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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Sonet protection usage
Bora Akyol wrote: > > Note that I am not a big fan of APS, but: >... > I think this is a huge oversimplification of APS and how it works. Yes APS > allows the > **operator** to backup various primaries to a backup. It allows 1:1 which is > same as diverse > circuits. This is the case of a rope that is **long enough**. > OK, since it "allows" 1:1, taking the same capacity as 2 circuits, why do you think that they charge less than for 2 circuits? Alternatively, since 2 circuits are paid for, why not use both, doubling capacity? My opinion (based on a fair number of years of experience) is that any ISP foolish enough to have bought APS should also ask proof that no other circuit is provisioned for the same APS. Once you've done that, a class action might be in order.... APS is specified to switch a failing circuit over to a backup within 50 milliseconds. It assumes that failure is in a multiplexor. It assumes that most of the circuits will be statistically idle. It assumes that the individual T3 (OC-1) paths are burstable, and can be recombined at the path or section layer. It assumes that 50 milliseconds is short relative to switching time. In short, it assumes voice. Data doesn't look like that at all! If the failure is actually due to the usual circumstances, a lot of data "circuits" fail all at once. There is no chance that they will all be backed up. APS (as sold) is a fraud on the uninformed. > Well-engineered trans-oceanic links are laid such that there are at least > two conduits running parallel > some large distance apart. > And which are those? I was unaware that any were laid that way. My information is dated on that topic, tho'. (The only one I ever viewed was pre-optical.) > Or you can run 1+1 IP Bonded interfaces and achieve the same effect ;-) > Unless it has vastly improved since I last tried it, bonding does not work well over diverse paths, due to timing differences. [email protected] Key fingerprint = 17 40 5E 67 15 6F 31 26 DD 0D B9 9B 6A 15 2C 32
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