GLOSSARY

Someone said to me once that 80% of technical knowledge was terminology.   My experience is that there is a lot of truth to declaration, though I have to say the 20% that’s left is where most of the study resides.  In any case, here is a list of terms, phrases and acronyms to help with your understanding.   This is by no means comprehensive, but as I discuss topics, I’ll add additional material to this page.

Also, I’ve put links for you to get more information if you’re interested.  Most of these links come from Wikipedia for two reasons: First, Wikipedia is a good source for more in depth descriptions of various terms.  Second, they copyright their material in a manner that allows others to freely incorporate their material as long as they get credit.

Bits and Bytes

Computers use the data unit called a  binary digit or bit, which is a unit of data that has two states, on (“1”) or off (“0”).  A 8 bit grouping of bits is a byte.  An alphanumeric character is typically encoded as a byte. Bits are usually represented in Hexadecimal, which is numeric base-16.   1,024 bits is a kilobit and is represented by kb, while 1,024 kb is a megabit is represented by Mb.  Kilo-bytes and Mega-bytes are typically represented by KB and MB respectively.  Finally, throughput is typically represented as kbps or Mbps or some number of bits per second.

File sizes are typically represented in bytes not bits, so to determine how many bytes are being downloaded, divide the bit-rate by 8 to get the byte-rate.  A quick-and-dirty method is to divide by 10, so that 20 Mbps is a little faster than 2 MBps.

Encryption

Encryption is a technology that scrambles information (plaintext)  into unrecognizable patterns according to a mathematical formula (cipher) using a seed called a key.  Decryption is the technology for returning the unrecognizable to the original readable state by applying the key.  From a  home IT perspective,  encryption/decryption is our primary method to insure that only those with authorization can read and understand data either as it’s stored on disk (at rest) or while it’s in transit.

This is a very complex topic, with all sorts of twists and turns.  For our purposes, you need to keep in mind the following:

  • Most secure encryption in this space uses Advanced Encryption Standard (AES), which is what both Secure Sockets Layer (SSL) uses for securing data flow on web connections, as well as the recommended algorithm for wireless security.
  • When we create a passcode (that’s human understandable) a very large integer is generated as the key.
  • The longer the key (in bits), the more difficult it is to crack the key using brute-force attacks.  The current standard is to use AES-256, which uses an integer with contains 32 hexadecimal characters (256 bits) as it’s key.

Internet Protocol (IP)

Internet Protocol (IP) is the low-level network protocol for packaging of data (called data packets), addressing where the packets go and routing of these addresses to the appropriate device.

IP Address

An IP address is a numerical value where the network can locate a device.   There are two naming conventions depending upon the protocol being use: IPv4 or IPv6.   For IPv4, which is still more common than IPv6, the addressing convention consists of 4 integers separated by “:”.  Each integer is a value between 0:255:

IPv4 Address Scheme (from Wikipedia)

Media Access Control (MAC) Address

The Media Access Control or MAC Address is a unique identifier assigned to a given network device.  If a computer has more than one network card (e.g., 1 Ethernet and 1 Wireless), then each will have a unique MAC Address.  This address consists of 6 groups of Hexadecimal digits separated by either hyphens “-” or colons “:”.  A typical address would look like:

01-23-45-67-89-ab

01:23:45:67:89:ab

Meta-data

Metadata is data about data.  Files, messages, databases all contain data, which is the data we routinely access and change.  They also contain data like the creation/modification/access dates and times, as well as addressing information for messages.  This is metadata.  Other metadata includes, protection information (who can access/modify the data), routing information for the messages, template information for MS Word documents and location data for photos.

Since metadata is largely out of view for the average user, it doesn’t “feel” important, yet the metadata surrounding our data can disclose much about the owners and users of that file, message or database.   For example, one can use creation time and GPS location metadata from pictures to identify where and when you were in a particular location.

Port

A port is a specific network end-point or connection for transferring data to and from a computer or device.  A port is an positive integer from 0 to 65535.  To connect to a computer, the domain address or IP address is pair with a port number.

Some ports have a default function and are known as well-known ports.   One such port is port 80, which is a default listening port for HTTP.   When a web server is listening for a connection, say http://www.msnbc.msn.com, port 80 is active and waiting for a connection.  When someone browses to that site, the initial connection is to port 80.  Since it’s for listening only, the next thing that server does is to allocate a private port to continue the connection.

For a short list of well known ports, go here.

Server

A server is a computer or a group of computers (known as a cluster) that provides application and web servers to a network.   They typically reside in a data center and are not used as a desktop or laptop.

Web server (or Web services)

This is a computer server (or server cluster) that serves web services to users.  The most common protocol is HTTP.  So, when one browses to  http://www.msnbc.msn.com, they are connecting to a web server.

Wi-Fi

Wi-Fi refers to the ability for a computer or device to be attached to the IP network via a specific wireless protocol ( IEEE 802.11 family of standards).  The term wireless  is used to mean Wi-Fi, though wireless can also mean other mechanisms, such as Bluetooth.

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