4K24C, 10/100 F/H Dual-Speed Switched Ports; Frame Buffering And Latency - GarrettCom Magnum 4K24F Installation And User Manual

Magnum 4K24 Switches Installation and User Guide
2.2.5 4K24C, 10/100 F/H dual-speed switched ports, RJ-45 (copper only)
The Magnum 4K24C copper has 24 ports that are dual speed 10/100Mb
switched RJ-45 ports Auto-negotiating. The 10/100Mb switched ports are independently
Magnum 4016C Switch
Power
N-way auto-negotiating for operation at 10 or 100Mb speed in full- or half-duplex mode
(as a default setting). They independently move to half-duplex mode at 10 Mb or at
100Mb speed if the device at the other end of the twisted pair cable is half-duplex or is
not an auto-negotiating device.
There are three LED's for each port. The LK/Act (Link/Activity) steady ON
indicates Link with no traffic, and blinking indicates the port is receiving and
transmitting. The Speed LED indicates operation at 100Mb speed when ON and at 10
Mb speed when OFF (when auto-negotiation is enabled). The Fdx/Col LED is ON to
indicate full-duplex operation and OFF to indicate half-duplex mode and collisions. A
twisted pair cable must be connected into each RJ-45 10/100Mb port and a proper Link
(LK lit) must be made with the device at the other end of the cable in order for the LEDs
to provide valid indications of operating conditions.
2.2.6

Frame Buffering and Latency

The Magnum 4K24F or 4K24C are store-and-forward switches. Each frame
(or packet) is loaded into the Switch's memory and inspected before forwarding can
occur. This technique ensures that all forwarded frames are of a valid length and have
the correct CRC, i.e., are good packets. This eliminates the propagation of bad packets,
enabling all of the available bandwidth to be used for valid information.
While other switching technologies such as "cut-through" or "express" impose
minimal frame latency, they will also permit bad frames to propagate out to the Ethernet
segments connected. The "cut-through" technique permits collision fragment frames,
which are a result of late collisions, to be forwarded to add to the network traffic. Since
there is no way to filter frames with a bad CRC (the entire frame must be present in order
for CRC to be calculated), the result of indiscriminate cut-through forwarding is greater
traffic congestion, especially at peak activity. Since collisions and bad packets are more
www GarrettCom com . .
Col/FDX
Col/FDX
Link/Act
Link/Act
100M
100M
2 4X 6 8 10 12 14
1X 1 3X 5 7 9 11
8
(10/04)
16 18 20 22 24
13 15 17 19 21 23