Comment meaning of the term Packet switch. (Score 2) 64
Lynx's switch is really a circuit switch and not a packet switch. Let me explain why.
The term Packet Switching commonly refers to statistical multiplexing of packets onto a lower layer channel like say a single WDM channel or a SONET stream. For statistical multiplexing, you need buffers at input or output ports because if two packets arrive at the same port at the same time, one of them has to be buffered while the other is being transmitted. Thus, the common usage of the term optical Packet Switching implies optical buffering and optical processing available in the switch. In other words, its like an optical implementation of a packet switch like an IP router or a cell switch like an ATM switch.
In contrast, these "photonic switches" in the market like those of Lynx are like circuit switches (like TDM swictches used to set up circuits in telephony.) There is no buffering and statistical multiplexing and intelligent forwarding features. The switch may of course still have to do opto-electronic conversion and look at the "packet" or "frame" headers to determine the incoming and then outgoing port numbers. But remember that this makes your switch dependent on the bit rate, clock timing and protocol format.
In contrast, pure wavelength switching (WDM switching) as opposed to this all-optical "packet switching" is totally independent of bit rate, clock timing and protocol format. You are switching light wavelengths and not packets here. This is one of the major advantages of WDM networks since their capacity can be dynamically upgraded in response to customer demand by just upgrading, i.e. adding more wavelengths or increasing bandwidth per wavelength channel - you don't have to go visit every node in your network core and upgrade all the equipment. This advantage is not available if you made your network out of these optical packet-switches like those of Lynx.
All said, wavelength switching and optical "packet-switching" are not necessarily competing technologies. The former is more suited to backbones and long haul networks..while the latter is more suited to local and metropolitan areas.
Note that I wrote "packet switching" in quotes here.
The term Packet Switching commonly refers to statistical multiplexing of packets onto a lower layer channel like say a single WDM channel or a SONET stream. For statistical multiplexing, you need buffers at input or output ports because if two packets arrive at the same port at the same time, one of them has to be buffered while the other is being transmitted. Thus, the common usage of the term optical Packet Switching implies optical buffering and optical processing available in the switch. In other words, its like an optical implementation of a packet switch like an IP router or a cell switch like an ATM switch.
In contrast, these "photonic switches" in the market like those of Lynx are like circuit switches (like TDM swictches used to set up circuits in telephony.) There is no buffering and statistical multiplexing and intelligent forwarding features. The switch may of course still have to do opto-electronic conversion and look at the "packet" or "frame" headers to determine the incoming and then outgoing port numbers. But remember that this makes your switch dependent on the bit rate, clock timing and protocol format.
In contrast, pure wavelength switching (WDM switching) as opposed to this all-optical "packet switching" is totally independent of bit rate, clock timing and protocol format. You are switching light wavelengths and not packets here. This is one of the major advantages of WDM networks since their capacity can be dynamically upgraded in response to customer demand by just upgrading, i.e. adding more wavelengths or increasing bandwidth per wavelength channel - you don't have to go visit every node in your network core and upgrade all the equipment. This advantage is not available if you made your network out of these optical packet-switches like those of Lynx.
All said, wavelength switching and optical "packet-switching" are not necessarily competing technologies. The former is more suited to backbones and long haul networks..while the latter is more suited to local and metropolitan areas.
Note that I wrote "packet switching" in quotes here.
