.

In many ways, transporting digital audio around the station, or anywhere else for that matter, has been made much simpler through Ethernet networking. I will discuss a new protocol (IPv6) that plays an important role in the transport of streaming data and a relatively old protocol (IP Tunneling) that perhaps could be one of the most useful tools in terms of creating both reliable and secure IP connections between devices. But first, a review of IP.

IP review: The basics

Internet protocol (IP) is the reason we can transport any type of data file through a local network or even the Internet. The IP establishes the method by which data is packaged and identified on the network; Transport Control Protocol (TCP) defines the method used to transport the IP from one point to another. Hence the acronym TCP/IP that describes how data gets packaged and routed through a network. As with most protocols in networking, these (and other) protocols are based on a set of layers that define the physical connection, transport methods, data packaging and error correction aspects of the protocol. These layers each have a specific job and are designed to work with the other layers above or below it. Layering also gives us a great deal of flexibility to upgrade to new standards while preserving compatibility with other protocols.

The IP address is a unique 32-bit sequence divided into four separate four-byte numbers or octets separated by periods. Each four-byte number ranges from 0 to 255 (aaa.bbb.ccc.ddd).

An organization called Internic is responsible for assigning these addresses with the intention of making sure every terminal device on the Internet has a unique address. The available addresses are further categorized into classes based on the amount of users needing a contiguous address, i.e. a cable provider serving thousands of users needs a large block of addresses to assign to users. The three classes are:

Class A - Addresses assigned to the first octet “aaa” in the range of 0-126. For example, an address beginning with 110.xxx.xxx.xxx is considered a class A address. This class can accommodate 126 different networks with up to 16 million separate hosts.

Class B - Utilizes the first two octets for the network ID and the last two for the host ID. The first two octets will always have an address between 128.000.xxx.xxx and 191.255.xxx.xxx yielding 16 thousand possible networks, each with 16 thousand possible hosts.

Class C - Uses the first three octets for the network ID and the last for host ID. The first three octets with always have addresses between 224.000.000.xxx and 239.255.255.xxx yielding 2 million possible networks and up to 254 hosts for each network.

Each class also has reserved addresses used only for establishing connections that do not go to the Internet. For example, the network in your office or home probably uses an address in the range 192.168.0.0 and 192.168.255.255. This is the range reserved for local connections in class C networks. If the local network has more than 255 users, then there are also reserved ranges for class A and B that accommodate larger amounts of users.

However, in most large company networks the smaller groups are usually divided into individual subnetworks that are grouped into a single larger network.

To reduce the need to assign every device on a network its own IP address, most routers use a technique called Network Address Translation (NAT). Let's say you send an e-mail message from your company computer to a computer in another company's office: from an IP perspective, the data leaves your PC on a local IP address. When it goes through the router, the data is sent on the IP address assigned to the specific office. When it arrives at the destination office, the router reassigns the data to the IP address of the intended recipient. NAT is the protocol that gives routers the ability to recognize IP data packets intended for a specific device and route them properly.



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