Monday, September 17, 2007

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Como en este blog hablo de todo y no solo de filosofía... y como soy Ingeniero y me dedico a las Telecomunicaciones (que por cierto me fascina este campo).... Aquí encontré una comparación entre las tecnologías ópticas de 10 Gbps Ethernet, es cortesía de Richard A Steenbergen.


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Besides the obvious differences of size/form factor and fiber connectors,
XENPAK and XFP are very different technologies on the backend.

The biggest difference for the end user is that on XENPAK the framer is
located on the optic itself, which essentially makes that optic "hard
coded" for a particular media and framing. XFP implements the framer on
the host board, making the optic itself media agnostic (not to mention
cheaper to produce). You can take the same XFP and use it for 10GE LAN
PHY, 10GE WAN PHY, OC192, even 10G fibre channel. Generally speaking this
means that any vendor producing anything less than an extremely low-end
device can easily implement LAN/WAN PHY framing on the board, and control
it via a simple software switch. I can only speak to the 10G XFP cards on
the MX960 specifically, but they implement LAN/WAN PHY support about as
well as you could possibly hope for (with full SONET alarms when in WAN
PHY mode). With XENPAK, you have to change out the entire optic, and you
usually end up paying a huge premium for "LW" optics (and good luck even
trying to FIND EW).

The other major difference is the interconnection technology used. XENPAK
uses XAUI, which is four (4) lanes of 3.125G serial interfaces, while XFP
uses XFI which is a single 10.3125G channel. The use of XAUI makes XENPAK
"naturally suited" to some exotic "4 lane" technologies such as LX4 and
CX4, which split the 10G signal into 4 individual lower speed signals. In
the case of LX4 for example, 4 slightly different colored wavelengths and
an integrated mux/demux are used to provide WDM, allowing you to get much
longer distances over old low-grade MMF plant than you could possibly get
with a single native 10G interface. Since XFP uses a single 10G channel,
you won't find LX4 optics and the like produced.

Generally speaking XFP is superior to XENPAK technically, and is cheaper
to produce, but you'll find a lot of existing hardware that is still
XENPAK based. The only other 10G optic technology still in production to
have any market penetration is X2, which is essentially XENPAK technology
in a smaller form factor (closer to original GBIC size).

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