Ancient Modern Communications
Even something as newfangled as SIP carries with it the mustiness of ancient times.
I live in what has been called the last eastern city in the United States -- Saint Paul, Minnesota. Our houses are old (I live in a 109-year-old Victorian), our roads are curvy (we have avenues that intersect avenues), and quite a few of our garages began their lives as horse barns. Still, despite the turn-of-the-last-century charm that can be found throughout the city, we do have electricity, indoor plumbing (albeit not always the best water pressure), and paved roads.
However, come spring and the winter thaw, potholes open up across the city that shed light on the city's less sophisticated and not too distant past. Take a look under the multiple layers of asphalt that blanket our streets and you will find red clay bricks or better yet, glacier-rounded cobblestones. While the tires on my car aren't particularly fond of these archeological finds, I love the seasonal glimpses we get into our city's past. I am reminded that what we think of as new and exciting today, will be seen as out-of-date and archaic tomorrow.
Take a good look at modern communications systems and protocols and you will uncover similar relics of history. Even something as newfangled as SIP carries with it the mustiness of ancient times. For example, every SIP request or response ends with a blank line. While this may not look all that odd if you were to visually inspect a SIP message, a packet tracing tool such as Wireshark shows you that a blank line is made up of two ASCII characters -- the carriage return (hexadecimal 0x0D) and a line feed (hexadecimal 0x0A).
Those of you old enough to have taken a typewriting class in high school will remember that when you reached the end of a line you would take hold of the return lever and throw it to the left. Not only did this bring you back to the margin (carriage return), it advanced the paper to the next line (line feed). This means that inside every single SIP message you have something that dates back to a mechanical procedure that originated in the early 1800s. So much for being cutting edge.Dial Tone
This 'old meets new' aspect can be found in a number of other components of communications. Consider the sound you hear every time you lift a telephone receiver from its cradle. Dial tone was invented way back in 1908 as a way to tell the telephone user that he or she had successfully connected to the phone company. Although it took a while to gain widespread adoption across the world, by the late 1940s and early 1950s, dial tone was the norm for all telephones.
Well, here we sit in the year 2015 and dial tone is still the "comfort sound" of analog, digital, and IP telephone systems. We have managed to learn to live without it on cell phones and soft clients, but it's expected everywhere else. You pick up a handset or press hands-free, and that 1908 hum still comes out at you.
While some new IP telephones create dial tone within the telephone itself, many rely on older media resources within the communications system to do it for them. Those resources are engaged when the handset is lifted and stick around until a media stream is established with the called party. So, even SIP phones sometimes need a little old fashioned TDM boost to get the ball rolling.Pennsylvania 6-5000
Everyone is familiar with the fact that dial pad buttons on telephones have both a number and three-to-four letters. The letters "abc" are assigned to the number 2, "def" to the number 3, and so on.
Long before electronics and software, telephone exchange buildings were dedicated to circuits that began with the first two or three digits of a seven-digit telephone number. When I was a kid growing up in Scottsdale, Ariz., my telephone number was Whitney 5-2497 where "Wh" mapped to the numbers 9 and 4. I am not sure when letter and number combinations ceased to exist, but for many years that was the "number" that was printed on the telephone itself and the "number" I gave out to my friends.
For reasons dating back to rotary telephones and pulse dialing, the number 1 has no letters. A single pulse could be a disturbance or noise spike on the line and they didn't want the exchange that served 1x to be inundated with erroneous calls.
Despite the elimination of the hard-wired local exchanges, those letters stuck around, but these days we employ them in a way that was never intended. Instead of telephone prefixes, the letters are now used to create clever mnemonics to help us remember numbers. For many people, 1-800-Got-Junk is a lot easier to remember than 1-800-468-5865.
Of course, with the advent of directories and click-to-call interfaces, the notions of remembering and dialing telephone numbers (mnemonics or not) are quickly becoming obsolete. These days, we open up a contacts list, select a name, and press "dial." In fact, it has gotten to the point where I no longer pay attention to telephone numbers. I have worked at the same company for over five years, and I doubt I know more than two or three of my coworker's telephone numbers. Why should I memorize numbers when the tools are so easy to use? There is enough clutter in my brain as it is.The King is Still Not Dead
Who remembers the old Saturday Night Live sketches about the never-ending death of the former dictator of Spain, Francisco Franco? I have been in telecom long enough to know that despite all the changes we've gone through, there are skeletons in the closet that refuse to go away. We now have instant message, WebRTC, video chat, and the omnipresent cloud, yet we still hang onto technologies pioneered by Alexander Graham Bell. We have Unify Circuit, and we still have 100-year-old dial tone. We have wide-band Opus, but the 1972-developed G.711 is far more common.
If there is one lesson to learn from this it's that every step forward carries with it many of the steps we've previously taken. Some technologies supplant the ones that came before them, while most simply build upon a well-established base. Knowing where you came from will make you more aware of where you are and where you want to be. Keep that in mind the next time you take a phone off-hook and hear that time-worn hum.
So, who's up for a little tip and ring?
Andrew Prokop writes about all things unified communications on his popular blog, SIP Adventures.