GarrettCom Quad manual Frame Buffering and Latency

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Magnum Quad-Series Fiber Switches

Installation and User Guide (06/03)

The RJ-45 ports run at 10/100Mbps with N-wayauto-negotiation capability, whereas the fiber port runs at 100Mbps with half- or full-duplex capability manually selected. The default condition is full-duplex. Internal jumper settings allow technicians to set the 100Mb fiber port to half-duplex mode. (See Section 3.4).

On Magnum Combo Quad-port modules, there are four LED’s for each RJ-45 port, which indicate status as described for the QPM-RJ45 in Section 2.2.4 above. The fiber port is fixed at 100Mbps speed at all times, and has LEDs that indicate status the same way as described for the Fiber Quad-port modules in Section 2.2.2 above.

2.2.6Frame Buffering and Latency

The Magnum Quad-Series 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 likely when traffic is heavy, the result of store-and-forward operation is that more bandwidth is available for good packets when the traffic load is greatest.

To minimize the possibility of dropping frames on congested ports, each Magnum Quad-Series QS5116 Switches dynamically allocates buffer space from an 8 MB memory pool, ensuring that heavily used ports receive very large buffer space for packet storage. (Many other switches have their packet buffer storage space divided evenly across all ports, resulting in a small, fixed number of packets to be stored per port. When the port buffer fills up, dropped packets result.) The other two Q-Series Switches QS580 and QS5116 dynamically allocates buffer from an 4MB memory pool. This dynamic buffer allocation provides the capability for the maximum resources of the

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Contents Fiber Switches Trademarks Contacting GarrettCom, Inc GarrettCom, IncIntroduction Table of ContentsIntroduction Magnum QUAD-SERIES QPM Personal Hubs, 10Mb series Personal Switches, 10/100MbTechnical Specifications Agency Approvals Magnum Quad-Series Port Modules Ordering InformationInspecting the Package and Product Magnum Quad-Series chassis models Product Description Magnum Quad-Series Fiber SwitchesPorts Table-Top Quad-port modules, 100Mb fiber Quad-port modules, 10 MbFiber QPRJ-MSC Quad-Port Module, RJ-45 copperCombo 3 + 1 Quad Port Modules, 3@RJ-45 and 1@fiber QPM-RJ45Frame Buffering and Latency Www . GarrettCom . com „ 16-port, 12-port, 8-port and 4-port models Features and Benefits„ Plug-and-Play installation for high performance switching „ Front-mounted LEDs, world-wide AC power supplyExample 1 Magnum QS580 ApplicationsExample 2 Magnum 8-port QS5108 Example 3 Magnum 16-port QS5116 Location of 8-port Magnum QS580’s cooling fan exhaust Locating Magnum Quad-Series SwitchesCopper Connecting Ethernet MediaConnecting Fiber Optic ST-type, twist-lock Ieee Standard Media Type Max. Distance Port Module FiberConnecting Fiber Optic SC-type, Snap-In Connecting Single-Mode Fiber OpticMedia Ieee Standard Table-Top or Shelf Mounting Wall or Vertical Surface Mounting, 8-port QS580Rack-mounting, models QS5108 and QS5116 Multiple Magnum QS5116 units rack-mounted in a 23 frame Jumper Settings for HDX/FDX Fiber ports, internal jumper settings Combo ports, RJ-45 and Fiber internal jumper settings Www . GarrettCom . com 10Mbps Fiber ports internal jumper settings Powering the Magnum Quad-Series SwitchPreparation for Installing and Removing QPMs Quad Port Module QPM Installation1a Removing Chassis Cover Remove Chassis Cover1c Front View QPM Retaining Screws hold Face Plates Installing QPM Cards in the Magnum Q-Series2a Inserting QPM Cards into a Magnum QS5116 3b Removing a QPM Card Removing QPM CardsSwitching Functionality Filtering and ForwardingAddress Learning ACT Status LEDsAuto-negotiation, for Fast Ethernet copper ports PWRWww . GarrettCom . com Flow-control, Ieee 802.3x standard Auto-negotiation for 10 Mb ports, half- or full-duplex modeFiber Port Module Product Description Introduction Magnum QUAD-SERIES QUAD-PORT Modules QPMQPM-MST, 100Mb multi-mode FX-ST Quad-port Module, twist lock 100BASE-FX Single-Mode QPM-SSC 100Mbps single-mode FX-SC-type, snap-in connectorSmall-form-factor QPM-RJ45 Twisted Pair, 10/100Mb TP Quad-Port 10/100BASE-T and 100BASE-FX Combo Quad-Port Connectors 10 Blank Face Plate QPM-FPBefore Calling for Assistance When Calling for Assistance Return Material Authorization RMA ProcedureNo Problem Found B1.0 Specifications for Magnum QUAD-SERIES Switches Power Supply Internal -48 VDC OptionShipping and Packaging Information Power Supply Internal 24 VDC Option Power Supply Internal 125 or 100VDC OptionB3.0 Applications for DC Powered Ethernet Switches B4.0 Installation B4.1 UL RequirementsB5.0 Operation Magnum QS5116-125VDC B6.0 Ordering InformationTo the external Terminal Block C4.0 Features and Benefits of the DUAL-SOURCE DesignC5.0 Installation C3.0 DUAL-SOURCE OPTION, Theory of OperationC7.0 Operation C5.1 UL RequirementsC6.0 Ordering Information Example Magnum QS5116-48VDC