E3Switch WAN Monitor Operating Information Manual - page 15
Chapter 6: Interoperability
Chapter 7: Telecom Connections
Framing and Physical Link
The unit can monitor a variety of E3, T3/DS3 links (with the appropriate media Monitor) such as fiber
optic, microwave radio, laser, copper, satellite, or a combination. The Monitor may be used with a standard
(i.e., M13, M23, clear-channel, C-Bit or G.751) framed or unframed, full-rate E3 or T3/DS3 link with AMI
and HDB3 or B3ZS encoding. C-Bit framing is recommended for DS3 links. The Monitor will report
PMDL Circuit ID present on C-Bit links.
Each Monitor regenerates the timing clock of the received TDM bit-stream, within E3 and T3/DS3
standards. High-accuracy receive clock rates are displayed at the unit's HTTP management page.
Telecom Cabling
For the E3 or T3/DS3 connection, 75-ohm coaxial cables with BNC connectors are required. It is important
that 75-ohm cable be used and not 50-ohm cable. For long connections or in electrically noisy
environments it may be important to use a high-quality 75-ohm 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 Monitor 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 Monitors can be used with the E3Switch Monitor 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 data rates (1000Mbit/s via SFP or if GbE upgrade purchased).
•
full-duplex LAN connection.
•
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 Monitor should be set for autonegotiation
mode in order to allow the Monitor 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 Monitor 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 Monitor's autonegotiation advertisement of strictly full-duplex capability.
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