Hi CB,
Interesting question, because it begs the question: What's a "backbone?" Of course, there is no single commonly accepted answer once you depart from the most pronounced type of spinal interconnect, rather, just a general agreement by all to use it in a vague sort of way.
>>I know that part of the backbone is located around here. This may be a dumb question, but is there any way to actually look at it? <<
I'll limit my message mostly to the context of wide are network (WAN) backbone considerations.
The term "backbone" itself is interesting, since the elements which make one up, and what they do, have evolved with technology, along with what we have come to expect from one.
Prior to the advent of fiber and TCP/IP networks [and even to this day in many cases], a backbone was a linear excursion on a diagram, representing the path of a cable route with branching taking place tree and branch style at various intervals. There are still plenty of these linear types of backbones in existence today, some supporting private networks, and many are pre-SONET type telco and cable tv networks.
If a backbone or "spine" was damaged or cut for any reason, like a backhoe accident called "backhoe fade," a "spare" backbone would be switched into service to take its place through a mechanism known as an automatic protection switch, or APS.
This means that if I had a backbone circuit between NY and LA that failed, say, I would have to have a spare standby circuit ready in the wings to switch into action during a cable outage.
"Spine" was actually the preferred, probably the original, term in some segments of the industry to connote the existence of a backbone cable system, especially in commercial buildings, since the vertical cabling system actually resembled a human spine with its radiating elements on every floor.
SPINES, BACKBONES, CIRCLES, RINGS, INTERLOCKS
But what happens to the term "backbone" when we begin to introduce circular topologies, like today's SONET rings? It no longer looks like a spine, nor does it operate like a traditional backbone in the same wayany longer.
Ring topologies come in many different flavors and textures. Some single fiber, some two-fiber, some are four fiber, etc. Is it still a backbone or spine if it is shaped like a ring?
Today's physical fiber rings consist of two or four fiber strands apiece (or, more recently, wavelengths in some instances which are hopefully hosted by different strands) that can "heal themselves." They are thus said to be "self-healing" through a method involving "signal -loss detection and loopback activation" at nodes which are adjacent to the fiber cut, in the event of a fiber break or node outage.
Further, several of the circular rings can be "interlocked" to form interlocking rings, or a ring of rings, as it were, and they collectively may look like anything BUT a backbone! Such a set of interlocking rings could actually resemble the geographic boundaries of the 48 contiguous states, for example. constructed so that, say, fiber was installed along each of the boundaries, and each state had its own ring, with interlocks on the east, north, west and south to each neighboring state's ring.
These, in our make-believe carrier, could easily be collectively referred to as a national backbone with dozens of nodal interlocks.
Like ahhaha says, there usually is no distinguishing characteristic to enable you to actually "look at" one of these beasts when you are in the proximity of one. Some exceptions may be tell tale signs like a string of orange signs out in the boon docks or on someone's private property rights that say "call before you dig." Then you can be sure that you are either near a fiber backbone route, or a gas line, or such... or multiples of these! In any event, you don't want to dig there.
Fiber backbones are usually laid in 4" conduits when placed along active thoroughfares, or may be "buried direct" in some cases. The type of conduit is determined in some cases by the pH value of the soil. PVC, fiberglass and stainless steel are some options, with PVC being the cheapest and most pervasively deployed.
Your chances of being next to a backbone increase if you are near a main interstate railroad route, or riding in an automobile on a larger thruway or highway, or when you go over bridges ot through tunnels between main bodies of populated land.
They will be in one of those pipes along the under-railing of the bridge, or hidden in the utility cavity between the two directions of a larger tunnel.
They have even been installed along water main and sewerage routes, but I doubt seriously if you would want to explore for one there.
Backbones tend to blend in with local communications feeder and distribution cable routes, the closer you get to an urban center. I hesitate to stipulate that you will never see a backbone strung overhead. My hesitation is due to my uncertainty as to what exactly makes up a backbone in the first place!
All of this raises another set of questions, and that is: Just how extensive and supportive of subordinate tributaries does a cable route have to be before it can legitimately qualify as a "backbone?" [even if it isn't a straight line, and looks like a bunch of inter-locked circles?]
As you can see, the term backbone, upon inspection, is often left to interpretation. |
