E3Switch DS3 Operating Information Manual
Also see for DS3: Operating information
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Chapter 7: Telecom Connectionscable which will have more consistent shielding and conduction. The maximum length of each cable shallbe 440 meters for E3 or 300 meters for T3/DS3, but the acceptable cable lengths of equipment attached tothe converter must be met as well. For lengths over 135 meters, testing in field should be used to determinewhether bit error rates are acceptable. Long cable lengths also require careful selection of cable type andattention to sources of external noise.Third-party fiber to copper media converters can be used with the E3Switch converter to implement fiber-optic DS3/E3 links; however, refer to the interoperability section of this document for vendors to avoid.Chapter 8: LAN Connections and PerformanceLAN PortsEach LAN port implements the following features to maximize LAN compatibility and link utilization andminimize packet loss:· Autosense/Autoconfiguration/Autonegotiation with the attached LAN.· 100Mbit/sec or 1000Mbit/s.· Full-duplex LAN connection.· Data buffering.· Upstream pause-frame flow-control messaging.· Quality of service high-priority queuing in certain firmware.· 1650-byte packet acceptance (1350 for mgmt and 9600 for jumbo).These features and their ramifications are discussed below in more detail.AutonegotiationThe network equipment attached to the LAN port of the converter should be set for autonegotiationmode in order to allow the converter to negotiate a 100Mbit full-duplex connection.There are rare cases with older LAN equipment in which it may be necessary to disable autonegotiation. Ifcrc-errors or short packet errors are seen in the management statistics of the LAN port, the attached LANequipment has probably configured itself to half-duplex mode and colliding packets are being lost. In sucha case, autonegotiation should be disabled on both the converter and the attached LAN equipment, withboth forced to 100BaseTX full-duplex. Autonegotiation interoperability and standards were not wellunderstood by the industry at the inception of 100BaseTX, resulting in some older LAN equipment notunderstanding the converter's autonegotiation advertisement of strictly full-duplex capability.It is highly desirable to leave autonegotiation enabled so that changing attached LAN equipment does notresult in the new equipment defaulting to half-duplex if set to autonegotiate. Autonegotiation must alwaysbe enabled for 1000Mbit/s links.LAN CablingIt is important to use the correct cabling for proper operation. Use UTP Category 5 network cable with RJ-45 connectors for the LAN ports, and do not exceed 100 meters (328 feet) in length. Either a straight-through or crossover cable may be used.LAN Buffering, Loading and Flow ControlThis converter contains approximately 500kBytes of total packet buffer. Queue utilization can bemonitored at the converter's statistics HTTP page, and buffer overflow will appear as “Rx oflow” errors atthe same HTTP page.If the converter's packet memory begins to fill up, the converter applies flow control techniques to themachines connected to its LANs rather than simply dropping incoming packets. For connected100/1000BaseTX LANs the converter uses 802.3x flow control. Flow control creates a much more17 |
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