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Chapter 5: Operating Modes and Configuration
DS3/E3 Return to Service delay
The return-to-service delay prevents network topology thrashing if a telecom link is flapping up and down.
Some telecom carriers will interrupt service for 50msec, once per day as a link test. A configurable, failure-
time setting to prevent such tests from triggering a link-down, retun-to-service delay.
To exit the return-to-service delay, power-cycle the converter or click the button which appears on the
configuration HTTP screen of a converter that is in configuration delay.
LAN Auto-Disable
The LAN port can be configured to automatically disable itself when no telecom link exists. This setting is
useful for attached LAN equipment which requires the LAN port to go down in order to understand that the
path to the remote network is no longer available. Use this setting cautiously, as management of the
converter will also no longer be possible through a disabled LAN port.
To exit the LAN-port-disabled condition, power-cycle the converter, which will allow communication with
the converter for approximately one minute even if telecom ports are down.
Chapter 6: Interoperability
LAN
The LAN ports of the converter support, at a minimum, all 100BaseTX Full-Duplex Ethernet connections
up to maximum line lengths and are set to auto-MDI/MDIX to automatically detect/correct crossover vs
straight LAN cable and auto-negotiate full-duplex and pause frame modes with the attached LAN
equipment.
The converter will pass all un-errored packets which do not exceed 1650 bytes in packet length (9600 with
jumbo frames enabled). This length allows QinQ, stacked VLAN, and extended packet-length router
protocols to be passed without concern. The management agent accepts and responds with packets having
MTU of 1350 bytes in order to automatically allow room for security protocol overheads.
Autonegotiation problems
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.
SFP LAN Port 1
This port is designed to be compatible with inexpensive, high-quality, copper or fiber-optic, SFP
transceivers from Finisar, which allows LAN connections of 10km or more. Most other industry-standard
SFP transceivers will work as well; however, fiber-optic features such as temperature and optical
transmit/receive power and alarms will only be available if using Finisar transceivers. Non-Finisar copper,
RJ45 SFP transceivers may only operate in 1000Base-T mode, while recommended transceivers from
Finisar, and possibly Avago or 3Com will operate in 100Base-TX mode as well.
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