What I expect is that it's a combination of size if you want any real range, and basically positioning and orientation. In some cases, yes, you can easily move the node... but then you have to spend days or weeks, depending on the node and where you moved it to, getting the thing to talk to the other nodes again. And the hardware and software necessary to keep it connected real time while being moved would likely add a factor of size and complexity as well, certainly more than most Fen would be willing to fuss with for a node that's normally relatively stationary.
Many ships (such as the Blue Midget fleet of JMC) may ship with Interwave nodes onboard... but those nodes are also not designed explicitly to be 'backbone' nodes, if only because they're in more or less a constant state of motion. They can require at least one computer-steerable transmitter and receiver, or a decent fixed antenna on small installations such as cars. And the connection is not going to be reliable enough to get the large amount of bandwidth required to be a backbone system.
JMC base facilities, such as Green Planetoidy and the 'main' office in Serenity Valley, do have true backbone nodes, but they are usually regarded as being immobile because of their relative complexity, being tied into multiple pre-aimed emitters and receivers on the outside surfaces of the station, having multiple redundancy, and whole set of 19U hardware racks loaded to the gills with 'waved hardware, which can also be hard to justify in terms of space in a moving spacecraft.
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"You know how parents tell you everything's going to fine, but you know they're lying to make you feel better? Everything's going to be fine." - The Doctor
Many ships (such as the Blue Midget fleet of JMC) may ship with Interwave nodes onboard... but those nodes are also not designed explicitly to be 'backbone' nodes, if only because they're in more or less a constant state of motion. They can require at least one computer-steerable transmitter and receiver, or a decent fixed antenna on small installations such as cars. And the connection is not going to be reliable enough to get the large amount of bandwidth required to be a backbone system.
JMC base facilities, such as Green Planetoidy and the 'main' office in Serenity Valley, do have true backbone nodes, but they are usually regarded as being immobile because of their relative complexity, being tied into multiple pre-aimed emitters and receivers on the outside surfaces of the station, having multiple redundancy, and whole set of 19U hardware racks loaded to the gills with 'waved hardware, which can also be hard to justify in terms of space in a moving spacecraft.
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"You know how parents tell you everything's going to fine, but you know they're lying to make you feel better? Everything's going to be fine." - The Doctor