E3Switch DS3 Operating information manual - page 17
Chapter 7: Telecom Connections
cable which will have more consistent shielding and conduction. The maximum length of each cable shall
be 440 meters for E3 or 300 meters for T3/DS3, but the acceptable cable lengths of equipment attached to
the converter must be met as well. For lengths over 135 meters, testing in field should be used to determine
whether bit error rates are acceptable. Long cable lengths also require careful selection of cable type and
attention 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 Performance
LAN Ports
Each LAN port implements the following features to maximize LAN compatibility and link utilization and
minimize 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.
Autonegotiation
The network equipment attached to the LAN port of the converter should be set for autonegotiation
mode 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. If
crc-errors or short packet errors are seen in the management statistics of the LAN port, the attached LAN
equipment has probably configured itself to half-duplex mode and colliding packets are being lost. In such
a case, autonegotiation should be disabled on both the converter and the attached LAN equipment, with
both forced to 100BaseTX full-duplex. Autonegotiation interoperability and standards were not well
understood by the industry at the inception of 100BaseTX, resulting in some older LAN equipment not
understanding 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 not
result in the new equipment defaulting to half-duplex if set to autonegotiate. Autonegotiation must always
be enabled for 1000Mbit/s links.
LAN Cabling
It 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 Control
This converter contains approximately 500kBytes of total packet buffer. Queue utilization can be
monitored at the converter's statistics HTTP page, and buffer overflow will appear as “Rx oflow” errors at
the same HTTP page.
If the converter's packet memory begins to fill up, the converter applies flow control techniques to the
machines connected to its LANs rather than simply dropping incoming packets. For connected
100/1000BaseTX LANs the converter uses 802.3x flow control. Flow control creates a much more
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