CALENDAR: Presentation is due this Friday. Sources list is due NOW

OBJECTIVE:  During today's class I will be able to:

• Explain how synchronization and coordination enable the transmission of binary messages.

WORDS FOR TODAY:

• bit: A contraction of "Binary Digit"; the single unit of information in a computer, typically represented as a 0 or 1
• bandwidth: Transmission capacity measure by bit rate
• bit: A contraction of "Binary Digit"; the single unit of information in a computer, typically represented as a 0 or 1
• bit rate: (sometimes written bitrate) the number of bits that are conveyed or processed per unit of time. e.g. 8 bits/sec.
• latency: Time it takes for a bit to travel from its sender to its receiver.
• protocol: A set of rules governing the exchange or transmission of data between devices

WORK O' THE DAY: 

CALENDAR: Presentation is due this Friday. Sources list is due NOW

Let's change groups today-- Please write your student number on a partial strip (conveniently located on the supply table by the door).

Now please circle every odd number and then write the resulting number down and then get in order of that number along the back wall.

Please introduce yourself to your new team!

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We've got a coupla new terms today.... let's review those now:

Data flows through the wires of the interweb much like water flowing through a pipe... that's why we use similar terminology. We often say that a large tech company like Google has "fat pipes". In other words, a tremendous amount of data flows in and out of the wires connected to that company.

The rate at which data flows through those wires (pipes!) is called the bit rate and is measured in bits of data (0's and 1's) per second.

Sometimes when too many people try to connect to a site at once or when communication equipment fails or is overwhelmed, we might say "the pipes are clogged". What we really mean is the equipment can't handle the flow of data efficiently, so the time to process and/or transmit that data slows down.... increasing latency.

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Now let's practice using them in a sentence (skip the words that are particularly obvious to you)

Oh and by the by, latency can be a real pain in the butt... if you have a windows pc there's an easy way to check that. Any thoughts? Can we do that with a chromie?

The answer is to do a *ping*. Pinging a server on your network or on the interweb sends a very simple (32 byte) message and awaits the response from that server: *pong*. Most software doesn't show the pong anymore though.

Ping uses the TCP/IP protocol.

IP Address: In this case 98.137.246.8. Notice that I pinged 'yahoo.com'. Ping is smart enough to go out to the web, find the lookup value for the IP Address (Internet Protocol Address) for Yahoo.com and then ping that.

All PC's, phones, servers and in fact ANYTHING connected to the interweb MUST have a unique IP Address

Time is the value that most interests us in terms of latency. Time is measured in milliseconds and is usually around the low to mid double-digits. Time in the triple digits (or larger) indicates latency between you computer and the server you're pinging.

TTL = "Time To Live" isn't really a time at all. TTL is a number of hops set by your computer when you initiate the ping. Each time that ping 'touches' another server, that TTL value goes down by one. After 55 'hops' the msg above will be disregarded -- effectively killing the msg.

When pinging a server on the web to check for latency it's always a good idea to choose a server (such as yahoo) that you are certain has a lot of bandwidth. Pinging a slower/clogged server to check for latency is kinda counter-productive.

Windows computers will ping an address 4 times. Other software will ping the server until you tell it to stop.

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Assuming your pipes aren't clogged (in other words the latency is due to equipment OTHER than your computer), there are ways to check your current bit rate, how do we do that?

Try looking up DSL Speed Test

Does anyone know how that works?

DSL Speed Test is a GREAT tool to use at home if Netflix, Vudu, Hulu or some other streaming service keeps bogging....